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Jubran A. Setting positive end-expiratory pressure in the severely obstructive patient. Curr Opin Crit Care 2024; 30:89-96. [PMID: 38085854 PMCID: PMC11141232 DOI: 10.1097/mcc.0000000000001131] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2024]
Abstract
PURPOSE OF REVIEW The response to positive end-expiratory pressure (PEEP) in patients with chronic obstructive pulmonary disease (COPD) requiring mechanical ventilation depends on the underlying pathophysiology. This review focuses on the pathophysiology of COPD, especially intrinsic PEEP (PEEPi) and its consequences, and the benefits of applying external PEEP during assisted ventilation when PEEPi is present. RECENT FINDINGS The presence of expiratory airflow limitation and increased airway resistance promotes the development of dynamic hyperinflation in patients with COPD during acute respiratory failure. Dynamic hyperinflation and the associated development of PEEPi increases work of breathing and contributes to ineffective triggering of the ventilator. In the presence of airflow limitation, application of external PEEP during patient-triggered ventilation has been shown to reduce inspiratory effort, facilitate ventilatory triggering and enhance patient-ventilator interaction. To minimize the risk of hyperinflation, it is advisable to limit the level of external PEEP during assisted ventilation after optimization of ventilator settings to about 70% of the level of PEEPi (measured during passive ventilation). SUMMARY In patients with COPD and dynamic hyperinflation receiving assisted mechanical ventilation, the application of low levels of external PEEP can minimize work of breathing, facilitate ventilator triggering and improve patient-ventilator interaction.
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Affiliation(s)
- Amal Jubran
- Division of Pulmonary and Critical Care Medicine, Edward Hines Jr. Veterans Affairs Hospital, Hines, Illinois
- Loyola University of Chicago Stritch School of Medicine, Maywood, Illinois, USA
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Acicbe Ö, Özgür CY, Rahimi P, Canan E, Aşar S, Çukurova Z. The effect of inspiratory rise time on mechanical power calculations in pressure control ventilation: dynamic approach. Intensive Care Med Exp 2023; 11:98. [PMID: 38117345 PMCID: PMC10733269 DOI: 10.1186/s40635-023-00584-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2023] [Accepted: 12/14/2023] [Indexed: 12/21/2023] Open
Abstract
BACKGROUND Mechanical power may serve as a valuable parameter for predicting ventilation-induced injury in mechanically ventilated patients. Over time, several equations have been developed to calculate power in both volume control ventilation (VCV) and pressure control ventilation (PCV). Among these equations, the linear model mechanical power equation (MPLM) closely approximates the reference method when applied in PCV. The dynamic mechanical power equation (MPdyn) computes power by utilizing the ventilatory work of breathing parameter (WOBv), which is automatically measured by the mechanical ventilator. In our study, conducted in patients with Covid-19 Acute Respiratory Distress Syndrome (C-ARDS), we calculated mechanical power using both the MPLM and MPdyn equations, employing different inspiratory rise times (Tslope) at intervals of 5%, ranging from 5 to 20% and compared the obtained results. RESULTS In our analysis, we used univariate linear regression at both I:E ratios of 1:2 and 1:1, considering all Tslope values. These analyses revealed that the MPdyn and MPLM equations exhibited strong correlations, with R2 values exceeding 0.96. Furthermore, our Bland-Altman analysis, which compared the power values derived from the MPdyn and MPLM equations for patient averages and all measurements, revealed a mean difference of -0.42 ± 0.41 J/min (equivalent to 2.6% ± 2.3%, p < 0.0001) and -0.39 ± 0.57 J/min (equivalent to 3.6% ± 3.5%, p < 0.0001), respectively. While there was a statistically significant difference between the equations in both absolute value and relative proportion, this difference was not considered clinically relevant. Additionally, we observed that each 5% increase in Tslope time corresponded to a decrease in mechanical power values by approximately 1 J/min. CONCLUSIONS The differences between mechanical power values calculated using the MPdyn and MPLM equations at various Tslope durations were determined to lack clinical significance. Consequently, for practical and continuous mechanical power estimation in Pressure-Controlled Ventilation (PCV) mode, the MPdyn equation presents itself as a viable option. It is important to note that as Tslope times increased, the calculated mechanical power exhibited a clinically relevant decrease.
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Affiliation(s)
- Özlem Acicbe
- Department of Anesthesiology and Reanimation, Şişli Hamidiye Etfal Training and Research Hospital, University of Health Sciences, Istanbul, Turkey
| | - Canan Yazıcı Özgür
- Department of Anesthesiology and Reanimation, Bakırköy Dr. Sadi Konuk Training and Research Hospital, University of Health Sciences, Istanbul, Turkey
| | - Payam Rahimi
- Department of Anesthesiology and Reanimation, Bakırköy Dr. Sadi Konuk Training and Research Hospital, University of Health Sciences, Istanbul, Turkey
| | - Emral Canan
- Department of Anesthesiology and Reanimation, Bakırköy Dr. Sadi Konuk Training and Research Hospital, University of Health Sciences, Istanbul, Turkey
| | - Sinan Aşar
- Department of Anesthesiology and Reanimation, Bakırköy Dr. Sadi Konuk Training and Research Hospital, University of Health Sciences, Istanbul, Turkey.
| | - Zafer Çukurova
- Department of Anesthesiology and Reanimation, Bakırköy Dr. Sadi Konuk Training and Research Hospital, University of Health Sciences, Istanbul, Turkey
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Wang JJ, Zhou Z, Zhang LY. Clinical evaluation of ventilation mode on acute exacerbation of chronic obstructive pulmonary disease with respiratory failure. World J Clin Cases 2023; 11:6040-6050. [PMID: 37731551 PMCID: PMC10507537 DOI: 10.12998/wjcc.v11.i26.6040] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/30/2023] [Revised: 07/19/2023] [Accepted: 08/18/2023] [Indexed: 09/08/2023] Open
Abstract
BACKGROUND At present, understanding of the most effective ventilation methods for treating chronic obstructive pulmonary disease (COPD) patients experiencing acute worsening symptoms and respiratory failure remains relatively limited. This report analyzed the efficiency and side effects of various ventilation techniques used for individuals experiencing an acute COPD exacerbation. AIM To determine whether pressure-controlled ventilation (PCV) can lower peak airway pressures (PAPs) and reduce the incidence of barotrauma compared to volume-controlled ventilation (VCV), without compromising clinical outcomes and oxygenation parameters. METHODS We have evaluated 600 patients who were hospitalized due to a severe COPD exacerbation, with 400 receiving mechanical ventilation for the respiratory failure. The participants were divided into two different groups, who were administered either VCV or PCV, along with appropriate management. We thereafter observed patients' attributes, clinical factors, and laboratory, radiographic, and arterial blood gas evaluations at the start and during their stay in the intensive care unit (ICU). We have also employed appropriate statistical methods for the data analysis. RESULTS Both the VCV and PCV groups experienced significant enhancements in the respiratory rate, tidal volume, and arterial blood gas values during their time in the ICU. However, no significant distinctions were detected between the groups in terms of oxygenation indices (partial pressures of oxygen/raction of inspired oxygen ratio) and partial pressures of carbon dioxide improvements. There was no considerable disparity observed between the VCV and PCV groups in the hospital mortality (32% vs 28%, P = 0.53), the number of days of ICU stay [median interquartile range (IQR): 9 (6-14) d vs 8 (5-13) d, P = 0.41], or the duration of the mechanical ventilation [median (IQR): 6 (4-10) d vs 5 (3-9) d, P = 0.47]. The PCV group displayed lower PAPs compared to the VCV group (P < 0.05) from the beginning of mechanical ventilation until extubation or ICU departure. The occurrence of barotrauma was considerably lower in the PCV group in comparison to the VCV group (6% vs 16%, P = 0.03). CONCLUSION Both VCV and PCV were found to be effective in treating patients with acute COPD exacerbation. However, PCV was associated with lower PAPs and a significant decrease in barotrauma, thus indicating that it might be a safer ventilation method for this group of patients. However, further large-scale study is necessary to confirm these findings and to identify the best ventilation approach for patients experiencing an acute COPD exacerbation.
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Affiliation(s)
- Jun-Jun Wang
- Department of Respiratory and Critical Care Medicine, The First People's Hospital of Yangquan City, Yangquan 045000, Shanxi Province, China
| | - Zhong Zhou
- Department of Respiratory and Critical Care Medicine, Guiyang Public Health Treatment Center, Guiyang 550001, Guizhou Province, China
| | - Li-Ying Zhang
- Department of Respiratory and Critical Care Medicine, The Ninth People's Hospital Affiliated to Shanghai Jiao Tong University School of Medicine, Shanghai 200023, China
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Gutierrez G. A novel method to calculate compliance and airway resistance in ventilated patients. Intensive Care Med Exp 2022; 10:55. [PMID: 36581716 PMCID: PMC9800666 DOI: 10.1186/s40635-022-00483-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2022] [Accepted: 12/17/2022] [Indexed: 12/31/2022] Open
Abstract
BACKGROUND The respiratory system's static compliance (Crs) and airway resistance (Rrs) are measured during an end-inspiratory hold on volume-controlled ventilation (static method). A numerical algorithm is presented to calculate Crs and Rrs during volume-controlled ventilation on a breath-by-breath basis not requiring an end-inspiratory hold (dynamic method). METHODS The dynamic method combines a numerical solution of the equation of motion of the respiratory system with frequency analysis of airway signals. The method was validated experimentally with a one-liter test lung using 300 mL and 400 mL tidal volumes. It also was validated clinically using airway signals sampled at 32.25 Hz stored in a historical database as 131.1-s-long epochs. There were 15 patients in the database having epochs on volume-controlled ventilation with breaths displaying end-inspiratory holds. This allowed for the reliable calculation of paired Crs and Rrs values using both static and dynamic methods. Epoch mean values for Crs and Rrs were assessed by both methods and compared in aggregate form and individually for each patient in the study with Pearson's R2 and Bland-Altman analysis. Figures are shown as median[IQR]. RESULTS Experimental method differences in 880 simulated breaths were 0.3[0.2,0.4] mL·cmH2O-1 for Crs and 0[- 0.2,0.2] cmH2O·s· L-1 for Rrs. Clinical testing included 78,371 breaths found in 3174 epochs meeting criteria with 24[21,30] breaths per epoch. For the aggregate data, Pearson's R2 were 0.99 and 0.94 for Crs and Rrs, respectively. Bias ± 95% limits of agreement (LOA) were 0.2 ± 1.6 mL·cmH2O-1 for Crs and - 0.2 ± 1.5 cmH2O·s· L-1 for Rrs. Bias ± LOA median values for individual patients were 0.6[- 0.2, 1.4] ± 0.9[0.8, 1.2] mL·cmH2O-1 for Crs and - 0.1[- 0.3, 0.2] ± 0.8[0.5, 1.2] cmH2O·s· L-1 for Rrs. DISCUSSION Experimental and clinical testing produced equivalent paired measurements of Crs and Rrs by the dynamic and static methods under the conditions tested. CONCLUSIONS These findings support to the possibility of using the dynamic method in continuously monitoring respiratory system mechanics in patients on ventilatory support with volume-controlled ventilation.
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Affiliation(s)
- Guillermo Gutierrez
- grid.253615.60000 0004 1936 9510Professor Emeritus Medicine, Anesthesiology and Engineering, The George Washington University, 700 New Hampshire Ave, NW, Suite 510, Washington, DC 20037 USA
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A model of the pulmonary acinar circulatory system with gas exchange function to explore the influence of alveolar diameter. Respir Physiol Neurobiol 2022; 300:103883. [PMID: 35247623 DOI: 10.1016/j.resp.2022.103883] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2021] [Revised: 02/27/2022] [Accepted: 02/27/2022] [Indexed: 11/20/2022]
Abstract
Lung diseases such as acute respiratory distress syndrome affect the patient's lung compliance, which in turn affects the ability of gas exchange. Changes in alveolar diameter relate to local lung compliance. How alveolar diameter affects gas exchange, particularly oxygen concentrations in alveolar capillaries, is a topic of concern for researchers, and can be studied using mathematical models. The level of small-scale mathematical models of the pulmonary circulatory system was the alveolar capillaries, but existing models do not consider the gas-exchange function and fail to reflect the influence of alveolar diameter. Therefore, we proposed a pulmonary acinar capillary model with gas exchange function, and most importantly, introduced alveolar diameter into the model, to analyze the effect of alveolar diameter on the gas exchange function of the pulmonary acini. The model was tested by three respiratory function simulation experiments. According to the simulation results of changing diameter, we found that the alveolar diameter mainly affects the alveolar gas exchange function of lung acinar inlets and the middle section compared with the peripheral section.
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Pinkham MI, Domanski U, Franke KJ, Hartmann J, Schroeder M, Williams T, Nilius G, Tatkov S. Effect of respiratory rate and size of cannula on pressure and dead-space clearance during nasal high flow in patients with COPD and acute respiratory failure. J Appl Physiol (1985) 2022; 132:553-563. [PMID: 35085029 PMCID: PMC8836745 DOI: 10.1152/japplphysiol.00769.2021] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Nasal high flow (NHF) is an efficient oxygenation tool for the treatment of respiratory failure. The study investigated the effect of breathing pattern on positive airway pressure and dead-space clearance by NHF. The breathing cycle during NHF was characterized in 26 patients with acute respiratory failure (ARF) and stable COPD and after mechanical ventilation (post-MV) via tracheostomy where also pressure was measured in the trachea. Dead-space clearance was measured in airway models during different breathing patterns. NHF reduced the respiratory rate (RR) and TI/TE through prolonging the TE; the TI/TE ranged between ≤0.5 observed in the COPD patients and ∼1.0 in the ARF patients. NHF via a standard medium-sized cannula interface generated a low-level expiratory pressure proportional to NHF rate and breathing flow; the median generated positive end-expiratory pressure was only 1.71 cmH2O at NHF 45 L/min. The dilution and purging of expired gas from a nasal cavity model were observed to occur at the end of expiration as expiratory flow slowed and the dynamic pressure decreased. The higher RR with shorter end-expiratory period resulted in reduced dead-space clearance by NHF; 20 L/min cleared 43 ± 2 mL at RR 15 min−1 vs. 9 ± 5 mL at RR 45 min−1, P < 0.001, which was increased at higher NHF rate. At lower RR, the clearance was similar between NHF rates 20 and 60 L/min. Higher NHF rates elevate positive airway pressure, and at the increased RR can improve the clearance. This may enhance gas exchange and lead to a reduction in the work of breathing. NEW & NOTEWORTHY During nasal high flow (NHF) an increased breathing frequency, which is commonly observed in acute respiratory failure, can lead to decreased dead-space clearance. Higher NHF rates increase the clearance and reduce the rebreathing which may eventually lower the respiratory rate and the work of breathing. Monitoring of the respiratory rate could be an important indicator of not only the respiratory function but also the NHF rate selection and the therapy efficacy.
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Affiliation(s)
| | | | - Karl-Josef Franke
- Märkische Kliniken GmbH, Lüdenscheid, Germany
- Universität Witten/Herdecke, Witten, Germany
| | | | | | | | - Georg Nilius
- Evang. Kliniken Essen-Mitte GmbH, Essen, Germany
- Universität Witten/Herdecke, Witten, Germany
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Marinakis G, Paraschos M, Patrani M, Tsoutsouras T, Vassiliou M. Non-interventional monitoring of expiratory flow limitation during experimental mechanical ventilation. ERJ Open Res 2021; 7:00264-2020. [PMID: 33532479 PMCID: PMC7836650 DOI: 10.1183/23120541.00264-2020] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2020] [Accepted: 09/25/2020] [Indexed: 11/17/2022] Open
Abstract
Background Expiratory flow limitation (EFL) is common among patients in the intensive care unit under mechanical ventilation (MV) and may have significant clinical consequences. In the present study, we examine the possibility of non-interventional detection of EFL during experimental MV. Methods Eight artificially ventilated New Zealand rabbits were included in the experiments. EFL was induced during MV by application of negative expiratory pressure (−5, −8 and −10 hPa) and detected by the negative expiratory pressure technique. Airway pressure (Paw) and gas flow (V′) were digitally recorded and processed off-line for the evaluation of respiratory mechanics. The method is based on the computation and monitoring of instantaneous respiratory resistance Rrs(t). The resistive pressure (Paw,res(t)) is calculated by subtracting from Paw its elastic component and the end-expiratory pressure, as assessed by linear regression. Then, Rrs(t) is computed as the instant ratio Paw,res(t)/V′(t). Results Two completely different patterns of expiratory Rrs(t) separate the cases with EFL from those without EFL. Small and random fluctuations are noticed when EFL is absent, whereas the onset of EFL is accompanied by an abrupt and continuous rise in Rrs(t), towards the end of expiration. Thus, EFL is not only detected but may also be quantified from the volume still to be expired at the time EFL occurs. Conclusion The proposed technique is a simple, accurate and non-interventional tool for EFL monitoring during MV. Respiratory system resistance in expiratory flow limitation during mechanical ventilationhttps://bit.ly/34hU6Bv
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Affiliation(s)
- Giorgos Marinakis
- Dept of Critical Care Medicine, General Hospital of Athens, "Korgialenio - Benakio" Hellenic Red Cross, Athens, Greece
| | - Michael Paraschos
- Dept of Critical Care Medicine, General Hospital of Athens, "Korgialenio - Benakio" Hellenic Red Cross, Athens, Greece
| | - Maria Patrani
- Dept of Critical Care Medicine, General Hospital of Athens, "Korgialenio - Benakio" Hellenic Red Cross, Athens, Greece
| | - Theodoros Tsoutsouras
- Dept of Critical Care Medicine, General Hospital of Athens, "Korgialenio - Benakio" Hellenic Red Cross, Athens, Greece
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Haouzi P, Zamir A, Villarreal-Fernandez E, Stauffer D, Ventola L, Ahmad D, Dewaters A, Khalid M, Wojnar M. Mechanics of Breathing and Gas Exchange in Mechanically Ventilated Patients with COVID-19-associated Respiratory Failure. Am J Respir Crit Care Med 2020; 202:626-628. [PMID: 32579017 PMCID: PMC7427403 DOI: 10.1164/rccm.202004-1041le] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
Affiliation(s)
| | - Areeb Zamir
- Pennsylvania State UniversityState College, Pennsylvania
| | | | - Dana Stauffer
- Pennsylvania State UniversityState College, Pennsylvania
| | - Lauren Ventola
- Pennsylvania State UniversityState College, Pennsylvania
| | - Danish Ahmad
- Pennsylvania State UniversityState College, Pennsylvania
| | - Ami Dewaters
- Pennsylvania State UniversityState College, Pennsylvania
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9
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Giosa L, Busana M, Pasticci I, Bonifazi M, Macrì MM, Romitti F, Vassalli F, Chiumello D, Quintel M, Marini JJ, Gattinoni L. Mechanical power at a glance: a simple surrogate for volume-controlled ventilation. Intensive Care Med Exp 2019; 7:61. [PMID: 31773328 PMCID: PMC6879677 DOI: 10.1186/s40635-019-0276-8] [Citation(s) in RCA: 59] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2019] [Accepted: 10/16/2019] [Indexed: 11/24/2022] Open
Abstract
BACKGROUND Mechanical power is a summary variable including all the components which can possibly cause VILI (pressures, volume, flow, respiratory rate). Since the complexity of its mathematical computation is one of the major factors that delay its clinical use, we propose here a simple and easy to remember equation to estimate mechanical power under volume-controlled ventilation: [Formula: see text] where the mechanical power is expressed in Joules/minute, the minute ventilation (VE) in liters/minute, the inspiratory flow (F) in liters/minute, and peak pressure and positive end-expiratory pressure (PEEP) in centimeter of water. All the components of this equation are continuously displayed by any ventilator under volume-controlled ventilation without the need for clinician intervention. To test the accuracy of this new equation, we compared it with the reference formula of mechanical power that we proposed for volume-controlled ventilation in the past. The comparisons were made in a cohort of mechanically ventilated pigs (485 observations) and in a cohort of ICU patients (265 observations). RESULTS Both in pigs and in ICU patients, the correlation between our equation and the reference one was close to the identity. Indeed, the R2 ranged from 0.97 to 0.99 and the Bland-Altman showed small biases (ranging from + 0.35 to - 0.53 J/min) and proportional errors (ranging from + 0.02 to - 0.05). CONCLUSIONS Our new equation of mechanical power for volume-controlled ventilation represents a simple and accurate alternative to the more complex ones available to date. This equation does not need any clinical intervention on the ventilator (such as an inspiratory hold) and could be easily implemented in the software of any ventilator in volume-controlled mode. This would allow the clinician to have an estimation of mechanical power at a simple glance and thus increase the clinical consciousness of this variable which is still far from being used at the bedside. Our equation carries the same limitations of all other formulas of mechanical power, the most important of which, as far as it concerns VILI prevention, are the lack of normalization and its application to the whole respiratory system (including the chest wall) and not only to the lung parenchyma.
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Affiliation(s)
- Lorenzo Giosa
- Departement of Anesthesiology, Emergency and Intensive Care Medicine, University of Göttingen, Göttingen, Germany
| | - Mattia Busana
- Departement of Anesthesiology, Emergency and Intensive Care Medicine, University of Göttingen, Göttingen, Germany
| | - Iacopo Pasticci
- Departement of Anesthesiology, Emergency and Intensive Care Medicine, University of Göttingen, Göttingen, Germany
| | - Matteo Bonifazi
- Departement of Anesthesiology, Emergency and Intensive Care Medicine, University of Göttingen, Göttingen, Germany
| | - Matteo Maria Macrì
- Departement of Anesthesiology, Emergency and Intensive Care Medicine, University of Göttingen, Göttingen, Germany
| | - Federica Romitti
- Departement of Anesthesiology, Emergency and Intensive Care Medicine, University of Göttingen, Göttingen, Germany
| | - Francesco Vassalli
- Departement of Anesthesiology, Emergency and Intensive Care Medicine, University of Göttingen, Göttingen, Germany
| | - Davide Chiumello
- SC Anestesia e Rianimazione, Ospedale San Paolo - Polo Universitario, ASST Santi Paolo e Carlo, Milan, Italy
- Dipartimento di Scienze Biomediche per la Salute, Centro Ricerca Coordinato di Insufficienza Respiratoria, Università degli Studi di Milano, Milan, Italy
| | - Michael Quintel
- Departement of Anesthesiology, Emergency and Intensive Care Medicine, University of Göttingen, Göttingen, Germany
| | - J J Marini
- University of Minnesota and Regions Hospital, Minneapolis/St. Paul, MN, USA
| | - Luciano Gattinoni
- Departement of Anesthesiology, Emergency and Intensive Care Medicine, University of Göttingen, Göttingen, Germany.
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Mauri T, Lazzeri M, Bellani G, Zanella A, Grasselli G. Respiratory mechanics to understand ARDS and guide mechanical ventilation. Physiol Meas 2017; 38:R280-H303. [PMID: 28967868 DOI: 10.1088/1361-6579/aa9052] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
OBJECTIVE As precision medicine is becoming a standard of care in selecting tailored rather than average treatments, physiological measurements might represent the first step in applying personalized therapy in the intensive care unit (ICU). A systematic assessment of respiratory mechanics in patients with the acute respiratory distress syndrome (ARDS) could represent a step in this direction, for two main reasons. Approach and Main results: On the one hand, respiratory mechanics are a powerful physiological method to understand the severity of this syndrome in each single patient. Decreased respiratory system compliance, for example, is associated with low end expiratory lung volume and more severe lung injury. On the other hand, respiratory mechanics might guide protective mechanical ventilation settings. Improved gravitationally dependent regional lung compliance could support the selection of positive end-expiratory pressure and maximize alveolar recruitment. Moreover, the association between driving airway pressure and mortality in ARDS patients potentially underlines the importance of sizing tidal volume on respiratory system compliance rather than on predicted body weight. SIGNIFICANCE The present review article aims to describe the main alterations of respiratory mechanics in ARDS as a potent bedside tool to understand severity and guide mechanical ventilation settings, thus representing a readily available clinical resource for ICU physicians.
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Affiliation(s)
- Tommaso Mauri
- Department of Pathophysiology and Transplantation, University of Milan, Via Festa del Perdono 7, 20122 Milan, Italy. Department of Anesthesia, Critical Care and Emergency, Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico, Via F. Sforza 35, 20122 Milan, Italy
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Albanese A, Vicario F, Buizza R. End-inspiratory occlusion in the presence of intrinsic PEEP. ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL INTERNATIONAL CONFERENCE 2017; 2017:149-152. [PMID: 29059832 DOI: 10.1109/embc.2017.8036784] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Typical modern mechanical ventilators offer the clinician the possibility of automatically performing end-inspiratory occlusion maneuvers. The static conditions induced by such maneuvers are indeed favorable to estimating patient's respiratory mechanics in terms of total resistance (R) and elastance (E). These are parameters of wide clinical interest. However, in the presence of intrinsic PEEP, the standard formula used to compute E via the occlusion maneuver is known to be inaccurate. In this paper we propose an alternative method for the estimation of E via the occlusion maneuver that eliminates the bias by leveraging concepts derived from physiological modeling of the respiratory system dynamics. The proposed method is also capable of accounting for respiratory efforts triggering the breath, and hence can be applied in both passive and spontaneously breathing conditions.
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12
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Colombo J. Predictors of Outcomes After Pediatric Cardiac Surgery: A Proposal to Improve the Vasoactive-Ventilation-Renal Score. Ann Thorac Surg 2017; 102:1413. [PMID: 27645958 DOI: 10.1016/j.athoracsur.2016.02.109] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/18/2016] [Revised: 02/18/2016] [Accepted: 02/26/2016] [Indexed: 10/21/2022]
Affiliation(s)
- Jacopo Colombo
- Department of Pathophysiology and Transplantation, University of Milan, Via Festa del Perdono 3, 20100 Milan, Italy.
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15
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Typical patterns of expiratory flow and carbon dioxide in mechanically ventilated patients with spontaneous breathing. J Clin Monit Comput 2016; 31:773-781. [PMID: 27344663 DOI: 10.1007/s10877-016-9903-z] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2016] [Accepted: 06/20/2016] [Indexed: 10/21/2022]
Abstract
Incomplete expiration of tidal volume can lead to dynamic hyperinflation and auto-PEEP. Methods are available for assessing these, but are not appropriate for patients with respiratory muscle activity, as occurs in pressure support. Information may exist in expiratory flow and carbon dioxide measurements, which, when taken together, may help characterize dynamic hyperinflation. This paper postulates such patterns and investigates whether these can be seen systematically in data. Two variables are proposed summarizing the number of incomplete expirations quantified as a lack of return to zero flow in expiration (IncExp), and the end tidal CO2 variability (varETCO2), over 20 breaths. Using these variables, three patterns of ventilation are postulated: (a) few incomplete expirations (IncExp < 2) and small varETCO2; (b) a variable number of incomplete expirations (2 ≤ IncExp ≤ 18) and large varETCO2; and (c) a large number of incomplete expirations (IncExp > 18) and small varETCO2. IncExp and varETCO2 were calculated from data describing respiratory flow and CO2 signals in 11 patients mechanically ventilated at 5 levels of pressure support. Data analysis showed that the three patterns presented systematically in the data, with periods of IncExp < 2 or IncExp > 18 having significantly lower variability in end-tidal CO2 than periods with 2 ≤ IncExp ≤ 18 (p < 0.05). It was also shown that sudden change in IncExp from either IncExp < 2 or IncExp > 18 to 2 ≤ IncExp ≤ 18 results in significant, rapid, change in the variability of end-tidal CO2 p < 0.05. This study illustrates that systematic patterns of expiratory flow and end-tidal CO2 are present in patients in supported mechanical ventilation, and that changes between these patterns can be identified. Further studies are required to see if these patterns characterize dynamic hyperinflation. If so, then their combination may provide a useful addition to understanding the patient at the bedside.
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Monitoring of total positive end-expiratory pressure during mechanical ventilation by artificial neural networks. J Clin Monit Comput 2016; 31:551-559. [PMID: 27067075 DOI: 10.1007/s10877-016-9874-0] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2015] [Accepted: 04/05/2016] [Indexed: 12/17/2022]
Abstract
Ventilation treatment of acute lung injury (ALI) requires the application of positive airway pressure at the end of expiration (PEEPapp) to avoid lung collapse. However, the total pressure exerted on the alveolar walls (PEEPtot) is the sum of PEEPapp and intrinsic PEEP (PEEPi), a hidden component. To measure PEEPtot, ventilation must be discontinued with an end-expiratory hold maneuver (EEHM). We hypothesized that artificial neural networks (ANN) could estimate the PEEPtot from flow and pressure tracings during ongoing mechanical ventilation. Ten pigs were mechanically ventilated, and the time constant of their respiratory system (τRS) was measured. We shortened their expiratory time (TE) according to multiples of τRS, obtaining different respiratory patterns (Rpat). Pressure (PAW) and flow (V'AW) at the airway opening during ongoing mechanical ventilation were simultaneously recorded, with and without the addition of external resistance. The last breath of each Rpat included an EEHM, which was used to compute the reference PEEPtot. The entire protocol was repeated after the induction of ALI with i.v. injection of oleic acid, and 382 tracings were obtained. The ANN had to extract the PEEPtot, from the tracings without an EEHM. ANN agreement with reference PEEPtot was assessed with the Bland-Altman method. Bland Altman analysis of estimation error by ANN showed -0.40 ± 2.84 (expressed as bias ± precision) and ±5.58 as limits of agreement (data expressed as cmH2O). The ANNs estimated the PEEPtot well at different levels of PEEPapp under dynamic conditions, opening up new possibilities in monitoring PEEPi in critically ill patients who require ventilator treatment.
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Sulemanji DS, Marchese A, Wysocki M, Kacmarek RM. Adaptive support ventilation with and without end-tidal CO2 closed loop control versus conventional ventilation. Intensive Care Med 2012; 39:703-10. [PMID: 23151992 DOI: 10.1007/s00134-012-2742-6] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2011] [Accepted: 10/15/2012] [Indexed: 10/27/2022]
Abstract
PURPOSE Our aim was to compare adaptive support ventilation with and without closed loop control by end tidal CO2 (ASVCO2, ASV) with pressure (PC) and volume control ventilation (VC) during simulated clinical scenarios [normal lungs (N), COPD, ARDS, brain injury (BI)]. METHODS A lung model was used to simulate representative compliance (mL/cmH2O): resistance (cmH2O/L/s) combinations, 45:5 for N and BI, 60:7.7 for COPD, 15:7.7 and 35:7.7 for ARDS. Two levels of PEEP (cmH2O) were used for each scenario, 12/16 for ARDS, and 5/10 for others. The CO2 productions of 2, 3, 4 and 5 mL/kg predicted body weight/min were simulated. Tidal volume was set to 6 mL/kg during VC and PC. Outcomes of interest were end tidal CO2 (etCO2) and plateau pressure (P Plat). RESULTS EtCO2 levels in N and BI and COPD were similar for all modes. In ARDS, etCO2 was higher in ASVCO2 than in other modes (p < 0.001). Under all mechanical conditions ASVCO2 revealed a narrower range of etCO2. P Plat was similar for all modes in all scenarios but ARDS where P Plat in ASV and ASVCO2 were lower than in VC (p = 0.001). When P Plat was ≥ 28 cmH2O, P plat in ASV and ASVCO2 were lower than in VC and PC (p = 0.024). CONCLUSION All modes performed similarly in most cases. Minor differences observed were in favor of the closed loop modes. Overall, ASVCO2 maintained tighter CO2 control. The ASVCO2 had the greatest impact during ARDS allowing etCO2 to increase and protecting against hypocapnia evident with other modes while ensuring lower P plat and tidal volumes.
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Affiliation(s)
- Demet S Sulemanji
- Department of Anesthesia, Critical Care and Pain Medicine, Harvard Medical School and Massachusetts General Hospital, Boston, MA, USA.
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Nassar BS, Collett ND, Schmidt GA. The flow-time waveform predicts respiratory system resistance and compliance. J Crit Care 2012; 27:418.e7-14. [PMID: 22226421 DOI: 10.1016/j.jcrc.2011.10.012] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2011] [Revised: 09/28/2011] [Accepted: 10/31/2011] [Indexed: 02/09/2023]
Abstract
PURPOSE Knowledge of patients' lung compliance and resistance aids clinical management. We investigated whether these values, readily measured during volume assist-control ventilation (VACV), could also be estimated during pressure assist-control ventilation (PACV). METHODS Data were collected in 12 mechanically ventilated human subjects. During VACV, peak pressure, plateau pressure, end-expiratory pressure, tidal volume, and inspiratory flow rate were measured. During PACV, inspiratory pressure, end-expiratory pressure, and tidal volume were recorded. The linear component of the pressure-time waveform was extrapolated to time and flow axes. Using the equation of motion for the respiratory system, assuming a nonlinear resistance, we calculated inspiratory resistance and compliance. During VACV, compliance and inspiratory resistance were calculated in the conventional manner. RESULTS In ventilated subjects, mean compliance during PACV was 37.06 ± 15.65 mL/cm H(2)O, and during VACV, 36.93 ± 12.18 mL/cm H(2)O. Mean inspiratory resistance during PACV was 15.17 ± 5.14 cm H(2)O/L per second, whereas during VACV, it was 12.50 ± 2.99 cm H(2)O/L per second. A strong correlation is evident between compliance and inspiratory resistance calculated during PACV vs VACV (r(2) of 0.73 and 0.51, respectively). CONCLUSIONS During PACV, the inspiratory flow waveform is linear, and its slope contains information regarding inspiratory resistance and compliance. Calculated values correlate with those during VACV.
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Affiliation(s)
- Boulos S Nassar
- Division of Pulmonary, Critical Care, and Occupational Medicine, Department of Internal Medicine, University of Iowa Carver College of Medicine, Iowa City, IA 52242, USA.
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Seymour CW, Frazer M, Reilly PM, Fuchs BD. Airway pressure release and biphasic intermittent positive airway pressure ventilation: are they ready for prime time? ACTA ACUST UNITED AC 2007; 62:1298-308; discussion 1308-9. [PMID: 17495742 DOI: 10.1097/ta.0b013e31803c562f] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Airway pressure release ventilation and biphasic positive airway pressure ventilation are being used increasingly as alternative strategies to conventional assist control ventilation for patients with acute respiratory distress syndrome (ARDS) and acute lung injury. By permitting spontaneous breathing throughout the ventilatory cycle, these modes offer several advantages over conventional strategies to improve the pathophysiology in these patients, including gas exchange, cardiovascular function, and reducing or eliminating the need for heavy sedation and paralysis. Whether these surrogate outcomes will translate into better patient outcomes remains to be determined. The purpose of this review is to summarize the rationale behind the use of these ventilatory strategies in ARDS, the clinical experience with the use of these modes, and their future applications in trauma patients.
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Affiliation(s)
- Christopher W Seymour
- Department of Surgery, Hospital of the University of Pennsylvania, Philadelphia 19104-4283, USA
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Brighenti C, Gnudi G, Barbini P, Avanzolini G. Estimation of expiratory resistance: a simulation study. ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL INTERNATIONAL CONFERENCE 2007; 2007:4247-4250. [PMID: 18002940 DOI: 10.1109/iembs.2007.4353274] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
It is of particular importance to detect and quantify obstructive pathological conditions in mechanically ventilated patients, especially in the presence of expiratory flow limitation (EFL), in order to help the clinicians in the choice of the most appropriate ventilation and pharmacological strategies. Aim of this work is to test by simulation a non invasive procedure for estimating the total apparent expiratory resistance of the respiratory system (Rtae). The proposed procedure is based on a time-varying two-element viscoelastic model characterized by the variable resistance Rtae and by a constant compliance estimated by the end-inspiratory occlusion technique. A non linear, dynamic, morphometric model of respiratory mechanics, based on Weibel's representation of the tracheobronchial tree, was used to simulate normal and obstructive respiratory conditions, leading to EFL, during artificial ventilation. The proposed resistance was computed in all simulated cases when the 50% and the 75% of tidal volume has been exhaled during a normal expiration. Rtae appeared to be dependent on the degree of airway obstruction and could provide useful information on how the airway compression varies during expiration.
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Affiliation(s)
- Chiara Brighenti
- Department of Electronics, Computer Science and Systems, University of Bologna, 40136 Bologna, Italy.
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21
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Barbini P, Brighenti C, Gnudi G. A Simulation Study of Expiratory Flow Limitation in Obstructive Patients during Mechanical Ventilation. Ann Biomed Eng 2006; 34:1879-89. [PMID: 17061156 DOI: 10.1007/s10439-006-9213-6] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2006] [Accepted: 09/27/2006] [Indexed: 11/24/2022]
Abstract
Although normal lungs may be represented satisfactorily by symmetrical architecture, pathological conditions generally require accounting for asymmetrical branching of the bronchial tree, since lung heterogeneity may be significant in respiratory diseases. In the present study, a recently proposed symmetrical dynamic morphometric model of the human lung, based on Weibel's regular dichotomy, was adapted to simulate different physiopathological scenarios of lung heterogeneity. The asymmetrical architecture was mimicked by modeling different conductive airway compartments below the main bronchi, each compartment being characterized by regular branching. The respiratory zone and chest wall were described by a Voigt body and a constant elastance, respectively. Simulation results allowed us to investigate the influence of the main mechanisms involved in expiratory flow limitation and dynamic hyperinflation in mechanically ventilated COPD patients. In brief, they showed that convective gas acceleration plays a key role in reproducing a negative relationship between driving pressure and expiratory flow. Moreover, reduced lung elastance due to emphysema resulted in a remarkable increase in dynamic hyperinflation, although it did not significantly modify expiratory flow limitation. Finally, the presence of a normal lung compartment masked pathological behaviors, preventing standard techniques from revealing expiratory flow limitation in affected compartments.
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Affiliation(s)
- Paolo Barbini
- Dipartimento di Chirurgia e Bioingegneria, Università di Siena, Viale Bracci 2, 53100, Siena, Italy.
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Tobin M, Brochard L, Rossi A. Exploration de la fonction des muscles respiratoires en réanimation. Rev Mal Respir 2004. [DOI: 10.1016/s0761-8425(04)71403-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
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23
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Ruiz ferrón F, Rucabado aguilar L, Poala gallego M, Muñoz muñoz J, Brea salvago J, La rosa salas F, Morante valle A. Cambios en la auto-PEEP durante la ventilación mecánica relacionados con la frecuencia respiratoria según el análisis de la constante de tiempo. Med Intensiva 2004. [DOI: 10.1016/s0210-5691(04)70044-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
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Vassiliou MP, Amygdalou A, Psarakis CJ, Dalavanga Y, Vassiliou PM, Mandragos KE, Constantopoulos SH, Behrakis PK. Volume and flow dependence of respiratory mechanics in mechanically ventilated COPD patients. Respir Physiol Neurobiol 2003; 135:87-96. [PMID: 12706068 DOI: 10.1016/s1569-9048(03)00064-8] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Volume and flow dependencies of respiratory mechanics are examined in 10 COPD patients under mechanical ventilation (MV) at 3 levels of externally applied PEEP (PEEPe). Airways pressure (Paw), flow (V') and volume (V) data are analyzed according to (1) the linear and (2) a non-linear model, accounting for volume dependence of elastance and for flow and volume dependence of resistance. The models' fitness to data is assessed by the regression errors. Non-linear modelling fits significantly better to data, while the difference of fitness decreases with PEEPe. Linear mechanics are not significantly different between the 3 levels of PEEPe. A positive volume dependence of elastance observed at 0, decreases at 5 and increases again at 10 hPa of PEEPe. A seriously negative volume dependence of resistance at 0 turned to positive with PEEPe. These dependencies of respiratory mechanics during COPD under MV, show that the present non-linear respiratory mechanical monitoring may help for better and less risky adjustment of PEEPe.
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Affiliation(s)
- Miltos P Vassiliou
- The Pneumonology Department, Medical School, University of Ioannina, Ioannina, Greece.
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Mygdalou A, Psarakis C, Vassiliou P, Dalavanga YA, Mandragos C, Constantopoulos SH, Behrakis PK, Vassiliou MP, Amygdalou A. Evaluation of the end-expiratory pressure by multiple linear regression and Fourier analysis in humans. Respir Med 2002; 96:499-505. [PMID: 12194633 DOI: 10.1053/rmed.2002.1305] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
This study was designed to compare the end-expiratory pressure (EEP) during mechanical ventilation (MV) measured dynamically (EEPdyn), by multiple linear regression (MLR) of the airway pressure (Pao) vs volume (V) and flow (V') and after Fourier analysis (FA) of the Pao and V'. Pao and V' were recorded from 32 ICU patients (II without respiratory disease, 10 COPD, II ARDS) under MV, at three levels of PEEPe (0, 5 and 10 hPa). Volume was calculated by numerical integration of V'. Data were analysed by MLR and FA, while the actual value of EEPdyn was recognised on the Pao signal at zero V' and V. EEPdyn, EEPMLR and EEPFA were compared for all patients, for each group of patients and for every level of applied PEEPe. Despite the different evaluation of respiratory mechanics between MLR and FA, the EEP values were always not significantly different between the three applied methods (P > 0.05). A high degree of correlation was found between them, taken two at a time (r > 0.99, P < 0.001). Two non-invasive analytical methods for the evaluation of respiratory mechanics during MV, MLR and FA offer a reliable and clinically useful estimation of EEP during MV.
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Affiliation(s)
- A Mygdalou
- Department of Experimental Physiology, School of Medicine, University of Athens, 75 Mikras Asias Street, Goudi, 11527 Athens, Greece
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Wang SH, Wei TS. The outcome of early pressure-controlled inverse ratio ventilation on patients with severe acute respiratory distress syndrome in surgical intensive care unit. Am J Surg 2002; 183:151-5. [PMID: 11918879 DOI: 10.1016/s0002-9610(01)00870-4] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
BACKGROUND Pressure-controlled inverse ratio ventilation (PC-IRV) was used in patients with acute respiratory distress syndrome (ARDS) after failed volume-cycled conventional ratio ventilation (VC-CRV). The aim of this study was to evaluate the outcome of early PC-IRV in severe ARDS. METHODS Twenty patients with severe ARDS were switched from VC-CRV to PC-IRV if they failed to maintain SaO(2) >90% by the following criteria: peak inspiratory pressure (PIP) >35 cm H(2)O, FIO(2) = 60%, and positive end-expiratory pressure (PEEP) 10 cm H(2)O. RESULTS The values of PIP, mean airway pressure, minute volumes, and lung injury score in VC-CRV were 43.9 +/- 8.0 cm H(2)O, 19.5 +/- 6.4 cm H(2)O, 11.0 +/- 2.1 L/min, and 2.8 +/- 0.2 respectively. In PC-IRV, the corresponding data were 31.8 +/- 5.1 cm H(2)O, 25.4 +/- 4.6 cm H(2)O, 8.3 +/- 0.9 L/min, and 2.5 +/- 0.4. All of these parameters were significantly different. Fifteen patients (75%) survived their intensive care unit stay. CONCLUSIONS Early PC-IRV in severe ARDS improves oxygenation, facilitates tapering of high fraction of inspiratory oxygen, and decreases high PEEP or PIP, and then results in the improvement of the patient's outcome.
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Affiliation(s)
- Shu-Hui Wang
- Critical Care Division, Surgical Department, Changhua Christian Hospital, Taiwan.
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Riou Y, Leclerc F, Scalfaro P, Abazine A, Neve V, Storme L. Effect of increasing inspiratory time on respiratory mechanics in mechanically ventilated neonates. Pediatr Crit Care Med 2002; 3:45-51. [PMID: 12793922 DOI: 10.1097/00130478-200201000-00011] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
OBJECTIVE To investigate the effect of inspiratory time and inspiratory flow on the respiratory mechanics of intubated and ventilated neonates. DESIGN Physiology study. SETTING Tertiary university neonatal intensive care unit. PATIENTS Neonates requiring mechanical ventilation with (group 1, n = 9) and without lung disease (group 2, n = 6). INTERVENTIONS All infants were ventilated with a Servo 900C Siemens ventilator in the volume-controlled constant-flow mode. Flow and pressure were measured at the Y-piece, while different inspiratory times (25%, 33%, 50%, and 67% of the respiratory cycle) were applied randomly without changing tidal volume. MEASUREMENTS The constant flow end-inspiratory airway occlusion technique allowed partitioning of the total respiratory system resistance (R(tot,rs)) into a standard intrinsic flow resistance (R(int,rs)) and a lung/thorax tissue viscoelastic component (DeltaR(rs)), and it allowed partitioning of the dynamic respiratory system elastance (E(dyn,rs)) into a static (E(st,rs)) and a lung/thorax tissue viscoelastic component (DeltaE(rs)). A two-compartment model of the respiratory system was applied to the experimental data. MAIN RESULTS All respiratory mechanics components were significantly higher in group 1 compared with group 2. Both groups showed increasing R(int,rs) with increasing flow and increasing DeltaR(rs) with increasing inspiratory time. DeltaR(rs) represented 40% to 75% of R(tot,rs) whatever the group. E(dyn,rs) and E(st,rs) changed with inspiratory time in the very low (<0.4 secs) and the very long inspiratory time range (>1.0 secs). No change was found when clinically, commonly used inspiratory times were applied (0.4-1.0 secs). DeltaE(rs) represented 17% to 19% of E(dyn,rs). The relationship between DeltaR(rs) and increasing inspiratory time fitted the exponential two-compartment model (r =.99, p <.001). CONCLUSIONS Total respiratory mechanics and its components in ventilated newborns with and without lung disease showed inspiratory time dependence. DeltaR(rs) increased with increasing inspiratory time as predicted by the two-compartment lung model, whereas standard R(int,rs) and E(dyn,rs) decreased.
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Affiliation(s)
- Yvon Riou
- Department of Respiratory Physiology, Hôpital Jeanne de Flandre, Chru de Lille, France
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Abstract
The management of some problematic patients having thoracic surgery is among the most difficult challenges for the anesthesiologist. Increasingly complex operations are performed on seriously compromised patients because of the development of new surgical techniques and the anesthesiologists' awareness of surgical needs and requirements to provide a satisfactory and safe surgical field. In order to facilitate thoracic surgery, the single most important and valuable anesthetic technique used actually is one-lung ventilation. This article reviews the complex pathopysiology of one-lung ventilation.
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Affiliation(s)
- L L Szegedi
- Department of Anesthesiology, Division of Thoracic and Cardiovascular Anesthesia, Erasme University Hospital, Brussels, Belgium.
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Barbini P, Cevenini G, Bernardi F, Massai MR, Gnudi G, Avanzolini G. Effect of compliant intermediate airways on total respiratory resistance and elastance in mechanical ventilation. Med Eng Phys 2001; 23:185-94. [PMID: 11410383 DOI: 10.1016/s1350-4533(01)00039-x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Total respiratory resistance and elastance were estimated off-line in a sample of 60 patients undergoing mechanical ventilation by means of two regression models in order to analyse and understand a possible physiological mechanism determining differences in inspiration and expiration. The first model considered a single value for resistance and elastance over a whole breathing cycle, whereas the second model considered separate values for inspiratory and expiratory resistance and a single value for elastance. Inspiratory resistance was found to be lower than expiratory resistance, and intermediate values were obtained for resistance estimated over the whole breathing cycle. Student's t-test showed a highly significant difference between these resistance estimates, and principal components analysis demonstrated a significant increase in information when both inspiratory and expiratory resistances were used. Minor differences were found between values of elastance calculated with the two approaches. In an attempt to interpret these experimental results, a lung model incorporating the non-linear viscoelastic properties of the intermediate airways was considered. This model suggested that changes in intermediate airway volume play a significant role in breathing mechanics during artificial ventilation and indicated that inspiratory and expiratory resistance could be useful parameters for locating airway obstruction.
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Affiliation(s)
- P Barbini
- Istituto di Chirurgia Toracica e Cardiovascolare e Tecnologie Biomediche, Università di Siena, I-53100, Siena, Italy.
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Mols G, Kessler V, Benzing A, Lichtwarck-Aschoff M, Geiger K, Guttmann J. Is pulmonary resistance constant, within the range of tidal volume ventilation, in patients with ARDS? Br J Anaesth 2001; 86:176-82. [PMID: 11573656 PMCID: PMC8543332 DOI: 10.1093/bja/86.2.176] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
When managing patients with acute respiratory distress syndrome (ARDS), respiratory system compliance is usually considered first and changes in resistance, although recognized, are neglected. Resistance can change considerably between minimum and maximum lung volume, but is generally assumed to be constant in the tidal volume range (V(T)). We measured resistance during tidal ventilation in 16 patients with ARDS or acute lung injury by the slice method and multiple linear regression analysis. Resistance was constant within V(T) in only six of 16 patients. In the remaining patients, resistance decreased, increased or showed complex changes. We conclude that resistance within V(T) varies considerably from patient to patient and that constant resistance within V(T) is not always likely.
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Affiliation(s)
- G Mols
- Department of Anaesthesiology and Critical Care Medicine, University of Freiburg, Germany
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Abstract
Exacerbations of COPD are a leading indication for MV in the intensive care unit. A thorough understanding of the pathophysiology of AVF in COPD is critical for physicians caring for these patients. In particular, physicians should understand DHI and use the ventilator and ancillary techniques to minimize its impact. Noninvasive positive-pressure ventilation should be considered strongly in relatively stable patients with an adequate mental status and manageable secretions. Once AVF resolves, patients should be removed from the ventilator as soon as is safe to do so to minimize the adverse effects of prolonged MV. An organized approach to weaning and identifying patients capable of independent breathing is crucial. Most patients with COPD and AVF benefit from MV and generally return to or approach their premorbid functional status. A significant subset, however, will not benefit from, or choose not to undergo, MV. Deciding upon appropriate therapeutic options for these patients relies heavily on effective communication between physician and patient. Comprehensive discussions before the development of AVF can assist decision-making after respiratory failure develops.
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Affiliation(s)
- J M Sethi
- Department of Medicine, Section of Pulmonary and Critical Care, Yale University School of Medicine, New Haven, Connecticut 06520, USA
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Tassaux D, Jolliet P, Roeseler J, Chevrolet JC. Effects of helium-oxygen on intrinsic positive end-expiratory pressure in intubated and mechanically ventilated patients with severe chronic obstructive pulmonary disease. Crit Care Med 2000; 28:2721-8. [PMID: 10966241 DOI: 10.1097/00003246-200008000-00006] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
OBJECTIVE To test the hypothesis that replacing 70:30 nitrogen: oxygen (Air-O2) with 70:30 helium:oxygen (He-O2) can decrease dynamic hyperinflation ("intrinsic" positive end-expiratory pressure) in mechanically ventilated patients with chronic obstructive pulmonary disease (COPD), and to document the consequences of such an effect on arterial blood gases and hemodynamics. DESIGN Prospective, interventional study. SETTING Medical intensive care unit, university tertiary care center. PATIENTS Twenty-three intubated, sedated, paralyzed, and mechanically ventilated patients with COPD enrolled within 36 hrs after intubation. INTERVENTIONS Measurements were taken at the following time points, all with the same ventilator settings: a) baseline; b) after 45 mins with He-O2; c) 45 mins after return to Air-O2. The results were then compared to those obtained in a test lung model using the same ventilator settings. MAIN RESULTS (MEAN + SD): Trapped lung volume and intrinsic positive end-expiratory pressure decreased during He-O2 ventilation (215+/-125 mL vs. 99+/-15 mL and 9+/-2.5 cm H2O vs. 5+/-2.7 cm H2O, respectively; p < .05). Likewise, peak and mean airway pressures declined with He-O2 (30+/-5 cm H2O vs. 25+/-6 cm H2O and 8+/-2 cm H2O vs. 7+/-2 cm H2O, respectively; p < .05). These parameters all rose to their baseline values on return to Air-O2 (p < .05 vs. values during He-O2). These results were in accordance with those obtained in the test lung model. There was no modification of arterial blood gases, heart rate, or mean systemic arterial blood pressure. In 12/23 patients, a pulmonary artery catheter was in place, allowing hemodynamic measurements and venous admixture calculations. Switching to He-O2 and back to Air-O2 had no effect on pulmonary artery pressures, right and left ventricular filling pressures, cardiac output, pulmonary and systemic vascular resistance, or venous admixture. CONCLUSION In mechanically ventilated COPD patients with intrinsic positive end-expiratory pressure, the use of He-O2 can markedly reduce trapped lung volume, intrinsic positive end-expiratory pressure, and peak and mean airway pressures. No effect was noted on hemodynamics or arterial blood gases. He-O2 might prove beneficial in this setting to reduce the risk of barotrauma, as well as to improve hemodynamics and gas exchange in patients with very high levels of intrinsic positive end-expiratory pressure.
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Affiliation(s)
- D Tassaux
- Medical Intensive Care Division, University Hospital, Geneva, Switzerland
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Guerin C, Chevre A, Dessirier P, Poncet T, Becquemin MH, Dequin PF, Le Guellec C, Jacques D, Fournier G. Inhaled fenoterol-ipratropium bromide in mechanically ventilated patients with chronic obstructive pulmonary disease. Am J Respir Crit Care Med 1999; 159:1036-42. [PMID: 10194143 DOI: 10.1164/ajrccm.159.4.9710081] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
In 18 patients with chronic obstructive pulmonary disease intubated and mechanically ventilated, we prospectively randomized 200 micrograms fenoterol-80 micrograms ipratropium bromide (four puffs) from a metered-dose inhaler (MDI) versus 1.25 mg fenoterol-500 micrograms ipratropium bromide in 5 ml saline from a nebulizer (NEB). Respiratory mechanics were assessed before and 30 min after the end of each delivery by the rapid end-inspiratory airway occlusion technique. We did vary on single breaths the inflation flow (V) from 0.2 to 1.2 L. s-1, at constant inflation volume. The total respiratory resistance of the respiratory system (Rrs) was partitioned into airway (Rint,rs) and tissue (DeltaRrs) resistances. We found that Rrs was equivalently reduced, from 16.49 +/- 1.37 to 14.85 +/- 1.88 cm H2O. L-1. s with MDI (p < 0.05) and from 18.04 +/- 1.85 to 15.15 +/- 1.33 cm H2O. L-1. s with NEB (p < 0.01). Whereas the prevailing effect of MDI was to reduce Rint,rs, that of NEB was to decrease DeltaRrs. In addition, the V resistance of the respiratory system over the whole range of V was significantly affected by NEB but not by MDI.
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Affiliation(s)
- C Guerin
- Service de Réanimation Médicale, Centre Hospitalier Lyon-Sud, Pierre-Bénite, Service Central d'Explorations Fonctionnelles Respiratiores, Groupe Hospitalier Pitié-Salpétriére, Paris, France
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Kress JP, O'Connor MF, Schmidt GA. Clinical examination reliably detects intrinsic positive end-expiratory pressure in critically ill, mechanically ventilated patients. Am J Respir Crit Care Med 1999; 159:290-4. [PMID: 9872852 DOI: 10.1164/ajrccm.159.1.9805011] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
Critically ill patients requiring mechanical ventilation often develop intrinsic positive end-expiratory pressure (PEEPi). Methods for its detection include an expiratory flow waveform display (not always available), an esophageal pressure transducer (invasive), or a relaxed or paralyzed patient. We sought to determine the accuracy of clinical examination for detecting PEEPi. Examiners blinded to waveform analysis assessed patients for the presence of PEEPi by inspection/palpation and auscultation. If either inspection/palpation or auscultation demonstrated PEEPi, it was said to be present by clinical exam. Clinicians with various levels of experience (attending, resident, student) made 503 observations of 71 patients. Sensitivity (SENS), specificity (SPEC), positive predictive value (PPV), negative predictive value (NPV), and likelihood ratios were determined for inspection/palpation, auscultation, and clinical exam. PEEPi was present during 69.8% of observations. SENS, SPEC, and PPV of clinical exam were 0.72, 0.91, and 0.95 respectively for the examiners as a whole. Likelihood ratio for PEEPi detection by clinical exam was 8.35. Attending intensivists displayed SPEC and PPV of 1.0. NPV was only 0.58 (likelihood ratio 0.31). We conclude that the clinical exam is very good for detecting PEEPi at all experience levels; and further, that the clinical exam is only modestly useful for ruling out PEEPi, therefore, other tests should be used if PEEPi is not detected by clinical exam.
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Affiliation(s)
- J P Kress
- Departments of Medicine and Anesthesia and Critical Care, University of Chicago, Chicago, Illinois, USA
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Cohendy R, Lefrant JY, Mangin R, Eledjam JJ. [Pressure-controlled mechanical ventilation: a simplified titration method of the extrinsic positive expiratory pressure]. ANNALES FRANCAISES D'ANESTHESIE ET DE REANIMATION 1998; 17:1114-21. [PMID: 9835981 DOI: 10.1016/s0750-7658(00)80005-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
OBJECTIVES Extrinsic positive end-expiratory pressure (PEEPe) may improve gas distribution within the lungs, induce alveolar recruitment or, conversely, produce pulmonary overdistension, and modify the respiratory impedance. Under pressure-controlled mechanical ventilation (PCV) this phenomenon modifies the minute ventilation and the dynamic compliance of the respiratory system (Crs,dyn). This study was aimed to assess the incidence of a significant gain in Crs,dyn under the effect of PEEPe during PCV. STUDY DESIGN Prospective, open, descriptive, case series study. PATIENTS Surgical intensive care unit patients, under sedation, neuromuscular blockade and PCV because of severe hypoxaemia (ARDS or acute lung injury). METHODS Four incremental levels of PEEPe (4 to 16 cmH2O) of 30 minute duration were applied. Crs,dyn, and PaO2/FIO2 were recorded at the end of each level of PEEPe. The resulting gain in Crs,dyn was calculated and considered as significant if it was greater than the upper limit of confidence (at 99.8%) of the statistical distribution of all the recorded gains. RESULTS Thirty patients were included, median and extreme values (within brackets) of PaO2/FIO2 of 117 [53-230] and Crs,dyn without PEEPe of 29 [14.3-46.8] mL.cmH2O-1. Among the 120 recorded gains, a gain in Crs,dyn was found significant at least once in 15 tests of PEEPe out of 30. Within the two groups of patients, the increase in PaO2/FIO2 with incremental PEEPe was similar. The levels of PEEPe producing the greatest increase in Crs,dyn were not correlated with the increase in PaO2/FIO2. CONCLUSION In 50% of the studied patients a significant gain in Crs,dyn was found, allowing a less traumatic PCV. These results suggest the clinical usefulness of this method of titration of PEEPe, which requires neither specific devices nor a disconnection of the patient.
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Affiliation(s)
- R Cohendy
- Département d'anesthésie-réanimation, CHU de Nîmes, France
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Abstract
This article provides a review of respiratory mechanics that can be monitored in ventilator-dependent patients during passive and spontaneous breathing. Special focus is placed on resistance, compliance, and work of breathing. A description of methods and techniques, and a summary of clinical observations and applications in critically-ill patients are also included.
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Affiliation(s)
- A Jubran
- Division of Pulmonary and Critical Care Medicine, Edward Hines Jr Veterans Affairs Hospital, Hines, Illinois, USA
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Avanzolini G, Barbini P, Cappello A, Cevenini G, Chiari L. A new approach for tracking respiratory mechanical parameters in real-time. Ann Biomed Eng 1997; 25:154-63. [PMID: 9124729 DOI: 10.1007/bf02738546] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
A new recursive least-squares procedure for on-line tracking of changes in viscoelastic properties of respiratory mechanics is proposed and applied to artificially ventilated patients. Classical least-squares methods based on simple first-order linear models with time-constant parameters generally provide systematic residuals that hardly satisfy standard statistical tests for model validation in terms of residuals. On the other hand, high order and/or nonlinear models introduce parameters whose estimates are of difficult interpretation in a clinical context. The present procedure overcomes these limitations by using the well-known first-order model of respiratory mechanics, wherein variability of resistance and elastance during the breathing cycle is allowed to take into account nonlinear and high-order behavior. Mean and standard deviation of resistance and elastance estimates, relative to a respiratory cycle, are then determined recursively. Feasibility of the method is evaluated by applying it both to experimental and simulated pressure-airflow signals measured in an intensive care unit during mechanical ventilation of patients recovering from heart surgery. Results demonstrate that the proposed procedure provides data description satisfying statistical tests, such as residual whiteness, and reliable estimates of viscoelastic lung parameters even during substantial and fast variations in the respiratory status. In addition, unlike classical methods, the new technique provides the means for on-line evaluation of parameter variability during each respiratory cycle, by the estimate of their standard deviations. This is important in clinical practice, because only the knowledge of reliable parameter values and standard deviations enables significant changes in the respiratory viscoelastic characteristics, and thus in patient status, to be assessed.
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Affiliation(s)
- G Avanzolini
- Dipartimento di Elettronica, Informatica e Sistemistica, Università di Bologna, Italy
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Baconnier PF, Carry PY, Eberhard A, Perdrix JP, Fargnoli JM. A computer program for automatic measurement of respiratory mechanics in artificially ventilated patients. COMPUTER METHODS AND PROGRAMS IN BIOMEDICINE 1995; 47:205-220. [PMID: 8529351 DOI: 10.1016/0169-2607(95)01651-9] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
A program for automatic and periodic determination of respiratory mechanics in artificially ventilated patients is described. Airway pressure and flow signals are obtained from the ventilator in the controlled ventilation mode with constant flow inflation and end-inspiratory pause. Periodically, the program records both signals for a given time and it delimits a ventilatory cycle and its components out of this record. Then, four mechanical parameters of the respiratory system are calculated: (1) Rinit, the resistance obtained with the end-inflation occlusion technique; (2) Ers, the elastance (inspiratory) calculated from the slope of the airway pressure profile during inflation; (3) tau, the expiratory time constant; (4) PEEP, the global positive end expiratory pressure. All parameter measurements have been evaluated in experimental conditions, and are in good agreement with reference values. The complete software includes the display of the signals and of the trends together with automatic disk file backups. An additional program allows one to display the trends again and to create table text files containing all the recorded data for further analysis. The system proved to work in ICU and anaesthesia patients with various ventilators.
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Affiliation(s)
- P F Baconnier
- PRETA-TIMC/IMAG, Laboratoire TIMC, Faculté de Médecine de Grenoble, La Tronche, France
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Rossi A, Polese G, Brandi G, Conti G. Intrinsic positive end-expiratory pressure (PEEPi). Intensive Care Med 1995; 21:522-36. [PMID: 7560497 DOI: 10.1007/bf01706208] [Citation(s) in RCA: 132] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Affiliation(s)
- A Rossi
- Divisione di Pneumologia, Ospedale Maggiore di Borgo Trento, Verona, Italy
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42
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Avanzolini G, Barbini P, Cappello A, Cevenini G. Influence of flow pattern on the parameter estimates of a simple breathing mechanics model. IEEE Trans Biomed Eng 1995; 42:394-402. [PMID: 7729838 DOI: 10.1109/10.376132] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
The first-order model of breathing mechanics is widely used in clinical practice to assess the viscoelastic properties of the respiratory system. Although simple, this model takes the predominant features of the pressure-flow relationship into account but gives highly systematic residuals between measured and model-predicted variables. To achieve a better fit of the entire data set, an approach hypothesizing deterministic time-variations of model parameters, summarized by information-weighted histograms was recently proposed by Bates and Lauzon. The present study uses flow and pressure data measured in intensive care patients to evaluate the real potential of this approach in clinical practice. Information-weighted histograms of the model parameters, estimated by an on-line identification algorithm, were first constructed by taking into account the parameter percentage standard deviations. Then, the influence of the respiratory flow pattern on the calculated histograms was evaluated by the Kolmogorov-Smirnov statistical test. The results show that the method gives good reproducibility under stable experimental conditions. In addition, for a given airflow waveform, an increase in respiratory frequency shifts the histograms representing time-varying viscous properties strongly versus lower values, whereas it shifts the histograms representing time-varying elastic properties slightly versus higher values. On the other hand, the same histograms were highly dependent on the airflow waveform, especially for the viscous properties. Even in a limited experimental work, in all the conditions considered, the method provides results which agree well with the physiological knowledge of nonlinear and multicompartment behavior of respiratory mechanics.
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Affiliation(s)
- G Avanzolini
- Dipartimento di Elettronica, Informatica e Sistemistica, University of Bologna, Italy
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Storme L, Riou Y, Logier R, Dubos JP, Kacet N, Rousseau S, Lequien P. A new application of an old method for respiratory mechanics measurements: the passive inflation method in newborn infants during pressure-controlled ventilation. Pediatr Pulmonol 1994; 18:244-54. [PMID: 7838624 DOI: 10.1002/ppul.1950180409] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
We have previously described a passive inflation method during constant inspiratory flow for measuring total respiratory elastance and resistance during mechanical ventilation in newborns. The simple method for measuring respiratory mechanics had been assessed during decelerating inspiratory flow obtained with pressure controlled ventilation (PCV). We report an application of this method to preterm and full-term mechanically ventilated newborn infants and a comparison with the occlusion method. Twenty-one newborn infants (birth weight 1,060 to 3,650 g; gestational age 26 to 41 weeks), between 1 to 55 days of postnatal age, were enrolled in the study. They were ventilated with a "Servo ventilator 900C," first set in the pressure-controlled mode and then in the volume-controlled mode without changing the tidal volume (VT), inspiratory time or ventilator rate. Flow was measured through a pneumotachograph inserted between the endotracheal tube (ETT) and the breathing circuit; VT was obtained by integration of flow and airway pressure measured directly at the airway opening. Flow, volume, and pressure were plotted on analog X/Y tables to obtain pressure-volume (P/V) and flow-volume (V/V) loops, as well as pressure-time curves. Occlusion was performed by using the end-inspiratory and the end-expiratory pause buttons of the ventilator. The passive inflation method during PCV was based on the analysis of P/V and V/V loops and provided compliance (Crs(PC)infl.), resistance Rrs(PC)infl.) of the respiratory system, and intrinsic positive end-expiratory pressure (PEEP(PC)i,infl.). These values were compared with (1) compliance (Crs(PC)occl.) and intrinsic positive end-expiratory pressure (PEEP(PC)i,occl.) measured by the occlusion method during PCV; (2) static (Crs(VC),occl.) and dynamic (Crs(VC),dyn.) compliance, airway (R(aw)(VC),), tissue (Rrs(VC),visc.) and total resistance (Rrs(VC),occl.), and intrinsic positive end-expiratory pressure (PEEP(VC)i,occl.) measured by the occlusion method during volume-controlled ventilation. Crs(PC),infl. correlated well with Crs(PC),occl., Crs(VC),occl., and Crs(VC),dyn.. Furthermore, Crs(PC),infl. and Crs(VC),dyn. did not differ significantly. Rrs(PC),infl. correlated well and did not differ significantly from total inspiratory resistance, i.e., the sum of R(aw)(VC) and Rrs(VC),vis. PEEPPC,i,infl. correlated well and did not differ significantly from PEEP(PC)i.occl. and from PEEP(VC),i,occl. The passive inflation method can be used during PCV with a decelerating flow waveform. It provides dynamic compliance, inspiratory resistance of the respiratory system, and intrinsic PEEP from the analysis of V/V and P/V loops recorded at the airway opening. This technique is simple to use and well tolerated by preterm and full-term ventilated newborn infants. It can be a good alternative to occlusion methods.
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Affiliation(s)
- L Storme
- Neonatal Intensive Care Unit, Calmette Hospital, Regional University Hospital, Lille, France
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Tantucci C, Corbeil C, Chassé M, Braidy J, Matar N, Milic-Emili J. Flow resistance in mechanically ventilated patients with severe neurological injury. J Crit Care 1993; 8:133-9. [PMID: 8275157 DOI: 10.1016/0883-9441(93)90018-g] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
In 5 mechanically ventilated patients with severe neurological injury (SNI), we measured the respiratory system's flow resistance (Rrs) over a range of inspiratory flows between 0.2 to 2 L/s, at inflation volumes (delta V) ranging from 0.1 to 1 L. Under baseline ventilatory conditions (V = 1 L/s; delta V = 0.95 L), we also partitioned Rrs into airway resistance (Raw) and the additional resistance offered by the tissues of the lung and chest wall (delta Rrs). At all inflation volumes, Rrs decreased hyperbolically with increasing flow but was higher than in normal anesthetized paralyzed subjects (N). At V of 1 L/s and delta V of 0.5 L, Rrs was significantly greater in SNI than in N (7.7 +/- 1.5 v 4.2 +/- 0.5 cm H2O/L/s; P < .01). This discrepancy was due to higher Raw in SNI. Indeed, at V of 1 L/s, Raw (mean +/- SEM) was significantly higher in SNI than in N (4.0 +/- 0.9 v 2.4 +/- 0.2 cm H2O/L/s; P < .001), whereas delta Rrs did not differ significantly. The increased Raw in SNI was due to the fact that these patients were therapeutically hyperventilated (PaCO2 = 30.4 +/- 4.2 mm Hg) and as a result their airways were bronchoconstricted. We conclude that in the intensive care unit setting, hyperventilated patients with severe neurological injury can not be considered to be adequate controls in terms of Rrs and Raw, because hypocapnia induces an increase of Raw and consequently also in Rrs (= Raw+delta Rrs).
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Affiliation(s)
- C Tantucci
- Respiratory Division, Hôpital Saint-Luc, Université de Montréal, Quebec, Canada
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Sydow M, Burchardi H, Zinserling J, Crozier TA, Denecke T, Zielmann S. Intrinsic PEEP determined by static pressure-volume curves--application of a novel automated occlusion method. Intensive Care Med 1993; 19:166-71. [PMID: 8315125 DOI: 10.1007/bf01720534] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
OBJECTIVE Evaluation of new computer-controlled occlusion procedure for determination of intrinsic PEEP in mechanically ventilated patients and comparison with the standard end-expiratory occlusion method. DESIGN Prospective controlled study. SETTING Intensive care unit of a university hospital. PATIENTS 16 patients with acute respiratory failure of different degree and etiology. All patients were mechanically ventilated, heavily sedated and muscle paralyzed (non-depolarising relaxants). The type of ventilator, the inspiration/expiration ratio, FIO2 and PEEP were selected by the attending clinicians according to the patients' need and independently from the study. INTERVENTIONS Static compliance of the respiratory system (Cstat) was determined at varying external end-expiratory pressure settings: ZEEP (= ambient pressure), PEEP of 5 cmH2O and 10 cmH2O. All other ventilator settings were kept constant during the entire procedure. MEASUREMENTS AND RESULTS A computer-controlled occlusion method (SCASS) was used for determination of Cstat. Intrinsic PEEP was determined by SCASS as the extrapolated zero-volume intercept of the regression line of multiple pressure/volume data pairs (PEEPSCASSinspir and PEEPSCASSexpir). Directly thereafter intrinsic PEEP in this particular ventilatory setting was determined by end-expiratory occlusions (PEPPEEO). The intrinsic PEEP values of the different methods were nearly identical with a significant correlation (p < 0.0001). Mean values +/- SD: PEEPSCASSinspir 7.1 +/- 4.3 cmH2O; PEEPSCASSexpir 7.1 +/- 4.5 cmH2O; PEEPEEO 7.1 +/- 4.2 cmH2O. CONCLUSION Since no significant difference between PEEPi values measured by the inspiratory and expiratory occlusion method (SCASS) was seen, this indicates that no alveolar recruitment occurred during the respiratory cycle. This study demonstrates that the automated occlusion method for measuring Cstat system can also be used with high accuracy for determination of intrinsic PEEP in mechanically ventilated patients.
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Affiliation(s)
- M Sydow
- Zentrum für Anaesthesiologie, Rettungs- und Intensivmedizin, Georg-August-Universität Göttingen, Germany
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Valta P, Takala J, Eissa NT, Milic-Emili J. Does alveolar recruitment occur with positive end-expiratory pressure in adult respiratory distress syndrome patients? J Crit Care 1993; 8:34-42. [PMID: 8343857 DOI: 10.1016/0883-9441(93)90031-f] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
We studied the effects of positive end-expiratory pressure (PEEP) (2 to 14 cm H2O) on alveolar recruitment (Vrec), static respiratory compliance, and end-expiratory lung volume (EELV) in nine sedated, paralyzed, mechanically ventilated adult respiratory distress syndrome patients. Positive end-expiratory pressure was applied in increasing and decreasing steps of 2 cm H2O. Flow, tidal volume, and airway pressure were measured. We used the rapid airway occlusion technique to determine static end-inspiratory elastic recoil pressure of the respiratory system (Pst, rs) and intrinsic PEEP (PEEPi). The changes in EELV were measured with respiratory inductive plethysmography. Alveolar recruitment was estimated as the difference in lung volume between PEEP and zero end-expiratory pressure (ZEEP) for the same end-inspiratory Pst, rs (20 cm H2O). We found that (1) Vrec with PEEP up to 14 cm H2O was in general rather small and was absent in two patients; (2) all patients exhibited PEEPi at ZEEP (5.6 +/- 1.0 cm H2O) and little change in EELV and Vrec was achieved until the external PEEP exceeded PEEPi; (3) if end-inspiratory Pst, rs is high at ZEEP, there is little or no alveolar recruitment with PEEP; and (4) Vrec and EELV were slightly higher during stepwise deflation than stepwise inflation with PEEP, except at ZEEP where EELV did not change after inflation-deflation runs with PEEP.
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Affiliation(s)
- P Valta
- Department of Intensive Care, Kuopio University Hospital, Finland
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Tantucci C, Eissa N, Ranieri V, Corbeil C, Milic-Emili J. Respiratory mechanics in ventilated patients. J Crit Care 1992. [DOI: 10.1016/0883-9441(92)90023-z] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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Guttmann J, Eberhard L, Wolff G, Bertschmann W, Zeravik J, Adolph M. Maneuver-free determination of compliance and resistance in ventilated ARDS patients. Chest 1992; 102:1235-42. [PMID: 1395774 DOI: 10.1378/chest.102.4.1235] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
At present, most methods of lung mechanics analysis do not take nonlinearities of compliance and resistance into account. Nevertheless, nonlinearity of compliance is an inherent property of the respiratory system in ARDS and nonlinearity of resistance is an inherent property of the endotracheal tube. Herein we describe a computer-assisted multipoint method (LOOP) for breath-by-breath calculation of total respiratory system compliance (Ctrs) and total respiratory system resistance (Rtrs). Unlike our previously published method, LOOP excludes nonlinearities of compliance and resistance by confining the data used from the P/V/V loop to sequences with constant flow in inspiration and with steadily decreasing flow in expiration. LOOP was applied to five patients ventilated after open heart surgery (HEART group) and 12 patients ventilated for ARDS (ARDS group). The compliance results from LOOP were compared with the semistatic reference values corrected for intrinsic PEEP (CsST,IP). In the ARDS patients the compliance values from LOOP (46 ml/mbar) corresponded well with the semistatic compliance (CsST,IP = 42 ml/mbar). Despite the fact that there is no reference method for resistance known to date, we also determined the semistatic resistance (RsST) at end-inspiratory pause. The resistance values determined with LOOP were 8.5 mbar/L/s (RsST = 7.3 mbar/L/s) in the HEART group and 11.1 mbar/L/s (RsST = 8.6 mbar/L/s) in the ARDS group. LOOP gives a good correspondence between the linear RC model and the measured data in ARDS patients. In conclusion, LOOP requires neither an end-inspiratory pause (EIP) nor additional determination of intrinsic PEEP and gives Ctrs, automatically corrected for IPEEP, as well as Rtrs breath by breath at the bedside.
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Affiliation(s)
- J Guttmann
- Department of Surgery, University of Basel/Switzerland
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50
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Marini JJ. Positive end-expiratory pressure and adult respiratory distress syndrome: What are we missing? J Crit Care 1992. [DOI: 10.1016/0883-9441(92)90009-v] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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