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Schumann S, Ucar S, Wenzel C, Spaeth J. Calculating intrinsic positive end-expiratory pressure from end-expiratory flow in mechanically ventilated children-A study in physical models of the pediatric respiratory system. Pediatr Pulmonol 2024; 59:766-773. [PMID: 38116920 DOI: 10.1002/ppul.26828] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/08/2023] [Revised: 12/06/2023] [Accepted: 12/08/2023] [Indexed: 12/21/2023]
Abstract
RATIONALE The high resistance of pediatric endotracheal tubes (ETTs) exposes mechanically ventilated children to a particular risk of developing intrinsic positive end-expiratory pressure (iPEEP). To date, determining iPEEP at the bedside requires the execution of special maneuvers, interruption of ventilation, or additional invasive measurements. Outside such interventions, iPEEP may be unrecognized. OBJECTIVE To develop a new approach for continuous calculation of iPEEP based on routinely measured end-expiratory flow and ETT resistance. METHODS First, the resistance of pediatric ETTs with inner diameter from 2.0 to 4.5 mm were empirically determined. Second, during simulated ventilation, iPEEP was either calculated from the measured end-expiratory flow and ETT's resistance (iPEEPcalc ) or determined with a hold-maneuver available at the ventilator (iPEEPhold ). Both estimates were compared with the end-expiratory pressure measured at the ETT's tip (iPEEPdirect ) by means of absolute deviations. RESULTS End-expiratory flow and iPEEP increased with decreasing ETT inner diameter and with higher respiratory rates. iPEEPcalc and iPEEPhold were comparable and indicated good correspondence with iPEEPdirect . The largest absolute mean deviation was 1.0 cm H2 O for iPEEPcalc and 1.1 cm H2 O for iPEEPhold . CONCLUSION We conclude that iPEEP can be determined from routinely measured variables and predetermined ETT resistance, which has to be confirmed in the clinical settings. As long as this algorithm is not available in pediatric ICU ventilators, nomograms are provided for estimating the prevailing iPEEP from end-expiratory flow.
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Affiliation(s)
- Stefan Schumann
- Department of Anesthesiology and Critical Care, Medical Center-University of Freiburg, Faculty of Medicine, University of Freiburg, Freiburg, Germany
| | - Sascha Ucar
- Department of Anesthesiology and Critical Care, Medical Center-University of Freiburg, Faculty of Medicine, University of Freiburg, Freiburg, Germany
| | - Christin Wenzel
- Department of Anesthesiology and Critical Care, Medical Center-University of Freiburg, Faculty of Medicine, University of Freiburg, Freiburg, Germany
| | - Johannes Spaeth
- Department of Anesthesiology and Critical Care, Medical Center-University of Freiburg, Faculty of Medicine, University of Freiburg, Freiburg, Germany
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Andrews P, Shiber J, Madden M, Nieman GF, Camporota L, Habashi NM. Myths and Misconceptions of Airway Pressure Release Ventilation: Getting Past the Noise and on to the Signal. Front Physiol 2022; 13:928562. [PMID: 35957991 PMCID: PMC9358044 DOI: 10.3389/fphys.2022.928562] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2022] [Accepted: 06/21/2022] [Indexed: 12/16/2022] Open
Abstract
In the pursuit of science, competitive ideas and debate are necessary means to attain knowledge and expose our ignorance. To quote Murray Gell-Mann (1969 Nobel Prize laureate in Physics): “Scientific orthodoxy kills truth”. In mechanical ventilation, the goal is to provide the best approach to support patients with respiratory failure until the underlying disease resolves, while minimizing iatrogenic damage. This compromise characterizes the philosophy behind the concept of “lung protective” ventilation. Unfortunately, inadequacies of the current conceptual model–that focuses exclusively on a nominal value of low tidal volume and promotes shrinking of the “baby lung” - is reflected in the high mortality rate of patients with moderate and severe acute respiratory distress syndrome. These data call for exploration and investigation of competitive models evaluated thoroughly through a scientific process. Airway Pressure Release Ventilation (APRV) is one of the most studied yet controversial modes of mechanical ventilation that shows promise in experimental and clinical data. Over the last 3 decades APRV has evolved from a rescue strategy to a preemptive lung injury prevention approach with potential to stabilize the lung and restore alveolar homogeneity. However, several obstacles have so far impeded the evaluation of APRV’s clinical efficacy in large, randomized trials. For instance, there is no universally accepted standardized method of setting APRV and thus, it is not established whether its effects on clinical outcomes are due to the ventilator mode per se or the method applied. In addition, one distinctive issue that hinders proper scientific evaluation of APRV is the ubiquitous presence of myths and misconceptions repeatedly presented in the literature. In this review we discuss some of these misleading notions and present data to advance scientific discourse around the uses and misuses of APRV in the current literature.
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Affiliation(s)
- Penny Andrews
- R Adams Cowley Shock Trauma Center, University of Maryland School of Medicine, Baltimore, MD, United States
- *Correspondence: Penny Andrews,
| | - Joseph Shiber
- University of Florida College of Medicine, Jacksonville, FL, United States
| | - Maria Madden
- R Adams Cowley Shock Trauma Center, University of Maryland School of Medicine, Baltimore, MD, United States
| | - Gary F. Nieman
- Department of Surgery, SUNY Upstate Medical University, Syracuse, NY, United States
| | - Luigi Camporota
- Department of Adult Critical Care, Guy’s and St Thomas’ NHS Foundation Trust, Health Centre for Human and Applied Physiological Sciences, London, United Kingdom
| | - Nader M. Habashi
- R Adams Cowley Shock Trauma Center, University of Maryland School of Medicine, Baltimore, MD, United States
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Heili-Frades S, Suarez-Sipmann F, Santos A, Carballosa MP, Naya-Prieto A, Castilla-Reparaz C, Rodriguez-Nieto MJ, González-Mangado N, Peces-Barba G. Continuous monitoring of intrinsic PEEP based on expired CO 2 kinetics: an experimental validation study. CRITICAL CARE : THE OFFICIAL JOURNAL OF THE CRITICAL CARE FORUM 2019; 23:192. [PMID: 31142337 PMCID: PMC6540388 DOI: 10.1186/s13054-019-2430-9] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/24/2018] [Accepted: 04/10/2019] [Indexed: 12/03/2022]
Abstract
Background Quantification of intrinsic PEEP (PEEPi) has important implications for patients subjected to invasive mechanical ventilation. A new non-invasive breath-by-breath method (etCO2D) for determination of PEEPi is evaluated. Methods In 12 mechanically ventilated pigs, dynamic hyperinflation was induced by interposing a resistance in the endotracheal tube. Airway pressure, flow, and exhaled CO2 were measured at the airway opening. Combining different I:E ratios, respiratory rates, and tidal volumes, 52 different levels of PEEPi (range 1.8–11.7 cmH2O; mean 8.45 ± 0.32 cmH2O) were studied. The etCO2D is based on the detection of the end-tidal dilution of the capnogram. This is measured at the airway opening by means of a CO2 sensor in which a 2-mm leak is added to the sensing chamber. This allows to detect a capnogram dilution with fresh air when the pressure coming from the ventilator exceeds the PEEPi. This method was compared with the occlusion method. Results The etCO2D method detected PEEPi step changes of 0.2 cmH2O. Reference and etCO2D PEEPi presented a good correlation (R2 0.80, P < 0.0001) and good agreement, bias − 0.26, and limits of agreement ± 1.96 SD (2.23, − 2.74) (P < 0.0001). Conclusions The etCO2D method is a promising accurate simple way of continuously measure and monitor PEEPi. Its clinical validity needs, however, to be confirmed in clinical studies and in conditions with heterogeneous lung diseases. Electronic supplementary material The online version of this article (10.1186/s13054-019-2430-9) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Sarah Heili-Frades
- Intermediate Respiratory Care Unit, Pulmonology Department, IIS-Fundación Jiménez Díaz, UAM, CIBERES, Madrid, Spain.,CIBER de Enfermedades Respiratorias, Instituto Carlos III, Madrid, Spain
| | - Fernando Suarez-Sipmann
- Servicio de Medicina Intensiva, Hospital Universitario de la Princesa, Madrid, Spain. .,CIBER de Enfermedades Respiratorias, Instituto Carlos III, Madrid, Spain. .,Department of surgical Sciences, Section of Anesthesia and Critical Care, Hedenstierna Laboratory, Uppsala University Hospital, Uppsala, Sweden.
| | - Arnoldo Santos
- ITC Ingeniería y Técnicas Clínicas, CIBER de Enfermedades Respiratorias (CIBERES), Madrid, Spain
| | - Maria Pilar Carballosa
- Intermediate Respiratory Care Unit, Pulmonology Department, IIS-Fundación Jiménez Díaz, UAM, CIBERES, Madrid, Spain
| | - Alba Naya-Prieto
- Intermediate Respiratory Care Unit, Pulmonology Department, IIS-Fundación Jiménez Díaz, UAM, CIBERES, Madrid, Spain
| | | | - Maria Jesús Rodriguez-Nieto
- Intermediate Respiratory Care Unit, Pulmonology Department, IIS-Fundación Jiménez Díaz, UAM, CIBERES, Madrid, Spain.,CIBER de Enfermedades Respiratorias, Instituto Carlos III, Madrid, Spain
| | - Nicolás González-Mangado
- Intermediate Respiratory Care Unit, Pulmonology Department, IIS-Fundación Jiménez Díaz, UAM, CIBERES, Madrid, Spain.,CIBER de Enfermedades Respiratorias, Instituto Carlos III, Madrid, Spain
| | - German Peces-Barba
- Intermediate Respiratory Care Unit, Pulmonology Department, IIS-Fundación Jiménez Díaz, UAM, CIBERES, Madrid, Spain.,CIBER de Enfermedades Respiratorias, Instituto Carlos III, Madrid, Spain
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Ruiz Ferrón F, Serrano Simón J. La monitorización convencional no es suficiente para valorar el esfuerzo respiratorio durante la ventilación asistida. Med Intensiva 2019; 43:197-206. [DOI: 10.1016/j.medin.2018.02.015] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2017] [Revised: 01/25/2018] [Accepted: 02/14/2018] [Indexed: 12/28/2022]
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Spaeth J, Ott M, Karzai W, Grimm A, Wirth S, Schumann S, Loop T. Double-lumen tubes and auto-PEEP during one-lung ventilation. Br J Anaesth 2016; 116:122-30. [DOI: 10.1093/bja/aev398] [Citation(s) in RCA: 97] [Impact Index Per Article: 12.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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Marini JJ. Dynamic hyperinflation and auto-positive end-expiratory pressure: lessons learned over 30 years. Am J Respir Crit Care Med 2011; 184:756-62. [PMID: 21700908 DOI: 10.1164/rccm.201102-0226pp] [Citation(s) in RCA: 70] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
Auto-positive end-expiratory pressure (auto-PEEP; AP) and dynamic hyperinflation (DH) may affect hemodynamics, predispose to barotrauma, increase work of breathing, cause dyspnea, disrupt patient-ventilator synchrony, confuse monitoring of hemodynamics and respiratory system mechanics, and interfere with the effectiveness of pressure-regulated ventilation. Although basic knowledge regarding the clinical physiology and management of AP during mechanical ventilation has evolved impressively over the 30 years since DH and AP were first brought to clinical attention, novel and clinically relevant characteristics of this complex phenomenon continue to be described. This discussion reviews some of the more important aspects of AP that bear on the care of the ventilated patient with critical illness.
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Affiliation(s)
- John J Marini
- Pulmonary and Critical Care Medicine, University of Minnesota, St Paul, MN 55101-2595, USA.
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Syring RS, Otto CM, Spivack RE, Markstaller K, Baumgardner JE. Maintenance of end-expiratory recruitment with increased respiratory rate after saline-lavage lung injury. J Appl Physiol (1985) 2006; 102:331-9. [PMID: 16959915 DOI: 10.1152/japplphysiol.00002.2006] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Cyclical recruitment of atelectasis with each breath is thought to contribute to ventilator-associated lung injury. Extrinsic positive end-expiratory pressure (PEEPe) can maintain alveolar recruitment at end exhalation, but PEEPe depresses cardiac output and increases overdistension. Short exhalation times can also maintain end-expiratory recruitment, but if the mechanism of this recruitment is generation of intrinsic PEEP (PEEPi), there would be little advantage compared with PEEPe. In seven New Zealand White rabbits, we compared recruitment from increased respiratory rate (RR) to recruitment from increased PEEPe after saline lavage. Rabbits were ventilated in pressure control mode with a fraction of inspired O(2) (Fi(O(2))) of 1.0, inspiratory-to-expiratory ratio of 2:1, and plateau pressure of 28 cmH(2)O, and either 1) high RR (24) and low PEEPe (3.5) or 2) low RR (7) and high PEEPe (14). We assessed cyclical lung recruitment with a fast arterial Po(2) probe, and we assessed average recruitment with blood gas data. We measured PEEPi, cardiac output, and mixed venous saturation at each ventilator setting. Recruitment achieved by increased RR and short exhalation time was nearly equivalent to recruitment achieved by increased PEEPe. The short exhalation time at increased RR, however, did not generate PEEPi. Cardiac output was increased on average 13% in the high RR group compared with the high PEEPe group (P < 0.001), and mixed venous saturation was consistently greater in the high RR group (P < 0.001). Prevention of end-expiratory derecruitment without increased end-expiratory pressure suggests that another mechanism, distinct from intrinsic PEEP, plays a role in the dynamic behavior of atelectasis.
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Affiliation(s)
- Rebecca S Syring
- Department of Clinical Studies, Section of Critical Care, School of Veterinary Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA
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Mellema MS, Haskins SC. Weaning from mechanical ventilation. CLINICAL TECHNIQUES IN SMALL ANIMAL PRACTICE 2000; 15:157-64. [PMID: 11109717 DOI: 10.1053/svms.2000.18293] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Patients that require positive pressure ventilation to maintain sufficient alveolar ventilation or pulmonary gas exchange may eventually reach a point in the course of their care wherein mechanical ventilation is no longer necessary. This process of transferring the work of breathing from the ventilator back to the patient is referred to as ventilator weaning. The term "ventilator weaning" may be used to refer to all methods by which this transfer of workload may be accomplished. In many patients, particularly those with short-lasting or readily correctable causes of respiratory insufficiency (e.g., general anesthesia), the discontinuation of positive pressure ventilation may be easily achieved. Indeed, in patients awakening from general anesthesia, the axiom "awake enough to blink, awake enough to breath" may prove to be a sufficient guideline. However, in those patients requiring long-term mechanical ventilatory support, the process can prove to be both frustrating and exceptionally challenging. It is of crucial importance to identify those patients that may be successfully weaned because of both the financial impact of prolonged intensive care unit hospitalization and the risks imposed on the patient by the process of positive pressure ventilation. To be able to predict which patients may be ready to be weaned from the ventilator requires an understanding of the balance between the work of breathing (ventilatory load) and the ability of the patient's respiratory pump to meet those needs (ventilatory capacity). The management of patients experiencing difficulty during the weaning process requires that the clinician recognize imbalances between ventilatory load and capacity and to correct these imbalances once identified.
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Affiliation(s)
- M S Mellema
- Veterinary Medical Teaching Hospital, Davis, CA, USA
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Schuessler TF, Gottfried SB, Bates JH. A model of the spontaneously breathing patient: applications to intrinsic PEEP and work of breathing. J Appl Physiol (1985) 1997; 82:1694-703. [PMID: 9134921 DOI: 10.1152/jappl.1997.82.5.1694] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
Intrinsic positive end-expiratory pressure (PEEPi) and inspiratory work of breathing (WI) are important factors in the management of severe obstructive respiratory disease. We used a computer model of spontaneously breathing patients with chronic obstructive pulmonary disease to assess the sensitivity of measurement techniques for dynamic PEEPi (PEEPidyn) and WI to expiratory muscle activity (EMA) and cardiogenic oscillations (CGO) on esophageal pressure. Without EMA and CGO, both PEEPidyn and WI were accurately estimated (r = 0.999 and 0.95, respectively). Addition of moderate EMA caused PEEPidyn and WI to be systematically overestimated by 141 and 52%, respectively. Furthermore, CGO introduced large random errors, obliterating the correlation between the true and estimated values for both PEEPidyn (r = 0.29) and WI (r = 0.38). Thus the accurate estimation of PEEPidyn and WI requires steps to be taken to ameliorate the adverse effects of both EMA and CGO. Taking advantage of our simulations, we also investigated the relationship between PEEPidyn and static PEEPi (PEEPistat). The PEEPidyn/PEEPistat ratio decreased as stress adaptation in the lung was increased, suggesting that heterogeneity of expiratory flow limitation is responsible for the discrepancies between PEEPidyn and PEEPistat that have been reported in patients with severe airway obstruction.
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Affiliation(s)
- T F Schuessler
- Meakins-Christie Laboratories, McGill University, Montreal, Quebec, Canada
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