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Cammarota G, Vaschetto R, Vetrugno L, Maggiore SM. Monitoring lung recruitment. Curr Opin Crit Care 2024; 30:268-274. [PMID: 38690956 DOI: 10.1097/mcc.0000000000001157] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/03/2024]
Abstract
PURPOSE OF REVIEW This review explores lung recruitment monitoring, covering techniques, challenges, and future perspectives. RECENT FINDINGS Various methodologies, including respiratory system mechanics evaluation, arterial bold gases (ABGs) analysis, lung imaging, and esophageal pressure (Pes) measurement are employed to assess lung recruitment. In support to ABGs analysis, the assessment of respiratory mechanics with hysteresis and recruitment-to-inflation ratio has the potential to evaluate lung recruitment and enhance mechanical ventilation setting. Lung imaging tools, such as computed tomography scanning, lung ultrasound, and electrical impedance tomography (EIT) confirm their utility in following lung recruitment with the advantage of radiation-free and repeatable application at the bedside for sonography and EIT. Pes enables the assessment of dorsal lung tendency to collapse through end-expiratory transpulmonary pressure. Despite their value, these methodologies may require an elevated expertise in their application and data interpretation. However, the information obtained by these methods may be conveyed to build machine learning and artificial intelligence algorithms aimed at improving the clinical decision-making process. SUMMARY Monitoring lung recruitment is a crucial component of managing patients with severe lung conditions, within the framework of a personalized ventilatory strategy. Although challenges persist, emerging technologies offer promise for a personalized approach to care in the future.
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Affiliation(s)
- Gianmaria Cammarota
- Department of Translational Medicine, Università del Piemonte Orientale, Novara
| | - Rosanna Vaschetto
- Department of Translational Medicine, Università del Piemonte Orientale, Novara
| | - Luigi Vetrugno
- Department of Medical, Oral and Biotechnological Sciences
| | - Salvatore M Maggiore
- Department of Anesthesiology and Intensive Care, Ospedale SS Annunziata & Department of Innovative Technologies in Medicine and Odonto-stomatology, Università Gabriele D'Annunzio di Chieti-Pescara, Chieti, Italy
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Mojoli F, Pozzi M, Arisi E. Setting positive end-expiratory pressure: using the pressure-volume curve. Curr Opin Crit Care 2024; 30:35-42. [PMID: 38085871 DOI: 10.1097/mcc.0000000000001127] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2024]
Abstract
PURPOSE OF REVIEW To discuss the role of pressure-volume curve (PV curve) in exploring elastic properties of the respiratory system and setting mechanical ventilator to reduce ventilator-induced lung injury. RECENT FINDINGS Nowadays, quasi-static PV curves and loops can be easily obtained and analyzed at the bedside without disconnection of the patient from the ventilator. It is shown that this tool can provide useful information to optimize ventilator setting. For example, PV curves can assess for patient's individual potential for lung recruitability and also evaluate the risk for lung injury of the ongoing mechanical ventilation setting. SUMMARY In conclusion, PV curve is an easily available bedside tool: its correct interpretation can be extremely valuable to enlighten potential for lung recruitability and select a high or low positive end-expiratory pressure (PEEP) strategy. Furthermore, recent studies have shown that PV curve can play a significant role in PEEP and driving pressure fine tuning: clinical studies are needed to prove whether this technique will improve outcome.
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Affiliation(s)
- Francesco Mojoli
- Department of Clinical-Surgical, Diagnostic and Pediatric Sciences, Unit of Anesthesia and Intensive Care, University of Pavia, Pavia, Italy
- Anesthesia and Intensive Care, Fondazione IRCCS Policlinico S. Matteo, Pavia, Italy
| | - Marco Pozzi
- Anesthesia and Intensive Care, Fondazione IRCCS Policlinico S. Matteo, Pavia, Italy
| | - Eric Arisi
- Anesthesia and Intensive Care, Fondazione IRCCS Policlinico S. Matteo, Pavia, Italy
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Sattari S, Mariano CA, Eskandari M. Pressure-volume mechanics of inflating and deflating intact whole organ porcine lungs. J Biomech 2023; 157:111696. [PMID: 37413822 DOI: 10.1016/j.jbiomech.2023.111696] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2022] [Revised: 06/14/2023] [Accepted: 06/19/2023] [Indexed: 07/08/2023]
Abstract
Pressure-volume curves of the lung are classical measurements of lung function and are impacted by changes in lung structure due to disease or shifts in air-delivery volume or cycling rate. Diseased and preterm infant lungs have been found to show heterogeneous behavior which is highly frequency dependent. This breathing rate dependency has motivated the exploration of multi-frequency oscillatory ventilators to deliver volume oscillation with optimal frequencies for various portions of the lung to provide more uniform air distribution. The design of these advanced ventilators requires the examination of lung function and mechanics, and an improved understanding of the pressure-volume response of the lung. Therefore, to comprehensively analyze whole lung organ mechanics, we investigate six combinations of varying applied volumes and frequencies using ex-vivo porcine specimens and our custom-designed electromechanical breathing apparatus. Lung responses were evaluated through measurements of inflation and deflation slopes, static compliance, peak pressure and volume, as well as hysteresis, energy loss, and pressure relaxation. Generally, we observed that the lungs were stiffer when subjected to faster breathing rates and lower inflation volumes. The lungs exhibited greater inflation volume dependencies compared to frequency dependencies. This study's reported response of the lung to variations of inflation volume and breathing rate can help the optimization of conventional mechanical ventilators and inform the design of advanced ventilators. Although frequency dependency is found to be minimal in normal porcine lungs, this preliminary study lays a foundation for comparison with pathological lungs, which are known to demonstrate marked rate dependency.
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Affiliation(s)
- Samaneh Sattari
- Department of Mechanical Engineering, University of California at Riverside, Riverside, CA, USA
| | - Crystal A Mariano
- Department of Mechanical Engineering, University of California at Riverside, Riverside, CA, USA
| | - Mona Eskandari
- Department of Mechanical Engineering, University of California at Riverside, Riverside, CA, USA; BREATHE Center, School of Medicine, University of California at Riverside, Riverside, CA, USA; Department of Bioengineering, University of California at Riverside, Riverside, CA, USA.
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Mojoli F, Pozzi M, Arisi E, Mongodi S, Orlando A, Maggio G, Capra Marzani F, Brochard L. Tidal lung hysteresis to interpret PEEP-induced changes in compliance in ARDS patients. Crit Care 2023; 27:233. [PMID: 37312187 PMCID: PMC10261834 DOI: 10.1186/s13054-023-04506-6] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2023] [Accepted: 05/23/2023] [Indexed: 06/15/2023] Open
Abstract
BACKGROUND In ARDS, the PEEP level associated with the best respiratory system compliance is often selected; however, intra-tidal recruitment can increase compliance, falsely suggesting improvement in baseline mechanics. Tidal lung hysteresis increases with intra-tidal recruitment and can help interpreting changes in compliance. This study aims to assess tidal recruitment in ARDS patients and to test a combined approach, based on tidal hysteresis and compliance, to interpret decremental PEEP trials. METHODS A decremental PEEP trial was performed in 38 COVID-19 moderate to severe ARDS patients. At each step, we performed a low-flow inflation-deflation manoeuvre between PEEP and a constant plateau pressure, to measure tidal hysteresis and compliance. RESULTS According to changes of tidal hysteresis, three typical patterns were observed: 10 (26%) patients showed consistently high tidal-recruitment, 12 (32%) consistently low tidal-recruitment and 16 (42%) displayed a biphasic pattern moving from low to high tidal-recruitment below a certain PEEP. Compliance increased after 82% of PEEP step decreases and this was associated to a large increase of tidal hysteresis in 44% of cases. Agreement between best compliance and combined approaches was accordingly poor (K = 0.024). The combined approach suggested to increase PEEP in high tidal-recruiters, mainly to keep PEEP constant in biphasic pattern and to decrease PEEP in low tidal-recruiters. PEEP based on the combined approach was associated with lower tidal hysteresis (92.7 ± 20.9 vs. 204.7 ± 110.0 mL; p < 0.001) and lower dissipated energy per breath (0.1 ± 0.1 vs. 0.4 ± 0.2 J; p < 0.001) compared to the best compliance approach. Tidal hysteresis ≥ 100 mL was highly predictive of tidal recruitment at next PEEP step reduction (AUC 0.97; p < 0.001). CONCLUSIONS Assessment of tidal hysteresis improves the interpretation of decremental PEEP trials and may help limiting tidal recruitment and energy dissipated into the respiratory system during mechanical ventilation of ARDS patients.
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Affiliation(s)
- Francesco Mojoli
- Department of Clinical-Surgical, Diagnostic and Pediatric Sciences, Unit of Anesthesia, University of Pavia, Pavia, Italy.
- Anesthesia and Intensive Care, Fondazione IRCCS Policlinico S. Matteo, Pavia, Italy.
| | - Marco Pozzi
- Anesthesia and Intensive Care, Fondazione IRCCS Policlinico S. Matteo, Pavia, Italy
| | - Eric Arisi
- Anesthesia and Intensive Care, Fondazione IRCCS Policlinico S. Matteo, Pavia, Italy
| | - Silvia Mongodi
- Anesthesia and Intensive Care, Fondazione IRCCS Policlinico S. Matteo, Pavia, Italy
| | - Anita Orlando
- Anesthesia and Intensive Care, Fondazione IRCCS Policlinico S. Matteo, Pavia, Italy
| | - Giuseppe Maggio
- Anesthesia and Intensive Care, Fondazione IRCCS Policlinico S. Matteo, Pavia, Italy
| | | | - Laurent Brochard
- Keenan Centre for Biomedical Research, Li Ka Shing Knowledge Institute, Unity Health Toronto, Toronto, ON, Canada
- Interdepartmental Division of Critical Care Medicine, University of Toronto, Toronto, ON, Canada
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Comparison of two methods of determining lung de-recruitment, using the forced oscillation technique. Eur J Appl Physiol 2018; 118:2213-2224. [PMID: 30062516 DOI: 10.1007/s00421-018-3949-1] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2018] [Accepted: 07/21/2018] [Indexed: 10/28/2022]
Abstract
Airway closure has proved to be important in a number of respiratory diseases and may be the primary functional defect in asthma. A surrogate measure of closing volume can be identified using the forced oscillation technique (FOT), by performing a deflation maneuver and examining the resultant reactance (Xrs) lung volume relationship. This study aims to determine if a slow vital capacity maneuver can be used instead of this deflation maneuver and compare it to existing more complex techniques. Three subject groups were included in the study; healthy (n = 29), asthmatic (n = 18), and COPD (n = 10) for a total of 57 subjects. Reactance lung volume curves were generated via FOT recordings during two different breathing manoeuvres (both pre and post bronchodilator). The correlation and agreement between surrogate closing volume (Volcrit) and reactance (Xrscrit) at this volume was analysed. The changes in Volcrit and Xrscrit pre and post bronchodilator were also analysed. Across all three subject groups, the two different measures of Volcrit were shown to be statistically equivalent (p > 0.05) and demonstrated a strong fit to the data (R2 = 0.49, 0.78, 0.59, for asthmatic, COPD and healthy subject groups, respectively). A bias was evident between the two measurements of Xrscrit with statistically different means (p < 0.05). However, the two measurements of Xrscrit displayed the same trends. In conclusion, we have developed an alternative technique for measuring airway closure from FOT recordings. The technique delivers equivalent and possibly more sensitive results to previous methods while being simple and easily performed by the patient.
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Soldati G, Demi M, Inchingolo R, Smargiassi A, Demi L. On the Physical Basis of Pulmonary Sonographic Interstitial Syndrome. JOURNAL OF ULTRASOUND IN MEDICINE : OFFICIAL JOURNAL OF THE AMERICAN INSTITUTE OF ULTRASOUND IN MEDICINE 2016; 35:2075-86. [PMID: 27503755 DOI: 10.7863/ultra.15.08023] [Citation(s) in RCA: 93] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Affiliation(s)
- Gino Soldati
- Emergency Medicine Unit, Valle del Serchio General Hospital, Lucca, Italy
| | - Marcello Demi
- Department of Medical Image Processing, Fondazione Toscana Gabriele Monasterio, Pisa, Italy
| | - Riccardo Inchingolo
- Department of Pulmonary Medicine, A. Gemelli University Hospital, Rome, Italy
| | - Andrea Smargiassi
- Department of Pulmonary Medicine, A. Gemelli University Hospital, Rome, Italy
| | - Libertario Demi
- Laboratory of Biomedical Diagnostics, Eindhoven University of Technology, Eindhoven, the Netherlands
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Soldati G, Smargiassi A, Inchingolo R, Sher S, Nenna R, Valente S, Inchingolo CD, Corbo GM. Lung ultrasonography may provide an indirect estimation of lung porosity and airspace geometry. Respiration 2014; 88:458-68. [PMID: 25376260 DOI: 10.1159/000368086] [Citation(s) in RCA: 63] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2014] [Accepted: 08/23/2014] [Indexed: 11/19/2022] Open
Abstract
BACKGROUND Echographic vertical artifacts (B-lines) in chest ultrasonography have often been associated with pathological patterns. A scientifically sound explanation of these artifacts has not yet been proposed. OBJECTIVES The 'spongy' nature of the lung in its liquid and solid components and the changes that take place in peripheral airspace (PAS) geometry might be the key point to understanding these phenomena. METHODS Six excised right rabbit lungs were obtained. Each lung underwent direct ultrasound evaluation in two different conditions: at complete tissue elastic recoil volume and at pulmonary expansion volume achieved by applying a constant positive pressure of 12 cm H2O. Lung volumes and densities were reported in both conditions. Histological examination was performed on three naturally collapsed lungs and on three lungs under positive pressure inflation after having been fixed in formalin solution. RESULTS Mean volumes of naturally collapsed lungs and fixed expanded lungs were 11.2 ± 0.36 and 44.83 ± 3.03 ml, respectively. Mean densities were 0.622 ± 0.016 and 0.155 ± 0.007 g/ml, respectively. Ultrasound evaluation of collapsed lungs showed dense vertical artifacts and a 'white lung' pattern, while the evaluation of expanded lungs showed hyperechoic line and horizontal artifacts of reflection. Histological evaluation showed a different PAS geometry in collapsed lungs caused by alveolar size reduction and shape changes with unfolded and closed units modifying the peripheral porosity of the frothy nature of the lung. CONCLUSIONS Airspace geometry, frothy nature and porosity are the determinants of the different behavior of ultrasound interacting with the subpleural lung parenchyma. Chest ultrasound may thus be interpreted as an indirect 'estimator' of lung porosity.
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Affiliation(s)
- Gino Soldati
- Emergency Medicine Unit, Castelnuovo Garfagnana General Hospital, Lucca, Italy
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Cereda M, Xin Y, Emami K, Huang J, Rajaei J, Profka H, Han B, Mongkolwisetwara P, Kadlecek S, Kuzma NN, Pickup S, Kavanagh BP, Deutschman CS, Rizi RR. Positive end-expiratory pressure increments during anesthesia in normal lung result in hysteresis and greater numbers of smaller aerated airspaces. Anesthesiology 2013; 119:1402-9. [PMID: 24025616 PMCID: PMC3987989 DOI: 10.1097/aln.0b013e3182a9b0c1] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
BACKGROUND Although it is recognized that pulmonary hysteresis can influence the effects of positive end-expiratory pressure (PEEP), the extent to which expansion of previously opened (vs. newly opening) peripheral airspaces contribute to increased lung volume is unknown. METHODS Following a recruitment maneuver, rats were ventilated with constant tidal volumes and imaged during ascending and descending ramps of PEEP. RESULTS The authors estimated peripheral airspace dimensions by measuring the apparent diffusion coefficient of He in 10 rats. In a separate group (n = 5) undergoing a similar protocol, the authors used computerized tomography to quantify lung volume. Hysteresis was confirmed by larger end-inspiratory lung volume (mean ± SD; all PEEP levels included): 8.4 ± 2.8 versus 6.8 ± 2.0 ml (P < 0.001) and dynamic compliance: 0.52 ± 0.12 versus 0.42 ± 0.09 ml/cm H2O (P < 0.001) during descending versus ascending PEEP ramps. Apparent diffusion coefficient increased with PEEP, but it was smaller during the descending versus ascending ramps for corresponding levels of PEEP: 0.168 ± 0.019 versus 0.183 ± 0.019 cm/s (P < 0.001). Apparent diffusion coefficient was smaller in the posterior versus anterior lung regions, but the effect of PEEP and hysteresis on apparent diffusion coefficient was greater in the posterior regions. CONCLUSIONS The authors' study results suggest that in healthy lungs, larger lung volumes due to hysteresis are associated with smaller individual airspaces. This may be explained by opening of previously nonaerated peripheral airspaces rather than expansion of those already aerated. Setting PEEP on a descending ramp may minimize distension of individual airspaces.
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Affiliation(s)
- Maurizio Cereda
- Assistant Professor, Department of Anesthesiology and Critical Care, University of Pennsylvania, Philadelphia, Pennsylvania
| | - Yi Xin
- Research Specialist, Department of Radiology, University of Pennsylvania, Philadelphia, Pennsylvania
| | - Kiarash Emami
- Project Manager, Department of Radiology, University of Pennsylvania, Philadelphia, Pennsylvania
| | - Jessie Huang
- Student, University of Pennsylvania, Philadelphia, Pennsylvania
| | - Jennia Rajaei
- Student, University of Pennsylvania, Philadelphia, Pennsylvania
| | - Harrilla Profka
- Research Specialist, Department of Radiology, University of Pennsylvania, Philadelphia, Pennsylvania
| | - Biao Han
- Research Specialist, Department of Radiology, University of Pennsylvania, Philadelphia, Pennsylvania
| | | | - Stephen Kadlecek
- Research Assistant Professor, Department of Radiology, University of Pennsylvania, Philadelphia, Pennsylvania
| | - Nicholas N. Kuzma
- Research Assistant Professor, Department of Radiology, University of Pennsylvania, Philadelphia, Pennsylvania
| | - Stephen Pickup
- Technical Director, Department of Radiology, University of Pennsylvania, Philadelphia, Pennsylvania
| | - Brian P. Kavanagh
- Professor, Departments of Critical Care Medicine and Anesthesia, Hospital for Sick Children, University of Toronto, Toronto, Ontario, Canada
| | - Clifford S. Deutschman
- Professor, Department of Anesthesiology and Critical Care and Stavropoulos Sepsis Research Program, University of Pennsylvania, Philadelphia, Pennsylvania
| | - Rahim R. Rizi
- Professor, Department of Radiology, University of Pennsylvania, Philadelphia, Pennsylvania
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Smith BJ, Bates JHT. Assessing the Progression of Ventilator-Induced Lung Injury in Mice. IEEE Trans Biomed Eng 2013; 60:3449-57. [PMID: 23751952 DOI: 10.1109/tbme.2013.2267151] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Patients with acute respiratory distress syndrome receiving mechanical ventilation typically experience repetitive closure (derecruitment) and subsequent reopening (recruitment) of airways and alveoli. This can lead, over time, to further ventilator-induced lung injury (VILI). Recruitment and derecruitment (R/D) thus reflect both the current level of lung injury and the risk for sustaining further injury. Accordingly, we investigated how the dynamics of R/D are altered as VILI develops following application of high tidal volume ventilation in initially healthy mice. R/D occurring on subsecond timescales was assessed from the shape of the pressure-volume ( PV) loop measured during a single large breath. R/D occurring on a timescale of minutes was evaluated via a derecruitability test in which we tracked the progressive increases in lung elastance occurring during periods of mechanical ventilation immediately following a recruitment maneuver. The degrees of R/D occurring on these different times scales were strongly correlated. To interpret these findings in quantitative terms, we developed a computational model of the lung in which changes in lung volume occurred both via R/D and distention of already open lung units. Fitting this model to measured PV loops indicates that VILI causes R/D both to increase and to occur at progressively higher pressures, and that the lung tissue that remains open during the breath becomes progressively more overdistended. We conclude that the dynamic PV loop in conjunction with our computational model can be used to assess the current injury state of the lung as well as its likelihood of sustaining further VILI.
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Frazer DG, Lindsley WG, McKinney W, Reynolds JS, Franz GN, Jackson M, Goldsmith WT. A model of the recruitment-derecruitment and volume of lung units in an excised lung as it is inflated-deflated between minimum and maximum lung volume. J Biomech Eng 2013; 135:34503. [PMID: 24231819 DOI: 10.1115/1.4023372] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2012] [Accepted: 01/10/2013] [Indexed: 11/08/2022]
Abstract
The role of the recruitment-derecruitment of small structures in the lung (lung units) as the lung increases and decreases in volume has been debated. The objective of this study was to develop a model to estimate the change in the number and volume of open lung units as an excised lung is inflated-deflated between minimum and maximum lung volume. The model was formulated based on the observation that the compliance of the slowly changing quasi-static pressure-volume (P-V) curve of an excised rat lung can differ from the compliance of a faster changing small sinusoidal pressure volume perturbations superimposed on the curve. In those regions of the curve where differences in compliance occur, the lung tissue properties exhibit nonlinear characteristics, which cannot be linearized using "incremental" or "small signal" analysis. The model attributes the differences between the perturbation and quasi-static compliance to an additional nonlinear compliance term that results from the sequential opening and closing of lung units. Using this approach, it was possible to calculate the normalized average volume and the normalized number of open units as the lung is slowly inflated-deflated. Results indicate that the normalized average volume and the normalized number of open units are not linearly related to normalized lung volume, and at equal lung volumes the normalized number of open units is greater and the normalized average lung unit volume is smaller during lung deflation when compared to lung inflation. In summary, a model was developed to describe the recruitment-derecruitment process in excised lungs based on the differences between small signal perturbation compliance and quasi-static compliance. Values of normalized lung unit volume and the normalized number of open lung units were shown to be nonlinear functions of both transpulmonary pressure and normalized lung volume.
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Sundaresan A, Chase JG, Shaw GM, Chiew YS, Desaive T. Model-based optimal PEEP in mechanically ventilated ARDS patients in the intensive care unit. Biomed Eng Online 2011; 10:64. [PMID: 21794116 PMCID: PMC3167768 DOI: 10.1186/1475-925x-10-64] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2011] [Accepted: 07/27/2011] [Indexed: 01/11/2023] Open
Abstract
BACKGROUND The optimal level of positive end-expiratory pressure (PEEP) is still widely debated in treating acute respiratory distress syndrome (ARDS) patients. Current methods of selecting PEEP only provide a range of values and do not provide unique patient-specific solutions. Model-based methods offer a novel way of using non-invasive pressure-volume (PV) measurements to estimate patient recruitability. This paper examines the clinical viability of such models in pilot clinical trials to assist therapy, optimise patient-specific PEEP, assess the disease state and response over time. METHODS Ten patients with acute lung injury or ARDS underwent incremental PEEP recruitment manoeuvres. PV data was measured at increments of 5 cmH2O and fitted to the recruitment model. Inspiratory and expiratory breath holds were performed to measure airway resistance and auto-PEEP. Three model-based metrics are used to optimise PEEP based on opening pressures, closing pressures and net recruitment. ARDS status was assessed by model parameters capturing recruitment and compliance. RESULTS Median model fitting error across all patients for inflation and deflation was 2.8% and 1.02% respectively with all patients experiencing auto-PEEP. In all three metrics' cases, model-based optimal PEEP was higher than clinically selected PEEP. Two patients underwent multiple recruitment manoeuvres over time and model metrics reflected and tracked the state or their ARDS. CONCLUSIONS For ARDS patients, the model-based method presented in this paper provides a unique, non-invasive method to select optimal patient-specific PEEP. In addition, the model has the capability to assess disease state over time using these same models and methods.
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Affiliation(s)
- Ashwath Sundaresan
- Department of Mechanical Engineering, College of Engineering, University of Canterbury, Private Bag 8140, Christchurch, New Zealand
| | - J Geoffrey Chase
- Department of Mechanical Engineering, University of Canterbury, Private Bag 8140, Christchurch, New Zealand
| | - Geoffrey M Shaw
- Department of Intensive Care, Christchurch Hospital, Private Bag 4710, Christchurch, New Zealand
| | - Yeong Shiong Chiew
- Department of Mechanical Engineering, College of Engineering, University of Canterbury, Private Bag 8140, Christchurch, New Zealand
| | - Thomas Desaive
- Cardiovascular Research Center, Institute of Physics, Allée du 6 Août, 17 (Bât B5), B4000 Liège (Belgium
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Sundaresan A, Yuta T, Hann CE, Chase JG, Shaw GM. A minimal model of lung mechanics and model-based markers for optimizing ventilator treatment in ARDS patients. COMPUTER METHODS AND PROGRAMS IN BIOMEDICINE 2009; 95:166-180. [PMID: 19327863 DOI: 10.1016/j.cmpb.2009.02.008] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/16/2008] [Revised: 12/22/2008] [Accepted: 02/20/2009] [Indexed: 05/27/2023]
Abstract
A majority of patients admitted to the Intensive Care Unit (ICU) require some form of respiratory support. In the case of Acute Respiratory Distress Syndrome (ARDS), the patient often requires full intervention from a mechanical ventilator. ARDS is also associated with mortality rate as high as 70%. Despite many recent studies on ventilator treatment of the disease, there are no well established methods to determine the optimal Positive End-Expiratory Pressure (PEEP) or other critical ventilator settings for individual patients. A model of fundamental lung mechanics is developed based on capturing the recruitment status of lung units. The main objective of this research is to develop a minimal model that is clinically effective in determining PEEP. The model was identified for a variety of different ventilator settings using clinical data. The fitting error was between 0.1% and 4% over the inflation limb and between 0.3% and 13% over the deflation limb at different PEEP settings. The model produces good correlation with clinical data, and is clinically applicable due to the minimal number of patient specific parameters to identify. The ability to use this identified patient specific model to optimize ventilator management is demonstrated by its ability to predict the patient specific response of PEEP changes before clinically applying them. Predictions of recruited lung volume change with change in PEEP have a median absolute error of 1.87% (IQR: 0.93-4.80%; 90% CI: 0.16-11.98%) for inflation and a median of 5.76% (IQR: 2.71-10.50%; 90% CI: 0.43-17.04%) for deflation, across all data sets and PEEP values (N=34predictions). This minimal model thus provides a clinically useful and relatively simple platform for continuous patient specific monitoring of lung unit recruitment for a patient.
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Affiliation(s)
- Ashwath Sundaresan
- Center for BioEngineering, Department of Mechanical Engineering, University of Canterbury, Private Bag 4800, Christchurch, New Zealand.
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LaFollette R, Hojnowski K, Norton J, DiRocco J, Carney D, Nieman G. Using pressure-volume curves to set proper PEEP in acute lung injury. Nurs Crit Care 2007; 12:231-41. [PMID: 17883616 DOI: 10.1111/j.1478-5153.2007.00224.x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The evolution of respiratory care on patients with acute respiratory distress syndrome (ARDS) has been focused on preventing the deleterious effects of mechanical ventilation, termed ventilator-induced lung injury (VILI). Currently, reduced tidal volume is the standard of ventilatory care for patients with ARDS. The current focus, however, has shifted to the proper setting of positive end-expiratory pressure (PEEP). The whole lung pressure-volume (P/V) curve has been used to individualize setting proper PEEP in patients with ARDS, although the physiologic interpretation of the curve remains under debate. The purpose of this review is to present the pros and cons of using P/V curves to set PEEP in patients with ARDS. A systematic analysis of recent and relevant literature was conducted. It has been hypothesized that proper PEEP can be determined by identifying P/V curve inflection points. Acquiring a dynamic curve presents the key to the curve's bedside application. The lower inflection point of the inflation limb has been shown to be the point of massive alveolar recruitment and therefore an option for setting PEEP. However, it is becoming widely accepted that the upper inflection point (UIP) of the deflation limb of the P/V curve represents the point of optimal PEEP. New methods used to identify optimal PEEP, including tomography and active compliance measurements, are currently being investigated. In conclusion, we believe that the most promising method for determining proper PEEP settings is use of the UIP of the deflation limb. However, tomography and dynamic compliance may offer superior bedside availability.
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Yuta T, Chase JG, Shaw GM, Hann C. Dynamic models of ARDS lung mechanics for optimal patient ventilation. CONFERENCE PROCEEDINGS : ... ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL CONFERENCE 2007; 2004:861-4. [PMID: 17271813 DOI: 10.1109/iembs.2004.1403294] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/13/2023]
Abstract
Mechanical ventilation is often used to treat patients with acute respiratory distress syndrome (ARDS). However, the optimal setting is still controversial, and physicians often rely on experience and intuition. The purpose of this research is to develop a model of the essential lung mechanics to help determining the optimal ventilator setting in clinical situations. The model is a compilation of physiologically based mechanics parameters, which are adjustable to represent patient specific conditions. Further investigation improvements are required, however it shows good initial for eventual clinical use.
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Affiliation(s)
- T Yuta
- Dept. of Mech. Eng., Canterbury Univ., Christchurch, New Zealand
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15
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Jonson B. Elastic pressure-volume curves in acute lung injury and acute respiratory distress syndrome. Intensive Care Med 2004; 31:205-12. [PMID: 15605228 DOI: 10.1007/s00134-004-2517-9] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2004] [Accepted: 11/08/2004] [Indexed: 10/26/2022]
Abstract
BACKGROUND The principal features of elastic pressure-volume curves of lungs or the respiratory system (P(el)/V curves) recorded during reexpansion of collapsed lungs and subsequent deflation have been known since the 1950s. In acute respiratory failure and acute respiratory distress syndrome such curves have recently attracted increasing interest because new knowledge can be acquired from them, and because such curves may be useful as guidelines in setting the ventilator so as to avoid ventilator-induced lung injury. DISCUSSION This article reviews recording methods, underlying physiology and utility of P(el)/V curves in research and clinical work.
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Affiliation(s)
- Björn Jonson
- Department of Clinical Physiology, University Hospital of Lund, 22185 Lund, Sweden.
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Hantos Z, Tolnai J, Asztalos T, Peták F, Adamicza A, Alencar AM, Majumdar A, Suki B. Acoustic evidence of airway opening during recruitment in excised dog lungs. J Appl Physiol (1985) 2004; 97:592-8. [PMID: 15090488 DOI: 10.1152/japplphysiol.01402.2003] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The aim of this study was to test the hypothesis that the mechanism of recruitment and the lower knee of the pressure-volume curve in the normal lung are primarily determined by airway reopenings via avalanches rather than simple alveolar recruitments. In isolated dog lung lobes, the pressure-volume loops were measured, and crackle sounds were recorded intrabronchially during both the first inflation from the collapsed state to total lobe capacity and a second inflation without prior degassing. The inflation flow contained transients that were accompanied by a series of crackles. Discrete volume increments were estimated from the flow transients, and the energy levels of the corresponding crackles were calculated from the sound recordings. Crackles were concentrated in the early phase of inflation, with the cumulative energy exceeding 90% of its final value by the lower knee of the pressure-volume curve. The values of volume increments were correlated with crackle energy during the flow transient for both the first and the second inflations ( r2 = 0.29–0.73 and 0.68–0.82, respectively). Because the distribution of volume increments followed a power law, the correlation between crackle energy and discrete volume increments suggests that an avalanche-like airway opening process governs the recruitment of collapsed normal lungs.
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Affiliation(s)
- Z Hantos
- Department of Medical Informatics, University of Szeged, Korányi fasor 9, H-6720 Szeged, Hungary.
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Sorkness RL, Tuffaha A. Contribution of airway closure to chronic postbronchiolitis airway dysfunction in rats. J Appl Physiol (1985) 2004; 96:904-10. [PMID: 14594863 DOI: 10.1152/japplphysiol.00674.2003] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Genetically susceptible Brown Norway rats develop a chronic asthmalike syndrome after recovering from viral bronchiolitis at an early age. We hypothesized that airway closure is an important mechanism of airflow obstruction in postbronchiolitis rats. Rats were studied 8–12 wk after inoculation with Sendai virus or sterile vehicle at 3–4 wk of age. Under light pentobarbital anesthesia, rats were instrumented with an orotracheal catheter and an esophageal pressure monitor and placed in a total body plethysmograph. Lung volumes and forced-expiratory maneuvers were measured using the Boyle's law method and software-controlled valving of positive and negative pressures to elicit lung inflations and rapid deflations; pulmonary resistance was measured during spontaneous tidal breathing; and quasi-static pressure-volume curves were obtained with passive inflations and deflations in fully anesthetized, paralyzed rats. Compared with controls, the postbronchiolitis rats had elevated pulmonary resistance and reduced forced-expiratory volume in 0.2 s. Most of the reduced forced-expiratory volume in 0.2 s was associated with reduced forced vital capacity, indicating premature airway closure as a prominent mechanism. The reduced airflow in postbronchiolitis rats was highly dependent on lung volume, being nearly normal at 70% lung capacity, but sevenfold less than normal at 30% lung capacity. Increased respiratory system hysteresis between functional reserve capacity and total lung capacity was evidence for increased airway closure at normal end-expiratory lung volumes in postbronchiolitis rats. We conclude that airway instability and closure is a prominent mechanism of the chronic airway dysfunction in rats that have recovered from viral bronchiolitis at an early age.
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Affiliation(s)
- Ronald L Sorkness
- Department of Medicine, Morris Institute for Respiratory Research, School of Pharmacy, University of Wisconsin, Madison 53792, USA.
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18
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Bates JHT, Irvin CG. Time dependence of recruitment and derecruitment in the lung: a theoretical model. J Appl Physiol (1985) 2002; 93:705-13. [PMID: 12133882 DOI: 10.1152/japplphysiol.01274.2001] [Citation(s) in RCA: 92] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Recruitment and derecruitment (R/D) of air spaces within the lung is greatly enhanced in lung injury and is thought to be responsible for exacerbating injury during mechanical ventilation. There is evidence to suggest that R/D is a time-dependent phenomenon. We have developed a computer model of the lung consisting of a parallel arrangement of airways and alveolar units. Each airway has a critical pressure (Pcrit) above which it tends to open and below which it tends to close but at a rate determined by how far pressure is from Pcrit. With an appropriate distribution of Pcrit and R/D velocity characteristics, the model able to produce realistic first and second pressure-volume curves of a lung inflated from an initially degassed state. The model also predicts that lung elastance will increase transiently after a deep inflation to a degree that increases as lung volume decreases and as the lung becomes injured. We conclude that our model captures the time-dependent mechanical behavior of the lung due to gradual R/D of lung units.
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Affiliation(s)
- Jason H T Bates
- Vermont Lung Center, Department of Medicine, University of Vermont, Burlington, Vermont 05446, USA.
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Srinivasan G, Bruce EN, Houtz PK, Bruce MC. Dexamethasone-induced changes in lung function are not prevented by concomitant treatment with retinoic acid. Am J Physiol Lung Cell Mol Physiol 2002; 283:L275-87. [PMID: 12114188 DOI: 10.1152/ajplung.00423.2001] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Alveolarization is impaired in rats treated with dexamethasone (Dex) on postnatal days 4-13, but concomitant treatment with all-trans retinoic acid (RA) increases alveolar number. To determine whether morphological changes induced by Dex and/or RA predict changes in lung function at 1 mo, we assessed resting breathing parameters, dynamic compliance, ventilation required to maintain O(2) saturation at > or = 90%, and pressure-volume curves of air-filled lungs. During resting breathing, mean tidal volume per gram was greater in Dex + RA-treated rats than in controls (P < 0.05). Dynamic compliance was also greater in Dex- and Dex + RA-treated rats than in controls or RA-treated rats (P < 0.02). In Dex- and Dex + RA-treated rats, we observed increased hysteresis ratios (P < or = 0.006), air trapping (P < 0.05), and lung volumes at 5 and 13.5 cmH(2)O pressure (P < 0.001) and decreased elastic recoil (P < 0.007). The effect of Dex on elastic recoil was greater in female than in male rats (P = 0.006). Despite impaired septation, O(2) saturation was not compromised in Dex- or Dex + RA-treated rats. Thus lung function changes induced by Dex treatment during alveolarization were not prevented by concomitant treatment with RA.
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Affiliation(s)
- Ganesh Srinivasan
- Department of Pediatrics, University of Kentucky Medical School, Lexington, Kentucky 40536, USA
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Valoración morfométrica de pulmones de rata insuflados con líquido fijador a diferentes presiones próximas a la capacidad pulmonar total. Arch Bronconeumol 2000. [DOI: 10.1016/s0300-2896(15)30125-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
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Cheng W, DeLong DS, Franz GN, Petsonk EL, Frazer DG. Discountinuous lung sounds and hysteresis in control and Tween 20-rinsed excised rat lungs. RESPIRATION PHYSIOLOGY 1999; 117:131-40. [PMID: 10563441 DOI: 10.1016/s0034-5687(99)00048-1] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/16/2022]
Abstract
In the past, the relationship between pulmonary hysteresis and a model of the recruitment-derecruitment of lung units has been explored (Cheng, W., DeLong, D.S., Franz, G.N., Petsonk, E.L., Frazer, D.G., 1995, Resp. Physiol. 102, 205-215). The recruitment process is characterized by a sequence of events which represents discrete configurational changes in lung structure. It is assumed that energy released during the opening of lung units is associated with the formation of discontinuous lung sounds. The goal of this study was to record tracheal sounds for lungs inflated from different end-expiratory pressures and to relate the sound power to the normalized hysteresis of individual pressure-volume (PL-VL) loops. PL-VL curves and lung sounds were recorded for control lungs and lungs rinsed with Tween 20 in order to estimate the role of alveolar surfactant on the recruitment-derecruitment process. Results indicate that there may be two populations of lung units, one which is altered by Tween 20 and another which is not. The population not affected by Tween 20 appears to be responsible for producing discrete lung sounds and may represent the opening of larger conducting airways. The second population, possibly within the respiratory zone, is affected by alterations in surface tension and contributes to pulmonary hysteresis, but, apparently, does not contribute significantly to lung sound power measured at the trachea.
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Affiliation(s)
- W Cheng
- Department of Physiology, West Virginia University School of Medicine, Morgantown 26506-2888, USA
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Jones TA, Petsonk EL, Frazer DG. Effect of temperature on pressure-volume hysteresis of excised lungs. RESPIRATION PHYSIOLOGY 1996; 106:47-55. [PMID: 8946576 DOI: 10.1016/0034-5687(96)00041-2] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
The objective of this study was to determine if the effect of temperature on excised lung pressure-volume (P-V) hysteresis during various P-V maneuvers would be consistent with predicted effects based on the recruitment-derecruitment (R-D) model of lung P-V hysteresis. Three sets of P-V curves were recorded for excised rat lungs at (1) 24 degrees C, (2) either 42 degrees or 45 degrees C, and (3) 24 degrees C. After full inflation of the lung, deflation-inflation (D-I) cycles were performed between total lung capacity (30 cmH2O) and successively decreasing end-expiratory pressures (EEPs). Normalized hysteresis (K) was plotted vs EEP. K remained relatively constant at EEPs > or = +5 cmH2O at 24 degrees C and 42 degrees C and > +5 cmH2O at 45 degrees C. Large increases in K occurred as the EEP was further reduced, with the relationship of K vs EEP being shifted to the right at 42 degrees C and 45 degrees C relative to 24 degrees C, with the greater shift occurring at 45 degrees C. Previous work has shown that the R-D of lung units contributes to P-V hysteresis and is EEP-dependent, increasing at EEPs < or = +4 +/- 1 cmH2O at room temperature (Cheng et al., 1995). This study suggests that at increased temperatures, R-D of lung units is initiated at higher EEPs and is more extensive than at room temperature.
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Affiliation(s)
- T A Jones
- Department of Surgery, Easton Hospital, PA 18042, USA
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