1
|
Miller AG, Bartle RM, Feldman A, Mallory P, Reyes E, Scott B, Rotta AT. A narrative review of advanced ventilator modes in the pediatric intensive care unit. Transl Pediatr 2021; 10:2700-2719. [PMID: 34765495 PMCID: PMC8578787 DOI: 10.21037/tp-20-332] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/13/2020] [Accepted: 11/26/2020] [Indexed: 01/29/2023] Open
Abstract
Respiratory failure is a common reason for pediatric intensive care unit admission. The vast majority of children requiring mechanical ventilation can be supported with conventional mechanical ventilation (CMV) but certain cases with refractory hypoxemia or hypercapnia may require more advanced modes of ventilation. This paper discusses what we have learned about the use of advanced ventilator modes [e.g., high-frequency oscillatory ventilation (HFOV), high-frequency percussive ventilation (HFPV), high-frequency jet ventilation (HFJV) airway pressure release ventilation (APRV), and neurally adjusted ventilatory assist (NAVA)] from clinical, animal, and bench studies. The evidence supporting advanced ventilator modes is weak and consists of largely of single center case series, although a few RCTs have been performed. Animal and bench models illustrate the complexities of different modes and the challenges of applying these clinically. Some modes are proprietary to certain ventilators, are expensive, or may only be available at well-resourced centers. Future efforts should include large, multicenter observational, interventional, or adaptive design trials of different rescue modes (e.g., PROSpect trial), evaluate their use during ECMO, and should incorporate assessments through volumetric capnography, electric impedance tomography, and transpulmonary pressure measurements, along with precise reporting of ventilator parameters and physiologic variables.
Collapse
Affiliation(s)
- Andrew G Miller
- Duke University Medical Center, Durham, NC, USA.,Respiratory Care Services, Duke University Medical Center, Durham, NC, USA
| | - Renee M Bartle
- Duke University Medical Center, Durham, NC, USA.,Respiratory Care Services, Duke University Medical Center, Durham, NC, USA
| | - Alexandra Feldman
- Duke University Medical Center, Durham, NC, USA.,Division of Pediatric Critical Care Medicine, Duke University Medical Center, Durham, NC, USA
| | - Palen Mallory
- Duke University Medical Center, Durham, NC, USA.,Division of Pediatric Critical Care Medicine, Duke University Medical Center, Durham, NC, USA
| | - Edith Reyes
- Duke University Medical Center, Durham, NC, USA.,Division of Pediatric Critical Care Medicine, Duke University Medical Center, Durham, NC, USA
| | - Briana Scott
- Duke University Medical Center, Durham, NC, USA.,Division of Pediatric Critical Care Medicine, Duke University Medical Center, Durham, NC, USA
| | - Alexandre T Rotta
- Duke University Medical Center, Durham, NC, USA.,Division of Pediatric Critical Care Medicine, Duke University Medical Center, Durham, NC, USA
| |
Collapse
|
2
|
Lucangelo U, Ajčević M, Lena E, Ferluga M, Comuzzi L, Accardo A, Zin WA. On some factors determining the pressure drop across tracheal tubes during high-frequency percussive ventilation: a flow-independent model. J Clin Monit Comput 2020; 35:885-890. [PMID: 32588314 PMCID: PMC7316425 DOI: 10.1007/s10877-020-00548-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2020] [Accepted: 06/11/2020] [Indexed: 11/29/2022]
Abstract
To provide an in vitro estimation of the pressure drop across tracheal tubes (ΔPTT) in the face of given pulsatile frequencies and peak pressures (Pwork) delivered by a high-frequency percussive ventilator (HFPV) applied to a lung model. Tracheal tubes (TT) 6.5, 7.5 and 8.0 were connected to a test lung simulating the respiratory system resistive (R = 5, 20, 50 cmH2O/L/s) and elastic (C = 10, 20, and 50 mL/cmH2O) loads. The model was ventilated by HFPV with a pulse inspiratory peak pressure (work pressure Pwork) augmented in 5-cmH2O steps from 20 to 45 cmH2O, yielding 6 diverse airflows. The percussive frequency (f) was set to 300, 500 and 700 cycles/min, respectively. Pressure (Paw and Ptr) and flow (V’) measurements were performed for all 162 possible combinations of loads, frequencies, and work pressures for each TT size, thus yielding 486 determinations. For each respiratory cycle ΔPTT was calculated by subtracting each peak Ptr from its corresponding peak Paw. A non-linear model was constructed to assess the relationships between single parameters. Performance of the produced model was measured in terms of root mean square error (RMSE) and the coefficient of determination (r2). ΔPTT was predicted by Pwork (exponential Gaussian relationship), resistance (quadratic and linear terms), frequency (quadratic and linear terms) and tube diameter (linear term), but not by compliance. RMSE of the model on the testing dataset was 1.17 cmH2O, r2 was 0.79 and estimation error was lower than 1 cmH2O in 68% of cases. As a result, even without a flow value, the physician would be able to evaluate ΔPTT pressure. If the present results of our bench study could be clinically confirmed, the use of a nonconventional ventilatory strategy as HFPV, would be safer and easier.
Collapse
Affiliation(s)
- Umberto Lucangelo
- Department of Perioperative Medicine, Intensive Care and Emergency, University of Trieste, Trieste, Italy
| | - Miloš Ajčević
- Department of Engineering and Architecture, University of Trieste, Trieste, Italy.
| | - Enrico Lena
- Department of Perioperative Medicine, Intensive Care and Emergency, University of Trieste, Trieste, Italy
| | - Massimo Ferluga
- Department of Perioperative Medicine, Intensive Care and Emergency, University of Trieste, Trieste, Italy
| | - Lucia Comuzzi
- Department of Perioperative Medicine, Intensive Care and Emergency, University of Trieste, Trieste, Italy
| | - Agostino Accardo
- Department of Engineering and Architecture, University of Trieste, Trieste, Italy
| | - Walter A Zin
- Carlos Chagas Filho Institute of Biophysics, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil
| |
Collapse
|
3
|
Dutta R, Xing T, Murdoch GK. Comparison of pressure, volume and gas washout characteristics between PCV and HFPV in healthy and formalin fixed ex vivo porcine lungs. Physiol Meas 2018; 39:095003. [PMID: 30109993 DOI: 10.1088/1361-6579/aada73] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
OBJECTIVE This study employs a recently developed experimental technique for comparison of the flow characteristics and the effectiveness of gas washout between pressure control ventilation (PCV) and high-frequency percussive ventilation (HFPV) in high-compliance and low-compliance ex vivo porcine respiratory tracts. APPROACH The ex vivo porcine lungs are filled with nitrogen prior to ventilating with atmospheric gas using either PCV or HFPV to investigate the flow characteristics and gas washout characteristics. The study considered freshly removed lungs from porcine carcasses that were humanely harvested for human consumption. Subsequently, the porcine lungs were exposed externally to formalin to simulate low-compliance conditions. The first order models of respiratory mechanics were employed to predict the lung compliance and resistance in normal and formalin exposed lungs. HFPV was operated in two different modes based upon the set pressures, namely HFPV-Low and HFPV-High. The peak pressures of HFPV and PCV were matched in HFPV-Low and the peak pressures are increased to about 20-30% in the HFPV-High mode. MAIN RESULTS Both HFPV-Low and HFPV-High mode deliver smaller tidal volume (V T) as compared to PCV in high and compliance states (about 70% and 40% for healthy and formalin treated lungs, repsectively). Although the tidal volume delivered by HFPV-High and HFPV-Low are comparable, they reveal a substantial difference in washout time as well as total ventilation volumes. In a high compliant lung (healthy lung), HFPV-High washes out the nitrogen within the lung more rapidly, whereas HFPV-Low washes out the inert gas more slowly as compared to PCV. In a low-compliance lung, HFPV-Low delivers similar washout rates as PCV at a much smaller V T and lower mean airway pressure. SIGNIFICANCE The ex vivo study supports the hypothesis that in low compliant lungs HFPV provides effective washout with a protective ventilation.
Collapse
Affiliation(s)
- Rabijit Dutta
- Department of Mechanical Engineering, University of Idaho, Moscow, ID, United States of America
| | | | | |
Collapse
|
4
|
Dutta R, Xing T, Swanson C, Heltborg J, Murdoch GK. Comparison of flow and gas washout characteristics between pressure control and high-frequency percussive ventilation using a test lung. Physiol Meas 2018; 39:035001. [PMID: 29369819 PMCID: PMC5870834 DOI: 10.1088/1361-6579/aaaaa2] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
OBJECTIVE A comparison between flow and gas washout data for high-frequency percussive ventilation (HFPV) and pressure control ventilation (PCV) under similar conditions is currently not available. This bench study aims to compare and describe the flow and gas washout behavior of HFPV and PCV in a newly designed experimental setup and establish a framework for future clinical and animal studies. APPROACH We studied gas washout behavior using a newly designed experimental setup that is motivated by the multi-breath nitrogen washout measurements. In this procedure, a test lung was filled with nitrogen gas before it was connected to a ventilator. Pressure, volume, and oxygen concentrations were recorded under different compliance and resistance conditions. PCV was compared with two settings of HFPV, namely, HFPV-High and HFPV-Low, to simulate the different variations in its clinical application. In the HFPV-Low mode, the peak pressures and drive pressures of HFPV and PCV are matched, whereas in the HFPV-High mode, the mean airway pressures (MAP) are matched. MAIN RESULTS HFPV-Low mode delivers smaller tidal volume (V T) as compared to PCV under all lung conditions, whereas HFPV-High delivers a larger V T. HFPV-High provides rapid washout as compared to PCV under all lung conditions. HFPV-Low takes a longer time to wash out nitrogen except at a low compliance, where it expedites washout at a smaller V T and MAP compared to PCV washout. SIGNIFICANCE Various flow parameters for HFPV and PCV are mathematically defined. A shorter washout time at a small V T in low compliant test lungs for HFPV could be regarded as a hypothesis for lung protective ventilation for animal or human lungs.
Collapse
Affiliation(s)
- Rabijit Dutta
- Department of Mechanical Engineering, University of Idaho, Moscow, ID, United States of America
| | | | | | | | | |
Collapse
|
5
|
Godet T, Jabaudon M, Blondonnet R, Tremblay A, Audard J, Rieu B, Pereira B, Garcier JM, Futier E, Constantin JM. High frequency percussive ventilation increases alveolar recruitment in early acute respiratory distress syndrome: an experimental, physiological and CT scan study. CRITICAL CARE : THE OFFICIAL JOURNAL OF THE CRITICAL CARE FORUM 2018; 22:3. [PMID: 29325586 PMCID: PMC5763966 DOI: 10.1186/s13054-017-1924-6] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/29/2017] [Accepted: 12/13/2017] [Indexed: 01/27/2023]
Abstract
Background High frequency percussive ventilation (HFPV) combines diffusive (high frequency mini-bursts) and convective ventilation patterns. Benefits include enhanced oxygenation and hemodynamics, and alveolar recruitment, while providing hypothetic lung-protective ventilation. No study has investigated HFPV-induced changes in lung aeration in patients with early acute respiratory distress syndrome (ARDS). Methods Eight patients with early non-focal ARDS were enrolled and five swine with early non-focal ARDS were studied in prospective computed tomography (CT) scan and animal studies, in a university-hospital tertiary ICU and an animal laboratory. Patients were optimized under conventional “open-lung” ventilation. Lung CT was performed using an end-expiratory hold (Conv) to assess lung morphology. HFPV was applied for 1 hour to all patients before new CT scans were performed with end-expiratory (HFPV EE) and end-inspiratory (HFPV EI) holds. Lung volumes were determined after software analysis. At specified time points, blood gases and hemodynamic data were collected. Recruitment was defined as a change in non-aerated lung volumes between Conv, HFPV EE and HFPV EI. The main objective was to verify whether HFPV increases alveolar recruitment without lung hyperinflation. Correlation between pleural, upper airways and HFPV-derived pressures was assessed in an ARDS swine-based model. Results One-hour HFPV significantly improved oxygenation and hemodynamics. Lung recruitment significantly rose by 12.0% (8.5–18.0%), P = 0.05 (Conv-HFPV EE) and 12.5% (9.3–16.8%), P = 0.003 (Conv-HFPV EI). Hyperinflation tended to increase by 2.0% (0.5–2.5%), P = 0.89 (Conv-HFPV EE) and 3.0% (2.5–4.0%), P = 0.27 (Conv-HFPV EI). HFPV hyperinflation correlated with hyperinflated and normally-aerated lung volumes at baseline: r = 0.79, P = 0.05 and r = 0.79, P = 0.05, respectively (Conv-HFPV EE); and only hyperinflated lung volumes at baseline: r = 0.88, P = 0.01 (Conv-HFPV EI). HFPV CT-determined tidal volumes reached 5.7 (1.1–8.1) mL.kg-1 of ideal body weight (IBW). Correlations between pleural and HFPV-monitored pressures were acceptable and end-inspiratory pleural pressures remained below 25cmH20. Conclusions HFPV improves alveolar recruitment, gas exchanges and hemodynamics of patients with early non-focal ARDS without relevant hyperinflation. HFPV-derived pressures correlate with corresponding pleural or upper airways pressures. Trial registration ClinicalTrials.gov, NCT02510105. Registered on 1 June 2015. The trial was retrospectively registered. Electronic supplementary material The online version of this article (doi:10.1186/s13054-017-1924-6) contains supplementary material, which is available to authorized users.
Collapse
Affiliation(s)
- Thomas Godet
- Departement de Médecine Périopératoire (MPO), Hôpital Estaing, Centre Hospitalier Universitaire (CHU) Clermont-Ferrand, 1 place Lucie Aubrac, Clermont-Ferrand, F-63003, France.,Université Clermont Auvergne, Laboratoire Universitaire GReD, UMR/CNRS 6293, INSERM U1103, Clermont-Ferrand, F-63003, France
| | - Matthieu Jabaudon
- Departement de Médecine Périopératoire (MPO), Hôpital Estaing, Centre Hospitalier Universitaire (CHU) Clermont-Ferrand, 1 place Lucie Aubrac, Clermont-Ferrand, F-63003, France.,Université Clermont Auvergne, Laboratoire Universitaire GReD, UMR/CNRS 6293, INSERM U1103, Clermont-Ferrand, F-63003, France
| | - Raïko Blondonnet
- Departement de Médecine Périopératoire (MPO), Hôpital Estaing, Centre Hospitalier Universitaire (CHU) Clermont-Ferrand, 1 place Lucie Aubrac, Clermont-Ferrand, F-63003, France.,Université Clermont Auvergne, Laboratoire Universitaire GReD, UMR/CNRS 6293, INSERM U1103, Clermont-Ferrand, F-63003, France
| | - Aymeric Tremblay
- Département d'Anesthésie et de Réanimation, Centre Hospitalier Universitaire (CHU) Saint-Etienne, Saint-Etienne, F-42000, France
| | - Jules Audard
- Departement de Médecine Périopératoire (MPO), Hôpital Estaing, Centre Hospitalier Universitaire (CHU) Clermont-Ferrand, 1 place Lucie Aubrac, Clermont-Ferrand, F-63003, France.,Université Clermont Auvergne, Laboratoire Universitaire GReD, UMR/CNRS 6293, INSERM U1103, Clermont-Ferrand, F-63003, France
| | - Benjamin Rieu
- Departement de Médecine Périopératoire (MPO), Hôpital Estaing, Centre Hospitalier Universitaire (CHU) Clermont-Ferrand, 1 place Lucie Aubrac, Clermont-Ferrand, F-63003, France
| | - Bruno Pereira
- Délégation à la Recherche Clinique et à l'Innovation (DRCI), Centre Hospitalier Universitaire (CHU) Clermont-Ferrand, Clermont-Ferrand, F-63000, France
| | - Jean-Marc Garcier
- Département de Radiologie, Centre Hospitalier Universitaire (CHU) Clermont-Ferrand, Clermont-Ferrand, F-63003, France
| | - Emmanuel Futier
- Departement de Médecine Périopératoire (MPO), Hôpital Estaing, Centre Hospitalier Universitaire (CHU) Clermont-Ferrand, 1 place Lucie Aubrac, Clermont-Ferrand, F-63003, France.,Université Clermont Auvergne, Laboratoire Universitaire GReD, UMR/CNRS 6293, INSERM U1103, Clermont-Ferrand, F-63003, France
| | - Jean-Michel Constantin
- Departement de Médecine Périopératoire (MPO), Hôpital Estaing, Centre Hospitalier Universitaire (CHU) Clermont-Ferrand, 1 place Lucie Aubrac, Clermont-Ferrand, F-63003, France. .,Université Clermont Auvergne, Laboratoire Universitaire GReD, UMR/CNRS 6293, INSERM U1103, Clermont-Ferrand, F-63003, France.
| |
Collapse
|
6
|
Ajčević M, Lucangelo U, Ferluga M, Zin WA, Accardo A. In vitro estimation of pressure drop across tracheal tubes during high-frequency percussive ventilation. Physiol Meas 2014; 35:177-88. [PMID: 24398394 DOI: 10.1088/0967-3334/35/2/177] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Tracheal tubes (TT) are used in clinical practice to connect an artificial ventilator to the patient's airways. It is important to know the pressure used to overcome tube impedance to avoid lung injury. Although high-frequency percussive ventilation (HFPV) has been increasingly used, the mechanical behavior of TT under HFPV has not yet been described. Thus, we aimed at characterizing in vitro the pressure drop across TT (ΔPTT) by identifying the model that best fits the measured pressure-flow (P-V̇) relationships during HFPV under different working pressures (PWork), percussive frequencies and mechanical loads. Three simple models relating ΔPTT and flow (V̇) were tested. Model 1 is characterized by linear resistive [Rtube ⋅ V̇(t)] and inertial [I · V̈(t)] terms. Model 2 takes into consideration Rohrer's approach [K1· V̇(t) + K2 ⋅V̇(t)] and inertance [I ·V̈(t)]. In model 3 the pressure drop caused by friction is represented by the non-linear Blasius component [Kb· V̇(1.75)(t)] and the inertial term [I· V̈(t)]. Model 1 presented a significantly higher root mean square error of approximation than models 2 and 3, which were similar. Thus, model 1 was not as accurate as the latter, possibly due to turbulence. Model 3 presented the most robust resistance-related coefficient. Estimated inertances did not vary among the models using the same tube. In conclusion, in HFPV ΔPTT can be easily calculated by the physician using model 3.
Collapse
Affiliation(s)
- M Ajčević
- Department of Engineering and Architecture, University of Trieste, Trieste, Italy
| | | | | | | | | |
Collapse
|
7
|
Fornasa E, Ajčević M, Accardo A. Characterization of the mechanical behavior of intrapulmonary percussive ventilation. Physiol Meas 2013; 34:1583-92. [PMID: 24165323 DOI: 10.1088/0967-3334/34/12/1583] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
A new device delivering intrapulmonary percussive ventilation (IPV), called Impulsator® (Percussionaire Corporation, Sandpoint, ID, USA), has recently been introduced in an effort to provide effective clearance and to promote homogeneity of ventilation in the lungs of patients with cystic fibrosis. In order to optimize the treatment based on its use, a better understanding of its functioning is still necessary. In fact, up to now, a complete characterization of this device has not been carried out, thus reducing its effective utilization in clinical practice. With the aim of overcoming this lack, in this study, data concerning flow and pressure delivered during in vitro IPV were acquired under different combinations of device settings and respiratory loads. Quantitative information was obtained about the physical variables administered by the device like percussive frequency, ratio of inspiratory to expiratory time, flow and pressure magnitudes and volume exchanged. The analysis of the data determined the relations among these variables and between them and the mechanical loads, laying the basis for an optimal clinical application of the device.
Collapse
|
8
|
Feltracco P, Serra E, Barbieri S, Milevoj M, Michieletto E, Carollo C, Rea F, Zanus G, Boetto R, Ori C. Noninvasive High-Frequency Percussive Ventilation in the Prone Position after Lung Transplantation. Transplant Proc 2012; 44:2016-21. [DOI: 10.1016/j.transproceed.2012.05.062] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
|
9
|
Dellamonica J, Vargas F. Ventilation à haute fréquence par percussion (VHFP) : des utilisateurs, mais des indications à préciser. Rev Mal Respir 2012; 29:111-3. [DOI: 10.1016/j.rmr.2011.06.019] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2011] [Accepted: 12/15/2011] [Indexed: 11/16/2022]
|
10
|
Riscica F, Lucangelo U, Ferluga M, Accardo A. In vitromeasurements of respiratory mechanics during HFPV using a mechanical lung model. Physiol Meas 2011; 32:637-48. [DOI: 10.1088/0967-3334/32/6/002] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
|
11
|
Lucangelo U, Accardo A, Bernardi A, Ferluga M, Borelli M, Antonaglia V, Riscica F, Zin WA. Gas distribution in a two-compartment model ventilated in high-frequency percussive and pressure-controlled modes. Intensive Care Med 2010; 36:2125-31. [PMID: 20689922 DOI: 10.1007/s00134-010-1993-3] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2009] [Accepted: 06/09/2010] [Indexed: 12/27/2022]
Abstract
PURPOSE To demonstrate in a two-compartment heterogeneous mechanical model of the lung how different loads applied to one compartment, while the other is kept constant, would modify gas distribution between the two pathways under high-frequency percussive ventilation (HFPV). Additionally, these results were compared with those generated in the same model by pressure-controlled ventilation (PCV). METHODS Analysis was based on a Siemens lung simulator, representing a fixed branch of the system with an elastance equal to 45 cmH(2)O/L and a resistance of 20 cmH(2)O/L/s, and a single-compartment lung simulator, representing a variable pathway of the model, presenting three elastic loads varying between 35 and 85 cmH(2)O/L and three resistive loads varying between 5 and 50 cmH(2)O/L/s. Each simulator represented one compartment of the model connected to a central airway that was ventilated with either a volumetric diffusive respirator (VDR-4; Percussionaire Corporation, Sandpoint, ID, USA) or a Siemens Servo 900c ventilator. Flow and pressures were measured in each branch of the model under nine conditions representing the combinations of three elastic and three resistive loads (variable branch) while the loads in the other pathway were kept constant. RESULTS HFPV was able to avoid hyperinflation and reduce tidal volume in a bicompartmental heterogeneous lung model. Under HFPV, gas distribution between the two compartments was not constrained by their time constants. PCV yielded gas distribution as determined by the time constant of each compartment. CONCLUSIONS HFPV accommodated volume distribution without overinflating compartments with low time constants, thus possibly presenting a potential protective behavior in mechanically heterogeneous lungs.
Collapse
Affiliation(s)
- Umberto Lucangelo
- Department of Perioperative Medicine, Intensive Care and Emergency, Cattinara Hospital, Trieste University School of Medicine, Strada di Fiume 447, 34139, Trieste, Italy.
| | | | | | | | | | | | | | | |
Collapse
|