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Cruz AF, Herrmann J, Carvalho CRR, Kaczka DW. A comparison of endotracheal tube compensation techniques for the measurement of respiratory mechanical impedance at low frequencies. J Clin Monit Comput 2022; 36:1461-1477. [PMID: 34910285 PMCID: PMC9198108 DOI: 10.1007/s10877-021-00788-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2021] [Accepted: 12/01/2021] [Indexed: 11/29/2022]
Abstract
Measurement of respiratory impedance ([Formula: see text]) in intubated patients requires accurate compensation for pressure losses across the endotracheal tube (ETT). In this study, we compared time-domain (TD), frequency-domain (FD) and combined time-/frequency-domain (FT) methods for ETT compensation. We measured total impedance ([Formula: see text]) of a test lung in series with three different ETT sizes, as well as in three intubated porcine subjects. Pressure measurement at the distal end of the ETT was used to determine the true [Formula: see text]. For TD compensation, pressure distal to the ETT was obtained based on its resistive and inertial properties, and the corresponding [Formula: see text] was estimated. For FD compensation, impedance of the isolated ETT was obtained from oscillatory flow and pressure waveforms, and then subtracted from [Formula: see text]. For TF compensation, the nonlinear resistive properties of the ETT were subtracted from the proximal pressure measurement, from which the linear resistive and inertial ETT properties were removed in the frequency-domain to obtain [Formula: see text]. The relative root mean square error between the actual and estimated [Formula: see text] ([Formula: see text]) showed that TD compensation yielded the least accurate estimates of [Formula: see text] for the in vitro experiments, with small deviations observed at higher frequencies. The FD and TF compensations yielded estimates of [Formula: see text] with similar accuracies. For the porcine subjects, no significant differences were observed in [Formula: see text] across compensation methods. FD and TF compensation of the ETT may allow for accurate oscillometric estimates of [Formula: see text] in intubated subjects, while avoiding the difficulties associated with direct tracheal pressure measurement.
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Affiliation(s)
- Andrea F Cruz
- Laboratorio de Pneumologia LIM-09, Disciplina de Pneumologia, Heart Institute (Incor), Hospital das Clinicas da Faculdade de Medicina da Universidade de São Paulo, São Paulo, São Paulo, Brazil
- Department of Anesthesia, University of Iowa, Iowa City, IA, USA
| | - Jacob Herrmann
- Department of Anesthesia, University of Iowa, Iowa City, IA, USA
- Roy J. Carver Department of Biomedical Engineering, University of Iowa, Iowa City, IA, USA
| | - Carlos R R Carvalho
- Laboratorio de Pneumologia LIM-09, Disciplina de Pneumologia, Heart Institute (Incor), Hospital das Clinicas da Faculdade de Medicina da Universidade de São Paulo, São Paulo, São Paulo, Brazil
| | - David W Kaczka
- Department of Anesthesia, University of Iowa, Iowa City, IA, USA.
- Roy J. Carver Department of Biomedical Engineering, University of Iowa, Iowa City, IA, USA.
- Department of Radiology, University of Iowa, Iowa City, IA, USA.
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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.
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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
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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.
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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.
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