Expiratory time constants in mechanically ventilated patients with and without COPD

Lourens, M. S.; Berg, Benno van den; Aerts, Joachim; Verbraak, A. F. M.; Hoogsteden, Henk C.; Bogaard, J. M.

doi:10.1007/s001340000632

Cited by 61 publications

(62 citation statements)

References 20 publications

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“…The target VT/RR combination is based on the equation by OTIS et al [19], which determines an RR that minimises work of inspiration for a clinician-set minute volume, based on the time constant of the respiratory system. The time constant is estimated on a breath-by-breath basis by the expiratory time constant (RCexp) obtained from the expiratory flow-volume curve [20,21].…”

Section: Patientsmentioning

confidence: 99%

Adaptive support ventilation for faster weaning in COPD: a randomised controlled trial

et al. 2011

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Adaptive support ventilation (ASV) is a closed-loop ventilation mode that can act both as pressure support ventilation (PSV) and pressure-controlled ventilation. Weaning with ASV shows promising results, mainly in post-cardiac surgery patients. The aim of the present randomised controlled study was to test the hypothesis that weaning with ASV could reduce the weaning duration in patients with chronic obstructive pulmonary disease (COPD) when compared with PSV.From among 435 COPD patients admitted to the intensive care unit (ICU) during a 20-month period, 97 were enrolled. Patients were assigned at random to either ASV or PSV as a weaning mode.Compared with PSV, ASV provided shorter weaning times (median 24 (interquartile range 20-62) h versus 72 (24-144) h, p50.041) with similar weaning success rates (35 out of 49 for ASV and 33 out of 48 for PSV). Length of stay in the ICU was also shorter with ASV but the difference was not statistically significant.This study suggests that ASV may be used in the weaning of COPD patients with the advantage of shorter weaning times. Further studies are needed to investigate the role and potential advantages of ASV in the weaning period of different patient groups.

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Section: Patientsmentioning

confidence: 99%

Adaptive support ventilation for faster weaning in COPD: a randomised controlled trial

et al. 2011

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“…The time constant is estimated on a breath-by-breath basis by the expiratory time constant (RCexp) obtained from the expiratory flow-volume curve. (30,31) Weaning protocols After randomisation, the BiPAP (Duo PAP) mode was stopped and the two weaning modes (ASV and PSV) were allocated randomly using sealed envelopes. Weaning and extubation were performed by the critical care physicians who were working in the ICU.…”

Section: Materials and Methods Patientsmentioning

confidence: 99%

A Randomized Controlled Trial to Compare Adaptive Support Ventilation and Pressure Support Ventilation for Weaning COPD Patients

Am¹

2016

jmscr

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“…14,22,23 This model consists of a single flow unit with a constant resistance, in series with a single elastic unit of constant compliance. 16 However, there are significant differences in the time constant when it is measured at different lung volumes in subjects with lung disease.…”

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confidence: 99%

“…16 However, there are significant differences in the time constant when it is measured at different lung volumes in subjects with lung disease. [22][23][24] Specifically, in patients with the acute respiratory distress syndrome and those with COPD, the time constant increases as expiration proceeds. 22,23 Notably, a single compartment cannot accurately describe passive expiration in intubated and paralyzed patients.…”

mentioning

confidence: 99%

“…[22][23][24] Specifically, in patients with the acute respiratory distress syndrome and those with COPD, the time constant increases as expiration proceeds. 22,23 Notably, a single compartment cannot accurately describe passive expiration in intubated and paralyzed patients. 25 However, our patients were in a stable state in the outpatient setting, as opposed to intubated under conditions of respiratory failure, 14,23 or paralysis.…”

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confidence: 99%

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Expiratory Time Constant and Sleep Apnea Severity in the Overlap Syndrome

Wiriyaporn

Wang

Aboussouan

2016

Journal of Clinical Sleep Medicine

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Study Objectives: Lung mechanics in the overlap of COPD and sleep apnea impact the severity of sleep apnea. Specifically, increased lung compliance with hyperinflation protects against sleep apnea, whereas increased airway resistance worsens sleep apnea. We sought to assess whether the expiratory time constant, which reflects lung mechanics, is associated with sleep apnea severity in such patients. Methods: Polysomnographies in 34 subjects with the overlap syndrome were reviewed. Three time constants were measured for each of up to 5 stages (wake, NREM stages, and REM). The time constants were derived by fitting time and pressure coordinates on the expiratory portion of a nasal pressure signal along an exponentially decaying equation, and solving for the time constant. Demographics, morphometrics, wake end-tidal CO 2 , right diaphragmatic arc on a chest radiograph, and the apnea-hypopnea index (AHI) were recorded. Results: The time constant was not associated with age, gender, body mass index, right diaphragmatic arc, or wake end-tidal CO 2 , and was not significantly different between sleep stages. A mean time constant (TC) was therefore obtained. Subjects with a TC > 0.5 seconds had a greater AHI than those with a TC ≤ 0.5 seconds (median AHI 58 vs. 18, respectively, p = 0.003; Odds ratio of severe sleep apnea 10.6, 95% CI 3.9-51.1, p = 0.005). Conclusions: A larger time constant in the overlap syndrome is associated with increased odds of severe sleep apnea, suggesting a greater importance of airway resistance relative to lung compliance in sleep apnea causation in these subjects.

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Expiratory time constants in mechanically ventilated patients with and without COPD

Abstract: In mechanically ventilated patients with and without COPD, a time constant can well be calculated from the expiratory flow-volume curve for the last 75% of tidal volume, gives a good estimation of respiratory mechanics, and is easy to obtain at the bedside.

Cited by 61 publications

References 20 publications

Adaptive support ventilation for faster weaning in COPD: a randomised controlled trial

Adaptive support ventilation for faster weaning in COPD: a randomised controlled trial

A Randomized Controlled Trial to Compare Adaptive Support Ventilation and Pressure Support Ventilation for Weaning COPD Patients

Expiratory Time Constant and Sleep Apnea Severity in the Overlap Syndrome

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