Low-pressure support vs automatic tube compensation during spontaneous breathing trial for weaning

Abstract

BackgroundDuring spontaneous breathing trial, low-pressure support is thought to compensate for endotracheal tube resistance, but it actually should provide overassistance. Automatic tube compensation is an option available in the ventilator to compensate for flow-resistance of endotracheal tube. Its effects on patient effort have been poorly investigated. We aimed to compare the effects of low-pressure support and automatic tube compensation during spontaneous breathing trial on breathing power and lung ventilation distribution.ResultsWe performed a randomized crossover study in 20 patients ready to wean. Each patient received both methods for 30 min separated by baseline ventilation: pressure support 0 cmH2O and automatic tube compensation 100% in one period and pressure support 7 cmH2O without automatic tube compensation in the other period, a 4 cmH2O positive end-expiratory pressure being applied in each. Same ventilator brand (Evita XL, Draeger, Germany) was used. Breathing power was assessed from Campbell diagram with esophageal pressure, airway pressure, flow and volume recorded by a data logger. Lung ventilation distribution was assessed by using electrical impedance tomography (Pulmovista, Draeger, Germany). During the last 2 min of low-pressure support and automatic compensation period breathing power and lung ventilation distribution were measured on each breath. Breathing power generated by the patient’s respiratory muscles was 7.2 (4.4–9.6) and 9.7 (5.7–21.9) J/min in low-pressure support and automatic tube compensation periods, respectively (P = 0.011). Lung ventilation distribution was not different between the two methods.ConclusionsWe found that ATC was associated with higher breathing power than low PS during SBT without altering the distribution of lung ventilation.

Diaphragm dysfunction, lung aeration loss and weaning-induced pulmonary oedema in difficult-to-wean patients

“…The definition of weaning-induced pulmonary oedema used in this study could also explain the high prevalence, as we opted to standardize classification of patients based on objective criteria (echocardiography and/or biomarkers) rather than classify patients based on expert consensus [ 1 , 2 ], which may be subject to bias. We also used a challenging weaning trial that is likely to have markedly influenced the intrathoracic pressure [ 29 ]. In addition, it is likely that the early spontaneous breathing trial strategy relying on the presence of “readiness-to-wean criteria” rather on “readiness to extubate criteria” is partially responsible of the high prevalence of weaning-induced pulmonary oedema observed in our population.…”

A Comprehensive Bench Assessment of Automatic Tube Compensation in ICU Ventilators for Better Clinical Management

“…We set linear compliance and resistance as equal during inspiration and expiration. At the patient effort step of the ASL 5000 script, we used the analog output of the esophageal pressure tracing in a representative subject included in the previously mentioned study comparing pressure support ventilation to ATC 3 (see the supplementary materials at http://www. rcjournal.com).…”

“…We recently reported 3 that breathing power was significantly higher with ATC than with low pressure support ventilation mode, both including a low PEEP, indicating that low pressure support ventilation provides pressure assistance beyond the pressure drop across ETT compensation. 4 Nevertheless, our previous work 3 used one brand of ventilator (Evita XL, Dräger, Germany) with all subjects, and the results may be different from those obtained with other ICU ventilators given that the algorithms governing ATC may differ. To explore this question further, we first performed an international survey to determine the rate of use ATC in daily practice.…”

“…Because ATC was under investigation, we refined the lung model by using an inspiratory effort from an actual subject enrolled in our previous study. 3…”

Redefining “Minimal Ventilator Settings”

“…The wide range of respiratory support, from automatic tube compensation to pressure support up to 10 cm H 2 O, generates a heterogeneous response that makes predicting the outcome difficult, leading to important clinical consequences. [6][7][8] The results of a study showed that 1-hour reconnection to mechanical ventilation after a tolerated SBT significantly reduced the reintubation rate in a population of patients who underwent SBT mostly by T-tube. 5 This result suggests that highly demanding SBT can contribute to extubation failure.…”