Optimization of ventilator setting by flow and pressure waveforms analysis during noninvasive ventilation for acute exacerbations of COPD: a multicentric randomized controlled trial

Abstract

IntroductionThe analysis of flow and pressure waveforms generated by ventilators can be useful in the optimization of patient-ventilator interactions, notably in chronic obstructive pulmonary disease (COPD) patients. To date, however, a real clinical benefit of this approach has not been proven.MethodsThe aim of the present randomized, multi-centric, controlled study was to compare optimized ventilation, driven by the analysis of flow and pressure waveforms, to standard ventilation (same physician, same initial ventilator setting, same time spent at the bedside while the ventilator screen was obscured with numerical data always available). The primary aim was the rate of pH normalization at two hours, while secondary aims were changes in PaCO2, respiratory rate and the patient's tolerance to ventilation (all parameters evaluated at baseline, 30, 120, 360 minutes and 24 hours after the beginning of ventilation). Seventy patients (35 for each group) with acute exacerbation of COPD were enrolled.ResultsOptimized ventilation led to a more rapid normalization of pH at two hours (51 vs. 26% of patients), to a significant improvement of the patient's tolerance to ventilation at two hours, and to a higher decrease of PaCO2 at two and six hours. Optimized ventilation induced physicians to use higher levels of external positive end-expiratory pressure, more sensitive inspiratory triggers and a faster speed of pressurization.ConclusionsThe analysis of the waveforms generated by ventilators has a significant positive effect on physiological and patient-centered outcomes during acute exacerbation of COPD. The acquisition of specific skills in this field should be encouraged.Trial registrationClinicalTrials.gov NCT01291303.

Patient-ventilator asynchronies: may the respiratory mechanics play a role?

“…Having said this, we have shown that the occurrence of asynchronies is very frequent even when the settings are performed in expert centers [2]. A close look at some indirect indices of mismatching (that is, the flow waveform), may help the clinician to detect the most frequent asynchrony between the patient and the machine, that is, ineffective effort [22]. Indeed, it is of clinical interest that, despite the different underlying pathologies, the settings decided by the operators to achieve the same aims (that is, gas exchange amelioration and tidal volume increase) are very similar, and also induced comparable amounts of asynchronies.…”

Noninvasive ventilation in acute respiratory failure: which recipe for success?

“…Patient-ventilator asynchrony, and therefore the likelihood of NPPV failure may be prevented by the optimisation of ventilator settings using the screen ventilator waveforms, adjusting trigger sensitivity, increasing PEEP, minimising air leaks or using different modes or more sophisticated ventilators [109]. New modes of ventilation, such as neutrally adjusted ventilator assist, have been documented to reduce asynchrony even in the presence of air leaks [110].…”

Semiquantitative cough strength score and associated outcomes in noninvasive positive pressure ventilation patients with acute exacerbation of chronic obstructive pulmonary disease

“…Patients were ventilated with bi-level positive airway pressure in S/T mode (BiPAP Vision or Respironics V60). Expiratory positive airway pressure was initially set at 4 cm H 2 O and titrated according to the flow curve to ensure that expiratory flow reached zero prior to inspiration or diminished ineffective efforts [16]. FiO 2 was set to maintain SpO 2 at around 95%.…”