High Respiratory Effort During Invasive Pressure Support Ventilation

Abstract

Background

High respiratory effort may be common in invasively ventilated patients receiving pressure support ventilation, but its epidemiologic characteristics are unclear.

Research Question

What are the epidemiologic characteristics of high respiratory efforts in critically ill patients, does agreement exist between high respiratory drive and high respiratory effort, what are clinician responses during such events, and what is the relationship between those with clinical parameters and outcomes?

Study Design and Methods

This clinician-masked, prospective, observational study in 2 centers measured the drop in airway pressure during the first 100 ms of an inspiratory effort with an occluded airway (P_0.1), a validated noninvasive measure of respiratory drive, in patients receiving pressure support ventilation for > 24 hours. We also measured estimated respiratory muscle pressure (_eP_musc), a validated surrogate of inspiratory effort. We measured _eP_musc and P_0.1 twice daily.

Results

Of 528 ventilated patients, 80 patients received pressure support ventilation for > 24 hours. Among them, 33 patients (41%) exhibited high respiratory effort, which was more common in COVID-19 ARDS, with 19 of such patients (58%) reached the predefined threshold vs 14 patients (27%) in the non-COVID-19 cohort (OR, 5.0; 95% CI, 1.9-14.9; P = .001). Moreover, 36% of P_0.1 values were ≥ 4 cm H₂O, indicating high respiratory drive. Moderate agreement was found between _eP_musc and P_0.1 measurements (intraclass correlation coefficient, 0.65), suggesting significant discrepancies between those 2 parameters. Clinician-directed management based on usual clinical observations (but masked to P_0.1 and _eP_musc) rarely changed in the presence of high respiratory effort. Higher _eP_musc and its concomitant elevation with P_0.1 were associated with worse blood gas parameters and respiratory mechanics. A concomitant elevation of both _eP_musc and P_0.1 was associated independently with a decreased likelihood of being alive and ventilator-free up to day 28 (OR, 0.26; 95% CI, 0.06-0.87; P = .037).

Interpretation

In this study, many critical care patients receiving invasive pressure support ventilation exhibited high respiratory efforts. In these patients, adjustments to ventilator settings were uncommon, despite association with worse clinical parameters and outcomes.