Association of respiratory drive and effort with mortality and time to discharge in patients on mechanical ventilation in Canada: a longitudinal, prospective, registry-based cohort study.

Abstract

Physiological data suggest that insufficient and excessive respiratory drive and effort during mechanical ventilation might injure the lung and diaphragm, but their clinical relevance is unknown. In this prospective, registry-based cohort study from the Toronto Intensive Care Observational Registry, we included all adults on mechanical ventilation admitted to the medical-surgical intensive care unit (ICU) at Toronto General Hospital from June 25, 2019, to April 1, 2022. There were no exclusion criteria. We obtained daily measurements of drive (airway occlusion pressure, P_0·1), effort (expiratory occlusion pressure, P_occ), lung stress during spontaneous breathing (dynamic transpulmonary driving pressure, ΔP_L,dyn), and ventilator-delivered dynamic driving pressure (ΔP_aw,dyn) for the first 10 days of mechanical ventilation. Daily hazards of death in ICU or discharge alive from ICU were quantified using Cox proportional hazards models adjusted for changing severity of illness over time. We included 1186 patients. 298 (25%) patients died during follow-up. P_0·1 and P_occ showed a non-linear association with the hazards of death and discharge alive (p≤0·024). In patients with a ratio of arterial partial pressure of oxygen to inspired fraction of oxygen (PaO₂:FiO₂) of 150 mm Hg or less, both low and high levels of P_0·1 and P_occ were associated with lower rate of ICU discharge; when PaO₂:FiO₂ was greater than 150 mm Hg, higher P_0·1 and P_occ were associated with accelerated ICU discharge (interaction p<0·0001). High ΔP_L,dyn was associated with lower rate of ICU discharge (p<0·0001), especially when PaO₂:FiO₂ was less than 150 mm Hg. Higher effort magnified the association between ΔP_aw,dyn and rate of discharge alive (interaction p=0·0052). In patients on mechanical ventilation, insufficient or excessive respiratory drive and effort were associated with higher ICU mortality and lower rate of ICU discharge, particularly when oxygenation was more severely impaired. Elevated respiratory effort exacerbated the effect of ventilator-delivered driving pressure on outcome. National Sanitarium Association, Canada.