Use of capnography to verify emergency ventilator sharing in the COVID-19 era

Abstract

Exacerbation of COVID-19 pandemic may lead to acute shortage of ventilators, which may require shared use of ventilator as a lifesaving concept. Two model lungs were ventilated with one ventilator to i) test the adequacy of individual tidal volumes via capnography, ii) assess cross-breathing between lungs, and iii) offer a simulation-based algorithm for ensuring equal tidal volumes. Ventilation asymmetry was induced by placing rubber band around one model lung, and the uneven distribution of tidal volumes (VT) was counterbalanced by elevating airflow resistance (HR) contralaterally. VT, end-tidal CO₂ concentration (ETCO₂), and peak inspiratory pressure (Ppi) were measured. Unilateral LC reduced VT and elevated ETCO₂ on the affected side. Under HR, VT and ETCO₂ were re-equilibrated. In conclusion, capnography serves as simple, bedside method for controlling the adequacy of split ventilation in each patient. No collateral gas flow was observed between the two lungs with different time constants. Ventilator sharing may play a role in emergency situations.

Keywords: COVID-19; Capnography; Lung compliance; Mechanical ventilation; Pandemic; Respiratory mechanics; Respiratory rescue manoeuvre; Respiratory resistance; Ventilator splitting.