Updated 9 April 2020
Non-invasive mechanical ventilation modalities in supporting patients in ARDS
This page addresses continuous positive airway pressure (CPAP) and bilevel positive airway pressure (BiPAP) which are modes of non-invasive ventilatory support. It is important to point out that mask-based solutions are not sufficient for patients experiencing hypoxic respiratory failure. At best, these are temporary solutions. These solutions both risk aerosolizing COVID-19 in the expired air which, generally, is not filtered.
CPAP is primarily used to help with oxygenation by applying a constant positive pressure throughout the patient’s respiratory cycle. It is commonly used for patients with obstructive airway or oxygenation problems. Patients have hypoxic respiratory insufficiency, but they do not yet have respiratory failure.
BiPAP detects the patient’s inspiratory and expiratory efforts and provides a differential positive airway pressure to help ease the work of respiration. Patients who are “tiring out” and demonstrate hypercarbic respiratory insufficiency would benefit from BiPAP over CPAP. Care must be taken to identify failure and intubate.
Intubation is necessary for patients experiencing respiratory failure because the effort of breathing is removed. The patient can be sedated and paralyzed, if need be, and higher pressure is used to keep gas exchange occurring in a diseased lung. Some patients can recover with CPAP and BiPAP, so clinical discretion should be used before intubation, but with ARDS intubation is likely.
In COVID-19 positive patients, non-invasive mechanical ventilation modalities can certainly be trialed, but careful monitoring for worsening of the patient towards respiratory failure should be diagnosed without delay so invasive ventilatory therapy can be initiated. Delay and/or failure to provide timely invasive positive pressure ventilatory support can lead to patient self-inflicted lung injury, please see this paper. At this point the only solution is invasive ventilation.