Abstract
BackgroundThe COVID-19 pandemic has resulted in increased admissions with respiratory failure and there have been reports of oxygen failure and shortages of machines to deliver ventilation and Continuous Positive Airway Pressure (CPAP). Domiciliary ventilators which entrain room air have been widely used during the pandemic. Poor outcomes reported with non-invasive respiratory support using ventilators which lack an oxygen blender could be related to an unreliable Fraction of inspired O2 (FiO2). Additionally, with concerns about oxygen failure, the variety of ventilator circuits used as well as differing peak inspiratory flow rates (PIFR) could impact on the FiO2 delivered during therapy with domiciliary ventilators.MethodsIn a series of bench tests, we tested the effect of choice of circuit and different PIFR on the FiO2 achieved during simulation of ventilation and CPAP therapy using domiciliary ventilators.ResultsFiO2 was highly dependent upon the type of circuit used with circuits with an active exhalation valve achieving similar FiO2 at lower oxygen flow rates than circuits using an exhalation port. During CPAP therapy, high PIFR resulted in significantly lower FiO2 than low PIFR.ConclusionsThis study has implications for oxygen usage as well as delivery of non-invasive respiratory support during therapy with domiciliary ventilators when these are used during the second wave of COVID-19.
Highlights
The COVID-19 crisis caused by SARS-CoV-2 has resulted in significant increases in critical care utilisation across the world
A higher Fraction of inspired O2 (FiO2) was seen in any circuit with an active exhalation valve compared to a single limb circuit with an exhalation port during mandatory ventilation in either volume control or pressure control ventilation
Oxygen flow rate l/min flow rate of 15 L/min in all circuits using active exhalation valves during mandatory ventilation. This was noted with the active exhalation valve in the single limb circuit in which an FiO2 of greater than 0.85 was seen during mandatory ventilation with an oxygen flow rate of 10 litres/minute
Summary
The COVID-19 crisis caused by SARS-CoV-2 has resulted in significant increases in critical care utilisation across the world. The COVID-19 pandemic has resulted in increased admissions with respiratory failure and there have been reports of oxygen failure and shortages of machines to deliver ventilation and Continuous Positive Airway Pressure (CPAP). With concerns about oxygen failure, the variety of ventilator circuits used as well as differing peak inspiratory flow rates (PIFR) could impact on the FiO2 delivered during therapy with domiciliary ventilators. Methods: In a series of bench tests, we tested the effect of choice of circuit and different PIFR on the FiO2 achieved during simulation of ventilation and CPAP therapy using domiciliary ventilators. Conclusions: This study has implications for oxygen usage as well as delivery of non-invasive respiratory support during therapy with domiciliary ventilators when these are used during the second wave of COVID-19
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