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Table 1 Bench study

From: Continuous positive airway pressure for respiratory support during COVID-19 pandemic: a frugal approach from bench to bedside

Changes expressed in % of baseline value without filter Low inspiratory effort
(Pmus = −5 cm H2O)
Moderate inspiratory effort
(Pmus = − 10 cm H2O)
∆ Volume ∆ WOB imposed ∆ WOB patient ∆ Volume ∆ WOB imposed ∆ WOB patient
Resistance 5 cm H2O/L/s FF-CPAP 6 cm H2O − 16.5%  + 105.8%  + 34.2% − 15.5%  + 98.3%  + 29.9%
FF-CPAP 10 cm H2O − 15.3%  + 64.8%  + 32.5% − 15.9%  + 69.0%  + 27.7%
Resistance 15 cm H2O/L/s FF-CPAP 6 cm H2O − 10.9%  + 90.4%  + 13.2% − 11.3%  + 95.9%  + 8.5%
FF-CPAP 10 cm H2O − 9.4%  + 51.7%  + 14.5% − 9.6%  + 57.6%  + 9.8%
  1. Influence of the filter on tidal volume and work of breathing during low and moderate simulated inspiratory efforts
  2. Pmus simulated muscle pressure, ∆ Volume tidal volume variation induced by the filter as compared to baseline (without filter), ∆ WOBimposed variation of work of breathing imposed by the CPAP induced by the filter as compared to baseline (without filter). WOBimposed was calculated from the airway pressure–volume loop. ∆ WOBpatient variation of simulated patient’s work of breathing needed to maintain the tidal volume constant after having added the filter. WOBpatient was calculated from the muscle pressure–volume loop, PEEP positive end-expiratory pressure, FF-CPAP filter frugal continuous positive airway pressure (see text for definition)