ABSTRACT
Background Several forms of noninvasive ventilatory supports have a high consumption of oxygen which may precipitate oxygen shortage, as experienced during the COVID-19 pandemic. In this bench-to-bedside study, we assessed the performances of a new continuous positive airway pressure (CPAP) device using a large a reservoir (the “Bag-CPAP”) designed to minimize oxygen consumption and compared it with other CPAP devices. Methods First, a bench study compared the performances of the Bag-CPAP and four CPAP devices to an intensive care unit ventilator. Two FiO2 targets (40-60% and 80-100%) at a predefined positive end expiratory pressure (PEEP) level between 5 and 10 cm H2O were tested and fraction of inspired oxygen (FiO2) and oxygen consumption were measured. Device-imposed work of breathing (WOB) was also evaluated. Second, an observational clinical study evaluated the new CPAP in 20 adult patients with acute respiratory failure in two hospitals in France. Actual FiO2, PEEP, peripheral oxygen saturation, respiratory rate and dyspnea score were assessed. Results All six systems tested in the bench study reached the minimal FiO2 target of 40% and four were able to reach at least 80% FiO2 while maintaining PEEP in the predefined range. The ratio of FiO2 delivered to the oxygen consumed was the highest with the new reservoir-based CPAP whatever the FiO2 target. The WOB induced by the device was slightly higher with the Bag-CPAP. In the clinical study, the Bag-CPAP was well tolerated and could reach high (>90%) and moderate (>50%) FiO2 with an oxygen flow rate of 15 [15-16] and 8 [7-9] L/min, respectively. Dyspnea score improved significantly after introduction of Bag-CPAP, and SpO2 increased. Conclusions In vitro, the Bag-CPAP exhibited the highest oxygen saving properties. It was well accepted clinically and reduces dyspnea. The Bag-CPAP may be useful to treat patients with acute respiratory failure in the field, especially when facing constraints in oxygen delivery.
Subject(s)
COVID-19 , Dyspnea , Respiratory InsufficiencyABSTRACT
Purpose: Whether the use of high-flow nasal oxygen in adult patients with COVID-19 associated acute respiratory failure improves clinically relevant outcomes remains unclear. We thus sought to assess the effect of high-flow nasal oxygen on ventilator-free days, compared to early initiation of invasive mechanical ventilation, on adult patients with COVID-19. Methods: : We conducted a multicentre cohort study using a prospectively collected database of patients with COVID-19 associated acute respiratory failure admitted to 36 Spanish and Andorran intensive care units (ICUs). Main exposure was the use of high-flow nasal oxygen (conservative group), while early invasive mechanical ventilation (within the first day of ICU admission; early intubation group) served as the comparator. The primary outcome was ventilator-free days at 28 days. ICU length of stay and all-cause in-hospital mortality served as secondary outcomes. We used propensity score matching to adjust for measured confounding. Results: : Out of 468 eligible patients, a total of 122 matched patients were included in the present analysis (61 for each group). When compared to early intubation, the use of high-flow nasal oxygen was associated with an increase in ventilator-free days (mean difference: 8.0 days; 95% confidence interval (CI): 4.4 to 11.7 days), and a reduction in ICU length of stay (mean difference: -8.2 days; 95% CI -12.7 to -3.6 days). No difference was observed in all-cause in-hospital mortality between groups (odds ratio: 0.64; 95% CI: 0.25 to 1.64). Conclusions: The use of high-flow nasal oxygen upon ICU admission in adult patients with COVID-19 related acute hypoxemic respiratory failure may lead to an increase in ventilator-free days and a reduction in ICU length of stay, when compared to early initiation of invasive mechanical ventilation. Future studies should confirm our findings.
Subject(s)
COVID-19 , Respiratory InsufficiencyABSTRACT
Background: Several Intensive Care Units (ICU) have been overwhelmed by the surge of COVID-19 patients thus necessitating to extend ventilation capacity outside the ICU where air and oxygen pressure are not always available. Transport ventilators requiring only O2 source may be used to deliver volume-controlled ventilation. Objective: To evaluate the performances of four transport ventilators compared to an ICU ventilator simulating severe respiratory conditions. Materials and methods: Two pneumatic transport ventilators, (Oxylog 3000, Draeger; Osiris 3, Air Liquide Medical Systems) and two turbine transport ventilators (Elisee 350, ResMed; Monnal T60, Air Liquide Medical Systems) were compared to an ICU ventilator (Engstrom Carestation - GE Healthcare) using a Michigan training test lung. We tested each ventilator with different set volumes Vtset (350, 450, 550 ml) and different compliances (20 or 50 ml/cmH2O) and a resistance of 15 cmH20/L/sec based on values recently described in COVID-19 Acute Respiratory Distress Syndrome. Volume error was measured, as well as the trigger time delay during assist-control ventilation simulating spontaneous breathing activity with a P0.1 of 4 cmH20. Results: Grouping all conditions, the volume error was 2.9 +/- 2.2 % for Engstrom Carestation; 3.6 +/- 3.9 % for Osiris 3; 2.5 +/- 2.1 % for Oxylog 3000; 5.4 +/- 2.7 % for Monnal T60 and 8.8 +/- 4.8 % for Elisee 350. Grouping all conditions, trigger delay was 42 +/- 4 ms, 65 +/- 5 ms, 151 +/- 14 ms, 51 +/- 6 and 64 +/- 5 ms for Engstrom Carestation, Osiris 3, Oxylog 3000, Monnal T60 and Elisee 350, respectively. Conclusions: In special surge situations such as COVID-19 pandemic, most transport ventilators may be used to safely deliver volume-controlled ventilation in locations where only oxygen pressure supply is available with acceptable volume accuracy. Performances regarding triggering function are generally acceptable but vary across ventilators.