ABSTRACT
BACKGROUND: SARS-CoV-2 aerosolization during noninvasive positive-pressure ventilation may endanger health care professionals. Various circuit setups have been described to reduce virus aerosolization. However, these setups may alter ventilator performance. RESEARCH QUESTION: What are the consequences of the various suggested circuit setups on ventilator efficacy during CPAP and noninvasive ventilation (NIV)? STUDY DESIGN AND METHODS: Eight circuit setups were evaluated on a bench test model that consisted of a three-dimensional printed head and an artificial lung. Setups included a dual-limb circuit with an oronasal mask, a dual-limb circuit with a helmet interface, a single-limb circuit with a passive exhalation valve, three single-limb circuits with custom-made additional leaks, and two single-limb circuits with active exhalation valves. All setups were evaluated during NIV and CPAP. The following variables were recorded: the inspiratory flow preceding triggering of the ventilator, the inspiratory effort required to trigger the ventilator, the triggering delay, the maximal inspiratory pressure delivered by the ventilator, the tidal volume generated to the artificial lung, the total work of breathing, and the pressure-time product needed to trigger the ventilator. RESULTS: With NIV, the type of circuit setup had a significant impact on inspiratory flow preceding triggering of the ventilator (P < .0001), the inspiratory effort required to trigger the ventilator (P < .0001), the triggering delay (P < .0001), the maximal inspiratory pressure (P < .0001), the tidal volume (P = .0008), the work of breathing (P < .0001), and the pressure-time product needed to trigger the ventilator (P < .0001). Similar differences and consequences were seen with CPAP as well as with the addition of bacterial filters. Best performance was achieved with a dual-limb circuit with an oronasal mask. Worst performance was achieved with a dual-limb circuit with a helmet interface. INTERPRETATION: Ventilator performance is significantly impacted by the circuit setup. A dual-limb circuit with oronasal mask should be used preferentially.
Subject(s)
COVID-19 , Continuous Positive Airway Pressure , Disease Transmission, Infectious/prevention & control , Noninvasive Ventilation , Air Filters , Benchmarking/methods , COVID-19/therapy , COVID-19/transmission , Continuous Positive Airway Pressure/adverse effects , Continuous Positive Airway Pressure/instrumentation , Continuous Positive Airway Pressure/methods , Critical Pathways/standards , Critical Pathways/trends , Humans , Infectious Disease Transmission, Patient-to-Professional/prevention & control , Noninvasive Ventilation/adverse effects , Noninvasive Ventilation/instrumentation , Noninvasive Ventilation/methods , Research Design , Respiratory Function Tests/methods , SARS-CoV-2 , Treatment Outcome , Ventilators, MechanicalABSTRACT
OBJECTIVE: The aim of this pilot study was to assess physical fitness and its relationship with functional dyspnea in survivors of COVID-19 6 months after their discharge from the hospital. METHODS: Data collected routinely from people referred for cardiopulmonary exercise testing (CPET) following hospitalization for COVID-19 were retrospectively analyzed. Persistent dyspnea was assessed using the modified Medical Research Council dyspnea scale. RESULTS: Twenty-three people with persistent symptoms were referred for CPET. Mean modified Medical Research Council dyspnea score was 1 (SD = 1) and was significantly associated with peak oxygen uptake (VO2peak; %) (rho = -0.49). At 6 months, those hospitalized in the general ward had a relatively preserved VO2peak (87% [SD = 20]), whereas those who had been in the intensive care unit had a moderately reduced VO2peak (77% [SD = 15]). Of note, the results of the CPET revealed that, in all individuals, respiratory equivalents were high, power-to-weight ratios were low, and those who had been in the intensive care unit had a relatively low ventilatory efficiency (mean VE/VCO2 slope = 34 [SD = 5]). Analysis of each individual showed that none had a breathing reserve <15% or 11 L/min, all had a normal exercise electrocardiogram, and 4 had a heart rate >90%. CONCLUSION: At 6 months, persistent dyspnea was associated with reduced physical fitness. This study offers initial insights into the mid-term physical fitness of people who required hospitalization for COVID-19. It also provides novel pathophysiological clues about the underlaying mechanism of the physical limitations associated with persistent dyspnea. Those with persistent dyspnea should be offered a tailored rehabilitation intervention, which should probably include muscle reconditioning, breathing retraining, and perhaps respiratory muscle training. IMPACT: This study is the first, to our knowledge, to show that a persistent breathing disorder (in addition to muscle deconditioning) can explain persistent symptoms 6 months after hospitalization for COVID-19 infection and suggests that a specific rehabilitation intervention is warranted.