Abstract
BackgroundDespite considerable progress, it remains unclear why some patients admitted for COVID-19 develop adverse outcomes while others recover spontaneously. Clues may lie with the predisposition to hypoxemia or unexpected absence of dyspnea (‘silent hypoxemia’) in some patients who later develop respiratory failure. Using a recently-validated breath-holding technique, we sought to test the hypothesis that gas exchange and ventilatory control deficits observed at admission are associated with subsequent adverse COVID-19 outcomes (composite primary outcome: non-invasive ventilatory support, intensive care admission, or death).MethodsPatients with COVID-19 (N = 50) performed breath-holds to obtain measurements reflecting the predisposition to oxygen desaturation (mean desaturation after 20-s) and reduced chemosensitivity to hypoxic-hypercapnia (including maximal breath-hold duration). Associations with the primary composite outcome were modeled adjusting for baseline oxygen saturation, obesity, sex, age, and prior cardiovascular disease. Healthy controls (N = 23) provided a normative comparison.ResultsThe adverse composite outcome (observed in N = 11/50) was associated with breath-holding measures at admission (likelihood ratio test, p = 0.020); specifically, greater mean desaturation (12-fold greater odds of adverse composite outcome with 4% compared with 2% desaturation, p = 0.002) and greater maximal breath-holding duration (2.7-fold greater odds per 10-s increase, p = 0.036). COVID-19 patients who did not develop the adverse composite outcome had similar mean desaturation to healthy controls.ConclusionsBreath-holding offers a novel method to identify patients with high risk of respiratory failure in COVID-19. Greater breath-hold induced desaturation (gas exchange deficit) and greater breath-holding tolerance (ventilatory control deficit) may be independent harbingers of progression to severe disease.
Highlights
IntroductionIt remains unclear why some patients admitted for COVID-19 develop adverse outcomes while others recover spontaneously
Despite considerable progress, it remains unclear why some patients admitted for COVID-19 develop adverse outcomes while others recover spontaneously
Ground glass opacities and consolidation seen in computed tomography prior to respiratory failure [5, 14, 15] suggest that gas exchange deficits are a likely risk factor
Summary
It remains unclear why some patients admitted for COVID-19 develop adverse outcomes while others recover spontaneously. One of the most consistent risk factors for adverse outcomes of COVID-19 is lower baseline SpO2 [5, 7, 8], a reflection of disease-related gas exchange deficits (e.g. ventilation/perfusion [V/Q] heterogeneity). In addition to baseline SpO2, reports from Italy early in the pandemic described successful triage of patients using exertional desaturation (cardiometabolic challenge) [10,11,12] as a means to reveal gas exchange abnormalities. Ground glass opacities and consolidation seen in computed tomography prior to respiratory failure [5, 14, 15] suggest that gas exchange deficits are a likely risk factor. There is a lack of available physiological data on the risks of respiratory failure associated with blunted v. robust ventilatory control in patients with COVID-19
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