Characteristics and predictors for silent hypoxemia in a cohort of hospitalized COVID-19 patients

Abstract

Background An intriguing feature recently unveiled in some COVID-19 patients is the “silent hypoxemia” phenomenon, which refers to the discrepancy of subjective well-being sensation while suffering hypoxia, manifested as the absence of dyspnea. Objective To describe the clinical characteristics and predictors of silent hypoxemia in hospitalized COVID-19 patients. Methods We conducted a prospective cohort study including consecutive hospitalized adult (≥ 18 years) patients with confirmed COVID-19 presenting to the emergency department with oxygen saturation (SpO2) ≤ 80% on room air from March 15 to June 30, 2020. We analyzed the characteristics, disease severity, and in-hospital outcomes of patients presenting with dyspnea and those without dyspnea (silent hypoxemia). Results We studied 470 cases (64.4% men; median age 55 years, interquartile range 46–64). There were 447 (95.1%) patients with dyspnea and 23 (4.9%) with silent hypoxemia. The demographic and clinical characteristics, comorbidities, laboratory and imaging findings, disease severity, and outcomes were similar between groups. Higher breathing and heart rates correlated significantly with lower SpO 2 in patients with dyspnea but not in those with silent hypoxemia. Independent predictors of silent hypoxemia were the presence of new-onset headache (OR 2.919, 95% CI 1.101–7.742; P = 0.031) and presenting to the emergency department within the first eight days after symptoms onset (OR 3.183, 95% CI 1.024–9.89; P = 0.045). Conclusions Patients with silent hypoxemia sought medical attention earlier and had new-onset headache more often. They were also likely to display lower hemodynamic compensatory responses to hypoxemia, which may underestimate the disease severity.

Predictors of silent hypoxia in hospitalized patients with COVID-19 in Japan

“…The results were partially similar to those in the study by García-Grimshaw et al, which identified DSO as a predictor of SH [ 6 ]. However, they were not concordant with the report by Alhusain et al, which did not include DSO or vitals on admission [ 7 ].…”

Physiotherapy management for COVID-19 in the acute hospital setting and beyond: an update to clinical practice recommendations

“…Silent or ‘happy’ hypoxaemia is a term that has evolved to describe an atypical clinical phenomenon in severe and critical COVID-19 patients where significant hypoxaemia is present, but subjectively patients have a feeling of wellbeing, often with the absence of dyspnoea or respiratory distress. 37 Despite the severe hypoxaemia, patients may be calm, awake and have near-normal lung compliance. 38 The pathophysiological cause of silent hypoxaemia is unclear, but it may be due to intrapulmonary shunting, loss of lung perfusion regulation, endothelial injury and impaired diffusion capacity.…”

Silent Hypoxia in Coronavirus disease-2019: Is it more dangerous? -A retrospective cohort study

“…Grimshaw et al . [ 6 ] reported a cohort of 470 patients with hypoxia defined as SpO 2 <80% and found that 5% of them had no breathlessness. In this study, the authors observed that the patients with silent hypoxia presented earlier to the hospital due to new-onset headaches and the mortality was higher in patients with dyspnoeic hypoxia (43.2%) as compared to those with silent hypoxia (30.4%).…”

“…The incidence of silent hypoxia in COVID-19 has been reported to be 32%–65% in various studies. [ 4 5 6 ] The reports on patients with silent hypoxia are conflicting, with some studies reporting poorer outcomes while others reporting better outcomes. [ 7 ] In the pandemic setting, patients with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection are advised to isolate at home due to the non-availability of hospital beds and seek hospitalisation when red flags such as breathlessness and tachypnoea occur.…”