Hypoxemia in the ICU: prevalence, treatment, and outcome

Abstract

Background: Information is limited regarding the prevalence, management, and outcome of hypoxemia among intensive care unit (ICU) patients. We assessed the prevalence and severity of hypoxemia in ICU patients and analyzed the management and outcomes of hypoxemic patients.

Methods: This is a multinational, multicenter, 1-day point prevalence study in 117 ICUs during the spring of 2016. All patients hospitalized in an ICU on the day of the study could be enrolled. Hypoxemia was defined as a PaO₂/FiO₂ ratio ≤ 300 mmHg and classified as mild (PaO₂/FiO₂ between 300 and 201), moderate (PaO₂/FiO₂ between 200 and 101), and severe (PaO₂/FiO₂ ≤ 100 mmHg).

Results: Of 1604 patients included, 859 (54%, 95% CI 51-56%) were hypoxemic, 51% with mild (n = 440), 40% with moderate (n = 345), and 9% (n = 74) with severe hypoxemia. Among hypoxemic patients, 61% (n = 525) were treated with invasive ventilation, 10% (n = 84) with non-invasive ventilation, 5% (n = 45) with high-flow oxygen therapy, 22% (n = 191) with standard oxygen, and 1.6% (n = 14) did not receive oxygen. Protective ventilation was widely used in invasively ventilated patients. Twenty-one percent of hypoxemic patients (n = 178) met criteria for acute respiratory distress syndrome (ARDS) including 65 patients (37%) with mild, 82 (46%) with moderate, and 31 (17%) with severe ARDS. ICU mortality was 27% in hypoxemic patients and significantly differed according to severity: 21% in mild, 26% in moderate, and 50% in patients with severe hypoxemia, p < 0.001. Multivariate Cox regression identified moderate and severe hypoxemia as independent factors of ICU mortality compared to mild hypoxemia (adjusted hazard ratio 1.38 [1.00-1.90] and 2.65 [1.69-4.15], respectively).

Conclusions: Hypoxemia affected more than half of ICU patients in this 1-day point prevalence study, but only 21% of patients had ARDS criteria. Severity of hypoxemia was an independent risk factor of mortality among hypoxemic patients. Trial registration NCT 02722031.

Trial registration: ClinicalTrials.gov NCT02722031.

Keywords: ARDS-acute respiratory failure; Critical care; Epidemiology; Hypoxemia; Invasive ventilation.

Fig. 1

Flowchart of the study. P/F: PaO₂/FiO₂ ratio; IV: invasive ventilation, NIV non-invasive ventilation, HFO₂: high-flow oxygen therapy, O₂: low-flow (standard) oxygen therapy, AA: ambient air

Fig. 2

Survival curve according to hypoxemia severity. Survival curves were drawn according to the severity of hypoxemia using the Kaplan–Meier method and were compared using the log-rank test. Follow-up ended at the ICU leaving or was censored at day 90