The PANDORA Study: Prevalence and Outcome of Acute Hypoxemic Respiratory Failure in the Pre-COVID-19 Era.

Objectives: To establish the epidemiological characteristics, ventilator management, and outcomes in patients with acute hypoxemic respiratory failure (AHRF), with or without acute respiratory distress syndrome (ARDS), in the era of lung-protective mechanical ventilation (MV).

Design: A 6-month prospective, epidemiological, observational study.

Setting: A network of 22 multidisciplinary ICUs in Spain.

Patients: Consecutive mechanically ventilated patients with AHRF (defined as Pao/Fio ≤ 300 mm Hg on positive end-expiratory pressure [PEEP] ≥ 5 cm HO and Fio ≥ 0.3) and followed-up until hospital discharge.

Interventions: None.

Measurements And Main Results: Primary outcomes were prevalence of AHRF and ICU mortality. Secondary outcomes included prevalence of ARDS, ventilatory management, and use of adjunctive therapies. During the study period, 9,803 patients were admitted: 4,456 (45.5%) received MV, 1,271 (13%) met AHRF criteria (1,241 were included into the study: 333 [26.8%] met Berlin ARDS criteria and 908 [73.2%] did not). At baseline, tidal volume was 6.9 ± 1.1 mL/kg predicted body weight, PEEP 8.4 ± 3.1 cm HO, Fio 0.63 ± 0.22, and plateau pressure 21.5 ± 5.4 cm HO. ARDS patients received higher Fio and PEEP than non-ARDS (0.75 ± 0.22 vs 0.59 ± 0.20 cm HO and 10.3 ± 3.4 vs 7.7 ± 2.6 cm HO, respectively [ < 0.0001]). Adjunctive therapies were rarely used in non-ARDS patients. Patients without ARDS had higher ventilator-free days than ARDS (12.2 ± 11.6 vs 9.3 ± 9.7 d; < 0.001). All-cause ICU mortality was similar in AHRF with or without ARDS (34.8% [95% CI, 29.7-40.2] vs 35.5% [95% CI, 32.3-38.7]; = 0.837).

Conclusions: AHRF without ARDS is a very common syndrome in the ICU with a high mortality that requires specific studies into its epidemiology and ventilatory management. We found that the prevalence of ARDS was much lower than reported in recent observational studies.