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

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).

A 6-month prospective, epidemiological, observational study.

A network of 22 multidisciplinary ICUs in Spain.

Consecutive mechanically ventilated patients with AHRF (defined as Pao₂/Fio₂ ≤ 300 mm Hg on positive end-expiratory pressure [PEEP] ≥ 5 cm H₂O and Fio₂ ≥ 0.3) and followed-up until hospital discharge.

None.

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 H₂O, Fio₂ 0.63 ± 0.22, and plateau pressure 21.5 ± 5.4 cm H₂O. ARDS patients received higher Fio₂ and PEEP than non-ARDS (0.75 ± 0.22 vs 0.59 ± 0.20 cm H₂O and 10.3 ± 3.4 vs 7.7 ± 2.6 cm H₂O, respectively [p < 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; p < 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]; p = 0.837).

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.