Cognition After Acute Hypoxemic Failure Not Affected by High vs Low PaO₂ Target

Cognitive impairment levels among intensive care unit (ICU) patients who survived acute hypoxemic respiratory failure were similar regardless of whether the partial pressure of arterial oxygen (PaO₂) target used during their ICU stay was 60 vs 90 mm Hg, according to study findings published in the American Journal of Respiratory and Critical Care Medicine.

Researchers for the Long-HOT study assessed the effects of a lower vs higher oxygenation target on cognitive and pulmonary functions at 1 year post ICU stay among adults who had experienced acute hypoxemic respiratory failure.

The Long-HOT study enrolled participants of 2 clinical trials — the Handling Oxygenation Targets in the Intensive Care Unit (HOT-ICU) trial and the Handling Oxygenation Targets in COVID-19 (HOT-COVID) trial (ClinicalTrials.gov Identifiers: NCT03174002 and NCT04425031) — at 1 year after the beginning of those trials. Both trials had randomly assigned participants 1:1 during their ICU stays to PaO₂ targets of 60 mm Hg (lower-oxygenation group) or 90 mm Hg (higher-oxygenation group) for a maximum of 90 days.

Cognitive function was assessed with the Repeatable Battery for the Assessment of Neuropsychological Status (RBANS), and the age-adjusted RBANS global score was the primary cognitive outcome. Pulmonary function was assessed with whole-body plethysmography, and the percentage of predicted pulmonary diffusion capacity of carbon monoxide (DLCO) was the primary pulmonary outcome.

A year after HOT-ICU and HOT-COVID, 54.5% of participants (1916 out of 3654) had survived. Of those, Long-HOT enrolled 417 survivors (median age, 64 years; 67% male) — 209 participants from the lower-oxygenation groups and 208 participants from the higher-oxygenation groups. The 1-year assessments were performed from June 2018 to February 2024.

RBANS testing was conducted in 189 survivors in the lower-oxygenation group at a median 13.7 months after randomization and in 190 survivors in the higher-oxygenation group at 14.0 months after randomization.

The lower-oxygenation group had a median (SD) RBANS global cognitive score of 78 (19) compared with 76 (21) in the higher-oxygenation group (adjusted mean difference, 2; 95% CI, –2 to 6; P =.41).

Whole-body plethysmography was conducted with 196 survivors in the lower-oxygenation cohort at 13.7 months and in 198 survivors in the higher-oxygenation cohort at 13.9 months. A mean DLCO of 68% (22%) was observed in the lower-oxygenation group vs 73% (25%) in the higher-oxygenation group (adjusted mean difference, –5% points; 95% CI, –9 to –1% points; P =.007).

No statistically significant differences were found for treatment effect between trials for the coprimary outcomes (interaction test for RBANS global cognitive score, P =.06; and for DLCO, P =.38).

Limitations include the high dropout rate among eligible survivors and potential survival bias. In addition, the participants’ cognitive and pulmonary functions before their critical illness were unknown; no information was obtained regarding participants’ education levels, ICU delirium status, or smoking status; and patients were tested at only 1 time point.

“A PaO₂ target of 60 vs 90 mm Hg in ICU appeared to result in similar cognitive impairment but might reduce pulmonary diffusion capacity in ICU survivors of hypoxemic respiratory failure,” the researchers concluded.

This article originally appeared on Pulmonology Advisor