New manuscript: Outcomes and Predictors of Severe Hyperoxemia in Patients Receiving Mechanical Ventilation: A Single-Center Cohort Study
Oxygen is (arguably) the most commonly given drug in the ICU. It can be life-saving for patients with respiratory failure, but it can also be a poison: healthy mice exposed to >95% oxygen will uniformly die within 5 days. Our group previously showed that oxygen alters respiratory and gut bacteria, and the microbiome plays a role in oxygen-induced lung injury. Despite the ubiquity of oxygen in clinical practice, we still don’t know how to dose it.
In this just-published study, Sanjeev Tyagi (co-mentored by Robert Dickson and Mike Sjoding) set out to determine: 1) what level of arterial oxygenation is associated with harm, 2) how common is this harmful hyperoxemia in ICU patients, and 3) what are the clinical predictors of harmful hyperoxemia? Sanjeev studied >2,000 mechanically ventilated patients with >33,000 (!) arterial blood gases. He found that 1) there is no relationship between arterial oxygen and mortality below 200 mmHg, but a linear positive relationship above this threshold, 2) there is no duration threshold below which this relationship is not seen (i.e. there doesn’t appear to be a minimum duration below which PaO2 > 200 is safe), 3) more than half (55%) of mechanically ventilated patients have at least one PaO2 above this threshold, 4) more than 1 in 7 patients (13.1%) were exposed to PaO2 > 200 on multiple days of their ICU stay, and 5) the ICU of admission was the strongest predictor of severe hyperoxemia. ”If patients spent an entire day exposed to PaO2 > 200 mmHg, they had 2.19 (95% CI 1.33 – 3.60, p = 0.002) greater odds of 30-day mortality in an adjusted analysis.”
Several recent RCTs have looked at conservative vs liberal oxygen dosing, yet none of them include patients exposed to arterial hyperoxemia in the range that unambiguous causes harm in humans and animals (PaO2 > 200). Yet in real-world ICU patients, harmful hyperoxemia is incredibly common (>55% of all patients) and persistent (>13% on multiple days). There is no legitimate clinical indication for a PaO2 > 200 mmHg, and abundant evidence that it is harmful. Perhaps the field should shift from trying to finding an optimal “dose” of oxygen within the safe range and instead treat harmful, persistent hyperoxemia as an unacceptable “never event” that should be studied like other quality-improvement issues.
Manuscript: Outcomes and Predictors of Severe Hyperoxemia in Patients Receiving Mechanical Ventilation: A Single-Center Cohort Study (Annals of the American Thoracic Society)
Sanjeev Tyagi