Risk Factors for and Prediction of Hypoxemia during Tracheal Intubation of Critically Ill Adults

Abstract

Rationale: Hypoxemia is a common complication during tracheal intubation of critically ill adults and is a frequently used endpoint in airway management research. Identifying patients likely to experience low oxygen saturations during tracheal intubation may be useful for clinical practice and clinical trials.

Objectives: To identify risk factors for lower oxygen saturations and severe hypoxemia during tracheal intubation of critically ill adults and develop prediction models for lowest oxygen saturation and hypoxemia.

Methods: Using data on 433 intubations from two randomized trials, we developed linear and logistic regression models to identify preprocedural risk factors for lower arterial oxygen saturations and severe hypoxemia between induction and 2 minutes after intubation. Penalized regression was used to develop prediction models for lowest oxygen saturation after induction and severe hypoxemia. A simplified six-point score was derived to predict severe hypoxemia.

Results: Among the 433 intubations, 426 had complete data and were included in the model. The mean (standard deviation) lowest oxygen saturation was 88% (14%); median (interquartile range) was 93% (83-98%). Independent predictors of severe hypoxemia included hypoxemic respiratory failure as the indication for intubation (odds ratio [OR], 2.70; 95% confidence interval [CI], 1.58-4.60), lower oxygen saturation at induction (OR, 0.92 per 1% increase; 95% CI, 0.89-0.96 per 1% increase), younger age (OR, 0.97 per 1-year increase; 95% CI, 0.95-0.99 per 1-year increase), higher body mass index (OR, 1.03 per 1 kg/m²; 95% CI, 1.00-1.06 per 1 kg/m²), race (OR, 4.58 for white vs. black; 95% CI, 1.97-10.67; OR, 4.47 for other vs. black; 95% CI, 1.19-16.84), and operator with fewer than 100 prior intubations (OR, 2.83; 95% CI, 1.37-5.85). A six-point score using the identified risk factors predicted severe hypoxemia with an area under the receiver operating curve of 0.714 (95% CI, 0.653 to 0.778).

Conclusions: Lowest oxygen saturation and severe hypoxemia during tracheal intubation in the intensive care unit can be accurately predicted using routinely available preprocedure clinical data, with saturation at induction and hypoxemic respiratory failure being the strongest predictors. A simple bedside score may identify patients at risk for hypoxemia during intubation to help target preventative interventions and facilitate enrichment in clinical trials.

Keywords: critical care; hypoxia; intratracheal; intubation; predictive value of tests.

Figure 1.

Predicted lowest arterial oxygen saturation for the independently associated risk factors adjusted for covariates. Each plot displays the predicted lowest arterial oxygen saturation and 95% confidence interval for the variation of one risk factor. Predictions are adjusted to the median of the remaining model covariates (indication for intubation neither hypoxemic nor hypercapnic, not receiving noninvasive ventilation in the preceding 6 h, highest fraction inspired of oxygen in the prior 6 h of 0.4, arterial oxygen saturation at induction of 99%, age 58 yr, Acute Physiology and Chronic Health Evaluation [APACHE] II score of 22, body mass index of 27.8 kg/m², male sex, white race, no sepsis, and operator experience with 61 prior procedures). Sp_O2 = arterial oxygen saturation as measured by continuous pulse oximetry.

Figure 2.

Calibration of Age, Trainee, Race, Indication, Sp_O2, kg/m² (AT RISK) score with severe hypoxemia. Height of bar depicts percentage of patients with severe hypoxemia by AT RISK score. Sp_O2 = arterial oxygen saturation as measured by continuous pulse oximetry.