Peak Pressures and PaO2/FiO2 Ratios Are Associated With Adverse Outcomes in Patients on Mechanical Ventilators

Patients requiring mechanical ventilation can have complications related to their underlying diseases and hospital-related events. It is possible that easily obtained information early in the course of mechanical ventilation can provide information about important outcomes.

Medical records from 281 episodes of mechanical ventilation in the medical intensive care unit were reviewed to collect information on patient demographics, admitting diagnoses, laboratory tests, duration of mechanical ventilation, the development of ventilator-associated events and mortality. Ventilator pressures from day 2 were analyzed for this study.

Most patients (72.7%) were ≥50 years, 53.8% were men and 66.3% had a body mass index (BMI) ≥ 25kg/m(2).The mean Acute Physiology and Chronic Healthy Evaluation II score was 13.6 ± 5.9. The median initial PaO2/FiO2 was 240 with interquartile range of 177-414. The median duration of ventilation was 4 days (interquartile range: 2-9 days). A PaO2/FiO2 ratio < 100 was associated with increased mortality compared with PaO2/FiO2 ratio > 500, and a BMI > 30kg/m(2) was associated with decreased mortality compared with normal BMIs. A PaO2/FiO2 ratio < 100 and BMIs <18.5kg/m(2) or >30kg/m(2) were all associated with having a ventilator-associated event. There was a positive correlation between peak pressure (day 2) and the duration of ventilation (r = 0.263, P = 0.007).

Easily available information collected on day 2 of mechanical ventilation can help identify patients at risk for poor outcomes, including the duration of mechanical ventilation, the development of ventilator-associated complications and mortality. Prospective studies measuring peak pressures are needed to evaluate the utility of this simple measurement in the management of patients requiring mechanical ventilation.