Effect of backrest elevation on the development of ventilator-associated pneumonia

Ventilator-associated pneumonia is a common complication of mechanical ventilation. Backrest position and time spent supine are critical risk factors for aspiration, increasing the risk for pneumonia. Empirical evidence of the effect of backrest positions on the incidence of ventilator-associated pneumonia, especially during mechanical ventilation over time, is limited.

To describe the relationship between backrest elevation and development of ventilator-associated pneumonia.

A nonexperimental, longitudinal, descriptive design was used. The Clinical Pulmonary Infection Score was used to determine ventilator-associated pneumonia. Backrest elevation was measured continuously with a transducer system. Data were obtained from laboratory results and medical records from the start of mechanical ventilation up to 7 days.

Sixty-six subjects were monitored (276 patient days). Mean backrest elevation for the entire study period was 21.7 degrees . Backrest elevations were less than 30 degrees 72% of the time and less than 10 degrees 39% of the time. The mean Clinical Pulmonary Infection Score increased but not significantly, and backrest elevation had no direct effect on mean scores. A model for predicting the Clinical Pulmonary Infection Score at day 4 included baseline score, percentage of time spent at less than 30 degrees on study day 1, and score on the Acute Physiology and Chronic Health Evaluation II, explaining 81% of the variability (F=7.31, P=.003).

Subjects spent the majority of the time at backrest elevations less than 30 degrees . Only the combination of early, low backrest elevation and severity of illness affected the incidence of ventilator-associated pneumonia.