Utility of pulse oximetry in diagnosing pneumonia in nursing home residents.

BACKGROUND: The differential diagnosis of acute infection in elderly nursing home patients is often difficult. This study evaluated pulse oximetry in pneumonia in this population.
METHODS: A case-control study was performed in a veteran's nursing home involving 2 analyses: (1) pneumonia patients (case subjects) were compared with patients with nonpulmonary infections (control subjects) at time of acute infection; (2) differences in paired values measured at time of infection versus a noninfected baseline were compared for pneumonia patients and control subjects. Vital signs including pulse oximetry were obtained routinely (at least monthly) and with acute illness.
RESULTS: Oxygen saturations were lower in 45 pneumonia patients than in 22 patients with acute nonpulmonary infections (P < 0.001). An oxygen saturation < 94 gave a sensitivity for pneumonia of 80%, specificity of 91%, and positive predictive value of 95%. The drop in oxygen saturation from the last baseline value was greater in pneumonia patients than in control subjects (P < 0.001). The sensitivity of an oxygen saturation drop >3% from baseline for pneumonia was 73% with specificity and positive predictive values of 100%.
CONCLUSIONS: Pulse oximetry may be very helpful in evaluating acutely infected nursing home residents. The present study suggests that in acutely infected nursing home patients, a decrease in oxygen saturation of >3% from baseline, as well as a single oxygen saturation of <94, should suggest pneumonia. A decrease from baseline of <4% or a single oxygen saturation of 94 or higher suggests that pneumonia is unlikely.