USE OF FLOW-VOLUME CURVES IN DETECTING SECRETIONS IN VENTILATOR-DEPENDENT PATIENTS

A noninvasive means of detecting airway secretions in ventilator-depen dent patients is desirable because endotracheal suctioning can result in life-threatening complications. In a patient who had copious secret ions, we observed a sawtooth pattern on his flow-volume curve that dis appeared after suctioning. Accordingly, we systematically examined the usefulness of a sawtooth pattern on flow-volume curves in detecting s ecretions in ventilator-dependent patients and compared its accuracy w ith clinical examination. Flow-volume curves were recorded in 50 venti lator-dependent patients over 1 min of spontaneous breathing. In 15 of these patients, clinical examination was performed by three clinician s to determine its accuracy in detection of secretions. Endotracheal s uctioning was then performed to determine the presence or absence of s ecretions. Subsequently, the flow-volume curves of all 50 patients wer e played back on a video screen, and three observers, who were unaware of the results of suctioning, made a decision regarding the presence or absence of a sawtooth pattern. The sensitivity of the sawtooth patt ern in detecting secretions ranged from 0.76 to 0.86, and specificity ranged from 0.86 to 0.90. The likelihood ratio of a positive test rang ed from 5.55 to 7.97, whereas the likelihood ratio of a negative test ranged from 0.16 to 0.27. Interobserver agreement, assessed by the kap pa statistic, was excellent: 0.76, 0.76, and 0.84. In the subgroup of patients evaluated by both clinical examination and flow-volume curve analysis, clinical examination was less accurate in 11 of the 15 patie nts. In conclusion, detection of a sawtooth pattern strongly suggests the presence of secretions, and the absence of this pattern suggests t hat secretions are unlikely to be present.