Clinical examination reliably detects intrinsic positive end-expiratory pressure in critically III, mechanically ventilated patients

Abstract

Critically ill patients requiring mechanical ventilation often develop intrinsic positive end-expiratory pressure (PEEP(i)). Methods for its detection include an expiratory flow waveform display (not always available), an esophageal pressure transducer (invasive), or a relaxed or paralyzed patient. We sought to determine the accuracy of clinical examination for detecting PEEP(i). Examiners blinded to waveform analysis assessed patients for the presence of PEEP1 by inspection/palpation and auscultation. If either inspection/palpation or auscultation demonstrated PEEP1, it was said to be present by clinical exam. Clinicians with various levels of experience (attending, resident, student) made 503 observations of 71 patients. Sensitivity (SENS), specificity (SPEC), positive predictive value (PPV), negative predictive value (NPV), and likelihood ratios were determined for inspection/palpation, auscultation, and clinical exam. PEEP(i) was present during 69.8% of observations. SENS, SPEC, and PPV of clinical exam were 0.72, 0.91, and 0.95 respectively for the examiners as a whole. Likelihood ratio for PEEP(i) detection by clinical exam was 8.35. Attending intensivists displayed SPEC and PPV of 1.0. NPV was only 0.58 (likelihood ratio 0.31). We conclude that the clinical exam is very good for detecting PEEP(i) at all experience levels; and further, that the clinical exam is only modestly useful for ruling out PEEP(i), therefore, other tests should be used if PEEP(i) is not detected by clinical exam.