Journal - Chest

Abstract :

In this prospective study, we measured the ST segments, heartrate-systolic BP product (RPP), respiratory rate to tidal volumeratio (RVR), and pulse oximetry saturations of patients in ourmedical/cardiac ICUs before and during weaning from mechanicalventilation. Ninety-three patients were enrolled with a meanage of 66.5±15.0 years (mean±SD), mean acute physiologyand chronic health evaluation (APACHE) II score of 16.0±6.9,and mean duration of mechanical ventilation of 5.2±8.6days. Forty-nine patients had coronary artery disease (CAD).Six of 93 patients (6.4%) experienced ECG evidence of ischemiaduring weaning. Five of these six had a precedent history ofCAD and four failed initial weaning attempts (22% of patientswith CAD who failed weaning). The RPP, for the group as a whole,increased significantly during weaning from 12.0±3.1 to13.4±4.0 mm Hg·bpm·103 (p<0.01). The rateto volume ratio did not change significantly during weaning,except in the subgroup of patients who failed to wean, in whomit increased from 98.4±45.2 to 124.9±54.9 bpm/L (p<0.05).Oxygenation also decreased significantly from 0.98±0.02to 0.96±0.03 and was significantly associated with weaningfailure (risk ratio [RR]=3.9; 95% confidence interval[CI]= 1.7 to 9.0). Thirty-seven patients failedthe initial weaning attempt. Cardiac ischemia (RR=1.8; 95% CI=1.0to 3.4) and an increased RVR (RR=1.7; 95% CI=0.9 to 3.4) tendedto increase the risk of weaning failure. Cardiac ischemia, althoughinfrequent (6%) in the general population of weaning medical/cardiacICU patients, should be considered in patients with CAD whofail to wean.