Objective: To study the result of respiratory multiple index(compliance, respiratory rate, oxygenation, pressure, CROP) in predicting weaning from mechanical ventilation in patients with acute exacerbation of chronic obstructive pulmonary disease (AECOPD).
Methods: A prospective study was conducted. Two hundred and fifteen patients weaning from mechanical ventilation with AECOPD in intensive care unit (ICU) of five tertiary hospitals from September 2010 to October 2012 were enrolled. All of the AECOPD patients were troubled with respiratory failure and received non-invasive mechanical ventilation for more than 24 hours. They were conscious and cooperative at the time of extubation, and passed the spontaneous breathing trial (SBT) for 30 minutes. Before weaning, the maximal inspiratory pressure (PImax), the peak airway pressure (Ppeak), the total positive end expiratory pressure (PEEPtot), tidal volume (VT) and respiratory frequency (f) were recorded; the arterial partial pressure of oxygen (PaO₂) and arterial partial pressure of carbon dioxide (PaCO₂) were detected; the effective compliance of the respiratory system (Crs) and alveolar oxygen pressure(PAO₂) were calculated. The above indexes were substituted into the formula: CROP= Crs × 1/f × PaO₂/PAO₂× PImax to get the value of CROP. Successful weaning from mechanical ventilation was defined if there was no indication for intubation within 72 hours. The receiver operating characteristic curve (ROC curve) was drawn to analyze the predict value of CROP on result of weaning from mechanical ventilation in patients with AECOPD.
Results: In 215 patients, 182 patients successfully weaned from mechanical ventilation, and 33 failed. There were no significant differences in gender, age and the acute physiology and chronic health evaluation II (APACHEII) score between the successfully weaned patients and the failed. Before weaning from mechanical ventilation, PaCO₂ in failed group was significantly higher than that in successful group (60.69 ± 10.47 mm Hg vs. 51.24 ± 8.81 mm Hg, P<0.05), the CROP was significantly lowered (10.286 ± 1.392 ml × breath⁻¹ ×min⁻¹ vs. 58.746 ± 7.283 ml×breath⁻¹×min⁻¹, P<0.01), and the duration of mechanical ventilation was prolonged (10.28 ± 3.94 days vs. 6.21 ± 2.87 days, P<0.05). The best critical value of CROP which could predict the result of weaning from mechanical ventilation was 13.521 ml×breath⁻¹×min⁻¹. CROP≥ 13.521 ml×breath⁻¹×min⁻¹ had a specificity of 91.9% and sensitivity of 87.9% in predicting extubation succeed. The positive predicted value was 0.97, and the negative predicted value was 0.58; Odds ratio (OR)<1, which confirmed that CROP was a strong and independent predictor of extubation.
Conclusions: For the AECOPD patients received mechanical ventilation, most extubation parameter was limited. Complex parameter of CROP has higher specificity and sensitivity, and has important value in predicting extubation outcome. When CROP ≥ 13.521 ml×breath⁻¹×min⁻¹, the successful rate is high, otherwise the rate is low.