Degree of convexity calculated from expiratory flow-volume curves for identifying airway obstruction in nonsedated and nonparalyzed ventilated patients.

The predictive performance of applying the degree of convexity in expiratory flow-volume (EFV) curves to detect airway obstruction in ventilated patients has yet to be investigated. We enrolled 33 nonsedated and nonparalyzed mechanically ventilated patients and found that the degree of convexity had a significant negative correlation with FEV1% predicted. The mean degree of convexity in EFV curves in the chronic obstructive pulmonary disease (COPD) group (n = 18) was significantly higher than that in the non-COPD group (n = 15; 26.37 % ± 11.94 % vs. 17.24 % ± 10.98 %, p = 0.030) at a tidal volume of 12 mL/kg IBW. A degree of convexity in the EFV curve > 16.75 at a tidal volume of 12 mL/kg IBW effectively differentiated COPD from non-COPD (AUC = 0.700, sensitivity = 77.8 %, specificity = 53.3 %, p = 0.051). The degree of convexity calculated from EFV curves may help physicians to identify ventilated patients with airway obstruction.

Impact and predictors of prolonged chest tube duration in mechanically ventilated patients with acquired pneumothorax.

BACKGROUND: Prolonged chest tube duration is less well studied in patients who are supported by mechanical ventilation and have acquired pneumothorax. We investigated the impact of prolonged chest tube duration on patient outcomes and the risk factors associated with prolonged chest tube duration. METHODS: This retrospective observational study included 106 ventilated subjects who had been treated with thoracostomy for pneumothorax between May 2004 and December 2011. We analyzed 61 subjects and 63 events. The subjects were divided into a prolonged chest tube duration group (> 18 d) and a non-prolonged group (≤ 18 d). RESULTS: Subjects with prolonged chest tube duration had significantly higher ICU mortality (P = .006), longer ICU stay (P = .001), longer hospitalization (P = .004), longer mechanical ventilation after development of pneumothorax (P = .003), higher maximum peak inspiratory pressure (P = .03), and a higher rate of surgical emphysema (P = .009). High peak inspiratory pressure and surgical emphysema remained independent predictors of prolonged chest tube duration after multivariate logistic regression analysis. The probability of chest tube removal within 28 days was significantly lower in subjects with both high peak inspiratory pressure and surgical emphysema, compared to subjects without any risk factors (log rank P = .001). CONCLUSIONS: High peak inspiratory pressure and surgical emphysema are independent predictors of prolonged chest tube duration and negatively impact clinical outcomes in this patient group. These findings may provide information for better chest tube management.