Abstract

OBJECTIVES: The negative inspiratory force (NIF) has been used to help clinicians predict a patient's likelihood of successful liberation from mechanical ventilation (MV). However, the utility of the traditional threshold of ≤-30 cmH (2)O may not be appropriate for patients with chronic obstructive pulmonary disease (COPD). This study aims to define the optimal predictive NIF threshold for COPD patients. METHODS: A prospective-observational multi-center study was conducted in intensive care units of six academic medical centers. All patients had COPD and were intubated for hypercapnic respiratory failure. The process of weaning from MV was conducted according to the defined hospital protocol. NIF was measured after 120 min of spontaneous breathing trial (SBT). The sensitivity, specificity, positive, and negative predictive value (PPV, NPV), positive and negative likelihood ratios (LR+, LR-) were calculated, and the diagnostic accuracy recorded. RESULTS: A total of 90 patients with COPD (39 males and 51 females) were included. Of these, 43 patients (47.8) were successfully extubated whereas 47 patients (52.2) failed SBT or required re-intubation (P = 0.654). The threshold value of ≤-25 cmH(2)O offered the optimal performance in COPD patients: area under the receiver operating characteristic (ROC) curves ROC curves 0.836, sensitivity 95.0, specificity 86.0, PPV 84.4, and NPV 95.6., LR+ 6.79, LR- 0.06, and the diagnostic accuracy 90.7. CONCLUSIONS: In mechanically ventilated COPD patients with hypercapnic respiratory failure, the NIF threshold of ≤-25 cmH(2)O was a moderate-to-good predictor for successful ventilator liberation, and outperforms the traditional threshold of ≤-30 cmH(2)O.