Involuntary cough strength and extubation outcomes for patients in an ICU

Abstract

Background: Removing the artificial airway is the last step in the mechanical ventilation withdrawal process. In order to assess cough effectiveness, a critical component of this process, we evaluated the involuntary cough peak flow (CPFi) to predict the extubation outcome for patients weaned from mechanical ventilation in ICUs.

Methods: One hundred fifty patients were weaned from ventilators, passed a spontaneous breathing trial (SBT), and were judged by their physician to be ready for extubation in the Tri-Service General Hospital ICUs from February 2003 to July 2003. CPFi was induced by 2 mL of normal saline solution at the end of inspiration and measured using a hand-held respiratory mechanics monitor. All patients were then extubated.

Results: Of 150 enrolled patients for this study, 118 (78.7%) had successful extubation and 32 (21.3%) failed. In the univariate analysis, there were higher Acute Physiology and Chronic Health Evaluation (APACHE) II scores (16.0 vs 18.5, P = .018), less negative maximum inspiratory pressure (-45.0 vs -39.0, P = .010), lower cough peak flows (CPFs) (74.0 vs 42.0 L/min, P < .001), longer postextubation hospital stays (15.0 vs 31.5 days, P < .001), and longer postextubation ICU stays (1.0 vs 9.5 days, P < .001) in the extubation failures compared with the extubation successes. In the multivariate analysis, we found that a higher APACHE II score and a lower CPF were related to increasing risk of extubation failure (odds ratio [OR] = 1.13; 95% CI, 1.03-1.25; and OR = 0.95; 95% CI, 0.93-0.98, respectively). The receiver operator characteristic curve cutoff point for CPF was 58.5 L/min, with a sensitivity of 78.8% and specificity of 78.1%.

Conclusions: CPFi as an indication of cough reflex has the potential to predict successful extubation in patients who pass an SBT.