Endotracheal tube cuff pressure change: Proof of concept for a novel approach to objective cough assessment in intubated critically ill patients

Cough strength assessment aids in predicting extubation failure. Peak expiratory flow rate during cough manoeuvre (CPF) is the gold-standard tool and flow rates of <60l/min suggest risk of failed extubation. We aimed to assess endotracheal tube cuff pressure change (ΔPcuff) as a novel method of objective cough strength assessment in intubated patients considered for extubation.Paired measurements of CPF and ΔPcuff were sampled during cough manoeuvres by intubated recovering critically ill patients. Spearman's correlation was used to assess agreement between the variables. Categorical data and receiver operating characteristic (ROC) curve analysis were undertaken to assess discriminating ability of ΔPcuff to identify low CPF.In total, 42 patients yielded 81 paired measurements. Paired samples with the highest CPF per patient had a correlation coefficient of 0.74. The composite of all samples had a correlation coefficient of 0.77. Regression analysis showed CPF=60l/min equates to ΔPcuff=28cmH2O with categorical analysis using these cut-offs showing significant dependence between the variables (p = 0.000001). ROC curve analysis identified an area under the curve (AUC) of 0.9 [95% CI (0.84, 0.97)], with optimal sensitivity and specificity of ΔPcuff at 20cmH2O.We identified a good correlation between CPF and ΔPcuff. Our research showed that overall discriminating ability of ΔPcuff in identifying CPF <60l/min was excellent. Further studies, looking at ΔPcuff and extubation outcomes are required to establish clinical utility.