Prognostic value of mouth occlusion pressure in patients with chronic ventilatory failure

Mouth occlusion pressure measurement is widely used for assessment of respiratory muscle function, particularly in patients with respiratory failure. However, its predictive value for long-term survival remains largely unexplored.

In 464 patients with chronic hypercapnic respiratory failure (CHRF) due to various underlying disorders and receiving non-invasive ventilation (NIV), maximal inspiratory mouth pressure (PI(max)), mouth occlusion pressure at 100 ms during quiet breathing (P(0.1)) and the ratio P(0.1)/PI(max) were assessed prior to and after treatment including NIV. Baseline data and changes at follow-up were used to evaluate their predictive value for long-term survival.

Overall, median (quartiles) P(0.1) was 177.0 (109.2;287.0) %pred, PI(max) 35.0 (24.0;47.0) %pred, and P(0.1)/PI(max) 564.0 (275.7;1082.3) %pred. In multivariate analyses, P(0.1) was related to airflow obstruction, lung hyperinflation, haemoglobin (Hb) and leukocytes, and PI(max) to airflow obstruction and hyperinflation (p<0.05 each). All-cause mortality during follow-up (median 31.6 months) was 31.5%. Survival was associated with age, body-mass index (BMI), lung function, leukocytes, Hb, PI(max), P(0.1) and P(0.1)/PI(max) (p<0.01 each, univariate). Among these multivariate Cox regression identified age, BMI, FEV(1), leukocytes and P(0.1)/PI(max) as independent predictors (p<0.05 each). Furthermore, the decrease of P(0.1)/PI(max) at follow-up was associated with improved survival in patients with high baseline P(0.1)/PI(max) (>50th or 75th percentile; p<0.05).

In patients with CHRF and current NIV therapy, P(0.1)/PI(max) was an independent predictor of long-term survival, in addition to previously established risk factors. Moreover, a decrease in P(0.1)/PI(max) after treatment including NIV was associated with an improved survival in patients with high baseline P(0.1)/PI(max) values.