The value of cough peak flow in the assessment of cough efficacy in neuromuscular patients. A cross sectional study

Abstract

Background: Cough efficacy assessment is of clinical relevance in neuromuscular patients. Tests of varying complexity and invasiveness, such as cough peak flow (CPF), maximal expiratory pressure (PEmax) and gastric pressure during cough (Cough Pgas) are routinely available.

Aim: To assess the value of CPF, PEmax and Cough Pgas in the detection of ineffective cough in patients suffering from neuromuscular diseases.

Design: Prospective observational study.

Setting: Outpatient laboratory for respiratory muscle function assessment.

Population: Forty-nine patients with neuromuscular diseases (25 F, age 50 ± 15 years).

Methods: Each patient performed spirometry, CPF, PEmax, Cough Pgas and maximal inspiratory pressure (PImax). Normal values for each test were determined from published and in-house lab data.

Results: In all patients, vital capacity ranged from 46 to 119% of pred. Twenty seven percent of patients resulted under the lower normal limit of CPF and this percentage was significantly lower as compared to that of PEmax and Cough Pgas (51% and 53% respectively, P=0.013). Combining all three tests, the percentage of patients resulting below normal was 22% (P=0.638, as compared to CPF results alone). Additionally, CPF correlated significantly with PImax, PEmax, and Cough Pgas (P<0.01 for each correlation) and by multiple regression analysis PImax and PEmax contributed 65% of CPF variance.

Conclusion: Our study shows that in neuromuscular patients, PEmax and Cough Pgas values may overdiagnose an ineffective cough. CPF, a non invasive and easy to perform test, is a global measure of voluntary cough. CLINICAL REHABILITATION SETTING:CPF may be relevant in the routine evaluation of patients with neuromuscular diseases, both in research and in rehabilitation settings.