Ultrasonographic Assessment of Passive Cephalic Excursion of Diaphragm During Cough Expiration Predicts Cough Peak Flow in Healthy Adults.

Evaluation of cough strength is clinically important, especially for patients with neuromuscular disorders and before extubation of mechanically ventilated patients. The pressure gradient between the airway and thoracoabdominal cavities during the cough expiratory phase generates cough flow and passive cephalic movement of the diaphragm. We hypothesized that passive diaphragmatic cephalic excursion, peak velocity, or both during cough expiration might predict cough peak flow (CPF). This physiologic study investigated associations of CPF with simultaneously measured ultrasonographic indices in healthy adults during the cough expiratory phase.56 healthy adults participated in this study. Right hemidiaphragm excursion and peak velocity were measured with ultrasonography during voluntary cough expiration with maximum effort. CPF was simultaneously measured for all coughs along with the ultrasonographic measurements. A linear regression model was used to determine whether ultrasonographic indices predicted CPF.

Simple regression analysis showed significant associations between excursion and CPF in men and women (P < .001, beta coefficient 37.8, 95% CI 10.9 - 64.7, adjusted R² = 0.195 for men; P < .001, beta coefficient 46.1, 95% CI 22.3- 69.9, adjusted R² = 0.386 for women). A multiple regression model adjusted for age, height, and sex showed a significant association between CPF and excursion (P < .001, adjusted beta coefficient 38.32, 95% CI 21.20 -55.44, adjusted R² = 0.643). Simple regression analysis showed a significant association between diaphragmatic peak velocity and CPF only in women (P = .004, beta coefficient 5.07, 95% CI 1.81- 8.33, adjusted R² = 0.280 for women).

Passive cephalic excursion of the diaphragm during the cough expiratory phase significantly predicted CPF with maximum cough effort in healthy adults. Future studies should investigate the relationship between CPF and excursion in persons with respiratory and neuromuscular disorders.