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

Abstract

BACKGROUND: 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. METHODS: 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. RESULTS: 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 R 2 ‫؍‬ 0.195 for men; P < .001, beta coefficient 46.1, 95% CI 22.3-69.9, adjusted R 2 ‫؍‬ 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 R 2 ‫؍‬ 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 R 2 ‫؍‬ 0.280 for women). CONCLUSIONS: 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.

Ultrasonographic measurement of the diaphragm movement during cough and extubation outcomes

“…Our results suggest that cough inspiratory volume is important in generating adequate CPF and that PCED is therefore closely associated with CPF. The coefficients in the equation for predicting CPF with PCED in patients with endotracheal tubes in this study were significantly different from those for healthy adults [15], mostly because of the absence of glottic closure secondary to endotracheal tubes and the consequent absence of a "compressive phase" before cough expiration.…”

“…A CX50 ultrasound device (Philips, The Netherlands) was used to assess ultrasonographic indices of the diaphragm with a sector transducer (3.5 MHz). The transducer was positioned on the abdominal wall just below the lowest right rib, between the midaxillary line and mammillary line in the longitudinal scanning plane to the cephalic direction, with the liver as an acoustic window [12][13][14][15]. The angle of the transducer was adjusted so that the ultrasound beam was perpendicular to the posterior third of the right hemidiaphragm [16].…”

“…Because PCED and diaphragm peak velocity cannot be measured simultaneously, PCED was measured during the first cough, and diaphragm peak velocity was measured during the second cough. To measure PCED, the M-mode interrogation line was adjusted to ensure that it was perpendicular to the movement of the posterior one-third of the right hemidiaphragm [14,15]. PCED was measured on the vertical axis of the M-mode and was traced from the end of inspiration to the end of cough expiration (Figure 1).…”

“…PCED was measured on the vertical axis of the M-mode and was traced from the end of inspiration to the end of cough expiration (Figure 1). Peak velocity of the diaphragm was measured by placing the tissue Doppler imaging cursor at the posterior one-third of the right hemidiaphragm ( Figure 2) [15]. Simultaneous measurement of CPF was performed for both coughs by using the internal flow meter of the ventilator (PB840, Covidien, Mansfield, MA, USA) [17].…”

“…The pressure gradient between the thoracoabdominal cavity and airway during cough generates air flow to the mouth, as well as passive cephalic excursion of the diaphragm (PCED). We recently reported that PCED during the cough expiratory phase is a significant predictor of CPF in healthy adults [11]. Ultrasonographic measurement of cough strength in mechanically ventilated patients, when feasible, would not require special devices, such as a peak flow meter (which must be connected to the endotracheal tube), or a ventilator from which an accurate CPF value can be recorded.…”