Effect of the Inspiratory Method and Timing of Voluntary Cough on Peak Cough Flow

OBJECTIVE: To define the effect of the inspiratory method and cough timing on peak cough flow (PCF). METHODS: We investigated the effect of measurement conditions on PCF in healthy subjects (n=10). We then compared obstructive and restrictive pulmonary diseases (n=20) to assess for similar results in respiratory diseases. The PCF was measured under four conditions: before coughing, without maneuver 1 or with maneuver 2 a temporary respiratory pause (4–6 seconds) after rapid inspiration, and without maneuver 3 or with maneuver 4 a temporary respiratory pause after slow inspiration. After the measurements were completed, the PCF between the four conditions was compared for each subject group, and the effect size was calculated. RESULTS: PCF of maneuvers 1 and 3 were significantly higher than maneuver 4 in healthy subjects (476.34±102.05 L/min and 463.44±107.14 L/min vs. 429.54±116.83 L/min, p<0.01 and p<0.05, respectively) and patients with restrictive pulmonary disease (381.96±145.31 L/min, 354.60±157.36 L/min vs. 296.94±137.49 L/min, p<0.01 and p<0.05, respectively). In obstructive pulmonary disease, maneuver 1 was significantly higher than maneuver 4 (327.42±154.73 L/min vs. 279.48±141.10 L/min, p<0.05). The largest effect sizes were shown by maneuvers 4 and 1. CONCLUSION: PCF depends on changes in inspiratory speed before coughing and on temporary respiratory pauses after maximal inspiration. It will become necessary to unify the measurement methods for coughing strength and present appropriate coughing methods.