Predictors of dyspnea intensity in asthma.

Predictors of dyspnea were studied during induced airflow obstruction or cough in an attempt to increase understanding of factors related to observed variability in the descriptions of the experience of dyspnea. Thirty-one adult subjects with asthma participated in a 2-day protocol using a laboratory analog of asthma. Air flow obstruction and dyspnea were induced on Day 1 with inhalations of methacholine in doubling concentrations from 0.063 to 2.0 mg/ml. Cough was induced on Day 2 with inhalations of 3% sodium gluconate solution. Dyspnea was assessed on both days by a visual analog technique. The magnitude of dyspnea was not related to airway caliber. There was a significant negative relationship between age and magnitude of dyspnea and between cigarette pack years and dyspnea intensity. Dyspnea at baseline was positively related to dyspnea intensity during induced bronchoconstriction. Dyspnea during cough was not related to airway caliber, but there was a significant difference between males and females in the intensity of dyspnea at cough threshold. These findings may explain some of the variability observed in the experience of dyspnea in asthma.