Exercise-induced bronchoconstriction and bronchodilation: investigating the effects of age, sex, airflow limitation and FEV1.

Exercise-induced bronchoconstriction (EIBc) is a recognised response to exercise in asthmatic subjects and athletes but is less well understood in an unselected broad population. Exercise-induced bronchodilation (EIBd) has received even less attention. The objective of this study was to investigate the effects of age, sex, forced expiratory volume in 1 s (FEV1) and airflow limitation (FEV1/forced vital capacity (FVC) <0.7) on the prevalence of EIBc and EIBd.This was a retrospective study based on incremental cardiopulmonary exercise testing on cycle ergometry to symptom limitation performed between 1988 and 2012. FEV1 was measured before and 10 min after exercise. EIBc was defined as a percentage fall in FEV1 post-exercise below the 5th percentile, while EIBd was defined as a percentage increase in FEV1 above the 95th percentile.35 258 subjects aged 6-95 years were included in the study (mean age 53 years, 60% male) and 10.3% had airflow limitation (FEV1/FVC <0.7). The lowest 5% of subjects demonstrated a ≥7.6% fall in FEV1 post-exercise (EIBc), while the highest 5% demonstrated a >11% increase in FEV1 post-exercise (EIBd). The probability of both EIBc and EIBd increased with age and was highest in females across all ages (OR 1.76, 95% CI 1.60-1.94; p<0.0001). The probability of EIBc increased as FEV1 % pred declined (<40%: OR 4.38, 95% CI 3.04-6.31; p<0.0001), with a >2-fold increased likelihood in females (OR 2.31, 95% CI 1.71-3.11; p<0.0001), with a trend with airflow limitation (p=0.06). The probability of EIBd increased as FEV1 % pred declined, in the presence of airflow limitation (OR 1.55, 95% CI 1.24-1.95; p=0.0001), but sex had no effect.EIBc and EIBd can be demonstrated at the population level, and are influenced by age, sex, FEV1 % pred and airflow limitation.

The Impact of beta blockade on the cardio-respiratory system and symptoms during exercise.

BACKGROUND: Beta blockers prolong life in patients with cardiovascular diseases. Negative chronotropic and inotropic effects carry the potential to adversely effect peripheral skeletal and airway smooth muscle contributing to further fatigue, dyspnea and exercise intolerance. RESEARCH QUESTIONS: Do beta-blockers reduce maximal power output (MPO), VO2 max, cardiorespiratory responses, increase the perceived effort required to cycle and breath during cardiopulmonary exercise tests (CPET) and limit the capacity to exercise? METHODS: Retrospective observational study of subjects performing CPET to capacity from 1988 to 2012. Subjects with and without beta-blockers were compared: baseline physiological characteristics, MPO, VO2 max, heart rate max, ventilation responses and perceived exertion required to cycle and breathe (modified Borg scale). Forward stepwise linear additive regression was performed with MPO as the dependent factor with height, age, gender, muscle strength, FEV1 and DLCO as independent contributors. RESULTS: 42,771 subjects were included 7,787 were receiving beta-blocker [mean age 61 yrs, BMI 28.40 kg/m2, 9% airflow obstruction (FEV1/FVC<0.7)] and 34,984 were not [mean age 51yrs, BMI 27.40 kg/m2, 11% airflow obstruction]. Heart rate was lower by 18.2% (95% C.I. 18.15-18.38) (p<0.0001) while Oxygen pulse (VO2/HR) was higher by 19.5% (95% C.I. 19.3-19.7) in those receiving beta blockers. Maximum power output (MPO) was 3.3% lower in those taking beta-blockers. The perceived effort required to cycle and breathe (mBorg) was 8% lower in those taking beta-blockers. INTERPRETATION: Increases in oxygen pulse minimize the reduction in exercise intolerance and symptom handicap associated with beta-blockers.