Designing and Validation an Experimental Protocol to Induce Airway Narrowing in Older Adults with and without Asthma

Background: Persons with asthma may experience excessive airway narrowing due to exercise or exposure to cold air, worsening their daily functionality. Exercise has several benefits for asthma control, but it may induce airway narrowing in some persons with asthma. When combined with cold temperatures, it introduces another layer of challenges. Therefore, managing this interaction is crucial to increase the quality of life in individuals with asthma. The purpose of this study was to develop a reliable experimental protocol to assess the effects of exercise and cold air on airway narrowing in adults with asthma, in a controlled and safe environment. Methods: This study was a randomized cross-over study in adults with and without asthma. Participants underwent a protocol involving a 10-minute seated rest, followed by a 10-minute cycling on a stationary bike in different temperatures of 0, 10, or 20°C. The sequence of room temperatures was randomized and there was a 30-minute interval for recovery between each temperature transition. In each temperature, to measure lung function and respiratory symptoms, oscillometry and a questionnaire were used at 0 minute of sitting (baseline), after 10 minutes of sitting or before starting biking (pre-exercise), and after 10 minutes of biking (post-exercise). At each room temperature, the changes in airway mechanics and asthma symptoms among baseline, pre-exercise, and post-exercise were compared with one-way repeated measures ANOVA or Friedman Rank Test. Results: A total of 23 persons with asthma (11 females, age: 56.3 ± 10.9 years, BMI: 27.4 ± 5.7 kg/m2) and 6 healthy subjects (3 females, age: 61.8 ± 9.1 years, BMI: 28.5 ± 3.1 kg/m2) were enrolled in the study. Cold temperature of 0°C induced airway narrowing in those with and without asthma after 10 and 20 minutes respectively. Exercise intervention had significant changes in airway narrowing in participants with asthma in the range of 10-20°C. Our results showed that in asthma, changes in subjective respiratory symptoms were due to both cold temperatures of 0 and 10°C and exercise in the 0-20°C range. Respiratory symptoms were not noticed among the healthy participants. Conclusion: In conclusion, our findings suggest that exposure to cold temperatures of 0°C could serve as a reliable method in the experimental protocol for inducing airway narrowing in asthma. The impact of exercise on airway narrowing was more variable among participants. Understanding these triggers in the experimental protocol is essential for the successful management of asthma in future studies.