Airway distensibility in healthy young and elderly adults

PURPOSE: In clinical practice, it is assumed that lung volume history influences maximal expiratory airflow (MEF) similarly across all ages. However, age-related changes in lung and airway structure suggest that a deep lung inflation (DI) may not elicit a bronchodilatory response in older adults. This study aims to clarify the unknown effect of lung stretch on airway caliber and airflow in elderly persons. We hypothesize that the DI preceding a maximal forced expiration (MFE) will enhance MEF in young adults but will reduce MEF in older adults. METHODS: Healthy young (n=14; age, 32.0 ± 1.6 yrs; BMI, 25.3 ± 0.8 kg/m 2 ) and healthy elderly adults with normal pulmonary function (n=5; age, 68.8 ± 1.5 yrs; BMI, 28.0 ± 2.1 kg/m 2 ) completed an incremental methacholine challenge test (MCT) using the one-minute tidal breathing protocol. The MCT was administered at doubling increments, starting at a concentration of 0.03125mg/mL, until forced expiratory volume in 1 second (FEV1) decreased by 20% or a maximum concentration of 32mg/mL was reached. Measurements from a respiratory maneuver consisting of: A) forced expiration from resting end-inspiratory lung volume (i.e., partial forced expiration [PFE]), B) inhalation to total lung capacity (TLC), C) MFE, D) inhalation to TLC were performed to determine the effect of a DI on MEF. The ratio of expiratory airflow between the maximal and partial forced expiration (M:P) was measured at a constant lung volume of 40% of the MFE (M40:P40). RESULTS: FEV1 decreased significantly after the MCT in both the young (3.39 ± 0.18 vs. 2.74 ± 0.19 L for pre- vs. post-MCT, respectively; P < 0.01) and the elderly (2.73 ± 0.30 vs. 2.32 ± 0.31L for pre- vs. post-MCT, respectively; P < 0.01) group. Baseline M40:P40 was not different between the two groups (1.05 ± 0.05 vs. 0.89 ± 0.08 young vs. elderly, respectively). In young participants, M40:P40 increased after MCT (1.05 ± 0.05 vs. 1.30 ± 0.06 pre- vs. post-MCT, respectively; P < 0.01). However, in elderly adults, M40:P40 was not affected by MCT (0.89 ± 0.08 vs. 0.98 ± 0.11 pre- vs. post-MCT, respectively; P > 0.05). Post-MCT challenge M40:P40 was significantly different in the young and elderly subjects (1.30 ± 0.06 vs. 0.98 ± 0.11 young vs. elderly, respectively; P < 0.05). CONCLUSIONS: A significant increase in M40:P40 was observed from pre- to post-bronchoconstriction following MCT administration in young adults, but not in older adults. Furthermore, post-MCT values of M40:P40 differed significantly between the young and elderly groups. We conclude that the airway dilatory effect of a DI is diminished in elderly adults. RESEARCH FUNDING: National Institutes of Health, National Institute on Aging: 1R21AG083488 This abstract was presented at the American Physiology Summit 2026 and is only available in HTML format. There is no downloadable file or PDF version. The Physiology editorial board was not involved in the peer review process.