Research Paper Title

Isolated Small Airway Dysfunction and Ventilatory Response to Cardiopulmonary Exercise Testing.

Background

The effect of isolated small airway dysfunction (SAD) on exercise remains incompletely characterised.

The researchers sought to quantify the relationship between isolated SAD, identified with lung testing, and the respiratory response to exercise.

Methods

The researchers conducted a prospective evaluation of service members with new-onset dyspnea.

All subjects underwent plethysmography, diffusing capacity of the lung for carbon monoxide (DLCO), impulse oscillometry, high-resolution computed tomography (HRCT), and cardiopulmonary exercise testing (CPET).

In subjects with normal basic spirometry, DLCO, and HRCT, SAD measures were analysed for associations with ventilatory parameters at submaximal exercise and at maximal exercise during CPET.

Results

The researchers enrolled 121 subjects with normal basic spirometry (ie, FEV1, FVC, and FEV1/FVC), DLCO, and HRCT.

Mean age and body mass index were 37.4 ± 8.8 y and 28.4 ± 3.8 kg/m2, respectively, and 110 (90.9%) subjects were male.

The prevalence of SAD varied from 2.5% to 28.8% depending on whether FEV3/FVC, FEF25-75%, residual volume/total lung capacity, and R5-R20 were used to identify SAD.

Agreement on abnormal SAD across tests was poor (kappa = -0.03 to 0.07). R5-R20 abnormalities were related to higher minute ventilation (V̇E) and higher V̇E/maximum voluntary ventilation (MVV) during submaximal exercise and to lower V̇O2 during maximal exercise.

After adjustment for differences at baseline, there remained a trend toward a relationship between R5-R20 and an elevated V̇E/MVV during submaximal exercise (β = 0.04, 95% CI -0.01 to 0.09, P = 0.099), but there was no significant association with V̇E during submaximal exercise or with V̇O2 during maximal exercise.

No other SAD measures showed a relationship with ventilatory parameters.

Conclusions

In 121 subjects with normal basic spirometry, DLCO, and HRCT, the researchers found poor agreement across tests used to detect SAD.

Among young, healthy service members with postdeployment dyspnea, SAD as identified by lung function testing does not predict changes in the ventilatory response to exercise.

Reference

Holley, A.B., Mabe, D.L., Hunninghake, J.C., Collen, J.F., Walter, R.J., Sherner, J.H., Huprikar, N.A. & Morris, M.J. (2020) Isolated Small Airway Dysfunction and Ventilatory Response to Cardiopulmonary Exercise Testing. Respiratory Care. pii: respcare.07424. doi: 10.4187/respcare.07424. [Epub ahead of print].