Use of continuous positive airway pressure reduces airway reactivity in adults with asthma

Abstract

Asthma is characterised by airway hyperreactivity, which is primarily treated with β-adrenergic bronchodilators and anti-inflammatory agents. However, mechanical strain during breathing is an important modulator of airway responsiveness and we have previously demonstrated in animal models that continuous positive airway pressure (CPAP) resulted in lower in vivo airway reactivity. We now evaluated whether using nocturnal CPAP decreased airway reactivity in clinically-stable adults with asthma. Adults with stable asthma and normal spirometry used nocturnal CPAP (8-10 cmH(2)O) or sham treatment (0-2 cmH(2)O) for 7 days. Spirometry and bronchial challenges were obtained before and after treatment. The primary outcome was the provocative concentration of methacholine causing a 20% fall in forced expiratory volume in 1 s (PC(20)). The CPAP group (n=16) had a significant decrease in airway reactivity (change in (Δ)logPC(20) 0.406, p<0.0017) while the sham group (n=9) had no significant change in airway reactivity (ΔlogPC(20) 0.003, p=0.9850). There was a significant difference in the change in airway reactivity for the CPAP versus the sham group (ΔlogPC(20) 0.41, p<0.043). Our findings indicate that chronic mechanical strain of the lungs produced using nocturnal CPAP for 7 days reduced airway reactivity in clinically stable asthmatics. Future studies of longer duration are required to determine whether CPAP can also decrease asthma symptoms and/or medication usage.

Trial registration: ClinicalTrials.gov NCT00592631.

FIGURE 1

Change in log-transformed provocative concentration of methacholine causing a 20% fall in forced expiratory volume in 1 s (PC₂₀) with treatment. logPC₂₀ increased (airway reactivity decreased) significantly with a) continuous positive airway pressure (CPAP) treatment (p<0.004), but not with b) sham treatment (p=0.988). The change in logPC₂₀ was significantly greater for the CPAP compared with the sham group (p<0.043). Solid lines represent individual subjects, and circles and dashed lines represent group means.

FIGURE 2

a, b) Change in Asthma Score with treatment. There were no significant changes in Asthma Score with a) continuous positive airway pressure (CPAP) treatment (p<0.147) or b) sham treatment (p=0.594). c, d) Change in forced expiratory volume in 1 s (FEV₁) with treatment. There were no significant changes in FEV₁ with c) CPAP treatment (p<0.567) or d) sham treatment (p=0.238). e, f) Change in exhaled nitric oxide (eNO) with treatment. There were no significant changes in eNO with e) CPAP treatment (p<0.326) or f) sham treatment (p=0.523). Solid lines represent individual subjects, and circles and dashed lines represent group means. % pred: % predicted.