Enforced mouth breathing decreases lung function in mild asthmatics.
Level 3 - non-randomized controlled study
Small non-randomized or unstated-randomization crossover physiological study
PubMed 18494947 · doi:10.1111/j.1440-1843.2008.01300.x
What was done
Eight asymptomatic volunteers with mild asthma completed two 1-hour resting breathing protocols on separate days: nasal-only breathing (lips sealed with tape) and oral-only breathing (nose clip applied). Lung function (% predicted FEV1) was measured at baseline and every 10 minutes for 1 hour using standard spirometry. Perceived difficulty in breathing was assessed at the end of each session using a Borg scale.
What was found
Baseline FEV1 was similar on nasal (101.2 ± 3.8% predicted) and oral days (102.7 ± 3.9% predicted; P > 0.3). At 60 minutes, FEV1 on the oral day (96.5 ± 4.1% predicted) was significantly lower than on the nasal day (101.0 ± 3.5% predicted; P < 0.009). FEV1 remained stable during nasal breathing (P > 0.3) but fell progressively during oral breathing (slope = -0.06 ± 0.01% FEV1/min, P < 0.0001). Three of eight participants developed coughing or wheezing at the end of the oral breathing day, while none did on the nasal day. Difficulty breathing in was rated higher after oral breathing (1.5 ± 0.4 arbitrary units) than nasal breathing (0.4 ± 0.3 arbitrary units; P < 0.05).
Why it matters
This study shows that bypassing the nasal airway at rest induces measurable bronchoconstriction and asthma symptoms in mild asthmatics, suggesting mouth breathing may trigger or worsen asthma exacerbations.
Limits
The sample size is very small (n = 8). The abstract does not report whether the order of exposure days was randomized, nor does it report room air temperature or humidity controls. Findings in resting mild asthmatics may not generalize to moderate-to-severe disease or dynamic everyday conditions.
Cited by
- partial Nasal breathing increases oxygen delivery to the lungs compared to mouth breathing.