Route of breathing in patients with asthma

Study objectives: To measure route of breathing in chronic asthmatic patien ts during and after an acute severe exacerbation. Patients or participants: Thirteen asthmatic patients were studied during h ospital admission for acute asthma and, in 9 patients, again when asymptoma tic. Nine healthy subjects were also studied, Interventions: Spontaneous route of breathing was qualitatively assessed us ing oral and nasal thermistor probes, and was then quantified using a dual compartment face mask with attached pneumotachographs. Measurements and results: All asthmatic patients had severe bronchoconstric tion initially (FEV1, 46 +/- 3% of predicted) that had resolved at follow-u p (FEV1, 91 +/- 6% of predicted). No healthy subject had evidence of bronch oconstriction (FEV1, 102 +/- 5% of predicted). During acute asthma, 11 asth matics were spontaneously breathing oronasally, as assessed using thermisto r probes, while all 13 breathed oronasally via face mask. When assessed usi ng thermistor probes, seven of nine asymptomatic asthmatic patients studied were breathing exclusively via the nose; however, all breathed oronasally via face mask. In contrast, while eight of nine healthy subjects were also breathing exclusively via the nose when assessed using thermistor probes, a ll breathed nasally only via face mask. Conclusions: Thus, when asymptomatic and at rest, asthmatic patients breath e exclusively via the nose. However, during acute exacerbations of asthma, these patients switch to oronasal breathing. Unlike healthy subjects, chron ic asthmatic patients also snitch to oronasal breathing when wearing a face mask, irrespective of the degree of bronchoconstriction. We speculate that asthmatics may have an increased tendency to switch to oral breathing, a f actor that may contribute to the pathogenesis of their asthma.