Study objectives: To measure route of breathing in
chronic asthmatic patients during and after an acute severe
Patients or participants: Thirteen
asthmatic patients were studied during hospital admission for acute
asthma and, in 9 patients, again when asymptomatic. Nine healthy
subjects were also studied.
route of breathing was qualitatively assessed using oral and nasal
thermistor probes, and was then quantified using a dual compartment
face mask with attached pneumotachographs.
results: All asthmatic patients had severe bronchoconstriction
initially (FEV1, 46 ± 3% of predicted) that had
resolved at follow-up (FEV1, 91 ± 6% of predicted). No
healthy subject had evidence of bronchoconstriction (FEV1,
102 ± 5% of predicted). During acute asthma, 11 asthmatics were
spontaneously breathing oronasally, as assessed using thermistor
probes, while all 13 breathed oronasally via face mask. When assessed
using 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, all breathed nasally only via face mask.
Conclusions: Thus, when asymptomatic and at rest, asthmatic
patients breathe exclusively via the nose. However, during acute
exacerbations of asthma, these patients switch to oronasal breathing.
Unlike healthy subjects, chronic asthmatic patients also switch 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 factor that may
contribute to the pathogenesis of their asthma.