A nocturnal decline of salivary pH associated with airway hyperresponsiveness in asthma

Salivary pH is associated with esophageal acid reflux and neutralization of
esophageal acid. In this study, we assessed the association between nocturnal decline of
salivary pH and airway hyperresponsiveness. Salivary pH was serially assessed in 9 patients
with mild asthma (7 men and 2 women ;mean age 33.3 years ;mean %predicted
FEV1.0 89.4%) and 10 healthy volunteers (6 men and 4 women ; mean age 31.2 years) using
a pH indicator tape. The buffering capacity of saliva was defined as the median effective
dose (ED50) for acidification of saliva with 0.01 N HCl, and airway responsiveness was
defined as the dose of methacholine producing a 35% fall in Grs (PD35-Grs). There was a
significant correlation between the values obtained from the pH indicator tape and those
obtained from the electrometric pH meter. Using the indicator tape for sequential monitoring,
we observed a nocturnal fall (pH) in salivary pH in all subjects. A significant correlation
was found between airway hyperresponsiveness (PD35-Grs) and eitherpH or ED50
in mildly asthmatic patients. Vagal reflux dysfunction might contribute to nocturnal
salivary pH as well as to airway hyperresponsiveness in mild asthmatics.

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