Aeroallergen‐induced hypoxic bradycardia in spontaneously breathing house dust mite‐sensitive nonhuman primates

Abstract

RATIONALEA small number of house dust mite (HDM)‐sensitive nonhuman primates (NHP) exhibit life‐threatening bradycardia after aero‐HDM challenge. Retrospective analysis was performed to elucidate conditions associated with the adverse cardiac response.METHODSData recorded for 71 NHP over 4 years was screened for a >25% decrease in HR and minimum HR <100 bpm following HDM challenge. Prior to data acquisition, NHP were anesthetized, intubated, and instrumented to record SpO2 & HR, lung resistance (RL), and dynamic compliance (Cdyn).RESULTSHypoxic bradycardia was observed in 10 of 71 NHP. It was associated with airway sensitivity to HDM and was preceded by rapid‐shallow breathing and often apnea. HR decreased 50% to 76±6 bpm and was associated with an SpO2 of 71±4%, increase in RL of 139±37%, and decrease in Cdyn of 59±5%. Bradycardia was also observed during methacholine provocation performed 24 hours after HDM challenge. Bradycardia was reversed by mechanical ventilation or atropine.CONCLUSIONSHypoxic bradycardia during respiratory stasis has been described in humans and canines. Our data indicate that HDM‐allergy can lower O2 and tidal volume thresholds for the reflex in susceptible subjects.