Autonomic dysregulation: a mechanism of asthma death

To the Editor: Therapeutic advances in the management of asthma have led to a gradual but sustained reduction in mortality [1, 2]. However, the death of otherwise healthy young individuals remains a tragic and all too frequent occurrence. The unheralded demise of two of our patients with previously minimally troublesome asthma led us to reconsider the mode of death in such patients. Numerous studies and retrospective reports have attributed such mortality to preventable factors such as inadequate severity assessment, discontinuity of medical care, poor concordance to prescribed therapies and poor management of acute asthma exacerbations [3, 4]; others have attributed fatalities to significant behavioural, socioeconomic or psychosocial factors including smoking, denial, depression and alcohol abuse [1, 5, 6]. Whilst these associations are undeniably important they do not adequately explain the observed clinical picture of precipitous deterioration, loss of consciousness, and death. Robin et al . [7] reported two patients with an abrupt demise, one during a telephone conversation and with no prior asthma-related symptoms. Grubb et al . [8] followed a teenage boy with a history of long-standing asthma after repeated near fatal asthma episodes requiring resuscitation. Our similar experience of two unexpected fatalities caused us to question bronchoconstriction as the primary mode of death. Others have suggested that vasovagally-induced bradycardia results in a potentially lethal syncope in predisposed individuals. We have sought to test this hypothesis in subjects from our asthma clinic who have a history of unconsciousness precipitated by exacerbations using the simulated diving reflex of facial immersion to replicate such events [9]. Participants were recruited through the Academic and Outpatient Respiratory department at Castle Hill Hospital (Cottingham, UK) over a 12-month period. Subjects were excluded if they had significant cardiovascular …