EFFECT OF A 2ND LARYNGEAL STIMULATION DURING RECOVERY FROM THE LARYNGEAL CHEMOREFLEX

The laryngeal chemoreflex is a potential mechanism for sudden infant d eath, In experimental protocols in which a full recovery is allowed be tween stimuli, no laryngeal chemoreflex responses result in a fatal ou tcome, In the clinical situation there are no controls to prevent repe ated laryngeal stimulation before a full recovery, The effect of a lar yngeal stimulus applied during or soon after a laryngeal chemoreflex-i nduced apnea was investigated, Eighteen piglets were divided into grou ps aged 10 to 12 days, 17 to 21 days, and 32 to 36 days, Laryngeal sti mulation was performed under normoxic conditions with water applied to the mucosa, Baseline respiratory and cardiovascular response data wer e measured, After recovery an initial stimulation was applied, followe d by a second stimulation during the apnea or 5, 30, 60, or 120 second s after restoration of breathing, No profound apneas occurred with bas eline laryngeal stimulation, In piglets aged 32 to 36 and 17 to 21 day s, a second laryngeal stimulus resulted in a shortened apnea duration, The response varied in piglets aged IO to 12 days with profound apnea s observed in 2 of 6 subjects and 4 of 30 trials. Piglets aged 17 to 3 6 days are less susceptible to the laryngeal chemoreflex during the im mediate recovery period, In piglets aged 10 to 12 days, the laryngeal chemoreflex response may be more severe after a second stimulus.