VENTILATORY-CONTROL ABNORMALITIES IN FAMILIAL SLEEP-APNEA

The role of ventilatory-control abnormalities in predisposing to famil ial sleep-disordered breathing (SDB) was assessed in 31 subjects 28 +/ - 10 yr of age (mean +/- SD). Subjects with (n = 10) and without SDB ( n = 12) were recruited from 13 families having two or more members wit h SDB. Nine age- and gender-matched controls were recruited from famil ies having no member with SDB. Respiratory responses to eucapnic hypox ia, and ventilatory and occlusion pressure responses to hyperoxic hype rcapnia with and without added resistive loads (6.5 cm H2O/L/s), were assessed through rebreathing. Age, FEV1, and FVC did not differ among the groups. Hypoxic responses (Delta VE/Delta Sa(O2)) were significant ly lower among the first-degree relatives of SDB families than among c ontrols (-0.76 +/- 0.47 L/min/% Sa(O2), and -1.32 +/- 0.92 L/min/% Sa( O2), respectively, p < 0.05). Respiratory responses to hypercapnia dur ing unloaded conditions were similar among the groups. With resistive loading, inspiratory impedance, as measured through the relationship o f mouth occlusion pressure (P-100) to inspiratory flow (VT/TI), increa sed with increasing hypercapnia to a greater extent in members of SDB families than in controls (0.169 +/- 0.054 cm H2O/L/min versus 0.122 /- 0.051, respectively, p < 0.05). These data suggest that familiar SD B may be based partly on a familial abnormality in ventilatory control associated with blunting of the hypoxic ventilatory response. The gre ater increase in impedance during inspiratory loading in members of af fected families also suggests a propensity for dynamic airway narrowin g.