Abnormal ventilatory responses to hypoxia in Type 2 diabetes

Aim The incidence of Type 2 diabetes is increasing, along with its associated micro- and macrovascular disease manifestations. Previous studies indicate that patients with Type 2 diabetes exhibit abnormal cardiopulmonary reflex responses to various stimuli, although the impact of hypoxia, a common physiological stimulus, on ventilatory responses has not previously been studied in humans with Type 2 diabetes.Methods Minute ventilation (V-E) breathing pattern responses (total breath time, T-TOT; expiratory time, T-E; inspiratory time, T-I; inspiratory duty cycle, T-I/T-TOT) were measured during 5 min each of normoxia and isocapnic hypoxia (arterial O-2 saturation similar to 85%) in eight subjects with Type 2 diabetes and seven age- and body mass index-matched healthy subjects.Results During normoxia, V-E was similar in control and diabetic subjects (6.4 +/- 1.2, 6.4 +/- 1.1 l/min, respectively). In response to hypoxia, V-E significantly increased in both groups (to 17.0 +/- 5.0 and 9.5 +/- 2.0 l/min, respectively, P < 0.05), but the magnitude of increase in V-E was significantly less in diabetic than in control subjects (P < 0.05). In addition, the breathing pattern response to hypoxia differed between groups in terms of T-I/T-TOT and T-TOT (P < 0.05), with control subjects significantly decreasing T-TOT and T-E (P < 0.05) while diabetic subjects tended to increase both.Conclusions Relative to matched control subjects, Type 2 diabetic subjects exhibit blunted V-E responses to acute isocapnic hypoxia, suggesting that this group of diabetic subjects possesses a chemoreflex ill-equipped to respond homeostatically to hypoxic challenge.