Abnormal ventilatory responses to hypoxia in Type 2 diabetes

Aims  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 (V̇ 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 ∼85%) in eight subjects with Type 2 diabetes and seven age‐ and body mass index‐matched healthy subjects. Results  During normoxia, V̇ E was similar in control and diabetic subjects (6.4 ± 1.2, 6.4 ± 1.1 l/min, respectively). In response to hypoxia, V̇ 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 V̇ 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 V̇ E responses to acute isocapnic hypoxia, suggesting that this group of diabetic subjects possesses a chemoreflex ill‐equipped to respond homeostatically to hypoxic challenge.