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 (V̇E) breathing pattern responses (total breath time, T TOT; expiratory time, TE; inspiratory time, TI; inspiratory duty cycle, TI/TTOT) were measured during 5 min each of normoxia and isocapnic hypoxia (arterial O2 saturation -85%) in eight subjects with Type 2 diabetes and seven age- and body mass index-matched healthy subjects. Results: During normoxia, V̇E was similar in control and diabetic subjects (6.4 ± 1.2, 6.4 ± 1.1 l/min, respectively). In response to hypoxia, V̇E 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 V̇E. 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 TI/TTOT and TTOT (P < 0.05), with control subjects significantly decreasing TTOT and TE (P < 0.05) while diabetic subjects tended to increase both. Conclusions: Relative to matched control subjects, Type 2 diabetic subjects exhibit blunted V̇E responses to acute isocapnic hypoxia, suggesting that this group of diabetic subjects possesses a chemoreflex ill-equipped to respond homeostatically to hypoxic challenge.
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- Breathing pattern
- Minute ventilation