Abnormal ventilatory responses to hypoxia in Type 2 diabetes
Weisbrod, C. J., Eastwood, P. R., O'Driscoll, G. & Green, D. J. (2005). Abnormal ventilatory responses to hypoxia in Type 2 diabetes. Diabetic Medicine, 22(5), 563–568. doi: 10.1111/j.1464-5491.2005.01458.x
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 (VE) breathing pattern responses (total breath time, TTOT; 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, VE was similar in control and diabetic subjects (6.4 ± 1.2, 6.4 ± 1.1 l/min, respectively). In response to hypoxia, VE 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 VE 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 VE responses to acute isocapnic hypoxia, suggesting that this group of diabetic subjects possesses a chemoreflex ill-equipped to respond homeostatically to hypoxic challenge.