Effects of a single bout of interval hypoxia on cardiorespiratory control in patients with type 1 diabetes - Duennwald et al. (2013)
Key Points
One session of intermittent hypoxia (IH) improved hypercapnic and hypoxic ventilatory responses in type 1 diabetics
One session of IH increased aerobic efficiency in type 1 diabetic participants
Longer-term IH training might be therapeutic in type 1 diabetes
The Breathing Diabetic Summary
Type 1 diabetics generally suffer from low-grade chronic hypoxia, which, as we have learned, might be the root cause of many diabetic complications. Thus, it might seem counterproductive for diabetics to practice intermittent hypoxia (IH) training. However, when used correctly, IH training helps adapt the body to hypoxia. Therefore, the authors of this paper hypothesized that IH training in diabetics would help their bodies adapt to their condition of low-grade hypoxia.
Fifteen patients with type 1 diabetes were recruited to participate in the experiment. The hypoxia session consisted of 6 min of hypoxia followed by 6 min of normoxia, repeated 5 times. Hypoxia was achieved by breathing in air with 13% oxygen (well within the therapeutic range). There was also a placebo day where the participants underwent the same protocol but breathed normal air. Measurements of many different cardio-respiratory parameters were obtained before (baseline), immediately after, and 3 and 6 h after the IH session.
At baseline, they found that the diabetics’ hypercapnic ventilatory response (HCVR) was reduced (note that many studies have found conflicting results with respect to HCVR and diabetics). After the IH session, HCVR increased significantly and stayed elevated for 6 h. Further, the hypoxic ventilatory response also increased after the IH training.
They did not observe many changes in cardiovascular or hematological parameters, which is interesting because the measurements were taken immediately after the IH session and therefore we would expect some abnormal readings due to the stress of IH. There was, however, a significant decrease in blood lactate concentrations on the IH training day that was not observed on the placebo day. This suggests that the IH training improved the efficiency of the body’s aerobic pathway.
We recently learned that 3 weeks of intermittent hypoxia (IH) training induced favorable changes to cardio-autonomic-respiratory parameters in chronic obstructive pulmonary disease (COPD). In this current study, however, the authors wanted to see if a single session of IH training could elicit positive adaptations because IH training had not been studied in type 1 diabetics before. Therefore, further studies will be needed to see if the long-term adaptations of type 1 diabetics to IH training is similar to what was observed in COPD.
Overall, this study found that one session of IH induced favorable adaptations with respect to ventilatory responses to hypercapnia and hypoxia and improved the body’s aerobic efficiency. The results were not groundbreaking, but they do suggest further studies are needed. And, because there were few negative effects from the session, IH potentially could be therapeutic in diabetes.
Abstract from Paper
Hypoxemia is common in diabetes, and reflex responses to hypoxia are blunted. These abnormalities could lead to cardiovascular/renal complications. Interval hypoxia (IH) (5-6 short periods of hypoxia each day over 1-3 weeks) was successfully used to improve the adaptation to hypoxia in patients with chronic obstructive pulmonary disease. We tested whether IH over 1 day could initiate a long-lasting response potentially leading to better adaptation to hypoxia. In 15 patients with type 1 diabetes, we measured hypoxic and hypercapnic ventilatory responses (HCVRs), ventilatory recruitment threshold (VRT-CO2), baroreflex sensitivity (BRS), blood pressure, and blood lactate before and after 0, 3, and 6 h of a 1-h single bout of IH. All measurements were repeated on a placebo day (single-blind protocol, randomized sequence). After IH (immediately and after 3 h), hypoxic and HCVR increased, whereas the VRT-CO2 dropped. No such changes were observed on the placebo day. Systolic and diastolic blood pressure increased, whereas blood lactate decreased after IH. Despite exposure to hypoxia, BRS remained unchanged. Repeated exposures to hypoxia over 1 day induced an initial adaptation to hypoxia, with improvement in respiratory reflexes. Prolonging the exposure to IH (>2 weeks) in type 1 diabetic patients will be a matter for further studies.
Journal Reference:
Duennwald T, Bernardi L, Gordin D, et al. Effects of a Single Bout of Interval Hypoxia on Cardiorespiratory Control in Patients With Type 1 Diabetes. Diabetes. 2013;62:4220-4227.