Abnormal ventilatory responses to hypoxia in Type 2 diabetes.
OBJECTIVE
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 O2 saturation approximately 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.
Weisbrod
C J
CJ
School of Human Movement & Exercise Science, The University of Western Australia, Crawley, WA.
Eastwood
P R
PR
O'Driscoll
G
G
Green
D J
DJ
D003924:Diabetes Mellitus, Type 2 / Q000150:complications / Q000503:physiopathology*; D005260:Female; D005541:Forced Expiratory Volume / Q000502:physiology; D006801:Humans; D000860:Hypoxia / Q000209:etiology / Q000503:physiopathology*; D008176:Lung Volume Measurements; D008297:Male; D008875:Middle Aged; D012120:Respiration Disorders / Q000209:etiology / Q000503:physiopathology*