Ventilatory response to exercise in diabetic subjects with autonomic neuropathy.
We have used diabetic autonomic neuropathy as a model of chronic pulmonary denervation to study the ventilatory response to incremental exercise in 20 diabetic subjects, 10 with (Dan+) and 10 without (Dan-) autonomic dysfunction, and in 10 normal control subjects. Although both Dan+ and Dan- subjects achieved lower O2 consumption and CO2 production (VCO2) than control subjects at peak of exercise, they attained similar values of either minute ventilation (VE) or adjusted ventilation (VE/maximal voluntary ventilation). The increment of respiratory rate with increasing adjusted ventilation was much higher in Dan+ than in Dan- and control subjects (P < 0.05). The slope of the linear VE/VCO2 relationship was 0.032 +/- 0.002, 0.027 +/- 0.001 (P < 0.05), and 0.025 +/- 0.001 (P < 0.001) ml/min in Dan+, Dan-, and control subjects, respectively. Both neuromuscular and ventilatory outputs in relation to increasing VCO2 were progressively higher in Dan+ than in Dan- and control subjects. At peak of exercise, end-tidal PCO2 was much lower in Dan+ (35.9 +/- 1.6 Torr) than in Dan- (42.1 +/- 1.7 Torr; P < 0.02) and control (42.1 +/- 0.9 Torr; P < 0.005) subjects. We conclude that pulmonary autonomic denervation affects ventilatory response to stressful exercise by excessively increasing respiratory rate and alveolar ventilation. Reduced neural inhibitory modulation from sympathetic pulmonary afferents and/or increased chemosensitivity may be responsible for the higher inspiratory output.
Tantucci
C
C
Clinica di Semeiotica Metodologia Medica, University of Ancona, Ospedale Regionale Torrette, Italy.
Bottini
P
P
Dottorini
M L
ML
Puxeddu
E
E
Casucci
G
G
Scionti
L
L
Sorbini
C A
CA
D000328:Adult; D015308:Anaerobic Threshold / Q000502:physiology; D001342:Autonomic Nervous System Diseases / Q000503:physiopathology*; D001786:Blood Glucose / Q000378:metabolism; D002245:Carbon Dioxide / Q000378:metabolism; D003929:Diabetic Neuropathies / Q000503:physiopathology*; D004562:Electrocardiography; D015444:Exercise / Q000502:physiology*; D006801:Humans; D019344:Lactic Acid / Q000097:blood; D008297:Male; D010101:Oxygen Consumption / Q000502:physiology; D011659:Pulmonary Gas Exchange / Q000502:physiology; D012129:Respiratory Function Tests; D015656:Respiratory Mechanics / Q000502:physiology*
D001786:Blood Glucose; D002245:Carbon Dioxide; D019344:Lactic Acid