IMPAIRED FOREARM BLOOD FLOW RESPONSE TO BREATH HOLDING IN DIABETIC PATIENTS WITH MANIFESTATIONS OF NEUROPATHY

Abstract

Breath holding affects vasomotion through an increase in PaC02 and a decrease in PaOz and intrathoracic pressure in normal subjects. This study attempts to see if the vasomotivese response would be the same in persons with diabetic autonomic neuropathy. Seven healthy subjects (one female and six males, fasting blood sugar, 4.44-5.83 mmol V and aged 45-55 years) and seven diabetics (one female and six males, fasting blood sugar, 5.00-7.78 mmol L-1 and aged 45-57 years) were studied while breathing normally for about five minutes
and during a breath holding period of 40-65 seconds. Four to five readings were recorded in each testing condition with a resting interval of about 90 seconds. The overall mean forearm blood flow decreased significantly (%A=-4L16, P<O.Ol) in the healthy subjects holding their breath for 40-65 seconds (average=52.1 sec). This reduction in forearm blood flow, which was not proportional to the duration of breath holding, signifies the reflex effect of increased PaC02 and decreased PaOz. None of the diabetic patients showed forearm blood flow reduction in response to an average breath holding time of 51.4 seconds (%A = 3.56, p<0.50). This lack ofreflex vasomotion in response to increased PaC02 and decreased Pa02 indicates that the sympathetic supply to
the vascular bed of the forearm is not intact. The apparent changes in the blood gases occurring during breath holding did not produce a direct vasodilatory effect either. This is probably attributable to vessel wall rigidity and lack or ineffectivity of endothelium-derived factors developing with metabolic and, structural derangements. The resting overall mean forearm blood flow in diabetics (5.33 ±O. 78ml/looml/min) compared with that of the c¢ntrols (3.96±O.39 ml/looml~ fmin) is significantly greater (%A=+36.62, p<O.Ol). This apparently suggests
that diabetic neuropathy leads to elevated resting blood flow. The significance of the pr~sent finding is that breath holding can be used as. a quick method for 42 Yoseph A. Mengesha assessing sympathetic denervation by measuring forearm blood flow and related cardiovascular variables.