Effect of Inhalation of CO₂ Gas during Artificial CO₂-Bathing for Cerebral Blood Flow in CVA Patients

Abstract

Purpose
To investigate the effect of CO₂-inhalation on the cerebral circulation of CVA patients during artificial CO₂-bathing, controlled examinations were made with ^99mTc-hexamethyl propyleneamine oxime SPECT (hereinafter abbreviated as HM-PAO-SPELT).
Subject and Methods
HM-PAO-SPECT was conducted on four CVA patients without CO₂-inhalation as a control. 0.5g of artificial CO₂-bath tablet (Kao Bub^®) was them added to 2l of hot tapwater at 40°C to provide an ordinary bathing concentration. The patients inhaled the CO₂ generated for 3min at a height of 20cm above the water level, which was immediately followed by HM-PAO-SPECT. Similar examinations were performed at a higher bathing concentration provided by adding 50g of artificial CO₂-bath tablet (Kao Bub^®) to 2l of water. To compare results with systemic circulation, blood pressure and blood gas were measured before and after the CO₂-inhalation.
Results
HM-PAO-SPECT showed a remarkable increase in blood flow in two of the four patients when 0.5g of artificial CO₂-bath tablet was used to provide an ordinary bathing concentration. At a concentration 100 times higher than ordinary concentration using 50g of artificial CO₂-bath tablet, obvious increase in blood flow was found in three of the patients. At both concentrations, the remaining patient showed a decrease on blood flow, with no change in blood pressure or blood gas.
Discussion
CO₂ is considered as one of the most potent factors involved in cerebral blood flow. In these examinations, the effect of CO₂-inhalation from artificial CO₂-bath tablet in increasing blood flow was confirmed by means of HM-PAO-SPECT. Its usefulness was thus proven. The subject who showed a decrease in blood flow may have been in a period of steal phenomenon, or luxury perfusion, when he underwent the examination. Future studies must be performed on the relationship between the increase in blood flow and the improvement of symptom, timing of artificial CO₂ bathing, and between the effect of artificial bathing and the CO₂ concentration.