Abstract
Blood gasmetry under hyperbaric oxygenated condition was studied clinically in relation to the difference of masks, calibration gases and the effect of heparin in sampling syringe. Subjects were 197 patients of cerebrovascular disease. IL #813 model（Instrumentation Laboratory Inc.） was employed as blood gas analyzer. During inhalation of pure oxygen, two kinds of low calibration gases were used as follows; gas A（O2 50%, CO2 2.5%, N2 balance）and gas B（O2 95%, CO2 2.5%, N2 balance）.
When gas B was used, PaO2 at 2 ATA was 725±125mmHg in patients using oxygen mask （lnspiron）, and 1088±147mmHg with anesthetic mask（Acoma）. But, when gas A was used, PaO2 showed apparently lower value than that of gas B （p<0.001）.
To study the influence of heparin upon PaO2, two kinds of heparin were used in sampling syringe; powdered and liquid heparin. Under 1 ATA O2 and 1 ATA air condition, the property of heparin had no influence upon PaO2. However, under 2 ATA O2 condition, when liquid heparin was used, PaO2 was significantly lower than those utilized powdered heparin（p<0.01）.
When extremely high PaO2 can be expected, calibration gas should be selected which has approximate properties to the sampled blood gas, and powdered heparin should be also prefered.
