A comparison of descending aortic and “arterialized” capillary blood in the sick newborn

Comparison was made of 53 “arterialized” capillary (heel prick) samples with descending aortic blood in 26 babies, of whom 24 were less than one week old and 18 had R.D.S. “Arterialized” capillary blood is an accurate and practical means of assessing aortic blood pH and Pco 2 over a range of 6.69 to 7.54 and 18 to 94 mm. Hg respectively. “Arterialized” capillary sampling is a reliable means of assessing descending aortic Po 2 when the “arterialized” capillary value is less than 60 mm. Hg. When higher than 60 mm. Hg the “arterialized” capillary oxygen tension may be considerably less than that of the blood in the descending aorta, hence the “arterialized” capillary blood oxygen tension method is unreliable in estimating systemic oxygenation when the descending aortic oxygen tension is more than 60 mm. Hg.