Effect of Hyperoxia and Hypoxia on Subcutaneous Tissue Gases and pH

Abstract

The effect of different fractions of inspired oxygen on subcutaneous oxygen tension, carbon dioxide tension and pH in relation to arterial and mixed venous blood gases and pH and hemodynamic variables was evaluated in 13 domestic pigs. Subcutaneous, arterial and mixed venous oxygen tensions were closely correlated (r = 0.94). A minor significant increase in subcutaneous carbon dioxide tension was noted during hyperoxia (p < 0.05). A major increase (33%) was noted during the last step of hypoxia, when arterial and mixed venous carbon dioxide tensions increased only 12 and 17%, respectively. A minor decrease in subcutaneous pH was noted during hyperoxia (p < 0.05) and a major decrease during hypoxia (p < 0.05). Measurements of subcutaneous tissue gases and pH are indicators of oxygen utilization during hyper- and hypoxia.

Influence of Positive End-Expiratory Pressure Ventilation on Peripheral Tissue Perfusion Evaluated by Measurements of Tissue Gases and pH

“…As a consequence of increased regional PCO 2 , the regional pH will fall reflecting a relative imbalance between tissue oxygen supply and metabolism [27,29]. The pHsc values measured in this study were higher than the arterial pH, but similar to measurements with a Roche tissue pH electrode and previous measurements with the Paratrend 7 sensor [15,30,31]. It cannot be excluded that these pH values represent a true value of subcutaneous tissue pH, but the absolute values may be less important than changes over time.…”

Evaluation of Subcutaneous Tissue Gases and pH during Induction of Acidosis and Alkalosis

“…In a study on the effect of hyperoxia and hypoxia P sc O 2 was 58 mm Hg when P a O 2 was 92 mm Hg and P sc O 2 14 mm Hg when P a O 2 was 29 mm Hg [19]. The value in the present study is about 5 mm Hg higher than in the previous study.…”

“…In previous studies, subcutaneous tissue pH values have been evaluated with the Roche electrode and the Paratrend 7 sensor. In those studies as well as in the present the obtained pH values of the subcutaneous tissue were higher compared to those in arterial blood [19,23].…”

“…However, some changes in the hemodynamic parameters were noted already during mild hypoxia, but the metabolic changes at the tissue level, measured as changes in tissue carbon dioxide tension and pH, were only noted at severe hypoxia (table 1). [19]. At this stage when the P a O 2 decreased from 53 to 26 mm Hg the oxygen uptake was still constant due to an increased oxygen extraction.…”

“…More recently it has been evaluated in the subcutaneous tissue of pigs subjected to hyperoxia and hypoxia [19]. The sensor was originally developed for continuous measurements of arterial blood gases and pH [20,21].…”