Factors influencing transcutaneous oxygen and carbon dioxide measurements in adult intensive care patients

Abstract

Transcutaneous PO2 (PtcO2) is suggested to reflect tissue oxygenation in intensive care patients, whereas transcutaneous PCO2 (PtcCO2) is advocated as a noninvasive method for assessing PaCO2. In 24 critically ill adult patients (mean Apache II score 14.2, SD 4.7) we investigated the impact of variables that are commonly thought to determine PtcO2 and PtcCO2 measurements. A linear correlation was found between PtcO2 and PaO2 (r = 0.6; p less than or equal to 0.0001) and between PtcO2 and mean arterial blood pressure (MAP; r = 0.42; p less than or equal to 0.003). Cardiac index (CI) correlated with tc-index (PtcO2/PaO2; r = 0.31; p less than or equal to 0.03). There was no relationship between PtcO2 and hemoglobin concentration (Hb) and the position of the oxygen dissociation curve (ODC). Stepwise multiple regression analysis demonstrated a significant influence of PaO2 and MAP on PtcO2. The contribution of CI, Hb and the ODC was not significant. Only 40% of the variability of a single PtcO2 measurement could be explained by PaO2 and MAP. A significant linear correlation was demonstrated between PtcCO2 and PaCO2 (r = 0.76; p less than or equal to 0.0001) but not between PtcCO2 and CI, MAP and arterial base excess (BEa). Stepwise multiple regression analysis revealed an influence of PaCO2 and of CI on PtcCO2; 66% of the variability of a single PtcCO2-value could be explained by PaCO2 and CI. Our data demonstrate that transcutaneous derived gas tensions result from complex interaction between hemodynamic, respiratory and local factors, which can hardly be defined in ICU-patients.

Variability of Transcutaneous Oxygen and Carbon Dioxide Pressure Measurements Associated with Sensor Location

“…Despite differences in the values of PtcO 2 and PaO 2 , a relationship between these two parameters has been documented (Weaver 2007;Kesten et al 1991). Some authors have shown that the strongest correlation between PtcO 2 and PaO 2 was found for PtcO 2 values measured on the chest (Nishiyama et al 2006;Hasibeder et al 1991). The present results failed to confirm this observation.…”

“…In a report by Weaver (2007) the difference between PtcO 2 and PaO 2 was <10 %, but that study involved healthy subjects in hyperbaric conditions. In reports on transcutaneous gas measurement in severely ill patients, the PtcO 2 /PaO 2 difference was even more pronounced (Hasibeder et al 1991). However, the comparative analysis of results from healthy subjects and patients with various respiratory and circulatory disorders may be misleading and requires caution, as the measurements in the latter can be influenced by hypoperfusion and alterations in tissue metabolism.…”

“…Even though the transcutaneous measurement of PO 2 and PCO 2 has important advantages, it must be emphasized that this method differs considerably from the measurement of partial gas pressures in the arterial blood (Hasibeder et al 1991). Transcutaneous PO 2 is always lower than PaO 2 .…”

The peripheral perfusion index and transcutaneous oxygen challenge test are predictive of mortality in septic patients after resuscitation

“…attempted the translation of PtcO 2 values to cardiac hemodynamics, when they explored the dependence of PtcO 2 on PaO 2 using a PtcO 2 index (PtcO 2 /PaO 2 ) to assess the severity of low flow shock [6]. A PtcO 2 index below 0.7 has been associated with hemodynamic failure in adult patients [25,26]. The PtcO 2 index has been used to estimate the adequacy of cardiac output and peripheral blood flow.…”

Postoperative assessment of free skin flap viability by transcutaneous pO2 measurement using dynamic phosphorescence imaging

“…Due to pre-existing diseases like diabetic disease, venous or arterial hypertension, pulmonal diseases or different anatomic conditions [23][24][25][26] the mean tissue oxygen tension of each patient differs a lot (e.g. Pat.…”