Critical care medicine
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Critical care medicine · Oct 1981
Transcutaneous oxygen monitoring of critically ill adults, with and without low flow shock.
One hundred and six critically ill adult patients were monitored continuously with a transcutaneous oxygen sensor (PtcO2); they also were intermittently monitored with conventional invasive hemodynamic and oxygen transport variables. A total of 1073 data sets were taken on 41 patients in the ICU and 65 patients in the operating room. The patients were divided into three groups by cardiac index (CI): relatively normal flow, CI greater than 2.2 L/min x M2; moderate low flow shock, 2.2 greater than CI greater than 1.5 L/min x M2; and severe low flow shock, CI less than 1.5 L/min x M2 x PtcO2 and arterial oxygen tension (PaO2) were compared in two ways: first by linear regression and second by a more simple clinical guide by indexing each transcutaneous value by its respective arterial value (PtcO2 index = PtcO2/PaO2). ⋯ The patients not in shock responded to changes in inspired oxygen concentration (FIO2) with changes in PaO2 and PtcO2 values; the 95% response time was approximately 2 min. The authors conclude that the normal value for PtcO2 for adult surgical patients who are hemodynamically stable is 79 +/- 12% of the PaO2 and that PtcO2 values were reliable, continuous, noninvasive trend monitors of PaO2 in these patients. During circulatory problems when PtcO2 values were compared to PaO2 values (PtcO2 index), the changes reflected trends in the severity of low flow shock.
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The value of continuous transcutaneous oxygen (PtcO2) monitoring in the presence of halothane and nitrous oxide (N2O) was studied in 10 infants. All infants were continuously monitored during the study with a Clark-type skin electrode with Mylar membrane. The polarization voltage of the membrane was changed to 600 mV to make it insensitive to N2O and halothane. ⋯ During the hyperoxic state, poor correlation existed between PaO2 and PtcO2 (r = 0.51). Although PtcO2 did not correlate with PaO2 during hyperoxia, it consistently overestimated PaO2 and thereby, provided a predictive ability by over-diagnosing hyperoxia. When combined with continuous monitoring of inspired oxygen tension to maintain normoxia, continuous monitoring of PtcO2 will reduce the frequency of PaO2 analysis and improve patient care during anesthesia.
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Critical care medicine · Oct 1981
Case ReportsTranscutaneous measurements of carbon dioxide partial pressure in sick neonates.
The authors measured the partial pressure of carbon dioxide transcutaneously (PtcCO2) in 15 sick newborns and compared the PtcCO2 to simultaneously measured partial pressure of arterial carbon dioxide (PaCO2). The PtcCO2 values reflected changes in the PaCO2 values. A linear regression on 106 paired PtcCO2 and PaCO2 values produced a correlation coefficient of 4 = 0.91 with a slope of 1.89 and a y-intercept of --9.4. The authors found the measurement of PtcCO2 to be a clinically useful method of continuously following the trend of PaCO2.