Transcutaneous Sensor Research Articles

Continuous monitoring of oxygen tension with a transcutaneous sensor during hypotensive anesthesia.

Transcutaneous oxygen tension (TCPO2) is a useful noninvasive technique for monitoring arterial oxygen tension under stable circulatory conditions. This study was undertaken to determine if TCPO2 is also reliable during sodium nitroprusside-induced hypotension under general anesthesia. Arterial blood gases and TCPO2 were measured prior to inducing hypotension (baseline), at 20-min intervals during hypotension, and when systemic arterial pressure had returned to within 10% of the control (pre-hypotension) value. With induced hypotension, PaO2 and TCPO2 decreased significantly (P less than 0.05), and were well correlated by linear regression (r greater than 0.85); however, regressions were strongly dependent on the individual patient. The mean regression line for all patients as a group was given by TCPO2 = 0.69 PaO2 + 20.7 mmHg (r = 0.93, P less than 0.01); significantly different regressions were obtained for each patient (P less than 0.0001). Comparing changes in TCPO2 versus those in PaO2 (relative change from baseline values) did not substantially reduce the variability among patients. It is concluded that TCPO2 reliably reflects changes in arterial oxygen tension during controlled hypotension under general anesthesia, but that a separate calibration of TCPO2 vs. PaO2, obtained prior to inducing hypotension, may be required for each individual patient.

A novel approach for an ECG electrode integrated into a transcutaneous sensor.

The integration of an ECG-electrode into a common transcutaneous sensor allows simple handling and leads to a reduction of the physiological stress of pre-term infants. Furthermore it may allow future replacement of an invasive method to measure the ECG under labour by a non-invasive one.

Transcutaneous Carbon Dioxide Tension in Newborn Infants: Reliability and Safety of Continuous 24-Hour Measurement at 42°C

In 58 newborn infants a new iridium oxide sensor was evaluated for transcutaneous carbon dioxide (tcPco2) monitoring at 42°C with a prolonged fixation time of 24 hours. The correlation of tcPco2 (y; mm Hg) v Paco2 (x; mm Hg) for 586 paired values was: y = 4.6 + 1.45x; r = .89; syx = 6.1 mm Hg. The correlation was not influenced by the duration of fixation. The transcutaneous sensor detected hypocapnia (Paco2 < 35 mm Hg) in 74% and hypercapnia (Pco2 > 45 mm Hg) in 74% of all cases. After 24 hours, calibration shifts were less than 4 mm Hg in 90% of the measuring periods. In 86% of the infants, no skin changes were observed; in 12% of infants, there were transitional skin erythemas and in 2% a blister which disappeared without scarring. In newborn infants with normal BPs, continuous tcPco2 monitoring at 42°C can be extended for as many as 24 hours without loss of reliability or increased risk for skin burns.

RELIABILITY AND SAFETY OF TRANSCUTANEOUS CARBON DIOXIDE TENSION (tcPCO2): MONITORING AT 42°C SENSOR TEMPERATURE DURING 24 HRS WITHOUT REPLACEMENT

TcPCO2 monitoring is widely used in the neonatal ICU. Reliability and safety of this indirect method to measure arterial PCO2(PaCO2) have been questioned, particularly when the sensor remains in place for more than 4 hours. Goal of this study was to assess correlation between tcPCO2 and PaCO2 and skin alterations during 24 hours monitoring without replacement.Patients: 51 critically ill newborns who required an arterial catheter for the clinical management. Weights 680-4170 g, Gestational ages 27-41 weeks.Method: An iridium oxide electrode (Transcapnode Hellige) heated at 42°C was chosen because of better stability than conventional glass electrodes. The sensor was calibrated with 5 and 10% CO2 and attached to the trunc or to the thigh. TcPCO2 was recorded continuously. Arterial blood samples were drawn systematically at 30’ and at 24 hours and on clinical indications. PaCO2 was measured with an IL 313 or an AVL 945 gas analyser.Results: After removal of the sensor no visible change of the skin was noted in 44 infants and a discrete erythema in 7. A blister developed in one patient 24 hours later which disappeared without scar. The correlation of tcPCO2(y;Torr) vs. PaCO2(x; Torr) was calculated for 504 paired values: y = 5.4 + 1.4×; r=.89; Sy·x=6.0 Torr. There was no systematic difference between the paired values at 30’ and those at 24 hours. The transcutaneous sensor detected 61% of hypocapnia (PaCO2<30 Torr, n=38) and 88% of hypercapnia PaCO2>50 Torr, n=73).Conclusion: The correlation between tcPCO2(42°C) and PaCO2 is acceptabel for clinical use and not influenced by the duration of fixation of the sensor up to 24 hours.

Estimation of arterial oxygen and carbon dioxide tensions by a single transcutaneous sensor.

A transcutaneous electrochemical sensor designed to estimate arterial oxygen (Pao2) and carbon dioxide (Paco2) tensions simultaneously and continuously was evaluated in newborn infants with respiratory illnesses. After calibration with two dry gas mixtures the sensor gave estimates of Pao2 and Paco2 that were comparable with those obtained by two separate electrodes that are already established in clinical use.

Continuous conjunctival and transcutaneous oxygen tension monitoring during resuscitation in a patient

Conjunctival ( PcjO 2) and transcutaneous ( PtcO 2) oxygen tensions were serially measured in a patient with multiple stab wounds. Even though blood pressure was normal, severe hypovolemia due to hemorrhage was detected in the emergency department by abnormally low P cjO 2 P aO 2 and P tcO 2 P aO 2 ratios. The adequacy of resuscitation was established by return of these ratios to normal values. The conjunctival sensor stabilized more rapidly than the transcutaneous sensor and is of greater utility in the emergency setting. It was found that conjunctival and transcutaneous oxygen sensors can play an important role in monitoring clinical state and resuscitation of trauma patients.