The ring must create enough of a seal to prevent leaks or formation of air bubbles, as ambient air reaching the sensor affects measured values. The sensor is then placed into the ring and usually snaps into place.
This improves the accuracy of the sensor and makes the diffusion of gases more efficient. However, changing sites as often as every 2 hours may be necessary in small premature neonates to avoid thermal injury.Īfter the fixation device is in place, 1–2 drops of either contact gel or normal saline should be placed inside the ring. This option may be especially important for neonatal population compliance with the minimal handling approach promoted in their care.
29 When monitoring P tcCO 2 only, use of lower skin probe temperatures increases the systematic overriding of TC measurement and may allow for longer periods of contact time between the skin and the sensor, for up to 8–12 hours. 29 Correlation with arterial blood gases is recommended to ensure accuracy of the values obtained by TC monitor. 1, 28 Most TC monitors allow the reduction of the probe temperature to minimize the risk of thermal injury. 27 By contrast, monitoring of the P tcCO 2 is reliable with skin temperature even as low as 37☌. 22– 26 In order to achieve accurate P tcO 2 the skin probe temperature must be 44☌, which may lead to injury or burning of the skin, particularly in patients with thin or damaged skin. Alternative sites may be the lateral side of the abdomen, chest, buttock, inside of the upper thigh, forearm, the zygomatic bone, the ear lobe, cheeks, or the forehead. The preferred location to obtain TC measurements in neonates and small pediatric patients is the upper chest.
Once the site is cleaned, then a sensor fixation ring should be placed in a highly vascularized area. After the sensor is calibrated, the skin must be cleaned of all oils, soaps, and dead skin. 21Įach manufacturer's calibration protocol for the TC monitor sensor should be followed. 1, 15– 20 A Clark electrode, which is composed of a platinum cathode and silver anode, measures the P O 2. Additionally, a temperature correction is used to address the epithelial CO 2 produced by heating the skin. 14 The sensor, usually a Severinghaus electrode, will calculate the P CO 2 electrochemically, usually by a change in pH of an electrolyte solution. The externally applied heat alters the solubility of CO 2 in the blood and increases the metabolic rate of the skin by approximately 4–5% for every degree Celsius, resulting in local production of CO 2. The TC monitor device induces hyperperfusion of the capillaries by increasing the local temperature of the skin at the sensor site. The measurements obtained include P tcO 2 and P tcCO 2.
The update of this clinical practice guideline is the result of reviewing a total of 124 articles: 3 randomized controlled trials, 103 prospective trials, 1 retrospective study, 3 case studies, 11 review articles, 2 surveys and 1 consensus paper on transcutaneous monitoring (TCM) for P tcO 2 and P tcCO 2. An electronic literature search for articles published between January 1990 and September 2011 was conducted by using the PubMed, CINAHL, SCOPUS, and Cochrane Library databases.