Comparison of two techniques for measuring carbon dioxide and oxygen levels in patients requiring arterial blood gas measurement.

The Arterial Blood Gas (ABG) is the gold standard measurement to estimate oxygen saturations and carbon dioxide levels in the bloodstream. Transcutaneous monitoring of carbon dioxide and oxygen saturations has the advantage of being easily measured using a small clip, usually placed on the earlobe. Unlike an ABG measurement, it allows continuous monitoring of carbon dioxide and oxygen levels, is painless, and does not have the risk of causing distal ischemia. The SenTec transcutaneous monitors have been used in several of our studies investigating the effects of oxygen therapy on blood carbon dioxide and oxygen levels. While the SenTec devices have been validated previously in one study, the devices need to be validated in the setting and under the standard operating procedures (SOPs) that are used in Medical Research Institute of New Zealand (MRINZ) trials. Our aim is to recruit patients (inpatients or outpatients) who are due to receive an ABG as part of their clinical management at Wellington Regional Hospital. When the ABG sample is taken the study investigator will record the carbon dioxide and oxygen saturation levels displayed by the transcutaneous monitor(s). These will then be compared to the ABG results.