Detection of ischemia by a biosensor measuring tissue carbon dioxide tension

Abstract

Objective

We investigated a miniaturized biomedical sensor that can be inserted into any tissue or organ to measure partial gas pressure of carbon dioxide (pCO₂) and temperature continuously in real time. Numerous animal studies have shown that pCO₂ is a sensitive and specific marker of ischemia. The present study was designed to examine the feasibility and safety of the device in patients scheduled for limb orthopedic (arm/leg) surgery with tourniquet.

Methods

We performed an observational, prospective, cohort study at a single center in Norway. The primary and secondary endpoints were to evaluate the ability of the biosensor to measure pCO₂ and corresponding temperature levels in ischemic and nonischemic limb musculature and subcutaneous tissue. Additional secondary objectives were to assess the safety/efficacy of using the device.

Results

Forty-five patients received the sensor in this study from May 2021 to June 2022. The mean difference between the pCO₂ levels in ischemia and nonischemia limbs was 29.4 mmHg (95% confidence interval [CI], 25.8-33.0; P < .001). When examining intramuscular tissue exclusively, the mean total difference between the pCO₂ levels in ischemic and nonischemic limb was 32.7 mmHg; 95% CI [27.5; 37.9], P < .001. The mean difference between the temperature levels in intramuscular and subcutaneous tissue in ischemic and nonischemic limb was 2.5 ^oC (95% CI, 2.0-2.9; P < .001) and 2.6 ^oC (95% CI, 2.1-3.2; P < .001), respectively. Four patients experienced minor bleeding (less than 5 mL) during insertion of the sensors. No other bleeding was reported during the study period. None of the subjects experienced any kind of clinical infections/inflammations or pain (numeric rating scale score, 0) at the insertion sites during the entire study period. No serious adverse events related to the study procedure or device were noted.

Conclusions

The device provides a safe and dependable way to continuously and instantly track pCO₂ levels in muscular and subcutaneous tissues, thereby offering a means to detect and monitor ischemia.