Volume 4 Supplement 1
Continuous monitoring of gastric carbon dioxide with optical fibers: European project COMOCADOF, in vitro evaluation
© Current Science Ltd 2000
Published: 21 March 2000
Gastric mucosal PCO2 is an important parameter to evaluate the splanchnic perfusion and to estimate the prognosis of critically ill patients. Saline and gas tonometry are the existing measurement methods, with air tonometry being the golden standard. The main disadvantage of this method is the relatively long equilibrium time, which only allows intermittent registrations and therefore cannot reflect rapid changes of PrCO2.The target of the COMOCADOF project was the development of an optical fiber sensor capable of a continuous monitoring of PCO2 inside the stomach, with high accuracy and long-term stability, able to track rapid PrCO2 changes.
Evaluation of the feasibility of a measurement device using an optical fiber sensor for continuous measurement of gastric PCO2.
The COMOCADOF system consists of a fiberoptical catheter and the measurement unit. A CO2-sensitive polymer layer is inserted into a probe head, which is fixed at the end of the optical fiber. The in vitro tests were performed in a glass test-tube containing 20 ml of sample solution, which was maintained at a temperature of 37°C. The sample solution (either physiological saline or a physiologically adjusted hydrochloric acid of pH 1.0) was flushed with 6 gas mixtures containing 0.0 to 15.0% CO2 for defined time intervals and at a gas flow rate of 50 ml/min. The sampling rate was typically 0.8 s. The tests were performed over a period of up to 48 h. In addition, the influence of gastric juice, colored or turbid samples (such as e.g. enteral nutrition) on the stability of the optochemical sensor was tested.
The table shows the original minimum requirements (target at the beginning of the project) and the achievements obtained up to now with the optical sensor for the detection of gastric carbon dioxide.
No significant influence of gastric juice, physiologically adjusted hydrochloric acid of pH 1.0, colored or turbid samples (such as e.g. enteral nutrition) was seen.
Measurement range (mmHg)
Resolution at 0 mmHg (mmHg)
Resolution at 120 mmHg (mmHg)
Response time (T90) (min)
Accuracy in range 40–105 mmHg (mmHg)
Accuracy in range 0–40 mmHg (mmHg)
Measurement period within accuracy (h)