Both the OxyArm and Capnoxygen mask provide clinically useful capnographic monitoring capability in volunteers

To compare the capnography monitoring performance of the new OxyArm (OA) with the Capnoxygen mask (CM), a conventional oxygen mask with a carbon dioxide sampling port.

Eleven healthy volunteer adult subjects underwent capnographic monitoring (in a non-randomized, un-blinded crossover study) at baseline and while receiving oxygen at seven different flow rates (0.5, 1.0, 2.0, 4.0, 6.0, 8.0, and 10 L x min(-1)), applied first with the CM and then with the OA.

Both the OA and CM produced acceptable capnographs with consistent waveforms. The measured end-tidal (ET) CO(2) was equivalent for the two devices at all seven oxygen flow rates. On average, the ETCO(2) measured with the OA was about 2 mmHg greater than that of the CM. Regression analysis showed an inverse relationship between oxygen therapy flow rate and measured ETCO(2) whereby the measured value of CO(2) decreased as the oxygen flow rate was increased (P < 0.001). Both the CM and OA produced consistent measurements of ETCO(2) as illustrated by their reliability coefficients, 0.95 and 0.86 respectively. The biggest source of variation in measured CO(2) for both devices was inter-subject differences, followed by variable oxygen flow rates.

This study suggests that the OA and CM can prove useful for respiratory monitoring and oxygen delivery in spontaneously breathing volunteers, and the OA could potentially be used as an alternative to the conventional methods of oxygen delivery and CO(2) sampling in patients.