Curare Cleft as a result of partial disconnection of main stream CO2 sensor
Tripathi et al reported that a partial disconnect of a main stream capnometer also can present a "cleft" on the expiratory plateau during controlled ventilation.
The authors provide the following hypothesis.
In the presence of the disconnection, the inspiratory capnogram is unchanged. During expiration, the initial high expiratory flow rate will be sufficient to close the inspiratory valve and allow exhaled gas to flow through the CO2 analyzer giving rise to the normal looking expiratory plateau. However, a portion of expiratory gases exit through the leak. This reduces the measure expired tidal volume. As the expiratory flow rate decreases, leak flow will cause pressure to decrease in the circuit, allowing expiratory valve to close prematurely and facilitate flow of inspiratory gases. The flow of fresh gases flow from the inspiratory limb reduces the measured CO2 at the analyzer. As the fresh gas flow causes pressure to rebuild in the circuit, the expiratory valve will reopen, allowing the further movement of alveolar gases pass through the CO2 analyzer.
Tripathi M, Tripathi, M. Partial disconnection at the main stream CO2 tansducer mimics
'curare cleft" capnogram. Anesthesiology 1998;88:1117-9.