Gas Exchange

Datex-Ohmeda gas exchange measurements M-COVX Module

Q: Can M-COVX be used with active humidification?
A: Yes.D-O has developed a new disposable D-lite+ flow sensor for humid conditions. If an HME is used both the new D-lite+ and the reusable D-lite can be used.

Q: Can M-COVX module be used with pediatrics?
A: It can be used with pediatric patients having Minute Volume more than 700ml and respiration rate less than 35.

Note! If there is a leak around the endotracheal tube the volume measurement is not accurate for gas exchange measurement. If high by-pass flow is used in the ventilator, both gas concentrations and volume will not be reliably measured.

Q: Can M-COVX be used in anaestesia connected to AM?
A: Yes, it can be used.

Q: Why does the RQ value sometimes show unphysiological values such as RQ < 0.6?
A: Usually it is due to non- steady state i.e. ventilator settings have been changed, FiO2 changed, irregular ventilation where FRC varies.

Q: Why aren’t VO2 and VCO2 always updated every minute?
A: The updating is based on the fact, that it needs 60sec correct data. In practice the updating interval can be longer, i.e. when zeroing occurs or some breaths are not detectable (flow changes can not be detected correctly i.e. in small and fast spontaneous breathing efforts).

Q: Can 3 m gas sampling line be used with M-COVX?
A: No, because the synchronization of the gas and flow data is based on 2 m sampling line’s response time. Using 3m sampling line causes 5-10% error in VO2 and VCO2 readings.

Q: What is the total dead space and resistance with HMEF and D-lite +?
A: Dead space = 86,5ml Resistance = 4.5cmH2O at 60l/min flow

Q: Does Nitric Oxide (NO) administration interfere with M-COVX measurements?
A: No. The amount of NO is so minimal.

Q: Can D-lite + be connected during administration of nebulized drugs?
A: D-lite and HME(F) should be disconnected while using nebulizer. After administration D-lite + can be reconnected immediately.

Q: Why is the Compliance value in the S/5 monitor not the same as the value at the ventilator?
A: The monitor measures directly at the ET-tube and reflects more closely follows compliance of the lung.

Hoses and other equipment between the patient and the ventilator influence the values measured in the ventilator.

Q: Why are the values not correct, if a ventilator with high continuous flow?
A: Due to high flow rates, as is found in some ventilators, the expiratory gas concentrations will dilute before measured (too low values are detected) and the high flow creates turbulence in the Y-piece. This causes a pressure difference over the D-lite + and leads to erroneous readings.

This problem can be avoided by using an extra connector of 4-7ml between Y-piece and D-lite +.

Note, that the extra dead space may cause slightly inaccurate gas exchange values.

Last updated: 1 March 2001Created
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