Monitoring tidal volume on HFOV

[ammar]

Dear friends,
I'm very happy to join this beautiful forum.
we are great users of HFV ventilators (SM 3100 A and B, Stéphanie, SLE and the BBL 8000) and we will conduct a work about the efficiency and safety of this ventilators. I ask if some one have a reference of a device that make monitoring of tidal volume possible at the distal point of the circuit and thanks.

[drashishjain2000]

I dont think the tidal volume in a hfov can be measured at the distal end

[JACK]

In HFOV, usually the tidal volume delivered will be less than the dead space. So even if you do measure it , it will not give any useful info.

[RespSci]

Mentioned in articles analysing HFOV tidal volumes are the Florian (Acutronic) and the 2100 VPM (SLE). Both are hot wire anemometers and accurate within the range of neonatal frequencies used with HFOV. I have used the Florian but have not seen the SLE. Looking at the Acutronic and SLE websites, I could not find these products listed, apart from spare parts for the Florian.

[Skysurfer]

We are using the SM 3100 A and are measuring our Vte`s via Florian with the technique mentioned above. We are more than satisfied with our equipment and i think it is useful if you want to adjust the settings until you reach the "right" frequency. In CMV, ventilation is defined as: F x Vt, in HFOV, ventilation is defined as: F x Vt to the power of 1.5-2.5.
Therefore changes in Vt have a larger impact on ventilation than changes in frequency !
The other thing is, that there exists a resonance frequency of the lung in which optimal ventilation (co2 removal) occurs. If you don´t measure the Vt, you can hardly be able to search for the "right" resonance frequency....
The resonance frequency varies by the size of the lungs and the degree of lung injury. For more detailed information pls see the powerpoint presentation of the PICU-COURSE at the Society of Critical Care Medicine homepage.
Hope that helps

Norbert