does adding alternate flow sources add to Vt on vents?

March 01, 2010, 12:01 PM

If you add flow from an alternative source to PB 840 or Servo 300, the expiratory TV reads higher. Is this due to added flow to expiratory sensors, or actual addition to VT?

March 02, 2010, 02:06 AM

JeffWhitnack

Both. Flow is just volume over time.

March 02, 2010, 02:11 AM

JeffWhitnack

Oh but forgot. During the insp time, when the exp valve is closed, the flow will be part of the VT. So if the insp time is 1.0 seconds and the flow is 10 liters/min then you'll get a VT addition--gee it's late and I think it's 167cc's?. But during the exp time that same flow is going and then that will be displayed as well. So the displayed VT is then the vent VT, the insp time addition to the VT, and the "fools gold" VT during the total exp time.

March 02, 2010, 09:17 AM

dentonrrt

quote:
dentonrrt
Junior Member
Posted March 01, 2010 02:01 PM
If you add flow from an alternative source to PB 840 or Servo 300, the expiratory TV reads higher. Is this due to added flow to expiratory sensors, or actual addition to VT?
Posts: 1 | Registered: March 01, 2010

JeffWhitnack
Member

Posted March 02, 2010 04:06 AM Hide Post
Both. Flow is just volume over time.
Posts: 171 | Location: Palo Alto, CA USA | Registered: November 15, 2002

Ignored post by JeffWhitnack posted March 02, 2010 04:06 AM Show Post

JeffWhitnack
Member

Posted March 02, 2010 04:11 AM Hide Post
Oh but forgot. During the insp time, when the exp valve is closed, the flow will be part of the VT. So if the insp time is 1.0 seconds and the flow is 10 liters/min then you'll get a VT addition--gee it's late and I think it's 167cc's?. But during the exp time that same flow is going and then that will be displayed as well. So the displayed VT is then the vent VT, the insp time addition to the VT, and the "fools gold" VT during the total exp time.
Posts: 171 | Location: Palo Alto, CA USA | Registered: November 15, 2002

Ignored post by JeffWhitnack posted March 02, 2010 04:11 AM Show Post

thanks, Jeff. I appreciate the response.

February 18, 2011, 01:11 AM

Cpap

[QUOTE]Originally posted by dentonrrt:
If you add flow from an alternative source to PB 840 or Servo 300, the expiratory TV reads higher. Is this due to added flow to expiratory sensors, or actual addition to VT? [This is a very Old concept and I believe if we search the Artifacts we should find older discussions on this Topic.]

December 09, 2011, 04:28 PM

respir8er

Adding a supplemental gas to a ventilator circuit will almost always increase the delivered Vt. Check your peak pressures during the tx.

January 12, 2012, 09:06 PM

abel

Ofcourse it will, but the actual VT the patient received can not be measured, I think the actual VT is between the VTi and VTe, so most ventilator manufactures do not suggest adding foreign flow into ventilator system. For doing this will disturbance the normal work of ventilator.