Cpap

[Christopher]

Bipap is much more comfortable, at least at higher inspiratory pressures.

CPAP should only be used in someone with strong respiratory drive and mechanics, whereas bipap is sometimes used in patients whose minute volume is low. A CHF'er with a moderate exacerbation who is just "tired" for instance. Bipap provides support that more closely resembles AC or SIMV on a ventilator.

I second this. Many of my middle range CHF'ers do far better on BiPAP once we hit the hospital than they were doing on CPAP in my truck. Humans weren't built to breathe via positive pressure, and BiPAP simply provides a more natural augmentation.

We've just added CPAP for COPD'ers, so I haven't seen any direct effects, but hospital experience tells me BiPAP is the preferred NIPPV for Asthma/COPD.

Anyways, great points.

 

[18G]

Sorry for the late response. Whoops, meant cmH20.

I think his sats may have gotten worse during my transport because of the lower FiO2 with my CPAP. The ER probably used 100% on theirs. That's the only thing that I can think of at least.

He had a silent chest on scene and was still really struggling even when his sats came up to 100% in the ER. I think he had a really bad exacerbation of his emphysema, and popped a bleb before we got there. The CPAP may have made it worse, especially with the higher pressure that the ER used. It's a good thing the transport was short. There would have been no way to figure out without an X-ray that he had a pneumo, and the treatment would only have made it worse.

If the patient had a "silent chest" neb treatments wouldn't have been real effective at all. Did you consider IM epinephrine or Brethine?

 

[Brandon O]

No, they are two entirely different units of measure for pressure.

1mmHg = 1.35cmH2O

Ventilatory pressures have traditionally been measured in centimeters of water. It actually represents the pressure exerted by a column of water that is X centimeters tall. I'm not sure the exact reason, but I know that in the dark ages of the mid 60's, PEEP valves could actually be fashioned using a water column in the ventilator circuit. Even today, water seals are used in chest tube systems - on rare occasions you might see chest tube bottles with water seals (what a total PIA those were). We used to measure CVP using a water column device, but that has been abandoned for electronic transducers that usually display mmHg.

I was recently wondering this exact question, and some critical care folks set me straight, as you explained very well. What's cool is that not only did some of the old circuits use a water column to create the PEEP, in some, you'd simply lower the expiratory tube into a basin of water by so-many centimeters -- so to exhale you need to first displace that same weight of water. The More You Know...

You can still measure CVP in cmH2O by estimating JVD height ;-)