Monday, March 14, 2011

Anesthesia Machines: Bellows vs. Piston

Correspondence 2008.

Attached are three documents:

1. Article on gas consumption in bellow driving anesthesia machines, comparing both Draeger & GE, this is one of the main reasons Draeger switched to a piston (to conserve on fresh gas, allowing for minimal flow anesthesia < or = 1/4 liter total fresh gas flow).

2. Abstract comparing the Apollo (piston) & Aisys (bellows) in regards to the accuracy of tidal volume delivery, with the new technology the Aisys can also accurately deliver both large & small tidal volumes. 

3. A letter I wrote to a customer on the limitations of the (Draeger's) Narkomed 2B (an older bellows machine) in regards to ventilating the morbidly obese patient. 

This weekend I tried to find white papers comparing the bellows vs. the piston design & the only significant article is the abstract attached. I believe based on evidence based medicine there is little difference between the piston tidal volume deliveries vs. the bellows as long as it is a newer generation machine (Aisys) that calculates for leaks & circuit compliance. Conversely, in regards to gas consumption I believe you would have significantly less gas consumption utilizing the Apollo. 
I hope this helps I didn't want to give you any false statements, this article search additionally gave me new information.

1.Klemenzson, G. & Perouansky, M. (2004). Contemporary Anesthesia Ventilators incur a Significant “Oxygen Cost”. Canadian Journal of Anesthesia. 51 (6): 616-620.

2.  Anesth Analg. 2008 May;106(5):1392-400. Do new anesthesia ventilators deliver small tidal volumes accurately during volume-controlled ventilation?

3. Richey, S. (2007). Determinants and limits of the Draeger Narkomed Anesthesia machine in regards to ventilating the morbidly obese patient. Correspondence.