RE: Re: Autopulse - Underlying Science

[Guest guest]

Fort Bend County carried them until a few yeas ago....When I first went to

work there....in 2001. When I saw it....I had know idea what it was....I

guess that shows my age.

MG

Re: Re: Autopulse - Underlying Science

Speaking of Thumper's, does anybody still use them? We don't see them much

over here in the NE.

Tater

Kenny Navarro wrote:

>>> So we are using the pressure on the vessles within the chest to

pump the blood vs the elasticity of heart muscle itself to pump the

blood? <<<

Danny,

There are two major theories to explain forward blood flow in closed

chest compressions, the cardiac-pump theory and the thoracic-pump

theory.

The cardiac-pump theory holds that blood moves as the result of

squeezing the heart between the sternum and the spinal column during

CPR. Blood is prevented from retrograde, or backward flow by

closing of the AV valves.

The thoracic-pump theory argues that forward blood flow occurs as a

result of changes in the size of the thorax. If you push down on

the chest, the pressure within the thoracic cavity is increased and

transmitted to all intrathoracic structures, including the heart.

This rise in intrathoracic pressure forces blood into the aorta (and

eventually the coronary arteries) and ultimately to the brain.

Blood is prevented from backward flow by closing of valves at the

thoracic inlets.

There is some evidence to suggest that both theories may be

responsible (at least in part) for forward blood flow.

The old style Thumper device took advantage of the cardiac-pump

theory by direct compression of the heart. The Autopulse exploits

the thoracic pump theory by changing the size of the thorax (to a

much greater degree than conventional closed chest compression) by

squeezing from anterior-posterior and laterally.

On the near horizon, there MAY be other devices that can exploit the

thoracic-pump theory, including the LUCAS device and the inspiratory

threshold device.

Dr. Bledsoe is correct (in my opinion) that the more clinically

relevant trial (the one stopped for ethical reasons) appears to show

harm compared with the observational study (Richmond).

Dr. Ornato reports that a third trial is planned but IRB approval

(as mentioned by Dr. Bledsoe) may be difficult to obtain.

Kenny Navarro

UT Southwestern