Another five years has snuck up on us again, and the American Heart Association (AHA) is about ready to announce their big (and little) changes for the 2015 Guidelines for CPR and ECC. These guidelines will are based on international research and data that been compiled over the past five years.
One such piece of research takes a look at the effect of negative thoracic pressures in relation to high quality CPR. Negative pressures occur in the lungs specifically when you exhale. Once your lungs are empty, there is a negative pressure (vacuum) that naturally sucks air back into the lungs.
These negative pressures are also pulling blood through the lungs and oxygenating the blood. Without the pressures, you can circulate blood all day long, but the blood won’t get oxygenated and won’t deliver oxygen to the rest of the body.
Part of this physiology is why AHA tells us to allow for full recoil of the chest. Not only do we want the heart to be able to completely refill with blood, but we also want the negative pressure in the chest to have full affect. Negative pressures exist until the lungs have fully recoiled to their normal position at which point the negative pressures neutralize.
Researchers have found that if the chest forcibly pulled up past the neutral point that it creates more negative pressure. This theory was first analyzed by a cardiologist when a teenager was found doing CPR on someone with a toilet plunger. The suction of the plunger pulled the chest past the neutral point and made for better oxygenation of the heart, brain, and other vital organs.
Now there are several devices available that look similar to toilet plungers but are intended for doing CPR. Two of the most notable devices are the Lucas and the ResQPump system. The principal is the same, however, the Lucas is an automated device and the ResQPump is manual. This method of CPR is formally known as Active-Compression-Decompression. Decompression is the action of pulling the chest past the neutral point.
Without a doubt, data is showing us that these devices are making a difference. Not only are they creating a positive effect, but the Lucas specifically provides consistent high quality CPR that was often lacking even among the most proficient team of rescuers.
One last device that takes negative pressures to another level is know as the ResQPod. This device is produced by the same manufacturers as the ResQPump system and essentially double the efficacy when used in conjunction. The ResQPod is know formally as an Impedance Threshold Device (ITD). This device could be best described as a selective one-way valve.
The ITD hooks into your bag-valve-mask and allows air to pass when forcibly ventilated with a BVM. However, in between breaths while compressions are being performed, the ITD prevents air from passively going into the lungs. It only allows are to go out when compressions are compressing the lungs.
If the lungs are not filling with air but ACD is occurring, then you have a more significant negative pressure environment. The more negative pressure, the better their chances of survival and return on spontaneous circulation.
Perhaps the explanation of the anatomy and physiology of these 2 devices seems complex, but don’t let that scare you from incorporating them the next time you perform CPR. The use of an ACD and ITD are very simple and have been making profound impacts on patient’s lives.