Pre-Hospital CPAP

Thu, 01 Sep 2005 13:48:10 GMT

Many EMS providers are starting to look at pre-hospital CPAP. CPAP stands for Constant Positive Airway Pressure. The best way to describe it is that you place a resistance against patient exhalation to increase pressure inside the lung causing more alveoli to open up and exchange gas. This can be critical when patients have many of their alveoli compromised; exactly the problem when fluid backs up in the lungs to due Congestive Heart Failure. This is usually accomplished through use of a PEEP valve, or Positive End Expiratory Pressure valve, used in combination with high flow oxygen support for the inspiratory phase of respiration..

Patients who receive CPAP in combination with drug therapy in the field often show remarkable improvement quickly. Several agencies have reported that using CPAP, they don’t have to do as many endotracheal intubations.

What is even better is that patients who have had CPAP administered in the field are likely to stay in the hospital fewer days. They don’t have to be weaned off a ventilator because they were never on one. This could dramatically cut the acute care costs for these patients.

I’m been asked a lot lately about what types of CPAP devices are out there which are suitable for EMS use. In response to these questions I would like to share;

My short primer on EMS CPAP technology.

There are currently 3 brands of CPAP devices on the market, in two basic styles. The Caradyne device called the Whisperflow, is owned by Respironics, which is a simple Downs Flow Generator. They make these in two models; one is called a Fixed Flow device which offers no adjustments and provides about 30% Oxygen. The reduced oxygen concentration extends use time because with these Downs Flow type devices, oxygen is consumed very quickly. CPAP devices operate at flows near 100LPM, and a device of this type can burn a D tank in 4 minutes at 100%. The second Adjustable Flow model, offers adjustable flow and FIO2. Unfortunately, you really do not have any way to assess the effectiveness of a given setting.

The second device is made by Vital Signs. It is also available in two models. One is called a Downs Fixed Flow Generator, the other the Downs Adjustable Flow Generator. Both models operate the same way and are virtually identical to the two Caradyne models. The only real difference is the Vital Signs units have a round body and the Caradyne units have a square body.

All 4 of these Downs Flow devices use a CPAP mask assembly that relies on a fixed PEEP valve on the mask. Usually most use 10cm, to start. None offer a pressure gauge to assess proper function of the disposable PEEP valve. All make a lot of noise, particularly in comparison to the third device described below. They also by comparison increase the work of breathing. As most of you know from experience, the CHF patients that wind up needing an ET tube are just plain tuckered out.

The third device is about 2 decades newer in design. Emergent makes the PortOVent CPAPos. This device only flows oxygen during the inspiratory phase; so even at 100% oxygen (which most protocols call for) it uses less oxygen, and reduces the work of breathing. It is also much less noisy. The Emergent device has a better mask, an internal adjustable PEEP valve, and an integrated pressure gauge. There is also a single pressure control knob that in conjunction with the pressure gauge permits carefully titrated application. It is a little more expensive, but you get what you pay for.

One issue that sometimes comes up is size. The Downs Flow devices are much smaller than the Emergent, but this is somewhat misleading. The majority of the bulk you carry is the high-pressure oxygen supply hose and the large CPAP set (mask, hose, and PEEP if required). The reality is all five units are nearly the same size, deployment wise, with the larger Emergent PortOVent CPAP device a few square inches larger and a few ounces heavier.

To sum it up, it looks like CPAP is ready for prime time. The number of CHF patients is increasing. EMS providers are now looking at adding this treatment modality to their protocols. As with any new technology, it is of paramount importance to get familiar with all of the available options.

Paramedic Blog: Technology

Pre-Hospital CPAP