Gamow bag

A pressure bag, even hyperbaric chamber is a device for the treatment of altitude sickness. It is basically a portable ( De ) compression chamber, by means of which the patient is exposed to a higher air pressure.

Principle of operation

A pressure bag is an inflatable air-tight envelope, which is large enough to accommodate a recumbent person. The patient is completely placed in the bag and which is then sealed. By inflating the bag with a foot pump, the internal pressure is increased, which corresponds to a physiological descent of the patient to a lower altitude. The extent of the achieved simulated descent is next to the reached pressure also depends on the height above sea level, since the decrease in air pressure with altitude is not linear (see Barometric height formula ): therefore, a greater decline in higher altitudes can be simulated. So you can achieve with a pressure of 200 millibars at an altitude of 4000 meters air pressure as at 1650 meters, at 6,000 meters can be a descent down to 3100 meters and 8000 meters to simulate up to 4500 meters.

The improved oxygen supply by the increased oxygen partial pressure in the interior leads to an improvement of the symptoms of Acute Mountain Sickness (Acute Mountain Sickness, AMS), the high altitude pulmonary edema (high -altitude pulmonary edema, HAPE ) and the altitude cerebral edema (high -altitude cerebral edema, HACE ).

Areas of application

Drug of first choice in the case of altitude sickness is always a real descent. The pressure bag is only used, if, for instance due to the poor condition of the patient is no longer possible. Pressure bags are available among other high-altitude refuges or can be carried on major expeditions. For small expeditions or treks, however, the carrying of pressure bags is not usual due to the heavy weight and high cost.

As a clear contraindication to pressure treatment only as respiratory and circulatory arrest.

Application

The correct implementation of a treatment with the pressure bag requires training of workers, but also exercise the patient, for example, to avoid claustrophobic conditions.

In preparing the treatment must be given to a balanced thermoregulation: Both hypothermia in the cold mountain air and overheating in direct sunlight must be avoided, the patient's clothes must the rising humidity in the bag well tolerated. Also needs a ground available, which allows to avoid damage to the bag. Before inclusion in the sack, the patient must perform a pressure compensation, in the case of a closed eustachian tube, the administration of nasal drops is displayed that can decongest the nasal mucosa and facilitate the pressure adjustment. Then the bag is laid flat or slightly-high headboard, the patient enrolled and inflated the bag until the air escapes through the pressure relief valves.

A patient is in the interior of the bag, it must be ensured by continuous pumping for adequate fresh air supply. This pump can be a great burden on the workers in the high altitude, it must usually more reliable and experienced helpers are available. A removal during the stay in the bag is difficult and usually impossible. During the treatment the patient has to be monitored through a window.

Usually, the patient is left as a maximum of two hours in the bag before the air slowly released and a renewed check is carried out of its condition. This time is sufficient for often such a strong improvement in the symptoms that an independent descent or at least a removal is possible. This should be done as quickly as possible, since the effect of therapy with the pressure bag usually does not last long. If necessary, the treatment can be repeated.

Construction forms and models

Hyperbaric chambers for treatment of acute mountain sickness have been known for a long time, especially in the Asian high mountains they are used in the military for a long time. The first mobile hyperbaric chamber was introduced in 1919 in Germany. However, only in 1988 presented Igor Gamow of the University of Colorado the first portable pressure bag in the modern sense.

Named after its inventor Gamow bag has a cylindrical shape, is made of airtight nylon fabric and has to enter and exit a longitudinal zipper. Side view windows allow visual contact. Two pressure relief valves limit the pressure to 138 mbar ( 2 psi). The bag weighs 7 kg.

The Certec bag is a French brand, which is 4.8 kg lighter, but its double hull also more stable than the Gamow bag. The maximum pressure is 220 mbar higher than the Gamow bag, a sideways mounted zipper to facilitate entry.

The Australian Portable Altitude Chamber ( English for " portable altitude chamber ", PAC) is made of coated fabric and is considered billigster pressure bag. He is a little more spacious and easy to enter through its all-round zip. The maximum pressure is 138 mbar, but can also be set lower if needed (such as for pressure equalization problems through closed eustachian tube).

Additional treatment and alternatives

Basically, in altitude sickness usually bottled oxygen or a combination therapy of oxygen and medicines the drug of choice. An advantage of the pressure bag to oxygen, however, is that it can be operated with muscle strength and can be refilled indefinitely from the ambient air. The pressure bag can be combined by an oxygen cylinder is taken into the sack with drug therapies or oxygen.

For cases in which the patient must be supervised during treatment, there are now also over-pressure bags in tent size that can still accommodate an assistant next to the patient. Another new development is the TAR helmet ( Thin Air Rescue), limited to the head region of positive pressure bag, which can be operated by the patient himself and maintains his mobility during treatment.