Strategic compulsions necessitate the regular deployment of soldiers at high altitudes of the Himalayan regions thereby exposing them to reduced atmospheric pressures. The reduced atmosphere and the harsh mountain environment at high altitude, being alien to low Landers, evoke a series of physiological responses in human system. There is a wide variation in both the speed of onset and severity of physiological responses and also the height at which they develop. Sudden exposure to high altitude is detrimental to the performance, both physical and mental, and in some cases may lead to dreaded condition like High Altitude Pulmonary Oedema (HAPO). HAPO is a condition in which fluid accumulates in lungs causing severe illness and is a serious consequence of failure to acclimatize to hypobaric and hypoxic atmosphere of altitude greater than 2700m above mean sea level. This condition is characterized by breathlessness, abnormally rapid heartbeat, mild cough, dry cough to blood stained sputum, and raised pulmonary artery pressure.
Condition of HAPO can be reversed by increasing the alveolar and arterial oxygenation either by providing supplemental oxygen at higher pressure or by descent to lower altitudes. Supplemental oxygen may not be readily available in a combat situation; while rapid descent, the treatment of choice, is often not possible either due to the topography, adverse weather or non-availability of transport. In such a scenario, portable hyperbaric chambers present an inexhaustible, light weight source of additional oxygen pressure which leads to rapid relief of symptoms of high altitude illness. Portable hyperbaric chambers allow the environmental pressure around the subject to be increased equivalent to a descent of up to 8000 to 10000 ft.
Portable chambers are near cylindrical in shape and are made out of medium to heavy weight, impermeable coated fabric with an air-proof zipper to accommodate a patient in supine position. Such chambers are integrated with various valves to facilitate the ease of operation and safety. The inflation of the chamber and the maintenance of the pressure are facilitated by a foot-pump alone or in combination with power operated compressor and a pressure sensing unit. Years of R&D effort coupled with the evaluation has culminated in the development of an automated bag, a unique feature vis-à-vis the imported bags. The operating pressure inside the developed bag is 2.5psi vis-à-vis 2psi of the above mentioned internationally available bags thereby enhancing the virtual descent of the patient and hence the recovery. The developed bag is 2.1m long, 0.65m dia at the head end and 0.5m dia at the foot end, with a volume of approximately 600ltr to accommodate the HAPO patient even with the multiple layers of cold-clothing. The bag is provided with a pre-set leak control valve to bleed continuously at a rate of 20lpm in order to avoid the build-up of carbon dioxide inside the bag and a safety pressure relief valve in order to prevent the excessive pressure inside the bag. Several user friendly features have been incorporated in the developed bag. All the materials have been selected to withstand sub-zero temperatures encountered in the usage.