Army sources say the use of nitric oxide (NO) in the management of high altitude sickness is extremely effective and had been in vogue in the western countries for over a decade. It has been introduced in the country only now.

Rapid ascent to altitude above 2,500 meters leads to the symptoms of Acute Mountain Sickness (AMS), severe enough to limit normal activity in majority of the people. "Severe AMS, which may represent early stages of High Altitude Pulmonary Oedema (HAPO), usually progresses and may be fatal unless treated aggressively," an Army doctor said. "At present, the only effective treatment of HAPO is immediate decent to lower altitude and to some extent, administration of oxygen," he added.

HAPO, in simple terms, occurs when the lungs get filled with fluids, which exert pressure on the thin-walled blood capillaries carrying de-oxygenated blood into the lungs, thereby constricting them and restricting the movement of blood. NO acts as a vasodialator, that is, helps dilate the pulmonary blood vessels, allowing blood to flow.

The Defence Research and Development Organisation (DRDO), in collaboration with the High Altitude Medical Research Centre (HAMRC) and the University of Minesotta, USA, had earlier carried out a programme to ascertain the effectiveness of NO in the treatment of HAPO, sources said.

During the two-phase research programme, conducted on soldiers suffering from HAPO, they were administered 50 per cent oxygen containing 15 parts per million NO for a specific period. Various parameters including blood pressure, pulmonary arterial pressure, blood pH, oxygen saturation as well as heart and respiratory rates were studied. "It was found that recovery in pulmonary arterial pressure, clinical symptoms and radiological clearances were much better in these cases than the control group where oxygen without NO was administered," a source said.

Doctors, however, caution that NO being a toxic gas, monitoring the concentration being administered is of vital importance. "On the other hand, its side effects, called systematic hypotension and methemoglobinemia, are rare," a doctor said.

While the use of NO is to be standardised in the management of HAPO cases in all military hospitals concerned with tackling high altitude sickness, it is also in the process of being introduced in the treatment of certain other respiratory diseases in the plains.