THE air we breathe contains 21 per cent oxygen. The rest of it is composed of mainly nitrogen with traces of hydrogen, helium, carbon dioxide and some water vapour.

Had the earth's atmosphere been entirely composed of oxygen, human survival would have been impossible because 100 per cent oxygen is injurious for the delicate lung tissue.

While administering anaesthesia to a patient, after induction, the anaesthetic state is maintained for the entire period of surgery with tiny vapours of volatile anaesthetic agents suspended and carried forwards and downwards in the lungs by a mixture of breathing gases.

This mixture of gases instead of being composed of 100 per cent oxygen only contains 30 to 50 per cent of oxygen and the rest is made up of nitrous oxide, the so-called laughing gas.

This gas not only contributes 50 to 70 per cent to the volume of the mixture of inhaled gases but also possesses some pain-relieving properties.

In my 22 years of anaesthesia practice, I have never witnessed such an acute shortage of nitrous oxide as it is being felt nowadays. Just because of this reason, anaesthesia at present is being conducted in many hospitals with 100 per cent oxygen, which is neither advisable nor desirable.

At the industrial level, nitrous oxide is manufactured by heating ammonium nitrate at high temperatures and is also released as a byproduct in various chemical processes which involve burning of air at a high temperature.

It may be noted that a factory in Multan is the only one producing calcium ammonium nitrate and nitro-phosphate, which have been found to have been used by terrorists for making improvised explosive devices.

Perhaps, the shortage of nitrous oxide has been brought about in the wake of the industrial inspection of the aforesaid factory by the Organisation for the Prohibition of Commercial Weapons.

Measures undertaken by the relevant government departments to ensure compliance with the Chemical Weapons Convention may be the reason why hospitals are running short of this vital gas.

Through this letter I would like to draw the attention of authorities concerned and at the same time request academicians and professional organisations of this specialty of anaesthesia to spare a few moments of their precious time and take up this matter at the highest level.

DR ARIF BAWANY
Karachi