Ventilation, cardiac frequency and pattern of breathing during exercise in men exposed to O-chlorobenzylidene malononitrile (CS) and ammonia gas in low concentrations.

Ventilation minute volume, tidal volume and cardiac frequency during submaximal exercise have been measured in healthy young soldier volunteers exposed to O-chlorobenzylidene malononitrile (CS) and ammonia gas in concentrations respectively of 0.16 to 4.4 mg.m(-3) and 50 to 344 mg.m(-3). The response of ventilation minute volume to the two gases is apparently similar; both gases cause a reduction of, on average 6%. With low doses this reflects a diminution in respiratory frequency whereas with higher doses it is due to a reduction in tidal volume which is accompanied by tachypnoea. The findings may result from stimulation successively of receptors in the larynx and of irritant receptors in the large airways of the lung. The pain which is a feature of exposure to CS but not to ammonia is due to stimulation of other so far unidentified receptors. Neither gas has a direct effect upon the exercise cardiac frequency.