A new method of obtaining samples of the respiratory gases in animals. A demonstration

Abstract

I wish to demonstrate a new method of obtaining a sample of air from the lungs, bronchi and trachea of the dog. Chloretone, dissolved in olive oil, is given intraperitoneally. The animal is tracheotomized and a T-shaped glass cannula is introduced. A Meltzer pleural cannula (new form) is placed in each pleural cavity. The intrathoracic negative pressure is then restored and the pleural spaces tested for air-tightness. It should be possible to maintain the negative pressure indefinitely. If any change occurs, it must be in the direction of an increase owing to the absorption of gases through the pleuræ.

Both pleural cannulæ are now connected with a source of air pressure. A small-sized rubber bag is then attached to the horizontal portion of the tracheal cannula. The bag is thoroughly exhausted. The cocks of the pleural cannulæ are now opened. At the end of an expiration, the upright portion of the tracheal cannula is quickly clamped, the air pressure is turned on and the bag opened. A mercury valve is provided so that the desired pressure cannot be exceeded. The lungs collapse. Their contents are forced into the trachea and rubber bag. A portion of the air remains in the bronchi and trachea. The sample therefore approximates the total air.

It has been found that when no precaution is observed to maintain the body temperature, very uniform percentages of carbon dioxid may be obtained. Five experiments have been made thus far. In each experiment the carbon dioxid exhibited uniformity, either immediately or after a preliminary period of fluctuation. The periods of constancy ranged from one and a half to three and a half hours. In three experiments in each of which 8 determinations were made, the maximum deviation from the average was ± 3.0-3.5 per cent.; in one experiment, in which 7 determinations were made, the maximum deviation from the average was ± 2.4 per cent.; in another experiment, in which 5 determinations were made, the maximum minus deviation was 0.5 per cent. and the maximum plus deviation 1.4 per cent.