In 1909 Meltzer and Auer, working with dogs, found that the ventilation of the alveolar air could be accomplished, and that an animal could be kept alive and in good condition by a stream of air blown through a tube passed down the trachea nearly to the bifurcation. Even after curare to suspend all action of the striated respiratory muscles the animal could be kept alive for hours. In fact, they had discovered a wonderful method of performing artificial respiration.

Then they found that, by passing the stream of air over ether, they could anesthetize the animal, and at the same time keep up a sufficient degree of positive intrathoracic pressure to prevent collapse of the lungs in intrathoracic surgery. This method has now become extensively employed for anesthesia with ether and for nitrous-oxide-oxygen anesthesia.

After a preliminary anesthesia to depress the laryngeal reflex a silk-woven catheter, about No. 22 French, is inserted through the glottis until the teeth are at a mark 26 cm. from its end. Then, with a bellows or pump, operated by foot or power, the air is passed through or over ether in a bottle into the trachea. The gases from the lungs make their escape around the catheter, and this should be small enough to leave ample room in the glottis. The apparatus should bear a manometer for recording the pressure, and the positive pressure should not, in ordinary operations, exceed 10 mm. of mercury, and in intrathoracic surgery 20 mm. At the end of the operation the ether is shut off, and air insufflated for several minutes. From three to six times a minute the air-stream should be stopped to permit collapse of the lungs and the expulsion of some Co2 which tends to collect in the alveoli. The ether-air vapor should be of about 6 or 7 per cent. strength.

The patient makes light respiratory movements, but the oxygenation of the blood goes on, irrespective of respiration. The color of the skin is good, and the pulse is normal. If the patient vomits on the table, or if blood runs down the throat, as in mouth operations, the positive pressure of the escaping gases prevents aspiration of the foreign material into the lungs.

Following the anesthesia, it is claimed, there seem to be no bad effects from the tube or the ether vapor, either upon the glottis, the trachea, the bronchi, or the lungs, even in the presence of a respiratory disease; and usually there is no nausea or vomiting. But in intratracheal insufflation experiments, Georg regularly observed injuries to the alveoli and bronchioles, whether the pressure was low or high. There have been a few deaths reported, generally due to rupture of the lungs from too great pressure, or to puncture of the trachea by a tube that is too long. This last produces interstitial emphysema. These dangers can be eliminated by having a short tube, a manometer, and a careful anesthetist, or by a safety valve set at 20 mm. of pressure.

Githens and Meltzer (1911) showed that double the lethal dose of strychnine given during ether anesthesia by intratracheal insufflation did not cause the death of a single animal.

Pharyngeal insufflation is produced in the same way as intratracheal, the vapor, however, being carried merely to the pharnyx by a Y tube bearing on each fork an 18 Fr. soft-rubber catheter with double eyelet (the Connell nasopharyngeal tube), to be passed through the nostril.