This section is from the book "A Text-Book Of Pharmacology, Therapeutics And Materia Medica", by T. Lauder Brunton. Also available from Amazon: A text-book of pharmacology, therapeutics and materia medica.
Solid powders may be applied to the larynx by insufflation. The insufflator (Fig. 162) used for this purpose consists of a tube curved at one end, and having at the other a piece of india-rubber tubing or an india-rubber ball, by which a powder may be blown through the tube near this end of the tube. There is a small opening in its side through which the powder may be introduced, and this is afterwards covered by a sliding ring or a piece of india-rubber tubing so as to prevent the powder from escaping. The bent part of the tube is carefully introduced into the mouth so as not to cause retching by touching the tongue or soft palate, and, when the end of it points down over the larynx, the patient is told to take a deep breath. At the moment of inspiration the operator forces the powder out of the tube into the larynx, either by blowing through the india-rubber mouthpiece, or by compressing the india-rubber ball. Morphine applied by this method gives more relief than almost anything else in laryngeal phthisis. About one-sixth of a grain is sufficient, and in order to give it sufficient bulk it may be mixed with either starch or bismuth.
Solutions may be simply applied by means of a sponge firmly tied to a piece of whalebone having the proper curve; as the patient inspires this is pushed down the larynx. Doubts have been expressed as to whether the sponge does get through the larynx, but I have seen the crico-thyroid membrane projected forwards by the sponge applied in this manner.
Fig. 162. - Insufflator for applying powders to the larynx. A, piece of india-rubber covering the opening in the insufflator, by which the powder is placed in it. B, india-rubber tube by which the powder is blown out of the insufflator into the larynx. c, curved end of insufflator for introduction into the pharynx.
Nitrate of silver applied in this way gives relief in cases of phthisis, but it is a very rough method, and the application of the solution by means of a brush, with the aid of the laryngoscope, is much to be preferred. When the sponge has not been firmly fixed it has been known to come off and fall into the trachea.
Fluids may be applied by a brush to the larynx, the operator using the brush with one hand and holding the laryngoscopic mirror with the other, while the patient holds his tongue out himself. If the patient is made to take several deep breaths in succession, a slight anaesthetic condition is produced, which renders the operation much more easy.
Caustics are best applied to the larynx by means of a caustic-holder in which the caustic is concealed until it reaches the point of application, when it can be projected by a touch of the finger, and again withdrawn at the wish of the operator.
Solid nitrate of silver may also be applied by heating the end of a partially curved metal rod, then touching the stick of caustic. In this way a uniformly-diffused and minute quantity of the caustic is melted on to the end of the instrument, which is then applied by aid of the mirror.
Liquid may be applied to the larynx in the form of spray, produced either by means of Richardson's apparatus or by a current of steam. The nozzle of the spray-producer may be simply directed towards the pharynx, or the tongue and the cheeks may be protected from the spray by a cylindrical glass speculum.