Abstract
Advantage has been taken of the fact that the opacity of tissues to light varies with the blood content, to record photoelectrically the changes in the blood content of the nasal septum.
The arrangement used (shown schematically in Fig. 1) is essentially an adaptation of the photoelectric plethysmograph for the finger, previously reported. 1 Illumination of the septum is provided by a small ophthalmoscope bulb inserted in one nares. Local heating is largely prevented by a heavy metal cap which, placed over the bulb, conducts the heat away to the lamp carrier. Local heating may be practically eliminated by using a mirror arrangement which permits the light source to be placed some distance from the nares. The latter method of providing illumination has the additional advantage of offering opportunity to control amplification, independent of septal luminosity, through predetermined decrements in light intensity by means of suitable filters. The light transmitted by the septum is reflected out the other nares by the mirror to the photoelectric cell. The entire assembly is mounted on a dental impression plate which, carried between the teeth, not only provides a rigid mount but also guarantees constancy of alignment with the nasal septum. The mirror and light tubes may be varied in diameter to fit varying nares. Any desired penetration is readily provided. The apparatus is light and comfortable and may be worn for hours without discomfort. Breathing through either the mouth or nose is equally feasible. The photoelectric oscillations are recorded galvanometric-ally on the photokymograph after amplification.
Preliminary observations indicate the feasibility of using the same arrangement for photoelectric plethysmography of the skin of the nose, employing either transmitted or reflected light.
Fig. 2-A shows the volume pulse of the septum so recorded, contrasted with the finger volume pulse (B) of the same subject.
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