Nasal Cavity Dimensions in Guinea Pigs Measured by Acoustic Reflections

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Abstract
Acoustic reflections have been used in adult humans to determine nasal cavity dimensions in terms of cross-sectional areas as a function of the distance from the nostril (J. Appl. Physiol., 66:295–303, 1989). In order to measure nasal cavity dimensions in guinea pigs, we modified equipment for use in humans by decreasing sound tube dimensions, increasing sampling frequency, and applying a special nosepiece. We measured 5 guinea pigs (Duncan Hartley strain, 500 g) on two days, before and after instillation of epinephrine and histamine in one nostril. In the control measurements, the minimum cross-sectional area of a nasal cavity was 1.1 mm2 (SD = 0.3 mm2), and the volume from the nostril to 20 mm into the nasal cavity was 60 mm3 (SD = 19 mm3). There was a tendency (P < 0.10) for epinephrine to increase minimum cross-sectional area on the treated side and volumes on both sides. Histamine decreased volume on both sides (P < 0.05), but not uniformly between animals. Measurements in a tube with 2 mm internal diameter (area 3.1 mm2) underestimated true area by approximately 30%. The method, therefore, at its present state of development, measures changes in dimensions rather than absolute values. It is concluded that the acoustic reflections technique may be a useful alternative to other, more invasive methods to assess nasal cavity dimensions in guinea pigs, but further studies are necessary to improve and validate the method.

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