Direct Determination of Luminal Diameter Changes in Intrapulmonary Airways

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Abstract
A method is described for the direct measurement of changes in luminal diameter at all levels of the airway. Using this method it was found that (i) abrupt bronchiolar collapse occurred in the preterminal and terminal bronchioles once the luminal diameter was reduced to a critical level; (ii) decreased temperatures resulted in airway narrowing which was reversed by increasing the temperature to above 25 °C; as a rule, airway narrowing followed a cranial to caudal direction, with higher concentration of a drug being required to close the peripheral airways; (iii) bronchodilators except Carbuterol had no effect on resting bronchial tone or on acetylcholine-induced constriction in the absence of α-adrenoceptor blockade; (iv) at 35 °C rhythmic waves (frequency 6–20/min) were observed; these waves travelled from the periphery in a cranial direction.