ISSN:
1432-1750
Source:
Springer Online Journal Archives 1860-2000
Topics:
Medicine
Notes:
Summary The marked inspiratory reaction elicited by collapse of the lungs during a pneumothorax is essentially different from the weak inspiratory effect brought about by decrease of lung volume during expiration under normal conditions. The latter effect is mainly a release from the inpiratory inhibition exerted by pulmonary stretch receptors firing at high rates; a release which is reinforced on the one hand by post-inhibitory, i.e., inspiratory rebound activity, on the other by moderate activation of inspiration due to low firing rate of the stretch receptors. The marked inspiratory reaction is, however, elicited by pulmonary deflation receptors that discharge through slowly conducting afferent fibres. It should be regarded as a nociceptive reflex preventing pulmonary collapse, or local effects such as atelectasis and pulmonary compression. The present investigations show that the marked inspiratory reaction plays an important role during experimentally produced asthma bronchiale. 1. In guinea-pigs sensitized to egg albumen, reversible bronchial asthma is produced by inhalation of antigen aerosol. At the onset of raised bronchial resistance, an inspiratory reaction characterized by tachypnoea and increase in lung volume occurs. It is mediated by afferent vagus fibres subserving inspiration and is modified at later stages by chemical factors. 2. This vagal inspiratory reflex is due to morphological pulmonary changes, i.e., emphysema and atelectasis. These disturbances of the mechanics of breathing produce increase of intrathoracic pressure during expiration and hence compression of the lungs; this in turn leads to excitation of vagal deflation receptors which sets up the inspiratory reaction and modifies the Hering-Breuer inflation reflex. 3. The inspiratory reaction plays an important role in the cycle of morphological pulmonary changes and physiological reactions that underlie an asthma attack, and represents a defence mechanism of the lungs constrained within the thoracic cage.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF02090684
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