Korpás J

Changes Induced by Severe Hypoxia in Respiratory Defence Reflexes in Anaesthetized Cats

The authors studied the effects of progressive isobaric hypoxia (FO2 = 0.11, 0.07, 0.06, 0.05, 0.04 and 0.03) on respiratory defence reflexes elicited by mechanical stimulation of the airways in 10 pentobarbital-anaesthetized cats. The intensity of the expiration reflex was already significantly reduced at a hypoxia level of only FO2 = 0.11; the intensity of cough also showed a tendency to decrease. The number of efforts and the intensity of both tracheobronchial (TB) and laryngopharyngeal (LPh) cough fell significantly in hypoxia of FO2 = 0.07. On an average, cough could no longer be elicited at PaO2 = 2.0 +/- 0.06 kPa. The aspiration reflex was found to be the most resistant to hypoxia, and could still be elicited just before hypoxic apnoea developed. During hypoxia with FO2 ranging from 0.21 to 0.06, minute ventilation increased, while the intensity of respiratory defence reflexes diminished. TB cough could not be elicited during hypoxia until the breathing was depressed. It can be seen from the results that the regulatory mechanisms responsible for the intensity of respiratory defence reflexes are less resistant to the consequences of an inadequate systemic oxygen supply than the mechanisms controlling ventilation.

Influence of Experimentally Induced Airway Inflammation on the Reactivity of Cat Lung Parenchymal Strips to Histamine and Acetylcholine

The reactivity of cat lung parenchymal strips to histamine and acetylcholine in vitro was studied at various stages of inflammation of the airways induced experimentally by the intratracheal administration of turpentine oil or Staphylococcus aureus, both in aerosol form. With histamine, the contractile responses of the lung strips were enhanced depending on the stage of turpentine oil inflammation. Similarly, the lung strips responded more to histamine in the staphylococcal inflammation. The reactivity of the lung strips to acetylcholine remained mainly unaffected by either type of inflammation.

Reactivity of Cat Tracheal Smooth Muscle to Histamine under Conditions of Experimentally Induced Inflammation

The reactivity of cat tracheal smooth muscle to histamine in vitro was studied at various degrees of inflammation of the airways induced experimentally by the intratracheal administration of turpentine oil or Staphylococcus aureus, both in aerosol form. Tracheal smooth muscle preparations from the control animals did not respond to histamine in doses of 10(-9)-10(-3) mol X 1(-1). In tracheal preparations from three groups of cats with turpentine oil inflammation induced 24 h, 48 h and 15 days previously, histamine caused contractions in 20, 70 and 24% of the cats, respectively, according to the degree of inflammation. All tracheal preparations from cats with staphylococcal inflammation responded to histamine by contraction. Atropine, acetylosalicylic acid and phentolamine did not abolish histamine contractions in tracheal preparations, but clemastine did.