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[Functional and morphological changes in the respiratory organs of cats after long-term exposure to pure normobaric
J Hanácek1, M Brozmanová, A Strapková
1Ustav patologickej fyziológie JLF UK, Martin, Slovakia. sd@doktor.jfmed.uniba.sk
Background:
Pulmonary oxygen toxicity is very well known and proved. The influence of hyperoxia on the respiratory reflexes is not known till now.
Main Purpose:
To ascertain if long-lasting breathing of pure normobaric oxygen (PNO) alter respiratory reflexes.
Methods:
34 adult cats of both sexes, weighing 2.5-4.0 kg, were used in two experiments. In the first experiment 16 animals with inserted chronic tracheal cannula (CTC) were used. In the second experiment 18 animals without CTC were employed. Part of animals in both experiments was exposed to PNO (day by day for 2 weeks, 10 h daily), remaining animals were exposed to room air under the same conditions. Side tracheal pressure was recorded in unanesthetized animals of the first experiment. The second experiment was performed in anaesthetised animals (Pentobarbital Spofa, 35 mg/kg, i.p.). Oesophageal pressure and blood pressure in femoral artery were recorded. Cough reflex, sneezing and aspiration reflexes were induced by mechanical stimulation of airway mucosa. Pulmonary chemoreflex was elicited by i.v. administration of 50 micrograms phenyl biguanid. Hering-Breuer inflation reflex was induced by lung inflation with pressure of 1 kPa. Reactivity of tracheal and pulmonary smooth muscle to histamine were measured in vitro. Differences in recorded parameters between animals exposed to PNO, and to room air, were tested by Mann-Whitney-Wilcoxon test and by Student's t-test. When p < 0.05, the differences were recognized as significant.
Results:
Significant decreasing of the expiratory parameters of the cough induced from laryngopharyngeal mucosa, inhibition of sneezing, and inhibition of aspiration reflex, were found in animals exposed to PNO. Relaxing reaction of tracheal smooth muscle of control animals to histamine was reversed to contraction in animals exposed to PNO. Morphological changes of the respiratory tract induced by influence of oxygen were found
Conclusion:
Long-lasting breathing of PNO induced changes of respiratory reactions elicited mainly from upper airway.(Fig. 6, Tab. 3, Ref. 22)