Acta Physiol Hung
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Pleural pressure, airflow and tidal volume during experimental cough and sneeze elicited by mechanical stimulation of the tracheobronchial and nasal mucous membranes were investigated in fifty anaesthetized cats (pentobarbital, 40 mg/kg i.p.). Pressure-volume, pressure-flow and flow-volume relations were studied during these expulsive processes. In comparison to quiet breathing there was a decrease in dynamic lung compliance in both respiratory tract reflexes (p less than 0.001), especially in their expiratory phases. ⋯ The total lung resistance increased markedly (p less than 0.001) in both cough and sneeze compared to quiet breathing. In these expulsive processes there was also a high "cough index" (resistance calculated from the peak flow and instantaneous pressure). The flow-volume curve in cough, in contradistinction to sneeze, indicated a significantly reduced airflow of the end of expiration (at 85% of the expired volume), demonstrating a concomitant bronchoconstriction.
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The influence of sulphur dioxide (SO2) on cough and expiratory reflexes was studied in 22 anaesthetized (pentobarbital, 30 mg/kg i.v.) rabbits. The cough reflex (CR) was elicited by tracheobronchial mucous membrane stimulation, using a soft venous catheter. In order to induce the expiratory reflex (ER) irritation of the larynx was performed by a silon fibre loop. ⋯ It was found that elicitability and strength of the cough reflex decreased immediately after SO2 breathing had been stopped, and did not reach the preexposure level at the end of the experiment, i.e. 2 hours after discontinuation of SO2 breathing. The direct dependence of LIPM on ERS in unaffected rabbits [10] was abolished immediately after SO2 breathing had been stopped but was present again 30-60 minutes later, and did not differ significantly from the control values. The results give evidence of the strong depressive influence of SO2 on the defensive reflexes of the airways in rabbits.
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In order to estimate optimum parameters for artificial ventilation of adult guinea pigs, the effect of four hours intermittent positive pressure ventilation (IPPV) was studied using different tidal volumes (VT), respiratory frequencies (f), and minute volumes (Ve). Total compliance was measured by placing the animal in a whole body plathysmograph, the arterial blood gases, pH and base excess by catheterizing the carotid artery. In Series I 9 guinea pigs were ventilated at parameters adapted to the spontaneous breathing pattern (VT = 2 ml, f = 70 breaths.min-1). ⋯ The results demonstrated a favourable effect of slow and deep ventilation upon lung mechanics and oxygenation. In Series III 3 different Ve (300, 250, 200 ml.min-1) were tested using a constant VT = 10 ml. Optimum parameters for artificial ventilation of adult guinea pigs were: VT = 10 ml and f = 20 breath--min-1 which resulted in stable compliance, good O2-saturation, normocapnia and normal acid-base balance.
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Dogs were made tolerant to lethal doses of adrenaline by treatment with increasing doses of the hormone up to 1 mg/kg. The conscious animals were then subjected to haemorrhagic shock with a hypovolaemic period of 3 hours. ⋯ Catecholamine induced myocardial lesions were found in the treated group. No evidence of a blunting of the sympathetic response or a protective effect in haemorrhagic shock was seen in adrenaline tolerance.