Search PubMed⌕ Search

Biomedical subjects

A Davies

Publications and source records attributed to A Davies.

At least 289 records · Page 16Linked to original sources
PubMed1981

Aspiration in seriously ill patients: a study of amylase in bronchial secretions.

Bronchial secretions from 21 patients with moderate to severe chest infections were obtained by transtracheal aspiration. Six seriously ill patients showed greatly increased levels of amylase activity in the bronchial secretions compared with those found in the 15 less ill patients. This amylase was almost certainly derived from oropharyngeal contents and its presence suggests that aspiration may be more common in comatose and semi-comatose patients than is generally appreciated.

Amylases↗
PubMed1980

Control of postural changes of end expiratory volume (FRC) by airways slowly adapting mechanoreceptors.

We recorded the e.m.g. activity of the diaphragm and of an abdominal muscle (ext. oblique) and the respiratory volume in anesthetized rabbits challenged with head-up tilting and positive pressure breathing (PPB). Both maneuvers determined an inhibition of inspiratory activity and an activation of abdominal muscles, the latter being especially marked with tilting. After cervical vagotomy neither the inspiratory inhibition nor the abdominal recruitment was present during tilting and PPB and the FRC increase was more pronounced. Sulphur dioxide was given in the inspired air (200 ppm) to selectively block the slowly adapting mechanoreceptors. Such blockade was indicated by the absence of the Hering-Breuer inflation reflex. The permanence of other respiratory reflexes was shown by a parodoxical response to inflation and by a still evident response to deflation. With SO2 block, both tilting and PPB did not elicit either the inspiratory inhibition or the abdominal muscles activation, leading to an FRC shift similar to that observed after vagotomy. We conclude that the slowly adapting mechanoreceptors subserve a reflex mechanism relevant in controlling FRC.

Abdominal Muscles↗
PubMed1979

Unusual response of anaesthetised pigs to asphyxia.

The effects of vagosympathectomy, asphyxia, hypoxia and hypercapnia on the breathing of anaesthetised pigs are described. Vagosympathectomy caused changes in cardiovascular variables and in the pattern of breathing characteristic of the loss of stretch receptor activity. After vagosympathectomy the linear relationship between tI and tE was abolished. Hypoxia in intact animals produced changes in minute ventilation by peripheral chemoreceptor drive. When this drive was removed by vagosympathectomy the central depressing effects of hypoxia were revealed as a slowing of breathing and reduction in minute volume. The central depressing effect of hypoxia on respiration was very potent in the pig and very clearly seen in asphyxia. Vagosympathectomy caused a reduction in frequency of breathing and respiratory arrest occurred when a dead space of only moderate size was used. Breathing slowed from the moment of connection of the dead space to produce respiratory arrest within 2 min. The pig lung has been considered similar to the human lung on morphometric and physiological grounds but these results show that there are very important species differences in response to asphyxia.

Animals↗
PubMed1978

Lung reflexes in rabbits during pulmonary stretch receptor block by sulphur dioxide.

Anaesthetized rabbits were given 200 ppm sulphur dioxide to breathe for 10 min. This abolished activity in 23 of 26 pulmonary stretch receptors, while leaving that of lung irritant receptors unimpaired. The Breuer-Hering reflex was abolished and breathing became deeper and slower. Inspiratory time (tI) was increased and expiratory time (tE) decreased. Subsequent vagotomy increased tidal volume (VT), tI and tE. In animals with stretch receptors blocked, injections of phenyl diguanide and histamine still increased breathing frequency and decreased VT, indicating that reflexes from lung irritant and J-receptors were intact. Inhalation of 8% CO2 caused a bigger increase in frequency and tidal volume in rabbits with stretch receptor block compared with controls or those after vagotomy. Induction of pneumothorax with stretch receptor block transiently prolonged tI and shortened tE; removal of the pneumothorax also transiently shortened tE and usually also decreased tI. The results suggest that lung irritant receptors reflexly shorten tE in all our experimental conditions, but have various effects on tI which may depend on the timing of the irritant receptor discharge and refractoriness of the inspiratory response.

Animals↗