Biomaterial Database

Phasic negative intrathoracic pressures enhance the vascular responses to stimulation of pulmonary arterial baroreceptors in closed-chest anaesthetized dogs. 2004

Jonathan P Moore, and Roger Hainsworth, and Mark J Drinkhill

Institute for Cardiovascular Research, School of Medicine, University of Leeds, Leeds LS2 9JT, UK.

We investigated whether the reflex responses to stimulation of pulmonary arterial baroreceptors were altered by intrathoracic pressure changes similar to those encountered during normal breathing. Dogs were anaesthetized with alpha-chloralose, a cardiopulmonary bypass was established, and the pulmonary trunk and its main branches as far as the first lobar arteries were vascularly isolated and perfused with venous blood. The chest was closed following connection to the perfusion circuit and pressures distending the aortic arch, carotid sinus and coronary artery baroreceptors were controlled. Changes in the descending aortic (systemic) perfusion pressure (SPP; flow constant) were used to assess changes in systemic vascular resistance. Values of SPP were plotted against mean pulmonary arterial pressure (PAP) and sigmoid functions applied. From these curves we derived the threshold pressures (corresponding to 5% of the overall response of SPP), the maximum slopes (equivalent to peak gain) and the corresponding PAP (equivalent to 'set point'). Stimulus-response curves were compared between data obtained with intrathoracic pressure at atmospheric and with a phasic intrathoracic pressure ranging from atmospheric to around -10 mmHg (18 cycles min(-1)). Results were obtained from seven dogs and are given as means +/-S.E.M. Compared to the values obtained when intrathoracic pressure was at atmospheric, the phasic intrathoracic pressure decreased the pulmonary arterial threshold pressure in five dogs; average change from 28.4 +/- 5.9 to 19.3 +/- 5.9 mmHg (P > 0.05). The inflexion pressure was significantly reduced from 37.8 +/- 4.8 to 27.4 +/- 4.0 mmHg (P < 0.03), but the slopes of the curves were not consistently changed. These results have shown that a phasic intrathoracic pressure, which simulates respiratory oscillations, displaces the stimulus-response curve of the pulmonary arterial baroreceptors to lower pressures so that it lies within a physiological range of pressures.

UI	MeSH Term	Description	Entries
D010477	Perfusion	Treatment process involving the injection of fluid into an organ or tissue.	Perfusions
D011311	Pressoreceptors	Receptors in the vascular system, particularly the aorta and carotid sinus, which are sensitive to stretch of the vessel walls.	Baroreceptors,Receptors, Stretch, Arterial,Receptors, Stretch, Vascular,Stretch Receptors, Arterial,Stretch Receptors, Vascular,Arterial Stretch Receptor,Arterial Stretch Receptors,Baroreceptor,Pressoreceptor,Receptor, Arterial Stretch,Receptor, Vascular Stretch,Receptors, Arterial Stretch,Receptors, Vascular Stretch,Stretch Receptor, Arterial,Stretch Receptor, Vascular,Vascular Stretch Receptor,Vascular Stretch Receptors
D011312	Pressure	A type of stress exerted uniformly in all directions. Its measure is the force exerted per unit area. (McGraw-Hill Dictionary of Scientific and Technical Terms, 6th ed)	Pressures
D011651	Pulmonary Artery	The short wide vessel arising from the conus arteriosus of the right ventricle and conveying unaerated blood to the lungs.	Arteries, Pulmonary,Artery, Pulmonary,Pulmonary Arteries
D004056	Differential Threshold	The smallest difference which can be discriminated between two stimuli or one which is barely above the threshold.	Difference Limen,Just-Noticeable Difference,Weber-Fechner Law,Difference Limens,Difference, Just-Noticeable,Differences, Just-Noticeable,Differential Thresholds,Just Noticeable Difference,Just-Noticeable Differences,Law, Weber-Fechner,Limen, Difference,Limens, Difference,Threshold, Differential,Thresholds, Differential,Weber Fechner Law
D004285	Dogs	The domestic dog, Canis familiaris, comprising about 400 breeds, of the carnivore family CANIDAE. They are worldwide in distribution and live in association with people. (Walker's Mammals of the World, 5th ed, p1065)	Canis familiaris,Dog
D005260	Female		Females
D000818	Animals	Unicellular or multicellular, heterotrophic organisms, that have sensation and the power of voluntary movement. Under the older five kingdom paradigm, Animalia was one of the kingdoms. Under the modern three domain model, Animalia represents one of the many groups in the domain EUKARYOTA.	Animal,Metazoa,Animalia
D001013	Aorta, Thoracic	The portion of the descending aorta proceeding from the arch of the aorta and extending to the DIAPHRAGM, eventually connecting to the ABDOMINAL AORTA.	Aorta, Ascending,Aorta, Descending,Aortic Arch,Aortic Root,Arch of the Aorta,Descending Aorta,Sinotubular Junction,Ascending Aorta,Thoracic Aorta,Aortic Roots,Arch, Aortic,Ascending Aortas,Junction, Sinotubular,Root, Aortic,Sinotubular Junctions
D013909	Thorax	The upper part of the trunk between the NECK and the ABDOMEN. It contains the chief organs of the circulatory and respiratory systems. (From Stedman, 25th ed)	Chest,Thoraces,Chests,Thorace