Pulmonary Circulation
Peter Kam, Ian Power, Michael J. Cousins, Philip J. Siddal in Principles of Physiology for the Anaesthetist, 2020
Unlike the high-pressure and high-resistance systemic circulation, which controls and changes perfusion to individual organs, the pulmonary circulation operates at much lower pressures, with very distensible and low-resistance vessels receiving and distributing the venous return over the large area of thin alveolar walls available for gas exchange. The primary function of the pulmonary circulation is to bring systemic venous (mixed venous) blood into contact with the alveoli for gas exchange. Additionally, it has three secondary functions: as blood filter, as blood reservoir and as a metabolic organ. Pressures in the pulmonary circulation are only 20% of systemic pressures, because the resistance of the former is much lower. Pulmonary vascular resistance is equally divided between arteries, capillaries and veins, unlike the systemic circulation, where the greatest part of the resistance is in the arterioles. The resistance of the pulmonary capillaries is influenced by alveolar volume and pressure.
Respiratory System
David Sturgeon in Introduction to Anatomy and Physiology for Healthcare Students, 2018
This chapter shows that oxygen from the atmosphere diffuses from a high concentration in the alveoli to a lower concentration in pulmonary circulation. The respiratory system consists of the airways, the lungs, the muscles of respiration and the areas of the nervous system which control the rate and depth of ventilation. The airways are divided into the upper and lower respiratory tract at the larynx. Air enters the larynx through the epiglottis which protects the glottis and lower respiratory tract when swallowing occurs. The upper respiratory tract consists of the nasal cavity, the mouth and the pharynx. Air is inhaled through the nose and is filtered, warmed and humidified as it passes through the nasal conchae and makes its way to posterior chamber of the nasal cavity and the upper part of the pharynx – the nasopharynx. The pharynx, oral cavity and nasal cavity also act as resonating chamber that helps to provide the distinctive sound quality of the voice.
Cardiovascular system
Andrew M. Luks, Philip N. Ainslie, Justin S. Lawley, Robert C. Roach, Tatum S. Simonson in Ward, Milledge and West's High Altitude Medicine and Physiology, 2021
This chapter discusses cardiovascular responses to high altitude hypoxia and how these responses impact global cardiovascular performance, reviews limitations and important gaps in knowledge, and emphasizes future directions to further our understanding of the cardiovascular system at high altitude. The core function of the cardiovascular system is to deliver oxygenated blood to the tissues. For that reason, any discussion of changes in cardiac function at high altitude must begin with consideration of changes in cardiac output. Experiments early in the last century showed a general pattern of a rise in cardiac output with acute exposure to high altitude, followed by a fall to at or near sea-level values with acclimatization. Given the role of heart-lung interactions in cardiac function and systemic hemodynamics, any discussion of cardiac function at high altitude must also consider changes that occur in the pulmonary circulation.
Ventricular assist devices for the failing univentricular circulation
Published in Expert Review of Medical Devices, 2017
Edward Buratto, William Y. Shi, Xin Tao Ye, Igor E. Konstantinov
ABSTRACT Introduction: Improved survival following single ventricle palliation has led to a large population of patients with a univentricular circulation, many of whom develop heart failure. Increasing experience with ventricular assist devices (VAD) in children has paved the way for VAD support in those with failing univentricular circulation. Areas covered: The use of VADs to support the failing univentricular circulation is a relatively new concept. Most studies have focused on supporting patients with the failing systemic ventricle. There are limited reports of VAD support of the pulmonary circulation in patients with Fontan failure despite preserved ventricular function. None of the current VADs have been designed to support the pulmonary circulation. Novel low-pressure, high-flow pumps, specifically designed to support the pulmonary circulation, are under development. Expert commentary: The failing univentricular circulation is one of the great challenges in the field of congenital heart disease. While current VADs are designed to support the systemic circulation, many patients require support of the pulmonary circulation. A fully implantable VAD for support of the pulmonary circulation as destination therapy would be beneficial for patients with preserved systolic function, but must have low energy requirements, negligible risk of stroke and low risk of device thrombosis and failure.
Anthropometric Evaluation and Functional Assessment of Patients with Pulmonary Hypertension and its Relationship with Pulmonary Circulation Parameters and Functional Performance
Published in Journal of the American College of Nutrition, 2018
Priscila B. Zanella, Camila C. Àvila, Carolina G. de Souza
ABSTRACT Objective: The objective of this study was to investigate the anthropometric and functional status in patients with pulmonary hypertension (PH) and its relationship with pulmonary circulation parameters and functional performance. Methods: The study is cross-sectional with 34 subjects, who were evaluated in terms of anthropometric measurements, physical performance, pulmonary circulation, and regular physical activity. Results: Subjects had a mean age of 47.0 ± 14.5 years, mean IMC 28.5 ± 7.7 kg/m2 among adults, and 27.65 ± 2.68 kg/m2 among elderly, with high body fat and preserved muscle mass. The sample presented the parameters of pulmonary circulation expected for PH patients and adequate performance in the physical capacity test. By linear regression analysis there was observed a negative relationship between body fat and regular physical activity. Conclusion: The evaluated subjects had an excess of body weight and fat, with preserved muscle mass, which does not appear to interfere in the pulmonary circulation parameters. However, elevated body fat appears to impair regular their physical activity.
Hemodynamic Changes of Adenosine Diphosphate, Adenosine Triphosphate, and Thrombin in Relation to Their Platelet-Aggregating Activity
Published in Scandinavian Journal of Clinical and Laboratory Investigation, 1971
J. Swedenborg, G. Taylor, P. Olsson
ADP and ATP were infused into the systemic and pulmonary circulation of dogs. Thrombin was infused into the pulmonary circulation. All the agents caused a decreased platelet count. ADP and ATP caused an increase in cardiac output. Pulmonary vascular resistance as well as total peripheral vascular resistance were decreased. Thrombin caused an increase in pulmonary vascular resistance and a decrease in total peripheral vascular resistance.