Exam 3 Study Guide NR224

Chapter 40 Oxygenation Oxygen -Cardiac and respiratory systems supply the oxygen demands of the body -Blood oxygenated through mechanisms (ventilation, perfusion, and transport of resp. gases) Respiratory Physiology ...

Chapter 40 Oxygenation Oxygen -Cardiac and respiratory systems supply the oxygen demands of the body -Blood oxygenated through mechanisms (ventilation, perfusion, and transport of resp. gases) Respiratory Physiology -Exchange of respiratory gases occur between environment and blood -Respiration is exchange of oxygen and carbon dioxide during cellular metabolism -Airways in lungs transfer oxygen from atmosphere to alveoli-oxy. Is exchanged for carbon dioxide. Structure and Function -Intrapleural pressure is negative/less than atmospheric pressure (760 mmHg) at seal level -Air flow into lungs, intrapleural pressure becomes more negative-sets pressure gradient between atmosphere and alveoli -Diaphragm and external intercostal muscles contract to create negative pleural pressure, increase size of thorax for inspiration 3 Steps of Oxygenation (Ventilation, Perfusion, Diffusion) Ventilation: process of moving gases into and out of the lungs. -coordination of lung and thorax -major inspiratory muscle of respiration is diaphragm -innervated by phrenic nerve, exits the spinal cord at 4th cervical vertebra Perfusion: ability of the cardiovascular system to pump oxygenated blood to tissues and return deoxygenated blood to lungs Diffusion: responsible for moving respiratory gases from one area to another by concentration gradients -exchange of respiratory gases need organ, nerves, muscles to be intact. Central nervous system needs to regulate the respiratory cycle Work of Breathing -the effort required to expand and contract the lungs Inspiration: an active process, stimulated by chemical receptors in aorta Expiration: passive process, depends on the elastic recoil properties of lungs -requires little or no muscle work Surfactant: chemical produced in the lungs to maintain the surface tension of the alveoli and keep them from collapsing -Patients with COPD lose the elastic recoil of the lungs and thorax, WOB increases Atelectasis: collapse of the alveoli that prevents normal exchange of oxygen and carbon dioxide Compliance-the ability of the lungs to distend or expand in response to increased intraalveolar pressure -decreases in diseases such as pulmonary edema, interstitial and pleural fibrosis, and congenital or traumatic structural abnormalities such as kyphosis or fractured ribsAirway resistance-increase in pressure occurs as diameter of airways decreases from mouth/nose to alveoli -Disease causing airway obstruction such as asthma and tracheal edema increase airway resistance -Airway resistance increases, amount of oxygen delivered to alveoli decreases Lung Volumes -Normal lung values are determine by age, gender, and height Tidal Volume: amount of air exhaled after normal inspiration Residual Volume: amount of air left in the alveoli after a full expiration Forced vital capacity: maximum amount of air that can be removed from the lungs during forced expiration Respiration Gas Exchange -Thickness of membrane affects rate of diffusion -Increased thickness of membrane impedes diffusion, gases take longer to transfer across membrane -Pulmonary Edema, Pulmonary Infiltrates, Pulmonary Effusion have thickened membrane, results in slow diffusion, slow exchange of respiratory gases, decreased delivery of oxygen to tissues Oxygen Transport -Consists of lungs and cardiovascular system -Delivery depends on amount of oxygen entering lungs (ventilation), blood flow to lungs and tissues (perfusion), rate of diffusion, and oxygen-carrying capacity Three things influence the capacity of the blood to carry oxygen: amount of dissolved oxygen in plasma, amount of hemoglobin, tendency of hemoglobin to bind with oxygen Hemoglobin: carrier for oxygen and carbon dioxide -transports most oxygen 97% -hemoglobin molecule combines with oxygen to form oxyhemoglobin -oxyhemoglobin is reversible, which frees oxygen to enter tissues Carbon Dioxide Transport -product of cellular metabolism, diffuse into red blood cells and is rapidly hydrated into carbonic acid (H2CO3) -Dissociates into hydrogen and bicarbonate ions HCO-3 -Hemoglobin buffers hydrogen ion and HCO-3 diffuses into plasma -Venous blood transports majority of carbon dioxide back to the lungs to be exhaled Cardiovascular Physiology -Cardiopulmonary physiology involves delivery of deoxygenated blood (high in carbon/low in oxy.) to the right side of heart and then to lungs where it is oxygenated -Oxygenated blood (high in oxygen/low in carbon) travels from lungs to the left side of heart and the tissues Structure and Function -Right ventricle pumps deoxygenated blood through the pulmonary circulation -Left ventricle pumps oxygenated blood through the systemic circulationMyocardial Pump -Pumping action of heart is essential to oxygen delivery -Four cardiac chambers, two atria, two ventricles -Ventricles fill during diastole, empty during systole -Stroke volume: volume of blood ejected from the ventricles during systole *Hemorrhage and dehydration cause a decrease in circulating blood volume and a decrease in stroke volume* -Myocardial fibers-have contractile properties, allow them to stretch during filling Frank-Starling Law of Hearts -Myocardium stretches, the strength of the subsequent contraction increases Pulmonary-left heart failure Systemic- right heart failure Myocardial Blood Flow -Must supply sufficient oxygen and nutrients to the myocardium itself -Valvular Disease: backflow or regurgitation of blood through the incompetent valve, causing a murmur that you can hear on auscultation Coronary Artery Circulation -Branch of systemic circulation, supplies the myocardium with oxygen and nutrients and removes waste Systemic Circulation -Deliver nutrients and oxygen to tissues and veins remove waste from tissues -Oxygenated blood flows from the left ventricle through the aorta and into large systemic arteries -Exchange of respiratory gases occurs at capillary level, tissues are oxygenated -Waste exit capillary network through venules, join to form veins -Veins become larger, form vena cava, carry deoxygenated blood to right side of heart, returns to pulmonary circulation Blood Flow Regulation Cardiac Output: amount of blood ejected from the left ventricle each minute -Normal cardiac output is 4-6 L/min -Cardiac output increases during exercise, pregnancy, and fever -Decreases during sleep -FORMULA: Stroke Volume (SV) X Heart Rate (HR) Preload: blood left in left ventricle at the end of diastole (preload) -More stretch on ventricular muscle, greater the contraction, greater the stroke volume Afterload: Resistance to left ventricular ejection -Heart works harder to overcome resistance, blood can be fully ejected from left ventricle -Diastolic aortic pressure is a good clinical measure of afterload -Hypertension-afterload increases making cardiac workload also increase Myocardial Contractility -affects stroke volume and cardiac output -poor ventricular contraction decreases amount of blood ejected -injury to myocardial muscle, acute MI causes decrease in myocardial contractility