pulmonary circulation

pulmonary

[pul´mo-ner″e] 1. pertaining to the lungs" >lungs; called also pulmonic and pneumonic.2. pertaining to the pulmonary artery.pulmonary acid aspiration syndrome a disorder produced as a complication of inhalation of gastric contents; it may progress to a syndrome resembling acute respiratory distress syndrome.pulmonary alveolar proteinosis a disease of unknown etiology marked by chronic filling of the alveoli with a proteinaceous, lipid-rich, granular material consisting of surfactant and the debris of necrotic cells. Some patients have a history of exposure to irritating dusts or fumes. The condition is treated by whole lung lavage with balanced salt solution; most patients need repeated lavage.pulmonary artery the large artery originating from the superior surface of the right ventricle of the heart and carrying deoxygenated blood to the lungs for oxygenation; it starts as the pulmonary trunk, which divides between the fifth and sixth thoracic vertebrae to form the right pulmonary artery that enters the right lung and the left pulmonary artery that enters the left lung. See Appendix 3-1.pulmonary circulation the circulation of blood to and from the lungs. Unoxygenated blood from the right ventricle flows through the right and left pulmonary arteries to the right and left lungs. After entering the lungs, the branches subdivide, finally emerging as capillaries which surround the alveoli and release the carbon dioxide in exchange for a fresh supply of oxygen. The capillaries unite gradually and assume the characteristics of veins. These veins join to form the pulmonary veins, which return the oxygenated blood to the left atrium. See also circulatory system.pulmonary function tests tests used to evaluate lung mechanics, gas exchange, pulmonary blood flow, and blood gases and pH. They are used to evaluate patients in the diagnosis of pulmonary disease, assessment of disease development, or evaluation of the risk of pulmonary complications from surgery.Lung Volumes and Capacities. The total lung capacity (TLC) is divided into four volumes. The tidal volume (V_T) is the volume inhaled or exhaled in normal quiet breathing. The inspiratory reserve volume (IRV) is the maximum volume that can be inhaled following a normal quiet inhalation. The expiratory reserve volume (ERV) is the maximum volume that can be exhaled following a normal quiet exhalation. The residual volume (RV) is the volume remaining in the lungs following a maximal exhalation. The vital capacity (VC) is the maximum volume that can be exhaled following a maximal inhalation; VC = IRV + V_T + ERV. The inspiratory capacity (IC) is the maximum volume that can be inhaled following a normal quiet exhalation; IC = IRV + V_T. The functional residual capacity (FRC) is the volume remaining in the lungs following a normal quiet exhalation; FRC = ERV + RV.
The vital capacity and its components are measured using a spirometer, which measures the volumes of air inhaled and exhaled. The functional residual capacity is usually measured by the helium dilution method using a closed spirometry system. A known amount of helium is introduced into the system at the end of a normal quiet exhalation. When the helium equilibrates throughout the volume of the system, which is equal to the FRC plus the volume of the spirometer and tubing, the FRC is determined from the helium concentration. This test may underestimate the FRC of patients with emphysema. The FRC can be determined quickly and more accurately by body plethysmography. The residual volume and total lung capacity are determined from the functional reserve capacity.Forced Vital Capacity (FVC). In the forced vital capacity maneuver, the patient exhales as forcefully and rapidly as possible, beginning at maximal exhalation. Several parameters are determined from the spirogram. The forced vital capacity is the total volume of air exhaled during the maneuver; it is normally equal to the vital capacity. The forced expiratory volume (FEV) is the volume expired during a specified time period from the beginning of the test. The times used are 0.5, 1, 2, and 3 seconds; corresponding parameters are FEV_0.5, FEV_1.0, FEV_2.0, and FEV_3.0. The maximal expiratory flow is the slope of the line connecting the points where 200 ml and 1200 ml have been exhaled; it is also called FEF_200–1200 (forced expiratory flow). The maximal midexpiratory flow is the slope of the line connecting the points where 25 per cent and 75 per cent of the forced vital capacity have been exhaled; it is also called FEF_25–75%.Maximal Voluntary Ventilation (MVV). This is the maximal volume of air that can be breathed by the patient, expressed in liters per minute; it was formerly called maximal breathing capacity. The patient breathes as rapidly and deeply as possible for 12 to 15 seconds and the volume exhaled is determined by spirometry.Predicted Values. Because the results of pulmonary function tests vary with size and age, the normal values are calculated using prediction equations or nomograms, which give the normal value for a specific age, height, and sex. The prediction equations are derived using linear regression on the data from a population of normal subjects. The observed values are usually reported as a percentage of the predicted value.Interpretation. These tests provide evidence of impairment of ventilatory function; they do not point to specific disease processes. Abnormal test results may show either an obstructive or a restrictive pattern; sometimes both are present.The Obstructive Pattern. This pattern occurs when there is airway obstruction from any cause, as in asthma, bronchitis, emphysema, or advanced bronchiectasis; these conditions are grouped together in the nonspecific term chronic obstructive pulmonary disease. In this pattern, the residual volume is increased and the PV/TLC ratio is markedly increased. Owing to increased airway resistance, the flow rates are decreased. The FEV/FVC ratios, maximal midexpiratory flow, and maximal expiratory flow are all decreased; FEV_1.0/FVC is less than 75 per cent.The Restrictive Pattern. This pattern occurs when there is a loss of lung tissue or when lung expansion is limited as a result of decreased compliance of the lung or thorax or of muscular weakness. This pattern occurs in conditions such as pectus excavatum, myasthenia gravis, diffuse idiopathic interstitial fibrosis, and space-occupying lesions (tumors, effusions). The vital capacity and forced vital capacity are less than 80 per cent of the predicted value, but the FEV/FVC ratios are normal. The total lung capacity is decreased and the RV/TLC ratio is normal.pulmonary vein any of the four large veins (two right and two left branches) that carry oxygenated blood from the lungs to the left atrium of the heart. See anatomic Table of Veins in the Appendices.

pul·mo·nar·y cir·cu·la·tion

the passage of blood from the right ventricle through the pulmonary artery to the lungs and back through the pulmonary veins to the left atrium. Synonym(s): lesser circulation