Pulmonary blood vessels

The lungs receive blood through both the bronchial and pulmonary arteries. The former carries blood at systemic pressure and has thicker, more muscular walls than the pulmonary arteries which carry blood under one-sixth as much pressure. 

Pulmonary artery pressure and size may be affected by the hypoxia that occurs with increasing altitude. According to Gio et al. (1988), however, the radiologically measured pulmonary artery size at median altitudes (Salt Lake City 1400 m) is the same as that seen at sea level. 

For mapping the microvascular pattern of normal and diseased tissue, Nettum (1995) described a combined vascular-bronchoalveolar casting method using formalin-fixed canine lungs and a low viscosity silicone rubber. 

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Two different circulatory systems, the bronchial and the pulmonary, supply the lungs with blood [133], The bronchial circulation is a part of the systemic circulation and is under high pressure. It receives about 1% of the cardiac output and supplies the conducting airways, pulmonary blood vessels and lymph nodes [133], It is important for the distribution of systemically administered drugs to the airways and to the absorption of inhaled drugs from the airways [18]. The pulmonary circulation comprises an extensive low-pressure vascular bed, which receives the entire cardiac output. It perfuses the alveolar capillaries to secure efficient gas exchange and supplies nutrients to the alveolar walls. Anastomoses between bronchial and pulmonary arterial circulations have been found in the walls of medium-sized bronchi and bronchioles [18, 65, 67],... 

Pharmacology The methyixanthines (theophylline, its soluble salts and derivatives) directly relax the smooth muscle of the bronchi and pulmonary blood vessels, stimulate the CNS, induce diuresis, increase gastric acid secretion, reduce lower esophageal sphincter pressure, and inhibit uterine contractions. Theophylline is also a central respiratory stimulant. Aminophylline has a potent effect on diaphragmatic contractility in healthy people and may then be capable of reducing fatigability and thereby improve contractility in patients with chronic obstructive airways disease. Pharmacokinetics ... 

Mechanism of Action A xanthine derivative that acts as a bronchodilator by directly relaxing smooth muscle of the bronchial airways and pulmonary blood vessels. Therapeutic Effect Relieves bronchospasm and increases vital capacity. Pharmacokinetics Rapidly and well absorbed. Protein binding Moderate (to albumin). Extensively metabolized in liver. Partially excreted in urine. Half-life 6-12 hr (varies). 

Preliminary studies in animals suggest that airway smooth muscle, like that in the vasculature, is effectively relaxed by nitric oxide. This very lipophilic drug can be inhaled as a gas in acute asthma and dilates the pulmonary blood vessels as well as the airway smooth muscle. Although nitric oxide itself—or nitric oxide donors—may prove of value in acute severe asthma, it appears likely that they will be more useful in pulmonary hypertension (for which nitric oxide is already approved). 

Q7 What happens to the area of lung whose circulation has been cut off by an embolus in a pulmonary blood vessel ... 

Another stable derivative of PGIj, iloprosi, is intended for nasal inhalation to provide a direei vasodilaiory effect on pulmonary blood vessels and thus decrease vascular resistance. Currently available in Europe, patients inhale 6 to 8 puffs of aerosolized iluprost every 2 to 3 hours. Side effects such as coughing, headaches, and jaw pain have been reported. 

Tumors of pulmonary blood vessels Microvascular effect on ocular fundus and retina direct injury to endothelial cells atheroma formation... 

In animals, HCl is a severe irritant of the eyes and respiratory system. The 30 min LC50 values in rats and mice are 4701 and 2644 ppm, respectively. Animals exposed to high concentrations of HCl gas developed necrosis of the tracheal and bronchial epithelium, pulmonary edema, atelectasis, emphysema, and damage to the pulmonary blood vessels and liver. Chronic exposure to 10 ppm for 6hday for life did not cause neoplastic lesions or serious irritant effects in the nasal epithelium of rats. In experimental animals, exposure to a concentration of 1350 ppm hydrogen chloride gas caused clouding of the cornea after 1.5 h and exposure to 3000 ppm for 6 h caused slight erosion of the corneal epithelium. 

Directly relaxes smooth muscle of bronchial airway, pulmonary blood vessels, relieving bronchospasm, increasing vital capacity. Produces cardiac and skeletal muscle stimulation. 

The primary indication for theophylline is as a controller medication for the treatment of bronchospasm of asthma and COPD. In addition to bronchodilation effects, theophylline dilates pulmonary blood vessels, acts centrally to stimulate respiration, acts as a diuretic, increases gastric acid secretion, and inhibits uterine contractions. Dosing requires the determination of plasma levels with 10 to 20 pg/mL being associated with the least incidence of side effects. Overdose of theophylline can result in a quick onset of ventricular arrhythmias, convulsions, or even death... 

There is no true pulmonary analogue to the systemic arterioles, since the pulmonary circulation occurs under relatively low pressure [West, 1977]. Pulmonary blood vessels, especially capiQaries and venules, are very thin walled and flexible. Unlike systemic capillaries, pulmonary capillaries increase in diameter, and pulmonary capillaries within alveolar walls separate adjacent alveoli with increases in blood pressure or decreases in alveolar pressure. Flow, therefore, is significantly influenced by elastic deformation. Although pulmonary circulation is largely unaffected by neural and chemical control, it does respond promptly to hypoxia. 

R. 1. Jeppsson and G, L. Schoefl, Electron microscopic obsers aiions on cerebral and pulmonary blood vessels after the i.v. injection of urtificial lipid emulsions containing barbituric acids. Au.st. J. Exp. Biol. Med Sci., 52 703-709. 1974. 

The actions of prostaglandins on isolated pulmonary blood vessels were reviewed by Piper and Vane (1979). Usually, E-type PG relax pulmonary vascular smooth muscle but there is some species variation in the reaction of intrapulmonary blood vessels (Palmer et al. 1973, Kadowitz et al. 1975). The intrapulmonary vessels will be exposed to the prostaglandins released in the lung by agents such as bradykinin, slow-reacting substance of anaphylaxis or histamine. 

In 1977, Craddock etal.( 26) reported that transient leukopenia occurred within 1 h of starting dialysis. They concluded that this was due to activation of the alternative complement pathway by the dialyzer and subsequent sequestration of polymorphonuclear cells by the pulmonary blood vessels caused by the chemotactic action of the activated complement. However, Haeffiier-Cavaillon et al. (27) reported that complement promotes the production of interleukin 1 by... 

Parenchymal bands consist of linear densities 2-5 cm in length, usually contacting the pleural surface and distinguishable from pulmonary blood vessels in that they are thicker, do not taper peripherally, and are often oriented in a direction incompatible with normal vessels (Fig. 8.21) (Aberle et al. 1988). 

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