miner's lung: see pneumoconiosis.

lung cancer, cancer that originates in the tissues of the lungs. Lung cancer is the leading cause of cancer death in the United States in both men and women. Like other cancers, lung cancer occurs after repeated insults to the genetic material of the cell. By far the most common source of these insults is tobacco smoke, which is responsible for about 85% of U.S. lung cancer deaths (see smoking). The incidence of lung cancer in other countries follows their smoking patterns. Some other carcinogens known to cause lung cancer are found in the workplace. These include bischloromethyl ether and chloromethyl ether in chemical workers, arsenic in copper smelting, and asbestos in shipbuilders and other asbestos workers. Radon poses a risk to uranium and fluorspar miners and may pose a risk in some private residences as well. African Americans have a higher incidence of lung cancer than European Americans, even after adjusting for smoking.

Types of Lung Cancer

Lung cancers are classified according to the type of cell present in the tumor. The majority are referred to as non-small cell carcinomas. These include squamous cell or epidermoid carcinomas (the most common type worldwide), adenocarcinomas, and large cell carcinomas. Small cell carcinoma (which includes the subtypes oat cell and intermediate) comprises approximately 20% to 25% of lung cancers; it often has metastasized by the time it is detected. Lung cancer most commonly spreads to the brain, bone, liver, or bone marrow.

Symptoms

The primary symptoms of lung cancer are cough, shortness of breath, hoarseness, blood in the sputum, and pain. In some types, the cancer cells themselves produce hormones or other substances that can create an imbalance and result in various symptoms. Metastatic lung cancer also can cause symptoms that result from its effect on the organ to which the cancer has spread.

Diagnosis and Treatment

Diagnosis of lung cancer may be made by physical examination, chest X rays, bronchoscopy (see bronchoscope), or percutaneous needle biopsy (insertion of a fine needle through the skin and into the lung to obtain tissue for study). In many cases definitive diagnosis is made after surgical specimens have been evaluated. Evaluation of suspected sites of metastasis may involve CAT scans or magnetic resonance imaging (MRI). A special CAT-scanning technique (helical low-dose CAT-scanning) has also been used for initial diagnosis because it can detect small tumors before they have spread.

Lung cancer is staged according to its location, size, cell type, and spread. This staging plus the state of health of the patient are used to determine treatment.

Treatment typically consists of surgical excision of the tumor alone or in combination with either external-beam radiation therapy or chemotherapy using one or more anticancer drugs. Photodynamic therapy is sometimes used if the cancer is still localized. In this therapy a substance that makes cells more sensitive to light is injected into the body. When it has passed out of most of the tissues, but remains in the cancer cells, the cancer is destroyed by a beam of laser light.

Prevention

Not starting to smoke or ceasing to smoke is by far the most effective lung cancer preventive. The risk of lung cancer in ex-smokers begins to decline about five years after quitting, and after 15 to 20 years their risk is 80% less than that of smokers. The reduction in cigarette smoking since the 1964 report of the Surgeon General's Advisory Committee on Health began to be translated into a decrease in the incidence of lung cancer in the 1990s; this decrease averaged more than 1% per year from 1990 to 1995. The preventive role of dietary antioxidants is under study.

iron lung, device used to maintain artificial respiration over an extended period of time. Before the successful vaccination program against poliomyelitis, it was used mostly in treatment of that disease. Currently, its main usage is in cases where the respiration control center of the brain has been damaged (e.g. skull fractures, brain tumors and stroke) or where the diaphragm is paralyzed by spinal cord disease or injury. Invented (1928) by Philip Drinker, the iron lung is composed of a cylindrical steel drum, which encloses the entire body with only the head exposed. A rubber diaphragm makes the cylinder airtight without putting undue pressure on the neck. Pumps raise and lower the pressure within the chamber. A number of problems exist with the iron lung machine; food or vomit may be aspirated into the lungs, and serious skin ulcers may develop in a patient who is immobilized for long periods of time.

heart-lung machine, device that maintains the circulation of the blood and the oxygen content of the body when connected with the arteriovenous system; it is also called the pump oxygenator. The machine is used in open-heart surgery when it is necessary to effect a bypass of the circulatory system of the heart and lungs. The oxygenator repeatedly draws off the blood from the veins, reoxygenates it, and pumps it into the arterial system. The contractions of the heart are halted by running a potassium citrate solution through the coronary vessels. The surgeon is thus enabled to open the heart and make the necessary repairs while the heart is still and his view is not obstructed by blood.

book lung, terrestrial respiratory organ characteristic of arachnids such as scorpions and primitive spiders. Each book lung consists of hollow flat plates. Air bathes the outer surface of the plates and blood circulates within them, facilitating the exchange of gases. In most species, adequate gas exchange occurs without any muscular movement to ventilate the lung.

black lung: see pneumoconiosis.

Ya-lung, river, China: see Yalong.

Ch'ien-lung, 1711-99, reign title of the fourth emperor (1735-96) of the Ch'ing dynasty, whose given name was Hung-li. Under his vigorous military policy, China attained its maximum territorial expanse; Xinjiang in the west was conquered, and Myanmar and Annam in the south were forced to recognize Chinese suzerainty. He restricted Western merchants to Guangzhou (Canton) in 1759, and he rejected British overtures for expanded trade and diplomatic ties in 1793. Ch'ien-lung was a patron of scholarship and the arts; some of China's finest porcelain and cloisonné were produced for his collections, and vast anthologies were edited, partly to censor seditious references to the Manchus. Despite the surface splendor of cultural achievement and imperial expansion, his reign in later years was characterized by growing official corruption, loss of military efficiency, and fiscal imbalance.

Lung disease caused by long-term inhalation of asbestos fibres. A pneumoconiosis found primarily in asbestos workers, asbestosis is also seen in people living near asbestos industries. Fibres remain in the lungs and many years later cause extensive scarring and fibrosis. Shortness of breath and inadequate oxygenation result; advanced cases include a dry cough. There is no effective treatment. The associated increased cardiac effort may induce heart disease. Cigarette smoking greatly exacerbates its symptoms. Lung cancer and malignant mesothelioma are more common with asbestos inhalation and asbestosis.

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Distention of blood vessels in the lungs and filling of the pulmonary alveoli with blood. It results from infection, hypertension, or inadequate heart function (e.g., left-sided heart failure). Congestion seriously impairs gas exchange, leading to breathing difficulty, bloody discharge in sputum, and bluish skin tint.

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Malignant tumour of the lung. Four major types (squamous-cell carcinoma, adenocarcinoma, large-cell carcinoma, and small-cell carcinoma) have roughly equal prevalence. Most cases are due to long-term cigarette smoking. Heavy smoking and starting smoking earlier in life increase the risk. Passive inhalation (“secondhand smoke”) is linked to lung cancer in nonsmokers. Other risk factors include exposure to radon or asbestos. Symptoms, including coughing (sometimes with blood), chest pain, and shortness of breath, seldom appear until lung cancer is advanced, when treatment with surgery, chemotherapy, and radiation or some combination of the three is less effective. Most patients die within a year of diagnosis.

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Either of two light, spongy, elastic organs in the chest, used for breathing. Each is enclosed in a membrane (pleura). Contraction of the diaphragm and the muscles between the ribs draw air into the lungs through the trachea, which splits into two primary bronchi, one per lung. Each bronchus branches into secondary bronchi (one per lobe of lung), tertiary bronchi (one per segment of lung), and many bronchioles leading to the pulmonary alveoli. There oxygen in the inspired gas is exchanged for carbon dioxide from the blood in the surrounding capillaries. Adequate tissue oxygen supply depends on sufficient distribution of air (ventilation) and blood (perfusion) in the lungs. Lung injuries or diseases (e.g., emphysema, embolism, pneumonia) can affect either or both.

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or brown lung disease

Respiratory disorder caused by an endotoxin produced by bacteria found in the fibres of cotton. The disorder is common among textile workers. In addition, the endotoxin stimulates histamine release; air passages constrict, making breathing difficult. Over time the endotoxin accumulates in the lung, producing a typical brown discoloration. First recognized in the 17th century, byssinosis today is seen in most cotton-producing regions of the world. Several years of exposure to cotton fibres are needed before byssinosis develops. In advanced stages, it causes chronic, irreversible obstructive lung disease. Though endotoxin in cotton is by far the most common cause, endotoxins found in flax, hemp, and other organic fibres can also produce byssinosis.

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or Ch'ien-lung emperor orig. Hongli

(born Sept. 25, 1711, China—died Feb. 7, 1799, Beijing) Fourth emperor of the Qing dynasty in China. His reign (1735–96) was one of the longest in Chinese history. China's boundaries reached their greatest extent, encompassing Mongolia, Tibet, Nepal, Taiwan, and portions of Central Asia. Qianlong sponsored a compilation of the Confucian Classics (see Five Classics); the compilation's descriptive catalog is still used today. At the same time, he ordered that all books containing anti-Manchu sentiments be expurgated or destroyed; some 2,600 h1s were lost. He enjoyed excellent personal relationships with Jesuit missionaries in Beijing, though Roman Catholic preaching remained officially forbidden. In the first half of his reign, agriculture made great strides and was superior to that in much of Europe. Taxes were light and education was widespread, even among the peasantry. Subsequently, military expeditions and increasing governmental corruption permanently harmed the dynasty, sowing the seeds for its decline in the 19th century. Seealso Heshen; Kangxi emperor; Manchu.

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