Cross-sectional physiology of the lung

Article Abstract:

The lungs are exposed to disease-causing elements primarily from inhaled air and from circulating blood. Both of these pathways expose the lungs fairly uniformly to such elements. However, many diseases tend to localize in specific areas of the lungs. Gravity plays a role in differences between the upper and lower portions of the lungs, but other factors influence the variation of disease localization found between the peripheral regions and the central region of the lungs. Anatomical and physiological differences are important factors in explaining why some diseases localize in the periphery of the lungs, and others in the central regions. The anatomy of the lungs is comparable to that of the kidneys' corticomedullary structure, consisting of a cortex (outer portion) and a medulla (inner portion). The medulla of the lungs is much more complex in structure than the cortex. Like the kidneys, there are major differences between the networks of blood vessels, bronchi, and lymph vessels found in the inner and outer portions of the lungs. Perfusion of blood flow to the inner and outer areas of the lungs is a difference thought to greatly influence disease localization. The amount and rate of blood flow through a region affects the amount of exposure that region will have to bloodborne toxins. Ventilation differences are also important factors in determining whether the inner or outer portions of the lungs will be affected by a disease-causing element. These differences result in variations in amounts and types of particles deposited in the layers. Differences in lymph flow between the layers are also found. Lymph flow is important for the removal of particles that cause disease from the tissues, and different rates of removal affect exposure times and amounts. Stress differences between the inner and outer layers are thought to also play a role in disease distribution and are comparable to stress differences found between the upper and lower portions of the lungs caused by gravity. This also affects where disease-causing particles will localize. As is found in the kidney, it appears that differences in disease distribution between the inner and outer portions of the lungs are a result of gradient differences resulting from anatomical and physiological variations of these areas. (Consumer Summary produced by Reliance Medical Information, Inc.)

Physiological aspects, Lungs, Lung, Anatomy

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When is it malpractice to miss lung cancer on chest radiographs?

Article Abstract:

The failure of a radiologist to diagnose lung cancer from X-rays has become one of the leading reasons patients initiate malpractice suits. Radiologists must judge whether any abnormalities seen on an X-ray should be evaluated further, usually by biopsy. It would be unreasonable, not to mention impossible, for all abnormalities found to be examined by this method. The radiologist must use his or her expertise in deciding which cases need further evaluation. Obviously, any time a cancer is not diagnosed when present, the error can have major consequences. By the time the cancer is diagnosed, it may be too late to save the patient's life. There is also the chance of misdiagnosing cancer when it does not exist; however, this type of error is preferable to the opposite type of error. This is particularly true for the radiologist. His diagnosis will not be accepted as fact until further diagnostic evaluation is made. This does not mean that a radiologist should automatically diagnose any abnormality as cancer and pass the patient on for confirmation. The costs would be prohibitive and it would have a negative effect on the position of radiology in the medical field. The radiologist must then be aware of what sources of error lead to malpractice suits and when these errors constitute negligence. Errors can occur in taking an X-ray of poor quality, not noticing a detectable abnormality, or not judging the abnormality to be serious. Up to 90 percent of all lung cancers can be detected on earlier X-rays when diagnosed later on. Present law does not allow such a finding to automatically indicate malpractice. In order for negligence to be found, it must be shown that the radiologist failed to attain the standard of care required, and that this failure was directly responsible for the failed diagnosis. Whether a radiologist wishes to avoid malpractice or plans to provide expert testimony in such cases, the standards of the profession, the sources of error, and the reasonableness of such error must be considered. (Consumer Summary produced by Reliance Medical Information, Inc.)

Medical personnel, Malpractice, Medical malpractice, Lung cancer, Radiologists

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Gleaning physiologic information from the conventional chest radiograph

Article Abstract:

Chest X-rays are frequently used in the diagnosis of cardiopulmonary disease (of the heart and lungs). They have generally been used to detect anatomic abnormalities, and have infrequently been used to detect physiologic or blood flow abnormalities. Milne and his fellow researchers have shown that chest X-rays are useful for distinguishing cardiogenic and noncardiogenic pulmonary edema (or accumulation of fluid in the lungs due to heart-related and nonheart-related causes). In the April 1991 issue of Radiology, Woodring examines the use of chest X-rays to measure ratios between the pulmonary artery (which brings blood to the lungs for oxygenation) and bronchus (one of the two branches of the trachea). This measurement is then used to assess pulmonary vascular congestion (the accumulation of blood in the pulmonary vessels) and congestive heart failure (ineffective heart function, which can result in pulmonary congestion). The study measures the pulmonary artery-bronchus ratios in normal subjects, patients with pulmonary vascular congestion, and patients with congestive heart failure in both supine (lying) and erect positions. The findings support results that would be predicted from physiologic principles. Healthy patients would be expected to have higher ratios in the upper lung when in the upright position because of the effects of gravity, and equal ratios in the lying position. Patients with congestive heart failure would be expected to have increased ratios in the upper lung regardless of position. These predictions were supported by Woodring's results. There are some problems with the study; the sample size for each group was small, and the positive and negative predictive values are probably overly optimistic. However, the results of using chest X-rays to obtain physiologic data are encouraging. (Consumer Summary produced by Reliance Medical Information, Inc.)

Measurement, Congestive heart failure, X-rays, Chest, Thorax

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