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3448. Pulse oximetry. Uses and abuses.
Pulse oximetry has made a significant contribution to noninvasive monitoring in a wide variety of clinical situations. It allows for continuous reliable measurements of oxygen saturation while avoiding the discomfort and risks of arterial puncture. As the extent of hypoxic episodes during various procedures and clinical settings is better appreciated, the role of continuous noninvasive monitoring will undoubtedly expand. An understanding of the principles and technology of pulse oximetry will allow physicians to obtain maximal clinical benefit from its use.
3456. Myocardial oxygen supply and demand.
The supply of oxygen to the myocardium is determined by coronary blood flow and oxygen carrying capacity. Coronary blood flow is a dynamic process modulated via multiple parameters. Cardiac metabolism is also affected by several factors. Under normal physiologic conditions, the demand is easily met by the supply of oxygen. In fact, there is a significant reserve on the supply side. Under certain pathologic states such as coronary artery disease, the supply of oxygen may be exhausted and an imbalance between supply and demand occurs which is translated into ischemia. The area of myocardium most susceptible to ischemia is the subendocardium due to mechanical and metabolic forces. In therapy of coronary artery disease, attention should be directed to directional changes in factors influencing supply and demand to improve blood flow to the most susceptible area.
3457. Esophagoatrial fistula with previous pericarditis complicating esophageal ulceration. Report of two cases and a review of the literature.
Sixteen cases of nontraumatic left atrial-esophageal fistulas have been reported previously. These fistulas usually result from chronic peptic esophagitis or cancer. The diagnosis is suggested by the triad of chronic dysphagia, hematemesis, and acute neurologic signs. There may be cardiac manifestations such as pericarditis, atrial fibrillation, or shock. An unusual feature of these fistulas is systemic embolization of food, air, or septic necrotic debris which may result in sudden central nervous system symptoms. All reported cases resulted in death due to hemorrhage, although there was often a variable time interval between the onset of hematemesis and the patient's death. The authors report two additional cases in which an episode of pericarditis preceded fistula development. Based on these 18 cases, the spectrum of esophagoatrial fistulas is reviewed, as well as the signs which may herald fistula development.
3459. Current use of imaging in the evaluation of primary mediastinal masses.
A wide variety of lesions occur in the mediastinum in patients of every age. Twenty five to 50 percent of these primary mediastinal masses may be malignant, making early diagnosis and therapy crucial. Since most arise from normal structures in the region, localization of lesions to compartments of the mediastinum may assist in diagnosis. This article reviews imaging techniques for lesions originating in the mediastinum.
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