Lung
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The normal structure and function of the pleura are discussed here in addition to how physiological abnormalities and various pathological processes can upset the finely balanced situation between the visceral and parietal pleural surfaces, leading to effusion formation, and/or adhesions. The various inflammatory and reactive processes that affect the pleura, together with primary and secondary tumor formations are described. Particular emphasis is placed on those conditions of the pleura that are associated with asbestos exposure because this group of diseases will increase over the next few decades due to the large number of workers who have been exposed to asbestos. They will therefore be of increasing importance to the clinician, radiologist, and pathologist in future years.
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Noninvasive positive pressure ventilation (NPPV) has reemerged as an effective strategy for reducing morbidity and mortality associated with acute exacerbations of chronic obstructive pulmonary disease (COPD). During acute respiratory failure, dynamic hyperinflation, intrinsic PEEP, and increased airway resistance result in a mechanical workload that exceeds inspiratory muscle capacity. NPPV provides augmentation of alveolar ventilation and respiratory muscle rest. ⋯ NPPV performs better in COPD patients without significant comorbid illness. It should be initiated during COPD exacerbations if arterial pH is less than 7.35 or if the patient is severely distressed. Pressure support ventilation (10-20 cmH2O) via face mask is likely the optimal technique and, when successful, results in rapid clinical improvement.
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Review Comparative Study
Pulse oximetry versus arterial blood gas specimens in long-term oxygen therapy.
Portable pulse oximeters are now widely available for the assessment of arterial oxygenation, and the U. S. Medicare program considers saturation readings to be acceptable substitutes for arterial PO2 in selecting patients for long-term oxygen therapy (LTOT). ⋯ Pulse oximetry cannot detect hypercapnia or acidosis. For these and other reasons, pulse oximetry should not be used in initial selection of patients for LTOT, as a substitute for arterial blood gas analysis in the evaluation of patients with undiagnosed respiratory disease, during formal cardiopulmonary exercise testing, or in the presence of an acute exacerbation. Pulse oximetry is an important addition to the clinician's armamentarium, however, for titrating the oxygen dose in stable patients, in assessing patients for desaturation during exercise, for sleep studies, and for in-home monitoring.
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Dyspnea--an unpleasant or uncomfortable awareness of breathing or need to breathe--is a common symptom of patients with cardiopulmonary disease. Although often thought of as a single symptom, dyspnea probably subsumes many sensations. Experimental conditions used to induce dyspnea are characterized by discrete groups or clusters of descriptive phrases. ⋯ Evidence is gathering that the sensations of dyspnea are modified by information from a variety of receptors throughout the respiratory system. The sense of effort, although still important in the breathlessness associated with mechanical loads, is insufficient to explain the dyspnea arising from a number of experimental and clinical conditions. As our understanding of the interactions between effort and afferent information from the respiratory system grows, new therapeutic interventions to alleviate dyspnea are likely to follow.
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Diaphragmatic weakness implies a decrease in the strength of the diaphragm. Diaphragmatic paralysis is an extreme form of diaphragmatic weakness. Diaphragmatic paralysis is an uncommon clinical problem while diaphragmatic weakness, although uncommon, is probably frequently unrecognized because appropriate tests to detect its presence are not performed. ⋯ In this review we outline an approach we have found useful in attempting to determine a specific cause. Most frequently the cause is either a phrenic neuropathy or diaphragmatic myopathy. Often the neuropathy or myopathy affects other nerves or muscles that can be more easily investigated to determine the specific pathologic basis, and, by association, it is presumed that the diaphragmatic weakness or paralysis is secondary to the same disease process.