Resp Care
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Lung function parameters vary considerably with age and body size, so that, unlike many laboratory tests, the normal range of expected values must be individualized. For spirometry, only low values are considered to be abnormal, so the lower limit of normal (LLN) is taken to be equal to the 5th percentile of a healthy, non-smoking population. Simple and commonly used "rules of thumb," such as an FEV(1)/FVC < 0.70 to indicate air-flow obstruction, or assuming values < 80% of predicted to be abnormal, are inaccurate and will cause misclassification, specifically under-diagnosis of abnormalities in younger, taller individuals and over-diagnosis in those older or shorter. ⋯ A future goal for the pulmonary community would be the development of risk stratified outcome data that would allow an estimation of the probability of disease with progressive decrements in lung function. While interpreting spirometry results near the LLN will continue to be problematic, a more important task for the pulmonary community is to focus on finding the pool of individuals with clear-cut, but undiagnosed, COPD. And for this, good quality spirometry remains the best tool and must be widely available.
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Over the years a great deal of effort has been made to standardize all pulmonary function tests on adults. Many of the "rules" concerning the interpretation of the spirogram have been based entirely on adult observations. In the age of increasing conformity, and attempts to relate "adult" literature to the pediatric population, the latter was given much less emphasis than the former. ⋯ Lung function testing, particularly spirometry, has much to offer in the diagnosis of lung disease in children and the monitoring of response to therapy. With better standardization of pulmonary function testing in children, and more trained technologists, the age limits for testing can be extended to below 6 years of age and sometimes below 5. Also with better standardization the results obtained are meaningful and when interpreted in context of age offer excellent diagnostic information to better treat the child with lung disease.
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With the introduction of the stair climb test of surgical patients in the 1950s, the role of exercise-based testing as a useful diagnostic tool and an adjunct to conventional cardiopulmonary testing was established. Since then, we have witnessed a rapid development of numerous tests, varying in their protocols and clinical applications. The relatively simple "field tests" (shuttle walks, stair climb, 6-minute walk test) require minimal equipment and technical support, and so are generally available to physicians and patients. ⋯ Is it sufficiently robust and informative to replace the more demanding and less available CPET? In many instances, the clinical applications are overlapping, with the 6MWT functioning as an adequate surrogate. However, in the initial evaluation of unexplained dyspnea, in formal evaluation of impairment and disability, in detailed evaluation of congestive heart failure, and in the selected lung cancer patient prior to resection, CPET remains superior. Investigations of portable metabolic and cardiovascular monitoring devices aiming to enhance the diagnostic capabilities of 6MWT may further narrow or close the remaining gap between these two exercise studies.
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Spirometry is considered the primary method to detect the air flow limitation associated with obstructive lung disease. However, air flow limitation is the end-result of many factors that contribute to obstructive lung disease. One of these factors is increased airway resistance. ⋯ Furthermore, the FOT provides unique information about lung mechanics that is not available from analysis using spirometry, body plethysmography, or the interrupter technique. However, it is unclear whether any of these measures of airway resistance contribute clinically important information to the traditional measures derived from spirometry (FEV(1), FVC, and FEV(1)/FVC). The purpose of this paper is to review the physiology and methodology of these measures of airway resistance, and then focus on their clinical utility in relation to each other and to spirometry.
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Review Case Reports
What is the best pulmonary diagnostic approach for wheezing patients with normal spirometry?
Asthma is characterized by airway inflammation, airway hyper-responsiveness (AHR) and variable air flow obstruction. The diagnosis of asthma, however, is often based upon nonspecific clinical symptoms of cough, wheeze, and shortness of breath. Furthermore, the physical examination and measurements of pulmonary function are often unremarkable in patients with asthma, thereby complicating the diagnosis of the disease. The following discussion will review approaches to the diagnosis of asthma when lung functions are normal, and will largely focus on the use of bronchial provocation tests to detect underlying AHR.