Chest
The Importance of Spirometry in COPD and Asthma: Effect on Approach to Management
Section snippets
Diagnosis of COPD
A diagnosis of COPD is suggested by history and physical examination and is confirmed by spirometry (ie, reduced FEV1).1 The residual volume and total lung capacity are increased in most cases. A chest radiograph may suggest emphysema, and the diagnosis can be confirmed with a CT scan, which is especially useful in the selection of patients for lung volume reduction surgery.4 Gas exchange is usually impaired and is frequently reflected by systemic hypoxemia with and without hypercapnia.5
Pathophysiology of COPD
The basic pathophysiologic process in COPD consists of increased resistance to airflow, loss of elastic recoil, decreased expiratory flow rate, and overinflation of the lung.678910 The alveolar walls frequently rupture (emphysema) in the process. The hyperinflated lungs flatten the curvature of the diaphragm and enlarge the rib cage. The altered configuration of the chest cavity places the respiratory muscles, including the diaphragm, at a mechanical disadvantage and impairs their
Natural History of COPD
Little is known about the natural history of COPD since the initiation of the modern era of treatment. Knowledge about the natural course of severe COPD is based on old studies and is linked entirely to changes in lung function.161718 We know that the FEV1 in nonsmokers without respiratory disease declines by 25 to 30 mL per year beginning approximately between the ages of 25 and 30 years. The rate of decline of FEV1 is steeper for smokers than for nonsmokers (Fig 1). It is also steeper for
Role and Value of Spirometry in COPD
As we have seen, postbronchodilator spirometry is required to confirm the diagnosis of COPD.1 Once diagnosed, there are no widely accepted staging or severity scoring systems for patients with COPD. At present, we grade the disease based on a single objective physiologic measure such as FEV1.
Paradoxically, we define COPD by a low FEV1 value that fails to respond to bronchodilators, a characteristic that differentiates it from asthma, and then we use the change in FEV1 to evaluate the effect of
Spirometry in Asthma
Asthma is a chronic inflammatory disease of the airways. In the United States, it afflicts approximately 14 million people. It is the most common disease of childhood and causes close to 500,000 hospitalizations a year. It is estimated that 5,000 people die from asthma every year. Many more develop acute respiratory failure and require mechanical ventilation. The death rates from asthma have remained stable for the past decade.
Inasmuch as asthma is a chronic inflammatory disorder, many cells
Conclusion
Spirometry remains essential for the diagnosis and monitoring of both asthma and COPD (Table 2). The use of spirometry in patients at risk for the development of both diseases or with respiratory symptoms could help detect cases at an early stage when intervention may prevent further deterioration. Because of the reversible component of asthma, the use of peak flowmeters to determine airflow on a continued basis is practical and seems to have resulted in improved outcomes. In contrast, in
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