Postgraduate Medicine

ISSN: 0032-5481 (Print) 1941-9260 (Online) Journal homepage: http://www.tandfonline.com/loi/ipgm20

Definition, differentiation, and classification of COPD Joseph F. Tomashefski MD To cite this article: Joseph F. Tomashefski MD (1977) Definition, differentiation, and classification of COPD, Postgraduate Medicine, 62:1, 88-97, DOI: 10.1080/00325481.1977.11712248 To link to this article: http://dx.doi.org/10.1080/00325481.1977.11712248

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Date: 29 November 2016, At: 17:43



sympOSium

definition, differentiation, and classification of COPD Joseph F. Tomashefski, MD

Cleveland Clinic Cleveland

consider What is the relationship of pipe and cigar smoking to COPD? Of air pollution? How should the patient at risk for COPD be evaluated clinically? What radiologie findings suggest asthma? Chronic bronchitis? Pulmonary emphysema?

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• The terms "chronic obstructive pulmonary disease" (COPD), "chronic obstructive airway disease" (COAD), and "chronic obstructive lung disease" (COLD) are applied to a group of conditions in which the common physiologie abnormality is obstruction to airflow on expiration. Most prevalent within this wide spectrum of diseases are chronic bronchitis, chronic asthma, and pulmonary emphysema. 1 •2 Others, which will not be considered here, are cystic fibrosis, bronchiectasis, and obstruction associated with fibrosing diseases. Obstruction to airflow is very common. Surveys indicate that 3% of the population have abnormal pulmonary function. The incidence is about 30% in men and women over 35 years of age, and even higher in smokers. Consequent! y, COPD is a major cause of pulmonary distress and disability. The various conditions can occur atone or in combination. They involve the major, intermediate, and small airways as weil as the Jung parenchyma. Early detection of COPD is important. Diagnosis and differentiation of the entities that make up its spectrum present a challenge. The umbrella term ''COPD'' is very convenient, but for prognostic and therapeutic reasons it is essential that the specifie disease or diseases be differentiated clearly and that measures to slow progression be instituted. Definitions

Chronic asthma- This disease is characterized by intermittent attacks of reversible airway obstruction, both inspiratory and expiratory, which may follow a course of days, months, or years. The two basic types of chronic asthma are arbitrarily referred to as intrinsic and extrinsic. Intrinsic asthma is nonatopic and develops mostly in adults; allergy tests are negative. Respiratory infection recurs, frequently in association with bronchitis (often called asthmatic bronchitis). Extrinsic asthma is atopic and may date from infancy or early childhood. A history of multiple allergies is usual. Differentiating between intrinsic and extrinsic asthma is often difficult. Chronic bronchitis-This disease involves major as weil as small airways and is characterized by inflammation, edema, mucous gland hypertrophy with crypt formation, cough, and hypersecretion. It can occur atone, sometimes as a severe disabling disease, or with asthma, emphysema, or both.

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Pulmonary emphysema-This disease of the Jung parenchyma is morphologically characterized by destruction of air spaces, with fenestrations and with Joss of Jung elasticity distal to the terminal bronchioles. Emphysema can be localized or diffuse, with or without apparent obstruction. It can be focal, perifocal (associated with scar formation), centrilobular, or panlobular (panacinar). Dyspnea on exertion is a classic symptom. Associated bronchitis is common. Obstruction to airflow resuhs from the loss of radial traction support of the small airways.

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Etiology

Numerous factors, both internai and environmental, can contribute to the development of each type of COPD 1-3 (table 1). Asthma may have single or multiple precipitating causes. Atopic patients may have positive skin tests, urticaria, hay fever, or eczema, or may show none of these allergie phenomena. A detailed history will often disclose aggravating agents. Skin tests are oflimited value in adults with chronic asthma. In children and in young

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definition of

COPD~-------------------------·

table 1. factors in development of COPD Asthma

Chronic bronchltls

Emphysema

Allergy Hypersensitivity Infection Environment

Cigarette smoking Atmospheric contaminants (eg, dusts, vapors, fumes, gases) Infection

Cigarette smoking Atmospheric contaminants (eg, dusts, vapors, fumes, gases) Antienzyme and enzyme deficiencies (eg, alpha1-antitrypsin) Advanced stages of pulmonary fibrosis Destruction of lung parenchyma (necrosis, ischemia, inflammation)

Drugs Emotions Social conditions

Chronic irritation Gastroesophageal dysfunction

Exercise

adults with intennittent episodes of disease, however, they may determine that perennial antigens (such as bouse dust, animal dander, molds, feathers, and mites) are involved. Although hyposensitization (immunotherapy) may be effective in children, results in adults have been very disappointing. Occasionally patients with reversible airway obstruction are allergie to aspirin or other drugs. The syndrome of asthma, nasal polyps, and aspirin sensitivity is now weil recognized. Aggravating factors in chronie asthma are infections; drug misuse; and emotional, social, and environmental conditions (smoke, gases, vapors, fumes, dusts, cold air, exercise, coughing, laughing). In chronic bronchitis and pulmonary emphysema, cigarette smoking is the most common causative factor, playing botha direct and an indirect role in pathogenesis. The risk in pipe and cigar smokers is less than that in cigarette smokers but greater than that in nonsmokers. Recent evidence indieates that smoking is associated with obstruction in the small, or peripheral, airways (~ 2 mm diameter), producing an entity referred to as small airway disease. Obstruction of the small airways is also present in chronic bronchitis, asthma, and pulmonary emphysema. It has been postulated that small airway disease represents an

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early and still reversible stage of COPD. 4 •5 Atmospherie pollution and occupational exposure to dusts are much less important etiologie factors than is cigarette smoking. Exposure to sorne dusts (eg, coal, asbestos, cotton) is associated with an increased incidence of COPD, especially in the person who is also a cigarette smoker or a hyperreactor. Air pollutants in high concentration (sulfur dioxide, nitrogen dioxide, ozone, chlorine gas) are capable of producing acute or chronic lung damage. Air pollution within acceptable standards has not been demonstrated to produce COPD. However, high air pollution levels aggravate symptoms in patients with established disease. The inhalation of toxic fumes in high concentrations can also produce pulmonary edema and bronchiolitis obliterans. Alpha 1 -antitrypsin deficiency has been shown6 to be associated with an increased tendency for the development of emphysema early in life. Uninhibited proteases of leukocytie origin are implicated in destroying lung parenchyma. Alpha 1 -antitrypsin measurements are indieated, therefore, in patients in whom symptoms develop at an early age, those with a strong family history of COPD, and those with emphysema predominantly in the lower lobe. There is evidence6 that inhaled irritants hasten the development of COPD in susceptible persans. Since alpha 1 -antitrypsin defieiency is transmitted as an autosomal recessive, investigation of other members of the patient's family is necessary; where deficiency is present, appropriate counseling should be provided. 7 A host of enzyme-antienzyme substances are currently being explored as possible etiologie factors in pulmonary emphysema. Gastroesophageal reflux and chronic aspiration with recurrent irritation and infection are occasional causes of COPD. Infections of the respiratory tract-whether viral, bacterial, or mycotie-may precipitate or aggravate the symptoms of COPD. Inhalation of sorne industrial fumes, gases, dusts, vapors,

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or chemicals may act directly or synergistically to produce COPD. Slgns and Symptoms

Because of the similarity of signs and symptoms among the various entities included in the spectrum of COPD, clinical differentiation frequently is difficult. The predominant symptoms are cough, expectoration, wheezing, shortness ofbreath, and those associated with recurrent respiratory infections. The predominance of certain symptoms and characteristics in a parti cul ar disease may allow clinical differentiation. The presence of a barrel chest suggests emphysema. This could be misleading, however, because barrel chest can occur with aging, as an osteoarthritic change, or with kyphosis, without any evidence of emphysema. Hyperresonance on percussion of the chest is associated with hyperinflation. One of the best indicators ofthe presence of obstructive airway disease is a prolonged expiratory phase. Normal forced expiration is completed in four to six seconds, whereas in patients with COPD, especially emphysema, completion takes more than six seconds. Rhonchi occur on both inspiration and expiration in asthma; they are predominantly expiratory in chronic bronchitis and emphysema. Rhonchi may not be discernible on chest examination during quiet breathing but become evident during forced breathing with the airways collapsed. They may clear or change after coughing, especially when secretions are present. One of the hallmarks of pulmonary emphysema is decreased breath sounds. Clubbing of the digits and cyanosis are rare or late manifestations of COPD; they occur more frequently and earlier in fibrosing interstitial pneumonitis. Radiologie Manifestations

The radiologie manifestations ofCOPD are multiple, varied, and often nonspecific. 7 The patient with COPD may have a normal chest

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Joseph F. Tomashefski Dr Tomashefski is head, department of pulmonary disease, and medical director of the pulmonary function laboratory, Cleveland Clinic, Cleveland.

film with marked clinical signs, symptoms, and physiologie abnormalities. On the other band, an occasional patient may have minimal clinical or physiologie manifestations but x-ray abnormalities indicating severe disease. The correlation between the posteroanterior chest film and the clinical and physiologiç manifestations of COPD is not good except in advanced stages of disease. In emphysema the identification and correlation improve if a posteroanterior view during deep inspiration and during forced complete expiration and a lateral view are obtained (figures 1 and 2). The primary radiologie feature for the diagnosis of COPD is pulmonary hyperinflation. Excursion of the hemidiaphragms is limited in ali forms of COPD. Chronic asthma-In asthma, the chest film may be normal. However, it is helpful in excluding presence of other pulmonary disease, pneumonie infiltrates, and atelectasis. During prolonged bronchospasm, overinflation occurs, as shown by a low position of the hemidiaphragms and an increased retrosternal air space. On fluoroscopy there is poordiaphragmatic excursion, impaired aeration, and evidence of air trapping. The pulmonary markings, heart, and mediastinal structures appear to be normal. Occasionally during a severe asthmatic episode, mediastinal emphysema may occur. A bronchogram of an asthmatic patient shows spasticity, changes in the cali ber of the bronchi, secretions, tapering, and obliteration of the small radicles. Chronic bronchitis-In chronic bronchitis, the posteroanterior chest film is also usually normal. Overinflation may be present, reflecting air trapping, associated emphysema, or both. Bronchial thickening, characterized by

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definition of COPD - - - - - - - - - - - - - - - - - - -

Figure 1. Position and extent of bilateral hemidiaphragmatic excursion in normal lung during inspiration (a) and expiration (b) and on lateral view (c).

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tubular shadows outside the hilar area, is one of the findings most diagnostic of chronic bronchitis. These shadows have been termed tram !ines and are best seen on laminagrams. Mucous gland filling on bronchography correlates weil with the presence of chronic bronchitis. The cryptic hypertrophied glandular collections of contrast medium are best seen along the inferior margin of the large airways and have been termed bronchial diverticula (figure 3). Their presence is pathognomonic of chronic bronchitis and is very helpful in differentiating chronic bronchitis from bronchiectasis, suppurative bronchitis, and other obstructive airway disease. Another finding highly suggestive of chronic bronchitis is the truncated termination of the bronc hi five to eight generations along the axial pathway. This may be the result of obliterative bronchi or of mucous secretions obstructing bronchi. Cine fluoroscopy often demonstrates collapse of the major airways with coughing or forced expiration. This feature, however, is nonspecific and may occur in other airway disease, such as asthma, bronchiectasis, or emphysema. Pulmonary emphysema-In pulmonary emphysema, the major roentgenographic

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finding is lung hyperinflation. Blebs and bullae are usually due to localized processes and seldom are indicative of diffuse disease. In diffuse emphysema of the panacinar or centrilobular types, the anteroposterior diameter of the chest is increased and there is forward bowing of the sternum, with a resultant increase in the retrosternal air space. 8 The hemidiaphragms are located in a low position and flattened. In sorne cases, inversion of the diaphragmatic contour occurs. Flattening is noted especially on the lateral view. In severe emphysema, the cardiac silhouette is narrow and elongated. Irregular areas of radiolucency are seen throughout. Many of the aforementioned findings may occur in the absence of emphysema. It is therefore crucial that the radiologie findings be confrrmed by at least two major clinical and physiologie findings before diagnosis of emphysema is entertained. Emphysema is often associated with decreased pulmonary vasculature peripherally and with large central arteries (so-called arterial deficiency pattern of emphysema). 7 In emphysema associated with alpha 1 antitrypsin deficiency, overdistention and other fine changes occur predominantly in the lower lung fields. Areas of lung hyperinfla-

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Figure 2. Position and extent of bilateral hemidiaphragmatic excursion in emphysematous Jung during inspiration (a) and expiration (b) and on lateral view (c). Note low flat position of hemidiaphragm, poor excursion, irregular radiolucencies, hyperinflation, increased retrosternal air space, and other radiologie signs of emphysema.

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definition of COPD tion with bullae are seen where retraction, tearing, and fibrosis occur, producing perifocal emphysematous changes. The bronchographie medium fails to fil! blebs and bullae in pulmonary emphysema. On occasion, however, areas of centrilobular emphysema may be filled with radiopaque material, giving a "lily ofthe valley" pattern (figure 4). Laminagraphy, cine fluoroscopy, and bronchography may be of value in sorne cases but are not advocated as standard procedures. Physiologie Findings

Figure 3. Bronchogram showing irregularity in caliber of airways, secretions, cryptic hypertrophy, and filling (bronchial diverticula) indicative of chronic bronchitis.

Figure 4. Bronchogram of emphysematous lung. Airways show evidence of bronchitis with peripheral filling consistent with centrilobular emphysema.

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The various entities of COPD have cornmon physiologie features as weil as certain distinguishing aspects. Asthma, for example, is characterized by edema, bronchospasm, and secretions. Consequent! y, inspiratory and expiratory airflow obstruction are both present but are highly reversible, in contrast to the obstruction seen with chronic bronchitis and emphysema. Chronic asthma-In asthma, in addition to airway obstruction, the mixing and distribution of air is poor and the lungs are overdistended, with an increase in total Jung capacity. Since Jung parenchyma is not destroyed, diffusing capacity is normal or sometimes even elevated owing to the increased surface area for gas diffusion. Most patients with chronic asthma can cope with airflow obstruction if airflow is maintained at 50% to 75% of the predicted normal range. Once airflow gets below this leve!, increased work of breathing and dyspnea are apparent. Chronic bronchitis-In chronic bronchitis, obstruction is only mildly reversible. The major as weil as the smaller airways are invoived. Residual volume and total Jung capacity are usually normal or mildly increased. Intrapulmonary gas mixing is good, but the reis marked mismatching of blood and air, giving rise to physiologie shunting characterized by hypoxemia and early hypercapnia. Diffusing capacity is normal or only mildly reduced. In many patients with chronic bronchitis, pulmonary function may

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definition of COPD table 2. differentiation of COPD entities by findings on physiologie tests Test or measurement

Asthme

Bronchltls

Emphysema

Spirometry

Slight improvernent wlth bronchodilators

No improvement with bronchodilators

Lung compartments (FRC, RV, TLC)*

Considerable improvement with bronchodilators (reversible bronchospasm) lncreased owing to hyperinflation of lungs

Usually normal or mildly increased

Diffusing capacity

Normal or increased

Lung compliance

Normal

Normal or mildly decreased Normal

FRC and RV markedly increased; TLC variable Usually decreased lncreased

*FRC, functional residual capacity; RV, residual volume; TLC, totallung capacity.

be only slightly compromised but symptoms may be very prominent, especially cough and hypersecretion. Pulmonary emphysema-In pulmonary emphysema, the obstruction does not res pond to bronchodilator inhalation. There is little or no reversibility. Lung hyperinflation is indicated by an increase in the residual volume and the functional residual capacity. Total Jung capacity may be increased or may remain within the normal range. Diffusing capacity is usually reduced because of the Joss of surface area for gas exchange. Air and blood are matched, so the arterial blood gas values are weil maintained except in end-stage disease. Airway collapse on expiration occurs because of a Joss of the radial traction support for the airways. The residual volume, total Jung capacity, and functional residual capacity may be underestimated by gas dilution and washout techniques. More accurate measurements of these values are obtained by full-body plethysmography. In emphysema, an increase in Jung compliance with Joss oflung recoil can occur. The physiologie abnormalities are readily apparent when viewed in light of the pathologie morphologie changes that occur. Differentiating COPD entities-For prognostic and therapeutic purposes, it is imperative to differentiate, where possible, which of the en titi es making up the spectrum of COPD is present. Table 2 shows the differentiai findings on physiologie tests.

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Arterial blood gas measurements are of little value in differentiating the forms of COPD. They are helpful, however, in determining the severity of Jung dysfunction; in following the course of the disease; and in determining exercise tolerance, by detecting the presence of hypoxemia, hypercapnia, or hypocapnia and the state of acid-base balance. The alveolar-arterial oxygen gradient is useful in determining ventilation-perfusion relationship and in estimating the degree of blood shunting. End-stage COPD is signaled by ventilatory and circulatory failure as manifested by alveolar hypoventilation, hypoxemia, hypercapnia, increased pulmonary vascular resistance, pulmonary hypertension, polycythemia, impaired cardiac output, respiratory acidosis, and cor pulmonale. Patients with hypoxemia and hypercapnia as features of COPD can, through compensation, maintain a normal arterial pH; such patients are in chronic compensated respiratory failure. Classification COPD can be classified clinically and pathophysiologically as one of five types. Type /-Patients in this group have primarily pulmonary emphysema. They have clinical signs and symptoms of emphysema, progressive dyspnea, relatively mild bronchitis, normal PacÛ2 at rest, increased Jung compliance, decreased diffusing capacity, minimal hypoxemia, and lung hyperinflation. These patients do not show evidence of chronic heart

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failure and do not res pond to bronchodilators. Type II-Patients in this group have predominantly chronic bronchitis. Emphysema is minimal or absent. They have a long history of chronic productive cough, poor ventilation-perfusion relationship, recurrent heart failure, alveolar hypoventilation, polycythemia, and marked hypoxemia. These patients have only a mild response to bronchodilators, normal or only mild increases in residual volume, and normal or mildly decreased diffusing capacity. Type /Il-Patients in this group have chronic asthma. They have airway obstruction with a high degree of reversibility on bronchodilator therapy. Residual volume and total Jung capacity may be elevated, but diffusing capacity and Jung compliance are normal. Hypoxemia is mild. They may be hypocapnic as a result ofhyperventilation. In the late stages of disease, respiratory failure may develop. Type IV- This group comprises patients with any combination of types I, Il, and III or patients who do not fulfill the criteria of the foregoing types and who have evidence of either partially reversible or irreversible airway obstruction. This group makes up the greatest percentage of patients seen. Type V-Patients in this group are characterized as having small airway disease. They may or may not be symptomatic. Results of standard pulmonary function tests are normal, but these patients have increased closing volumes, abnormal flow volume loops, impaired frequency dependence of dynamic corn-

pliance, and abnormal isovolumetric flow curves. Summary

The term ''COPD" covers a spectrum of diseases with a common denominator, obstruction to airflow on expiration. Chronic asthma, chronic bronchitis, and pulmonary emphysema are the most prevalent conditions. The signs and symptoms of COPD are similar in ali entities. Differentiai diagnosis may be difficult. Earl y detection of COPD is important, and tests are available for this purpose. For therapeutic and prognostic reasons it is also important to differentiate, wherever possible, which disease entity is predominant in a particular person. This can be done to a high degree by correlating clinical, radiologie, and physiologie findings. The radiologie manifestations ofCOPD are multiple, varied, and in many instances nonspecific. The primary radiologie feature in COPD is lung hyperinflation. In advanced disease, radiologie changes are diagnostic and correlate weil with physiologie and clinicat findings. Frequently, however, the chest film is normal even when clinical and physiologie manifestations indieate advanced disease. • Address reprint requests to Joseph F. Tomashefski, MD, Cleveland Clinic, 9500 Euclid Ave, Cleveland, OH 44106. ReadySource on COPD appears on page 151. CME Credit Quiz on COPD begins on page 149.

References 1. Hodgkin JE, Baie hum OJ, Kass 1, et al: Chronic obstructive airway disease: Current concepts in diagnosis and comprehensive care. JAMA 232:1243-1260. 1975 2. Chronic Obstructive Pulmonary Disease. Ed 5. New York, American Lung Association, 1977 3. Tomashefski JF, Pratt PC: Pulmonary emphysema, pathology and pathogenesis. Med Clin North Am 51:269-281, 1967 4. Macklem PT: Obstruction in small airways: A challenge to medicine. Am J Med 52:721-724, 1972 5. Ahmad M. Tomashefski JF: Small airway disease. Ohio State Med 1 69:756-759, 1973

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6. Mittman C: Summary of a symposium on pulmonary emphysema and proteolysis. Am Rev Respir Dis 105:430, 1972 7. Fraser RG, Pare JP: Diagnosis of Diseases of the Chest: An Integrated Study Based on the Abnormal Roentgenogram. Philadelphia. WB Saunders Co, 1970, p%6 8. Sutinen S, Christoforidis AJ, Klugh GA, et al: Roentgenologic criteria for the recognition of nonsymptomatic pulmonary emphysema: Correlation between roentgenologic findings and pulmonary pathology. Am Rev Respir Dis 91:69-76, 1965

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Definition, differentiation, and classification of COPD.

Postgraduate Medicine ISSN: 0032-5481 (Print) 1941-9260 (Online) Journal homepage: http://www.tandfonline.com/loi/ipgm20 Definition, differentiation...
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