Table 18.1 Nomenclature of bone tumors
Fig. 21 COPD. Section of bronchial mucosa stained for mucus glands by PAS showing increase in mucussecreting goblet cells.
Fig. 22 Pathological changes in the airways in chronic bronchitis and emphysema.
Fig. 23 Influence of smoking on airflow limitation.
• Tobacco exposure
• Occupational exposure to pulmonary toxins (e.g., cadmium)
• Atmospheric pollution
• a1 antitrypsin deficiency (rare; <1% of COPD patients)
• Respiratory infections
• Cystic fibrosis
• Pulmonary embolism
• Sleep apnea, obstructive
Chest x-ray examination, pulmonary function testing, blood gases (in patients with acute exacerbation)
• CBC may reveal leukocytosis with “shift to the left” during acute exacerbation.
• Sputum may be purulent with bacterial respiratory tract infections. Sputum staining and cultures are usually reserved for cases that are refractory to antibiotic therapy.
• ABGS: normocapnia, mild to moderate hypoxemia may be present.
• Pulmonary function testing: abnormal diffusing capacity, increased total lung capacity and/or residual volume, fixed reduction in FEV1 are present with emphysema; normal diffusing capacity, reduced FEV1 are present with chronic bronchitis. Generally, acute spirometry should not be used to diagnose an exacerbation or assess its severity.
Chest x-ray examination:
• Hyperinflation with flattened diaphragm, tending of the diaphragm at the rib, and increased retrosternal chest space
• Decreased vascular markings and bullae in patients with emphysema
• Thickened bronchial markings and enlarged right side of the heart in patients with chronic bronchitis
• Weight loss in patients with chronic bronchitis.
• Avoidance of tobacco use and elimination of air pollutants.
• Supplemental oxygen, usually through a face mask to ensure oxygen saturation >88% measured by pulse oximetry.
• Pulmonary toilet: careful nasotracheal suction is indicated in patients with excessive secretions and inability to expectorate. Mechanical percussion of the chest as applied by a physical or respiratory therapist is ineffective with acute exacerbations of COPD.
ACUTE GENERAL Rx
• Acute exacerbation of COPD can be treated with:
1. Inhaled anticholinergic bronchodilators such as ipratropium are very productive.
2. Inhaled short-acting b2 agonists or use of a nebulizer to provide alauterol or a similar agent with saline and oxygen enhances delivery of the medications to the airways.
3. Corticosteroids: in the hospital setting, IV methylprednisolone 50- to 100-mg bolus, then q6-8h; taper as soon as possible. In the out-patient setting, oral prednisone 40 mg/day initially, decreasing the dose by 10 mg every other day is generally effective. Inhaled corticosteroids are useful in patients with moderate to severe COPD and in patients with frequent exacerbations.
4. Judicious oxygen administration (hypercapnia and further respiratory compromise may occur after high-flow oxygen therapy); use of a venturi-type mask delivering an inspired oxygen fraction of 24% to 28% is preferred to nasal cannula.
5. Noninvasive positive pressure ventilation delivered by a facial or nasal mask in the treatment of chronic restrictive thoracic disease may obviate the need for intratracheal intubation.
• Antibiotics are indicated in suspected respiratory infection (e.g. increased purulence and volume of phlegm).
1. Haemophilus influenzae, streptococcus pneumoniae are frequent causes of acute bronchitis.
2. Oral antibiotics of choice are azithromycin, levofloxacin, or cefuroxime.
3. The use of antibiotics is beneficial in exacerbations of COPD presenting with increased dyspnea and sputum purulence (especially if the patient is febrile).
• Guaifenesin may improve cough symptoms and mucus clearance; however, mucolytic medications are generally ineffective. Their benefits may be greatest in patients with more advanced disease.
• Intubation and mechanical ventilation may be necessary if above measures fail to provide improvement.
• Following the initial episode of respiratory failure, 5-yr survival is approximately 28%.
• Development of cor pulmonale or hypercapnia and persistent tachycardia are poor prognostic indicators.
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Chronic obstructive pulmonary disease
Chronic obstructive pulmonary disease (COPD) is a disorder characterized by the presence of airflow limitation that is not fully reversible. COPD encompasses emphysema, characterized by loss of lung elasticity and destruction of lung parenchyma with enlargement of air spaces, and chronic bronchitis, characterized by obstruction of small airways and productive cough greater than 3 months duration for more than 2 successive years. Patients with COPD are classically subdivided in two major groups based on their appearance:
1. “Blue bloaters” are patients with chronic bronchitis; the name is derived from the bluish tinge of the skin (secondary to chronic hypoxemia and hypercapnia) and from the frequent presence of peripheral edema (secondary to cor pulmonale); chronic cough with production of large amounts of sputum is characteristic.
2. “Pink puffers” are patients with emphysema; they have a cachectic appearance but pink skin color (adequate oxygen saturation); shortness of breath is manifested by pursed-lip breathing and use of accessory muscles of respiration.
EPIDEMIOLOGY & DEMOGRAPHICS
• COPD affects 16 million Americans and is responsible for >80,000 deaths / year.
• Highest incidence is in males >40 years.
• 16 million office visits, 500,000 hospitalizations, and >$18 billion in direct health care costs annually can be attributed to COPD.
PHYSICAL FINDINGS & CLINICAL PRESENTATION
• Blue bloaters (chronic bronchitis): peripheral cyanosis, productive cough, tachypnea, tachycardia
• Pink puffers (emphysema): dyspnea, pursed-lip breathing with use of accessory muscles for respiration, decreased breath sounds
• Possible wheezing in both patients with chronic bronchitis and emphysema
• Features of both chronic bronchitis and emphysema in many patients with COPD.
• Acute exacerbation of COPD is mainly a clinical diagnosis and generally manifests with worsening dyspnea, increase in sputum purulence, and increase in sputum volume
The most consistent pathological finding in COPD is increased numbers of mucus-secreting goblet cells in the bronchial mucosa, especially in the larger bronchi (Fig. 21). In more advanced cases, the bronchi become overtly inflamed and pus is seen in the lumen.
Microscopically there is infiltration of the walls of the bronchi and bronchioles with acute and chronic inflammatory cells; lymphoid follicles may develop in severe disease. In contrast to asthma, the lymphocytic infiltrate is predominantly CD8+. The epithelial layer may become ulcerated and, when the ulcers heal, squamous epithelium replaces the columnar cells. The inflammation is followed by scarring and thickening of the walls which leads to widespread narrowing in the small airways (Fig. 22).
The small airways are particularly affected early in the disease, initially without the development of any significant breathlessness. This initial inflammation of the small airways is reversible and accounts for the improvement in airway function if smoking is stopped early. In later stages the inflammation continues, even if smoking is stopped.
Further progression of the airways disease leads to progressive squamous cell metaplasia, and fibrosis of the bronchial walls. The physiological consequence of these changes is the development of airflow limitation. If the airway narrowing is combined with emphysema (causing loss of the elastic recoil of the lung with collapse of small airways during expiration) the resulting airflow limitation is even more severe.
Emphysema is defined pathologically as dilatation and destruction of the lung tissue distal to the terminal bronchiole. It is classified according to the site of damage:
■ Centri-acinar emphysema. Distension and damage of lung tissue is concentrated around the respiratory bronchioles, whilst the more distal alveolar ducts and alveoli tend to be well preserved. This form of emphysema is extremely common; when of modest extent, it is not necessarily associated with disability. Severe centri-acinar emphysema is associated with substantial airflow limitation.
■ Pan-acinar emphysema. This is less common. Distension and destruction appear to involve the whole of the acinus, and in the extreme form the lung becomes a mass of bullae. Severe airflow limitation and VA Q mismatch occur. This type of emphysema occurs in α1-antitrypsin deficiency.
■ Irregular emphysema. There is scarring and damage affecting the lung parenchyma patchily without particular regard for acinar structure.
Emphysema leads to expiratory airflow limitation and air trapping. The loss of lung elastic recoil results in an increase in TLC, and premature closure of airways limits expiratory flow while the loss of alveoli results in decreased capacity for gas transfer.
VA Q mismatch occurs partly because of damage and mucus plugging of smaller airways from chronic inflammation, and partly because of the rapid expiratory closure of the smaller airways owing to loss of elastic recoil from emphysema. This leads to a fall in PaO2 and an increase in the work of respiration.
CO2 excretion is not impaired to the same extent and indeed many patients will show low normal PaCO2 values due to increasing their ventilation in an attempt to maintain normal blood gases by increasing their respiratory effort. Other patients fail to maintain their respiratory effort and as a consequence their CO2 levels increase. In the short term, this rise in CO2 leads to stimulation of respiration but in the long term, these patients often become insensitive to CO2 and come to depend on hypoxaemia to drive their ventilation. These patients appear less breathless and because of their reduced O2 saturation, they start to retain fluid and stimulate erythrocyte production (leading to polycythaemia). In consequence they become bloated, plethoric and cyanosed, the typical appearance of the ‘blue bloater’. Attempts to abolish hypoxaemia by administering oxygen can make the situation much worse by decreasing respiratory drive in these patients who depend on hypoxia to drive their ventilation.
The classic Fletcher and Peto studies (Fig. 23) show that there is a loss of 50 mL per year in FEV1 in COPD compared to 20 mL per year in healthy people.
In summary, three mechanisms have been suggested for this limitation of airflow in small airways (< 2 mm in diameter).
■ Loss of elasticity and alveolar attachments of airways due to emphysema. This reduces the elastic recoil and the airways collapse during expiration.
■ Inflammation and scarring cause the small airways to narrow.
■ Mucus secretion which blocks the airways.