The majority of diseases of the respiratory system fall into one of three major categories: (1) obstructive lung diseases; (2) restrictive disorders; and (3) abnormalities of the vasculature. Obstructive lung diseases are most common and primarily include disorders of the airways such as asthma, chronic obstructive pulmonary disease (COPD), bronchiectasis, and bronchiolitis. Diseases resulting in restrictive pathophysiology include parenchymal lung diseases, abnormalities of the chest wall and pleura, as well as neuromuscular disease. Disorders of the pulmonary vasculature are not always recognized and include pulmonary embolism, pulmonary hypertension, and pulmonary venoocclusive disease. Although many specific diseases fall into these major categories, both infective and neoplastic processes can affect the respiratory system and may result in myriad pathologic findings, including obstruction, restriction, and pulmonary vascular disease (see Table 251-1).
Table 251–1. Categories of Respiratory Disease
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Table 251–1. Categories of Respiratory Disease
Obstructive lung disease
Restrictive pathophysiology—parenchymal disease
Idiopathic pulmonary fibrosis (IPF)
Desquamative interstitial pneumonitis (DIP)
Restrictive pathophysiology—neuromuscular weakness
Amyotrophic lateral sclerosis (ALS)
Restrictive pathophysiology—chest wall/pleural disease
|Ankylosing spondylitis |
|Chronic pleural effusions|
Pulmonary vascular disease
|Pulmonary arterial hypertension (PAH)|
Bronchogenic carcinoma (non-small-cell and small cell)
The majority of respiratory diseases present with abnormal gas exchange. Disorders can also be grouped into the categories of gas exchange abnormalities, including hypoxemic, hypercarbic, or combined impairment. Importantly, many diseases of the lung do not manifest gas exchange abnormalities.
As with the evaluation of most patients, the approach to a patient with disease of the respiratory system begins with a thorough history. A focused physical examination is helpful in further categorizing the specific pathophysiology. Many patients will subsequently undergo pulmonary function testing, chest imaging, blood and sputum analysis, a variety of serologic or microbiologic studies, and diagnostic procedures, such as bronchoscopy. This step-wise approach is discussed in detail below.
The cardinal symptoms of respiratory disease are dyspnea and cough (Chaps. 33 and 34). Dyspnea can result from many causes, some of which are not predominantly caused by lung pathology. The words a patient uses to describe breathlessness or shortness of breath can suggest certain etiologies of the dyspnea. Patients with obstructive lung disease often complain of “chest tightness” or “inability to get a deep breath,” whereas patients with congestive heart failure more commonly report “air hunger” or a sense of suffocation.
The tempo of onset and duration of a patient's dyspnea are helpful in determining the etiology. Acute shortness of breath is usually associated with sudden physiological changes, such as laryngeal edema, bronchospasm, myocardial infarction, pulmonary embolism, or pneumothorax. Patients with underlying lung disease commonly have progressive shortness of breath or episodic dyspnea. Patients with COPD and idiopathic pulmonary fibrosis (IPF) have a gradual progression of dyspnea on exertion, punctuated by acute exacerbations of shortness of breath. In contrast, most asthmatics have normal breathing the majority of the time and have recurrent episodes of dyspnea usually associated with specific triggers, such as an upper respiratory tract infection or exposure to allergens.
Specific questioning should focus on factors that incite the dyspnea, as well as any intervention that helps resolve the patient's shortness of breath. Of the obstructive lung diseases, asthma is most likely to have specific triggers related to sudden onset of dyspnea, although this can also be true of COPD. Many patients with lung disease report dyspnea on exertion. It is useful to determine the degree of activity that results in shortness of breath as it gives the clinician a gauge of the patient's degree of disability. Many patients adapt their level of activity to accommodate progressive limitation. For this reason it is important, particularly in older patients, to delineate the activities in which they engage and how they have changed over time. Dyspnea on exertion is often an early symptom of underlying lung or heart disease and warrants a thorough evaluation.
Cough is the other common presenting symptom that generally indicates disease of the respiratory system. The clinician should inquire about the duration of the cough, whether or not it associated with sputum production, and any specific triggers that induce it. Acute cough productive of phlegm is often a symptom of infection of the respiratory system, including processes affecting the upper airway (e.g., sinusitis, tracheitis) as well as the lower airways (e.g., bronchitis, bronchiectasis) and lung parenchyma (e.g., pneumonia). Both the quantity and quality of the sputum, including whether it is blood-streaked or frankly bloody, should be determined. Hemoptysis warrants an evaluation as delineated in Chap. 34.
Chronic cough (defined as persisting for more than 8 weeks) is commonly associated with obstructive lung diseases, particularly asthma and chronic bronchitis, as well as “nonrespiratory” diseases, such as gastroesophageal reflux (GERD) and postnasal drip. Diffuse parenchymal lung diseases, including idiopathic pulmonary fibrosis, frequently present with a persistent, nonproductive cough. As with dyspnea, all causes of cough are not respiratory in origin, and assessment should consider a broad differential, including cardiac and gastrointestinal diseases as well as psychogenic causes.
Patients with respiratory disease may complain of wheezing, which is suggestive of airways disease, particularly asthma. Hemoptysis, which must be distinguished from epistaxis or hematemesis, can be a symptom of a variety of lung diseases, including infections of the respiratory tract, bronchogenic carcinoma, and pulmonary embolism. Chest pain or discomfort is also often thought to be respiratory in origin. As the lung parenchyma is not innervated with pain fibers, pain in the chest from respiratory disorders usually results from either diseases of the parietal pleura (e.g., pneumothorax) or pulmonary vascular diseases (e.g., pulmonary hypertension). As many diseases of the lung can result ...