Figure 45.1. NAEPP stepwise approach to asthma therapy. Source: National Asthma Education and Prevention Program: Expert Panel Report 3: Guidelines for the diagnosis and management of asthma: National Institutes of Health Publication No. 08-4051. Bethesda, MD, 2007.

    As control of symptoms is achieved, patients are “stepped down” in therapy as appropriate with the goal of minimizing symptoms and maintaining lung function with the least medication necessary. Once control has been achieved, clinicians should work with patients to develop an “action plan” based on symptoms and peak flow measurement. Each plan is individually tailored and can allow a reliable patient to treat an exacerbation early before severe symptoms and a true asthmatic attack ensue.

COPD

The Global Initiative for Chronic Obstructive Lung Disease characterizes COPD as a disease of “airflow limitation that is not fully reversible. The airflow limitation is usually progressive and associated with an abnormal inflammatory response of the lung to noxious particles or gases.” Most commonly, the noxious particles and gases are from cigarette smoke. This disease, in its myriad of presentations, conservatively affects more than 20 million Americans and is the third leading cause of death in the United States. With this in mind, it is important for all clinicians to be familiar with the diagnosis and treatment of COPD.

    Patients with intermittent dyspnea and cough who have long-term exposure to cigarette smoke should be assessed for evidence of airflow obstruction by spirometry. As is the case in asthma, obstruction is generally defined as a ratio of FEV₁/FVC <70%. The diagnosis of COPD is made by the demonstration of obstruction that is not fully reversible with a short-acting bronchodilator in the setting of the appropriate exposure history. Spirometry is particularly helpful, as the severity of COPD is based on the measured FEV₁ (see table 45.1). Additional testing including lung volumes, Dlco, blood gas sampling, and chest tomography do not need to be routinely obtained but should be considered on an individual basis, particularly in those patients who have severe symptoms, resting hypoxemia, or severely impaired lung function.

    The most important step in the treatment of COPD is to prevent its development through smoking cessation. Similarly, patients with established COPD will slow the rate of decline in lung function when they quit smoking. Therapies for smoking cessation include both nonpharmacologic approaches (e.g., support groups) and medications (see table 45.2). Physicians should inquire about smoking cessation on each patient visit.

    Pharmacologic therapy for stable, chronic COPD includes both short- and long-acting inhaled bronchodilators including beta agonists and anticholinergics as well as inhaled steroids. In contrast to asthma treatment, multiple studies support the use of LABAs alone in the treatment of COPD without the evidence of increased mortality. Most patients are initially treated with either a long-acting anticholinergic or LABA. Inhaled steroids are reserved for patients with moderate to severe COPD (based on FEV₁) and recurrent exacerbations of disease. All patients should also receive pneumococcal and influenza vaccines.

    Patients with more severe disease may develop resting hypoxemia. When oxygen saturation is <88% at rest, supplemental oxygen should be initiated as there is a clear mortality benefit to this therapy. Patients with more severe disease also benefit from pulmonary rehabilitation. The clinician should consider referral of such patients to a specialist because certain subsets of COPD patients may benefit from lung volume reduction surgery, lung transplantation, or other novel therapies.

DIFFUSE PARENCHYMAL LUNG DISEASES

There are a variety of less common diseases that diffusely affect the lung parenchyma. In the past, these conditions were referred to as the interstitial lung diseases (ILD). Because these processes often affect more than the interstitium, the grouping is now commonly called diffuse parenchymal lung disease (DPLD). The classic DPLD is idiopathic pulmonary fibrosis (IPF), but there are a myriad of other poorly understood diseases including sarcoidosis, cryptogenic organizing pneumonia (COP), and hypersensitivity pneumonitis included in the DPLDs.

    IPF is an insidious disease of presumed abnormal wound healing that results in progressive scarring of the lungs with impaired gas exchange and restrictive pathophysiology. The cause of IPF, as the name implies, is unknown. Patients present with progressive dyspnea on exertion and nonproductive cough, often initially misdiagnosed as asthma or pneumonia. On examination, basilar crackles and clubbing are common, and most patients progress to resting hypoxemia. Diagnosis is occasionally made by classic computed tomography (CT) scan appearance with basilar, subpleural honeycombing with a lack of ground glass opacities, however most patients require a lung biopsy for definitive diagnosis. On biopsy, subpleural changes including “fibroblastic foci” within heterogeneous areas of injury and fibrosis are pathognomonic for IPF. Unfortunately, at this time there are no effective therapies for IPF. Patients should be referred early in their course for evaluation for possible lung transplantation.

    Other DPLDs can be grouped into those with known causes and those of unknown etiology with, unfortunately, many more diseases in the latter category. Changes in the lung related to inorganic inhalational exposures are termed pneumoconioses. The best-described pneumoconiosis is asbestosis. This disease is quite similar pathologically to IPF but is secondary to chronic asbestos exposure. As with IPF, there is no known therapy for asbestosis, although it is rarely as aggressively progressive as IPF. In contrast, inhalation of organic substances can lead to a granulomatous inflammation along the bronchovascular bundles called hypersensitivity pneumonitis (HP). A variety of materials can result in HP, and well-described exposures include actinomycetes, pigeon droppings, atypical mycobacteria (commonly from hot tubs), and Aspergillus. The initial therapy is removal of the offending agent. In the acute phase, these reactions are generally responsive to glucocorticoids; however, with chronic exposure the parenchymal changes can become irreversible.

    There are a series of poorly understood DPLDs related to cigarette smoking. These include desquamative interstitial pneumonitis (DIP), respiratory bronchiolitis interstitial lung disease (RBILD), and pulmonary Langerhans-cell histiocytosis (PLCH). All of these are much less common than COPD, which should be suspected first in patients with a history of tobacco exposure and new dyspnea or cough.

    Sarcoidosis is a multiorgan disease of unknown etiology. The hallmark of sarcoid is noncaseating granulomatous inflammation. Lung involvement ranges from asymptomatic hilar lymphadenopathy to end-stage fibrosis. Most lung disease is at least initially responsive to glucocorticoids, although many patients will require no therapy. Other organs commonly affected by sarcoid include the skin (e.g., erythema nodosum, lupus pernio), heart, liver, central nervous system, and eyes.

VENOUS THROMBOEMBOLIC DISEASE

Although the incidence markedly increases after the age of 60, patients of all ages, with a variety of risk factors and underlying diseases, may develop venous thrombolic disease (VTE), which encompasses both deep venous thrombosis (DVT) and pulmonary embolism (PE). The majority of patients who develop VTE have one or more clinical risk factors including underlying malignancy, cigarette smoking, oral contraceptive use, recent surgery, trauma, or immobilization. In addition, those patients with a personal or family history are at increased risk, suggesting a genetic risk factor such as factor V Leiden or prothrombin gene mutation.

    Patients with DVT usually present with symptoms related to lower extremity swelling and discomfort. Patients with PE classically present with dyspnea, pleuritic chest discomfort and mild hypoxemia; however, PE can be clinically silent or result in hemodynamic collapse, refractory hypoxemia, and death. For this reason, clinicians need to always be alert to the possibility of PE, particularly in patients with multiple risk factors for VTE.

    Diagnosis of VTE can be quite challenging. The gold standard for confirmation of DVT is a duplex venous ultrasound, but CT, magnetic resonance (MR) angiography, and contrast venography are also used in certain clinical situations. In the recent 5–10 years, contrast CT scan has become the modality by which most pulmonary emboli are diagnosed, whereas in the past ventilation-perfusion scans were more common. MR and pulmonary angiography remain other options; however, timeliness and invasiveness (respectively) are issues with these studies. In many clinical situations, it is more important to “rule out” pulmonary embolism, particularly when there is a low clinical probability. In these settings, the measurement of a D-dimer may be helpful, as it has a strong negative predictive value in outpatient populations with low clinical likelihood of PE.

    The mainstay of treatment of VTE is anticoagulation either with heparin products, warfarin, or fondaparinux. For patients who cannot be anticoagulated, placement of an inferior vena cava filter can acutely protect against a DVT resulting in a PE but may have significant long-term morbidity. The use of thrombolytic agents, catheter, or surgical intervention in the setting of massive pulmonary emboli remains an area of ongoing debate. As all of these interventions have limitations, it is encouraging that new therapies are on the horizon for all aspects of VTE.

OBSTRUCTIVE SLEEP APNEA

Obstructive sleep apnea (OSA) is an underdiagnosed disease that is estimated to affect approximately 5% of the adult population. Because there are many long-term health consequences of OSA, it is important for all clinicians to consider the possibility of this diagnosis in their patients. Patients with OSA have increased rates of hypertension, coronary artery disease, heart failure, diabetes, and stroke, as well as significantly increased risk of motor vehicle accidents.

    The hallmark of OSA is the obstructive apnea where there is full collapse of the airway resulting in complete cessation of breathing for at least 10 seconds. The diagnosis of OSA, however, relies on the number of apneas and hypopneas (i.e., reduced airflow for at least 10 seconds due to partial collapse) per hour of sleep, often referred to as the apnea-hypopnea index (AHI). Most clinicians use a threshold of at least 15 episodes per hour to diagnose OSA in asymptomatic patients and between 5 and 15 events per hour in symptomatic patients. In some settings, the number of respiratory event–related arousals (RERA) per hour is also tabulated, as these events related to increased work of breathing due to partial airway collapse are also disruptive to sleep.

    Risk for OSA correlates with obesity and advanced age. There are a variety of other risk factors, some of which are modifiable, which should be assessed in any patient suspected of having OSA (see box 45.1). In addition, an individual patient’s upper airway anatomy impacts the risk of OSA, as smaller upper airway lumens are more likely to collapse. This can be affected by large tonsils, large tongue, and increased adipose tissue.

    Several symptoms should suggest a diagnosis of OSA. These include snoring (the most commonly reported symptom), daytime sleepiness, morning headaches, memory impairment, and depression. Patients are often formally evaluated with the Epworth Sleepiness Scale, which is a validated tool to assess for excessive daytime sleepiness. On examination, obesity and hypertension should raise a clinician’s suspicion; however, the airway examination is most helpful. Mallampati airway scores have been shown to predict risk for OSA.

Box 45.1 RISK FACTORS FOR OSA

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