Respiratory diseases

Noninfectious respiratory diseases are divided into two groups: (1) asthma and (2) COPD (see Figure 19-2). COPD is further divided into chronic bronchitis and emphysema. Other respiratory problems are related to respiratory infections, principally viral or bacterial.

Asthma

One common respiratory disease is asthma. It is characterized by reversible airway obstruction and is associated with reduction in expiratory airflow. A few hours later, inflammation occurs, resulting in an increase in secretions in the lungs and swelling in the bronchioles. Asthma is classified as being either intermittent or persistent. Persistent asthma is further categorized as mild, moderate, or severe. Patients with intermittent asthma experience symptoms less than two times a month and the symptoms do not interfere with normal activity. Persistent asthma occurs anywhere from more than twice a week to all day long. Persistent asthma can cause minor limitation of normal activities, and severe persistent asthma can severely limit the patient’s normal activities. When asthma is treated, both components of the disease must be addressed. The National Asthma Education and Prevention Program Expert Panel Report 3, published in October 2007, presents the latest recommendations of the National Heart Lung and Blood Institute regarding asthma therapy. Table 19-1 reviews the stepwise approach for managing asthma in children older than 12 years and adults.

Asthma may be precipitated by allergens, pollution, exercise, stress, or upper respiratory infection (allergic reaction to viruses). The patient with status asthmaticus has persistent life-threatening bronchospasm despite drug therapy. Environmental pollution may also play an important role in the increase in asthma. The dental hygienist should manage dental patients with asthma so as to induce minimal stress. Patients should bring their fast-acting β₂-agonist inhalers to be used prophylactically or in the management of an acute asthmatic attack in the dental office. Signs of asthma include shortness of breath and wheezing. By observing and asking the patient about asthma control before the dental appointment, the dental hygienist can prevent an acute attack. β₂-adrenergic agonists, xanthines, cromolyn, corticosteroids, leukotriene (LT) altering agents, and anticholinergics are used to treat this disease (Figure 19-3).

Chronic Obstructive Pulmonary Disease

COPD is characterized by irreversible airway obstruction, which occurs with either chronic bronchitis or emphysema. Smoking is associated with almost all cases of COPD. Chronic bronchitis is a result of chronic inflammation of the airways and excessive sputum production. Emphysema is characterized by alveolar destruction with air space enlargement and airway collapse. Tables 19-2 and 19-3 review the recommended treatment regimens for COPD. The anticholinergics are the first-line agents, but β₂-adrenergic agonists are also used to produce bronchodilation in patients with this disease. In many instances patients receive a combination metered-dose inhaler containing an anticholinergic drug and a β₂ agonist. COPD is associated with an increase in the incidence of bronchospasm and with fixed airway obstruction. Patients with upper respiratory tract infections also often take β₂ adrenergic agonists for bronchoconstriction, antihistamines to reduce secretions, expectorants to thin sputum, and antitussives to control coughing. Each drug group is discussed separately in the section on respiratory infections.

In the normal person, the drive for ventilation (breathing) is stimulated by an elevation in the partial pressure of carbon dioxide (Paco₂). The partial pressure of oxygen (Pao₂) can vary widely without stimulating ventilation in the normal patient. Patients with COPD, because their ventilation is compromised, experience a gradual rise in Paco₂ over time. Because this mechanism becomes resistant to changes in Paco₂, a new stimulus emerges, the partial pressure of Pao₂. The patient’s ventilation is then driven by a decrease in Pao₂. If a patient with COPD is given oxygen and the Pao₂ rises, the stimulant to breathing is removed, and apnea may be induced. For patients with severe COPD, it is suggested that the rate of oxygen administration be limited to less than 3 L/min. Other literature recommends that in the patient with severe COPD, oxygen by nasal cannula be used during a dental appointment, especially if pain or stress is expected (increased oxygen demand).

The MDI, developed in the 1950s, provides a useful method to administer certain medications to the respiratory tree (Figure 19-4). It is the preferred route of delivery for most asthma drugs. Its advantages include the following:

Disadvantages of MDIs are that they are difficult to use properly (particularly for children) and they can be abused, with a resultant decrease in response. Additional patient education is required to get the most from this dose form. Often, a “spacer” is placed between the MDI and the mouth to increase the amount of drug delivered to the lungs (see Figure 19-4B). Medications currently available in MDIs include β-agonists, both specific and nonspecific; corticosteroids; cromolyn; and anticholinergic drugs.

Chlorofluorocarbons (CFCs), which have ozone-depleting properties, have been phased out as propellants in MDIs. Nonchlorinated hydrofluoroalkane (HFA) propellants, which do not deplete the ozone layer, have replaced CFCs.

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