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= Lower Airway Diseases =

Acute Bronchitis
Acute bronchitis is an acute respiratory infection involving the large airways (trachea and bronchi) that is manifested predominantly by cough with or without phlegm production that lasts up to 3 weeks. In patients who are otherwise healthy and without underlying pulmonary disease, bronchitis is most commonly caused by a viral infection. The viruses most commonly implicated are influenza B, influenza A, parainfluenza, and RSV. Viruses that are predominantly associated with upper respiratory tract infection, including coronavirus, rhinovirus, and adenovirus, have also been implicated as causes of acute bronchitis. Acute bronchitis due to bacterial infection is less common and is seen more commonly in patients who have chronic lung disease. The bacteria that have been causally linked to acute bronchitis in otherwise healthy individuals include only Mycoplasma pneumoniae, Chlamydia pneumoniae, Bordetella pertussis, and Bordetella parapertussis. Staphylococcus and gram- negative bacteria are common causes of bronchitis among hospitalized individuals.

Management
Viral bronchitis can be managed with supportive care only as most individuals who are otherwise healthy recover without specific treatment. If significant airway obstruction or hyper-reactivity is present, inhaled bronchodilators, such as albuterol, can be useful. Cough suppressants, such as codeine, can also be used for patients whose coughing interferes with sleep. The treatment of bacterial bronchitis includes amoxicillin, amoxicillin-clavulanate, macrolides, and cephalosporins. For suspected or confirmed pertussis infection, treatment with a macrolide or trimethoprim-sulfamethoxazole is appropriate. Inhaled b2-agonist bronchodilators were commonly used in the past but are no longer recommended to alleviate cough.

Dental considerations
Resistance to antibiotics may develop rapidly and last for 10 to 14 days. Thus, patients who are taking amoxicillin for acute bronchitis should be prescribed another type of antibiotic, (such as clindamycin or a cephalosporin) when an antibiotic is needed for an odontogenic infection.

Asthma
Asthma is a respiratory disease characterized by reversible, diffuse stenosis or stricture of the peripheral bronchi, increased responsiveness or sensitivity to different stimuli, and frequently also signs or laboratory test evidence of an allergic alteration. Asthma is a common condition, typically affecting children and with a prevalence of 5-6%. Over half of all affected individuals are between 5-15 years of age.

A distinction is to be made between allergic and non-allergic asthma. Allergic (or extrinsic) asthma is characterized by a family history of asthma, together with an increase in serum IgE titers. These antibodies participate in type I hypersensitivity or immediate sensitivity reactions and are produced in response to exposure to antigens that access the body through the oral or parenteral route, or in aerosol form.

Non-allergic, idiosyncratic or intrinsic asthma in turn constitutes a respiratory disorder manifesting in a heterogeneous group of patients with reversible and recurrent bronchospasm in response to different stimuli such as physical exercise, the inhalation of cold air, emotions, exposure to smoke, hypoxemia, stress, gastroesophageal reflux, etc. Patients with this type of asthma can be sensitive to aspirin and nonsteroidal anti-inflammatory drugs (NSAIDs).

Oral Manifestations
Nasal symptoms, allergic rhinitis, and mouth breathing are common with extrinsic asthma. Patients with asthma who are mouth breathers may have altered naso-respira­tory function, which may be associated with increased upper anterior and total anterior facial height, higher palatal vault, greater overjet, and a higher prevalence of crossbite.

The medications taken by patients who have asthma may contribute to oral disease. For example, β2-agonist inhalers reduce salivary flow by 20% to 35%, decrease plaque pH, and are associated with increased preva­lence of gingivitis and caries in patients with moderate to severe asthma. Gastroesophageal acid reflux is common in patients with asthma and is exacerbated by the use of β-agonists and theophylline. This reflux can contribute to erosion of enamel. Oral candidiasis (acute pseudomembranous type) occurs in approximately 5% of patients who use inhalation steroids for long periods at high dose or frequency. However, development of this condition is rare if a “spacer” or aerosol-holding chamber is attached to the metered-dose inhaler and the mouth is rinsed with water after each use. The condi­tion readily responds to local antifungal therapy (i.e, nystatin, clotrimazole, or fluconazole). Patients should receive instructions on the proper use of their inhaler and the need for oral rinsing. Headache is a frequent adverse effect of antileukotrienes and theophylline. The clinician should be aware of this adverse effect when diagnosing disease in patients with orofacial pain complaints.

Dental management of Asthma
The underlying primary goal in dental management of patients with asthma is to prevent an acute asthma attack. The first step in achieving this goal is to iden­tify patients with asthma by history, followed by assessment to elucidate the surrounding details of the problem, along with prevention of precipitating factors.

Through a good history, the dentist should be able to determine the severity, stability of disease, the type of asthma (e.g, allergic versus nonallergic), the precipitating substances, the frequency and severity of attacks, the times of day when attacks occur. Whether this is a current or past problem, how attacks usually are managed, and whether the patient has received emergency treatment for an acute attack. The clinician must be cognizant of the indications of severe disease: frequent exacerbations, exercise intolerance, FEV1 less than 60%, use of several medications, and a history of visits to an emergency facility for treatment of acute attack.

The stability of the disease can be assessed during the interview component of the history and by clinical exam­ination and the results of laboratory measures. Features such as shortness of breath, wheezing, increased respira­tory rate (more than 50% above normal), FEV1 that has fallen more than 10% or to below 80% of peak FEV1, an eosinophil count that is elevated to above 50/mm3, poor drug use compliance, and emergency department visits within the previous 3 months suggest inadequate treatment and poor stability. Also, the use of more than 1.5 canisters of a beta agonist inhaler per month (more than 200 inhalations per month) or doubling of monthly use indicates high risk for a severe asthma attack. For severe and unstable asthma, consultation with the patient’s physician is advised. Routine dental treatment should be postponed until better control is achieved.Modifications during the preoperative and operative phases of dental management of a patient with asthma can minimize the likelihood of an attack. Patients who have nocturnal asthma should be scheduled for late-morning appointments, when attacks are less likely. Use of operatory odorants (e.g., methyl methacrylate) should be reduced before the patient is treated. Patients should be instructed to regularly use their medications, to bring their inhalers (bronchodilators) to each appointment, and to inform the dentist at the earliest sign or symptom of an asthma attack. Prophylactic inhalation of a patient’s bronchodilator at the beginning of the appointment is a valuable method of preventing an asthma attack. Alter­natively, patients may be advised to bring their spirom­eter and daily expiratory record to the office. The dentist may request that the patient exhale into the spirometer and record the expired volume. A significant drop in lung function (to below 80% of peak FEV1 or a greater than 10% drop from previously recorded values) indicates that prophylactic use of the inhaler or referral to a physi­cian is needed. The use of a pulse oximeter also is valu­able for determining the patient’s oxygen saturation level. In healthy patients, this value remains between 97% and 100%, whereas a drop to 91% or below indicates poor oxygen exchange and the need for intervention.

Because stress is implicated as a precipitating factor in asthma attacks and dental treatment may result in decreased lung function, all dental staff members should make every effort to identify patients who are anxious and provide a stress-free environment through establishment of rapport and openness. Preoperative and intraoperative sedation may be desirable. If sedation is required, nitrous oxide–oxygen inhalation is best. Nitrous oxide is not a respiratory depressant, nor is it an irritant to the tracheobronchial tree. Oral premedica­tion may be accomplished with small doses of a short-acting benzodiazepine. Reasonable alternatives with children are hydroxyzine (Vistaril), for its antihistamine and sedative properties, and ketamine, which causes bronchodilation. Barbiturates and narcotics, particularly meperidine, are histamine-releasing drugs that can provoke an attack. Outpatient general anesthesia gener­ally is contraindicated for patients with asthma.

Selection of local anesthetic may require adjustment. In 1987, the U.S. Food and Drug Administration (FDA) warned that drugs that contained sulfites were a cause of allergic-type reactions in susceptible individu­als. Sulfite preservatives are found in local anesthetic solutions that contain epinephrine or levonordefrin, although the amount of sulfite in a local anesthetic car­tridge is less than the amount commonly found in an average serving of certain foods. Although rare, at least one case of an acute asthma attack precipitated by expo­sure to sulfites has been reported. Thus, the use of local anesthetic without epinephrine or levonordefrin may be advisable for patients with moderate to severe disease. Because relevant data remain limited, the dentist should discuss with the patient any past responses to local anes­thetics and allergy to sulfites and should consult with the physician on this issue. As an alternative, local anes­thetics without a vasoconstrictor may be used in at-risk patients.

Patients with asthma who are medicated over the long term with systemic corticosteroids may require supple­mentation for major surgical procedures if their health is poor. However, long-term use of inhaled corticosteroids rarely causes adrenal suppression unless the daily dosage exceeds 1.5 mg of beclometha­sone dipropionate or its equivalent. Administration of aspirin-containing medication or other nonsteroidal anti-inflammatory drugs to patients with asthma is not advisable, because aspirin ingestion is associated with the precipitation of asthma attacks in a small percentage of patients. Likewise, barbiturates and narcotics are best not used, because they also may precipitate an asthma attack. Antihistamines have ben­eficial properties but should be used cautiously because of their drying effects. Patients who are taking theophyl­line preparations should not be given macrolide antibiot­ics (i.e., erythromycin and azithromycin) or ciprofloxacin hydrochloride, because these agents interact with the­ophylline to produce a potentially toxic blood level of theophylline. To prevent serious toxicity, the dentist should ask the patient who takes theophylline whether the dosage is being monitored on the basis of serum theophylline levels (recommended to be less than 10 μg/ mL). Approximately 3% of patients who take zileuton exhibit elevated alanine transaminase levels, reflecting liver dysfunction that may affect the metabolism of den­tally administered drugs.