Pathophysiology and Etiology of the Asthma

Asthma, a chronic disease process, affects approximately 18 million people in the United States. While asthma can be reversible, failure to control symptoms and provide adequate and timely treatment can lead to a decrease in respiratory function, which ultimately increases the risk of death (Durham, Fowler, Smith, & Sterrett, 2017). Accurate and timely nursing care can help patients manage their symptoms and increase their quality of life while decreasing hospitalizations and related costs (Keep, Reiffer, & Bahl, 2016).

Disease Condition

Asthma is a chronic condition marked by repeated episodes of airflow obstruction, bronchial hyperresponsiveness, and chronic inflammation of the airway.

It affects approximately 18 million adults in the United States (Durham, et al., 2017). However, estimates suggest that approximately 400 million people worldwide will be affected by asthma by 2025 with a projected 250,000 annual asthma-related deaths worldwide (Alhassan, Hattab, Bajwa, Bihler, & Singh, 2016).

Pathophysiology and Etiology

Asthma is a disorder that affects the bronchioles in the lungs. When triggered by either allergic or nonallergic stimuli, an immune reaction occurs (Alhassan, et al., 2016). When an asthma exacerbation occurs, mast cells release histamine, leukotrienes, interleukins, and prostaglandins, which cause mucus to be produced and spasms in the smooth muscles within the bronchiole walls. This action decreases the size of the bronchioles and, in turn, decreases inspiratory and expiratory air flow (Keep, et al., 2016). While airway obstruction is potentially reversible, failure to avoid asthmatic flares can lead to a decrease in overall respiratory function, increase the risk of death, and can cause chronic airway remodeling with only partially reversible airflow obstruction (Durham, et al., 2017).

Risk Factors

Risk factors that can trigger an asthmatic response can both modifiable and nonmodifiable. Obesity, particularly childhood obesity, is a modifiable risk factor for adult asthma. Both a child's sedentary lifestyle and decreased physical activity lead to central obesity, which increases the risk for asthma. Weight reduction is encouraged due to positive effect on lung function. Another modifiable factor is occupational exposure. This can include jobs that involve animals, plants, or insects or irritants such as gases, fumes, or dust (Alhassan, et al., 2016.) additional modifiable factors include exercise, stress, smoke, medications and pets. There are also nonmodifiable factors that can trigger asthma. These can include a family history of atopic dermatitis, allergies, and asthma, which all can lead to an increased risk of developing asthma, especially if the family history includes a first-degree relative with a history of asthma. Additional nonmodifiable triggers include a gastroesophageal reflux disease, nasal polyps, rhinitis, and sinusitis (Durham, et al., 2017).

Signs and Symptoms

Asthmatic signs and symptoms vary between individuals. The general signs and symptoms include recurrent shortness of breath, wheezing, coughing, and chest tightness. These symptoms can respond to a bronchodilator (Alhassan, et al., 2016). The most frequent finding is expiratory wheezing. Physical findings can include hyper expansion of the chest, use of accessory muscles, prolonged expirations, and retractions (Durham, et al., 2017). These signs are due to the excessive mucus production and the spasm of the smooth muscle of the bronchioles, which reduce the diameter of the airway (Keep, et al., 2016).

Disease Diagnosis

Diagnosis is based on the symptoms and categorized into four categories: mild intermittent, mild persistent, moderate persistent, and severe persistent (Henry, 2016). To determine the category, a thorough personal and family history as well as a physical examination, laboratory, and diagnostic testing can be performed (Durham, et al., 2017).

Laboratory Tests

Laboratory testing can be performed related to a potential diagnosis of asthma. Such laboratory studies can include arterial blood gases (ABGs) to determine the presence of hypoxemia, hypocarbia (can occur in the early phase of an asthma attack), and hypercarbia (can occur in the later phase of an asthma attack). This study is used to evaluate respiratory function and acid-base balance, which would be altered if the exchange of oxygen and carbon dioxide are impaired secondary to excess mucus or constriction in the bronchioles (Van Leeuwen & Bladh, 2015, pp. 293-307). In addition, sputum cultures can be performed to rule out bacterial causes for the symptoms (Henry, 2016).

Radiologic Studies

In addition to laboratory studies, a chest x-ray can also be performed, although not routinely performed in the diagnosis of asthma (Durham, et al., 2017) . A chest x-ray may show hyperinflation or changes in chest structure over the long term (Henry, 2016).

Diagnostic Studies

There are various diagnostic testing that can be performed to assist in diagnosing asthma. These are referred to as pulmonary function studies and they can evalute types of lung disease and assess effectiveness of treatments and medications (Van Leeuwen & Bladh, 2015, pp. 1328-1334). One test is called spirometry. This test is the best diagnostic tool available to objectively assess obstruction of air flow and to evalute the bronchial response to treatment. Spirometry is strongly recommended to confirm an asthma diagnosis. Testing can be performed in the physician's office or an outpatient pulmonary function laboratory. There are two measurements that are needed: forced vital capacity (FVC), which is the maximum amount of air exhaled after a deep breath, and the forced expiratory volume in one second (FEV1), which is the amount of air expelled during the first second of expiration after FVC. FEV1 is the most standardized measurement to evalute for airflow limitation. Spirometry also assesses for reversibility of asthma. Spirometry is performed pre- and post-bronchodilator use to measure the amount of improvement after bronchodilator use, thereby proving reversibility of asthma. (Alhassan, et al., 2016). In asthmatics, the FEV1 is 15 to 20% lower than the expected values (Henry, 2016). To qualify as reversible, at least 12% improvement and 200 mL in FVC and/or FEV1 after use of the bronchodilator or four weeks anti-inflammatory treatment (Alhassan, et al., 2016).

Peak expiratory flow (PEF) can be measured during spirometry and can be helpful in monitoring asthma, although not nearly as reliable as spirometry. PEF is the greatest flow of air during forced exhalation. This can be measured easily with a small device the patient can keep with them. PEF monitoring can be a useful tool in assessing the patient's response to therapy (Alhassan, et al., 2016). Bronchial provocation, also known as bronchial challenge testing, is another useful tool, especially in patients with suspected asthma but a normal spirometry result. This test can determine airway hyperresponsiveness (AHR) by measuring the amount of airway constriction that occurs when exposed to a trigger (Alhassan, et al., 2016). However, while a positive result can be indicative of asthma, it may also indicate other diagnoses such as chronic obstructive pulmonary disease (COPD), cystic fibrosis, or allergic rhinitis. If the test is negative, it can rule out the diagnosis of asthma (Durham, et al., 2017) .

Other challenge tests include methacholine challenge testing (MCT). This specific test is the most common provocative test to evaluate for hyperresponsiveness. MCT can only be performed in a laboratory setting using nebulized methacholine. As MCT has a high sensitivity for asthma but it can also show false positive results in the presence of COPD, cystic fibrosis, or allergic rhinitis (Alhassan, et al., 2016).

Allergy testing, while not diagnostic of asthma, can identify sensitivities to triggers that may cause an asthma attack (Durham, et al., 2017) .

Treatment

Preventative Treatment and Education

Preventative treatment and education are a critical first step in management of asthma. Patients should be made aware of ways to avoid known triggers, such as smoking cessation (both the patient and the family), avoiding pets, limiting carpeting in the home, and the use hypoallergenic pillows (Durham, et al., 2017). Avoiding and Controlling Your Asthma Triggers, a form created by the American Lung Association, can help patients identify triggers and offers advice to avoid or reduce triggers and covers topics such as smoking, pets, pollen, strong odors, dust, and even strong emotions, all of which can trigger an attack. Journaling is also a useful tool to teach asthma patients and one they can also share with their physicians to track day-to-day triggers and symptoms (Keep, et al., 2016).

Motivational interviewing (MI) has been found to be effective in patients to self-manage their asthma. This teaching method is a client-centered therapeutic method to explore and resolve resistance to change. MI encourages patients to identify positive and negative results related to changing or not changing their behaviors. Identification of barriers and solutions enables patients to become independent in their management care and has been found to significantly improve medication compliance and make healthy lifestyle changes (Keep, et al., 2016).

In addition to patients knowing their triggers and how to avoid them, an Asthma Action Plan should be completed for every asthma patient and even comes as a small card that can be kept in a wallet. This plan has green, yellow, and red zones that correlate to the patient's current symptoms. The green zone indicates a patient has well-controlled asthma symptoms without coughing or wheezing and can complete all normal activities. The goal is to stay in the green zone at all times, indicating good control over asthma. The yellow zone indicates difficulty carrying out normal activities due to coughing, wheezing, shortness of breath, or chest tightness. In the yellow zone, medication changes may be necessary, such has using a rescue medication. The yellow zone provides instructions on administering the rescue medication and next steps to take if the rescue medication is not effective. If medication changes in the yellow zone are not effective, it becomes the red zone, which is a medical emergency. Instructions are provided in this action plan regarding medication, contacting the physician, and calling 9-1-1 for emergency services. Additionally, if a peak flow meter is being used by the patient, the physician can set guidelines for the peak flow in each zone to further delineate control or action needed (Keep, et al., 2016).

Medical Management of Acute and Chronic Phases

While prevention methods, such as avoiding the triggers of asthma, are helpful in managing asthma, however, medications may also be necessary. Asthma medications include two categories short-term symptom relief with rescue medications and long-term symptom relief with controllers. Often, a combination of the two are necessary for good control (Durham, et al., 2017) .

Short-term symptom relievers are used for acute asthma symptoms. These include short-acting beta2 agonists (SABA), such as albuterol, and short-acting muscarinic antagonists (SAMA) ipratropium. These medications are bronchodilators, which reduce bronchoconstriction and allow for improved air flow. They have an onset of five minutes, peak in 30 to 60 minutes, and last for four to six hours (Alhassan, et al., 2016). While they quickly act to reduce asthmatic symptoms and have minimal symptoms, adverse side effects such has tachycardia, dysrhythmia, or tremors can occur. SAMA medications can be used in addition to SABA medications or as a replacement when SABA medications are not well-tolerated. In addition to SABA and SAMA use, systemic corticosteroid bursts can also be added to SABAs and SAMAs for short term relief depending on the severity of symptom exacerbation (Durham, et al., 2017) .

Long-term symptom relief can be obtained through long-acting beta2 agonists (LABA) medications meant to control inflammation related to chronic asthma and help prevent an asthma attack. LABA medications promote a decrease in symptoms, decreased risk of exacerbations, decreased asthma-related hospitalizations, improved lung function, improved quality of life, and lower risk of asthma-related deaths (Durham, et al., 2017). LABA medications typically last more than 12 hours and include medications such has salmeterol, formoterol, and vilanterol. These medications have similar side effects as SABA medications. Although LABAs are strong bronchodilators, they must not be used as a single therapy. It is recommended that LABAs be used with inhaled corticosteroids (ICS) to decrease the risk of severe exacerbations and death (Durham, et al., 2017).

In addition to SABA and LABA medications, leukotriene receptor antagonists (LTRAs) such has montelukast and zafirlukast can be used to treat chronic, long-term asthma. These medications have a steroid-sparing effect and also work well preventing exercise-induced bronchospasms (Durham, et al., 2017). Lastly, long-acting muscarinic receptor antagonists (LAMAs) and tiotropium can be added to medication therapy when asthma is still uncontrolled even with the use of two or more controller medications.

Nursing Care Plan

Developing a plan of care is of great importance to successfully control asthma and prevent exacerbations. Three important issues that need to be addressed are ineffective airway clearance, impaired gas exchange, and readiness for enhanced health management.

Ineffective Airway Clearance

In an acute phase, this care plan will address ineffective airway clearance related to asthma. Auscultation of breath sounds every two to four hours is necessary to assess for changes in wheezing or crackles. Respiratory patterns should also be monitored to assess for respirations to remain between 12 to 16 breaths per minute. Increased respiratory rate can signal airway secretions. An acute patient should have the head of bed elevated to between 30 and 45 degrees to allow for maximum expansion of the lungs. The patient should be educated regarding deep breathing and controlled coughing to help clear excessive airway secretions. Incentive spirometry can also be used to promote clearance of excessive secretions. Encouraging frequent patient mobilization as tolerated. If the patient is nonmobile, changing positions every two hours can be effective. This is to help mobilize secretions. Administer bronchodilators or inhaled steroids as necessary while monitoring for side effects, such has tachycardia, tremors, and dysrhythmias. Administration of these medications can decrease airway resistance and improve oxygenation (Ackley, Ladwig, & Makic, 2017, pp. 130-135).

Impaired Gas Exchange

A patient in an acute phase of asthma would also suffer from impaired gas exchange. It would be important to monitor respiratory rate, depth, and ease of same. Assess for nasal flaring or use of accessory muscles to monitor for signs of respiratory distress. Auscultate lungs everyone to two hours to monitor for crackles and wheezes and assess for diminished lung sounds or air trapping. Monitor for changes in mental status, confusion, restlessness, or lethargy, as these can be signs of impaired gas exchange. Oxygen saturation should be closely monitored along with possible blood gases to assess the need for supplementation oxygen. Observation of the skin, especially around the mouth, tongue, and oral mucosa, for cyanosis. A bluish coloration can signal underventilated or unventilated alveoli. Position the patient at a 30 to 45 degree angle in bed to promote lung expansion. Administer medications as ordered and assess for efficacy post-administration in a timely manner associated with the onset, peak, and duration of the medication (Ackley, et al., 2017, pp. 404-407).

Readiness for Enhanced Health Management

A patient in a chronic phase of asthma should have readiness or enhanced health management. Promotion of knowledge regarding asthma is critical at this point. Review factors/triggers that need to be avoided and way to do so. This will provide the patient and family with ways to potentially avoid asthma attacks. Discuss and review appropriate medications using teach-back method to ensure the patient has understood the medication information relayed to them. Provide written materials to reinforce teaching so the patient will have something to refer to at home. Ensure an Asthma Action Plan is completed and updated regularly. Remind the patient to refer to the Plan to guide their therapy and warn them when emergency help may be needed (Ackley, et al., 2017, pp. 451-454).

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