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Advanced Pathophysiology adapt Asthma
A Introduction to Asthma: - Asthma is a complex, obstructive lung disease with airway inflammation and bronchoconstriction due to intrinsic or extrinsic factors. Airway hyperresponsiveness to various stimuli is a crucial feature that leads to the inflammation and bronchoconstriction experienced by clients living with asthma.
- Asthma has defining characteristics of shortness of breath, chest tightness, and cough that vary over time and in intensity. Asthma affects all ages but is most common in children and younger adults.
- Asthma results in (...). Changes in airflow may cause partial or total airway obstruction, leading to (...) Increased alveolar oxygenation, increased alveolar perfusion, decreased alveolar ventilation Bradycardia, emphysema, hypoxia: Decreased alveolar ventilation Hypoxia
- Which physiological process causes wheezing during an exacerbation of asthma?
- Air passing through the alveoli filled with mucus during inhalation and exhalation
- Air passing through the nose due to partial blockage of the epiglottis
- Air passing through narrowed bronchioles and mucus during exhalation
- Air passing enlarged tonsils into a narrowed trachea during inhalation: - Air passing through narrowed bronchioles and mucus during exhalation
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- Pathophysiology of Asthma: - In asthma, an allergen or irritant exposure causes immune activation, while mast cell degranulation is triggered by immune factors that bind to the allergen or irritant as it enters the airway. Mast cell degranulation releases chemicals and vasoactive mediators. Vasoactive mediators cause vasodilation and increased capillary permeability, while chemotactic mediators result in cellular infiltration.
- With continued exposure to an allergen or irritant, the client experiences airway bronchospasm, acute inflammation, mucus production that accumulates in the lungs, alveoli hyperinflation with consolidation, and eventually epithelial erosion and fibrosis. The outcome is bronchial hyperresponsiveness and partial or total airway obstruction.
- Asthma and Gas Exchange: - As with other obstructive lung diseases, asthma has an underlying gas exchange problem and ventilation-perfusion (V/Q mismatch). Thick mucus, mucosal edema, and bronchospasms obstruct small airways; breathing becomes labored, and expiration is difficult. Hyperventilation sets in as lung receptors respond to airway obstruction and increase lung volume—early hypoxia, then hypoxemia sets in with decreased PaCO2 and increased pH (respiratory alkalosis).
- With ongoing expiratory airflow obstruction, air trapping becomes severe, and breathing in and out becomes difficult. The lungs and thorax become hyperexpanded, and accessory muscles are used for breathing, leading to the following: *decreased tidal volume (TV) *hypoventilation *increased PaCO *respiratory acidosis
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- Intrinsic Asthma: Intrinsic asthma is initiated through stimuli targeting hyperresponsiveness in the airway.
Non-allergic stimuli cause a slightly different variation in the inflammatory process. Intrinsic asthma is commonly diagnosed in adulthood with no elevation in IgE.
- Medications such as aspirin or non-steroidal anti-inflammatory drugs (NSAIDs) cause respiratory and gastrointestinal (GI)
irritation and increase the production of mucosal protective substances in both the GI and respiratory tracts.
- Airborne allergens such as tobacco smoke and pollution cause bronchoconstriction in the lower airways as a protective response.
After prolonged exposure, histamine release and bronchoconstriction continue, leading to acute inflammation and multisystem adverse effects.
- Viral infections acquired through infancy (e.g., respiratory syncytial virus [RSV] and human respiratory virus strain C) can trigger
asthma by stimulating an excessive immune response in children. This leads to a permanent imbalance of immune cells, activating the Th2 cells to stimulate the immune factors and mast cell degranulation.
- Gastroesophageal reflux disease (GERD) is also associated with the development of intrinsic asthma. When the vague nerve,
which controls acid production, is stimulated, acetylcholine is released to increase acid production. The acetylcholine binds to receptors in the respiratory tract, causing bronchial constriction. Examine the image below to learn more about extrinsic and intrinsic asthma. Image Transcript
- Clinical Manifestations of Asthma: - Decreased alertness
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- SOB
- Expiratory wheezing
- Dyspnea and prolonged expiration
- Cough
- Tachypnea
- Report of chest tightness
- Tachycardia
- Pulsus paradoxus
- Status Asthmaticus: Medical Emergency: In severe cases, accessory muscles are used to breathe. Status asthmaticus may result if bronchospasm is not reversed with treatment. A pulsus paradoxus (decrease in systolic blood pressure during inspiration of more than 10 mmHg) may be present. Hypoxia turns to hypoxemia, expiratory flow rates decrease, and ventilation decreases, resulting first in respiratory alkalosis and then acidosis. Acidosis affects multiple systems and, if the body is unable to compensate, then the client will go into multisystem organ failure.
- Early Treatment and Intervention: - Early intervention and targeted treatment are critical when bronchial hyperresponsiveness is present to prevent further airway obstruction and disease progression. Early intervention of airway hyperresponsiveness is clinically significant, as it is associated with a decline in lung function and an increased risk for the
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- Peak Flow Meter: Clients can use a peak flow meter to determine the severity of an asthma attack. It is a
portable device the client uses to see how much air they are exhaling. The results help clients participate in self-care management of the disease and decide whether to use their "rescue" inhaler.
- Asthma Diagnostics: Airflow Obstruction: Asthma differs from other obstructive lung diseases
because the symptoms occur and then subside (an asthma attack or exacerbation) without getting progressively worse. Other obstructive diseases, such as chronic obstructive pulmonary disease (COPD), get worse over time.
- Variability: Variability refers to the fluctuation of lung function over time, where the client may have normal
versus abnormal readings during an exacerbation. Variability occurs with a FEV1/FEV of < 70% or less than the lower limit of normal.
- Reversibility: Reversibility is a key differentiator of asthma. It is defined as a FEV1 that improves by 12% and
200 mL after using a bronchodilator.
- Flow Volume Loop: - During spirometry, a flow volume loop is produced. In expiration, there is a scooping
nature to the flow volume loop. An obstruction can be confirmed by noting that the FEV1/FVC is < 70%.
- After albuterol, as shown in the diagram, the lungs open, allowing more airflow. This indicates a normal flow volume loop. Note
that there is no scooping pattern with the blue line. This indicates reversible airflow obstruction because of measured improvement after the bronchodilator (albuterol) was administered.
- Peak Expiratory Flow Rate: - Another method for determining variable obstruction is through the peak
expiratory flow rate. It is simple and convenient to use by the client in the home setting. You will see values ranging from zero up
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- A client's peak expiratory flow can be predicted by using certain online calculators that use the client's age, height, and gender to determine their personal value. The client is instructed to take the lever down into the neutral or zero position. The client inhales maximally and then forcefully exhales to completion. The client will record three of these values for both morning and evening. Over one week, if these values vary by more than 20%, it is consistent with the variability of obstruction (asthma).
- Asthma Diagnostics: Methacholine Challenge Test: - For a client with clinical manifestations of asthma but normal testing parameters via spirometry, a bronchoprovocation test or methacholine challenge test is indicated. The test is performed in a pulmonary function lab setting and is considered a gold standard in diagnosing asthma.
- Methacholine stimulates airway smooth muscle cells to cause bronchoconstriction. After obtaining a baseline FEV1, methacholine is administered in escalating doses until either the FEV1 drops by 20% or the maximum dose is achieved.
- In the graph showing methacholine challenge test results, the "x" axis is pre-test probability, and the "y" axis is the predicted FEV1. The curved lines are labeled with the dose administered. The value of 100% corresponds to the client's FEV1. The values are plotted after each dose of methacholine is given. The curve will progressively drop where it crosses the 80% mark. This is an important value because it is considered the provocation challenge dose that causes a 20% decrease in FEV1. *If this value is less than 8-16 mg/mL, it is positive for bronchial hyperreactivity. *If the test is negative, asthma can be ruled out.
- Before the challenge test is ordered, the nurse practitioner (NP) must determine if the client is receiving medications that can
10 / exacerbation (i.e., web of causation), clinical management can be complex. For example, a client with asthma contracts the COVID- 19 virus, which can exacerbate the disease. Determining the cause of the COVID-19 virus is challenging for a susceptible client. Client teaching strategies in an action plan help reduce the frequency and severity of the disease, and include, but are not limited to the following:
- Recognize early symptoms.
- Identify and avoid asthma triggers (i.e., intrinsic and extrinsic factors).
- Create and follow an action plan of what to do if an attack does occur; receive education on what is a mild, moderate, and severe reaction. Depending on where they fit within these categories, teach information on its management, including how to adjust drug dosages (e.g., stepwise approach).
- Take medications as prescribed.
- Teach the client when to contact their healthcare provider or seek emergency treatment. For example, noticing a progressive increase in "rescue" inhaler use.
- Get vaccinated to prevent infections that may make asthma worse.
- Participate in regular exercise.
- Age-Related Considerations in Asthma: - With physiological age-related changes, lung function and capacity decrease. In older adults with asthma, this decrease contributes to a greater likelihood of death from an exacerbation of the disease.
11 / According to the Centers for Disease Control and Prevention (CDC, 2021), asthma mortality increases with age. Between 2016 and 2018, the mortality rate among adults was four times higher than children. Where children died at a rate of 2.7 per 1 million, adults died at a rate of 13.2 per 1 million, and those over 65 died at 29.5 per 1 million.
- Comorbidities (e.g., cardiac, respiratory, and renal problems) can aggravate management treatment plans for clients with asthma. Medications taken for other diseases can make asthma symptoms worse. For example, beta-adrenergic receptor antagonists (e.g., beta- blockers) used to treat hypertension have the opposite effect on smooth muscle in the lungs. These medications block airway β2- receptors, causing severe and sometimes fatal bronchoconstriction. These medications are contraindicated in clients with asthma.
