Asthma 哮喘 (Reading & Sharing)

Asthma is a chronic reactive airway disorder that is a long term pulmonary disease with airflow resistance causing episodic airway obstruction from bronchospasms, increased mucus secretion, and mucosal edema. In people with asthma these airways are chronically inflamed making them hypersensitive to triggers.

Current statistics show:

• Approximately 25 million people in America have asthma. 1 in 13 people.
• 7.6% of adults, 8,4% of children have asthma.
• More women, 9.7% ….than men, 5.4% have asthma.
• More boys than girls have asthma.
• More children than adults have asthma.
• African-Americans are three times as likely to be hospitalized and to die from asthma.
• 13.4% of African-American children compared to 7.4% of white children have asthma.

(CDC Medical Review, 2018)

 

The most common clinical manifestations include cough, dyspnea, and wheezing (Eckman et al (2013). Asthma is increased with individuals who are exposed to environmental allergens that causes hypersensitivity and inflammation of the respiratory system which could have triggered his or her Asthma attacks like the tobacco smoke, dust, mold, cockroach droppings, pollen, fragrances, urban dust, animal dander, mold, and even the common cold.

Asthma exacerbation is mediated by exposure to indoor allergens.  Evidence shows that not all allergen exposure affects children equally.  Cockroach exposure results in severe asthma outcomes and is a major contributor to asthma morbidity.  The mechanism by which cockroach allergen leads to morbidity is not well understood, exposure has been shown to increase proliferative T-cell responses and to be highly potent, inducing an IgE response at considerably lower levels of exposure than dust mite and cat allergen.  Allergen avoidance is one of the principles of asthma management.  Up to 85% of homes of children with asthma in the inner city have detectable levels of cockroach allergen in the dust and roughly half have very high levels (Rabito, Carlson, He, Werthmann, & Schal, 2017).  Identifying and mitigating asthma triggers are vital components for preventing frequent pediatric asthma exacerbations and recurrent emergency room (ER) visits (Shah, Dooley, Shelef, & Patel, 2018).

Furthermore, the anxiety experienced from bronchospasms worsen the condition that requires immediate attention (Braun et al,2017).

When someone with asthma is exposed to a trigger, the smooth rings of muscle contract and become narrow. At this same time, the trigger worsens inflammation which causes the mucosal lining to swell and secrete more mucous. Under normal conditions, this mucous is used to trap the particles, such as mold or dust, but during an asthma attack the mucous blocks the narrowed airway, making it even harder to exchange air. This process leads to the symptoms of asthma, the smooth muscle constriction causes chest tightness, the increase mucous and inflammation can cause coughing, wheezing happens because as the airway constricts the air makes a whistling noise as it passes through the narrowing airways.

During physiological events of an asthma attack the tightening of muscles around the airways are known as bronchospasm. A bronchospasm often happens rapidly and is caused by a trigger or exercise. They often cause a cough not to expel mucous but more because it is caused by an involuntary muscle spasm. During a bronchospasm air is trapped within the alveoli related to the constricting bronchiole. Most common causes of bronchospasm are due to excessive mucus production, inflammation, illness, irritants (triggers), and stress.

Pharmacological treatment of asthma includes treatment of acute asthma exacerbations with quick-relief medications, and prevention of exacerbations with long-term control medications.

Quick relief medications include:

• Short acting beta agonists (Bronchodilators known as AccuNeb, ProAir or Ventalin) act within minutes -as the rescue inhaler used during an attack that treat symptoms immediately by acting on the sympathetic nervous system, and last for several hours. Can be given with a nebulizer or with a metered dose inhaler (MDI) and spacer.  Risks include tachycardia, hypokalemia, and hyperglycemia. Albuterol is the gold standard- helps relax the constricted muscles and allow the airways to widen, which will allow more air to travel to the alveoli. With the dilation of the bronchial airways the medication stimulates the beta-2 receptors on the smooth muscle cells, which cause the muscles to relax.
• Corticosteriods (anti-inflammatory agents) Relieves airway inflammation caused by acute asthma attacks within minutes. May be given Intravenously or orally. Prednisone or methylprednisolone are the gold standards (CDC medical Review, 2018).

Long-term control medications include:

• Inhaled corticosteroids, the most beneficial management medication for asthma (anti-inflammatory agents) Used to calm inflamed airways and abate persistent asthma symptoms. They include Flovent, Q-var, Pulmicort, Asthmanex.  ICS is considered a preventative medication that needs to be taken every day and can take up to two weeks to be effective. ICS reduces airway sensitivity and inflammation by stabilizing mast cells and not allowing any further inflammatory mediators to be released (Marsh, 2017). ICS is the only medication that can effectively suppress the characteristics of inflammation in the asthmatic airways. Overtime, the use of ICS will not heal asthma but make the attacks better managed.

• Leukotriene modifiers (anti-inflammatory agent) Used to calm inflamed airways. Given orally.  Prevents asthma symptoms for up to 24 hours. Singular is the gold standard.  Others include Zyflo, and Accolate.

• Combination inhalers (inhaled corticosteroids and a long action Beta agonist, LABA) LABA should only be used in combination with an inhaled corticosteroid. Should only be used when asthma is not well controlled with other therapies.  Most common are Advair, Symbicort, Breo and Dulera

(Ortiz-Alverez, O. and Mikroglanaskis, A., 2012).

 

The optimal asthma treatment depends on a number of factors, including the child’s age, the severity and frequency of asthma attacks, and the ability to properly use the prescribed medications.  Successful management of asthma requires the parent and child to monitor their asthma regularly.  This is primarily done by recording the frequency and severity of asthma symptoms and the use of the bronchodilator albuterol (Sawicki & Haver, 2018). It is important to note that the above pharmacological therapies must be evaluated using the same assessment tools used to rate severity of disease. This should be done within a comprehensive written action plan that is shared with the patient and family. In so doing, one can:

• verify how well medications are working,
• adjust medications when needed,
• verify if medications are subduing triggering agents and response to same,
• identify when a health care provider needs to be called (Mayo Clinic, 2018).

Severe asthma attacks can be significant to the chances of respiratory distress failure and respiratory acidosis. During an asthma attack the inflammation can make it harder to exhale than inhale. This can lead to hyperinflation, which is when there is a trapping of air inside the lungs causing the body to work harder to move air. The consequences of hyperinflation include increase work of breathing, impaired gas exchange and respiratory muscle fatigue. This leads to reduced oxygen delivery to the body’s organs and tissues (Papiris, 2012). Along with hypoxemia, carbon dioxide is unable to eliminate appropriately. Another reason for physical fatigue with prolonged asthma attacks could be the generation of intrinsic positive end- expiratory pressure (PEEPi) which can cause large negative intrathoracic pressure that effects the right atrial filling and leads to poor cardiac output (Stanley & Tunnicliffe, 2008). During respiratory fatigue the body becomes hypercapnia, which is the retention of carbon dioxide. CO2 is a by-product of cell metabolism and is carried through the blood through the venous system to the lungs, where it is exhaled. When there is an accumulation of CO2 (hypercapnia), the abundance of CO2 dissolved into the blood stream by diffusing across the alveolar-capillary membrane. The body will compensate by increasing the respiration rate (hyperventilation), increase blood pressure, heart rate elevates, and increase kidney bicarbonate production. The body will become exhausted and inadequate alveolar ventilation will occur. When the CO2 becomes excessive, the blood stream will become as acidosis, which means the pH has become less that 7.35. During acidosis, the body’s blood vessels constrict in the extremities, all while the arteries to the vital organ dilate. If the body begins to tire the compensatory mechanism fail causing depression to the central nervous system. This can be presented by increase lethargy, confusion and memory loss (Butterworth, 2015).

 Therefore, clinically, treatment should be initiated as soon as possible to ensure a more positive outcome:

• Treat hypoxia with supplemental O₂ by face mask until SpO₂ is >94%.
• Administer short-acting B₂-agonists, Albuterol (the gold standard) by metered-dose inhaler and spacer.
• P.O. or intravenous corticosteroids dependent on severity. Prednisone or methylprednisolone are common.
• Assess response to treatment
• Consider other modalities of treatment if necessary.

 

Management: Prevention measures to control factors contributing to asthma are aimed at limiting exposure to irritants and factors that increase asthma symptoms and precipitate asthma exacerbation. A careful history is needed to identify all the contributory factors, such as environmental factors (stress that the importance of elimination of dust, cockroaches, mold, and etc.) and as well as gastroesophageal reflux after milk drinking before bedtime. Relaxation techniques and controlled breathing are necessary in patient and family teaching and often help to allay the panic and anxiety that aggravate breathing difficulties. Inhaled B2-adrenergic agonists may be used in the treatment of acute attack, and anti-inflammatory agents sodium cromolyn and nedocromil may be used to prevent an asthmatic attack. (Grossman & Porth, 2014, p. 971- 972).

Resources: The National Asthma Education and Prevention Program (NAEPP) and the Global Initiatives for Asthma (GINA) are organizations that empower care providers with tools to help manage Asthma by accomplishing the following actions: 1) selecting initial therapies, 2) systematically assessing patient outcomes, and 3) adjusting therapies based on individual response to medications which appear below (Meghdadpour et al,2018).

Braun,C.,A.,&Anderson C.,M.(2017) Applied Pathophysiology : a Conceptual Approach      to the Mechanisms of Disease.(3^rd Edition) Baltimore: Wolters Kluwer.

CDC Medical Review, 2018, Living with Asthma.

Eckman, M., & Share, D. (2013). Pathophysiology Made Incredibly Easy!. Philadelphia: LWW.

Grossman, S. C. & Porth, C. M. (2014). Porth’s pathophysiology: Concepts of altered health stats. (9th ed.). Wolters Kluwer/ Lippincott Williams & Wilkins

Irazuzta, J. E., & Chiriboga, N. (2017). Magnesium sulfate infusion for acute asthma in the emergency department. Jornal De Pediatria, 93 Suppl 119-25. doi:10.1016/j.jped.2017.06.002

Meghdadpour, S., & Lugogo, N. L. (2018). Medication Regimens for Managing Stable Asthma. Respiratory Care, 63(6), 759-772. doi:10.4187/respcare.05957

Ortiz-Alverez, O., and Mikroglanaskis, A., 2012.  Managing the Paediatric Patient with an Acute Asthma Exacerbation. Paediatr Child Health. 2012. 17(5): 250-256.

Rabito, F. A., Carlson, J. C., He, H., Werthmann, D., & Schal, C. (2017). A single intervention for cockroach control reduces cockroach exposure and asthma morbidity in children. The Journal Of Allergy And Clinical Immunology, 140(2), 565-570.

Shah, A. Y., Dooley, D., Shelef, D. Q., & Patel, S. J. (2018). Improving Asthma Outcomes in Children: From the Emergency Department and Into the Community. Clinical Pediatric Emergency Medicine, 19(1), 92. doi:10.1016/j.cpem.2018.02.013

Stanley, D., & Tunnicliffe, W. (2008). Management of life-threatening asthma in

adults. Continuing Education in Anaesthesia Critical Care & Pain, 8(3), 95-99. doi:10.1093/bjaceaccp/mkn012

Sawicki, G., & Haver, K. (2018). Patient education: Asthma treatment in children (Beyond the Basics). Retrieved from https://www.uptodate.com/contents/asthma-treatment-in-children-beyond-the-basics

Zahran, H. S., Bailey, C. M., Damon, S. A., Garbe, P. L., & Breysse, P. N. (2018). Vital Signs: Asthma in Children – United States, 2001-2016. MMWR: Morbidity & Mortality Weekly Report, 67(5), 149-155. doi:10.15585/mmwr.mm6705e1