Respiratory Pathologies:
Asthma:
Asthma is a reactive airway disease. This means that its symptoms are the result of a bodily reaction to either extrinsic or intrinsic factors. Extrinsic factors include environmental irritants and allergens, while intrinsic factors would include things like a stress response or inappropriate inflammatory reaction.
The disease itself generally develops in childhood, and is associated with extrinsic factors, although it can develop in adolescence as well. Lifestyle factors such as smoking or working with environmental irritants can also irritate an underlying asthma that may have been largely asymptomatic for years.
Asthma is characterized by a symptom triad of dyspnea, wheeze, and cough that occur in exacerbations and remissions. The mechanism behind the disease is actually a triad as well, and is the result of:
Constriction of the bronchioles
Inflammation of the lower airways
Increased mucous production by goblet cells
Management of asthma typically involves addressing inflammation through the long term use of corticosteroids, and treatment of exacerbations with beta-2 agonists.
EMS Management depends largely on the severity of the exacerbation. In severe exacerbations, where the patient presents with a silent chest or apnea, intramuscular epinephrine 1:1000 is administered to trigger immediate dilation of the airways and reduction of inflammation. Ventilatory assistance is also indicated in these patients as they are not breathing effectively on their own. In mild to moderate exacerbations, Salbutamol/Albuterol is indicated, and is generally followed up with a corticosteroid such as Dexamethosone. Many patients will have taken their own inhalers prior to arrival and will likely present with only mild dyspnea.
COPD:
COPD consists of 2 diseases, however they generally occur concurrently to some degree.
Chronic Bronchitis occurs when frequent exposure to an environmental irritant (usually cigarette smoke) leads to hyperplasia of goblet cells in the smaller airways. This causes overproduction of thick, sticky, mucous. The result is air trapping, and difficulty ventilating. Patients subsequently have difficulty with gas exchange at the alveolar level, due to dead spacing, and end up retaining higher than normal levels of CO2 in the bloodstream. The CB patient is often called a blue bloater, because they typically have chronic peripheral cyanosis in areas like the nail beds, and are often of larger body mass due to reduced exercise tolerance.
Emphysema occurs when environmental irritants (again typically cigarette smoke) lead to irritation and inflammation of the lower airways. The inflammatory response leads to proliferation of alveolar macrophages and inflammatory mediators in the lung tissue, and subsequent destruction of the alveolar septa. The septa collapse, and alveoli themselves form clumps, or blebs, with reduced surface area for gas exchange. The result is, trapping of stagnant air in hyperinflated alveoli.
Both disease processes tend to occur, to some degree, in tandem. COPD patients have chronic elevation of CO2 in the bloodstream, and generally function normally with oxygen saturations from 88-92%.
Management of COPD generally involves the use of beta-2 agonists, corticosteroids, and anti-cholinergic medications. Home oxygen is used in many cases as these patients have difficulty with alveolar gas exchange.
COPD is typically relatively stable over a period of time, however it is progressive, and can present with exacerbations in the emergency setting. Due to reduced ability to compensate in the setting of increased exercise, febrile illness, or the presence of allergens, a COPD patient can present with acute exacerbations of their symptoms. EMS treatment is similar to that of asthma, in that our aim is to initially ensure adequate ventilation, and assist if needed. We also treat with salbutamol, and corticosteroids to alleviate brochoconstriction, and we utilize CPAP/BIPAP to splint open collapsed airways. The goal is to support the COPD patient in ventilating effectively, as this is their core problem.
Anaphylaxis:
While not strictly a respiratory problem, anaphylaxis typically occurs with some degree of airway compromise, and is typically grouped into this category. Anaphylaxis, or anaphylactic shock, occurs when exposure to an allergen leads to an inappropriate, systemic, inflammatory response. In a normal allergic reaction, a substance to which the body is sensitized triggers a localized release of inflammatory mediators, and immune cells, causing a reaction. This reaction is dependant on the body system affected. Commonly, things like cat dander, or pollens cause rhinitis, itchy eyes, or local skin reactions. Anaphylaxis is different. In an anaphylactic reaction, the release of inflammatory mediators is systemic and affects multiple organs and body systems. This leads to widespread inflammation and vasodilation. Ultimately the major concerns here are bronchospasm, airway obstruction, and distributive shock.
In order to be considered an anaphylactic reaction, there must be 2 or more body systems involved. A thorough assessment of the patient is necessary, however, if you suspect anaphylaxis it is better to treat for it than to wait for further progress of the reaction.
Many patients with a known anaphylactic sensitivity will carry an epipen. Epinephrine stimulates both alpha and beta adrenergic receptors, leading to increased heart rate, vasoconstriction, and bronchodilation. This effectively treats the primary symptoms of anaphylaxis, however, the effects of epinephrine are short lived, and a rebound anaphylactic reaction can still occur, as epinephrine does not address the leukotrines and underlying inflammatory cascade occuring in the body. An antihistamine, such as Diphenhydramine, needs to be co-administered with epinephrine in order to stop the progress of this inflammatory process. In EMS we treat with intramuscular epinephrine 1:1000, followed by IV or IM Diphenhydramine. We can also use Salbutamol/Albuterol to treat ongoing bronchoconstriction, and Zofran for any nausea or vomiting that may also be present. IV cannulation should be performed if able as the patient is in a shock state, and fluid administration may be required at some point.
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