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17 minute read
Asthma is a respiratory disease that affects a large amount of the population. This section will review the anatomy and physiology that leads to this disease and some of the resulting signs and symptoms that you may observe in the field. It will also review the basics of EMT level management and treatment of this common disease.
Anatomy and Physiology
Asthma is a disease of the smaller airways (Bronchi and bronchioles) that the lungs use to move air from the trachea to the alveoli. Asthma is both an acute and chronic disease, over time the walls of the airways thicken due to a chronic allergic response to inhaled particles. When certain stimuli occur (allergens, cold air, exercise) the walls of those narrow airways further constrict leading to respiratory obstruction. This acute constriction is caused by the release of "histamine" an inflammatory chemical that the body over-produces in patients with asthma.
As a bonus, the thickening of the airways due to the chronic allergic response also increases the secretion of mucus, further increasing the obstruction.
This obstruction is known as "bronchoconstriction" and mainly occurs in the cartilage-free bronchioles that are made of smooth muscle. It is important to know that the "Sympathetic Beta Receptors" in these muscles control bronchoconstriction. If they are not stimulated, the airways have a tendency to collapse.
This collapse varies in severity depending upon the individual patient's disease, leading to the wide variety in symptoms seen in this condition.
Signs and Symptoms
Asthma has a wide variety of presentations, but they can be grouped into mild, severe, and life-threatening. The universal sign of small airway constriction is wheezing, high pitched whistling sounds heard in the lungs, mainly with expiration (during which the airways normally narrow).
The signs of mild asthma are often limited to wheezing, in rare cases, tachypnea may be present.
The symptoms of mild asthma may be entirely absent or may present as mild discomfort or mild shortness of breath that is tolerable at rest.
The sign that differentiates severe asthma from mild asthma is the presence of "accessory muscle use" which is the use of the neck, intercostal, pectoral, and arm muscles to assist in taking a breath. These patients are also universally tachypneic and might have a normal SPO2%. These patients may "tripod-position" or lean over and place their hands on a table or on their knees to assist with breathing.
The symptoms of severe asthma almost universally include shortness of breath, sweating, and chest discomfort. Severe anxiety, confusion, and headache may be present in some patients.
The sign that asthma is becoming life-threatening is when the above-mentioned accessory muscle use begins to disappear and the respiratory rate begins to return to normal despite severe wheezing and potential changes in mental status. This is a sign of decompensation, a state of exhaustion from the work of breathing in which the patient no longer has the energy to maintain the elevated respiratory rate they require.
Keep in mind that the CO2 level in the blood increases before oxygenation drops, a patient may be close to death even with a normal pulse ox reading.
At this stage of asthma symptoms are unreliable, often patients may cease complaining of shortness of breath as mental status declines. Confusion often sets in and more dramatic changes in mental status such as unresponsiveness are often seen.
The best treatment of asthma is prevention, doctors will prescribe inhalers and oral medications to control the disease, asking how well patients adhere to these medication schedules can be important. In the EMS setting only the "short-acting inhalers and nebulizers" matter, sometimes called "rescue inhalers." The generic name for these medications are albuterol and ipratropium; patients will be given these medications in the form of an inhaler they take when they have symptoms.
The EMS treatment for asthma focuses around supporting oxygenation and giving agents to help open the small airways.
Mild asthma should be treated if it causing symptoms that are distressing to the patient or different from a patient's usual asthma symptoms. Provide oxygen by nasal cannula and inhaled beta-agonists (albuterol), these often come in inhalers, it is appropriate to use the patient's own medication if available.
In some cases, medical command may recommend the use of "Duo-Nebs," a combination of albuterol and ipratropium that is inhaled by the patient over a 30 minute time period. Patients may or may not require transport following the resolution of symptoms, although it is important to remind them that these medications are short-acting and they may have a recurrence of symptoms within hours.
Severe asthma should always be treated with oxygen and Duo-Nebs as above. These patients will need to be transported to a higher level of care, since severe asthma is an asthma exacerbation ("asthma attack") and requires medical treatment.
If a patient's status does not improve following duo-neb administration carefully monitor their mental status and respiratory rate while in transport, as acute decrease in either likely represents a transition to life-threatening asthma. Transport in a position of comfort for their breathing.
The management of life-threatening asthma at the EMT level is focused around placing the patient on non-rebreather with nebulized Duo-Nebs as above, obtaining IV access, and arranging ALS intercept for likely intubation. Be prepared to provide positive pressure ventilation via bag-valve-mask to any patients that are becoming drowsy and developing a decreased respiratory rate.
These patients should be placed on cardiac monitors due to a significant risk of hypoxic cardiac arrest.
Pearls and Pitfalls
- Asthma goes from mild to severe when accessory muscle use develops
- Always watch patient's respiratory rates, a tachypneic patient that begins to slow to normal respiratory rates is getting sicker, not better.
- Don't interrupt high flow oxygen therapy in severe patients to use a nebulizer, there are versions that attach to the non-rebreather mask.
- The pulse ox reading does not correlate with a patient's status, asthma severity is based on the clinical exam.