Wilderness and Rescue Medicine 7th Edition Jeffrey Isaac, PA-C and David E. Johnson, MD

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Section II: Critical Body Systems

upward flow of mucus is generated by tiny hair- like structures called cilia. You are continuously swallowing the resulting mixture, usually without thinking about it. The chest wall and diaphragm act like bellows to draw the air in and out. The rate and depth of breathing is under nervous system control. In a healthy person, the brain regulates breathing by measuring the carbon dioxide concentration of the blood. Too much carbon dioxide in the blood causes an increase in acidity. The brain responds by increasing the rate and depth of respiration to “blow off” the carbon dioxide until normal acidity is reestablished. Conversely, alkalosis (decreased acidity) is corrected by decreasing the rate and depth of respiration to retain carbon dioxide.

Respiratory Problems Respiratory distress is the generic term for dif- ficulty breathing. Symptoms include increased respiratory rate, increased respiratory effort, anx- iety, wheezing, and coughing. One of the most obvious signs of respiratory distress is the use of accessory muscles. Normally, a person at rest uses only the dia- phragm to breathe. When work is increased, oxy- gen demand increases, and the respiratory system will use muscles in the chest, shoulders, and neck to increase the depth of respiration. You would expect to see this as a normal response in some- one who is running or hiking hard; you would not expect to see it in someone sitting still. Accessory muscle use at rest indicates respiratory distress. A more subtle sign is shortness of breath on exertion. This patient has a compromised respira- tory system that can supply enough oxygen only if the demand is low. Sitting and resting are fine, but any level of increased exertion, such as hiking, causes severe shortness of breath. This symptom is often an early sign of respiratory distress due to pneumonia, high altitude pulmonary edema, or asthma.

Breathing

General Principles

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Inspiration

Expiration

“…the brain regulates breathing by measuring the pH (acidity) of the blood. This is actually a reflection of the amount carbon dioxide dissolved in the blood plasma.”

Respiratory Failure

General Principles

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This acid–base regulation system is very precise and results in a smooth and regular respiratory pattern. However, in some disease conditions, such as emphysema, the amount of carbon diox- ide in the blood is high all the time because the lower airway is chronically constricted and can- not ventilate properly. Conversely, in a metabolic condition like diabetic ketoacidosis, the patient may be breathing fast to blow off carbon diox- ide to keep the pH under control even though the carbon dioxide concentration is already low. Conditions like these can result in respiratory regulation that is much less precise, more easily upset, and results in a more irregular pattern.

Respiratory Distress: • Difficulty breathing, speaks in short sentences. • A on AVPU, anxious Respiratory Failure: • Able to speak only one or two words at a time. • A, lethargic to V, or P on AVPU Respiratory Arrest: • No breathing

Low Risk

High Risk

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Regardless of the cause of respiratory distress, the condition will eventually progress to respira- tory failure if not corrected. Respiratory failure means that the system cannot supply enough oxy- gen to the blood to keep the brain functioning normally. The primary distinction is made by the decay in mental status and level of consciousness.