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

Chapter 5: The Respiratory System

One of the three critical systems, the respiratory system is responsible for oxygenating the blood as it perfuses the capillaries in the lungs. Respiration involves a complex arrangement of muscle, bone, airway tubes, semipermeable membranes, and the adjacent capillaries and larger blood vessels. Respiratory failure occurs when the respiratory system is unable to supply enough air to the alveoli of the lungs to adequately oxygenate the blood or remove the accumulated carbon diox- ide. Respiratory failure is a serious critical system problem requiring immediate and aggressive life- saving treatment. Caring for someone in respira- tory distress or failure is the scariest thing you will ever do in emergency medicine. Structure and Function The structure of the respiratory system is designed to bring air into the alveoli where only a thin semi- permeable membrane separates air from blood. The combined surface area of the millions of alveoli in the lungs would cover a tennis court, offering an extensive membrane through which oxygen can diffuse to bind with the hemoglobin in the red blood cells and for carbon dioxide to diffuse passively from the blood plasma into the air to be exhaled. The efficiency with which the system works is measured as oxygen saturation.

Respiratory System

General Principles

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Structure: • Upper Airway • Lower Airway • Alveoli • Chest Wall and Diaphragm • Neuro Drive Function: • Oxygenation of the Blood • Regulation of Blood pH Problem: • Respiratory Failure

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A healthy person at sea level would measure 95 to 100% on a pulse oximeter, indicating that the oxygen-carrying capacity of the blood is met. In the presence of respiratory problems, oxygen saturation will fall, indicating less efficient respira- tion. It is also possible to measure the efficiency of the respiratory system by assessing mental status and skin color. Like the circulatory system, the structure of the respiratory system can be described in basic terms for field use: upper airway, lower airway, alveoli, chest wall and diaphragm, and nervous system control. The upper and lower airways consist of the semi-rigid tubes that conduct air into the alveoli. These passages are lined with mucous membranes designed to remove contaminants and bacteria from the system continuously. The