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

Chapter 1: General Principles of Physiology and Pathology

Most emergency medical assessment and treat- ment is based on a few general principles of pathology and physiology. If you can understand these basic human responses to injury and illness, you will be in a much better position to adapt your medical skills and experience to the remote and extreme environment. These principles are funda- mental and will surface frequently in your study of wilderness and rescue medicine. The ideal result is that you will never forget what to do because you will understand what needs to be done. Oxygenation and Perfusion All living tissue must be continuously perfused with oxygenated blood to function normally. For each cell in the body to be adequately oxygenated, a continuous flow of fresh air to the lungs and a continuous flow of blood to the body tissues is required. Anything that interferes with this is a serious problem. The preservation of oxygenation and perfusion is the fundamental goal of emer- gency medical care.

General Principles

Oxygenation and Perfusion

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“Anything that interferes with this is a serious problem.”

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The basic function of the respiratory system is to bring outside air into the alveoli of the lungs where only a thin membrane separates air from blood. This allows oxygen from the air to diffuse into the blood and combine with hemoglobin in red blood cells. Adequate oxygenation of the blood requires adequate respiration. The basic purpose of the circulatory system is to perfuse the lungs with blood in need of oxygen, and to perfuse the rest of the body tissues with the newly oxygenated blood. Adequate perfusion requires that the circulatory system generates enough pressure to force the blood through the capillary beds in body tissues where oxygenation of the cells and removal of carbon dioxide and metabolic waste occurs.