Wilderness and Rescue Medicine 8th Edition

1 7

Section I: General Principles

Respiratory rate (R), expressed in breaths per minute, is a direct measurement of respiratory system function but can be difficult to measure accurately. It is more valuable to note the effort involved in respiration. An increased respiratory rate may be a compensatory response to shock, which is a circulatory system problem and not an indication of respiratory distress. Labored and noisy respiration would confirm a respiratory sys- tem problem and true respiratory distress.

The more accurate esophageal or bladder probes are generally not available or practical for field use. Skin color and temperature (S) reflects the perfusion of the body shell. Reduced skin perfu- sion may indicate compensation for loss of blood volume in illness and injury. Or, cool and pale skin might just be part of the normal response to cold weather. Warm, dry, and pink skin is normal. The perfusion status of dark-skinned patients can be assessed by observing the palms and soles and the mucosa of the lips. Oxygen Saturation (O 2 ) measures the percent- age of the blood’s oxygen carrying capacity that is currently in use. At sea level, a healthy circulatory and respiratory systemwill oxygenate to 98–100%. This drops to 90–95% at 3000 meters of elevation. Some chronic respiratory problems will result in an O 2 saturation as low as 85%, which may be normal for that person. Generally, anything below 89% indicates a problem, unless other factors such as altitude are considered. Oxygen saturation is measured in the field with a small device that fits on a finger, toe, or earlobe. Called a pulse oximeter , it measures the color of the blood fromwhich it calculates the percentage of hemoglobin molecules that are combined with oxygen. Some smartphones also have this mea- suring capability. An accurate reading depends on good circulation to the digit being used for measurement. Placing the probe on a cold or ischemic extrem- ity may result in an artificially low oxygen satura- tion reading. The presence of carbon monoxide, which produces a bright red color when combined with hemoglobin, will result an artificially high reading. Fingernail polish has also been shown to effect the device. Consciousness and mental status (C) is a measure of brain function. No special instru- ments are required. Consciousness is described as relating to one of four letters on the AVPU scale: • A is awake, with the patient’s condition further described in terms of mental status using terms like oriented, disoriented, confused, combative, etc.

There are a number of places where arteries lie just under the skin where the pulse can be felt and the rate counted. Temperature (T) refers to the temperature of the body core. This can be quite different from skin temperature, especially when exposed to extremes of heat or cold. The rectum is the most accurate place to measure core temperature in the field. Oral temperatures are certainly more con- venient, but are affected by eating, breathing, and talking and may be lower than core temperature.