wherever shoes rub. If you have blisters and they burst, leave the skin in place and apply a clean dressing. Carrying an extra pair of socks in your survival vest is suggested. At least once per day, clean, dry, and massage your feet to ensure adequate circulation. Remember, trench foot is caused by prolonged exposure to wet, usually cold, conditions; but it may be developed in the tropics. If symptoms of trench foot appear-that is, tingling, numbness, swelling, blisters, or sores—pay extra attention to your feet and give them proper care. Control of Bleeding The control of heavy bleeding is extremely important under all conditions, but it is of even greater importance in a survival situation since transfusions are not possible. When breathing ceases in conjunction with heavy bleeding, you must first take action to initiate breathing, then to stop the bleeding. NOTE: Never apply a tourniquet unless that is the only way to stop bleeding from an extremity. Restoration of Breathing When breathing signs are absent, the most common cause is blockage of the airway. If normal first-aid procedures fail to clear the airway and restore breathing, you have one alternate procedure. This procedure is called a cricothyroidotomy and can be performed suc- cessfully by unskilled nonmedical personnel. To perform a cricothyroidotomy, proceed as follows: 1. Locate the thyroid cartilage (Adam’s apple), which is the largest bony protrusion in the center line of the neck. 2. Locate the cricoid cartilage (the first circular ridge below the Adam’s apple). The point of incision is the depression immediately above the cricoid cartilage. 3. Using a sterile surgical razor blade, if available, or any other cutting instrument in an emergency, make a lateral incision one-fourth to one-half of an inch wide and approximately one-fourth of an inch deep into the trachea. 4. Insert the lower half of a ball-point pen barrel or any similar rigid tube into the incision one-half to three-fourths of an inch or until movement of air is felt or heard. 5. Secure the tube with tape if it is to be left in place for an extended period of time or if the victim is to be transported. Control of Pain Control of pain accompanying disease or injury is extremely difficult because pain cannot be measured. The severity of pain accompanying any disease or injury is relative to the individual’s ability to withstand or cope with that pain. Although some individuals can tolerate a great deal of pain, others cannot. Psychological injury m a y  a l t e r  a n  i n d i v i d u a l ’ s  p a i n  t h r e s h o l d. Regardless of this difficulty, every effort should be made to control or eliminate pain, not only because of its adverse effect on morale, but also because it contributes to shock and makes a survivor less capable of performing other essen- tial tasks. The ideal method for pain reduction is to eliminate its cause. Since this is not always possible, the following methods are recom- mended: . Reduce movement of the painful area. Immobilize the wounded area in a position that p r o v i d e s  m a x i m u m  c o m f o r t  a n d  e a s e  of maintenance. Use splints and bandages. . Apply a clean dressing that will protect the wound from the air and from painful contacts with objects in the environment. l Apply hot or cold compresses. Try both hot and cold compresses to determine which offers the most relief. . A common injury sustained by downed aircrew members is broken teeth. This results in extreme pain because the nerves are exposed to air. To ease the pain, take the following steps: . Cover broken teeth with pine or other tree saps or any waxy substance. . Drink tea made from the boiled inner bark of a willow tree. The bark contains an active substance called salicylate, which is an aspirin substitute. Aspirin will prevent blood from clotting. Pain-relieving drugs should be given sparingly, and then only to relieve true pain, not to soothe the victim’s apprehension. The only ready-made pain reliever available to aircrew members is the aspirin located in the SRU-31/P Medical Packet #1. Control of Shock Shock is frequently the most serious conse- quence of an injury. You should become familiar 5-38