Skin is composed of two main interwoven layers of dermis, on the inside, and epidermis, on the outside. The epidermis, which is composed of five sub units, possesses the most important sign of our identity. Each thin layer is arranged in a way to carry out different tasks. A significant amount of elasticity and flexibility is provided to skin via these five layers. These layers can glide on each other slightly and can also be compressed under pressure. They are compressed when we sit on a hard surface. This situation can be similar to the compression of the spring in a click pen, or the suspension of a vehicle under a load. They regain their previous state upon termination of the pressure, like standing up. This elasticity is crucial for skin’s integrity.
The thin construct of our skin contains sweat glands that are embedded in the fibrous connective tissue. There are sensory receptors, hair roots, and hair muscles connected to them, and also loose nerve endings, and a network of capillary vessels. Free nerve endings are created to specialize in various functions so as to sense hot, cold, pressure, and pain. Likewise, the continuation of blood flow relies on very intricate calculations that are hard to explain. When blood vessels arrive at the skin, they are dispersed like a net in the form of capillaries.
The blood pressure of the arteries located at lower section of the skin is higher than the pressure of pulmonary veins. If pressure is applied to skin for a long duration from outside, the pressure in the pulmonary veins builds up and regional blood flow is disrupted. Therefore oxygen, glucose, and other nutritional substances cannot be delivered to these areas; along with inhibition of waste product removal, it leads to a nutritional abnormality in the tissue.
Sensory cells within our skin detect and report nutritional abnormalities of tissue to our brain via various chemical substances (like acetylcholine, bradykinin, and histamine). Thus we change our position consciously or subconsciously with the intervention of our brain to avoid the danger of a nutritional abnormality, and therefore the area regains normal circulation. In this stage, the process is still reversible; however, should the pressure continue, skin cells will start to die from, from the outside in. These systems do work well in healthy persons but in cases of stroke or coma, the intervention system does not work.
This critical picture can be understood better with an example. Just like roads need to be used in order to carry goods and remove trash, the transportation of minerals, vitamins, and many other life saving substances to the distant parts of the body and removal of waste products requires blood vessels to remain open. This must continue in a perfect balance without any interruption throughout our lives.
If a pressure ulcer occurs, it is like being exposed to external dangers in a house if a door or window breaks. It is like a free entrance visa is granted to germs that were blocked. Our back and pointy areas, like, thighs knees, heels, and shoulders are under more pressure, and therefore at more risk when we lie down. Two to six hours of pressure to one of these areas is enough time to disrupt skin integrity. Our daily sleep requirement is around 6-8 hours, therefore we need to switch positions a couple of times during our sleep. Therefore we face this risk everyday in our sleep; however, thanks to the perfectly functioning protective systems, without noticing during our sleep, our position is changed and this dangerous situation is avoided. Intensive care doctors and staff know better what a great blessing that is are since intensive care patients are mostly unable to move. Despite the use of many preventive efforts, like turning the patients in certain periods or the use of air beds, pressure ulcers still occur and a significant portion of patients die of the microbial infections caused by these wounds.
The story of sleepers
“The Seven Sleepers” story in the Christian tradition is retold in the Qur’an as “the People of the Cave.” The story is about a group of young believers who took refuge in a cave fleeing the oppression of the pagan Roman emperor. Both traditions narrate that they fell asleep in the cave, where they stayed asleep for hundreds of years. The Qur’anic account, however, mentions that they were made to change position during their centuries-long sleep: “You would have thought them awake though they were asleep. We caused them to turn over to the right and the left…” (18:18). It is an interesting nuance that they were made to change position, for it sounds rather irrelevant to the rest of the story. However, with the medical conditions of our skin that were explained above, this nuance makes perfect sense as advice to us on how we should treat patients who are unable to move.