Some people have pathology of the lung which prevent rapid flow of excess air through the passages, which can lead to lung barotrauma even if the breath is not held during rapid depressurisation. These people should not dive as the risk is unacceptably high. Most commercial or military diving medical examinations will look specifically for signs of this pathology. Diving mask squeeze enclosing the eyes and nose: The main risk is rupture of the capillaries of the eyes and facial skin because of the negative pressure difference between the gas space and blood pressure, or orbital emphysema from higher pressures. This can be avoided by breathing air into the mask through the nose. Goggles covering only the eyes are not suitable for deep diving as they cannot be equalised. Dry suit squeeze. The main risk is skin getting pinched and bruised by folds of the dry suit when squeezed on descent. Most dry suits can be equalised against squeeze via a manually operated valve fed from a low pressure gas supply. Air must be manually injected during the descent to avoid squeeze and is manually or automatically vented on the ascent to maintain buoyancy control. Diving helmet squeeze: Helmet squeeze will occur if the gas supply hose is severed above the diver and the non-return valve at the helmet gas inlet fails or is not fitted. Severity will depend on the hydrostatic pressure difference.
Couvade is a term which was coined by anthropologist E. B. Tylor in 1865 to refer to certain rituals in several cultures that fathers adopt during pregnancy. Couvade can be traced to Ancient Egypt as a "sacred birth custom, of when a child is born, the man experiences the ritual of "labor" in which he takes to his bed, and undergoes periods of fasting and purification, and the observance of certain taboos".The term "couvade" is borrowed from French (where it is derived from the verb couver "to brood, hatch"); the use in the modern sense derives from a misunderstanding of an earlier idiom faire la couvade, which meant "to sit doing nothing. "An example of couvade is that the Cantabri people had a custom in which the father, during or immediately after the birth of a child, took to bed, complained of having labour pains, and was accorded the treatment usually shown to women during pregnancy or after childbirth. Similarly, in Papua New Guinea, fathers built a hut outside the village and mimicked the pains of labour until the baby is born. Similar rituals occur in other cultural groups in Thailand, Russia, China, India and many indigenous groups in the Americas. In some cultures, "sympathetic pregnancy" is attributed to efforts to ward off demons or spirits from the mother or seek favour of supernatural beings for the child. Couvade has been reported by travelers throughout history, including the Greek geographer Strabo (3.4.17).