Dysbarism refers to medical conditions resulting from changes in ambient pressure. Various activities are associated with pressure changes. Underwater diving is the most frequently cited example, but pressure changes also affect people who work in other pressurized environments (for example, caisson workers), and people who move between different altitudes. Ambient pressure
Ambient pressure is the pressure in the water around the diver (or the air, with caisson workers etc.). As a diver descends, the ambient pressure increases. At 10 meters (33 feet) in salt water, it is twice the normal pressure than that at the surface. At 40 meters (a common recommended limit for recreational diving) it is 5 times the pressure than at sea level. Pressure decreases as we rise above sea level, but less dramatically. At 3000 feet altitude (almost 1000 meters), the ambient pressure is almost 90% of sea level pressure. Ambient pressure does not drop to 50% of sea level pressure until 20,000 feet or 6,000 meters altitude. Effects of pressure on the body
Direct effects on tissues
This is not of practical importance, because the body is mostly composed of barely compressible materials such as water. People often wonder whether scuba divers feel their body being crushed by the pressure, but divers would have to reach depths of thousands of feet before their flesh began to suffer significant compression. Gas filled spaces
Gas is very compressible. Humans have many air spaces: sinuses, middle ears, gas in our bowels, cavities in our teeth, and largest of all, our lungs.
In younger women, they are more common, thus in patients under the age of 21, 60% of ovarian tumors are of the germ-cell type, and up to one-third are malignant. In males, GCTs of the testis occur typically after puberty and are malignant (testicular cancer). In neonates, infants, and children younger than 4 years, most are sacrococcygeal teratomas.Males with Klinefelter syndrome have a 50 times greater risk of GSTs. In these persons, GSTs usually contain nonseminomatous elements, present at an earlier age, and seldom are gonadal in location. Treatment
Women with benign GCTs such as mature teratomas (dermoid cysts) are cured by ovarian cystectomy or oophorectomy. In general, all patients with malignant GCTs have the same staging surgery that is done for epithelial ovarian cancer. If the patient is in her reproductive years, an alternative is unilateral salpingoophorectomy, while the uterus, the ovary, and the fallopian tube on the opposite side can be left behind. This is not an option when the cancer is in both ovaries. If the patient has finished having children, the surgery involves complete staging, including salpingoophorectomy on both sides, as well as hysterectomy.Patients with germ-cell cancer often need to be treated with combination chemotherapy for at least three cycles, but female patients with early-stage disease may not require this treatment. The chemotherapy regimen most commonly used in GCTs is called PEB (or BEP), and consists of bleomycin, etoposide, and a platinum-based antineoplastic (cisplatin).