One of the advantages of a full-face diving mask is prevention of regulator loss in the event of a seizure. Mouthpiece retaining straps are a relatively inexpensive alternative with a similar but less effective function. As there is an increased risk of central nervous system oxygen toxicity on deep dives, long dives and dives where oxygen-rich breathing gases are used, divers are taught to calculate a maximum operating depth for oxygen-rich breathing gases, and cylinders containing such mixtures should be clearly marked with that depth.The risk of seizure appears to be a function of dose – a cumulative combination of partial pressure and duration. The threshold for oxygen partial pressure below which seizures never occur has not been established, and may depend on many variables, some of them personal. the risk to a specific person can vary considerably depending on individual sensitivity, level of exercise, and carbon dioxide retention, which is influenced by work of breathing.In some diver training courses for these types of diving, divers are taught to plan and monitor what is called the oxygen clock of their dives. This is a notional alarm clock, which ticks more quickly at increased oxygen pressure and is set to activate at the maximum single exposure limit recommended in the National Oceanic and Atmospheric Administration Diving Manual.
Micromastia (also called hypomastia, breast aplasia, breast hypoplasia, or mammary hypoplasia) is a medical term describing the postpubertal underdevelopment of a womans breast tissue. Just as it is impossible to define normal breast size, there is no objective definition of micromastia. Breast development is commonly asymmetric and one or both breasts may be small. This condition may be a congenital defect associated with underlying abnormalities of the pectoral muscle (as in Polands syndrome), related to trauma (typically surgery or radiotherapy) or it may be a more subjective aesthetic description. Self perceived micromastia involves a discrepancy between a persons body image, and her internalized images of appropriate or desirable breast size and shape. Societal ideals over breast size vary over time, but there exist many conceived ideas involving breasts and sexual attractiveness and identity across different cultures. Causes
Micromastia can be congenital or acquired disorder and may be unilateral or bilateral. Congenital causes include ulnar–mammary syndrome (caused by mutations in the TBX3 gene), Poland syndrome, Turner syndrome, and congenital adrenal hyperplasia. There is also a case report of familial hypoplasia of the nipples and athelia associated with mammary hypoplasia that was described in a father and his daughters. Acquired causes of micromastia include irradiation in infancy and childhood and surgical removal of prepubertal breast bud. Treatment
The procedure to remedy micromastia is breast enlargement, most commonly augmentation mammoplasty using breast implants. Other techniques available involve using muscle flap-based reconstructive surgery techniques (latissimus dorsi and rectus abdominis muscles), microsurgical reconstruction, or fat grafting.