Ebullism is the formation of gas bubbles in bodily fluids due to reduced environmental pressure, for example at high altitude. It occurs because a system of liquid and gas at equilibrium will see a net conversion of liquid to gas as pressure lowers; for example, liquids reach their boiling point at lower temperatures when the pressure on them is lowered. Symptoms
Symptoms of ebullism include bubbles in the membranes of the mouth and eyes, swelling of the skin, and bubbles in the blood. Blood circulation and breathing may be impaired or stopped. The brain tissue may be starved of oxygen because of blockage of arteries, and the lungs may swell and hemorrhage. Death results unless recompression is rapid enough to reduce the bubbles before tissue damage occurs. In 1960, Joseph Kittinger experienced localised ebullism during a 31 kilometres (19 mi) ascent in a helium-driven gondola. His right-hand glove failed to pressurise and his hand expanded to roughly twice its normal volume  accompanied by disabling pain. His hand took about three hours to recover after his return to the ground. Tissue samples from the remains of the crew of Space Shuttle STS-107 Columbia revealed evidence of ebullism. Given the level of tissue damage, the crew could not have regained consciousness even with re-pressurization. Mechanism
In the atmospheric pressure present at sea level, water boils at 100 °C (212 °F). At an altitude of 63,000 feet (19,000 m), it boils at only 37 °C (99 °F), the normal body temperature of humans.
Specific radiographic signs of NEC are associated with specific Bells stages of the disease:
Bells stage 1 (suspected disease):
Mild systemic disease (apnea, lethargy, slowed heart rate, temperature instability)
Mild intestinal signs (abdominal distention, increased gastric residuals, bloody stools)
Nonspecific or normal radiological signs
Bells stage 2 (definite disease):
Mild to moderate systemic signs
Additional intestinal signs (absent bowel sounds, abdominal tenderness)
Specific radiologic signs (pneumatosis intestinalis or portal venous gas)
Laboratory changes (metabolic acidosis, too few platelets in the bloodstream)
Bells stage 3 (advanced disease):
Severe systemic illness (low blood pressure)
Additional intestinal signs (striking abdominal distention, peritonitis)
Severe radiologic signs (pneumoperitoneum)
Additional laboratory changes (metabolic and respiratory acidosis, disseminated intravascular coagulation)Ultrasonography has proven to be useful, as it may detect signs and complications of NEC before they are evident on radiographs, specifically in cases that involve a paucity of bowel gas, a gasless abdomen, or a sentinel loop. Diagnosis is ultimately made in 5–10% of very-low-birth-weight infants (<1,500g). Diagnosis of NEC is more challenging in premature infants, due to inexplicit symptoms and radiographic signs. The most preterm infant is at highest risk of developing NEC. Prevention
Prevention includes the use of breast milk and probiotics. A 2012 policy by the American Academy of Pediatrics recommended feeding preterm infants human milk, finding "significant short- and long-term beneficial effects," including reducing the rate of NEC by a factor of one-half to three-quarters.Small amounts of oral feeds of human milk starting as soon as possible, while the infant is being primarily fed intravenously, primes the immature gut to mature and become ready to receive greater intake by mouth.