So, a descent from the surface to 10 metres (33 feet) underwater results in a doubling of the pressure on the diver. This pressure change will reduce the volume of a flexible gas-filled space by half. Boyles law describes the relationship between the volume of the gas space and the pressure in the gas.Barotraumas of descent are caused by preventing the free change of volume of the gas in a closed space in contact with the diver, resulting in a pressure difference between the tissues and the gas space, and the unbalanced force due to this pressure difference causes deformation of the tissues resulting in cell rupture.Barotraumas of ascent are also caused when the free change of volume of the gas in a closed space in contact with the diver is prevented. In this case the pressure difference causes a resultant tension in the surrounding tissues which exceeds their tensile strength. Use of a hyperbaric chamber
Patients undergoing hyperbaric oxygen therapy must equalize their ears to avoid barotrauma. High risk of otic barotrauma is associated with unconscious patients. Rapid decompression of a pressurised artificial environment
Explosive decompression of a hyperbaric environment can produce severe barotrauma, followed by severe decompression bubble formation and other related injury. The Byford Dolphin incident is an example. Rapid uncontrolled decomression from caissons, airlocks, pressurised aircraft, spacecraft, and pressure suits can have similar effects of decompression barotrauma. Rapid pressurisation of an artificial environment
Collapse of a pressure resistant structure such as a submarine, submersible, or atmospheric diving suit can cause rapid compression barotrauma.
These reactions take place primarily in the kidney and pancreas. The clinical manifestations of AGAT deficiency are caused by the decreased amounts of creatine produced. Diagnosis
AGAT deficiency can be suspected from clinical findings, although there is significant phenotypic overlap with the most common presenting symptoms of intellectual disability and muscle weakness. Laboratory testing of plasma and urine will show decreased levels of creatine and guanidinoacetate. Non-specific elevations of metabolites on urine testing that are normalized to creatinine may appear falsely elevated. Magnetic resonance spectroscopy (MRS) of the brain will also show an absence of creatine, which is normally present. This finding is not specific to AGAT deficiency, it can be observed in all three cerebral creatine deficiencies. The combination of biochemical testing and MRS findings can be strongly suggestive of AGAT deficiency. Confirmation would most often be done with molecular testing of GATM. Identification of biallelic pathogenic variants in GATM would be confirmation of a diagnosis of AGAT deficiency. Uncertain findings on molecular testing may be able to be confirmed by enzyme assays, or by measuring creatine uptake in fibroblasts. Prenatal testing for AGAT deficiency can be performed on chorionic villi samples if the causative pathogenic variants in the family are known. Treatment
The main focus of treatment for AGAT deficiency is supplementation of creatine, with the goal of replenishing cerebral creatine to normal levels. This is done with oral creatine supplementation. Treatment is most effective if it is started early in life, before symptoms are apparent.