The clinician must be able to calculate how much oxygen a patient is receiving. In order to standardize this amount, atmospheres absolute (ATA) are used. This can be calculated from the percentage of oxygen in the gas mixture (usually 100% in Oxygen Therapy; 21% if using air) and multiplied by the pressure. The pressure is expressed in feet of seawater , which is the pressure experienced if one were descending to that depth while in seawater. Depth and pressure can be measured in many ways. Some common conversions are 1 atmosphere = 33 feet of seawater = 10 meters of sea water = 14.7 pounds per square inch (psi) = 1.01 bar.
ແພດຈະຕ້ອງສາມາດຄິດໄລ່ອົກຊີເຈນທີ່ຄົນເຈັບໄດ້ຮັບ. ເພື່ອມາດຕະຖານຈໍານວນນີ້, atmospheres absolute (ATA) ຖືກນໍາໃຊ້. ນີ້ສາມາດຖືກຄິດໄລ່ຈາກອັດຕາສ່ວນຂອງອົກຊີໃນການປະສົມອາຍແກັສ (ມັກ 100% ໃນການປິ່ນປົວດ້ວຍອົກຊີ; 21% ຖ້າໃຊ້ອາກາດ) ແລະຄູນດ້ວຍຄວາມກົດດັນ. ຄວາມກົດດັນແມ່ນສະແດງຢູ່ໃນຕີນຂອງນ້ໍາທະເລ, ເຊິ່ງເປັນຄວາມກົດດັນທີ່ມີປະສົບການຖ້າຫາກວ່າຫນຶ່ງໄດ້ຫຼຸດລົງໄປໃນຄວາມເລິກໃນຂະນະທີ່ຢູ່ໃນນ້ໍາທະເລ. ຄວາມເລິກແລະຄວາມກົດດັນສາມາດໄດ້ຮັບການວັດແທກໃນຫຼາຍວິທີ. ການປ່ຽນແປງບາງຢ່າງແມ່ນບັນຍາກາດ 1 = ນ້ໍາທະເລ 33 ຂອງນ້ໍາ = ນ້ໍາທະເລ 10 ແມັດ = 14.7 ປອນຕໍ່ຕາລາງນິ້ວ (psi) = 1.01 ແຖບ.