## Summary

In study session I you have learnt

• Gases are easy to compress, they expand to fill their containers, and they occupy far more space than the liquids or solids from which they form. Since one of the properties of a gas is compressibility, a gas at a certain volume can be compressed by adding pressure.
• Many of the properties of gases can be measured in different ways. Conversion from one unit of pressure to another is very important. Here is a list of equivalent amounts of pressure: 1 atmosphere (atm) = 14.7 PSI (pounds per square inch) = 760 mm Hg (also known as 1 Torr) = 101.325 KPa (kiloPascals)
• Mathematically Boyle's law can be expressed as P1V1 = P2V2 . Charles' law states that, at constant pressure, the volume of a given mass of gas varies directly with its absolute temperature (T):
• A 'full' cylinder of oxygen on an anesthetic machine contains compressed gaseous oxygen at a pressure of 137 bar. If the cylinder of oxygen empties at constant temperature, the volume of gas contained is related linearly to its pressure.
• Medical gases are pure grade of gas to be used for medical purposes. The medical gases commonly used in operating rooms are oxygen, nitrous oxide, air, and nitrogen. Patients are endangered if medical gas systems, particularly oxygen, malfunction.
• Medical gases are delivered through a piping network from their central supply source to the operating room or from gas cylinder located near to anesthesia machine.
• The tubing is color coded and connects to the anesthesia machine through a non interchangeable diameter-index safety system (DISS) fitting that prevents incorrect hose attachment.
• Anesthesia machines must have an oxygen supply low-pressure sensor that activates a gas whistle or electric alarm sounds when inlet gas pressure drops below a threshold value (usually 20-35 psig). It must be stressed that these safety devices do not protect against other possible causes of hypoxic accidents
• A gas cylinder is a pressure vessel used to store gases at above atmospheric pressure. A gas cylinder has different sizes from A- J. Medical gases are most commonly stored in "H" or "K" cylinders whose inside dimensions are 8 1/2" by 51".
• Compressed gas may be used only when an approved pressure regulation device is installed to control the gas flow from the cylinder.
• The cylinder's valve must be blown clear before a pressure regulation device is installed. This is done by slowly cracking the valve for an instant to get rid of contaminants (such as dirt and dust).
• Gas cylinders are often color coded, but the codes are not standard across different jurisdictions, and sometimes are not regulated. Cylinder color cannot safely be used for positive product identification; cylinders have labels to identify the gas they contain and the label alone should should not be used for positive identification.
• You have to follow standard for a safe practice of using oxygen cylinder.