Fresh gas flow
Encyclopedia
Fresh gas flow refers to the mixture of medical gases and volatile anaesthetic agents which is produced by an anaesthetic machine
. The flow rate and composition of the fresh gas flow is determined by the anaesthetist.
Typically the fresh gas flow emerges from the common gas outlet, a specific outlet on the anaesthetic machine to which the breathing attachment is then connected.
Some older forms of breathing attachment, such as the Magill attachment, require high fresh gas flows (e.g. 7 litres/min) to prevent the patient from rebreathing their own expired carbon dioxide. More modern systems, e.g. the circle breathing attachment, use soda lime
to absorb carbon dioxide
, so that expired gas becomes suitable to re-use. With a very efficient circle system, the fresh gas flow may be reduced to the patient's minimum oxygen
requirements (e.g. 250ml/min), plus a little volatile.
Anaesthetic machine
The anaesthetic machine is used by anaesthesiologists and nurse anaesthetists to support the administration of anaesthesia...
. The flow rate and composition of the fresh gas flow is determined by the anaesthetist.
Typically the fresh gas flow emerges from the common gas outlet, a specific outlet on the anaesthetic machine to which the breathing attachment is then connected.
Some older forms of breathing attachment, such as the Magill attachment, require high fresh gas flows (e.g. 7 litres/min) to prevent the patient from rebreathing their own expired carbon dioxide. More modern systems, e.g. the circle breathing attachment, use soda lime
Soda lime
Soda lime is a mixture of chemicals, used in granular form in closed breathing environments, such as general anaesthesia, submarines, rebreathers and recompression chambers, to remove carbon dioxide from breathing gases to prevent CO2 retention and carbon dioxide poisoning.It is made by treating...
to absorb carbon dioxide
Carbon dioxide
Carbon dioxide is a naturally occurring chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom...
, so that expired gas becomes suitable to re-use. With a very efficient circle system, the fresh gas flow may be reduced to the patient's minimum oxygen
Oxygen
Oxygen is the element with atomic number 8 and represented by the symbol O. Its name derives from the Greek roots ὀξύς and -γενής , because at the time of naming, it was mistakenly thought that all acids required oxygen in their composition...
requirements (e.g. 250ml/min), plus a little volatile.
See also
- Anaesthetic vaporiserAnaesthetic vaporiserAn anaesthetic vaporiser is a device generally attached to an anaesthetic machine which delivers a given concentration of a volatile anaesthetic agent.The design of these devices takes account of varying*ambient temperature*fresh gas flow...
- Anaesthetic machineAnaesthetic machineThe anaesthetic machine is used by anaesthesiologists and nurse anaesthetists to support the administration of anaesthesia...
- Soda limeSoda limeSoda lime is a mixture of chemicals, used in granular form in closed breathing environments, such as general anaesthesia, submarines, rebreathers and recompression chambers, to remove carbon dioxide from breathing gases to prevent CO2 retention and carbon dioxide poisoning.It is made by treating...