A monitoring apparatus for monitoring a composition of {TAIL ~ a breathing gas mixture} comprising a first gaseous component and {HEAD ~ a second gaseous component}, said monitoring apparatus comprising: 
A monitoring apparatus for monitoring a composition of { TAIL ~ a breathing gas mixture } comprising a first gaseous component and { HEAD ~ a second gaseous component } , said monitoring apparatus comprising :
OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH