XENON RESPIRATORY MONITOR

Descriptions

Xenon is licensed in the UK as an anaesthtic gas for use in ASA I/II patients. The team are currently conducting clinical trials with xenon containing breathing gas mixtures, delivered by a mechanical ventilator, in human neonates who are at moderate or severe risk of brain damage after delivery in poor condition. It is proposed that xenon may reduce this brain damage. We are currently ventilating the neonates by applying a pressure to the airway during inspiration which inflates the lungs, then releasing this to a lower pressure during expiration, allowing the lungs to recoil. A typical pressure swing would be 15cm.H2O during inspiration over 4cm.H2O during expiration.The mechanical ventilator when using the xenon system is not connected to the airway tube (tracheal tube) of the baby as would normally be the case, but is attached to a single use closed circle re-breathing system being used to deliver the xenon. This xenon delivery breathing circuit has a compressible internal volume. Therefore the flow/volume sensor of the commercial ventilator (attached to the Xe circuit, not directly to the baby) will tend to give elevated readings. For example if the ventilator is giving 40ml breaths to the closed circuit breathing system as a driving force, then due to compressibility of the gas within the closed breathing circuit and expansion/contraction of corrugated hoses, the baby may only be getting 30ml breaths. This is acceptable so long as clinicians are aware of this.Currently we are assessing whether the volume of each breath is adequate by using an end-tidal carbon dioxide monitor which reflects the blood carbon dioxide level. If too high, then we need to increase the size of each breath or the breaths given per minute or both. Although we do not therefore have to know the exact breath volume given to the baby, clinicians would find this very desirable as it is a value they are used to knowing and would be very desirable in future large clinical studies and ultimately during clinical use of xenon.A ventilation monitor for use in neonates (and adults with an adult sensor head) when xenon containing breathing gas mixtures are in use. For use in all xenon neuroprotection research and xenon anaesthesia in both neonates and adults.Adult flow sensor specificationsConnections: 15mm ID at patient end, opposite end 15 mm OD.Tapers: ISO 5356-1Dead space when installed: As low as possible but typically 5ml.Tubing (if pneumotachograph based): 2m long with connections to monitor.Measured flow range: 2 – 180 LPM (32 – 3000 ml/s)Added airway resistance: < 2 cmH2O @ 1000ml/sAccuracy: ±5% of reading or 0.5L/min (whichever is greater).Intended for tidal volumes >= 100ml.Neonatal flow sensor specificationsConnections: 15mm ID at patient end, opposite end 15 mm OD.Tapers: ISO 5356-1Dead space when installed: As low as possible but ideally < 1ml.Tubing (if pneumotachograph based): 2m long with connections to monitor.Measured flow range: 0.25 - 40 LPM (4 - 667 ml/s)Added airway resistance: < 1 cmH2O @ 10L/minAccuracy: +- 5% of reading or 0.125L/min (whichever is greater).Operating temperature range: 5°C to 50°CShipping/storage temperature range: -40°C to 70°C