Oxygen assessment and provision Anne McGown Consultant Royal Berkshire Hospital Mar 2008

Old system Oxygen concentrators for long term oxygen therapy –some assessment done by chest clinics, but prescription done by GPs Cylinders for prn use No provision of ambulatory oxygen

New system Divided according to oxygen requirement, and then company decide most economical system Long term oxygen therapy Ambulatory Short burst Emergency - indications yet to be defined

Therapeutic role of oxygen Only one of a number of effective treatments for chronic lung disease Need to have the right diagnosis Need to optimise other treatments Has defined indications and is not a universal panacea.

Oxygen for breathlessness No evidence that oxygen treats breathlessness in patients who are not hypoxic either at rest or on exercise. Why should it?

Oxygen dissociation curve If already on the flat bit no benefit from increased pO2 (If on the steep bit even low concentrations can help.)

Long term oxygen therapy Continuous oxygen for at least 15hours a day Survival benefit in persistently hypoxaemic patient Mainly patients with COPD, other chronic lung disease with hypoxia. Criteria for prescription based only on blood gas measurements, not symptoms.

Who should be assessed? (COPD) All patients with severe airflow obstruction (FEV1 < 30% predicted) patients with cyanosis patients with polycythaemia patients with peripheral oedema patients with a raised JVP

Pulse oximetry Can be used to screen who to refer for LTOT assessment Non-invasive way to monitor percentage of haemoglobin that is saturated with oxygen. Works because oxygenated haemoglobin is a different colour from deoxygenated haemoglobin. Selects out pulsatile flow. Accurate above a saturation of 70%.

Pulse oximetry - practical points Not accurate if signal poor - always need to check signal –probe position –hypovolaemia/shock –peripheral vasoconstriction - cold –shivering –nail varnish

Checking the signal

Assessment for LTOT Pulse oximetry saturation <92% Arterial blood gases on 2 occasions 3 weeks apart when stable (ie not during exacerbation) Arterial puncture, traditionally performed by doctors in hospitals; we have a hospital protocol for nurse training and 4 nurses currently trained in clinic. Capillary sampling, easier, less reliable, tends to underestimate oxygen values

LTOT prescription Strict criteria for prescription - pO2 of <7.3 or 7.3 to 8 with signs of cor pulmonale. Do HOOF if fit the criteria. Oxygen concentrator 15hours a day, 2l/min Warn re smoking Monitor compliance, sats, peripheral oedema Evidence that it doesn’t help if not that bad.

The HOOF and the HOCF

Small print Copies to –PCT –Trust clinical lead for oxygen –GP –patients notes –oxygen company

Oxygen concentrators Concentrate oxygen out of the air (by absorbing other gases) Plug into the wall, with tubing wired round the house. Need a cylinder for power cuts etc.

Ambulatory oxygen Provision of oxygen during exercise and activities of daily living. Shown to be effective in increasing exercise capacity and reducing breathlessness in patients with exercise arterial oxygen desaturation (fall of more than 4% or to below 90%).

Ambulatory assessment New assessment procedure 6 minute walk, check desaturation 6 minute walk on oxygen, measure distance, desaturation correction and breathlessness on visual analogue scale. Time consuming, but less technically demanding than blood gases Only do assessment if reasonably mobile and motivated to carry the oxygen.

Ambulatory assessment Grade 1 oxygen requirements –on LTOT, walk nowhere, may want portable cylinder for their wheelchair but don’t need assessment Grade 2 oxygen requirements –active LTOT - need assessment to see what flow rate corrects desaturation Grade 3 oxygen requirements –exertional desaturation no LTOT

Ambulatory referrals Probably should offer assessment to all severe COPD patients if active enough. ? Also some moderate COPD patients who are SOBOE interstitial lung disease + SOBOE new service so we don’t really know nationally who will end up using it compliance issues.

Short burst oxygen Prn cylinder patients no assessment necessary to prescribe short burst (no clear evidence of benefit) All new patients being considered for short burst oxygen should be referred for ambulatory assessment if mobile and LTOT assessment if hypoxic.

Compliance New system should allow better compliance/usage monitoring and removal of equipment if not used. Inappropriate short burst prescription should be reduced.

Flight assessment