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

Sea level SaO2 Oxygen

>95% Not required

92-95% no lungdisease

Not required

92-95% andlung disease

Hypoxicchallenge

<92% or homeLTOT

In-flight oxygen