Oxygen assessment and provision

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Oxygen assessment and provision

• Anne McGown
• Consultant
• Royal Berkshire Hospital
• Mar 2008

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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

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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

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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.

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Oxygen for breathlessness

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

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Oxygen dissociation curve

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

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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.

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Who should be assessed? (COPD)

• All patients with severe airflow obstruction
  (FEV1 lt 30 predicted)
• patients with cyanosis
• patients with polycythaemia
• patients with peripheral oedema
• patients with a raised JVP

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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.

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Pulse oximetry - practical points

• Not accurate if signal poor - always need to
  check signal
• probe position
• hypovolaemia/shock
• peripheral vasoconstriction - cold
• shivering
• nail varnish

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Checking the signal
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Assessment for LTOT

• Pulse oximetry saturation lt92
• 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

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LTOT prescription

• Strict criteria for prescription - pO2 of lt7.3 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 doesnt help if not that bad.

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The HOOF and the HOCF
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Small print

• Copies to
• PCT
• Trust clinical lead for oxygen
• GP
• patients notes
• oxygen company

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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.

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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).

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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.

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Ambulatory assessment

• Grade 1 oxygen requirements
• on LTOT, walk nowhere, may want portable cylinder
  for their wheelchair but dont 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

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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 dont really know nationally
  who will end up using it
• compliance issues.

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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.

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Compliance

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

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Flight assessment