Peak Flow W

PEAK FLOW ●

What is Peak Flow?

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What equipment do we use?

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How do we get valid results?

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What does it tell us?

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Are there limitations?

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When is it useful?

PEAK FLOW Definition:It is the maximum flow achievable from a forced expiration starting at a full inspiration with an open glottis ref:: Guidelines for the measurement of respiratory function. Respiratory Medicine (1994) 88, 165 - 194

PEAK FLOW ●

Hadorn 1942 ●

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Aneroid

Wright & McKerrow ●

Wright meter

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Mini Wright 1978

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Many others 1976 -

1959

PEAK FLOW Available on prescription

BNF March 1999

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Ferraris Pocketmeter

£6.42

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Mini Wright

£6.74

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Vitalograph

£6.65

PEAK FLOW Causes of reduced peak flow ●

Larynx • tumour, oedema.

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Trachea • tumour, goitre, strictures, relapsing polychondritis.

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Bronchi • tumour, foreign body, asthma, COPD, bronchiectasis.

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Lung parenchyma • tumour

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Chest wall • ankylosing spondylitis, neuromuscular disease.

PEAK FLOW ‘Normal’ ●

Normal lung function

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Asthma

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ILD

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Mild COAD

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Asymptomatic smoker

PEAK FLOW

Pitfalls in measurement ●

Poor effort • confusion, weakness, lack of motivation, lack of co-ordination

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Errors in use of mouthpiece • Leaks, facial palsy, obstruction by tongue /dentures

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Obstruction of cursor or air vents • by fingers

Inadequate rest between attempts ● Deliberate falsification ●

PEAK FLOW Diagnosis (Asthma) ●

Diurnal variation

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Bronchodilator reversibility

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Exercise test

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Steroid trial

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Occupational testing

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Monitoring (Asthma)

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Care plans – Decide when to add or stop medication – Decide when to seek emergency help

Bronchodilator reversibility test Patients Peak flow

Predicted Peak flow

Standard dose of bronchodilator given(200 µg salbutamol or 500 µg Bricanyl) Wait 10 - 15 minutes Post bronchodilator Peak flow

Change % change

= best post PEF - best pre PEF =(change/best pre) x 100

Exercise test Patients demographic details Time

PEF l/min

Predicted PEF

0

6 minutes exercise +5 +10 +15 +20

Post bronchodilator PEF

Steroid trial 30 mg oral prednisolone daily 400 PEF l/min 300 200

100

1

7

14 Days

21

28

PEAK FLOW ●

Cleaning – Manufacturers instructions ● ●

Wash in detergent Milton

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Dishwasher

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Glutaldehyde

– Do not take apart

PEAK FLOW ●

Calibration ●

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Very difficult to calibrate flow accurately

Quality control ●

Reference values for ‘normal’ staff