WHAT DOES PEAK FLOW METER MEASURE?

• Measures Peak Expiratory Flow Rate during forced maneuver
• Does not measure lung volumes. Obstruction in the airways will decrease the flow of air that can be removed with force from the lungs.

ROLE OF PEAK FLOW METER IN PRACTICE

• To diagnose Asthma
• To grade the severity of Asthma
• Useful follow up tool for Asthma
• To identify impending exacerbations
• To identify triggers
• To diagnose Occupational Asthma

HOW TO MEASURE PEFR

Using peak flow is as simple as taking a deep breath and blowing out a candle.

Blow fast!!

• Person is asked to blow as hard as possible from a position of maximal inspiration.
• PEF measurement is effort dependent, hence patient need to be coached

STEPS

1) Place INDICATOR at the base of the numbered
2) Scale
3) Fix new MOUTH-PIECE to Peak Flow Meter
4) Take a DEEEEP breath
5) Place PFM in your mouth and seal your lips
6) Blow out as HARD as FAST as you can
7) Note down the number you get from the scale
8) REPEAT Above Steps 2 more time
9) Note down the HIGHEST of the three values Obtained.

ESTABLISHING ‘PERSONAL BEST’ PFR

• Record PFR twice a day during monitoring period of 2-3 weeks
• On both occasions record PFR at least 3 times.
• Note the Highest Number of that day.
• Personal Best is the highest measurement achieved when patient is free from signs and symptoms.

DIURNAL VARIABILITY

Highest PFR-Lowest PFR
PEF Variability = ----------------------------------X 100
Highest PFR Reading
Example:-
400-350
PEF Variability = ------------- X 100 = 12.5%
400
Normal Diurnal Variability< 20%

MEASURE REVERSIBILITY WITH SALBUTAMOL 400mcg

• Baseline PEFR
• Inhaled Salbutamol 400 mcg
• Wait 15 mins
• Post BD improvement > 20% suggests reversible airway disease, likely asthma

MEASURE DIURNAL VARIABILITY > 20% in Asthma

Highest PFR- Lowest PFR
PEF Variability = ----------------------------------X 100
Highest PFR Reading
0
50
100
150
200
6:00 AM 6:00 PM 6:00 AM

Peak flow readings are often classified into 3 zones of measurement according to the American Lung Association;[9] green, yellow, and red. Doctors and health practitioners can develop an asthma management plan based on the green-yellow-red zones.

ROLE OF PEAK FLOW METER IN ASTHMA

ASSESSING SEVERITY

Intermittent PEFR >80%
Variability <20%

Mild Persistent PEFR >80%
Variability 20-30%

Moderate persistent PEFR 60-80%
Variability >30%

Severe Persistent PEFR <60%
Variability >30%

References:

http://www.uptodate.com/contents/how-to-use-a-peak-flow-meter-beyond-the-basics

http://en.wikipedia.org/wiki/Peak_expiratory_flow