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  • • Peak flow measurements monitor asthma, in both acute and chronic cases.

    • Peak flow measurements can be used to assess severity, diurnal variation, response to bronchodilators, response to triggers (eg, viral illnesses, allergens), and effect of exercise.

    • Peak flow monitoring is useful at home, in the emergency department, and at the bedside to assess the severity of a patient’s asthma.

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Absolute

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  • • Pneumothorax.

    • Hemoptysis.

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Relative

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  • • Age; patients can usually perform maneuver starting between ages 4 and 5 years.

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  • • Peak flows are highly variable and effort dependent.

    • Measurements can vary from 1 peak flow meter to the next. (It is important to use same meter each time.)

    • Peak flows change as patient gets taller.

    • Diurnal variation occurs—as much as 25–30% in children.

    • Measurement of peak flows is mainly determined by resistance in large airways; therefore, peak flow measurement is insensitive to small airways resistance, which is most often affected in asthma.

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  • • Explain procedure in a developmentally appropriate manner before and during procedure.

    • Coach the patient for optimal effort to ensure acceptable results.

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  • • Patient should be sitting upright or standing with erect posture.

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  • • Return indicator/arrow on peak flow meter to zero.

    • Hold peak flow horizontal.

    • Take a deep full breath in (to total lung capacity).

    • Place mouth on peak flow meter and make a seal with lips.

    • Exhale hard and fast.

    • Read number from indicator/arrow.

    • Repeat 2 more times.

    • Record best of 3 efforts.

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  • • Patients should determine their baseline and personal best peak flow measurement.

    • To obtain baseline, have patient perform maneuver 3 times in morning and 3 times at night for 2 weeks and maintain a record.

    • Personal best is the highest of these values over these 2 weeks.

    • Normal peak flow values are greater than 80% of the personal best, with mild values being 50–80% and critical values < 50% of personal best.

    • Predicted nomograms are also available based on patient height.

    • Response to various triggers and exercise can be defined as a decrease in peak flow of 15%, whereas a positive response to bronchodilator therapy is an increase of 15% in peak flow.

    • Awareness of patient effort dependence and variations assists in making clinical decisions based on peak flow measurements.

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  • • The most significant limitation is that this test is effort dependent.

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  • • Routine review of technique, establishment of new personal best peak flows, and appropriate asthma action plan for alterations in peak flow should be used to maximize the benefit of peak flow use.

Boggs PB, Wheeler D, Washburne WF et al. Peak expiratory ...

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