Incorrect use of peak flow meters: are you observing your patients?

BACKGROUND

Monitoring peak expiratory flow (PEF) values is one option as part of asthma action plans per national guidelines. PEF assessment is also recommended in emergency department and hospitalized patients. Incorrect use of peak flow meters (PFM) has obvious implications for appropriate decisions by patients and clinicians.

METHODS

We searched the English literature via PubMed and SCOPUS using the following search terms: PEF maneuver; incorrect use of PFM. When pertinent articles were found, we assessed publications cited in those papers. All studies related to incorrect use of PFM in patients with asthma were included.

RESULTS

Nine studies have reported errors in performing the PEF maneuver, including three pediatric and six adult studies. Errors were found at most steps of the maneuver, and inability to perform all steps correctly was common in these investigations. Examples of errors included failure to inhale fully or give maximum effort on exhalation, accelerating air with the tongue and buccal musculature, and performing only one attempt versus three. Gender differences in correct use of PFM are suggested by three adult studies. One study described falsifying PEF values by manipulating the PFM indicator, and another investigation assessed the PEF maneuver in two positions in bed versus the correct posture of standing.

CONCLUSION

Many pediatric and adult patients do not use PFM correctly. Clinicians should regularly observe patients use PFM to detect errors and help ensure correct use and accurate PEF measurements.

A comparison of peak expiratory flow measured from forced vital capacity and peak flow meter manoeuvres in healthy volunteers

BACKGROUND:

Spirometry measures the mechanical function of lungs, chest wall and respiratory muscles by assessing the total volume of air exhaled from total lung capacity to residual volume. Spirometry and peak flow measurements have usually been carried out on separate equipments using different expiratory maneuvers.

AIMS:

The present study was carried out to determine whether there is a significant difference between peak expiratory flow (PEF) derived from a short sharp exhalation (PEF maneuver) and that derived from a full forced vital capacity (FVC) maneuver in healthy volunteers.

SETTINGS:

A medical college and tertiary level hospital.

MATERIALS AND METHODS:

The present study was carried out during the period from January 2006 to July 2006. The study included 80 healthy volunteers with no coexisting illnesses, who were in the 15-45 years age group and belonging to either sex. They were asked to perform two sets of PEF and FVC maneuvers using the same turbine spirometer; the order was randomly assigned.

STATISTICAL ANALYSIS:

The difference between PEF obtained from a peak flow maneuver (PEFPF) and that obtained from a forced vital capacity maneuver (PEFVC) in healthy volunteers was analyzed separately for males and females, as well as for both groups combined, and statistical significance of its correlations with study data parameters was analyzed.

RESULTS:

The difference between PEF obtained from a peak flow maneuver (PEFPF) and that obtained from a forced vital capacity maneuver (PEFVC) was statistically significant (P < 0.001) in males and in females separately and also for both groups combined. PEFPF (517.25 ± 83.22 liters/min) was significantly greater than PEFVC (511.09 ± 83.54 liters/min), as found on combined group mean analysis. However, the difference was small (6.16 + 7.09 liters/min).

CONCLUSIONS:

FVC maneuver can be used over spirometers to detect the PEF; and on follow-up subsequently, the same maneuver should be used to derive PEF. If we are using a peak flow maneuver subsequently, corrections are required to compensate for the difference due to the different maneuver.