Peak Expiratory Flow Meter Research Articles

Effect of Altitude on Hand-held Peak Flowmeters

To quantify the effect of altitude on the operational characteristics of hand-held peak flowmeters. Altitude simulation within a hypobaric chamber combined with five constant simulated peak flows delivered from a computerized pump were used to test commercially available peak flowmeters. F.G. Hall Hyperbaric/Hypobaric facilities located at Duke University School of Medicine. Two each of nine models of commercially available hand-held peak flowmeters and a volume spirometer were tested at six simulated altitudes (100, 500, 1,000, 1,500, 2,000, and 3,000 m) using five target peak flows. Each peak flow was injected into each meter twice. Forward stepwise regression was used to check for nonlinear relationships between altitude and peak expiratory flowmeter readings. Linear regression equations were fit to the data at each target flow across altitude. Effect of absolute peak flow was tested by analysis of covariance. For these altitudes, linear relationships were found between altitude and measured peak flow. For all meters tested, the average decrease in peak flow ranged from -8.7% at the lowest target flow (123 L/min) to -6.5% at the highest target flow (702 L/min) for each 100 mm Hg decrease in barometric pressure (PB). Individual meters ranged from -12.3% at the lowest target flow to -4.4% at the highest target flow for 100 mm Hg decrease in PB. The spirometer had no significant changes associated with changes in PB. In all cases, the magnitude of the altitude effect, measured by percent change, decreased with increasing peak flow. Peak expiratory flowmeters underread PEF as a function of both increasing altitude and increasing target peak flow.

The performance of Mini Wright peak flow meters after prolonged use

The accuracy of 84 new and 35 old Mini Wright peak flow meters were tested using a servo-controlled pump system. The 95% confidence limits for flow measurement across the range of the new meters was between ± 151 min −1 at the lower end of the range and ± 281 min −1 at the top of the range. The readings for 22 (63%) of the old meters (age range 1–13 yr) were within these 95% confidence limits. For the remaining 13 old meters (age range 1–13 yr) whose readings were not within these limits, there were 11 meters with readings falling below and two meters with readings above these limits. Twelve of these old meters were washed and retested and there was no significant change in their readings. Twenty of the new meters were retested after 1 yr of continuous use and their readings were significantly higher with a median value of 51 min −1 across the range, although only two of these 20 meters had readings outside the 95% confidence limits set from the 84 new meters. It is concluded that whilst Mini Wright meters aged up to 14 yr can give readings which are as good as new meters, some meters demonstrate significant changes in readings after only 1 yr and washing did not correct this change. It is recommended that clinicians prescribing peak expiratory flow (PEF) meters should be responsible for checking the patient's meter as well as their PEF readings at clinic visits.

Frequency response of portable PEF meters.

Peak expiratory flow (PEF) is a dynamic parameter and therefore requires a measuring device with a high-frequency response. This study evaluated the frequency-response characteristics of eight commercially available PEF meters, using simulated forced-expiratory maneuvers with a computer-controlled mechanical pump. Three different PEF levels were used (200, 400, and 600 L/min) at six levels of harmonic-frequency content similar to those observed in human subjects. For waveforms with higher frequency content (at the high end or above the physiologic range), the Assess, Vitalograph, Pocket Peak, and Spir-O-Flow PEF meters all overread PEF (greater than 15% difference from target values) at all three PEF levels. These results suggest that the frequency response of PEF meters is an important consideration in the selection of such meters and should be included in device requirements. The current practice of using various levels of American Thoracic Society (ATS) waveform 24 with its low-frequency content may not adequately evaluate the frequency characteristics of PEF meters. An upper range (5% of the fundamental frequency) of 12 Hz, within the range observed in normal subjects, appears to be more practical than an upper limit of 20 Hz.

Standard flow-time waveforms for testing of PEF meters.

The American Thoracic Society (ATS) has recommended the use of 24 volume-time waveforms for the testing of spirometers. Although these waveforms include values of peak expiratory flow (PEF), they were not originally intended to test PEF meters, but, rather, volume parameters for spirometers. In addition, the practice of using ATS volume-time Waveform 24 with varying multiplying factors does not provide the range of flow-time waveform shapes (rise times) needed to evaluate PEF meters. Accordingly, we have developed a set of 26 flow-time waveforms specifically selected to evaluate PEF meters. PEF and other flow parameters (rise time and time to PEF) can be directly measured from these flow-time waveforms. When PEF determined directly from the flow-time curve was compared with PEF determined indirectly from a volume-time curve (ATS-recommended algorithm with an 80 ms time segment), as much as a 10.7% difference between the two methods was observed using a waveform with a fast rise time. In contrast, there was very little difference between the various methods of deriving PEF for waveforms with slower rise times. These 26 flow-time waveforms provide a means of defining PEF for the testing of software algorithms and the testing of PEF meters with computer-driven mechanical pumps.

Comparing MiniWright and Spirometer Measurements of Peak Expiratory Flow

The accuracy and instrument variability of the MiniWright (Clement Clarke) peak expiratory flow (PEF) meter was determined with 6 of the 24 American Thoracic Society's (ATS) standard waveforms using a mechanical pump. Both room air and air heated to 37 degrees C and saturated with water vapor were used. In addition, MiniWright-determined PEF measurements were compared with those obtained using a dry rolling-seal spirometer (Ohio No. 822; Ohio Medical Products; Madison, Wis) from 75 subjects on 2 different days. The MiniWright average coefficient of variation within a waveform was found to be 2.8%. Results using heated and humidified air (body temperature, ambient pressure, and saturated with water: body conditions) were 2.5% lower than those obtained using room air. Comparisons with mechanically simulated PEF and with spirometry-determined peak flow in 75 human subjects showed that MiniWright meters over-estimated flows at lower flow rates and slightly under-estimated flows at higher flow rates. These results suggest that the new "mechanical PEF" MiniWright scale should be used instead of the "traditional" MiniWright scale.

A field method for sampling benzene in end-exhaled air.

A simple and reliable field method is presented for sampling and analysis of benzene in end-exhaled air. The sample is collected directly on an adsorbent tube while the subject exhales through a sampling device consisting of a modified peak expiratory flow meter. To ensure sampling of end-exhaled air, the temperature of the breath is monitored during expiration. The analytes subsequently are thermally desorbed and analyzed by gas chromatography. No sample preparation before analysis is needed, and therefore sample loss is minimized, shipping is easy, storage is possible, and clean up is unnecessary. All these steps have been major problems in earlier methods for breath analysis. The presented method has been applied to the monitoring of benzene. The separation of benzene from other components of exhaled air was good and the detection limit low (0.5 microgram/m3), and therefore benzene could be monitored in occupationally nonexposed nonsmokers. No carry-over in the sampling device or breakthrough could be detected. The samples were stable for at least a week. The combined precision in sampling and analysis was excellent, with a coefficient of variation of 13%.

Evaluation of a new electronic spirometer: the vitalograph "Escort" spirometer.

The "Escort" spirometer is a lightweight, hand held spirometer employing a Fleisch pneumotachograph. Measurements of forced expiratory volume in one second (FEV1), forced vital capacity (FVC), and peak expiratory flow (PEF) are obtained from a single FVC manoeuvre. Results are displayed on a small liquid crystal display, but there is no graphical display. The performance of the Escort spirometer has been compared with that of a wedge bellows spirometer (Vitalograph S model) and a Wright PEF meter. One hundred and thirteen subjects performed three FVC manoeuvres on the wedge bellows and Escort spirometers and three PEF manoeuvres on the Wright meter. The best reading for each index was recorded. In 21 of the subjects comparison of a Wright manoeuvre with an FVC manoeuvre on the Escort spirometer was performed, whilst in three subjects the effect of repeated blows was studied. The FEV1 ranged from 0.5 to 5.4 litres, FVC from 1.05 to 6.2 litres, and PEF from 100 to 725 l/min. The mean (SD) difference for the FEV1 was -0.05 (0.15) (95% confidence interval (95% CI) -0.07 to -0.02) litres, for FVC 0.03 (0.28) (95% CI -0.02 to +0.08) litres, and for PEF 1.68 (50.6) (95% CI -7.7 to +11.1) l/min. The differences were positively correlated with the mean reading for PEF and FVC but not for FEV1. The Wright PEF manoeuvre performed on the Escort produced significantly higher PEF readings (mean difference -22.9 litres). There was no significant effect of repeated FVC manoeuvres on any of the indices. The Escort spirometer compares extremely well with a wedge bellows spirometer for measurement of FEV1 and FVC, whilst yielding results of PEF from an FVC manoeuvre which are comparable to those obtained from a Wright meter. It can be recommended for use as a portable hand held spirometer.

Factors affecting peak expiratory flow variability and bronchial reactivity in a random population sample.

Bronchial reactivity measurements are widely used in epidemiological studies to provide an objective marker of asthma. There are, however, several potential advantages of measuring peak expiratory flow (PEF) variability instead, particularly in large studies. PEF variability and bronchial reactivity were compared in a population sample to assess the relationships of the two measurements to factors known to be associated with airways disease, and to compare their response rates. Subjects aged 18-65 were randomly selected from the electoral register of an administrative area in eastern England and randomised to attend either for a bronchial challenge test measuring the provocative dose of methacholine producing a 20% fall in FEV1 (PD20), or to measure PEF at two hourly intervals during waking hours for one week. Skin tests with common allergens were performed and a smoking history obtained. PEF variability was expressed as the amplitude % mean (highest - lowest x 100/mean). A total of 273 subjects (69%) collected a PEF meter but a completed record sheet was returned by only 247 (62%); this was still significantly more than the 202 subjects (54%) who attended for and successfully completed a challenge test. Amplitude % mean was higher in women than in men (9.7% v 8.5%). In multiple regression analysis amplitude % mean increased significantly with age, mean skin weal diameter, and with current smoking. The odds of having a PD20 below 24.5 mumol increased with mean skin weal diameter and were greater in current smokers. Neither age nor sex had a significant effect on bronchial reactivity but there were significant interactions between age and the effects of both smoking and atopy. The higher response rate associated with the use of PEF variability measurement, and the association with factors implicated in the pathogenesis of airways disease, suggest that PEF variability would be a useful measurement to employ in epidemiological studies.

Development of an accurate portable recording peak-flow meter for the diagnosis of asthma

This article describes the systematic design of an electronic recording peak expiratory flow (PEF) meter to provide accurate data for the diagnosis of occupational asthma. Traditional diagnosis of asthma relies on accurate data of PEF tests performed by the patients in their own homes and places of work. Unfortunately there are high error rates in data produced and recorded by the patient, most of these are transcription errors and some patients falsify their records. The PEF measurement itself is not effort independent, the data produced depending on the way in which the patient performs the test. Patients are taught how to perform the test giving maximal effort to the expiration being measured. If the measurement is performed incorrectly then errors will occur. Accurate data can be produced if an electronically recording PEF instrument is developed, thus freeing the patient from the task of recording the test data. It should also be capable of determining whether the PEF measurement has been correctly performed. A requirement specification for a recording PEF meter was produced. A commercially available electronic PEF meter was modified to provide the functions required for accurate serial recording of the measurements produced by the patients. This is now being used in three hospitals in the West Midlands for investigations into the diagnosis of occupational asthma. In investigating current methods of measuring PEF and other pulmonary quantities a greater understanding was obtained of the limitations of current methods of measurement, and quantities being measured. It is now possible to define the quantities that need to be measured for accurate pulmonary diagnosis and the requirements of future instrumentation to make these necessary measurements. We are now in the process of developing this new instrumentation.

The accuracy of portable peak flow meters.

The variability of peak expiratory flow (PEF) is now commonly used in the diagnosis and management of asthma. It is essential for PEF meters to have a linear response in order to obtain an unbiased measurement of PEF variability. As the accuracy and linearity of portable PEF meters have not been rigorously tested in recent years this aspect of their performance has been investigated. The response of several portable PEF meters was tested with absolute standards of flow generated by a computer driven, servo controlled pump and their response was compared with that of a pneumotachograph. For each device tested the readings were highly repeatable to within the limits of accuracy with which the pointer position can be assessed by eye. The between instrument variation in reading for six identical devices expressed as a 95% confidence limit was, on average across the range of flows, +/- 8.5 l/min for the Mini-Wright, +/- 7.9 l/min for the Vitalograph, and +/- 6.4 l/min for the Ferraris. PEF meters based on the Wright meter all had similar error profiles with overreading of up to 80 l/min in the mid flow range from 300 to 500 l/min. This overreading was greatest for the Mini-Wright and Ferraris devices, and less so for the original Wright and Vitalograph meters. A Micro-Medical Turbine meter was accurate up to 400 l/min and then began to underread by up to 60 l/min at 720 l/min. For the low range devices the Vitalograph device was accurate to within 10 l/min up to 200 l/min, with the Mini-Wright overreading by up to 30 l/min above 150 l/min. Although the Mini-Wright, Ferraris, and Vitalograph meters gave remarkably repeatable results their error profiles for the full range meters will lead to important errors in recording PEF variability. This may lead to incorrect diagnosis and bias in implementing strategies of asthma treatment based on PEF measurement.

Fungal contamination of mini peak flow meters

Sixteen peak expiratory flow meters from the Outpatient Department of Solihull Hospital were dismantled for inspection and washing. Fungal contamination was found in all 16 machines with visible contamination in four.

鼻腔通気度測定におけるピークフローメータの価値

We determined nasal peak flow using a peak flowmeter with a face mask (PALROD peak expiratory flowmeter) and nasal airway patency with an anterior rhinomanometer (Nihon Koden MPR-1100) at a minimum time interval in the same individual. We compared the values obtained by two kinds of measurements to evaluate the usefulness of the peak flowmeter for nasal airway patency. In this study, the nasal patencies were experimentally changed and measured in 30 patients using alpha-1 stimulant spray and in 25 patients with nasal allergy using nasal provocation of antigens. We also measured the natural circadian changes of nasal patency in 21 patients with nasal allergy and in 18 normal persons every two hours from 8:00 A.M. to 8:00 P.M. and from 9:00 A.M. to 9:00 P.M., respectively. As a result, we found close correlations between percent change of the peak flow and the nasal airway patency measured after spraying alpha-1 stimulant (r = 0.699, p less than 0.01), after antigen provocation (r = 0.585, p less than 0.01), and during circadian change (r = 0.464, p less than 0.01 in normal persons and r = 0.251, p less than 0.05 in allergy patients). In conclusion, peak flowmeter is handier and cheaper than rhinomanometer and is useful in evaluating the effect of vasoconstrictors and nasal provocation on nasal patency and in measuring the circadian changes of nasal patency. Since nasal secretion in the nose affects the measurement of peak flow, it should be removed as much as possible immediately before the flowmeter is used.

Use of anti-asthma drugs in New Zealand.

Increased sales of anti-asthma drugs, and a second "epidemic" of asthma mortality, raised concerns about the management of asthma in New Zealand. To study this, prescriptions were obtained from randomly selected pharmacies to identify 235 patients receiving one common anti-asthma drug, 175 of whom were willing to be interviewed. The authors considered that 80% had asthma, and only 20% suffered primarily from chronic bronchitis or emphysema. The increased sales of anti-asthma drugs could not therefore be explained by their increasing use in treatment of other respiratory disorders. One third of the identified asthmatic subjects experienced daily symptoms despite regular drug treatment. Inhaled corticosteroids were used by only 42% of this group with persistent symptoms. Regular or short course oral corticosteroids, with or without inhaled steroids, had been required by 49%. All patients with domiciliary nebulisers appeared to use these appropriately, and most had peak expiratory flow meters. Despite the increased sales of anti-asthma drugs, corticosteroids appear to be as much underused in patients with chronic asthma in the community as in those who die of their disease.

Self-Measurements for Asthma

To the Editor.— Julius et al (229:663, 1974) have documented well the value of self-determined blood pressure readings in the management of labile hypertension. Their article, which emphasizes again the patient aspartner, prompts me to recapitulate observations on the use of daily peak expiratory flow (PEF) measurements, taken by the patient at home or at work, for the investigation and the control of variable (labile) obstructive lung disease. The instrument in common use is the Wright peak expiratory flow meter, a small, portable, and relatively simple apparatus, which almost anybody above the age of 4 or 5 years can learn to use reliably. Self-determinations of PEF by the patient two to four times daily, under diverse conditions of exposure, activity, and medication, provide a meaningful record of intermittent obstruction of the airways (Ann Allergy30:443, 1972). More sophisticated techniques, such as spirometry, plethysmography, and gas dilution studies, performed only

Peak expiratory flow rates in chronic asthma. A gauge of progression and improvement.

Because there is doubt over the usefulness of the peak expiratory flow meter in assessing the course of chronic asthma, 55 children aged 6 to 18 years were studied over a period of 12 months. All children, who were receiving cromolyn sodium prophylaxis, were tested at monthly intervals with the peak expiratory flow rate (PEFR) meter and at three-month intervals by conventional spirometry. The patients were separated into three groups according to their monthly PEFR results: (1) values always within normal limits; (2) values fluctuating between normal and abnormal ranges; and (3) values consistently subnormal. A drop-off of at least 15% in PEFR was observed with 25 of the 55 children when five successive expirations were measured. The PEFR, the forced expiratory volume in the first second, and the maximum voluntary ventilation correlated well ( P =.001) in all cases. Pulmonary function values in 16 patients (29%) failed to show the expected return to normal during the one-year period.

Genitourinary Tuberculosis

BACKGROUND--Previous work has indicated a high rate of non-attendance at hospital based clinics among young, multiracial asthmatic patients of lower socioeconomic class. The efficacy of delivering asthma education from a community health centre established in a multiracial working class neighbourhood was evaluated. METHODS--A prospective controlled study was performed in which asthmatic subjects aged between two and 55 years attending a hospital emergency room with acute asthma and living within a defined geographical area of high emergency room users were randomised to the usual follow up or the education centre plus usual follow up. Measurements were taken at entry into the study and again nine months later. RESULTS--At nine months patients randomised to the education centre had more preventive medications, more peak expiratory flow meters and better flow meter technique, more self-management plans, better knowledge of appropriate action to take when confronted with worsening asthma, less nocturnal awakening, and better self-reported asthma control than the control group. There was no difference between the study groups in measurements of compliance, hospital admission, days lost from school or work, or emergency room use. CONCLUSIONS--The main effects of education were on asthma knowledge and self-management skills, whilst improvements in asthma morbidity were small. Potential reasons for this include heterogeneous study population (in terms of baseline self-management skills, asthma severity, ethnicity and age), pragmatic study design, insensitivity of many of the measurements of morbidity, the modest effectiveness of a single time limited education programme, and inability to limit the effects of such a large community based study to the intervention group (there was a 67% reduction in asthma admissions during the study period from the geographical area targeted compared with a 22% reduction for the rest of Auckland).