Malnutrition and peak expiratory flow rate

In order to assess the effects of malnutrition on the growth of lung function, 376 Indian schoolchildren aged 6-12 yrs were studied. Peak expiratory flow rate (PEFR) was measured with a Wright peak flow meter, and nutritional status assessed by calculation of the percentage predicted height for age (HFA) and weight for height (WFH) using Harvard standards. After standardizing for height and sex, the PEFR of 30 wasted children (WFH below 80%) was significantly reduced (p less than 0.01), but that of 135 stunted children (HFA below 90%) was higher than average (p less than 0.05). It is concluded that current malnutrition has a negative effect on PEFR, possibly due to impaired muscle function, but that past or chronic malnutrition affects growth of lung function less than it affects somatic growth.     

The relationship between FEV1 and peak expiratory flow in patients with airways obstruction is poor

STUDY OBJECTIVES: To evaluate the correlation between FEV1 and peak expiratory flow (PEF) values expressed as a percentage of their predicted value, and to assess factors influencing differences between the two measurements. DESIGN: Cross-sectional. SETTING: Pulmonary function laboratory at a tertiary-level teaching hospital in northern India. PARTICIPANTS: A total of 6,167 adult patients showing obstructive pattern on spirometry over a 6-year period. INTERVENTIONS: None. MEASUREMENTS AND RESULTS: There was considerable variability between percentage of predicted FEV1 (FEV1%) and percentage of predicted PEF (PEF%). Locally weighted least-square modeling revealed that PEF% underestimated [corrected] FEV1% in patients with less severe obstruction and overestimated [corrected] it in those with more severe obstruction. Using Bland-Altman analysis, PEF% underestimated FEV1% by a mean of only 0.7%; however, limits of agreement were wide (- 27.4 to + 28.8%), indicating that these two measurements cannot be used interchangeably. PEF% and FEV1% were > 5% apart in approximately three fourths and differed by > 10% in approximately one half of the patients. On multivariate analysis, discordance > 5% was significantly influenced by female gender (odds ratio, 1.26; 95% confidence interval [CI], 1.01 to 1.58) and increasing FEV1% (odds ratio, 1.09 for every 10% increase; 95% CI, 1.04 to 1.14) but not by height or age. CONCLUSIONS: FEV1% and PEF% are not equivalent in many patients, especially women and those with less severe airflow limitation. Assumptions of parity between PEF% and FEV1% must be avoided.     

Comparison of peak expiratory flow variability between workers with work-exacerbated asthma and occupational asthma

BACKGROUND: Peak expiratory flow (PEF) monitoring is frequently used to diagnose occupational asthma (OA). The variability of PEF between periods at work and away from work has not been described in workers with work-exacerbated asthma (WEA). We sought to assess and compare the diurnal variability of PEF during periods at and away from work between subjects with OA and WEA. METHODS: Workers referred for work-related asthma underwent PEF monitoring for 2 weeks at and away from work. The diagnostic of OA or WEA was subsequently made according to the respective positivity or negativity of the specific inhalation challenges. PEF mean diurnal variability was calculated during periods at and away from work. PEF graphs were also interpreted using direct visual analysis by five observers and using a computer program (Oasys-2, Expert System ) [available at: http://www.occupationalasthma.com]. RESULTS: Thirty-four subjects were investigated (WEA, n = 15; OA, n = 19). There was a greater variability of PEF at work than away from work in both OA (19.8 +/- 8.7% vs 10.7 +/- 6.3%, p < 0.001) and WEA (14.2 +/- 4.8% vs 10.6 +/- 5.6%, p = 0.02). However, the magnitude of the variability was higher in OA than in WEA (p = 0.02). The visual interpretation of PEF or the Oasys-2 program failed to distinguish WEA from OA. CONCLUSION: Although workers with OA showed a higher PEF variability than workers with WEA when at work, clinicians were unable to reliably differentiate OA from WEA using the visual interpretation of PEF graphs or the computerized analysis.     

Comparison between peak expiratory flow and FEV(1) measurements on a home spirometer and on a pneumotachograph in children with asthma

BACKGROUND: The accuracy of electronic portable home spirometers has been demonstrated in vitro using computer-based waveforms. We assessed the agreement in vivo between measurements of lung function on an electronic spirometer (Koko Peak Pro) and those obtained by the gold standard, a hospital lung function laboratory pneumotachograph. METHODS: Fifty stable asthmatic children (33 boys), aged 6-17 years, performed peak expiratory flow (PEF) and forced expiratory volume in 1 sec (FEV(1)) measurements according to international guidelines on a portable home spirometer and on the hospital pneumotachograph in random order. All measurements complied to standard quality criteria. The PEF and FEV(1) values recorded with the home spirometer and on the hospital pneumotachograph were compared. RESULTS: All children performed reproducible high-quality measurements on both spirometers. PEF values on the home spirometer were considerably lower than on the laboratory pneumotachograph (95% CI for difference in PEF 14-30 L/min; P < 0.0001). Individual differences in PEF between the two devices could be >100 L/min. The FEV(1) values were slightly, but significantly, lower on the home spirometer (95% CI for difference in FEV(1) 0.02-0.1 L; P = 0.0018). CONCLUSIONS: A home spirometer provides reproducible and quality acceptable measures in children with asthma when performed under professional supervision and encouragement. Mean PEF and FEV(1) values recorded on this home spirometer are significantly lower than those on a hospital pneumotachograph, and individual differences may be large. Therefore, home spirometry may not be interchanged with pneumotachography in a lung function laboratory.     

An assessment of peak expiratory flow as a surrogate measurement of FEV1 in stable asthmatic children

We examined the relationship over 24 hours between percent-predicted values (PPV) of peak expiratory flow (PEF) and forced expiratory volume in one second (FEV1) in a group of 23 stable untreated asthmatic children 6 to 17 years of age by means of regression analysis as well as the percentage difference between the PPV of these two measurements. Although the Pearson correlation coefficient between the PPV was consistently high, ranging between 0.854 and 0.892, the assumption that such a finding substantiates the substitution of PEF for FEV1 is called into question. Over 50 percent of the subjects displayed a 10 percent or greater difference in the PPV between the two measurements, regardless of the time of day the two respiratory variable were determined, while over one-third of all subjects evidenced a 20 percent or greater discrepancy between the PPV of the two measures. While, on a group basis, there was no statistically significant difference in the mean percentage difference over 24 hours between the PPV of FEV1, when compared with the corresponding measurement of PEF, reliance on PEF alone in individual subjects may result in a false impression of the patency of the airways in comparison to the FEV1.     

Comparisons of peak diurnal expiratory flow variation, postbronchodilator FEV(1) responses, and methacholine inhalation challenges in the evaluation of suspected asthma

STUDY OBJECTIVES: The validity of peak expiratory flow variation (PEFvar) as defined by National Heart, Lung, and Blood Institute (NHLBI) guidelines as a diagnostic tool for suspected asthma or its comparative value to methacholine inhalation challenge (MIC) or postbronchodilator (BD) FEV(1) responses has not been formally assessed. We prospectively analyzed the correlation of 28 different PEFvar indexes (including 4 NHLBI-compatible indexes) with MIC and pre-BD and post-BD FEV(1) responses in suspected asthmatic subjects with normal findings on lung examination, chest radiography, and baseline spirometry. DESIGN: Participants were asked to record peak expiratory flow four times daily for 2 to 3 weeks, followed by an MIC. During a minimum 6-month follow-up period, a clinical diagnosis of asthma was made or ruled out based on testing results and response to antiasthma therapy. SETTING: Medical school-affiliated subspecialty private practice of allergy, asthma, and immunology. PARTICIPANTS: One hundred twenty-one suspected asthmatic patients with normal findings on lung examination, chest radiography, and baseline spirometry. MEASUREMENTS AND RESULTS: Fifty-seven subjects completed both the peak flow diary and the MIC and were accepted for statistical analysis. There were no statistically significant correlations between any peak expiratory flow index and MIC. Among the three diagnostic tools evaluated, MIC had the highest sensitivity (85.71%). All the PEFvar indexes and post-BD responses had low sensitivity and high false-negative rates. CONCLUSIONS: PEFvar and post-BD FEV(1) responses are poor substitutes for MIC in the assessment of patients with suspected asthma with normal findings on lung examination, chest radiography, and spirometry. Our findings warrant a reconsideration of the NHLBI guidelines recommendation of the utility of PEFvar as a diagnostic tool for asthma in clinical practice.     

Peak expiratory flow is not a quality indicator for spirometry: peak expiratory flow variability and FEV1 are poorly correlated in an elderly population

BACKGROUND: Peak forced expiratory flow (PEF) and FEV(1) are spirometry measures used in diagnosing and monitoring lung diseases. We tested the premise that within-test variability in PEF is associated with corresponding variability in FEV(1) during a single test session. METHODS: A total of 2,464 healthy adults from the Health, Aging, and Body Composition Study whose spirometry results met American Thoracic Society acceptability criteria were screened and analyzed. The three "best" test results (highest sum of FVC and FEV(1)) were selected for each subject. For those with acceptable spirometry results, two groups were created: group 1, normal FEV(1)/FVC ratio; group 2, reduced FEV(1)/FVC ratio. For each subject, the difference between the highest and lowest PEF (DeltaPEF) and the associated difference between the highest and lowest FEV(1) (DeltaFEV(1)) were calculated. Regression analysis was performed using the largest PEF and best FEV(1), and the percentage of DeltaPEF (%DeltaPEF) and percentage of DeltaFEV(1) (%DeltaFEV(1)) were calculated in both groups. RESULTS: Regression analysis for group 1 and group 2 showed an insignificant association between %DeltaPEF and %DeltaFEV(1) (r(2) = 0.0001, p = 0.59, and r(2) = 0.040, p = 0.15, respectively). For both groups, a 29% DeltaPEF was associated with a 1% DeltaFEV(1). CONCLUSION: Within a single spirometry test session, %DeltaPEF and %DeltaFEV(1) contain independent information. PEF has a higher degree of intrinsic variability than FEV(1). Changes in PEF do not have a significant effect on FEV(1). Spirometry maneuvers should not be excluded based on peak flow variability.     

Diurnal variation of peak expiratory flow rate in asthmatic children

A diurnal variation in peak expiratory flow rate (PEFR) has been described in normal and asthmatic adults. This variation has been apparent in data reported from children, but the rhythm has not been characterized. Sixty-eight asthmatic children recorded PEFR three times a day for 4 weeks at home. Data were analyzed using paired t-tests, cosinor analysis, and spectral analysis. Fifty subjects (73.5%) had significant diurnal variations in PEFR on paired t-tests. Mean amplitude, derived from cosinor analysis, was 22.6% (SD = 13.2%) of mean PEFR. The trough of the PEFR rhythm occurred at 0345 hours for the group. Spectral analysis confirmed that the major component of the variation in PEFR was due to a rhythm with a period of 24 hours. The amplitude of the diurnal variation was not related to the subjects' age, sex, or medications taken but was inversely related to mean lung function (expressed as percentage predicted).     

Reproducibility of peak expiratory flow rate measured at home

In 8 stable patients with chronic asthma, the reproducibility of peak expiratory flow rate (PEFR) measured and recorded 4 times per day for longer than 1 month at home and at work was assessed. Average %PEFRs of individuals through the periods observed were higher than 80%, and coefficients of variation were less than 10% regardless of the time measured. This suggested that a decrease in %PEFR more than 10% reflects early phase of deterioration of airways narrowing and frequent measurement of PEFR is essential for long-term management and for self-assessment of chronic asthma.     

The effect of dialyzer reuse on peak expiratory flow rate

Peak expiratory flow rates were measured during routine haemodialysis in 18 patients with chronic renal failure who were in receipt of thrice weekly haemodialysis treatment, using both a new cuprophan dialyzer and then the same dialyzer after reprocessing. Acetate buffered dialysate was used on both occasions. The peak expiratory flow rates fell by 10 +/- 0.3%, mean +/- sem, during the first hour of treatment with the new dialyzer, and in seven patients (39%) the fall was greater than 15%. Whereas the reduction in peak expiratory flow rates was significantly less with reuse, 4 +/- 0.1% (P less than 0.5). Similarly, the fall in arterial oxygen tension was also reduced on reuse from 28 +/- 1.2% to 14 +/- 1.3% at 30 min (P less than 0.05) and from 30 +/- 1.4% to 18 +/- 3.1% (P less than 0.05) at 60 min of dialysis. There was also a reduction in the fall in the peripheral platelet count at 30 min of dialysis from 14 +/- 0.8% to 9 +/- 0.4% with reuse (P less than 0.05). However, there was no change in dialysis associated leukopenia with reuse of the dialyzer membrane. These results suggest that reprocessing the dialyzer membrane alters its biocompatibility characteristics resulting in an improvement in biocompatibility and further supports the role of inflammatory cell mediator release in the pathogenesis of dialysis associated hypoxaemia and pulmonary dysfunction during the first hour of dialysis treatment.     

Inter-session reproducibility of peak expiratory flow with standardized expiratory maneuvers

BACKGROUND: In adults performing forceful expiratory maneuvers, the length of post-inspiratory pause prior to forced expiration may influence the subsequently measured peak expiratory flow (PEF) and increase its variability. We investigated the effects of two different lengths of breath-hold at total lung capacity (TLC) on the short-term reproducibility of PEF in healthy volunteers. METHODS: Forty-six healthy volunteers (age 34.6+/-8.5; 23 men) performed a series of maximal forceful expirations in two different test sessions, separated by approximately 2 weeks. In each test-session, PEF was measured with two different types of maneuvers. One maneuver (P) included a brief (<2s) post-inspiratory pause at TLC prior to forced expiration, whereas the second maneuver (NP) included no pause at TLC. The speed of inspiration to TLC was fast and similar for both maneuvers. In a given test session, all volunteers performed four efforts for each type of maneuver. The highest PEF for each maneuver was used for analysis. The Bland-Altman statistical analysis was used to determine inter-session reproducibility of PEF. RESULTS: Within-maneuver analysis of the between-test session reproducibility of PEF showed that neither maneuver systematically biased the measured PEF (mean difference 0.02L/s for the P and 0.17L/s for the NP maneuver). Inter-maneuver between-test session analysis similarly showed that neither maneuver introduced a systematic bias in the maximal PEF (mean difference ranged from -0.15 to -0.01L/s). The limits of agreement were comparable in all maneuver-pair analyses. CONCLUSIONS: Forceful expiratory maneuvers with or without a brief (<2s) pause at TLC produce comparable PEF values in test-retest sessions.     

Comparison between peak expiratory flow rate and forced expiratory volume in one second in the evaluation of children suspected to have asthma

This study was conducted to evaluate whether forced expiratory volume in 1 second (FEV1) for the diagnosis of bronchial reactivity by means of the free-running exercise test and bronchodilator inhalation, could be appropriately replaced by simple measurements of peak expiratory flow rate (PEFR) in children.We studied 108 referred symptomatic children (due to chronic cough or wheezing) suspected to have asthma aged 5-14y. Forced breathing spirometry and the "Mini-Wright peak flow meter" tests were recorded before and fifteen minutes after the challenge with free- running exercise or bronchodilator (Salbutamol) inhalation, regarding the baseline FEV1 value (FEV1> 80% considered as normal).There was a high correlation between PEFR and FEV1 (in absolute value and percent predicted) measured before and after bronchodilator inhalation test (r = 0.48, P = 0.05) in comparison to the values referred to free- running exercise test (r = 0.26, P = 0.01)."forced breathing spirometry" and "Mini-Wright peak flow" cannot be used interchangeably for diagnosing asthma, and PEFR measurement should remain a procedure for monitoring and following up the patients.     

Omeprazole improves peak expiratory flow rate and quality of life in asthmatics with gastroesophageal reflux

Objective: The aim of this study was to determine if omeprazole improves pulmonary function and quality of life in asthmatics with gastroesophageal reflux.
Methods: This was a double blind, randomized, placebo-controlled cross-over trial. After a 4-wk lead-in period, nine patients with documented asthma and gastroesophageal reflux, were prescribed either omeprazole 20 mg, daily or placebo for 8 wk and then crossed over to the alternate treatment. Outcome measurements included: forced expiratory volume at 1 s (FEV₁), peak expiratory flow rate (PEFR), and responses on the Asthma Quality of Life Questionnaire, a validated disease specific measure of functional status.
Results: After omeprazole treatment, compared with placebo, patients had higher mean morning and evening PEFR, mean absolute difference (95% CI): morning: 37.8 L/min. (10.9–64.6), evening: 31.2 (3.2–59.2). Omeprazole treatment led to higher mean overall scores on the Asthma Quality of Life Questionnaire, and on the subdomains of activity limitation, symptoms, and emotions (   p = 0.039  , 0.049, 0.024, 0.040). A trend toward higher FEV₁ (mean: 15.6% difference) with omeprazole failed to reach statistical significance (   p > 0.2  ).
Conclusions: After taking omeprazole for 8 wk, asthmatics with GER have better PEFR and quality of life than after placebo.     

Effect of air pollution on peak expiratory flow rate variability.

Exposure to air pollution affects pulmonary functions adversely. Effect of exposure to pollution on diurnal variation of peak flow was assessed in healthy students. Three hundred healthy age-matched nonsmoker students were studied. They were categorized into two groups on the basis of their residence: commuters and living on campus. Peak expiratory flow (PEF) recordings were made twice daily for 2 days with the Pink City Flow Meter. The measurement was then used to calculate for each subject the amplitude percentage mean, which is an index for expressing PEF variability for epidemiological purposes (Higgins BG, Britton JR, Chinns Jones TD, Jenkinson D, Burnery PG, Tattersfield AE. Distribution of peak expiratory flow variability in a population sample. Am Rev Respir Dis 1989; 140:1368-1372). Air pollution parameters were quantified by measurement of sulfur dioxide (SO2), oxides of nitrogen (NO2), carbon monoxide (CO), and respirable suspended particulate matter (RSPM) in the ambient air at the campus and on the roadside. The mean values of PEF variability (amplitude percent mean) in the students living on campus and in the commuters were 5.7 +/- 3.2 and 11 +/- 3.6, respectively (P < .05). Among the commuters, maximum number of subjects showed amplitude percentage mean PEFR at the higher end of variability distribution, as compared to the students living on campus, among whom the majority of subjects fell in the lower ranges of variability distribution. The ambient air quality parameters, namely SO2, NO2, CO, and RSPM were significantly lower on the campus. It can be concluded that long-term periodic exposure to air pollution can lead to increased PEF variability even in healthy subjects. Measurement of PEF variability may prove to be a simple test to measure effect of air pollution in healthy subjects.     

Reference values for peak expiratory flow rate in adults of African descent

Substantial racial differences in the values of peak expiratory flow (PEF) rate have been noted by several workers in the past. It has also been noted that applying prediction formulae derived from a Caucasian population overestimated the PEF values in Black Africans by 12%-15%. Yet reference values used up until the present, even among Black populations, are based on such formulae. This study provides new reference values for use in the Black population. They were obtained by using curvilinear formulae derived from the study of 1009 normal adult Nigerians (668 men and 341 women) between the ages of 15 years and 82 years, living and/or working in Port Harcourt, Nigeria and its hinterland.