The use of peak expiratory flow rate measurements in respiratory disease

Associations between the muscle quality index and adult lung functions from NHANES 2011-2012

Background

The muscle quality index (MQI), as an important component of sarcopenia, is defined as the ratio of muscle strength to muscle mass. Lung function, is a clinical indicator to assess ventilation and air exchange function. This study investigated the relationship between lung function indices and MQI in the NHANES database from 2011 to 2012.

Methods

This study included 1,558 adults from the National Health and Nutrition Examination Survey from 2011 to 2012. Muscle mass and muscle strength were assessed using DXA and handgrip strength, and all participants underwent pulmonary function measurements. Multiple linear regression and multivariable logistic regression were used to assess the correlation between the MQI and lung function indices.

Results

In the adjusted model, MQI was significantly correlated with FVC% and PEF%. And, after quartiles of MQI in Q3, where FEV₁%, FVC%, and PEF% were all associated with MQI, in Q4, a lower relative risk of a restrictive spirometry pattern was linked to increased MQI. Compared to the lower age group, the relationship between the MQI and lung function indices was more significant in the higher age group.

Conclusion

There was an association between the MQI and lung function indices. Furthermore, in the middle-aged and older adult populations, lung function indicators and restrictive ventilation impairment were significantly associated with MQI. This implies that improving lung function through muscle training may be beneficial to this group.

Subcutaneous allergen immunotherapy for asthma: A randomized, double-blind, placebo-controlled study with a standardized Blomia tropicalis vaccine

BACKGROUND

Sensitization to Blomia tropicalis (Bt) is very frequent in the tropics, and particularly in Cuba, being a significant cause of allergic asthma. Allergen immunotherapy (AIT) with Bt can be a therapeutic option, however, placebo-controlled clinical trials have not been reported.

OBJECTIVE

To assess the therapeutic effect and safety of AIT for asthma using a standardized allergen vaccine of B. tropicalis by subcutaneous route, in allergic asthmatic patients exposed and sensitized to this mite species.

METHODS

A double-blind, placebo-controlled Phase II trial was conducted in 35 adults (18 with treatment and 17 with placebo), with mild to moderate asthma, predominantly sensitized to Bt. AIT was administered subcutaneously in increasing doses from 4 to 6000 Biological Units using a locally manufactured standardized extract (BIOCEN, Cuba). Patient assessment was performed using symptom-medication score (SMS), peak expiratory flow and skin reactivity relative to Histamine as measured by skin prick test (SPT).

RESULTS

The 12-month treatment achieved a significant (p < 0.001) decrease of SMS. Symptom score showed only 41% (CI: 26-61) of placebo values, whereas medication was 34.5% (22.4%-63.3%). Treatment was regarded clinically effective in 67% of patients (OR 32; 95%CI: 17 to 102). The effect size on symptoms and medication was higher than has been reported with equivalent allergen dosages of D. pteronyssinus and D. siboney in Cuban asthmatic patients. Skin reactivity to Bt was also significantly reduced (p = 0.0001), increasing 148-fold the allergen threshold to elicit a positive skin test. This desensitization effect was specific to Bt and did not modify the reactivity to Dermatophagoides. The change of specific skin reactivity was significantly (p < 0.05) correlated to clinical improvement. All adverse events were local with a frequency of 2.4% of injections.

CONCLUSIONS

Subcutaneous AIT with Blomia tropicalis was effective and safe in asthmatic adults exposed and sensitized to this mite species in a tropical environment.

TRIAL REGISTRATION

Cuban Public Registry of Clinical Trials: RPCEC00000026 (WHO International Clinical Trial Registry Platform ICTRP).

Ambient PM2.5 causes lung injuries and coupled energy metabolic disorder

Ambient fine particulate matter (PM_2.5) is a challenge to public health worldwide. Although increasing numbers of recent epidemiological studies have emphasized the critical role of PM_2.5 in promoting respiratory diseases, the precise mechanism behind PM_2.5-mediated lung obstruction remains obscure. In the present study, we analyzed lung structure and function and further investigated mitochondrial morphology and transcription-modulated energy metabolism in mice following PM_2.5 aspiration. The results showed that PM_2.5 exposure reduced pulmonary function and induced severe pathological alterations, including alveolar endothelial disruption and airway obstruction. Based on ultrastructural observations, we also found mitochondrial vacuolation and mitochondrial membrane rupture in alveolar type II epithelial cells. Importantly, the abnormality of mitochondrial structure was coupled with energy metabolism disorders, as evidenced by the decrease in ATP levels, the accumulation of pyruvate and lactate content, and the altered transcription of related genes. Moreover, the reduction in mitochondrial markers, including PGC-1α, NRF-1, and TFAM, were involved in mitochondrial dysfunction. These findings suggest that energy metabolic disorders and mitochondrial dysfunction may be the important contributors to pulmonary injuries in response to PM_2.5 exposure, indicating possible targets for protection and therapy in polluted areas.

Asthma management by medical practitioners: the situation in a developing country

BACKGROUND

Asthma is a common chronic disease worldwide and is responsible for considerable morbidity, socioeconomic burden, and depletion of health resources. Clinically, diagnosis of asthma is based on information obtained from symptom questionnaires, physical examination and demonstration of variable airflow obstruction. Proper diagnosis of asthma is mandatory in clinical practice in order to avoid undue use of potentially toxic asthma medications and prevent unwarranted social stigmatization. This study aimed to determine how medical practitioners in Nigeria diagnose asthma and use asthma medications during asthma exacerbation and the follow-up period.

METHODS

A semi-structured self-administered questionnaire on asthma management was distributed to medical practitioners attending the annual scientific meeting/update course in August, 2009. Forty-nine practice centers in the 6 geopolitical zones in Nigeria were included in this survey.

RESULTS

Totally 131 medical practitioners (80 males, 51 females) completed the questionnaire. Post National Youth Service Corp practice (mean ± SD) was 9.95±7.78 years, ranging from 2 to 39 years. The practice centers of respondents included university teaching hospitals (65.6%), state specialist hospitals (17.6%), private hospitals (10.7%), and missionary hospitals (6.l%). Respondents' assessment of burden of asthma was high (30.5%), moderate (63.4%) and low (6.1%). Asthma diagnosis was made by various methods including: symptoms only (35.9%), health personnels (32.3%), mother/self evaluation (20.3%), and use of spirometry/peak expiratory flow rate (11.5%). Thus inappropriate asthma diagnosis could have been practiced by 116 (88.5%) medical practitioners.

CONCLUSION

The study revealed inadequate knowledge of asthma diagnosis and drug management of asthma by medical practitioners in Nigeria.

Safety and efficacy of extracorporeal granulocyte and monocyte adsorption apheresis in patients with severe persistent bronchial asthma

The Adacolumn is an adsorptive-type extracorporeal device, which is filled with cellulose diacetate beads that selectively adsorb granulocytes and monocytes. Patients with severe persistent asthma experience highly variable continuous symptoms and severe exacerbations in spite of medication based on inhaled glucocorticosteroids. Granulocyte and monocyte adsorption apheresis using extracorporeal circulation through the Adacolumn was performed in nine patients with severe persistent asthma. The extracorporeal circulation through the Adacolumn was performed once a week for 5 weeks. We were able to perform this therapy without any severe adverse effects in all patients, although one patient complained of general fatigue just after the circulations. In six of the nine patients, the increase in peak expiratory flow (PEF) was more than 50 mL/min. The average increase in morning PEF was 23.3% while that in the evening PEF was 26.4% after the therapy. This therapy was not harmful for patients with severe persistent asthma. A placebo-controlled study will be desired to evaluate the efficacy of this nonpharmacological strategy accurately.

The use of spirometers and peak flow meters in the diagnosis and management of asthma among Spanish pediatricians. Results from the TRAP study

The objective of this study was to determine the level of adherence of pediatricians in Spain to the Spanish National Guidelines for Asthma Treatment with regard to the use of a peak flow meter (PEFR) or a spirometer in the diagnosis and management of asthma in childhood and to analyze sources of variations in these practices. A prospective survey (consisting of demographic and asthma knowledge sections) was conducted over a 2-wk time interval of 3000 pediatricians throughout the country. At least one part of the questionnaire was completed and returned by 2773 individuals (92.4%), with 2347 (78.2%) answering both sections; results are for this population. Around 62% of the pediatricians reported having a peak flow meter or a spirometer in their office; however, only 33% and 48% of them used the devices for the diagnosis and treatment of asthma, respectively. There was a significant association between being older (36-55 yr old) and using PEFR or spirometry for the diagnosis (OR: 1.35, 95% CI 1.11-1.66) and the management (OR 1.47, 95% CI 1.22-1.77) of asthma. Males used a peak flow meter or a spirometer more often than females for the diagnosis (37.8% vs. 30.9%, p = 0.001) and management of asthma (52.0% vs. 45.6%, p = 0.008). Pediatricians with formal pediatric residence training used these devices more for the diagnosis (OR: 1.39, 95% CI 1.09-1.75) and management (OR: 1.58, 95% CI 1.27-1.96) than those without. Working in a hospital was also related with more peak flow meter or spirometer use than working in health centers (OR: 2.08, 95% CI 1.71-2.54 for diagnosis; OR: 1.83, 95% CI 1.50-2.22 for management). About one-third of the Spanish pediatricians surveyed use spirometers and/or peak flow meters for diagnosing asthma and about half use one of these devices occasionally for managing the disease. Independent factors favoring their use are: age 36-55 yr, male gender, working in a hospital setting, and having been trained in a formal pediatric residence program.

[Care of children and adolescents with asthma by primary care physicians: current situation and proposals for improvement]

INTRODUCTION

To provide good asthma care to children and adolescents the following conditions are required: well-trained health professionals with the structure and resources necessary to perform their work efficiently, and client satisfaction as a measure of compliance and self-management. The aims of this study were to determine the current situation of asthma management by primary care pediatricians and to promote improvement of the healthcare and quality of life of these children and their families.

MATERIAL AND METHODS

We performed a descriptive study. A questionnaire was completed by primary care pediatricians attending asthma courses given by the Respiratory Team of the Spanish Association of Primary Care Pediatrics in 2001.

RESULTS

Three hundred twenty-three questionnaires were completed. The mean age of the pediatricians was 42 years and 70.6 % were women. A total of 7.4 % referred all patients to the pediatric pneumologist and 21.3 % referred all patients to the pediatric allergy clinic; 61.9 % referred only patients with moderate-severe persistent asthma. Concerning items registered in medical records, 32.5 % recorded a codified asthma diagnosis and 61 % included severity classification. Spirometers were available to 48.6 % and peak flow meters to 45.5 %. With regard to lung function measurement, 17.3 % performed spirometry and 33.2 % performed peak expiratory flow. Concerning asthma educational issues, 90.4 % had received education on environmental factors, 81.7 % had received training in the proper use of medication inhalers and 41.2 % had received training in written self-management plans.

CONCLUSIONS

This is the first study to present results on the current situation of asthma management by primary care pediatricians in Spain. The results show the need to improve record-keeping, facilitate the resources required for diagnosis and follow-up and prioritize education in order to achieve an optimal level of self-management by patients and their families.

Management of children with severe asthma exacerbation in the emergency department

Although acute asthma is a very common cause of emergency department visits in children, there is as yet insufficient evidence for the establishment of a standardized treatment protocol. The aim of this review is to describe updated information on the management of asthma exacerbations in the pediatric emergency department. Oxygen is the first-line treatment of acute asthma exacerbations in the emergency department to control hypoxemia. It is accompanied by the administration of beta(2)-adrenoceptor agonists followed by corticosteroids. beta(2)-Adrenoceptor agonists have traditionally been administered by nebulization, although spacers have recently been introduced and proven, in many cases, to be as effective as nebulization. Oral prednisolone, with its reliability, simplicity, convenience and low cost, should remain the treatment of choice for the most severe asthma exacerbations, when the lung airways are extremely contracted and filled with secretions. Recently, several studies have shown that high-dose inhaled corticosteroids are at least as effective as oral corticosteroids in controlling moderate to severe asthma attacks in children and therefore should be considered an alternative treatment to oral corticosteroids in moderate to severe asthma attacks. Studies of other drugs have shown that ipratropium bromide may be given only in addition to beta(2)-adrenoceptor agonists; theophylline has no additional benefit, and magnesium sulfate has no clear advantage. Comprehensive asthma management should also include asthma education, measures to prevent asthma triggers, and training in the use of inhalers and spacers. Proper management will avoid most asthma attacks and reduce admission and readmission to emergency departments.

Can peak expiratory flow measurements estimate small airway function in asthmatic children?

BACKGROUND

Asthma is characterized in part by small airways dysfunction. Peak expiratory flow (PEF) measurement has been suggested by all international guidelines as an important tool in asthma management. The correlation between PEF and FEV(1) but not with forced expired flow at 50% of vital capacity (FEF(50)) is well-established.

STUDY OBJECTIVE

To determine the value of PEF measurement as a predictor of small airways status as expressed by FEF(50).

DESIGN

Analysis of the association between PEF and FEF(50) in single and multiple determinations.

PATIENTS

One hundred eleven asthmatic children (mean age, 11.8 years), grouped in the following way according to FEV(1) values: within normal range (n = 46); mildly reduced FEV(1) (n = 44); and moderately/severely reduced FEV(1) (n = 21).

RESULTS

Overall, FEF(50) and PEF were significantly correlated (r = 0.49; p < 0.0001). However, in 41.6% of the patients, the actual FEF(50) differed by > 20% from the calculated FEF(50). PEF has a high specificity (82.4%) but a poor sensitivity (51.7%) to detect FEF(50) status. PEF was better able to reflect abnormal FEF(50) in the patients with more severe asthma and to reflect normal FEF(50) values in the healthier patients. In patients with multiple measurements (n = 40), the correlation between FEF(50) and PEF was significantly better than that derived from a single determination (multiple measurements r = 0.77; single measurement, r = 0.49).

CONCLUSIONS

Although PEF is an important tool in the management of asthmatic patients, it does not yield a complete picture because it is not sensitive in detecting small airways function. It is best used at home along with regular spirometry measurements at the clinic. PEF may serve as a better index of changes in small airways function once an individual regression is determined.

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.

Do eosinophil counts correlate differently with asthma severity by symptoms versus peak flow rate?

BACKGROUND

Discrepancy in asthmatic assessment by symptoms and peak flow rate (PFR) is a frequent dilemma. Currently, total peripheral eosinophil count (TPEC) is under study for asthma evaluation.

OBJECTIVES

To explore the correlation between TPEC and asthma severity assessed by symptoms alone versus symptoms and PFR.

METHOD

Adults asthmatics were selected from the Asthma Clinic. Severity assessment was based on two methods: symptoms alone or symptoms and PFR. Expiratory PFR was recorded by a Wright peak flow meter. Severity levels included mild intermittent, mild persistent, moderate persistent, and severe persistent. Total peripheral eosinophil count was performed on a Celldyn-3500 counter. Data was analyzed for statistical significance.

RESULTS

Sixty asthmatics aged 15 to 70 years (mean = 34 years), of which 68.3% were female, were studied. Severity levels differed between the two assessment methods in 45% of the cases and showed a predominance of the moderate persistent type. Total peripheral eosinophil count ranged between 22 and 2470 cells/mm3 (mean = 520 +/- SD = 393) and eosinophilia was found in 50% of the cases. Total peripheral eosinophil count showed a high positive correlation with increased asthma severity level assessed by history alone (r = 0.460, P < .001); more than by history and PFR (r = 0.328, P < .05).

CONCLUSION

The discrepancy between symptoms and PFR is confirmed by these results. A reliable objective parameter in asthma assessment is a continuous challenge. This study advocates the possible supplementation of TPEC as another objective parameter that might help in selecting the appropriate severity level in asthmatics.

How the discrepancy between symptoms and peak expiratory flow rate influences evaluation of asthma severity

BACKGROUND

Recent asthma guidelines recommend the assessment of severity levels based on the most severe symptoms and peak expiratory flow rate (PEFR). Discrepancies are frequently encountered in the use of these variables in determining the severity levels of asthmatics. The objective of this study was to determine the difference in asthma severity levels as assessed by either symptoms alone or by PEFR alone, as compared with the assessment by the asthma guidelines.

PATIENTS AND METHODS

Severity levels that were determined by recent asthma guidelines for 60 asthmatic patients were reassessed, based on symptoms alone and PEFR alone. They were compared for any significant differences to the asthma guidelines.

RESULTS

Asthmatics were aged between 15 and 70 (mean 34) years, and 63.8% were females. Severity levels by symptoms alone were different from the guidelines in 27 cases (45%). Of these, 89% showed a tendency toward higher severity levels. Severity levels by PEFR alone were different in only three cases (5%). In both comparisons, differences of severity levels were significant (P<0.0001), but assessment by symptoms alone showed more deviation (x(2) =162.1) than PEFR alone (x(2) =73.1).

CONCLUSION

The study documented significant discrepancies in asthma severity assessed by symptoms alone and PEFR alone, when compared to the recent asthma guidelines. Severity assessed by symptoms alone showed lower levels, and the use of PEFR tended to categorize some asthmatics into a more severe level.

Peak flow variability in the SAPALDIA study and its validity in screening for asthma-related conditions. The SPALDIA Team

We used 3-wk peak expiratory flow (PEF) measurements (twice daily) made in the diary study of the population-based Swiss Study on Air Pollution and Lung Disease in Adults to describe PEF-variability (PEF(var)) (amplitude as a percent of the mean, PEF [i.e., difference between morning and evening values divided by the mean]) in the study population and in five subgroups (physician-diagnosed asthma; current asthma, or physician-diagnosed asthma plus asthma attacks and/or medication; history of wheezing without a cold; hyperreactive; and nonsymptomatic). We assessed the performance of PEF(var) as a potential tool with which to screen for asthma. Alternatively, subjects with a PEF(var) of >/= 20%, >/= 30%, and >/= 50% on at least 2 d were considered to have high variability. The analyses were conducted for subgroups with different pretest probabilities for asthma-related conditions. The median PEF(var) was 4.5%. Among asthmatic subjects, women had nonsignificantly higher PEF(var) values than did men. In all other groups, women had significantly lower PEF(var). Both in the entire population and in subgroups with a higher pretest probability for asthma-related conditions, screening performance of PEF was limited. A PEF(var) of >/= 20% on at least 2 d detected current asthma with a sensitivity of 36% (specificity = 90%; positive predictive value = 16.4%). Results were better among subjects with a history of wheezing without colds (sensitivity = 40.4%; specificity = 83.6%; positive predictive value = 45.2%). PEF(var), a useful measure both clinically and in epidemiology, is of limited value when unselected populations are screened for asthma-related conditions, since the overlap of PEF(var) distributions across subgroups is large.

Healthy women's PEF variations with ambient summer concentrations of PM10, PM2.5, SO42-, H+, and O3

The relationship between ambient air pollution and daily change in peak expiratory flow (PEF) was studied in a sample of 473 nonsmoking women (age 19 to 43 yr) in Virginia over summers 1995- 1996. Daily 24-h averages of particulate matter (PM2.5 and PM10), fine particulate sulfate (SO42-) and strong acid (H+), hourly ozone (O3), and select meteorologic variables (e.g., temperature) were collected at a regional outdoor monitoring site. Subjects took PEF measurements twice daily for a 2-wk period using a standard MiniWright peak flow meter. Concurrent measures for summer periods of 24-h PM2.5 (micrograms/m3) ranged from 3.5 to 59.7; H+ (nmol/m3) from 0 to 250; maximal daily 8-h average O3 (ppb) from 17.0 to 87.6. Morning PEF decrements were significantly associated with H+ and PM2. 5. An increase of 50 etamol/m3 of H+ and 10 micrograms/m3 of PM2.5 related to decreases of 0.89 (95% CI = 0.21 to 1.57) and 0.73 (95% CI = 0.07 to 1.38) L/min in morning PEF, respectively. Ozone was the only exposure related to evening PEF with 5-d cumulative lag exposure showing the greatest effect; 7.65 L/ min (95% CI = 2.25 to 13.0) decrease per 30 ppb O3 increase. Separate physiologic effects were observed for summer ambient concentrations of two different pollutants (PEF decrements related to PM2.5 in morning and O3 in evening) at concentrations below the new U.S. EPA 24-h ambient air quality standard for PM2.5 and 8-h standard for O3.

Using statistical process control charts for the continual improvement of asthma care

BACKGROUND

Home monitoring of lung function using simple, inexpensive tools to measure peak expiratory flow rate (PEFR) has been possible since the 1970s. Yet although current national and international guidelines recommend monitoring of PEFRs via traditional run charts, their use by both patients and physicians remains low. The role of statistical process control (SPC) theory and charts in the serial monitoring of lung function at home were explored and applied to the direct care of patients with asthma. The method represents an integration of collective professional and improvement knowledge with the related disciplines of continual improvement, SPC, system thinking/system dynamics, paradigms, and the learning community/organization.

CASE STUDIES

Use of PEFR control charts for four patients cared for at the Asthma-Allergy Clinic and Research Center (Shreveport, La) is described. The key to good asthma control is the ability to optimize lung function by reducing the variation between serial lung function measurements and thereby generate a safe range of function. Knowledge of the type of variation (special cause or common cause) in the system helps in focusing clinical decision making. Case 4, an 11-year-old boy, for example, shows how control charts were used to learn the effects of a new inhaled corticosteroid. Comparison of the last 14 days of baseline and the last 14 days of open label use of the inhaled corticosteroid showed an obvious improvement in actual PEFR values--which a run chart or comparison of means would have easily demonstrated. The control chart showed that this child's care process at baseline was functionally at risk for severe asthma (46% personal best) and that the effect of the new medication not only elevated the mean function but shifted the range of function from 46%-72% personal best to 78%-102% personal best. At this new range of function the patient's system of care was not capable of delivering values that are at risk for severe asthma. Unless the range of function the change in care is capable of producing is specifically quantitated, misinterpretation of improvement data can occur.

DISCUSSION

Developing the concept of the PEFR control chart involved examining and challenging traditional mental models for monitoring PEFR at home in the care of asthma, acquiring a better understanding of the workings of dynamic systems and with system thinking, and sharing what was learned with patients and seeking their input.

CONCLUSIONS

The PEFR control chart employs an interesting statistical platform that enables the integration of knowledge of serial measurements and knowledge of the variation between those measurements into a tool with which to better assess the asthma care process being followed. This tool provides clinical insights, practical knowledge, and opportunities unavailable to patients and physicians via traditional PEFR charting.

Peak expiratory flow rate control chart in asthma care: chart construction and use in asthma care

BACKGROUND

The home monitoring of peak expiratory flow rate (PEFR), although recommended in current asthma guidelines, remains seriously underutilized by both patients and physicians. Our assessment is that this is more a statement regarding the inability of current charting methods to fulfill the promises made for PEFR monitoring, rather than a commentary regarding the usefulness of peak expiratory flow rate monitoring per se. We have adapted the theory and charting tool of the discipline of statistical process control to the daily monitoring of PEFR in the care of patients with asthma. Statistical process control charts integrate the actual PEFR values and their day-to-day variation in a manner that permits more informed decision-making. This article introduces our adaptation of statistical process control theory and charts via three case presentations.

OBJECTIVE

Report our experience in the use of statistical process control theory and charting to the monitoring of peak expiratory flow in the care of patients with asthma.

METHODS

Discussion of methodology and case reports.

CONCLUSION

This is the first report of the application of statistical process control (SPC) theory and charting to the home monitoring of peak expiratory flow rate and the clinical decision-making processes involved in the day-to-day care of patients with asthma. SPC charts integrate knowledge of actual serial PEFR measurements with knowledge of their associated serial variation. Our adaptation of this theory and its charting methodology results in a tool that loses nothing provided by the charting methods suggested in current guidelines and, at the same time, provides patient specific, statistically driven signals of significant change; facilitates identification of the reason(s) for the change in PEFR; predicts the range in which future function will occur; permits decision-making and care to be provided in an anticipatory manner; and, importantly, permits the early identification of the functionally at-risk patient. This report demonstrates that home monitoring of peak expiratory flow is a robust tool whose usefulness in the care of patients with asthma has been limited more by the paradigm in which we have required it be used than by any of the limitations of the measurement per se.

A multivariate model for predicting respiratory status in patients with chronic obstructive pulmonary disease

OBJECTIVE

To develop and validate a multivariate model for predicting respiratory status in patients with advanced chronic obstructive pulmonary disease (COPD).

DESIGN

Prospective, double-blind study of peak flow monitoring.

SETTING

Albuquerque Veterans Affairs Medical Center.

PATIENTS

Male veterans with an irreversible component of airflow obstruction on baseline pulmonary function tests.

MEASUREMENTS

This study was conducted between January 1995 and May 1996. At entry, subjects were instructed in the use of the modified Medical Research Council Dyspnea Scale and a mini-Wright peak flow meter equipped with electronic storage. For the next 6 months, they recorded their dyspnea scores once daily and peak expiratory flow rates twice daily, before and after the use of bronchodilators. Patients were blinded to their peak expiratory flow rates, and medical care was provided in the customary manner. Readings were aggregated into 7-day sampling intervals, and interval means were calculated for dyspnea score and peak expiratory flow rate parameters. Intervals from all subjects were then pooled and randomized to separate groups for model development (training set) and validation (test set). In the training set, logistic regression was used to identify variables that predicted future respiratory status. The dependent variable was the log odds that the subject would attain his highest level of dyspnea in the next 7 days. The final model was used to stratify the test set into "high-risk" and "low-risk" categories. The analysis was repeated for 3-day intervals.

MAIN RESULTS

Of the 40 patients considered eligible for study, 8 declined to participate, 4 could not master the technique of peak flow monitoring, and 6 had no fluctuations in their dyspnea level. The remaining 22 subjects form the basis of this report. Fourteen (64%) of the latter completed the 6-month protocol. Data from the 8 who were dropped or died were included up to the point of withdrawal. For 7-day forecasts, mean dyspnea score and mean daily prebronchodilator peak expiratory flow rate were identified as predictor variables. The adjusted odds ratio (OR) for mean dyspnea score was 2.71 (95% confidence interval [CI] 1.79, 4.12) per unit. For mean prebronchodilator peak expiratory flow rate, it was 1.05 (95% CI 1.01, 1.09) per percentage predicted. For 3-day forecasts, the model was composed of mean dyspnea score and mean daily bronchodilator response. The ORs for these terms were 2.66 (95% CI 2.06, 3.44) per unit and 0.980 (95% CI 0.962, 0.998) per percentage of improvement over baseline, respectively. For a given level of dyspnea, higher pre-bronchodilator peak expiratory flow rate and lower bronchodilator response were poor prognostic findings. When the models were applied to the test sets, "high-risk" intervals were 4 times more likely to be followed by maximal symptoms than "low-risk" intervals.

CONCLUSIONS

Dyspnea scores and certain peak expiratory flow rate parameters are independent predictors of respiratory status in patients with COPD. However, our results suggest that monitoring is of little benefit except in patients with the most advanced form of this disease, and its contribution to their management is modest at best.

Patient compliance with peak flow monitoring in chronic obstructive pulmonary disease

BACKGROUND

The factors affecting patient compliance with peak flow monitoring in advanced chronic obstructive pulmonary disease (COPD) were examined using a prospective, blinded study.

METHODS

Twenty-eight male veterans were instructed in the use of an electronic, hand-held peak flow meter and the modified Medical Research Council dyspnea scale. They then entered a 6-month monitoring phase in which they recorded a dyspnea score once daily and peak expiratory flow rates twice daily, before and after bronchodilator use. The meter displays were disabled so that the patients were blinded to their values. Medical care was provided in the customary manner. Compliance was defined as the ratio of recorded values to all values specified by the protocol, exclusive of those missing due to circumstances beyond the patient's control.

RESULTS

Of 40 patients who met the entry criteria for this study, 8 refused to participate and 4 could not master the technique. The remaining 28 patients were enrolled. Overall, 25 (63% of those eligible) adhered to the protocol until its conclusion or until they became unable to comply because of medical or social problems. Compliance was 89.8+/-15.0%. Of those followed for longer than 150 days, linear regression showed that only one patient had a decline in compliance over time (r=0.84, P=0.04). Compliance was lower in the afternoons (P < 0.001) and on days with higher dyspnea scores (P < 0.001). No other clinical factors had an effect on patient measurements.

CONCLUSIONS

A substantial proportion of patients with advanced COPD can be trained in the technique of peak flow monitoring. Compliance is high if patients are enrolled in a long-term, structured program of supervision and periodic retraining.

Bronchial lability and responsiveness in school children born very preterm

We evaluated bronchial lability and responsiveness in 29 prematurely born children (birth weight < 1,250 g) 8 to 14 yr of age, 12 with histories of bronchopulmonary dysplasia (BPD). Flow-volume spirometry, a bronchodilator test, and histamine challenge at the office and home monitoring of peak expiratory flow (PEF) values twice daily for 4 wk with and without a beta2-agonist were performed with a novel device, the Vitalograph Data Storage Spirometer. The spirometric values at the office and the results of home monitoring were compared with those for a control group of children born at term. All spirometric values except FEV1/FVC were significantly lower in the BPD group than in the non-BPD group (p < 0.0001). Ten children (83%) in the BPD group and four (24%) in the non-BPD group had subnormal spirometric values at the office, indicating bronchial obstruction. Of the children with obstruction, 79% reported respiratory symptoms during the preceding year, and 57% had increased diurnal PEF variation and/or responded to administration of a beta2-agonist during home monitoring or at the office. The BPD children were significantly more responsive to histamine than the non-BPD children (p = 0.002). All spirometric values were significantly lower in both preterm groups than in the control group born at full term (p < 0.01). In conclusion, regardless of BPD, bronchial obstruction, bronchial lability, and increased bronchial responsiveness are common in prematurely born children of school age.

Chronic respiratory symptoms, skin test results, and lung function as predictors of peak flow variability

We examined how chronic respiratory symptoms, reported in a questionnaire, and results of skin prick tests and spirometry predicted variability in peak expiratory flow (PEF) among 6-12-yr-old children (n = 1,854). After characterization with skin tests and spirometry, children were followed for 2-3 mo during the winter of 1993-1994. Peak expiratory flow was measured daily in the morning and evenings. Children with asthmatic symptoms (wheeze and/or attacks of shortness of breath with wheeze in the past 12 mo and/or ever doctor diagnosed asthma) had a greater variation in PEF than children with dry nocturnal cough as their only chronic respiratory symptom. Similarly, doctor-diagnosed asthma was associated with a greater variation in PEF, also among children with asthmatic symptoms. Peak flow variability increased with an increasing number of symptoms reported in the questionnaire. Atopy, positive skin test reactions to house dust mite and cat and lowered level (as % of predicted) in FEV1 and in MMEF were also associated with an increased variation in PEF. All the differences were observed in both diurnal and day-to-day variation in PEF. In conclusion, chronic respiratory symptoms reported in a questionnaire, spirometric lung function and skin prick test results among asthmatic children predicted variation in PEF measured during a 2-3 mo follow-up. The difference in morning PEF coefficient of variation (CV) between children with asthmatic symptoms and children with cough only was somewhat bigger in girls than in boys. The effect of atopy on morning PEF CV was somewhat bigger in young than in older children.

FEF25-75 as a marker of airway obstruction in asthmatic children during reduced mite exposure at high altitude

Sensitivity of forced expiratory flow between 25% and 75% of the vital capacity (FEF25-75) in detecting airway obstruction was investigated in 14 children with mild-moderate asthma, allergic to house dust mites, while at high altitude (1756 m). Forced vital capacity (FVC), forced expiratory volume in 1 sec (FEV1), FEF25-75, and peak expiratory flow (PEF) were measured every 2 weeks for 12 weeks (total, 84 measurements). The presence or absence of wheezing at the chest auscultation was ascertained before each test. During the study period, a significant improvement of both mean (SD) FEF25-75 [61 (12)% vs. 68 (11)% of the predicted value, p = 0.005] and PEF [95 (16)% vs. 103 (13)%, p = 0.002] was observed. FEV1 changed only marginally [82 (7)% vs. 86 (6)%, p = 0.05]. Wheezing was present on 12/84 occasions. Wheezing was associated with abnormal FEF25-75 values on most occasions but not with abnormal FEV1 or PEF. FEF25-75 was decreased on 51% of days in which wheezing was absent. FEV1 and PEF were, respectively, normal in 69% (p < 0.0001) and 92% (p < 0.0001) of measurements in which FEF25-75 was abnormal. These results suggest that FEF25-75 may be considered a good indicator of airflow obstruction and a sensitive marker of respiratory improvement in asthmatic children during reduced antigen exposure.

Short-term compliance with peak flow monitoring: results from a study of inner city children with asthma

The objective of the study was to assess the feasibility of initiating daily peak flow monitoring in a research study of asthma in inner city children. We performed a descriptive study of patterns of peak flow monitoring in children randomized to receive a simple mini-Wright (SM) or an electronic recording meter (ERM). The ERM served as a "covert" meter, providing objective documentation of actual peak flow use. Sixty-five Hispanic or African-American children, ages 5-9 years, with a history of physician-diagnosed asthma participated in the study. All children resided in census tracts with 40% or more of the population living at or below the poverty level. Subjects were instructed to use a peak flow meter (the SM or ERM) at least twice daily over a 3 week period, and to record peak flow values in a paper diary. Subjects who received the ERM were not made aware that measurements were also recorded electronically. Differences in patterns of use of the SM and ERM were assessed with the Wilcoxon signed rank test and Wilcoxon sum rank test. Adherence to peak flow monitoring was evaluated by comparing the percent days with missing values in the manually completed diary with those obtained by computer record. The Friedman statistic was used to compare changes in compliance (percent of days with missing peak flow entries) over time. Accuracy of peak flow readings was assessed by comparing the manual and electronic recordings with paired and unpaired t-tests and with Pearson product moment correlations. The percent of days with missing peak flow entries on diaries increased from 1.4% to 10.6% from the first to third week of monitoring (P < 0.004). The ERMs indicated a significantly greater percent of missing data than did the manual records (P < 0.0002). The difference in the percent of missing data for the electronic and manual records was most notable during the third study week, when the ERM and the manually completed records indicated that 52% and 15% of days, respectively, were without peak flow measures. Large inter-subject variations in the relationship between manually and electronically recorded peak flow measurements were observed, suggesting that errors in reading and transcribing peak flow rates occur in a subset of asthmatics. We conclude that children and caretakers in the inner city may have considerable difficulty initiating and maintaining peak flow recordings. Data obtained by manual records may considerably overestimate actual use. Compliance with monitoring decreases markedly between the first and third week of monitoring.

Peak expiratory flow variation and bronchial hyperresponsiveness in asthmatic children during periods of antigen avoidance and reexposure

Changes of diurnal variation of peak expiratory flow rate (%PEF variation) and their relationship with bronchial hyperresponsiveness (BHR) to methacholine (PC20) were evaluated in 12 children with mild-to-moderate asthma and house-dust mite allergy, during successive periods of stay in a mite-free environment at high altitude (1756 m) and at their home at sea level. The children remained at the high altitude from October until the end of December; then they spent a 3-week period at home and returned to high altitude residence in January. PEF was measured daily, in the morning and in the evening, during the 3 months' stay at high altitude and them for 10 days after the return in January. PC20 was assessed in 8/12 children, once a month from October to December, and at the return in January. Mean absolute PEF values did not change significantly throughout the study. From October to December, patients showed a significant decrease of mean %PEF variation (P = 0.04), while PC20 showed an increase (P = 0.05). After the 3 weeks at home, both %PEF variation (P = 0.03) and PC20 (P = 0.05) significantly worsened. The correlation between PC20 values and mean %PEF variation in the 2 days before and after each methacholine test was r = -0.63 (P = 0.001). Our data suggest that there is a beneficial effect of a prolonged stay in a mite-free environment, on both PEF variability and BHR, also in asthmatic children with good pulmonary function. PEF variability and bronchial responsiveness to methacholine were significantly correlated also for small changes of the two variables.

[Measurement of peak expiratory flow in young children: comparison of four portable equipments]

BACKGROUND

Peak expiratory flow (PEF) monitoring is seldom used in young children because peak flow meter normal values are needed for children less than 7 years old.

POPULATION AND METHODS

PEF was measured in 152 non asthmatic school children, aged 2.9 to 14.5 years with four peak flow meters (Assess, DHS, Vitalograph, MiniWright). Calibration of these peak flow meters were performed with flows ranging from 100 to 700 l/min with a calibration syringe.

RESULTS

Calibration demonstrated the excellent linearity of each device but there was a slight overestimation by DHS and MiniWright, and a slight underestimation by Vitalograph and Assess. PEF measured with the four devices was better linearly correlated with height (r = 0.72 to 0.77) than with age. Differences similar to calibration have been found between the four linear regressions.

CONCLUSION

These results indicate that PEF can be used in young children less than 7 years old. It is necessary to always use the same peak flow meter for a child.

Ambulatory monitoring of peak expiratory flow. Reproducibility and quality control

Eighty-five children and 230 adults from a population study performed ambulatory peak flow readings three times a day for 1 to 2 weeks following a home visit. Three peak expiratory flow (PEF) readings were reported for each of 5,809 test sessions. Within each test session, the third maneuver most frequently (40% of the time) gave the highest PEF reading. This did not vary throughout the day. In subgroups of children and women with a history of asthma or asthma symptoms (hereinafter referred to as "asthma"), the first maneuver during the evening test sessions more frequently gave the highest readings. However, maneuver-induced bronchospasm occurred during less than 5% of the test sessions in both subjects with asthma and in other subjects. The within test session PEF reproducibility was good: overall, the highest and second highest reading matched within one division (10 L/min) 73% of the time and within 30 L/min (9% of the reading) 95% of the time. The best reproducibility was noted after the first two days of testing, during evening and bedtime test sessions (vs morning), and in girls and men. In the group with at least 2 weeks of testing, the coefficient of repeatability (CR) for the week-to-week PEF lability index was 10% for healthy adults and 17% for healthy children. As expected, repeatability was not as good for adults with asthma (CR = 17%) and children with asthma (CR = 28%).

Peak expiratory flow rate variability in population surveys. Does the number of assessments matter?

We investigated the effect of reducing the number of daily peak expiratory flow (PEF) measurements on (1) the amplitude of PEF variability and (2) the relationships of this amplitude to bronchial reactivity to methacholine. One hundred seventeen workers (mean age = 38.7 years +/- 9.5; men = 86.3%) recorded their highest of three PEF measurements, every 3 waking hours, ie, 5 times a day, for 7 days, each using a newly purchased peak flowmeter (Vitalograph), and underwent methacholine challenge tests. The variability of PEF of each subject was expressed using the three sets of indices: amp%mean, ie, highest of the daily measurements considered minus the lowest/mean x 100, averaged over 6 days from the second to the seventh, amp%highest (same as amp%mean, but with the highest daily measurements as denominators) and SD%mean (calculated initially as single measures using the data of the 6 days considered, with standard deviation (SD) of each subject's PEF measurements). For each set, we used the indices constructed with the five daily measurements of each day (gold standard), with the first, third, fourth, and fifth, the first, third, and fourth, the first and third, and the first and fourth. The PEF variability was significantly reduced when reducing the number of daily measurements, only when the amp%mean and the amp%highest sets were used. No decrease was observed with the SD%mean set of indices, and SD%mean constructed with the first, third, fourth, and fifth daily measurement was satisfactory. Whatever the sort of index used, three daily measurements were sufficient to identify the group of subjects with excessive variability in relation to methacholine reactivity.

Peak expiratory flow values in children relative to the degree of atmospheric air pollution

The purpose of the study was to determine peak expiratory flow (PEF) values in children from three regions with different degrees of atmospheric pollution. The study included 1415 healthy children aged 7-9 years. In each child five measurements of PEF (1/min) were performed with a Vitalograph. The highest result was considered. The greatest degree of airway resistance, as reflected in low PEF values, was noted among children living in the Upper Silesian Industrial Region and in the Olkusz region where the degree of atmospheric pollution is high compared with Zarki.

Comparison between peak expiratory flow rates (PEFR) and FEV1 in the monitoring of asthmatic subjects at an outpatient clinic

Peak expiratory flow rate (PEFR) monitoring is often used alone in evaluating bronchial caliber and the response to a bronchodilator in the assessment of asthmatic subjects. A 15% change in airway caliber has been proposed as the criteria for modifying treatment. Our aim was to determine if changes in PEFR from one visit to the next can adequately evaluate changes in airway caliber as assessed by FEV1, which is considered the gold standard, and to identify the characteristics of subjects whose evaluations were inadequate. This was a retrospective study of 197 asthmatic subjects seen regularly at an outpatient clinic for whom FEV1 and PEFR assessments, prebronchodilator and postbronchodilator, were available for two visits. There was a high correlation between PEFR and FEV1 (in absolute value or percent predicted) (r = 0.83 and r = 0.75). However, 24 of 56 (43%) of those who had a change in FEV1 of 15% or more between two visits (mean change [%] +/- SD, range [best-lowest/best] = 20.9 +/- 5.1%, 15 to 36%) showed changes in PEFR of less than 15% (6.7 +/- 6.5%, 8.0 to 13.9%). On the other hand, 14 of 42 (33%) subjects with changes in FEV1 of less than 15% (9.8 +/- 3.2%, 1.1 to 13.8%) had changes in PEFR of 15% or more (22.2 +/- 10.9%, 16 to 35%). This discrepancy was not related to differences in baseline FEV1, control status, or the relationship between changes in FEV1 and PEFR in response to a bronchodilator. In conclusion, assessment of airway caliber through PEFR monitoring may not be valid in some asthmatic subjects and can often lead to underestimation or overestimation of changes in FEV1. None of the explanations considered made it possible to identify these subjects.

Pulmonary function in infants and children

The assessment of pulmonary function in infants and children with lung disease can add substantially to their diagnosis and management. This article is a practical review of techniques such as peak flow measurement and spirometry which can be performed in the home or office setting. More complex methods such as airway challenge and infant lung function testing techniques also are discussed.

Physiologic measures: pulmonary function tests. Asthma outcome

When the effectiveness of asthma interventions are evaluated in the research setting, the physiologic manifestation of asthma-variable airways obstruction-is always objectively measured by some of the following pulmonary function tests: (1) Baseline spirometry gives a highly accurate "snapshot" of asthma severity and the degree of airways obstruction. The FEV1, derived from spirometry, is the most reproducible pulmonary function parameter and is linearly related to the severity of airways obstruction. There are no contraindications for the test, spirometers are widely available at reasonable cost, and methods and result interpretation are comprehensively standardized. (2) The post-bronchodilator FEV1 measures the best lung function that can be achieved by bronchodilator therapy on the day of the visit and therefore is a more stable measure in asthmatics than comparing visit-to-visit baseline FEV1. Although a positive acute response to bronchodilator helps to confirm the diagnosis of asthma, the degree of bronchodilator reversibility from visit-to-visit (change in reversibility) is not a useful index of asthma outcome. (3) Airway responsiveness (bronchial challenge) measures the degree to which an individual withstands nonspecific stimuli that trigger asthmatic attacks. The methacholine challenge test is safe and requires less than an hour, but it requires more technical skill than baseline spirometry and is contraindicated in some situations. (4) Ambulatory monitoring, using peak flow meters or hand-held spirometers, provides multiple measurements of the degree of obstruction for days to weeks in the patient's natural setting. PEF meters are very inexpensive and almost all asthmatics can use them, but PEF results are less reliable than the FEV1. The often asymptomatic obstruction of an asthmatic has both short-term (within a day and day-to-day) and longer-term variations that are triggered by naturally occurring stimuli. These changes are measured by PEF lability but not by spirometry during clinic visits. (5) Other pulmonary function tests, such as absolute lung volumes and airways resistance, may provide confirmatory data, but the instruments are large, expensive, and technically demanding. The results of all the above pulmonary function tests are significantly correlated with each other and with symptom scores and medication use in large groups of patients with widely varying degrees of asthma severity. Since a "gold standard" with which to measure asthma severity does not currently exist, all of these tests contribute an additional amount of unique information when measuring asthma outcome in a clinical trial.

Multipollutant exposures and health responses to particulate matter

Epidemiological methods provide opportunities to study interactions of pollutants in complex environments. During the study of health and the environment and the evaluation of particulate matter in Tucson, we found that type, location, and temporality of particulate matter exposures were critical with respect to the various interactions that related to health effects. Indoor particulate matter interacted with other components of particulate matter found in tobacco smoke, as evidenced by lung function. The interaction of environmental tobacco smoke with indoor formaldehyde caused various symptoms. Other interactions occurred between indoor and outdoor forms of particulate matter, which caused symptoms in some of the subjects.