Standardization of ambulatory peak flow monitoring: the importance of recent beta2-agonist inhalation

Control charts demonstrated limited utility for the monitoring of lung function in asthma

OBJECTIVE

Statistical process control charts have been advocated for use in monitoring of lung function in asthma. We aimed to evaluate their application in asthma using existing data from a randomized trial.

STUDY DESIGN AND SETTING

Patients on optimal inhaled corticosteroid/bronchodilator therapy (n=81) were randomized to continue the same or change to corticosteroid alone. Baseline statistical control was assessed from 20 days of electronically recorded lung function (peak expiratory flow [PEF], forced expiratory volume in one second [FEV(1)]). The ability to detect lung function changes was assessed during 10 days after randomization.

RESULTS

PEF measurements were in statistical control during baseline for only 59-79% of patients for different combinations of five control chart rules (e.g., Rule 1: >3 standard deviations outside mean and 95% expected to be in control), with similar proportions for FEV(1). After randomization, among those previously in statistical control, Rule 1 signaled lower FEV(1) for 35% of patients randomized to treatment change compared with 6% continuing baseline treatment (P=0.004). Control charts performed poorly for PEF, signaling a decrease for 8% of patients randomized to treatment change compared with 11% continuing treatment (P=0.7). A paradoxical increase was signaled for many patients continuing treatment.

CONCLUSION

Control charts may not be suitable for use in many patients with asthma.

Daily mood, shortness of breath, and lung function in asthma: concurrent and prospective associations

OBJECTIVE

Previous asthma diary studies have yielded equivocal findings on concurrent associations between lung function and mood, and prospective associations have rarely been explored. We therefore examined concurrent and prospective associations between daily mood, shortness of breath, and lung function, and studied between-individual variability and stability of concurrent associations across different times of the day.

METHOD

Twenty asthma patients and 20 healthy controls recorded their positive and negative mood, shortness of breath, physical activity, peak expiratory flow (PEF) and forced expiratory volume in the first second (FEV(1)) using an electronic pocket spirometer with diary functions three times per day for about 21 days.

RESULTS

For both groups, PEF showed positive concurrent associations with ratings of various mood states, whereas FEV(1) was only associated with positive mood. Both indices correlated negatively with shortness of breath. Within-individual concurrent associations varied significantly in both groups and their stability varied across time of the day, with overall higher stability for associations with shortness of breath in asthma and PEF for both groups. Prospectively, higher shortness of breath consistently predicted lower lung function later during the day and on the subsequent day.

CONCLUSION

The relationship between normal mood variations and lung function is highly variable across individuals and times of the day, limiting the predictive value of average group associations. Shortness of breath is predictive of future lung function decline in asthma. Future longitudinal research should focus on extreme emotional states, effort-independent measures of lung function, and additional indicators of asthma control.

Outpatient monitoring of asthma

Monitoring asthma outcomes is an essential step to the successful implementation of national asthma guidelines. Symptoms, airflow obstruction and exacerbations can be monitored by patients with asthma and by physicians. Patients who practise self-monitoring in conjunction with use of a written action plan and regular medical review have significantly fewer hospitalizations, emergency room visits and lost time from work. Additional monitoring tools are under evaluation, and these include measures of airway responsiveness, airway inflammation, and Internet-based monitoring systems.

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.

Worsening of asthma in children allergic to cats, after indirect exposure to cat at school

Exposure to cat allergen at school might exacerbate symptoms in asthmatic children with cat allergy. To study this, we identified 410 children, 6-12 yr of age, who were being treated for asthma (inhaled steroids and beta-agonists), were allergic to cats, and had no cat at home. Peak expiratory flow (PEF), asthma symptoms, medication, fever and/or sore throat, and contact with furred pets were recorded twice daily during the last week of summer holidays and the second and third weeks of school. The number of cat owners in each class was recorded. Ninety-two children with asthma reported no contact with furred pets. Among these, children who attended classes with > 18% (median value) cat owners reported significantly decreased PEF, more days with asthma symptoms, and increased use of medication after school started. Those in classes with < or = 18% cat owners reported no change. Children in classes with many cat owners ran a 9-fold increased risk of exacerbated asthma after school start compared with children in classes with few cat owners, after adjusting for age, sex, and fever and/or sore throat. Thus, asthma symptoms, PEF, and the use of asthma medication in children with cat allergy may be affected by indirect cat exposure at school.

Monitoring the patient with asthma: an evidence-based approach

The monitoring of symptoms, airflow obstruction, and exacerbations is essential to asthma management. Patients who practice self-monitoring in conjunction with use of a written action plan and regular medical review have significantly fewer hospitalizations, emergency department visits, and lost time from work. Either symptom monitoring or peak expiratory flow monitoring is satisfactory, provided the results are interpreted with reference to the patient's own baseline asthma status. Regular monitoring by physicians also improves health outcomes for patients, provided the physician is systematic and monitors control, medications, and skills at regular intervals. Additional monitoring tools are under evaluation, and these include measures of airway responsiveness, airway inflammation, and Internet-based monitoring systems. Administrators need to monitor the quality and cost of care, as well as compliance with national management guidelines. Assessment of the hospitalization rate and regular audit may achieve these aims in the hospital setting. The best way to assess and monitor asthma in primary care remains an unresolved yet crucial issue because primary care physicians manage the vast burden of illness caused by asthma. Monitoring asthma outcomes is an essential step toward the successful implementation of national guidelines for the management of asthma.

Airway responsiveness to acetaldehyde in patients with asthma: relationship to methacholine responsiveness and peak expiratory flow variation

BACKGROUND

Although airway hyperresponsiveness to inhaled acetaldehyde has been documented in Japanese patients with asthma, the response to this bronchoconstrictor agent has never been studied in Caucasians.

OBJECTIVES

The objectives of the study were to determine differences in airway responsiveness to acetaldehyde between asthmatic and healthy subjects, and to examine the relationship between acetaldehyde responsiveness and the variability of peak expiratory flow (PEF).

METHODS

The response to methacholine and acetaldehyde challenges was measured in 81 non-smoking adults (61 asthmatics and 20 normal controls). Subjects recorded PEF morning and evening for 14 days. The response to both bronchoconstrictor agents was measured by the PC20 (provocative concentration required to produce a 20% fall in FEV1). PEF variation was expressed as amplitude percentage mean, and as low percentage best (lowest PEF expressed as a percentage of the best PEF recorded).

RESULTS

The two types of challenge yielded a similarly high level of sensitivity (100% for methacholine and 92% for acetaldehyde) and specificity (90 and 100%, respectively) to distinguish between asthma and controls. Asthmatic subjects were on average 265-fold less sensitive to acetaldehyde than to methacholine. PC20 acetaldehyde correlated weakly but significantly with both indices of PEF variation (amplitude percentage mean: rho = - 0.36, P = 0. 004; low percentage best: rho = 0.42, P = 0.001).

CONCLUSIONS

These results indicate that airway hyperresponsiveness to acetaldehyde is a sensitive and specific indicator for separating asthmatic and normal subjects. Airway responsiveness to methacholine or acetaldehyde and PEF variation are not reflecting the same pathophysiological process in the airways.

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.

Differences between asthma exacerbations and poor asthma control

BACKGROUND

Increased variation in peak expiratory flow (PEF) is characteristic of poorly controlled asthma, and measurement of diurnal variability of PEF has been recommended for assessment of asthma severity, including during exacerbations. We aimed to test whether asthma exacerbations had the same PEF characteristics as poor asthma control.

METHODS

Electronic PEF records from 43 patients with initially poorly controlled asthma were examined for all exacerbations that occurred after PEF reached a plateau with inhaled corticosteroid treatment. Diurnal variability of PEF was compared during exacerbations, run-in (poor asthma control), and the period of stable asthma before each exacerbation.

FINDINGS

Diurnal variability was 21.3% during poor asthma control and improved to 5.3% (stable asthma) with inhaled corticosteroid treatment. 40 exacerbations occurred in 26 patients over 2-16 months; 38 (95%) of exacerbations were associated with symptoms of clinical respiratory infection. During exacerbations, consecutive PEF values fell linearly over several days then improved linearly. However, diurnal variability during exacerbations (7.7%) was not significantly higher than during stable asthma (5.4%, p=0.1). PEF data were consistent with impaired response to inhaled beta2-agonist during exacerbations but not during poorly controlled asthma.

INTERPRETATION

Asthmatics remain vulnerable to exacerbations during clinical respiratory infections, even after asthma is brought under control. Calculation of diurnal variability may fail to detect important changes in lung function. PEF variation is strikingly different during exacerbations compared with poor asthma control, suggesting differences in beta2-adrenoceptor function between these conditions.