Lung function measures and their relationship to respiratory symptoms in 7- and 8-year-old children

[Lung function testing and assessment of distal airways in asthma]

INTRODUCTION

Small airways are defined (in humans) as those<2mm in diameter.

BACKGROUND

They were originally described as the "quiet zone" of the lungs contributing less than 10% of the total resistance to airflow. Pulmonary function tests remain the most used method to assess distal airway flow limitation.

VIEWPOINTS

However, these tests are limited in adults and also in children because MEF25-75% and FEF50% are highly variable spirometric indices and they depend on vital capacity, which increases with expiratory time in obstructed subjects. There is a need for promising non invasive new tools like the forced oscillation technique to measure resistance. The increased availability of the exhaled fraction of nitric oxide (FeNO) measurement means that this method is accessible and attractive.

CONCLUSION

The production of nitric oxide (NO) can be assessed by measuring the fraction of NO during a prolonged expiration (FENO) or by estimating other parameters of NO exchange including the alveolar NO concentration (CalvNO) and may provide information about small airway inflammation and assist the optimal control of the disease.

Asthma and lung function in a birth cohort at 6-7 years of age in southern Brazil

OBJECTIVE

Asthma and respiratory symptoms are common in children, and many studies have shown associations between childhood symptoms and impaired lung function in adult life. The aim of the present study was to investigate the association of various respiratory symptoms with wheezing patterns (persistent, early, and late-onset) and lung function, as well as to determine whether lung function was associated with atopy or with demographic, socioeconomic, environmental, and gestational factors, in a birth cohort at 6-7 years of age.

METHODS

The target population consisted of children aged 6-7 years from a birth cohort of 5,304 children born in southern Brazil in 1993. For this follow-up evaluation, 532 of those children were randomly selected, and a sub-sample was submitted to spirometry and skin prick tests. A questionnaire was administered to the parent(s) or legal guardian(s) of each child.

RESULTS

Spirometric values were lower in the children with respiratory symptoms or asthma. Mean forced expiratory volume in one second/forced vital capacity ratio (FEV1/FVC ratio) was lower in children with any of the following: current wheezing and asthma; asthma ever; four or more episodes of wheezing within the preceding 12 months; sleep disturbance due to wheezing; and exercise-induced wheezing. Persistent wheezing was associated with lower FEV1/FVC ratio. After multiple linear regression, exercise-induced wheezing was also associated with reduced FEV1/FVC ratio. Nonwhite skin color and wheezing severe enough to limit speech were associated with lower FEV1.

CONCLUSIONS

Children with persistent wheezing and symptoms of severe asthma have impaired lung function at 6-7 years of age.

Childhood respiratory illness and lung function at ages 14 and 50 years: childhood respiratory illness and lung function

BACKGROUND

Although childhood respiratory tract infections and low birth weight have both been associated with reduced adult lung function, little is known about the timing of these associations during life. We used data from the Newcastle Thousand Families Study to examine how these and other factors influenced FEV(1) at age 14 years and between 14 and 49 to 51 years.

METHODS

Detailed information was collected prospectively during childhood. At age 14 years, 252 members of the cohort were recruited into a case-control study of respiratory health, which included measurement of FEV(1). One hundred twenty-two of these were measured again at age 49 to 51 years. Linear regression models were used to examine cross-sectional and longitudinal influences on FEV(1).

RESULTS

Lower height (P < .001), lower BMI (P < .001), being breast fed for less than 4 weeks (P = .028), childhood history of severe respiratory illness (P = .014), childhood history of asthma (P = .004), childhood history of TB (P = .023), and birth into a lower social class (P = .049) were all significant independent predictors of lower FEV(1) at 14 years of age. Correspondingly, being a women (P < .001), and having a higher FEV(1) at age 14 years (P < .001), a lower standardized birth weight (P = .025), a greater lifetime number of cigarettes smoked (P = .007), and a childhood history of severe respiratory illness (P = .047) were all independently associated with a greater decline (or a smaller increase) in FEV(1) between age 14 and 49 to 51 years.

CONCLUSIONS

This study suggests that the change in FEV(1) between youth and middle age depends on several factors acting throughout life, including FEV(1) in adolescence, sex, cigarette smoking, birth weight, and childhood respiratory health.

Utilization of the pulmonary function test laboratory in the evaluation of respiratory disorders in the Al-Amiri Hospital: a secondary medical center

OBJECTIVE

The aim of this study was to describe the current use of pulmonary function tests (PFT) and the degree of matching between the diagnoses at referral and after the test.

SUBJECTS AND METHODS

A pre-test questionnaire was administered to 464 (5-88 years) patients referred to the PFT laboratory followed by a complete PFT test. The results of the patients' tests were analyzed in terms of the diagnosis before the test, its relation to symptoms, and the rate of concordance between the diagnoses before and after the test.

RESULTS

The most referrals were from the medical Outpatient Department; 61%) and the most frequent diagnosis before the test was asthma (31.8%). Of the 464 patients, 34% were currently smoking cigarettes, and the most common symptoms were chronic dyspnea (30.2%) and chronic cough (19.6%). The chronicity of symptoms showed some association with the diagnosis before PFT in the case of chronic obstructive pulmonary disease (COPD) showing the symptom of dyspnea (p = 0.05), and COPD and restrictive lung disease with cough (p < 0.05). The overall rate of concordance in matching diagnoses before and after the test was 60.4% by consultant physicians and 51.9% by non-consultants, with an overall rate of 55% by all physicians.

CONCLUSION

Our findings show that there should be better utilization of the PFT laboratory by physicians in all sub-specialities and there is a need to facilitate its use to make a better functional diagnosis.

Feasibility of school-based spirometry screening for asthma

To determine the feasibility and value of spirometry in school-based asthma screening, spirometry testing was coupled with parent questionnaires in a school-based asthma screening project. Children in grades five to eight of the Catholic school system in Rochester, Minn., performed spirometry with coaching and data acquisition by nurses trained for this activity. Most students completed three tests. For each student, the best test was selected for interpretation. Tests were considered technically unacceptable for screening purposes if the FEV1 was less than 85% and the curve showed evidence of cough, delayed start, poor initial effort, incomplete effort, or non-reproducibility. Students with acceptable tests and FEV1 < 85% as predicted for age, race, and BMI were classified as appropriate for referral for further evaluation of potential asthma. A sensitivity analysis was conducted using different FEV1 thresholds for referral. Children (119, 17.6% of all) with known asthma based on parent-completed questionnaire were not considered for referral. Of the remaining 557 students screened, 535 had technically acceptable tests, and 498 had normal spirometry performance. Using a threshold for referral of FEV1 < 85%, 37 children were candidates for referral for further evaluation of potential asthma. Only four (11%) of these also had questionnaire responses that made them candidates for referral. School-based spirometry screening for asthma is technically feasible but there is little overlap between those who are referral candidates based on spirometry data and those who are referral candidates based on parent-reported symptoms on screening questionnaires. Without further study, spirometry cannot be recommended for school-based asthma screening.

Asthma symptoms, morbidity, and antiinflammatory use in inner-city children

BACKGROUND

Asthma is a major cause of morbidity that disproportionately affects inner-city children. For children with persistent asthma, defined as having asthma symptoms 3 or more days per week or 3 or more nights per month, national guidelines recommend the use of daily antiinflammatory agents. Despite these recommendations, antiinflammatory agents remain underused, particularly in inner-city children with high asthma morbidity.

OBJECTIVES

The objectives of our study were to determine: 1) whether persistent asthma symptoms in inner-city children are related to acute care utilization and to the frequency of acute exacerbations; 2) whether children with persistent asthma are receiving recommended daily antiinflammatory agents; and 3) whether antiinflammatory medication use relates to sociodemographic factors, caretaker self-efficacy, the frequency of primary care visits, and/or measures of quality asthma care.

DESIGN AND METHODS

A 64-item telephone survey was administered between July 1996 and June 1997 to 219 parental caretakers of 2- to 12-year-old children who had been hospitalized with asthma at an inner-city medical center between January 1995 and February 1996. Persistent asthma symptoms were assessed by inquiring about the frequency of daily and nocturnal asthma symptoms over the last 4 weeks. Children's asthma severity was classified by applying the 1997 National Asthma Education and Prevention Program (NAEPP) Asthma Guidelines' severity classification scheme based on the frequency of asthma symptoms. Asthma morbidity was defined as the frequency of acute asthma exacerbations, emergency department visits and hospitalizations. Daily antiinflammatory medication use was compared by sociodemographic factors, caretaker self-efficacy, frequency of primary care visits, and measures of quality asthma home management.

RESULTS

In this sample, quantifying persistent asthma symptoms and applying the NAEPP symptom criteria identified 17% of the children with mild intermittent asthma, 27% with mild persistent asthma and 56% with moderate to severe persistent asthma. There were no differences in the age of the children in the 3 groups (mean age: 6 years). Asthma morbidity, as measured by the number of asthma exacerbations in the last 6 months, was significantly higher in the children with moderate to severe persistent asthma compared with children with mild intermittent asthma (9.8 vs 3.5) or mild persistent asthma (9.8 vs 4.5). In addition, there were significantly more emergency department visits in the moderate to severe group than in the mild persistent (3.05 vs 1.69) or mild intermittent group (3.05 vs 1.76). Lastly, as asthma symptom frequency increased, there were trends toward more hospitalizations and more days hospitalized. Overall, 35% of the 219 families reported giving daily antiinflammatory medications to their child (mostly cromolyn sodium). Of the 181 children (83%) who met NAEPP symptom criteria for persistent asthma, only 39% were receiving daily antiinflammatory treatment. Of the children with symptoms of moderate to severe asthma, only 15% were receiving inhaled steroids in contrast to the guidelines' recommendations. Use of antiinflammatory agents was not related to caretaker sociodemographic factors or self-efficacy scores. Measures of quality asthma home management, which included use of mattress covers, written plans, and peak flow meters, correlated positively with use of antiinflammatory agents. Children whose families reported using daily antiinflammatory medications had more primary care visits in the last 6 months than those children not receiving antiinflammatory medications.

CONCLUSION

Questioning parents about the frequency of their child's asthma symptoms is an important, inexpensive, and readily accessible bedside and office tool that may aid in the detection of persistent symptoms and help direct therapy. Our study suggests that classifying asthma severity by quantifying persistent asthma symptoms, as defined in the NAEPP Guidelines, is a clinically useful tool that relates to asthma morbidity. In our sample of previously hospitalized children with asthma, 83% met 1997 NAEPP symptom criteria for persistent asthma, and yet only 35% were receiving daily antiinflammatory agents. Use of antiinflammatory agents correlated positively with other indicators of quality asthma home management. Additional work is necessary to increase appropriate use of antiinflammatory agents in this population, and in particular, to increase inhaled steroid use for children with moderate or severe symptoms.