Portable Spirometry During Acute Exacerbations of Asthma in Children

Journal of Asthma, 46:122 125, 2009 Copyright C 2009 Informa Healthcare USA, Inc. ISSN: 0277-0903 print / 1532-4303 online DOI: 10.1080/02770900802460522 ORIGINAL ARTICLE Portable Spirometry During Acute Exacerbations of Asthma in Children MELISSA L. LANGHAN, M.D. 1, AND DAVID M. SPIRO, M.D., M.P.H. 2 1 Department of Pediatrics, Section of Pediatric Emergency Medicine, Yale University School of Medicine, New Haven, Connecticut, USA 2 Departments of Emergency Medicine and Pediatrics, Oregon Health and Science University, Portland, Oregon, USA Background. Spirometry is the gold standard for assessment of asthma and is objective and non-invasive. This is a pilot study to evaluate whether portable spirometry can be successfully performed by children in the pediatric emergency department for acute exacerbations of asthma. Methods. We enrolled children more than 6 years of age presenting to an urban pediatric emergency department with a history of asthma during an acute exacerbation. On arrival and after each bronchodilator treatment, vital signs and a clinical score were recorded. Portable spirometry was then performed. Attempts were continued until acceptable and reproducible measurements were obtained or until the patient was unable to perform further attempts. Outcomes included success at spirometry and correlation of spirometry with clinical signs. Results. Thirty-four subjects were enrolled with a median age of 12 years. Ninety-one percent of subjects completed at least one attempt at spirometry. Seventy-three percent of all spirometry attempts were reproducible. Portable spirometry demonstrated increased severity of the exacerbation in comparison to clinical signs and peak expiratory flow. Percent of predicted forced expiratory volume in 1 second, ratio of forced expiratory volume in 1 second to forced vital capacity, and peak expiratory flow are all poorly correlated with degree of wheezing, clinical score, respiratory rate, and oxygen saturation (r <0.5). Conclusion. Portable spirometry can be successfully performed by children with acute exacerbations of asthma in the emergency department and demonstrated greater degrees of airway obstruction than did clinical signs. Spirometry provides objective, non-invasive measurements of the severity of airway obstruction in the emergency department for children with acute exacerbations of asthma. Keywords asthma, spirometry, FEV 1, children, emergency department INTRODUCTION In 2006, 6.8 million children under 18 years of age were affected by asthma with over 4 million of those children having an acute exacerbation of asthma in the preceding 12 months (1). Accordingly, there are numerous annual visits to emergency departments (ED) each year for these episodes (2). In 2007, the National Asthma Education and Prevention Program of the National Heart, Lung, and Blood Institute (NHLBI) defined an exacerbation of asthma as a quantifiable decrease in lung function. Furthermore, they recommend that during an acute exacerbation of asthma objective measures of lung function, such as spirometry should be obtained and monitored (3). The methods by which acute exacerbations of asthma are currently assessed in children in the ED have significant limitations. These include clinical signs, a variety of scoring systems, and peak flow meters. Individual clinical signs have previously been shown to be poorly correlated with the actual degree of obstruction seen in children with asthma (4, 5). To better assess the severity of disease and the need for hospitalization, clinical scoring systems, of which there are more than 18 published in the literature, were developed to combine aspects of the physical examination (6, 7). Scoring systems are easily measured and require no effort on the part This work was presented in a platform at the American Academy of Pediatrics National Conference and Exhibition, October 2006, Atlanta Georgia. Corresponding author: Melissa Langhan, MD, Pediatric Emergency Medicine, Yale-New Haven Children s Hospital, 840 Howard Avenue, New Haven, Connecticut 06520. E-mail: Melissa.Langhan@yale.edu of the patient, thus they are not limited by age or severity of disease. However, a minority of these scoring systems have been validated with objective measures of obstruction. Additionally, clinical scoring systems have not been shown to be generalizable and often have poor interobserver agreement. Peak flow meters, which measure the peak expiratory flow (PEF) during a forced expiratory maneuver, are widely available and inexpensive. They are endorsed by the NHLBI as an objective measurement of lung function to be used during exacerbations of asthma and as part of routine monitoring (3). However, measurements of forced expiration used in the assessment of bronchospasm depend on effort and require significant cooperation by the patient. Children under the age of 7 years are usually unable to coordinate sufficiently to provide reliable results. A limitation of PEF is that it represents flow of air in the larger airways and is thus, imperfectly related to the small airway obstruction seen in asthma (3). Spirometry, or the classic pulmonary function test, is the current gold standard by which to measure airway obstruction. It provides an objective measurement of the severity of asthma during an acute exacerbation, as well as of the reversibility of the obstruction in response to treatment. The forced expiratory volume in one second (FEV 1 ) and the ratio of FEV 1 to the forced vital capacity (FVC) are measurements of airflow and lung volume that are obtained during spirometry and decreased in small airway obstruction (8). Although recent literature has shown that preschool children can perform spirometry with the help of on-screen incentives, these maneuvers depend on both effort and age similar to assessment by peak flow meters (9). Spirometry is typically performed in a pulmonary function laboratory and is thus not 122

SPIROMETRY IN A PEDIATRIC EMERGENCY DEPARTMENT 123 easily accessible to either community or emergency physicians. Portable spirometers have recently become available. These hand-held devices have been shown to provide results similar to those obtained by laboratory-based spirometers and can be used in a variety of settings (10 12). There are no studies assessing the ability to use this device in the evaluation of exacerbations of asthma in children in the ED. The aim of this pilot study was to determine if portable spirometers can be successfully used in children during an acute exacerbation of asthma in a pediatric ED and to describe the correlation between observed clinical symptoms and objective measures of lung function. MATERIALS AND METHODS This cross-sectional study was performed in the pediatric ED of Yale-New Haven Children s Hospital on a convenience sample of subjects from 7 to 21 years of age from December 2004 to November 2006. The Yale-New Haven pediatric ED has an annual census of approximately 31,000 patients and is located in an urban setting. All subjects were enrolled by a single pediatric emergency medicine fellow. This study was approved by the Yale University Human Investigation Committee and written informed consent was obtained before enrollment. Subjects were patients who presented with a self-reported diagnosis of asthma and a chief complaint of wheezing, increased work of breathing, cough, or shortness of breath. Subjects were excluded if they had any clinical or radiographic evidence of pneumonia, a history of either cardiac or other chronic pulmonary disease, were previously enrolled, or had a final diagnosis other than an acute exacerbation of asthma. Basic demographic information was recorded as well as duration of asthma-related symptoms and use of medication in the preceding 24 hours. On arrival and after each bronchodilator treatment, all children had a physical examination to evaluate signs of asthma. The data were then used to calculate the Pulmonary Score (PS), which is a clinical scoring system for asthma described and validated by Smith et al. (13). It is comprised of three components that include (1) wheezing, (2) sternocleidomastoid retractions, and (3) respiratory rate by age. Each component was graded on a 3-point scale with 0 representing the absence of wheezing, retractions, or tachypnea and 3 representing severe wheezing, retractions, or tachypnea. The results were then summed. A score from 0 to 3 represented a mild exacerbation, 4 to 6 a moderate exacerbation, and 7 to 9 a severe exacerbation. The PS was chosen for this study because it was developed with children in a similar age range to our sample and was validated against peak expiratory flow values (13). After the PS was determined, portable spirometry was performed using the EasyOne spirometer with disposable spirettes and EasyScreen with child incentives (NDD Medical Technologies, Zurich, Switzerland). Before the first attempt, the enrolling physician spent 1 to 2 minutes demonstrating how to use the device and performed a forced exhalation maneuver for the subject, then coached the subjects during their attempts. The EasyScreen allowed the portable spirometer to be attached to a laptop and as the subject performed spirometry they visualized a child blowing up a balloon simultaneously. Visual rewards appeared for successful attempts. The spirometer provided feedback to the subjects after each attempt as to how to improve their maneuver to obtain a successful and reproducible attempt. On arrival and after all bronchodilator treatments, each child was asked to use the spirometer until there was sufficient agreement between two measurements as determined by the automated quality assessment of the spirometer or until the patient was unable to tolerate further attempts because of respiratory complaints. This series of attempts is defined as a session. The actual and percent of predicted values for PEF, FEV 1, FVC, and FEV 1 /FVC were recorded for each session. Percent of predicted values were based on the NHANES III reference ranges that incorporated age, weight, height, and ethnicity and were calculated by the device. All bronchodilator treatments were recorded as well as final disposition. Treating physicians were blinded to results of spirometry and thus made decisions regarding patient treatment and disposition independent of study data. The primary outcome was success in performing spirometry. This was defined as a minimum of two acceptable maneuvers and the difference between two FEV 1 values of 200 ml. The spirometer was enabled with automated quality assessment that provided measurements of success and reproducibility. Flow-volume loops of the best forced expiratory maneuvers were recorded and independently reviewed by the enrolling physician. The secondary outcome was correlation between clinical signs of asthma and results of spirometry. According to the NHLBI guidelines, a mild exacerbation was defined as an FEV 1 or PEF 70% predicted, a moderate exacerbation as an FEV 1 or PEF of 40 69% of predicted, and a severe exacerbation as an FEV 1 or PEF <40% of predicted (3). Data were entered into TrialDB, a web-based data management tool supported by Yale University. Statistical analysis was performed in SPSS 14.0 (SPSS Inc, Chicago, IL). Descriptive analyses including mean, median, and range were performed on demographic data and clinical signs. Univariate analysis of covariance was used to evaluate for associations between age, medication use, clinical signs, symptom duration, and success at spirometry. Bivariate correlation was performed using the Spearman rank correlation coefficient to measure the relationship between spirometry and clinical signs. RESULTS A total of 36 patients were enrolled in this study. No patients who were approached for enrollment refused participation. Two patients were excluded for a diagnosis other than asthma. The demographic information is presented in Table 1. Thirty-one of the 34 patients (91%) were able to complete at least one session of spirometry during their stay in the pediatric ED. One patient, age 14 years with a PS of 0 throughout his ED stay, was unable to successfully perform any spirometry maneuvers while in the pediatric ED. Two patients, ages 7 and 15 years and both with clinically moderate exacerbations based on their PS, were able to successfully perform the maneuver on one occasion but could not reproducibly produce their efforts at spirometry during any session. Of the remaining patients, 73% of all attempts at spirometry were

124 M. L. LANGHAN ET AL. successful and reproducible. A mean of two spirometry sessions were completed by each patient during the course of their ED stay (range 1 4). Eighty-one percent of patients successfully completed the majority of all sessions and 52% successfully completed all sessions. There was no difference in the mean age, gender, or race of patients who were able to successfully complete the majority of their spirometry sessions (12.8 years vs. 10.7 years [95% CI 5.1 to 0.8, p = 0.25]]) Successful spirometry attempts were associated with a lower mean respiratory rate (21.4 vs. 28.5, p =.016), a higher oxygen saturation (97.3 vs. 96.5, p = 0.002) and a higher mean percent of predicted FEV 1 /FVC (82.2 vs. 79.6, p = 0.031). There were no significant differences in the percent of predicted FEV 1 (58.7 vs. 49, p = 0.415), percent of predicted PEF (62.8 vs. 51.5, p = 0.252), PS (2.4 vs. 3.7, p = 0.255), or degree of wheezing (2.4 vs. 2.7, p = 0.55) detected before successful attempts compared with unsuccessful spirometry attempts. The median duration of asthma-related symptoms before arriving in the ED was 26 hours (range 1 168 hours). The majority of our patients (85%) received albuterol in the 24 hours before arrival, with a median time of 1 hour (range 0 13 hours). Inhaled steroids were taken by 6 subjects (18%) and oral steroids by 6 subjects (18%) before arrival. On physical examination at arrival, wheezing was severe in 21% and moderate in 29% of patients who had successful and reproducible spirometry. Using the PS, 4% of the subjects had a severe exacerbation (median score 7) and 25% a moderate exacerbation (median score 5). In comparison, of successful spirometry attempts on arrival, 25% of subjects had a severe degree of obstruction and 46% had a moderate degree of obstruction by percent of predicted FEV 1. Based on percent of predicted PEF, 46% had a moderate exacerbation and 17% had a severe exacerbation. These results are shown in Table 2. The PS, degree of wheezing, respiratory rate, and oxygen saturation were all poorly correlated with more objective measures of obstruction including percent of predicted FEV 1, FEV 1 /FVC, and PEF with an r 0.48 (p <0.05) as shown in Table 3. Percent of predicted PEF was shown to poorly correlate with percent of predicted FEV 1 /FVC (r = 0.44), but significantly correlate with percent of predicted FEV 1 (r = 0.86) [p <0.001]. DISCUSSION Portable spirometry can be successfully performed during acute exacerbations of asthma in children in the pediatric ED. Neither the PS, nor individual clinical signs of asthma correlated with more objective measures of airway obstruction, such as percent of predicted FEV 1 or FEV 1 /FVC. Furthermore, both clinical signs of asthma and the PS underestimated the degree of airway obstruction as measured by portable spirometry in a significant number of patients. The severity of the exacerbation as assessed by PEF was similar to FEV 1 but also underestimated severity to a milder degree. The methods by which acute exacerbations of asthma are currently assessed are either subjective or imperfectly related to obstruction in the lower airways. Although spirometry is effort and age dependent, the availability of on-screen child incentives to improve success and reproducibility makes it feasible to use this device in children greater than 2 years of age (14). Several studies have demonstrated that the clinical assessments made by emergency physicians, community pediatricians, and even pediatric pulmonary specialists all underestimated the degree of obstruction in patients with asthma and the addition of spirometry significantly impacted management (12, 15, 16). In the study by Holt, children were able to perform spirometry in a pediatric clinic during at acute exacerbation of asthma similar to the patients in our study population (15). However, in this previous study we are not provided with information as to how severe these exacerbations were. Children arriving in a pediatric ED with acute exacerbations of asthma may have a broader severity of symptoms than that of children presenting to a community clinic. Although peak flow meters are inexpensive and widely available, portable spirometry offers the advantage of obtaining multiple measurements related to lower airway obstruction. Furthermore, the device used in this study was previously validated against laboratory-based pulmonary function tests (11). Although the percent of predicted PEF was shown to be significantly correlated with the percent of predicted FEV 1, this is in large part because the majority of the volume of the FEV 1 is derived from the volume of PEF. However, percent of predicted PEF did not correlate with the ratio of FEV 1 to FVC and overestimated the number of patients with mild exacerbations of asthma. Both devices require coaching by ED staff and multiple maneuvers to document reproducibility, yet there is little extra teaching needed for spirometry making it equally feasible in this setting. The spirettes used by the portable spirometer are individual, disposable, and inexpensive. The automated quality assessment of each attempt, immediate feedback for improvement, and calculation of percent predicted values by the device are other advantages of this tool. One prior study demonstrated that many children assessed with an acute exacerbation of asthma were unable to perform peak flow maneuvers (17). Our data conflict with this report, but it is unclear in that study whether these maneuvers were demonstrated to the subjects before attempt and what coaching or feedback they received. Also, the availability of incentive screens may improve performance of spirometry over peak flow meters. Both the PS and individual clinical signs and symptoms of asthma were poorly correlated with objective measures of obstruction. The correlation between the PS and predicted PEF in this study was only minimally less than that found in its original validation report (13). Whereas only one patient was found to have severe obstruction based on this score, six patients had severe obstruction as measured by FEV 1.As clinicians, we use our physical examination skills to make treatment and admission decisions in children with asthma. These, however, may be underestimating the severity of illness. LIMITATIONS This study is limited by its small size and convenience sample of patients. The availability of one examiner to enroll all patients eliminated the issue of interobserver variability found with clinical assessment and scoring systems. Clinical scores were determined before objective measurements to avoid bias. Although we found that the ability to perform

SPIROMETRY IN A PEDIATRIC EMERGENCY DEPARTMENT 125 spirometry successfully was not effected by age or subjective severity of the exacerbation, we were not sufficiently powered to ensure that these confounders will remain without statistical significance in a larger study. In addition, preschool children were excluded from this study despite recent literature suggesting that younger children can perform spirometry given on-screen incentives. CONCLUSIONS This is the first study to demonstrate that portable spirometry can be used in the evaluation of acute exacerbations of asthma in children in the ED. Overall, spirometry demonstrated increased severity of obstruction in patients with asthma than did a clinical examination or scoring system. Portable spirometry may be a valuable tool to improve the assessment of acute exacerbations of asthma in children, which may affect treatment and admission decisions in the ED. Further studies are needed to evaluate the feasibility of the use of portable spirometry in preschool children as well as its impact on management of children with asthma in the ED. ACKNOWLEDGEMENT James Dziura, Ph.D., provided statistical assistance and Eugene Shapiro, M.D., helped to review this manuscript. An award received from the Friends of the Yale-New Haven Children s Hospital made it possible to purchase the portable spirometer and spirettes used in this study. REFERENCES 1. Bloom B, Cohen RA. Summary health statistics for U.S. children: National Health Interview Survey, 2006. Vital Health Stat 10 2007: 1 79. 2. Mannino DM, Homa DM, Akinbami LJ, Moorman JE, Gwynn C, Redd SC. Surveillance for asthma United States, 1980 1999. MMWR Surveill Summ 2002; 51: 1 13. 3. National Heart, Lung, and Blood Institute. National Asthma Education and Prevention Program Expert Panel Report 3: Guidelines for the Diagnosis and Management of Asthma: US Department of Health and Human Services, National Institutes of Health; 2007. 4. Teeter JG, Bleecker ER. Relationship between airway obstruction and respiratory symptoms in adult asthmatics. Chest 1998; 113: 272 277. 5. Verini M, Rossi N, Dalfino T, Verrotti A, Di Gioacchino M, Chiarelli F. Lack of correlation between clinical patterns of asthma and airway obstruction. Allergy Asthma Proc 2001; 22: 297 302. 6. van der Windt D. Promises and pitfalls in the evaluation of pediatric asthma scores. J Pediatr 2000; 137: 744 746. 7. van der Windt DA, Nagelkerke AF, Bouter LM, Dankert-Roelse JE, Veerman AJ. Clinical scores for acute asthma in pre-school children. A review of the literature. J Clin Epidemiol 1994; 47: 635 646. 8. Spahn JD, Chipps BE. Office-based objective measures in childhood asthma. J Pediatr 2006; 148: 11 15. 9. Nystad W, Samuelsen SO, Nafstad P, Edvardsen E, Stensrud T, Jaakkola JJ. Feasibility of measuring lung function in preschool children. Thorax 2002; 57: 1021 1027. 10. Ezzahir N, Leske V, Peiffer C, Trang H. Relevance of a portable spirometer for detection of small airways obstruction. Pediatr Pulmonol 2005; 39: 178 184. 11. Mortimer KM, Fallot A, Balmes JR, Tager IB. Evaluating the use of a portable spirometer in a study of pediatric asthma. Chest 2003; 123: 1899 1907. 12. Emerman CL, Cydulka RK. Effect of pulmonary function testing on the management of acute asthma. Arch Intern Med 1995; 155: 2225 2228. 13. Smith SR, Baty JD, Hodge D, 3rd. Validation of the pulmonary score: an asthma severity score for children. Acad Emerg Med 2002; 9: 99 104. 14. Vilozni D, Barak A, Efrati O, Augarten A, Springer C, Yahav Y, Bentur L. The role of computer games in measuring spirometry in healthy and asthmatic preschool children. Chest 2005; 128: 1146 1155. 15. Holt EW, Tan J, Hosgood HD. The impact of spirometry on pediatric asthma diagnosis and treatment. J Asthma 2006; 43: 489 493. 16. Nair SJ, Daigle KL, DeCuir P, Lapin CD, Schramm CM. The influence of pulmonary function testing on the management of asthma in children. J Pediatr 2005; 147: 797 801. 17. Gorelick MH, Stevens MW, Schultz T, Scribano PV. Difficulty in obtaining peak expiratory flow measurements in children with acute asthma. Pediatr Emerg Care 2004; 20: 22 26.