Responses to physical activity among children and youths with exercise-induced asthma.

Asthma is a chronic condition due to bronchial tube inflammation, causing airflow restriction and lung hyperresponsiveness (National Institutes of Health [NIH], 1997), and is a major contributor to school absenteeism among children (Cypcar & Lemanske, 1995). A large percentage of those with chronic asthma also experience exercise-induced asthma (EIA), an acute asthmatic response to a bout of exercise, characterized by wheezing or breathlessness either during, but typically after exercise. As with chronic asthma, airway obstruction associated with EIA is reversible (Clark, 1992; Rupp, 1996). The purposes of this article are to describe the acute response and control of EIA during activity among children and youths and to explore potential benefits/non-benefits of long-term activity on EIA.

Pathophysiology and Prevalence of Exercise-Induced Asthma

Various mechanistic theories exist to explain symptoms of EIA. The most established theory, to this point, seems to be related to the loss of heat and water from the airways. Possible water loss or heat loss, due to strenuous breathing during exercise or activity, appears to result in bronchoconstriction (airway narrowing) or bronchospasm (Beck, 1999; Cypcar & Lemanske, 1995; Rupp, 1996; and Storms, 1999). During exercise, heat and water from respiratory tissue are lost to warm and humidified inspired air. Rate of loss occurs at a faster rate during exercise than during rest. Among individuals with EIA, the heat or water loss ultimately results in airway constriction.

A second theory to explain EIA is the thermal gradient or respiratory heat exchange theory (Cypcar & Lemanske, 1995; Storms, 1999). According to this theory, heat loss from airways causes bronchial tissue to dilate in order to re-warm the respiratory tract. Dilation of the vasculature then restricts airflow through bronchial passages. According to either of these theories, airway constriction can occur during exercise, but symptoms are typically most severe during the post-exercise period.

Exercise-induced asthma symptoms are noted when peak expiratory flow rate (PEFR) or forced expiratory volume (FE[V.sub.1]) decreases 15% from baseline following exercise (Morton & Fitch, 1990). Although other criteria exist for diagnosis of EIA, a 10-20% lung function decrease following exercise is categorized as mild EIA. A moderate diagnosis is made when the fall is 20-40%, and a severe diagnosis is made when reduction in lung function is 40% or greater (Rupp, 1996). Interestingly, exercise itself may be manipulated to prevent or reduce airway constriction during follow-up exercise (Cypcar & Lemanske, 1995; Ienna, 1994; Rupp, 1996). An athlete may invoke symptoms prior to a race to suppress symptoms during actual competition. Although useful for competitive athletes, encouraging children and youths to induce this refractory period is probably not an effective means of controlling EIA symptoms.

Asthma diagnoses are increasing (Kaliner, 1995). Increases may be explained by better diagnosis techniques or actual increased prevalence of asthma. Approximately 4-16% of individuals in the United States have been diagnosed with asthma, and at least 80% of individuals diagnosed with asthma present EIA. Incidences are highest among individuals under 18 years of age and are higher among blacks than whites (Kaliner, 1995; Mahler, 1993; Morton & Fitch, 1990; Rupp, 1996). Because such a large percentage of children and youths with asthma exhibit EIA, the physical education teacher or recreational professional must be able to recognize onset of EIA and be able to control symptoms within the classroom or program environment. Although incidences of asthma and EIA are lower among adults, EIA is not strictly a childhood response to exercise. Individuals who experience EIA during childhood may not exhibit symptoms of EIA during adolescence or early adulthood. However, the incidence of asthma increases among older adults and symptoms may return (Cypcar & Lemanske, 1995; Kaliner, 1995).

Asthma Education and Prevention Program

The National Heart, Lung, and Blood Institute (NHLBI) published an asthma education program for school practitioners (NIH, 1995). NHLBI indicated children and youth with asthma frequently avoid exercise and activity, although unnecessarily. Limited physical activity may lead to major health consequences (U.S. Department of Health and Human Services, 1996); therefore, perceived barriers (i.e., exercise) may indirectly increase morbidity among individuals with asthma. The purpose of the NHLBI report was to educate school personnel to recognize and manage children and youths with asthma to facilitate beneficial activity environments. School teachers and coaches may be the first individuals to recognize asthmatic symptoms.

Acute Activity Effects on Children and Youths with Asthma

Cardiovascular

Peak heart rates do not appear to be different between children and youths with and without asthma (Baba, Nagashima, Tauchi, Nishibata, & Kondo, 1997; Clark, 1992). Children with asthma are capable of demonstrating similar cardiovascular fitness levels as those without asthma. However, children and youths with asthma tend to have lower cardiovascular fitness scores than children without asthma (Baba, et al., 1997; Clark, 1992; Nixon, 1996). Practitioners must help individuals and their parents understand asthma and EIA, in a controlled manner, do not restrict performances or activity. It appears aerobic capacity is limited by lack of cardiovascular training, rather than respiratory constraints (Clark, 1992). Nonetheless, during or immediately after an asthmatic episode, activity may need to be modified in type, length, or frequency, but not necessarily eliminated (NIH, 1995).

Pulmonary

A possible deterrent to activity among children and youths with EIA is reduced air intake (i.e., lower lung volumes). Unlike individuals without asthma, children and youths with EIA exhibit substantial drops in PEFR and FE[V.sub.1] after cessation of exercise (Baba, et al., 1997; Heaman & Estes, 1997; Nixon, 1996). Peak expiratory flow rate is the maximum volume of air expelled following a maximal inhalation, and FE[V.sub.1] the maximum volume of air expelled in one second. In general, children experience reduced lung function 6-12 minutes into exercise, and severity is greatest 5-10 minutes following exercise (Rimmer, 1989). From a practical perspective, EIA prevents children from inspiring or expelling sufficient air to maintain intense activity. Service delivery professionals may want to purchase a peak flow meter to evaluate readiness for activity (some children may have their own meters). If lung volumes are below normal prior to activity, a child is more likely to develop EIA, so strenuous activity should be avoided. Peak flow meters are relatively inexpensive, and can be purchased at a local pharmacy.

Chronic Activity Effects on Children and Youths with Asthma

Cardiovascular

Children and youths with asthma are able to improve maximal aerobic capacities, and submaximal work/exercise efficiencies, at least among individuals with mild to moderate asthma (Clark, 1992; Haas, et al., 1987; Hallstrand, Bates, & Schoene, 2000; King, Noakes, & Weinberg, 1989; and Matsumoto, et al., 1999). By participating in activity regularly, children are able to exercise at higher intensities with less cardiovascular and pulmonary stresses. Hence, aerobic training may increase the EIA threshold or, stated differently, may enable children to exercise at higher intensities before symptoms occur (Haas, et al., 1987; Morton & Fitch, 1990). Therefore, aerobically trained children and youths may exhibit fewer episodes and use less medications (Bar-Or, 1993; Cypcar & Lemanske, 1995; King, Noakes, & Weinberg, 1989). If aerobic conditioning is structured, swimming may be the most suitable environment, as swimming may not induce EIA (Bar-Or, 1993; Nixon, 1996). Swimming typically occurs in a warm, humid environment, thereby possibly decreasing risks of water and heat losses from the respiratory tract during activity.

Evidence also exists that exercise training may not reduce number of EIA episodes (Nixon, 1996). Regarding episode severity, effects of chronic aerobic training are equivocal. Training may (Bar-Or, 1993; Cypcar & Lemanske, 1995; Nixon, 1996; Rimmer, 1989) or may not (Cypcar & Lemanske, 1995; King, Noakes, & Weinberg, 1989) alter severity of attacks or episodes. At this point, chronic aerobic training and activity appear to benefit symptoms of EIA, although effects do not appear to be consistent.

Pulmonary

Effects of improved health-related physical fitness on EIA among children and youths are equivocal. Evidence exists that aerobic training enhances post-exercise FE[V.sub.1] responses (Haas, et al., 1987) but may not alter exercise FE[V.sub.1] responses (King, Noakes, & Weinberg, 1989). Theoretically, aerobic training in particular may reduce heat and water loss during exercise, thereby impeding mechanisms that may lead to EIA symptoms (Bar-Or, 1990; Clark, 1992; Nixon, 1996).

For a child or youth with EIA, improving minute ventilation ([V.sub.e]) would certainly be a desired outcome of a training program. Minute ventilation is the volume of air traveling through the respiratory tract in one minute, and the product of the respiratory rate and inspired/expired lung volumes (Marieb, 1995). Theoretically, improved ventilation would indicate less airflow restrictions (or less airway constrictions). However, aerobic training regimens may not result in improved lung function during activity or improved submaximal [V.sub.e] or max [V.sub.e] (Haas, et al., 1987; King, et al., 1989).

Although effects of aerobic training among children and youths with asthma are not completely understood, increased activity seems to be a positive recommendation. Aerobic training is related to decreased rates of hospitalization and absenteeism from school (Bar-Or, 1993; Cypcar & Lemanske, 1995). Childhood asthma is already associated with obesity (Figueroa-Munoz, Chinn, & Rona, 2001), and lack of activity may result in additional secondary health concerns (e.g., diabetes). Through benefits of medications and asthma management, children and youths should be encouraged, rather than discouraged, to participate in regular physical activity (Bar-Or, 1993).

Common Medications and Intended Usage

Medications used in treating EIA can be classified into two categories--quick relief and long-term control (NIH, 1997). In the school or recreational setting, quick relief medications (e.g., [Beta.sub.2] agonists) are used either to prevent EIA during exercise or reverse symptoms after onset ([Beta.sub.2] denotes the receptor on which the medication has an effect). One may also see the term beta-andrenergic used for this type of medication, indicating norepinephrine or epinephrine binds to the cell, and in the case of the bronchioles, causes dilation (Marieb, 1995). Short acting medication is typically taken immediately (15-30 minutes) prior to exercise, and can prevent EIA or its symptoms for several hours. Albuterol is probably the most common generic form of this medication and may be used at cessation of exercise to inhibit airway constriction. Quick relief medications may also be called rescue inhalers because the medication effect is both immediate and substantial. In fact, Beta agonists are the most effective medications for preventing EIA symptoms (Rupp, 1996). If EIA symptoms persist following quick relief administration, chronic asthma is probably contributing to the symptoms, and the child/youth should be removed from activity and evaluated by a medical professional. Although schools may have stringent policies on medications, children and youths with asthma should be afforded easy access to short acting inhalers.

Because children and youths may not be able to bring medications to school or take medications on a day-long outdoor trip, long-term control medications, (e.g., long acting [Beta.sub.2] agonists) may prevent EIA for the majority of the school day (NIH, 1997). Long acting medications, similar to quick relief medications, are intended to prevent EIA symptoms before symptoms arise. Therefore, children and youths may not have to bring long acting medications to school to prevent EIA symptoms typically associated with activity. Salmeterol is one example of a generic medication. Whether using a short-term or long-term [Beta.sub.2] agonist, symptoms should not occur during exercise. Unlike quick relief medications, long-term control medications are not intended to reverse EIA symptoms.

A variety of daily medications, also termed long-term control treatments, are intended to treat chronic asthma (anti-inflammatory effects on the bronchial tubes), thereby reducing severity of future attacks. Flovent, Azmacort, and Pulmicort are examples of daily medications intended to treat chronic asthma. However, these medications are not intended to prevent EIA and are, therefore, not taken immediately prior to or concluding activity. Tables 1-3 review pharmacologic treatment of EIA and asthma.

Physical Activity Guidelines and Modifications

The most important activity modification for a child or youth with EIA is pre-medication. Short acting medications are typically taken 15-30 minutes prior to activity, but because directions for uses differ among medications, professionals should have a record of intended administration for each individual. Professionals should make every effort to ensure children and youths take medications prior to activity (Rimmer, 1989). School policies may prevent students from carrying/taking pre-exercise medications; therefore, school administration must have specific protocols to enable either the teacher, school nurse, or specific staff member to administer medications at the appropriate time (Surburg, 2000). Pre-medication should prevent EIA symptoms. If symptoms arise despite pre-medication, exercise is probably not the stimulus causing the symptoms, and medical attention should be sought.

Among non-medicated children and youths with asthma, service delivery personnel may be able to reduce risks of EIA symptoms by enabling students to participate in appropriate warm-ups and cool-downs (NIH, 1995). An adequate warm-up may reduce risk or severity of an EIA episode (Morton & Fitch, 1990; Nixon, 1996); and warm-ups should be specific to the child (e.g., some individuals with asthma may require longer warm-ups than others). The purpose of the warm-up is to prepare the body gradually for intensity of the exercise, thereby progressing gradually to peak [V.sub.e] and water/heat loss rates. Intensity progression should be made from least asthmogenic activities, such as walking and short-distance/area games, to the most asthmogenic activities, such as running or soccer (Morton & Fitch, 1990; Storms, 1999). A cool down period is equally important. Surburg (2000) indicated a child's heart rate should be within 20 beats of resting heart rate before stopping activity. For a child or youth with asthma, reducing exercise intensity is more beneficial than immediate activity cessation in terms of episode symptoms.

In the physical education classroom, activities including difficult motor skills or small activity spaces can be utilized as warm-ups. For example, lead-up games/activities requiring novel motor tasks (e.g., walking backwards, participating in pairs) do not allow drastic increases in intensity. Restricting the warm-up pace during team handball or ultimate Frisbee enables a teacher to discuss strategy while simultaneously enabling a gradual intensity increase. Regardless of the effort initiated by an individual, difficult motor tasks will not elicit the same breathing demands as mastered skills. Small activity spaces also limit exercise intensity. For instance, a soccer or basketball warm-up can be accomplished in a 2-on-2 or 3-on-3 setting, thereby reducing space coverage and energy demands. Long, continuous activity increases an individual's risk for experiencing EIA symptoms. Small spaces limit the speed and duration of activity, thereby reducing breathing demands of the activity. In general, interval, rather than continuous, activities are better activity options for children and youths with asthma (Rimmer, 1989; Surburg, 2000).

A teacher may want to evaluate a child's PEFR, via a peak flow meter, prior to participation. If the PEFR is below normal, the child/youth is more at risk for developing EIA symptoms during an activity. Specifically, the National Heart, Blood, and Lung Institute (NIH, 1995) recommends that intervention is necessary (e.g., intake of medication, modification of activity) when PEFR is less than 80% of the student's best.

Philosophically, professionals may have to determine if a child or youth with asthma should start the activity program apart from participants. For instance, children and youths with severe EIA may need to check PEFR prior to exercise, as well as walk 5 to 6 minutes without participating in more vigorous activities. Such activity deviations may be difficult for service delivery personnel to manage. If a child's or youth's EIA is managed effectively through medications, additional warm-up activities, apart from the group warm-ups, are probably not necessary.

Outside the classroom, children and youths with asthma should avoid cold, dry environments. Children and youths may also be advised to breathe through the nose to warm and humidify air (especially outside). Avoiding cold environments, and practicing nose breathing, may reduce the heat/water loss thought to contribute to EIA (Morton & Fitch, 1990). Swimming is an excellent activity option for individuals with asthma, possibly due to the warm, humid environment (less heat/water loss).

Excessive mucus production is also a concern with EIA. Excessive mucus production is a response to EIA and may further restrict breathing. Individuals with EIA should be encouraged to expel mucus regularly during activity (Surburg, 2000). In the classroom, teachers may need to establish policies to ensure children have opportunities to expel mucus throughout an activity session.

Service delivery personnel must be aware that breathlessness or wheezing may be most severe after a child has left the physical education classroom, playground, or athletic field. Physical education specialists, in particular, must communicate with classroom teachers about severity of symptoms a child or youth may be experiencing on arrival to the next class. Although chronic asthma symptoms may need to be treated immediately, EIA typically does not require hospitalization (Cypcar & Lemanske, 1995). Therefore, the purpose of communication is for the physical educator to understand the child's responses to EIA (e.g., cool down was/was not appropriate, activity intensity was/was not appropriate), not necessarily to determine if the child/youth feels healthy. If the child's or youth's responses to EIA are atypical, even after intake of medication, chronic asthma may be contributing to symptoms, and the child/youth should be evaluated immediately by a medical specialist.

Responding to Non-Participation

A major challenge for practitioners is responding to individuals who use EIA as an excuse to withdraw from physical activity. Children and youths with asthma have similar likenesses to physical education, and similar self-concepts as children without asthma (Routon & Sherrill, 1989). This point is made to emphasize that those who avoid physical education class may use asthma as an excuse not to exercise. It is difficult to mandate participation among children and youths when parents attempt to excuse participation. Teachers must reinforce potential benefits of activity relative to EIA to both children and parents. Exercise may reduce chronic asthma symptoms; exercise will not worsen a child or youth's chronic condition.

Despite typically lower health-related physical fitness levels, medical severity of asthma does not appear to be related to physical fitness (Clark, 1992; Cypcar & Lemanske, 1995). Insufficient education regarding exercise capacities among those with asthma, rather than limitations enforced by asthma itself, may lead to sedentary lifestyles. Stated earlier, NHBLI has indicated children and youth unnecessarily avoid physical activity. Lack of education among children and youths with EIA relative to activity capabilities may explain the poor relationship between medical severity and health-related physical fitness.

Conclusion

Questions remain regarding exact causes of EIA. Intensity and duration of activity appear to dictate EIA symptoms, with higher intensity and longer duration activities being most asthmogenic. Consistent activity appears to benefit children and youths with EIA; however, exact effects are equivocal. Aerobic training programs may reduce dependence on medications, and may reduce number of EIA episodes; however, regular activity does not appear to alter severity of EIA episodes. Although chronic activity/exercise may lead to benefits among individuals with EIA, effects of training programs do not appear to benefit all children and youths with asthma in the same ways. Nonetheless, proper management of medications and activity modifications can enable children and youths with asthma to enjoy and participate in physical activity in the same manner as their peers without asthma.

Table 1
Ouick Relief Medications for Exercise-Induced Asthma

Type               Generic Names  Indication           Brand Examples

[Beta.sub.2]       Albuterol      Relief and           Asmavent
 Agonists                          prevention of
                                   symptoms
                   Terbutaline                         Proventil
                                                       Ventolin

Anticholineregics  Ipratropium    Relief of symptoms   Apolpravent
                                                       Atrovent

Systemic           Prednisone     Relief of symptoms   Deltasone
 Corticosteroids                                       Novo-Prednisone
Table 2
Long-Term Control Medications Used to Prevent EIA

Type               Generic Names  Indication           Brand Examples

[Beta.sub.2]       Salmeterol     Prevention of        Serevent
 Agonists (long                    symptoms
 acting)                                               Ventolin
                   Albuterol
                    (sustained
                    release)

Cromolyn Sodium    Cromolyn       Prevention of        Crolom
 and Nedocromil                    symptoms
                   Nedocromil                          Intal
                                                       Tilade
Table 3
Long-Term Control Medications Used to Treat Chronic Asthma Rather
Than EIA

                                                       Brand
Type               Generic Names  Indication           Examples

Corticosteroids    Beclomethasone Anti-inflammatory    Beclovent
                    dipropionate
                   Budesonide                          Entocort
                   Triamcinole                         Pulmicort
                    acetonide
                                                       Azmacort

Methylxanthines    Theophylline   Bronchodilation      Slobid Gyrocaps

Leukotriene        Zafirlukast    Allergy response     Accolate
 Modifiers                         interference
                   Zileuton                            Zvflo

Selected References

Baba, R., Nagashima, M., Tauchi, N., Nishibata, K., & Kohdo, T. (1997). Cardiorespiratory response to exercise in patients with exercise-induced bronchial obstruction. Journal of Sports Medicine and Physical Fitness, 37, 182-186.

Bar-Or, O. (1990). Disease-specific benefits of training in the child with a chronic disease: What is the evidence? Pediatric Exercise Science, 2, 384-394.

Bar-Or, O. (1993). Effects of training on the child with a chronic disease: Beauty and the beast? Clinical Journal of Sports Medicine, 3, 2-5.

Beck, K. (1999). Control of airway function during and after exercise in asthmatics. Medicine and Science in Sports and Exercise, 31(1) (Suppl), S4-11.

Clark, C. (1992). The role of physical training in asthma. Chest, 101 (Suppl.), 293S-298S.

Cypcar, D., & Lemanske, R. (1995). Exercise-induced asthma. In B. Goldberg (Ed.), Sports and exercise for children with chronic health conditions (pp. 150-165). Champaign, IL: Human Kinetics.

Figueroa-Munoz, J., Chinn, S., & Rona, R. (2001). Association between obesity and asthma in 4-11 year old children in the UK. Thorax, 56, 133-137.

Haas, F., Pasierski, S., Levine, N., Bishop, M., Axen, K., Pineda, H., & Haas, A. (1987). Effect of aerobic training on forced expiratory airflow in exercising asthmatic humans. Journal of Applied Physiology, 63, 1230-1235.

Heaman, D., & Estes, J. (1997). The free-running asthma screening test: An approach to screening for exercise- induced asthma in rural Alabama. Journal of School Health, 67(3), 83-88.

Ienna, T. (1994). The asthmatic athlete: Metabolic and ventilatory responses during exercise with and without pre-exercise medication. Unpublished master's thesis: University of British Columbia, Vancouver, British Columbia, Canada.

Kaliner, M. (1995). What you need to know about asthma. In A. Cook & P. Dresser (Eds.), Respiratory diseases and disorders sourcebook: Vol. 6 (pp. 18-34). Detroit, MI: Omnigraphics.

King, J., Noakes, T., & Weinberg, E. (1989). Physiological effects of a physical training program in children with exercise-induced asthma. Pediatric Exercise Science, 1, 137-144.

Mahler, D. (1993). Exercise-induced asthma. Medicine and Science in Sports and Exercise, 25, 554-561.

Marieb, E. (1995). Human anatomy and physiology (3rd ed.). Redwood, CA: Benjamin/Cummings.

Morton, A., & Fitch, K. (1990). Exercise-induced bronchial obstruction. In J. Torg, R. Welsh, & R. Shephard (Eds.), Current therapy in sports medicine: Volume 2 (pp. 211-226). Philadelphia, PA: B. C. Decker.

National Institutes of Health: National Heart, Lung, and Blood Institute. (1995). Asthma and physical activity in the school. NIH Publication No. 95-3651: author.

National Institutes of Health: National Heart, Blood, and Lung Institute. (1997). Guidelines for the diagnosis and management of asthma: Expert panel report 2. NIH Publication No. 97-4051: author.

Nixon, P. (1996). Role of exercise in the evaluation and management of pulmonary diseases in children and youth. Medicine and Science in Sports and Exercise, 28, 414-420.

Rimmer, J. (1989). A vigorous physical education program for children with exercise-induced asthma. Journal of Physical Education, Recreation, & Dance, 60(6), 90-95.

Routon, J., & Sherrill, C. (1989). Attitude toward physical education and self-concepts of asthmatic and non-asthmatic children taught by physical education specialists. Perceptual and Motor Skills, 68(3, Pt 2), 1320-1322.

Rupp, N. (1996). Diagnosis and management of exercise-induced asthma. Physician and Sportsmedicine, 24(1), 77-87.

Surburg, P. (2000). Other health-impaired students. In J.P. Winnick (Ed.), Adapted physical education and sport (3rd ed., pp. 251-262). Champaign, IL: Human Kinetics.

Storms, W. (1999). Exercise-induced asthma: Diagnosis and treatment for the recreational or elite athlete. Medicine and Science in Sports and Exercise, 31(Suppl.), S33-S38.

U.S. Department of Health and Human Services. (1996). Physical activity and health: A report of the Surgeon General. Atlanta, GA: U.S. Department of Health and Human Services, Centers for Disease Control and Prevention, National Center for Chronic Disease Prevention and Health Promotion.

Jean Paul Barfield, Huntingdon College, has chronic asthma and participates in Huntingdon's sport/activity program for children with physical disabilities. Timothy J. Michael, Western Michigan University, promotes physical activity for the treatment of obesity and asthma.

Acute & Chronic Effects of Exercise on Children & Youth with EIA

Acute

* Reduces Lung function during or after exercise.

* Causes wheezing or breathless during or after exercise.

* Reduces ability to inhale or exhale air.

* Enables opportunity for healthy aerobic capacity.

Chronic

* May improve aerobic capacity.

* May improve EIA threshold (can exercise at high intensity prior to symptoms).

* May decrease dependence on short-term control medications.

* May or may not alter severity of symptoms.

Programming for Individuals with EIA

Activity Indications

* Pre-medicate.

* Check peak flow.

* Promote warm-ups & cool-downs (difficult motor tasks, small activity areas).

* Encourage interval activity.

* Encourage nose breathing (warms and humidifies inspired air).

* Allow mucus expelling.

* Encourage swimming.

* Encourage physical conditioning.

Activity Contraindications

* Avoid cold, dry environments.

* Avoid drastic intensity changes.

* Discourage non-participation.

* Avoid over-medication if symptoms persist.

Resources Relative to Asthma and EIA

* National Heart, Lung, & Blood Institute (www.nhlbi.nih.gov)

* American Lung Association (www.lungusa.org; 800-LUNG-USA)

* Asthma and Allergy Foundation of America (www.aafa.org; 800-7 ASTHMA)

* Centers for Disease Control (www.cdc.gov; 800-311-3435).