Factors predisposing to exercise-induced late asthmatic responses

Exercise-induced asthma in children

Exercise-induced asthma (EIA) is a relatively common problem in children, but may not be recognized because children either do not report their symptoms, or avoid activities that cause it. Clarifying the diagnosis of EIA, in particular separating EIA from other causes of exertional dyspnea, is essential. Treating EIA in children is challenging because of the nature of their physical activities, which are often not planned, and may be prolonged. Keeping children active is an important goal to ensure healthy physical and social development. Many children with EIA are well managed with an inhaled short-acting beta(2)-adrenoceptor agonist before exercise or if symptoms develop. The approach to more troublesome EIA depends on whether the child has persistent asthma and requires better prevention, or the EIA is an isolated clinical problem. The options for treatment also depend on the timing, frequency, and duration of activity that induces EIA. Options include the addition of a cromone, a leukotriene modifier, an inhaled corticosteroid, or switching to use a long-acting beta(2)-adrenoceptor agonist. The use of warm-up exercises has been shown to be helpful by using the refractory period but is not practical for most children with EIA. A final consideration for successful management of EIA in children is that the delivery of medication needs to be age-appropriate.

p38 mitogen-activated protein kinase and c-Jun-NH2-terminal kinase regulate interleukin-8 and RANTES production in hyperosmolarity stimulated human bronchial epithelial cells

OBJECTIVE

We have previously shown that p38 mitogen-activated protein kinase (MAPK) regulates, at least in part, hyperosmolarity induced interleukin (IL)-8 expression in human bronchial epithelial cells (BEC). In the previous study, hyperosmolarity also activated c-Jun-NH2-terminal kinase (JNK); however, the role of the JNK signalling pathway has not been determined. In the present study, we examined the role of the JNK signalling pathway in hyperosmolarity induced IL-8 and RANTES production by BEC using the novel inhibitor of the JNK signalling pathway CEP 11004 in order to clarify these issues.

METHODS

Bronchial epithelial cells that had been pre-incubated with SB 203580, CEP 11004 or a combination of these were exposed to a hyperosmolar medium and then the p38 MAPK and JNK phosphorylation activity in these cells and IL-8 and RANTES concentrations in the culture supernatants were determined.

RESULTS

The results showed that: (i) hyperosmolarity induced the threonine and tyrosine phosphorylation of p38 MAPK and JNK; (ii) SB 203580, as the specific inhibitor of p38 MAPK activity, and CEP 11004 attenuated hyperosmolarity induced p38 MAPK and JNK activity, respectively; (iii) SB 203580 and CEP 11004, but not PD 98059, partially attenuated IL-8 and RANTES production; and (iv) a combination of SB 203580 and CEP 11004 attenuated IL-8 and RANTES production in an additive fashion.

CONCLUSION

These results indicate that p38 MAPK and the JNK pathway regulate hyperosmolarity induced IL-8 and RANTES production by BEC.

Hyperosmolarity-induced interleukin-8 expression in human bronchial epithelial cells through p38 mitogen-activated protein kinase

The changes in airway osmolarity have been described to contribute to the production of exercise- induced bronchoconstriction (EIB) and the development of the late-phase response (LPR). The mechanism has been investigated; however, the responsiveness of bronchial epithelial cells (BEC) to hyperosmolarity and the intracellular signals leading to cell activation have not been determined. In this study, we examined the effect of hyperosmolar medium on interleukin-8 (IL-8) expression and the role of p38 mitogen-activated protein (MAP) kinase and c-Jun NH2 terminal kinase ( JNK) in human BEC in this response in order to clarify the intracellular signals regulating IL-8 expression in hyperosmolarity-stimulated BEC. The results showed that hyperosmolarity induced IL-8 expression in a concentration dependent manner, p38 MAP kinase phosphorylation and activation, and JNK activation whether NaCl or mannitol was used as the solute. SB 203580 as the specific p38 MAP kinase inhibitor inhibited hyperosmolarity-induced p38 MAP kinase activation and partially inhibited hyperosmolarity-induced IL-8 expression. These results indicate that p38 MAP kinase, at least in part, regulates hyperosmolarity-induced IL-8 expression in BEC. However, other signals such as JNK are possibly also involved. These results provide new evidence on the mechanism responsible for the development of the LPR induced by EIB, and a strategy for treatment with the specific p38 MAP kinase inhibitor.

Prevalence and characteristics of exercise-induced asthma in children

We have evaluated the prevalence and the characteristics of exercise-induced asthma (EIA) in a group of 71 patients with a prior history of mild, moderate or severe asthma (42 males and 29 females), aged 6-16 years-old. Measurements of the forced expiratory volume in 1 second (FEV1) were obtained before and at regular intervals up to 8 hours following exercise. As a control, the same patients were evaluated at similar time intervals on another day when they had not been submitted to an exercise challenge. Using pre-exercise FEV1 values as the reference, 32 patients (45.1%) had a positive exercise challenge, defined as a fall in FEV1 value equal to or greater than 15% from baseline following exercise. Among the patients with a positive exercise challenge, the majority (23/32, 71.8%) had an immediate response alone, with no significant changes in FEV1 within the 8-hour follow-up. However, a subgroup of patients (9/32, 28.1%) had both an immediate and a late-phase response to exercise. During the control day, no significant fall in FEV1 were observed. In keeping with previous investigations, no correlation was found between a history of EIA and a positive exercise challenge in the present study. Positive exercise challenges were found more frequently among patients with moderate and severe asthma than patients with mild asthma.

The occurrence of late asthmatic response to exercise after allergen challenge

BACKGROUND

The determinants of late asthmatic responses to exercise remain unknown. It has been reported that they may develop in some adult subjects with asthma following a late asthmatic response to allergen.

OBJECTIVE

We intended to corroborate this finding in children with asthma and to investigate which aspect of airway responses to allergen is associated with late asthmatic responses to exercise.

METHODS

We studied 17 children with allergic asthma, who showed late asthmatic responses to inhaled allergen (Dermatophagoides pteronyssinus). Each underwent an exercise challenge test two days before (pre-allergen) and two days after (postallergen) an allergen inhalation challenge. FEV1 was measured at regular intervals up to ten hours after each challenge. Methacholine PC20 was measured before the allergen challenge and before the postallergen exercise challenge.

RESULTS

After the pre-allergen exercise test, all the subjects showed isolated early asthmatic responses. After the postallergen exercise test, seven showed dual responses (early and late asthmatic responses) (group I) and the remaining ten showed isolated early asthmatic responses (group II). Bronchial responses to pre-allergen exercise or inhaled allergen and the severity of early asthmatic responses to postallergen exercise were similar in groups I and II. Neither before allergen inhalation nor before the postallergen exercise was methacholine PC20 different between the two groups. Methacholine dose shift caused by allergen challenge, however, was significantly greater in group I than in group II (-2.00+/-0.39 versus -1.36+/-0.53 doubling doses; P < .05). There was significant correlation between the dose shift and the magnitude of late response to the postallergen exercise in the whole group (r = 0.51, P < .05).

CONCLUSION

Late asthmatic responses to exercise may develop in some children with asthma following a late asthmatic response to allergen. This phenomenon was related neither to the baseline nor to postallergen methacholine PC20 but to the extent of increased sensitivity to methacholine caused by allergen challenge.

Peripheral blood manifestations of T(H)2 lymphocyte activation in stable atopic asthma and during exercise-induced bronchospasm

BACKGROUND

Recently, TH2 lymphocyte activation has been shown to play a key role in initiating and propagating the inflammatory response in asthmatic airways. This is manifest through increased numbers of "activated" CD25-(IL-2R)-bearing T-helper cells and can be seen through the IL-5 driven recruitment of eosinophils and IL-4-mediated B-cell expression of CD23 (low affinity IgE receptor) and ultimately IgE production.

OBJECTIVE

To gain a better understanding of the role of immune cells in asthma by describing the peripheral blood immune cell phenotypes in mild atopic asthma.

METHODS

We enrolled 13 patients with mild atopic asthma and a group of seven nonatopic, nonasthmatic controls. Objective measures of lung function were obtained. The peripheral blood was analyzed by flow cytometry for specific cellular markers at rest and during the development of exercise induced bronchospasm.

RESULTS

At rest the number of CD23-bearing B cells (169/mL versus 117/mL; P = .05) and the number of CD25-bearing T cells (355/mL versus 237/mL; P = .03) were increased in the asthma group. There was a linear relationship between these two lymphocyte subsets and the maximum voluntary ventilation at rest (r = 0.56, P = .01 and r = 0.57, P = .01). With the development of exercise-induced bronchospasm there was a significantly greater increase in CD23-positive B cells (96.7/mL versus 59.7/mL; P = .05) and CD25-positive T cells (111.8/mL versus 45.1; P = .01) in the asthma group.

CONCLUSIONS

These data indicate that TH2 lymphocyte activation is manifested by increased numbers of CD23-bearing B cells and CD25-bearing T cells in the peripheral blood of patients with stable mild atopic asthma. Further, these immune cell subsets correlate with markers of resting lung function and increase in the peripheral blood early after the development of exercise-induced bronchospasm.

Late asthmatic response in exercise-induced asthma

BACKGROUND

There is a controversy over the occurrence of a late asthmatic response during exercise-induced asthma. While some workers have documented such a response as a genuine phenomenon, others have attributed this to drug withdrawal.

OBJECTIVES

We carried out the present study to investigate whether a late asthmatic response occurs during exercise-induced asthma as a genuine event and, if so, what are the factors which determine its occurrence.

METHODS

Sixteen, clinically stable asthmatic patients with laboratory-proven exercise-induced asthma underwent a standardized exercise challenge on a bicycle ergometer. The airway response to exercise was studied by spirometry to measure FEV1. Spirometry was carried out before the exercise, at 4, 8, 15, 30, and 60 minutes, and then hourly for the next 7 hours. Spirometry was also done repeatedly as above on a non-exercise control day, four to seven days earlier.

RESULTS

Eight (50%) subjects developed a second fall of greater than 10% in FEV1, three to eight hours after recovery from the early response. The late fall in FEV1 after exercise was significantly greater than the spontaneous decay of lung function at the corresponding clocktime on the non-exercise control day. The dual responders did not differ from those with isolated early responses with respect to age, duration and severity of asthma, treatment requirements, peripheral blood eosinophilia, and atopic status. Baseline FEV1 and maximum fall in FEV1 during the early response, and the rate of its development and recovery from it were also similar. Among the dual responders, the late response was not related to the baseline FEV1 or to the intensity of the early response.

CONCLUSIONS

A late asthmatic response is a genuine phenomenon in exercise-induced asthma. Its occurrence cannot however be predicted by any clinical or physiologic factors.

GC/MS analysis of urinary excretion of 9alpha,11beta-PGF2 in acute and exercise-induced asthma in children

BACKGROUND

9Alpha,11beta-prostaglandin (PG) F2 is an initial metabolite of PGD2 which has a potent bronchoconstrictive activity.

OBJECTIVES

We measured the urinary levels of 9alpha,11beta-PGF2 in asthmatic children to investigate its role in not only acute asthmatic attack in a time course study but also in exercise-induced asthma (EIA).

METHODS

In the acute asthma study, 30 asthmatic children were examined. Urine samples were collected on the first, third, and sixth days. Urinary levels of 9alpha,11beta-PGF2 were measured with gas chromatography mass spectrometry using the electron impact method. In the exercise challenge study, 14 children with EIA and 14 children without EIA were studied. Urine samples were collected before exercise challenge, and at 1 h, and 5 h after exercise challenge. Urinary levels of 9alpha,11beta-PGF2 were measured.

RESULTS

Elevated urinary levels of 9alpha,11beta-PGF2, which were observed on the first day when treatment was started in the hospital, were gradually decreased on the third day (P < 0.05), and on the sixth day (P < 0.01). A significant correlation between urinary levels of 9alpha,11beta-PGF2 and symptom scores (P < 0.005) was observed on the first day. In EIA, there was a significant increase in urinary levels of 9alpha,11beta-PGF2 at 1 h (P < 0.01) and at 5 h (P < 0.01) after exercise challenge, but not in the children without EIA.

CONCLUSION

9Alpha,11beta-PGF2 may be involved in the pathogenesis of acute and exercise-induced asthma in children.

Exercise-induced asthma and the use of hypertonic saline aerosol as a bronchial challenge

Exercise induced asthma is a common complaint and the prevalence appears to be increasing worldwide. Once confined to the research domain of university teaching hospitals, the study of EIA has extended into the school playground, defence force establishments and sports institutions. Standardized protocols have been developed to study EIA in the laboratory and in the field. A surrogate challenge using eucapnic or isocapnic hyperventilation with dry air is becoming popular because it has advantages over exercise, at least for adults. The stimulus that leads the airways to narrow is caused by the inhalation of dry air during hyperventilation and exercise, during which water is evaporated from the airways in order to condition the inspired air. The mechanism whereby the airways narrow is thought to be due to the dehydrating effects of water loss, particularly in relation to its potential to cause the airways to become hyperosmolar. Mast cell mediators such as histamine and the leucotrienes are probably involved in EIA because specific antagonists reduce severity. As a result of the osmotic theory of EIA, studies were carried out to determine whether subjects with EIA were sensitive to the effects of increasing airway osmolarity by inhalation of hyperosmolar aerosols of sodium chloride. A challenge protocol using an aerosol of 4.5% sodium chloride, generated from an ultrasonic nebulizer, has been used to identify persons with asthma and to assess response to drug therapy. There are many similarities between responses to exercise, hyperventilation and hypertonic saline in the physiological and biochemical responses and the responses to drugs. Challenge with hypertonic saline is easier and cheaper to use because expensive equipment and a source of dry air is not required as with exercise or hyperventilation. The ability to obtain a dose-response curve rather than a single response and the ability to collect inflammatory cells at the same time make challenge with hypertonic saline an attractive technique to study patients suspected of having asthma.

Maximal airway narrowing on the dose-response curve to methacholine is increased after exercise-induced bronchoconstriction

The changes in airway responsiveness between before and after exercise in asthma are not well defined. We investigated the effect of exercise on PC20 (bronchial sensitivity) and maximal airway narrowing (MAN) on the dose-response curve to methacholine in 56 mildly asthmatic children. High-dose methacholine inhalation tests were performed before and 7 hr after exercise challenge. Methacholine PC20 was not changed by exercise, irrespective of exercise-induced bronchoconstriction (EIB). However, the subjects with (+)EIB displayed increased MAN after exercise, whereas those with (+/-)EIB or (-)EIB did not. The results showed that EIB may be followed by increased MAN but not by the change of bronchial sensitivity.

Airway responsiveness to allergen is increased 24 hours after exercise challenge

Although exercise is one of the most ubiquitous triggers of acute bouts of asthma, the changes in airway responsiveness before and after exercise are not well defined. Specifically, the effect of the changes in airway responsiveness induced by exercise has not been studied on subsequent allergen exposure. To test whether the reactivity to allergen is altered by preceding exercise and to define possible factors determining it, we subjected 24 children with atopic asthma to the relevant allergen challenge on two occasions: one as a control without a preceding procedure and the other 24 hours after exercise challenge. Mean postallergen maximal percent falls in forced expiratory volume in 1 second from baseline (delta FEV1) of the whole group were higher after the exercise challenge compared with those of control in both early (< 1 hour) and late (3 to 10 hours) phases. The changes of postallergen maximal delta FEV1 between the control and post-exercise allergen challenges were not related to the early bronchial response to the preceding exercise challenge. Late asthmatic responses to exercise developed in six children, and the changes in both early and late phases were significantly higher in these children, compared with those without late asthmatic responses. Furthermore, the changes were well correlated with the magnitude of the late-phase response to preceding exercise in the group as a whole. It is concluded that an increased airway responsiveness to allergen occurs 24 hours after exercise in some patients with asthma. As the changes are related to a late bronchial response to exercise, late asthmatic response to exercise, when it occurs, may be associated with increased asthmatic symptoms for as long as 24 hours after exercise.

Alpha 4-integrins mediate antigen-induced late bronchial responses and prolonged airway hyperresponsiveness in sheep

Eosinophils and T lymphocytes are thought to be involved in allergic airway inflammation. Both cells express the alpha 4 beta 1-integrin, very late antigen-4 (VLA-4, CD49d/CD29); alpha 4-integrins can promote cellular adhesion and activation. Therefore, we examined the in vivo effects of a blocking anti-alpha 4 monoclonal antibody, HP 1/2, on antigen-induced early and late bronchial responses, airway hyperresponsiveness, inflammatory cell influx, and peripheral leukocyte counts in allergic sheep. Sheep blood lymphocytes, monocytes, and eosinophils expressed alpha 4 and bound HP 1/2. In control sheep, Ascaris antigen challenge produced early and late increases in specific lung resistance of 380 +/- 42% and 175 +/- 16% over baseline immediately and 7 h after challenge, respectively, as well as airway hyperresponsiveness continuing for 14 d after antigen challenge. Treatment with HP 1/2 (1 mg/kg, i.v.) 30 min before antigen challenge did not affect the early increase in specific lung resistance but inhibited the late-phase increase at 5-8 h by 75% (P < 0.05) and inhibited the post-antigen-induced airway hyperresponsiveness at 1, 2, 7, and 14 d (P < 0.05, for each time). Intravenous HP 1/2 given 2 h after antigen challenge likewise blocked late-phase airway changes and postchallenge airway hyperresponsiveness. Airway administration of HP 1/2 (16-mg dose) was also effective in blocking these antigen-induced changes. Response to HP 1/2 was specific since an isotypic monoclonal antibody, 1E6, was ineffective by intravenous and aerosol administration. Inhibition of leukocyte recruitment did not totally account for the activity of anti-alpha 4 antibody since HP 1/2 neither diminished the eosinopenia or lymphopenia that followed antigen challenge nor consistently altered the composition of leukocytes recovered by bronchoalveolar lavage. Because airway administration of HP 1/2 was also active, HP 1/2 may have inhibited cell activation. Reduction of platelet-activating factor-induced eosinophil peroxidase release from HP 1/2-treated eosinophils supports such a mechanism. These findings indicate a role for alpha 4-integrins in processes that lead to airway late phase responses and persisting airway hyperresponsiveness after antigen challenge.

Water loss without heat flux in exercise-induced bronchospasm

We identified inspired gas conditions that result in no net respiratory heat loss, an isenthalpic condition, but induce a mucosal loss of water. Inspired gas at 37 degrees C with 47 mm Hg water vapor pressure, 56 degrees C with 38 mm Hg; and 78 degrees C with 27 mm Hg has the same heat content as fully saturated air at body temperature. In four normal subjects hyperventilating at a minute ventilation of 30 times their FEV1 for 6 min, expired temperatures at the mouth averaged 39 degrees, 43 degrees, and 43 degrees C for the three conditions. Retrotracheal esophageal temperatures did not fall in any subject, thereby demonstrating the absence of significant airway cooling. Nine subjects with exercise-induced bronchospasm were tested under the same conditions. Baseline functions showed an FEV1 of 85 +/- 10% of predicted (mean +/- SD), FVC, 98 +/- 13% of predicted, and FEV1/FVC, 79 +/- 4% of predicted. The asthmatic subjects demonstrated postchallenge mean falls in FEV1 of 3.4%, 6.2%, and 10.1% for the three conditions, with bronchospasm increasing as the temperature of the inspired air increased (p = 0.001). The amount of respiratory water lost from the respiratory mucosa significantly correlated with the resultant bronchospastic response as measured by the fall in FEV1 (p = 0.017), but the net respiratory heat lost did not significantly correlate (p = 0.113). This study demonstrates that bronchospasm can be induced without significant respiratory heat loss or airway cooling and suggests that it is proportional to the amount of water lost from mucosal surfaces.

Reproducibility of late phase pulmonary response to exercise and its relationship to bronchial hyperreactivity in children with chronic asthma

To determine the reproducibility of the delayed response to exercise and its effect on bronchial hyperreactivity, we had 26 asthmatic children perform treadmill exercise challenge on two occasions 1 week apart. Both challenges were preceded by 2 control days and 1 histamine challenge day, and were followed by another histamine challenge day. Peak expiratory flow rate (PEFR) was measured hourly for 12 hours on each control day and for 12 hours after each exercise or histamine challenge. During the first week, five patients showed a late reaction (PEFR change > 15%) after exercise, which was present in only two of them the following week. These two patients, however, also showed a spontaneous fall > 15% of PEFR from baseline during the other control study days. A similar pattern was seen in two other patients who had a late response during the second exercise challenge but not during the first. No significant change occurred in histamine PC-20 FEV1 between before and after the exercise challenges. An apparent late asthmatic response after exercise challenge may represent a within-day fluctuation in pulmonary mechanics that develops spontaneously in children with asthma.

Eosinophils in exercise-induced asthma

The variations in serum levels of eosinophil cationic protein (ECP) have been measured after exercise challenge of 13 patients with asthma with exercise-induced asthma (EIA) and nine patients with asthma without EIA. The patients were treated before exercise in a randomized and blinded fashion with inhalation of one dose of either disodium chromoglycate, terbutaline, or budesonide and in an open study with 4 weeks of inhaled budesonide. In the group with EIA, there was, in some patients, an initial increase in serum levels of ECP after exercise, but 60 minutes after exercise, the levels were significantly reduced (p less than 0.001). Disodium chromoglycate and 4 weeks of budesonide treatment inhibited this reduction. Histamine challenge of the group with EIA produced a similar fall in serum ECP levels (p less than 0.001). The group without EIA had initially lower levels of ECP than the group with EIA (p less than 0.05 to p less than 0.01), and ECP stayed unaltered after exercise. The preexercise serum ECP levels correlated significantly to the maximal fall in peak expiratory flow in the untreated group (r = 0.91; p less than 0.001) and in the group receiving one dose of budesonide (r = 0.62; p less than 0.05). The blood eosinophil counts were unchanged after challenge and not related to lung function. The results suggest that the ECP content in serum reflects the degree of allergic inflammation in the lungs and thereby the degree of bronchial hyperreactivity.

Late asthmatic responses after exercise challenge are reproducible

In this study the reproducibility of a late asthmatic reaction (LAR) after exercise challenge (EC) has been documented. Eighty-three hospitalized patients with asthma were challenged with exercise. The patients were examined according to a standardized protocol that comprised 8 minutes of bicycling at 90% of predicted heart rate. An LAR after EC was considered to have occurred when there was a fall in peak expiratory flow rate greater than or equal to 20% on three or more time points on the exercise day compared to corresponding clock time on a control day. According to these criteria, 11 patients (13.3%) experienced an LAR. Those patients were rechallenged 21 to 150 days after the first EC, without changing the therapy regimen of the patients, to study its reproducibility. Eight patients (73%) demonstrated a reproducible LAR after EC based on the criteria for a positive LAR. Although the LAR after EC was reproducible, the time points at which the LAR took place after the second EC differed from LARs after the first EC. Our results indicate that the LAR after EC occurs in a considerable number of patients with bronchial asthma and is quite reproducible.

Exercise response in 404 young men with asthma: no evidence for a late asthmatic reaction

As the existence of a late reaction in exercise induced asthma is controversial, peak expiratory flow (PEF) was measured for up to 13 hours after a running test in 404 consecutive young male army conscripts undergoing assessment of their asthma. In 294 subjects (73%) the immediate post-exercise fall in PEF was 10% or more; the mean (SD) fall in PEF in this group was 27% (15%). Nine patients with exercise induced asthma had a fall in PEF of 20% or more 4-13 hours after the exercise test. In these possible "late responders," however, the change in PEF 4-13 hours after exercise was similar to the change in PEF on control days before and after the exercise day, and the lowest PEF during this period was similar to the lowest measurements on the control days. These nine subjects showed pre-exercise bronchodilatation. Their pre-exercise PEF, from which the percentage fall in PEF was calculated, was 24% (9%) higher than the mean PEF level on control days. This study supports the view that what appears to be a "late asthmatic reaction" after exercise is an artefact. Spontaneous within day fluctuation in pulmonary function, pre-exercise bronchodilatation, and the fact that airflow obstruction persists after the early postexercise response may give a false impression of an exercise induced late asthmatic response in patients with labile airways.

Cold air challenge for measuring airway reactivity in children: lack of a late asthmatic reaction

Cold air challenge (CACh) for measuring airway reactivity uses respiratory heat or water loss as a bronchoconstrictor stimulus; this stimulus is also important for the development of exercise-induced asthma, for which late asthmatic reactions (LARs) have been described. At 1200 hr on day 1, 22 children with asthma started to record their peak expiratory flow rate (PEFR) in 3 hr intervals until 0900 hr on day 2. At 1000 hr, they underwent a standardized 4 min CACh. Children then inhaled salbutamol and continued to record PEFR until 0900 hr on day 3. As a bronchodilator effect, PEFR measurements were significantly higher 2, 5, and 8 hr after CACh, but subsequently did not differ significantly from pre-CACh values. At 5 hr after CACh, individual values ranged from 95 to 137% of the corresponding pre-CACh measurements, at 8 hr from 94 to 150%, and at 11 hr from 80 to 121%. This random sample of children with asthma demonstrated no LAR after CACh.

Real and pseudo late asthmatic reactions after submaximal exercise challenge in patients with bronchial asthma. A new definition for late asthmatic responses after exercise challenge

The late asthmatic reaction after exercise challenge remains a controversial issue. In this study, 21 patients recorded peak expiratory flow rate (PEFR) on two control days without performing exercise. There was no difference between both control days when PEFR at 1 h was compared with baseline PEFR and when PEFR at 4 to 13 hours was compared with baseline PEFR. After analyzing variation coefficients of baseline PEFR on a control day and exercise day, PEFR was not allowed to differ more than 15.3 percent in the same patient when comparing exercise day and control day for the late fall in PEFR in the study. In 17 of 81 patients, a late asthmatic reaction after exercise challenge was present when PEFR fall was greater than or equal to 20 percent compared with baseline PEFR value. In eight of the 17 patients, a real late asthmatic reaction to exercise challenge was present with a PEFR fall greater than or equal to 20 percent on at least three successive time points and who had a PEFR fall greater than or equal to 20 percent compared with corresponding clocktime on a control day. The late asthmatic reaction to exercise challenge is characterized not as a nonspecific epiphenomenon, but as a fall in PEFR of greater than or equal to 20 percent compared with baseline PEFR value and with corresponding clocktime on a control day on at least three successive time points. Graphic illustration of airway responses following exercises may facilitate the detection of a late asthmatic response.

Pharmacology of allergen-induced early and late airway responses and antigen-induced airway hyperresponsiveness in allergic sheep

The pharmacology of antigen-induced early and late phase airway responses and the associated antigen-induced airway hyperresponsiveness was studied in allergic sheep. Data from studies with anti-allergic agents and specific receptor antagonists, especially leukotriene antagonists and antagonists of platelet activating factor (PAF), have led to the hypothesis that allergen-induced late responses in allergic sheep are linked to a heightened metabolism of arachidonic acid via the 5-lipoxygenase pathway. This increases leukotriene production during the acute allergic reaction, which results in a more prolonged acute bronchoconstriction and subsequently a more severe airway inflammation. These recruited inflammatory cells can then release mediators and other cell products which contribute to the late response and airway hyperresponsiveness.

Rhinovirus upper respiratory infection increases airway hyperreactivity and late asthmatic reactions

Although viral upper respiratory infections (URIs) provoke wheezing in many asthma patients, the effect of these illnesses on the airway response to inhaled antigen is not established. The following study evaluated the effect of an experimental rhinovirus (RV) illness on airway reactivity and response to antigen in 10 adult ragweed allergic rhinitis patients. Preinfection studies included measurements of airway reactivity to histamine and ragweed antigen. Furthermore, the patients were also evaluated for late asthmatic reactions (LARs) to antigen (a 15% decrease in forced expiratory volume of the first second approximately 6 h after antigen challenge). 1 mo after baseline studies, the patients were intranasally inoculated with live RV16. All 10 patients were infected as evidenced by rhinovirus recovery in nasal washings and respiratory symptoms. Baseline FEV1 values were stable throughout the study. During the acute RV illness, there was a significant increase in airway reactivity to both histamine and ragweed antigen (P = 0.019 and 0.014, respectively). Before RV inoculation, only 1 of the 10 subjects had an LAR after antigen challenge. However, during the acute RV illness, 8 of 10 patients had an LAR (P less than 0.0085 compared with baseline); the development of LARs was independent of changes in airway reactivity and the intensity of the immediate response to antigen. Therefore, we found that not only does a RV respiratory tract illness enhance airway reactivity, but it also predisposes the allergic patient to develop LARs, which may be an important factor in virus-induced bronchial hyperresponsiveness.

Re-examination of the late asthmatic response to exercise

To determine the nature of the delayed response to exercise, we had 20 atopic asthmatics perform cycle ergometry on 2 occasions while breathing either frigid or hot-humid air in a random fashion. The latter served as a sham control. Forced expiratory volume in one second (FEV1) was measured serially for 10 h after each trial. Subjects developing a second wave of obstruction after recovery from the initial asthma attack were rechallenged on a third day with methacholine and followed in an identical fashion. Cold-air exercise produced an immediate 28% fall in FEV1 for the group as a whole, after which 2 distinct patterns of recovery developed. In 13 subjects, the initial obstruction resolved over several hours. Thereafter, lung function remained constant. In the remaining 7 subjects, the early attack was followed by an initial improvement and then progressive deterioration. This pattern occurred at the same times and to the same magnitude both in the hot-humid experiment in which the initial obstruction was absent, and when the obstruction was induced with methacholine. Based on these observations, it appears that the late asthmatic reaction that follows physical exertion in some subjects is a nonspecific epiphenomenon that is neither dependent upon the existence of an early response nor is unique to exercise.

Prevalence and characteristics of late asthmatic responses to exercise

The prevalence and characteristics of late asthmatic responses to exercise were studied in an adult asthmatic population. Twenty-four subjects (eight male and 16 female), aged 17 to 39 years (mean, 23.7 years), performed a 6-minute exercise on a bicycle ergometer at 75% of their maximum oxygen intake. FEV1 was measured at regular time intervals up to 8 hours after exercise. Seven subjects demonstrated a late asthmatic reaction defined as a fall in FEV1 greater than 10% between 2 to 8 hours. Bronchial reactivity to histamine was unchanged 24 hours after the exercise, compared to baseline. On a control day, a fall in FEV1 similar to the one observed after exercise was induced by methacholine inhalation. Measurements of FEV1 were done at the same time intervals as on exercise day. Neutrophil chemotactic activity was measured in the serum of 15 subjects, on exercise day for early responders, and on the 3 test days for subjects with a dual response. There was no difference between subjects with an isolated early or late response for age, sex, or atopic status. Baseline expiratory flows and nonspecific bronchial reactivity to histamine were similar in both groups. These results demonstrate the occurrence of a late asthmatic response in 30.4% of the population studied. There was no significant change of nonspecific bronchial responsiveness after the late asthmatic response to exercise. No significant increase in neutrophil chemotactic activity could be observed.

Immediate and delayed bronchoconstriction after exercise in patients with asthma

Although an immediate asthmatic response after exercise is known to occur in some patients with asthma, the existence of a delayed asthmatic response after exercise is controversial. Accordingly, we studied 53 patients who had an immediate mean (+/- SD) decrease in forced expiratory volume at one second (FEV1) of 36 +/- 13 percent, which was maximal 13 +/- 12 minutes after the completion of treadmill exercise. Eight of these patients also had a delayed asthmatic response (a 32 +/- 5 percent decrease in FEV1 occurring 5.0 +/- 1.8 hours after exercise). During a control day, on which the FEV1 was measured serially but no exercise was performed, the same delayed asthmatic response was observed in all but one patient. This finding suggests that the delayed asthmatic response observed in these patients after exercise was not specifically related to the performance of exercise. We conclude that in patients who have bronchoconstriction immediately after exercise, a second asthmatic response occurring later after the exercise is uncommon.