Effects of dry and humid climates on exercise-induced asthma in children and preadolescents

Bar‐Or, Oded; Neuman, I; Dotan, Raffy

doi:10.1016/0091-6749(77)90119-1

Cited by 117 publications

(42 citation statements)

References 20 publications

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“…The results from the present study confirm that inhalation of warm-humid air attenuates the bronchoconstrictor response to challenge with exercise [5,10,11,13]. Because subjects showed refractoriness both after exercise challenges that produced bronchoconstriction (thermoneutral trials) and after reduced or nonbronchoconstricting bouts (warm-humid trials), airway constriction was not an essential trigger of refractoriness in these subjects.…”

Section: Discussionsupporting

confidence: 72%

“…The purpose of this study was to see whether the effect of indomethacin, a prostaglandin synthetase inhibitor could help answer this question. The inhalation of warm-humid air during the initial exercise has been shown to reduce, or even abolish, exercise-induced asthma (EIA) [10,11], without abolishing refractoriness [12,13]. This phenomenon provides a condition where the effects of prior exercise on refractoriness can be studied independent of the effects of prior EIA.…”

mentioning

confidence: 99%

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The effects of indomethacin on refractoriness following exercise both with and without a bronchoconstrictor response

Wilson¹,

Bar‐Or²,

O'Byrne³

1994

Eur Respir J

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T Th he e e ef ff fe ec ct ts s o of f i in nd do om me et th ha ac ci in n o on n r re ef fr ra ac ct to or ri in ne es ss s f fo ol ll lo ow wi in ng g e ex xe er rc ci is se e b bo ot th h w wi it th h a an nd d w wi it th ho ou ut t a a b br ro on nc ch ho oc co on ns st tr ri ic ct to or r r re es sp po on ns se e ABSTRACT: Repeated exercise tests demonstrate refractoriness to the development of exercise-induced asthma (EIA). It is unclear whether it is the initial exercise per se or the resulting bronchoconstriction that causes the attenuated response to the second exercise challenge. This study was designed to determine whether the reported blocking of the refractory period by indomethacin requires a significant bronchoconstriction following the primary exercise challenge.Thirteen asthmatic teenagers (aged 12-16 yrs) were tested on four visits. Each visit included two 7 min treadmill exercise challenges at 80% maximum heart rate, separated by a 30 min rest. Conditions for the second exercise challenge (Ch2) were always thermoneutral (20-22°C and 25-35% relative humidity (RH); whilst challenge one (Ch1) was completed twice in thermoneutral and twice in warm-humid breathing conditions (33-35°C and 90-95% RH). A pretreatment for 3 days in a double-blind design with either placebo or indomethacin was completed. Forced expiratory volume in one second (FEV 1 ) was measured before and repeatedly following each challenge. The % fall in FEV 1 following Ch1 of the placebo thermoneutral trial was taken as reference. "Percent protection" at each visit was expressed as the decrease in EIA following Ch2, compared to reference.Warm-humid breathing reduced the EIA post Ch1 by 75%, whilst providing similar protection to thermoneutral conditions. Indomethacin had no significant effect on EIA after Ch1, but reduced "percent protection" for both warm-humid (from 67 to 16%) and thermoneutral (from 70 to 26%) conditions.The data indicate that inhibitory prostaglandins play a major role in EIA refractoriness and suggest that the release of these prostaglandins is initiated by some exercise factor, independent of the development of bronchoconstriction.

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Section: Discussionsupporting

confidence: 72%

mentioning

confidence: 99%

The effects of indomethacin on refractoriness following exercise both with and without a bronchoconstrictor response

Wilson¹,

Bar‐Or²,

O'Byrne³

1994

Eur Respir J

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“…AT HV-REC GRADIENT (°C) the resulting obstruction (1)(2)(3)(4)(5)(6)(7) (Fig. 2), and through this, the magnitude of airflow limitation (Fig.…”

Section: Resultsmentioning

confidence: 99%

“…In the past, it has been documented that the initial reaction sequence in the production ofairway obstruction in asthmatics after exercise or hyperventilation was linked to the process of respiratory heat exchange and involved a fall in airway temperature (1)(2)(3)(4)(5)(6)(7). Recent data have expanded this concept by suggesting that cooling alone is insufficient to produce obstruction, and that a second event, such as the rate of rewarming that occurs in the immediate recovery period, may also be pathogenically important in this condition (8)(9)(10).…”

Section: Introductionmentioning

confidence: 99%

Airway cooling and rewarming. The second reaction sequence in exercise-induced asthma.

Gilbert

McFadden²

1992

J. Clin. Invest.

102

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To determine if a relationship exists among the magnitude and rate of airway rewarming, and the severity of bronchial obstruction in thermally induced asthma, we had seven subjects perform three-to four-point stimulus response curves with isocapnic hyperventilation of frigid air with and without pretreatment with inhaled norepinephrine. The latter was employed to alter the heat supplied to the airway walls by producing vasoconstriction. 1-s forced expiratory volume (FEV l) was measured before and 5 min after the cessation of each bout of hyperpnea and before and after norepinephrine. On a separate day, the subjects repeated the above challenges while the temperatures of the airstream in the intrathoracic airways were measured. Prenorepinephrine, FEV1 progressively decreased in a stimulus response fashion as ventilation rose, while norepinephrine shifted this curve to the right. As the level of ventilation increased, the size ofthe temperature difference between the cooling of hyperpnea and the rewarming of recovery followed suit, and their magnitude was linearly related to the severity of bronchial narrowing. Reducing the mucosal blood supply of the airways with norepinephrine limited rewarming and attenuated the obstructive response. These data demonstrate that the airway narrowing that develops following hyperpnea and the magnitude of the thermal differences are related, and that alterations in blood supply directly affect bronchial heat flux and influence obstruction. (J. Clin. Invest. 1992.90:699-704.)

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“…Whatever the mechanism, the severity of EIA is known to be influenced by the level of work undertaken, together with the temperature and water content of the inspired air [16][17][18]. It was, therefore, logical to assess whether the use of cold, dry, inspired air would increase the sensitivity of the exercise challenge.…”

Section: Discussionmentioning

confidence: 99%

Exercise-induced airway narrowing in army recruits with a history of childhood asthma

Sinclair¹,

Sims²,

Hoad³

et al. 1995

Eur Respir J

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E Ex xe er rc ci is se e--i in nd du uc ce ed d a ai ir rw wa ay y n na ar rr ro ow wi in ng g i in n a ar rm my y r re ec cr ru ui it ts s w wi it th h a a h hi is st to or ry y o of f c ch hi il ld dh ho oo od d a as st th hm ma a ABSTRACT: The aim of this study was to determine whether the addition of cold, dry, inspired air to maximum heart rate (MHR) exercise increased the number of subjects demonstrating abnormal airway narrowing, when applied to symptom-free army recruits with a history of asthma in childhood. One hundred recruits with a history of asthma in childhood underwent two exercise challenges to maximum heart rate, breathing either room air or cold dry air in randomized order. The percentage fall index (%FI) was calculated for each challenge, a positive result being ≥15%.A total of 29 subjects had a positive % fall index, 12 subjects were positive to both challenges, 7 to the room air alone and 10 to the cold air challenge alone. In these subjects (n=29), the mean (SD) % fall index to the cold air challenge was 22.7 (11.0)% compared with 16.3 (9.5)% for the room air challenge.We conclude that when employed as a screening test for abnormal airway narrowing, the addition of cold, dry, inspired air during exercise does not increase the number of subjects with a positive response, but the magnitude of the response is increased.

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Effects of dry and humid climates on exercise-induced asthma in children and preadolescents

Cited by 117 publications

References 20 publications

The effects of indomethacin on refractoriness following exercise both with and without a bronchoconstrictor response

The effects of indomethacin on refractoriness following exercise both with and without a bronchoconstrictor response

Airway cooling and rewarming. The second reaction sequence in exercise-induced asthma.

Exercise-induced airway narrowing in army recruits with a history of childhood asthma

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