Bronchial obstruction and exhaled nitric oxide response during exercise in cold air

Abstract

aaMuscular exercise in a cold environment requires both the warming and the humidification of large amounts of inspired air, resulting in a loss of heat and water from the respiratory tract. While these losses are known to induce airway obstruction in subjects with bronchial hyperresponsiveness, their effects are not well defined in normal nonatopic subjects. According to some authors, normal subjects do not develop measurable obstruction in response to airway cooling [1][2][3], whereas other authors claim that they respond by developing measurable obstruction when the stimulus is sufficiently great [4,5]. Under these conditions, the origin and mechanisms involved in the development of bronchial obstruction are still under debate [6][7][8].Endogenous NO is produced in the lung by a family of NO synthases [9][10][11]. This NO is thought to be an important modulator of vascular tone and airway function in normal airways. Therefore, NO may be involved in several physiological mechanisms during airway cooling. Thus, in normal pulmonary circulation, NO mediates the vasodilation response to physical and chemical factors [9]. Moreover, NO mediates the nonadrenergic, noncholinergic neural inhibitory responses which represent the only neural bronchodilator mechanism in human airways [12,13]. In addition, NO may contribute to acute inflammation and host defence in the lung [14].NO may be detected in the air exhaled by humans and the amount of NO exhaled over time (V 'NO) may be measured accurately and continuously [15][16][17][18]. Although the NO detected at the mouth is the difference between what is produced in the respiratory system and what is transformed or eliminated continuously by other endogenous pathways, V 'NO is generally assumed to reflect the NO produced by cells within the respiratory tract. Therefore, if endogenous NO-production takes a part in the mechanisms involved during airway cooling, a change in exhaled [NO] may be expected during inhalation of cold air. The aim of the present study was: 1) to confirm that extensive airway cooling can induce detectable airway obstruction in nonatopic subjects, 2) to determine whether this cooling induces changes in the V 'NO response, and 3) to determine whether a relationship may be established between both of these observations. Methods SubjectsEight well-trained male subjects, engaged in various endurance activities (cross-country skiing, triathlon or running) for >8 h·week -1 , were studied. These subjects were selected because they were able to produce a high ventilatory response during exercise and, would therefore, need to warm up a large amount of air when they exercised in Thus, eight well-trained males performed two incremental exercise tests until exhaustion, followed by 5 min of recovery in temperate (22°C) and cold (-10°C) environments, at random. At -10°C, they were dressed in warm clothes. Ventilation (V'E), oxygen consumption (V'O 2 ), carbon dioxide production, cardiac frequency (fC), and [NO] and V'NO were measured continuously. Before and after...

Exhaled Breath Temperature Increases after Exercise in Asthmatics and Controls

“…Prolonged hyperventilation of cold or dry air can cause the dehydration, suggesting an explanation for the high prevalence of the condition among cross-country skiers, cyclists and other endurance sports athletes. Furthermore, exercising in cold air may temporarily decrease the levels of exhaled nitric oxide (NO), reducing its bronchodilating effect [10] .…”

Measuring exhaled nitric oxide: not only a matter of how--but also why--should we do it?

“…This protective effect is further supported by the recent demonstration that the release of endogenous NO by kinins inhibits the bronchoconstriction induced by cold air inhalation in guinea pigs [45]. We must, however, keep in mind that in the study conducted by THERMINARIAS et al [44], as in other studies [46][47][48][49][50], there is an increase from baseline of the actual NO output during exercise, even with cold air breathing. The explanation is therefore likely to be far more subtle than the mere hypothesis of a relative deficiency of a bronchodilator agent (namely endogenous NO) being responsible for the occurrence of bronchial obstruction.…”

“…Even when NO seems to play a protective role as shown by THERMINARIAS et al [44], we still have dif-ficulty in putting forward an explanation for such a putative beneficial effect. Biological mechanisms underlying the ac-tion of NO in the human body are usually a complex matter.…”

“…In this issue of the Journal, THERMINARIAS et al [44] have shown that airway obstruction is associated with a relative de-crease in NO output during exercise in eight healthy subjects breathing cold (-10°C) as compared with ambient (22°C) air. Due to the bronchodilatory effect of NO, it is tempting to speculate that such a relative deficiency in NO production may favour the occurrence of airway obstruction in these subjects.…”

Measurement of Exhaled Nitric Oxide in Humans and Animals

“…133 affecting normal individuals. 112,141 This suggests that the exhaled NO in normal subjects is derived from Immersion and exercise in cool water 134 and exercise in cold air 135 reduce V NO suggesting that lower lung constitutive NOS (unaffected by steroids), whereas the elevated levels in asthma are derived from iNOS, NO may contribute to airway obstruction in cold and have a role in airway heat and water exchange.…”