JWBT335-c130013
JWBT335-CompPhys-3G
Printer: Yet to Come
February 23, 2015 8:37 8in×10.75in
Air Quality and Temperature Effects on Exercise-Induced Bronchoconstriction Kenneth W. Rundell,*1 Sandra D. Anderson,2 Malcolm Sue-Chu,3 Valerie Bougault,4 and Louis-Philippe Boulet5 ABSTRACT Exercise-induced bronchoconstriction (EIB) is exaggerated constriction of the airways usually soon after cessation of exercise. This is most often a response to airway dehydration in the presence of airway inflammation in a person with a responsive bronchial smooth muscle. Severity is related to water content of inspired air and level of ventilation achieved and sustained. Repetitive hyperpnea of dry air during training is associated with airway inflammatory changes and remodeling. A response during exercise that is related to pollution or allergen is considered EIB. Ozone and particulate matter are the most widespread pollutants of concern for the exercising population; chronic exposure can lead to new-onset asthma and EIB. Freshly generated emissions particulate matter less than 100 nm is most harmful. Evidence for acute and long-term effects from exercise while inhaling high levels of ozone and/or particulate matter exists. Much evidence supports a relationship between development of airway disorders and exercise in the chlorinated pool. Swimmers typically do not respond in the pool; however, a large percentage responds to a dry air exercise challenge. Studies support oxidative stress mediated pathology for pollutants and a more severe acute response occurs in the asthmatic. Winter sport athletes and swimmers have a higher prevalence of EIB, asthma and airway remodeling than other athletes and the general population. Because of fossil fuel powered ice resurfacers in ice rinks, ice rink athletes have shown high rates of EIB and asthma. For the athlete training in the urban environment, training during C 2015 American Physiological Society. low traffic hours and in low traffic areas is suggested. Compr Physiol 5:579-610, 2015.
Introduction Exercise-induced bronchoconstriction (EIB) is a response to airway dehydration in the presence of inflammatory cells and mediators in a person with responsive bronchial smooth muscle (BSM). It is important to note that approximately 80% to 90% of asthmatics bronchoconstrict from exercise and up to 20% of individuals without apparent asthma exhibit EIB. Asthma and EIB without apparent asthma are similar in that they both require the presence of inflammatory cells and receptors responsive to bronchoconstricting mediators. Typically, maximal bronchoconstriction occurs 5 to 20 min after the cessation of short-term exercise (5-10 min) at high ventilation intensities (76), but occurs to some degree during exercise of longer duration, although a mechanical protection from exercising ventilation has been reported (40). There can also be a refractory period following exercise in 40% to 50% of individuals with EIB where bronchoconstriction will be significantly reduced or eliminated. Likewise, a late phase or biphasic response can occur 5 to 11 h after the initial bronchoconstriction to exercise. This late response is associated with increases in both eosinophils and neutrophils in bronchoalveolar fluid. The rate of occurrence for late phase response may be as high as 40% of early phase responders. One study found that 9 of 32 children who demonstrated an immediate response to exercise demonstrated a late-phase fall in FEV1
Volume 5, April 2015
within an 8 h period postexercise (325). However, other studies have questioned the existence of the late-phase response to exercise per se, and have alternatively associated it with airway inflammation and the allergen response (71, 95). Inspired air is conditioned to body temperature and 99% relative humidity as it passes through the airways. The water for this process is obtained from the thin layer of airway surface liquid (ASL) and can result in local changes in osmolarity. This can result in the generation and release of mediators from inflammatory cells such as mast cells and eosinophils. If the specific receptors are present on the airway smooth * Correspondence
to [email protected] of The Basic Sciences, The Commonwealth Medical College, Scranton, PA, USA 2 Clinical Professor Department of Respiratory and Sleep Medicine, Royal Prince Alfred Hospital, Camperdown, New South Wales, Australia 3 Department of Thoracic Medicine, St Olavs Hospital, Trondheim University Hospital, Department of Circulation and Medical Imaging, Norwegian University of Science and Technology, Trondheim, Norway 4 Universit´ e Lille Nord de France, Lille, France 5 Institut universitaire de cardiologie et de pneumologie de Qu´ ebec, Qu´ ebec, Canada Published online, April 2015 (comprehensivephysiology.com) DOI: 10.1002/cphy.c130013 C American Physiological Society. Copyright 1 Department
579
JWBT335-c130013
JWBT335-CompPhys-3G
Printer: Yet to Come
February 23, 2015 8:37 8in×10.75in
EIB: Air Pollution and Temperature
EIA and inspired water concentration 50
40 % fall FEV1
muscle, bronchoconstiction can occur. The severity of this response is related to the water content of the inspired air and the level of ventilation achieved and sustained. Repetitive hyperpnea of dry air and polluted air during training in athletes is associated with inflammatory changes and remodeling in the airways and an increased prevalence of EIB to dry air exercise. This article will address the mechanism and pathophysiology of EIB with particular attention given to cold/dry air hyperpnea during exercise. The high prevalence of airway dysfunction and EIB among athletes who train and compete in polluted environments will be discussed and relationships between inhaled air pollutants from auto and truck emissions as well as chloramines from swimming pools and the effects on the airways will be detailed.
Comprehensive Physiology
30
20
10
0 0
Mechanism and Pathophysiology of EIB Conditioning the inspired air The stimulus to EIB is the loss of heat and water from the airways that occurs during exercise in response to conditioning large volumes of air in a short time (14). Under resting conditions, breathing is usually via the nose around 5 to 10 L/min and most conditioning occurs in the upper airways and before the air reaches the pharynx (303). During exercise, the ventilation can increase 10 to 20 times the resting level and breathing switches from the nose to the mouth. When air is inspired it needs to be heated and humidified to body conditions (37◦ C and 44 mg H2 O/L) before it reaches the alveoli. Heat and water are lost and, in the process, the airways are cooled and on expiration, some heat and water are returned (251). As the air inspired during exercise is usually below body temperature and not fully humidified and the air expired is usually around 32◦ C and 31 mg H2 O/L, there is normally a net loss of heat and water during exercise (12,252, 260, 303).
Conditions for provoking EIB To provoke EIB in susceptible people particularly those with atopic asthma, the exercise intensity, while breathing relatively dry air of temperate conditions (18◦ C and
JWBT335-CompPhys-3G
Printer: Yet to Come
February 23, 2015 8:37 8in×10.75in
Air Quality and Temperature Effects on Exercise-Induced Bronchoconstriction Kenneth W. Rundell,*1 Sandra D. Anderson,2 Malcolm Sue-Chu,3 Valerie Bougault,4 and Louis-Philippe Boulet5 ABSTRACT Exercise-induced bronchoconstriction (EIB) is exaggerated constriction of the airways usually soon after cessation of exercise. This is most often a response to airway dehydration in the presence of airway inflammation in a person with a responsive bronchial smooth muscle. Severity is related to water content of inspired air and level of ventilation achieved and sustained. Repetitive hyperpnea of dry air during training is associated with airway inflammatory changes and remodeling. A response during exercise that is related to pollution or allergen is considered EIB. Ozone and particulate matter are the most widespread pollutants of concern for the exercising population; chronic exposure can lead to new-onset asthma and EIB. Freshly generated emissions particulate matter less than 100 nm is most harmful. Evidence for acute and long-term effects from exercise while inhaling high levels of ozone and/or particulate matter exists. Much evidence supports a relationship between development of airway disorders and exercise in the chlorinated pool. Swimmers typically do not respond in the pool; however, a large percentage responds to a dry air exercise challenge. Studies support oxidative stress mediated pathology for pollutants and a more severe acute response occurs in the asthmatic. Winter sport athletes and swimmers have a higher prevalence of EIB, asthma and airway remodeling than other athletes and the general population. Because of fossil fuel powered ice resurfacers in ice rinks, ice rink athletes have shown high rates of EIB and asthma. For the athlete training in the urban environment, training during C 2015 American Physiological Society. low traffic hours and in low traffic areas is suggested. Compr Physiol 5:579-610, 2015.
Introduction Exercise-induced bronchoconstriction (EIB) is a response to airway dehydration in the presence of inflammatory cells and mediators in a person with responsive bronchial smooth muscle (BSM). It is important to note that approximately 80% to 90% of asthmatics bronchoconstrict from exercise and up to 20% of individuals without apparent asthma exhibit EIB. Asthma and EIB without apparent asthma are similar in that they both require the presence of inflammatory cells and receptors responsive to bronchoconstricting mediators. Typically, maximal bronchoconstriction occurs 5 to 20 min after the cessation of short-term exercise (5-10 min) at high ventilation intensities (76), but occurs to some degree during exercise of longer duration, although a mechanical protection from exercising ventilation has been reported (40). There can also be a refractory period following exercise in 40% to 50% of individuals with EIB where bronchoconstriction will be significantly reduced or eliminated. Likewise, a late phase or biphasic response can occur 5 to 11 h after the initial bronchoconstriction to exercise. This late response is associated with increases in both eosinophils and neutrophils in bronchoalveolar fluid. The rate of occurrence for late phase response may be as high as 40% of early phase responders. One study found that 9 of 32 children who demonstrated an immediate response to exercise demonstrated a late-phase fall in FEV1
Volume 5, April 2015
within an 8 h period postexercise (325). However, other studies have questioned the existence of the late-phase response to exercise per se, and have alternatively associated it with airway inflammation and the allergen response (71, 95). Inspired air is conditioned to body temperature and 99% relative humidity as it passes through the airways. The water for this process is obtained from the thin layer of airway surface liquid (ASL) and can result in local changes in osmolarity. This can result in the generation and release of mediators from inflammatory cells such as mast cells and eosinophils. If the specific receptors are present on the airway smooth * Correspondence
to [email protected] of The Basic Sciences, The Commonwealth Medical College, Scranton, PA, USA 2 Clinical Professor Department of Respiratory and Sleep Medicine, Royal Prince Alfred Hospital, Camperdown, New South Wales, Australia 3 Department of Thoracic Medicine, St Olavs Hospital, Trondheim University Hospital, Department of Circulation and Medical Imaging, Norwegian University of Science and Technology, Trondheim, Norway 4 Universit´ e Lille Nord de France, Lille, France 5 Institut universitaire de cardiologie et de pneumologie de Qu´ ebec, Qu´ ebec, Canada Published online, April 2015 (comprehensivephysiology.com) DOI: 10.1002/cphy.c130013 C American Physiological Society. Copyright 1 Department
579
JWBT335-c130013
JWBT335-CompPhys-3G
Printer: Yet to Come
February 23, 2015 8:37 8in×10.75in
EIB: Air Pollution and Temperature
EIA and inspired water concentration 50
40 % fall FEV1
muscle, bronchoconstiction can occur. The severity of this response is related to the water content of the inspired air and the level of ventilation achieved and sustained. Repetitive hyperpnea of dry air and polluted air during training in athletes is associated with inflammatory changes and remodeling in the airways and an increased prevalence of EIB to dry air exercise. This article will address the mechanism and pathophysiology of EIB with particular attention given to cold/dry air hyperpnea during exercise. The high prevalence of airway dysfunction and EIB among athletes who train and compete in polluted environments will be discussed and relationships between inhaled air pollutants from auto and truck emissions as well as chloramines from swimming pools and the effects on the airways will be detailed.
Comprehensive Physiology
30
20
10
0 0
Mechanism and Pathophysiology of EIB Conditioning the inspired air The stimulus to EIB is the loss of heat and water from the airways that occurs during exercise in response to conditioning large volumes of air in a short time (14). Under resting conditions, breathing is usually via the nose around 5 to 10 L/min and most conditioning occurs in the upper airways and before the air reaches the pharynx (303). During exercise, the ventilation can increase 10 to 20 times the resting level and breathing switches from the nose to the mouth. When air is inspired it needs to be heated and humidified to body conditions (37◦ C and 44 mg H2 O/L) before it reaches the alveoli. Heat and water are lost and, in the process, the airways are cooled and on expiration, some heat and water are returned (251). As the air inspired during exercise is usually below body temperature and not fully humidified and the air expired is usually around 32◦ C and 31 mg H2 O/L, there is normally a net loss of heat and water during exercise (12,252, 260, 303).
Conditions for provoking EIB To provoke EIB in susceptible people particularly those with atopic asthma, the exercise intensity, while breathing relatively dry air of temperate conditions (18◦ C and
