Breathing Dry Air Research Articles

Exercise-Induced Bronchospasm in Soccer Athletes Living in a Tropical Humid Region

Background: Exercise-induced bronchospasm (EIB) is frequent in asthmatic athletes and, although less prevalent, also occurs in non-asthmatic ones. Breathing warm-humid air reduces this phenomenon.Objective: To evaluate EIB prevalence in semi-professional soccer athletes from a tropical humid region.Methods: We included athletes from a soccer team from the city of Recife-Brazil. A history of asthma or respiratory symptoms after exercise, demographic data and baseline FEV1 measurements were obtained. Thereafter, each athlete performed a standardized free field running to achieve 85% to 95% of the maximum calculated heart rate for the last 6 minutes of a total running time of 8 to 10 minutes. FEV1 was measured again at 5, 10, 15 and 30 minutes after exercise and EIB was defined as a reduction ≥ 10% from basal values in two consecutive time points. Results: Fifty-four male athletes aged between 13 and 21 years were evaluated. All denied exercise associated respiratory symptoms. Mean temperature and air humidity were 30.2°C ± 2.7°C and 82.1% ± 2.9%, respectively. EIB was found in two (7%) athletes (with a fall in FEV1 from baseline of 23.3% and 22.6%), none with history of asthma symptoms. Two other athletes had a history of asthma symptoms in childhood but no decrease in FEV1. Conclusion: The studied population of semi-professional soccer athletes with no exercise associated respiratory complaints showed a low BIE prevalence (7%). It may be necessary to perform the challenge with the athlete breathing dry air in those that also play in more dry and cold climates.

Exercise test using dry air in random adolescents: Temporal profile and predictors of bronchoconstriction.

Guidelines recommend exercise tests using dry air to diagnose exercise-induced bronchoconstriction (EIB). Lung function changes subsequent to these tests have not been investigated in a general adolescent population, and it remains unknown whether signs of airway inflammation, measured using exhaled nitric oxide (FeNO), can predict a positive response. The aim of this study was to investigate the temporal aspect of decline in forced expiratory volume in 1 s (FEV1 ) after an exercise test using dry air, and to investigate predictors of EIB. From a cross-sectional study on adolescents aged 13-15 years (n = 3838), a random subsample of 146 adolescents (99 with and 47 without self-reported exercise-induced dyspnoea) underwent standardized treadmill exercise tests for EIB while breathing dry air. Of the adolescents, 34% had a positive EIB test (decline of ≥10% in FEV1 from baseline) within 30 min. Of the subjects with EIB, 53% showed the greatest decline in FEV1 at 5 to 10 min (mean decline 18.5%), and the remaining 47% of the subjects showed the greatest decline at 15 to 30 min (mean decline 18.9%) after exercise. Increased FeNO (>20 ppb), female gender and self-reported exercise-induced dyspnoea were independently associated with a positive EIB test. When assessing general adolescents for EIB with exercise test using dry air, there is a temporal variation in the greatest FEV1 decline after exercise. Therefore, lung function should be measured for at least 30 min after the exercise. Increased FeNO, female gender and self-reported exercise-induced dyspnoea can be predictors of a positive EIB test.

Prevalence of exercise-induced bronchoconstriction and exercise-induced laryngeal obstruction in a general adolescent population

BackgroundExercise-induced respiratory symptoms are common among adolescents. Exercise is a known stimulus for transient narrowing of the airways, such as exercise-induced bronchoconstriction (EIB) and exercise-induced laryngeal obstruction (EILO). Our aim...

Comparing nebulized water versus saline after laryngeal desiccation challenge in Sjögren's Syndrome

This study examined the effects of a laryngeal desiccation challenge and two nebulized hydration treatments on phonation threshold pressure (PTP), vocal effort, and throat dryness in patients with chronic airway dryness. Double-blind, within-subjects crossover design. Eleven individuals with Primary Sjögren's Syndrome received a 15-minute laryngeal desiccation challenge (breathing dry air-<1% relative humidity-transorally), followed by nebulized isotonic saline or nebulized water treatments (3 mL) on 2 consecutive weeks. PTP, as well as self-perceived vocal effort, mouth, and throat dryness were assessed before and after the desiccation challenge, and at 5, 35, and 65 minutes after the nebulized treatment. The laryngeal desiccation challenge produced statistically significant increases in PTP, vocal effort, and mouth and throat dryness (P < 0.05). Nebulized saline produced greater-but not statistically significant-treatment effects than water. PTP was more correlated with throat dryness than vocal effort. Patients with chronic airway dryness experienced phonatory changes following dry air exposure. Nebulized isotonic saline may offset this effect. Future research should explore dose-response relationships among dry air exposure, nebulized treatments, voice change, and self-perceived throat dryness.

Comparative And Synergistic Effects Of Caffeine And Albuterol On The Severity Of Exercise-induced Bronchoconstriction.

PURPOSE: Previous research has demonstrated a beneficial effect of caffeine on preventing exercise-induced bronchoconstriction (EIB). Therefore, the main aim of this study was extend previous published findings that have demonstrated a beneficial effect of caffeine on EIB by evaluating the comparative and synergistic effects of caffeine and albuterol (b2-agonist) on the severity of EIB. METHODS: Ten asthmatic subjects with EIB participated in a randomized, double-blind double-dummy crossover study. One hour before an exercise challenge, each subject was given 0, 3, 6, or 9mg/kg of caffeine or placebo mixed in a flavored sugar drink. Fifteen minutes before the exercise bout, an inhaler containing either albuterol (180μg) or placebo was administered to each subject. Pulmonary function tests were conducted pre- and post-exercise (1, 5, 10, 15 and 30 min). The exercise challenge comprised of each subject running on a motorized treadmill to volitional exhaustion while breathing dry air from a gas tank. RESULTS: Caffeine significantly reduced (P < 0.05) the mean maximum % fall in post-exercise FEV1 at 6 and 9mg/kg (-9.0±9.2% and -6.8±6.5%) as compared to the double-dummy (placebo; -14.3±11.1%) and baseline (-18.4+7.2%). There was no significant difference (P>0.05) in the post-exercise % fall in FEV1 between albuterol (without caffeine) (-4.0±5.2%) and the 9mg/kg dose of caffeine (-6.8±6.5%). Interestingly, there was no significant difference (P>0.05) in the post-exercise % fall in FEV1 between albuterol (without caffeine) (-4.0+5.2%) and albuterol with 3, 6 or 9mg/kg of caffeine (-4.4±3.8, -6.8±5.6, -4.4±6.0% respectively). Similar changes noted for the post-exercise % fall in FEV1 were also observed for FVC, FEF25-75% and PEF. In addition, it was determined that a dose-response relationship existed between the %fall in post-exercise FEV1 and caffeine dose administered (0, 3, 6 and 9 mg/kg) for all dependent variables. DISCUSSION: These data indicate that moderate (6 mg/kg) to high doses (9 mg/kg) of caffeine can reduce the severity of EIB in a dose-response manner. These data also indicate that no significant difference exists between high doses of caffeine and albuterol which suggests that caffeine may represent an alternative to albuterol reducing the severity of EIB.

Influence of Body Fat on Exercise-Induced Bronchoconstriction

The prevalence of obesity and asthma (including exercise-induced bronchoconstriction, EIB) are both increasing in the United States. While previous research suggests a link between obesity and EIB, the effect of body fat on airway hyper-reactivity following exercise is not known. PURPOSE: To determine the effect of body fat on airway function in subjects with EIB. METHODS: Thirteen subjects (4 men, 9 women) with EIB (determined by ≥10% decrease in FEV1 following an exercise bout and a eucapnic voluntary hyperventilation test: EVH) were divided into three groups (high fat HF, n=5; moderate fat MF, n=4; low fat LF, n=4) based on total body fat (g) relative to height (HF 161.4 ± 19.5; MF 117.5 ± 8.5; LF 63.5 ± 9.9 g/cm; p <0.05) determined via Dual Energy X-ray Absorptiometry (DXA; Lunar). Pulmonary function tests (PFT) and exhaled nitric oxide (ENO; Sievers) were determined in triplicate pre and post (min 5, 15, 30) exercise. Subjects completed a constant load eight minute exercise test on a cycle ergometer at a workload based on a target ventilation of ∼50–60% predicted maximal voluntary ventilation while breathing dry air. RESULTS: There were no differences (P > 0.05) between groups in PFT or ENO at rest, or in metabolic or ventilatory variables during exercise. However, the decrease in FEV1 from baseline to 5 minutes post exercise was less (p <0.05) in MF (−15.5 ± 1.4%) compared to both LF (−28.5 ± 6.6%) and HF (−31.2 ± 1.4%). Also, at 5 minutes post exercise, the decrease in ENO was significantly greater in HF (−18.6 ± 2.7%) vs. MF (−8.8 ± 2.5%). There was no difference (P > 0.05) at min 15 or 30 post exercise in any variable. CONCLUSION: These data suggest that, for our population, both high and low body fat lead to greater airway narrowing following exercise in subjects with EIB compared to subjects with moderate body fat amounts. The mechanism responsible may be a greater bronchoprotective role of airway nitric oxide in moderately fat individuals.

Acute Relief of Exercise-Induced Bronchoconstriction by Inhaled Formoterol in Children With Persistent Asthma

To compare the acute bronchodilatory effect of the long-acting beta2-agonist formoterol against the short-acting beta2-agonist (SABA) terbutaline during exercise-induced bronchoconstriction (EIB) in children with asthma. A randomized, double-blind, placebo-controlled, crossover study of the immediate effect of formoterol, 9 microg, vs terbutaline, 0.5 mg, and placebo administered as dry powder at different study days. Exercise challenge test was used as a model of acute bronchoconstriction. Twenty-four 7- to 15-year-old children with persistent asthma. The children performed standardized treadmill exercise tests, breathing dry air, with a submaximal workload. Study medication was administered 5 min after exercise if FEV1 dropped > or = 15% within 5 min after exercise. FEV1 and forced expiratory flows were measured repeatedly until 60 min after dose. Formoterol and terbutaline offered a significant acute bronchodilatory effect from 3 min after dose compared with placebo (p < 0.001). There was no difference between formoterol and terbutaline in FEV1 5 min after dose (p = 0.15), with a mean increase from each predrug baseline of 62% of the maximum increase for both. Median times to recovery within 5% of baseline FEV1 were 5.0 min and 7.4 min for formoterol and terbutaline, respectively (p = 0.33). Single-dose formoterol, 9 microg, via dry powder inhaler provided an acute bronchodilatory effect similar to terbutaline during EIB in schoolchildren with persistent asthma. Formoterol is at least as effective as SABA and may be considered an alternative in the treatment of acute bronchoconstriction in school children.

Exercise-induced bronchoconstriction in children: Montelukast attenuates the immediate-phase and late-phase responses

Background: Montelukast, a leukotriene receptor antagonist, attenuates exercise-induced bronchoconstriction. We and others have shown that there is a late-phase response 3 to 8 hours after exercise in a subset of asthmatic patients. Objective: We sought to evaluate the protective effect of montelukast on immediate-phase and late-phase responses after exercise challenges. Methods: Twenty-two atopic asthmatic children aged 7 to 16 years with reproducible exercise-induced bronchoconstriction (minimum of 15% decrease of FEV1 from baseline) were enrolled in this placebo-controlled crossover study. Exercise challenges were performed while breathing cold dry air, and FEV1 measurements were taken up to 480 minutes after exercise. Patients underwent exercise challenges on a screening day and 1 week after placebo treatment. Subsequently, after a week with no treatment, pulmonary function was assessed after breathing dry cold air (control day). Finally, an exercise challenge was carried out after a week of treatment with montelukast. Results: Reproducible late-phase reactions occurred in 5 of 22 patients, which correlated with the extent of the immediate response (P < .05). After 1 week of treatment with montelukast, a significant decrease of immediate responses was observed. Montelukast treatment compared with placebo was associated with a lower mean maximum decrease of FEV1 (mean ± SEM: 17.3% ± 2.4% and 35.1% ± 2.6%, respectively), decrease of the area above the curve (267.8% ± 42.7%/min and 868.0% ± 103.8%/min, respectively), and shorter time for recovery (6.9 ± 1.1 minutes and 30.9 ± 4.0 minutes, respectively; P < .05). Treatment with montelukast also abolished late-phase responses. Conclusion: Once daily treatment with oral montelukast attenuated the immediate-phase response and abolished the late-phase response induced by means of exercise challenge in asthmatic children. (J Allergy Clin Immunol 2003;111:301-7.)

EFFECTS OF NITRIC OXIDE SYNTHASE INHIBITION IN LUNG FUNCTION DURING EXERCISE IN ASTHMATICS

Upon cessation of exercise, pulmonary resistance (RL) and forced expired volume in one second (FEV1) significantly deteriorate in individuals with exercise-induced asthma. However, lung function during exercise is relatively well preserved. Nitric oxide (NO) is a known bronchodilator that might have a protective effect during exercise. METHODS We evaluated changes in RL during 20 min moderate intensity exercise in 17 subjects with FEV1 91% ± 16% predicted and a positive exercise challenge test (reduction in FEV1>15% after exercise breathing dry air). RL was assessed before, during, and up to 15 min after the 20-min exercise on two days; subjects were treated with a nebulized NO synthase inhibitor LNMMA (Ng-monomethyl-L-arginine, 50mg in 2mL saline) or saline in random order, double blinded. RESULTS LNMMA increased RL (81% ± 78% on LNMMA day vs 6.6% ± 28% on saline day, P < 0.01). A decline in RL early in exercise was not prevented by LNMMA, and post exercise increase in RL was similar on the two days (table). There was a slow rise in RL during exercise that was the same on the two days (0.061 ± 0.063 for saline, 0.078 ± 0.078 for LNMMA, units cmH2O/L/sec per min of exercise).TableCONCLUSIONS Our results suggest that NO might regulate baseline airway tone, but it is not further involved in the control of airway function during or after exercise. A dilator influence is present early in exercise, which might be related to mechanical effect of increased tidal volume or respiratory rate. Supported by NIH grants HL52230 and NIH RR-00585

Exercise-Induced Bronchoconstriction in Adults with Asthma

The bronchial response to cycling and running was compared in six adult asthmatic persons. The effects of different air conditions during cycling regarding the induction of bronchoconstriction was studied.The exercise consisted of 6 minutes' work at an intensity of 80–85% of maximal heart rate. Heart rate, oxygen consumption and ventilation were measured to check that the exercise level was the same in all tests. Peak expiratory flow (PEF) was used to test for bronchoconstriction.Bicycling and treadmill running were performed under indoor conditions and bicycling while breathing cold, dry air (−18°C) and room-tempered humid air (60% RH), respectively.No difference in bronchoconstriction was found between cycling and running under indoor conditions. However, bicycling exercise with inhalation of cold dry air provoked more bronchoconstriction than when inhalating humid air (PEF reductions of 19.4 ± 6% and 6.1 ± 2%, respectively). No differences were found between the exercise modes in heart rate, oxygen consumption, ventilation per minute, respiratory rate, carbon dioxide elimination or subjective ratings of perceived exertion and breathlessness.It is concluded that it is not the type of exercise, but the ventilation demand and humidity of the inspired air that are the main determinants of the occurrence and degree of bronchoconstriction.

Sample size estimation in studies monitoring exercise-induced bronchoconstriction in asthmatic children.

BACKGROUND: The repeatability of the response to standardised treadmill exercise testing using dry air and monitoring of heart rate in asthmatic children suffering from exercise-induced bronchoconstriction (EIB) has not been...

Duration of Protection by Inhaled Salmeterol in Exercise-induced Asthma

Beta-adrenoceptor agonists such as albuterol are very effective in preventing exercise-induced asthma (EIA) when they are given as an aerosol immediately before exercise. However, their duration of protection against EIA is usually less than 2 h. This may be due partly to their rapid clearance from the airways. Salmeterol is a highly lipophylic compound that is thought to bind to an exoreceptor near the beta-receptor. The objective of this study was to compare the protective effect of salmeterol with albuterol against EIA. Exercise was performed 0.5, 2.5, 4.5, and 6.5 hours after administration of the active drugs. Subjects attended the laboratory on four days within six weeks and cycled for 8 min breathing dry compressed air. We studied 17 asthmatic subjects (aged 19 to 49 years) with moderate to severe EIA. Salmeterol (50 micrograms) or albuterol (200 micrograms) was given from a metered dose inhaler via a spacer (Volumatic). On the control day, the mean work load +/- 1 SD was 174 +/- 47 W, ventilation (VE) was 77.9 percent +/- 11.2 percent of the target ventilation (60 percent maximum voluntary ventilation [MVV]), and heart rate was 170 +/- 14 beats per minute. This intensity was maintained for all tests. FEV1 was measured before and after exercise and was expressed as percent predicted and as percentage of the preexercise value (percentage of fall). Thirty minutes after treatment, both drugs were effective in inhibiting EIA--percentage of fall in FEV1, 17 +/- 12 after salmeterol; percentage of fall in FEV1, 15 +/- 15 after albuterol. At 2.5, 4.5, and 6.5 hours, the reduction in FEV1 was significantly less (p less than 0.01) after salmeterol compared with albuterol. At 6.5 hours, the percentage of fall in FEV1 was 20 +/- 10 after salmeterol and 36 +/- 12 after albuterol. Salmeterol also had a more prolonged action as a bronchodilator and values for FEV1 were significantly higher compared with those on albuterol at 4.5 and 6.5 hours. At 6.5 hours, the FEV1 percent predicted was 96 +/- 10 after salmeterol and 84 +/- 12 after albuterol (p less than 0.01). We conclude that the extent of protection against EIA and the bronchodilation induced by both drugs was similar, but that salmeterol has a longer duration of action compared with albuterol. The reason for its superior duration of action may be due to a slower clearance of the drug from the airways.

Effect of GR32191, a potent thromboxane receptor antagonist, on exercise induced bronchoconstriction in asthma.

Previous work suggests a role for mast cell derived mediators in exercise induced asthma. The contribution of newly generated contractile prostaglandins to exercise induced asthma was assessed by using a potent and orally active thromboxane (TP1) receptor antagonist, GR32191. The effect of 120 mg GR32191 on exercise induced asthma was observed in 12 asthmatic subjects. For the exercise challenge the subjects performed six minutes of treadmill exercise, breathing dry air at a work load that had previously been shown to induce a fall in FEV1 of 25% or more from the pre-exercise baseline. No effect of GR32191 on pre-exercise baseline airway calibre was evident. There was no significant difference in the mean maximum percentage fall in FEV1 from baseline after exercise between drug and placebo (placebo 30.2%, GR32191 day 31.6%). It is concluded that the thromboxane antagonist GR32191 has no effect on exercise induced asthma. This suggests that prostaglandins, including PGD2, that act via the thromboxane receptor do not have an important role in exercise induced asthma.

Laryngeal Changes during Exercise and Exercise-Induced Asthma

Exercise-induced asthma is defined as bronchospasm within the distal airways initiated by exercise. Whether the larynx responds to produce an exacerbation or alleviation of symptoms during an attack has never been evaluated. Thirty subjects were tested, including 15 normals and 15 with exercise-induced asthma. Laryngeal response to exercise was determined by measuring the area of the glottic aperture before, during, and after exercise. The glottis was visualized with a flexible laryngoscope and video images were recorded during monitoring of respirations. Asthma was induced in subjects by having them exercise on an ergometer for 10 minutes while breathing dry air at 10 degrees C. Measurements were subsequently made from recorded images and relative glottic areas were compared between groups. Our data quantify the normal physiologic response of the larynx to exercise and demonstrate a substantial laryngeal contribution to asthma induced by exercise.

Effects of Humid Air Breathing during Arm or Treadmill Exercise on Exercise-induced Bronchoconstriction and Refractoriness

Although it has been reported that inhibitory prostaglandins may be a causal factor in exercise refractoriness, it is still unclear whether exercise-induced bronchoconstriction (EIB) and/or other specific "exercise factors" are necessary to trigger their release and render a subject refractory to subsequent exercise. The purpose of this study was to determine whether non-EIB-producing exercise with the legs or arms could produce refractoriness to a standard treadmill challenge. Eight asthmatic subjects with EIB completed three sessions consisting of two exercise challenges separated by a 30-min rest. In all sessions, the second challenge was done on a treadmill while breathing dry air. Conditions for Challenge 1 were the following: Session A = treadmill, dry air; Session B = treadmill, humid air; Session C = arm cranking, humid air. All three conditions produced a significant degree of refractoriness. There was a tendency for the percent protection index to be greater for Session A; however, no significant differences were found among the three sessions. Therefore, it can be concluded that although both exercise and bronchoconstriction may play a role in producing the refractory period, neither severe bronchoconstriction nor intense exercise with the same muscle groups are required to produce refractoriness.

Airway blood flow response to eucapnic dry air hyperventilation in sheep.

Eucapnic hyperventilation, breathing dry air, produces a two- to fivefold increase in airway blood flow in the dog. To determine whether airway blood flow responds similarly in the sheep we studied 16 anesthetized sheep. Seven sheep (1-7) were subjected to two 30-min periods of eucapnic hyperventilation breathing 1) warm humid air [100% relative humidity (rh)] followed by 2) warm dry air [0% rh] at 40 breaths/min. To determine whether there was a dose-response effect on blood flow of increasing levels of hyperventilation of dry air, another nine sheep (8-16) were subjected to four 30-min periods of eucapnic hyperventilation breathing warm humid O2 followed by warm dry O2 at 20 or 40 breaths/min in random sequence. Five minutes before the end of each period of hyperventilation, hemodynamics, blood gases, and tracheal mucosal temperature were measured, and tracheal and bronchial blood flows were determined by injection of 15- or 50-micron-diam radiolabeled microspheres. After the last measurements had been made, all sheep were killed, and the lungs and trachea were removed for determination of blood flow to trachea, bronchi, and parenchyma. In sheep 1-7, warm dry air hyperventilation at 40 breaths/min produced an increase in blood flow to trachea (7.6 +/- 3.5 to 17.0 +/- 6.2 ml/min, P less than 0.05) and bronchi (9.0 +/- 5.4 to 18.2 +/- 8.2 ml/min, P less than 0.05) but not to the parenchyma. When blood flow was compared with the two ventilatory rates (sheep 8-16), tracheal blood flow increased (9.1 +/- 3.3 to 18.2 +/- 6.1 ml/min, P less than 0.05) at a rate of 40 breaths/min but not at 20 breaths/min.(ABSTRACT TRUNCATED AT 250 WORDS)

Nasal mucociliary transport in healthy subjects is slower when breathing dry air

We assessed the effect of dry air (DA) nasal breathing on nasal clearance rate in healthy nonsmoking subjects. We measured saccharin nasal transit time (SNTT), an index of mucociliary clearance rate, in eleven normal subjects (six males, five females) breathing either room air (RA) or DA through the nose in random order on six different study days. On each study day, the trial was conducted at the same time, in the same nostril, using a patent airway. DA was breathed through a light-weight, tight-fitting, nasal mask (SEFAM, France) for 30 min and SNTT was then measured immediately. Saccharin (250 micrograms) was deposited on the anterior part of the inferior turbinate under visual control and saliva was swallowed every 30 s thereafter. SNTT was the time elapsed between deposition and first perception of saccharin taste. The group-average SNTT on DA was 18.5 +/- 8.6 min which was significantly longer than on RA (11.9 +/- 5.3 min). Our findings suggest that dry air breathing results in excessive water loss by the nasal mucosa, which may in turn reduce nasal mucociliary clearance rate through changes in the rheological properties or adhesiveness of nasal mucus and/or slowing of ciliary beating.

Effect of Dry Warm Air on Respiratory Water Loss in Children with Exercise-induced Asthma

The variation in respiratory water loss (RWL) over time, expressed as the mass of water vapor lost per liter (body temperature and pressure, saturated) of ventilation (MH2O), was investigated in two groups: (1) children with exercise-induced asthma; and (2) healthy children. Children were matched for age and sex and went without medication for at least 12 hours before each experiment. The children breathed dry warm air (TI = 28.4 degrees C +/- 0.3 degree C) for 15 minutes while bicycling at constant and moderate work load (50 W). The MH2O was measured by collecting and weighing the expired water vapor (1) at rest breathing in warm conditions of inspired gas (control values), (2) every five minutes during exercise while breathing dry warm air, and (3) four minutes after the end of exercise. Pulmonary function tests were performed before and six minutes after exercise. The results were abnormal only in children with exercise-induced asthma. During exercise, RWL significantly fell (compared to control value) at the tenth and 15th minute in both groups. Whereas normal subjects recovered their initial values for MH2O four minutes after stopping exercise, asthmatic children still had a reduction in respiratory water loss. During exercise, MH2O decreased a little more in healthy than in asthmatic children. The decrease in MH2O in both groups suggests that the means to fully humidify expired gas are overwhelmed by thermal stress. The lack of increase in MH2O in asthmatic children on stopping exercise suggests that the airway mucosa is unable to produce enough water vapor and is thus dehydrated and probably hyperosmotic.

Breathing dry air causes acute epithelial damage and inflammation of the guinea pig trachea.

Drying and cooling of the airways mucosa caused by respiratory water loss may be responsible for exercise- and hyperventilation-induced asthma. Therefore we designed this study to investigate whether breathing dry air is capable of causing structural changes of the airways mucosa. Anesthetized guinea pigs breathed spontaneously through a tracheostomy either dry (n = 15) or water-saturated (n = 12) air at approximately 38 degrees C for 30 or 60 min, during which time total pulmonary resistance (TPR) was measured. Immediately afterward, the animals were killed and the lungs and airways were prepared for histological examination (light microscopy, transmission electron microscopy, and scanning electron microscopy). With dry as well as humid air, there was no change in TPR or in the structure of the main bronchi and lung parenchyma. With humid air the tracheal mucosa was normal in six guinea pigs and exhibited minor changes of the ciliae in eight and localized epithelial damage on light microscopy in the remaining animal. With dry air we found widespread loss of the ciliae on scanning electron microscopy in 10 of 12 animals, associated with detachment or sloughing of the epithelium, subepithelial vascular congestion, edema, and cellular infiltration on light microscopy. Our data demonstrate that a short exposure of the trachea to dry air causes marked epithelial lesions and local inflammation.

Exercise Intensity Determines and Climatic Conditions Modify the Severity of Exercise-induced Asthma

Recent studies have shown some evidence that exercise-induced asthma (EIA) may not be entirely explained by respiratory heat loss (RHL). We investigated the interrelationship between heat exchange, exercise intensity and EIA. In order to differentiate between the effects of RHL and exercise intensity, we arranged for tests to be performed with the same RHL, but with different intensities of exercise and inspired air conditions. Each of 8 asthmatic children exercised twice in random order for 6 min on a cycle ergometer. One test consisted of exercise performed at a greater level of effort while breathing room air, mean (+/- SE) air conditions being 25.0 +/- 0.4 degrees C and 15.7 +/- 0.2 mg H2O/L. The other test was performed at a lesser level of effort while breathing cold (0.0 +/- 0.5 degrees C) and dry air (O mg H2O/L). The mean ratio of minute ventilations in the 2 exercise tests was 1.78 +/- 0.03, but the RHL was similar in both tests. The EIA after the exercise at the greater level was more severe than after the lesser level, the percent fall in FEV2 from baseline being 36 +/- 7% and 21 +/- 5%, respectively (p less than 0.025). We conclude that the exercise level has a major role in determining the severity of EIA and that climatic conditions act as modifying factors.