Effects of BMI on Static Lung Volumes in Patients With Airway Obstruction

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1 CHEST Effects of BMI on Sttic Lung Volumes in Ptients With Airwy Obstruction Originl Reserch Denis E. O Donnell, MD, FCCP ; Athvudh Deesomchok, MD ; Yuk-Miu Lm, PhD ; Jordn A. Guenette, PhD ; Nprt Amornputtisthporn, MD ; Lutz Forkert, MD ; nd Ktherine A. Webb, MSc PULMONARY PHYSIOLOGY Bckground: Both chronic irwy obstruction nd obesity re incresing in prevlence but the effect of their combintion on pulmonry function prmeters cross the rnge of irwy obstruction is unknown. Methods: We studied the impct of incresing BMI on sttic lung volumes nd irwy function in cohort of 2,265 subjects from lrge pulmonry function lbortory dtbse who were 40 to 80 yers of ge nd met GOLD (Globl Inititive for Chronic Obstructive Lung Disese) spirometric criteri for COPD (postbronchodiltor /FVC, 0.7). We lso evluted the influence of severity of irwy obstruction (by GOLD criteri) on these reltionships. Results: With incresing BMI in the group s whole, functionl residul cpcity, residul volume, expirtory reserve volume, nd specific irwy resistnce (srw) decresed exponentilly (ll P,.001); totl lung cpcity (TLC) decresed linerly ( P,.001); nd inspirtory cpcity (IC) nd IC/TLC incresed linerly ( P,.001). However, vitl cpcity ws not influenced significntly. The effects of incresing BMI on /FVC nd srw were gretest in GOLD stge III/IV ( P,.05), wheres incresing BMI hd greter effects on IC in GOLD stge I ( P,.001). Conclusions: With incresing BMI, subjects with irwy obstruction hd consistent reductions in lung hyperinfltion, with significnt improvements in IC nd the /FVC rtio; this effect ws gretest in ptients with the most severe irwy obstruction. These results hve importnt implictions for the clinicl ssessment of ptients with combined obesity nd irwy obstruction. CHEST 2011; 140(2): Abbrevitions: ANOVA 5 nlysis of vrince; D lco 5 diffusing cpcity of the lung for crbon monoxide; ERV 5 expirtory reserve volume; FRC 5 functionl residul cpcity; GOLD 5 Globl Inititive for Chronic Obstructive Lung Disese; IC 5 inspirtory cpcity; LLN 5 lower limit of norml; NW 5 norml weight; OB 5 obese; OW 5 overweight; Rw 5 irwy resistnce; RV 5 residul volume; srw 5 specific irwy resistnce; TLC 5 totl lung cpcity; UW 5 underweight; VC 5 vitl cpcity The prevlence of obesity is incresing drmticlly throughout the Western world. 1 It is well estblished tht obesity cn result in respirtory impirment nd incresed respirtory symptoms, even in individuls without irwy obstruction. 2,3 The min Mnuscript received October 7, 2010; revision ccepted Jnury 14, Affilitions: From the Deprtment of Medicine (Drs O Donnell, Deesomchok, Guenette, Amornputtisthporn, nd Forkert nd Ms Webb), Queen s University nd Kingston Generl Hospitl; nd the Deprtment of Community Helth nd Epidemiology (Dr Lm), Queen s University, Kingston, ON, Cnd. Funding/Support: The uthors hve reported to CHEST tht no funding ws received for this study. Correspondence to : Denis E. O Donnell, MD, FCCP, 102 Sturt St, Kingston, ON, K7L 2V6, Cnd; e-mil: odonnell@ queensu.c physiologic effects of simple obesity include reduced respirtory system complince, incresed work nd oxygen cost of brething, nd incresed peripherl irwy closure.4,5 In cohort of individuls without irwy obstruction (prebronchodiltor /FVC. 90% predicted), Jones nd Nzekwu 6 confirmed n inverse reltion between incresing BMI nd sttic lung volume components. In tht study, it ws estblished tht reltively smll increses in BMI (ie, the overweight [OW] rnge) hd profound effects on functionl 2011 Americn College of Chest Physicins. Reproduction of this rticle is prohibited without written permission from the Americn College of Chest Physicins ( site/misc/reprints.xhtml ). DOI: /chest CHEST / 140 / 2 / AUGUST,

2 residul cpcity (FRC) nd expirtory reserve volume (ERV). The interction between incresing BMI nd lung volumes in individuls with underlying irwy obstruction is less well estblished. Recent studies in sthm hve indicted tht the reltion between BMI nd lung volumes ppers to be similr to tht described in popultions without irwy obstruction. 7,8 Informtion is lcking on the effect of BMI on plethysmogrphic lung volume mesurements in ptients with COPD. This informtion becomes importnt for ccurte interprettion of pulmonry function tests in n ever-incresing number of ptients in whom obesity nd chronic irwy obstruction coexist. In ptients with COPD, lung hyperinfltion with reduction in inspirtory cpcity (IC) hs been ssocited with poor exercise performnce, incresed exertionl dyspne, dynmic crdiovsculr dysfunction, nd even incresed mortlity It follows tht fctors tht cn potentilly mitigte lung hyperinfltion, such s incresed BMI, my hve some fvorble physiologic nd prognostic influences. 14,15 Therefore, the min focus of the current study ws to exmine the reltion between BMI nd lung volumes in cohort of individuls with irwy obstruction of vrious severity. Bsed on previous physiologic studies on the impct of obesity in helth, sthm, nd COPD, 7,8,14,15 w e postulted tht the inverse reltionship between BMI nd sttic lung volumes (ie, FRC nd ERV) would be present in individuls with irwy obstruction cross the rnge of severity. To test this hypothesis, we conducted retrospective nlysis of lrge pulmonry function lbortory dtbse from tertiry cre fcility. Our study popultion consisted of dults who hd irwy obstruction (postbronchodiltor /FVC, 0.7) tht ws not fully reversible nd were likely minly composed of ptients with COPD. We exmined the reltionship between BMI nd plethysmogrphic lung volumes nd cpcities, s well s spirometric indices of irwy function in the group s whole. Finlly, we exmined the influence of sex nd severity of irwy obstruction (by GOLD [Globl Inititive for Chronic Obstructive Lung Disese] criteri) 16 on these reltionships. nd women 40 to 80 yers of ge; BMI, 14 to 55 kg/m 2 (ie, to exclude mesurements outside the bulk of the frequency distribution tht re ssocited with extreme sttisticl uncertinty); postbronchodiltor /FVC, 0.7; vilbility of postbronchodiltor lung volumes mesured by body plethysmogrphy; nd the bsence of dignosis of ny lung disese other thn COPD. In the cse of multiple tests within ptient, only the first visit meeting eligibility criteri were used for nlysis. Subjects were strtified by BMI: underweight (UW), 14 to kg/m 2 ; norml weight (NW), 18.5 to kg/m 2 ; OW 25 to kg/m 2 ; nd obese (OB), 30 to 55 kg/m Subjects were lso evluted ccording to GOLD stge criteri 16 : GOLD stges III nd IV were combined becuse only 74 ptients hd postbronchodiltor, 30% predicted nd the presence of chronic respirtory filure could not be confirmed. The Queen s University nd Affilited Teching Hospitls Reserch Ethics Bord pproved the use of these dt nd wived the need for ptient informed consent (DMED ). Procedures Spirometry, body plethysmogrphy, nd single-breth diffusing cpcity of the lung for crbon monoxide (D lco ) were performed by experienced respirtory therpists/technicins using utomted testing equipment (2130 spirometer with 6200 Autobox D L or V6200 Autobox; SensorMedics; Yorb Lind, Cliforni) ccording to recommended stndrds All short-cting nd long-cting bronchodiltors were withdrwn for t lest 4 h nd 12 h, respectively. Bronchodiltor responsiveness (mesured by spirometry nd body plethysmogrphy) ws ssessed 20 min fter inhltion of slbutmol 200 m g by metered dose inhler. Predicted norml vlues were those used in the testing lbortory, with predicted IC clculted s predicted totl lung cpcity (TLC) minus predicted FRC, nd predicted ERV clculted s predicted FRC minus predicted residul volume (RV). The use of these predictive equtions showed good vlidity for mesurements of lung hyperinfltion in helthy, ge-mtched (rnge yers; men 63 yers), nonsmoker popultion studied in our lbortory, but underestimted our lbortory s normtive vlues by t lest 5% for, vitl cpcity (VC), IC, ERV, specific Mterils nd Methods Subjects nd Design Subjects in this study hve been described previously in nonoverlpping nlysis. 17 This retrospective nlysis ws conducted using dt from ptients referred to the Kingston Generl Hospitl s Pulmonry Function Lbortory between My 1992 nd April 2008 for comprehensive pulmonry function tests with bronchodiltor responsiveness. Selection criteri included men Figure 1. The frequency histogrm for BMI shows significnt right skew. Subjects (N 5 2,265) were strtified by BMI: UW, 14 to kg/m 2 ; NW, 18.5 to kg/m 2 ; OW, 25 to kg/m 2 ; nd OB, 30 to 55 kg/m 2. NW 5 norml weight; OB 5 obese; OW 5 overweight; UW 5 underweight. 462 Originl Reserch

3 irwy resistnce (srw), nd D lco. 17 Our normtive dt set hd lower limit of norml (LLN) for /FVC of 74.5% nd 104.9% predicted. Sttisticl Anlysis Vlues re reported s mens SD unless otherwise specified. A P vlue of,.05 ws considered significnt in ll nlyses. Comprisons cross BMI subgroups were performed using nlysis of vrince (ANOVA) with post-hoc testing of significnt vribles crried out using t tests with Bonferroni djustment for multiple comprisons. Primry nlyses were performed on pulmonry function mesurements expressed s percentges of predicted norml vlues. Regression nd ANOVA Models: To evlute the effect of incresing BMI on selected lung function mesurements, liner or nonliner (exponentil or other power trnsformtion under Box-Cox trnsformtion 26 ) regression nlysis ws performed. Regrdless of linerity/nonlinerity, we lso performed threewy ANOVA (with two-fctor interctions) using BMI grouping, GOLD stge, nd sex s ctegoricl vribles. Interction terms were used in the regression model to ccount for the possibility tht BMI, severity of obstruction, nd sex were not independent. A significnt sex 3 BMI interction term indicted difference between men nd women in the reltionship between BMI nd the selected lung function mesurement. A significnt interction between GOLD stge nd BMI grouping indicted tht the BMI effect on prticulr mesurement ws different cross GOLD stge groups. All model fitting ws exmined using residul nlysis, nd regression dignostics were performed to identify possible outliers nd influentil observtions. Results This study included 2,265 subjects (61% men). All subjects hd postbronchodiltor /FVC rtio tht fell below the LLN of 74.5% found in our own normtive dt set, lthough nine older subjects (rnge, y) from the GOLD stge I subgroup were bove the LLN for this rtio when it ws expressed s percent of the predicted vlue. The frequency histogrm for BMI showed slight right skew ( Fig 1 ). This distribution pttern ws similr cross sexes, except men hd modestly higher men thn women: vs kg/m 2, respectively ( P 5.008). Mesurements cross the BMI subgroups re reported in Tble 1. The somewht Tble 1 Subject Chrcteristics Vrible Underweight (n 5 74) Norml Weight (n 5 733) Overweight (n 5 804) Obese (n 5 654) Sex, % mle Age, y BMI, kg/m b Weight, kg b Height, cm GOLD stge, No. (%) I 8 (10.8) 186 (25.4) 231 (28.7) 195 (29.8) II 29 (39.2) 354 (48.3) 405 (50.4) 341 (52.1) III/IV 37 (50.0) 193 (26.3) 168 (10.9) 118 (18.0) /FVC postbronchodiltor, % b postbronchodiltor, % predicted reversibility, L (%) (7 11) (10 12) (10 12) (11 13) Prebronchodiltor pulmonry function, % predicted /FVC, % b FEF 50, % predicted TLC, % predicted b SVC, % predicted b IC, % predicted b IC/TLC, % b FRC, % predicted b RV, % predicted RV/TLC, % ERV, % predicted b Rw, % predicted srw, % predicted D lco, % predicted D lco /V, % predicted b V, % predicted TLC Vlues re mens SD unless otherwise specified. D lco 5 diffusing cpcity of the lung for crbon monoxide; ERV 5 expirtory reserve volume; FEF 50 5 forced expirtory flow t 50% of FVC; FRC 5 functionl residul cpcity; GOLD 5 Globl Inititive for Chronic Obstructive Lung Disese; IC 5 inspirtory cpcity; Rw 5 irwy resistnce; RV 5 residul volume; srw 5 specific irwy resistnce; SVC 5 slow vitl cpcity; TLC 5 totl lung cpcity; V 5 lveolr volume. Bonferroni djusted P,.05 vs norml weight. b P,.05 obese vs overweight. CHEST / 140 / 2 / AUGUST,

4 underrepresented UW subgroup (n 5 74) hd the gretest proportion of subjects within the GOLD III/IV stge nd ws significntly (P,.05) worse thn the NW group for the mjority of pulmonry function mesurements. Within the NW, OW, nd OB subgroups, there ws reltively even distribution of ptients meeting GOLD stge I, II, nd III/IV criteri. BMI Effects on Pulmonry Function Mesurements By simple liner regression, BMI correlted significntly with ll prebronchodiltor nd postbronchodiltor lung function mesurements, except for FVC, SVC, irwy resistnce (Rw), single-breth lveolr volume nd Dlco (ll expressed s % predicted). BMI reltionships with TLC % predicted, IC % predicted, the IC/TLC rtio nd the RV/TLC rtio were liner. RV % predicted, FRC % predicted, ERV % predicted, nd srw % predicted ll decresed exponentilly s BMI incresed (Fig 2). Dt were pooled for men nd women becuse there were no significnt sex 3 BMI interctions for mesurements other thn FRC % predicted (pre, P 5.034; post, P ); this sex difference ws driven by greter (P,.01) decrese in FRC with incresing BMI in men compred with women in GOLD stge III/IV only. Figure 2 shows some of these reltionships. We did not find significnt inverse reltionship between Rw % predicted nd FRC % predicted. Figure 2. Significnt reltionships between BMI nd postbronchodiltor mesurements of FRC % predicted, RV % predicted, ERV % predicted, IC % predicted, IC/TLC, nd srw % predicted re shown. Regression equtions re shown for ech reltionship. ERV 5 expirtory reserve volume; exp 5 exponentil function; FRC 5 functionl residul cpcity; IC 5 inspirtory cpcity; RV 5 residul volume; srw 5 specific irwy resistnce; TLC 5 totl lung cpcity. 464 Originl Reserch

5 Effects of BMI Across Vrious Severities of Airflow Obstruction Lung volume components cross BMI nd GOLD subgroups re summrized in Figure 3. There ws significnt BMI 3 GOLD interction for /FVC (pre, P 5.011; post, P ), IC % predicted (pre, P ; post, P,.0001), IC/TLC (pre, P ; post, P ), FRC/TLC (pre, P ; post, P,.0001), ERV % predicted (pre, P,.0001; post, P,.0001), nd srw % predicted (pre, P 5.031; post, P,.0001). Mens of severl key spirometric nd plethysmogrphic mesurements cross GOLD stges re shown within ech BMI subgroup in Figure 4. Discussion The min findings of this study re s follows: (1) Sttic lung volume components FRC nd RV decresed exponentilly with incresing BMI in this cohort with bseline irwy obstruction. (2) The ssocition between lung volume reduction nd obesity ws present regrdless of the severity of irwy obstruction by GOLD criteri. (3) In this cohort with irwy obstruction, IC incresed linerly s BMI incresed. This cohort ws composed of individuls referred to tertiry cre pulmonry function lbortory for detiled physiologic ssessment. The testing ws stndrdized using Americn Thorcic Society criteri nd ws conducted by three experienced technicins. Given the referrl pttern, the mjority of this smple likely hd respirtory symptoms. By entry criteri, subjects hd irflow obstruction tht ws not fully reversible. The BMI distribution showed smll right-sided skew, reflecting inclusion of subjects with morbid obesity. Approximtely 30% hd BMI vlues in the OB rnge. With the exception of the under- Figure 3. Postbronchodiltor lung volume components re shown divided by GOLD stge nd BMI. The Norml column represents mesurements from previously studied ge-mtched, helthy, nonsmoker popultion. 12 GOLD 5 Globl Inititive for Chronic Obstructive Lung Disese. See Figure 1 nd 2 legends for expnsion of other bbrevitions. represented UW group, the three other subgroups strtified by BMI were well mtched for ge, sex, nd GOLD stge distribution. Reduced sttic respirtory system complince is well estblished s mjor physiologic effect of mss loding of the chest nd bdomen in obesity. 27,28 Jones nd Nzekwu 6 demonstrted tht even smll increses in BMI in the OW rnge hd consistent volume-reducing effects on FRC nd ERV in cohort without irwy obstruction. The current study confirms tht this effect persists in the presence of irwy obstruction. Thus, both prebronchodiltor nd postbronchodiltor FRC nd RV decresed exponentilly s BMI incresed within the group s whole. Accordingly, the most profound effects on lung volume components were seen within the OW BMI rnge nd tpered off s BMI incresed. 30 kg/m2 ( Fig 2 ). For exmple, for every unit increse in BMI up to 30 kg/m 2, postbronchodiltor FRC nd RV decresed by n verge of 3.6% predicted, wheres for every unit of increse in BMI bove 30 kg/m 2, the reduction in FRC nd RV fell to pproximtely 1% predicted. When compring OB with NW ptients of similr, FRC ws reduced by n verge of 0.7 L in the former. Incresing BMI ws ssocited with liner increses in resting IC nd the IC/TLC rtio. These indices of lung hyperinfltion hve emerged s independent predictors of both respirtory nd ll-cuse mortlity in ptients with COPD. 12,13 In ddition, IC expressed s % predicted correltes well with pek symptomlimited oxygen uptke during incrementl cycle exercise, 9,10 nother independent predictor of mortlity in COPD.12,29 Moreover, smll improvements in IC following phrmcologic or surgicl lung volume reduction hve been ssocited with improved dyspne nd exercise endurnce in COPD. 30,31 It is, therefore, possible tht the reltively reduced lung hyperinfltion (nd incresed IC/TLC) in OW, reltive to normlweight, ptients with irwy obstruction my crry some physiologic dvntges. Indeed, recent studies hve provided evidence tht the reduced FRC nd incresed resting IC in ptients with combined obesity nd irwy obstruction (sthm or COPD) prtly counterblnce the negtive effects of dynmic pulmonry hyperinfltion on the respirtory muscles during either induced bronchoconstriction/hyperinfltion in sthm or weight-supported cycle exercise in COPD. 8,14 In contrst to previous study in helthy individuls where VC ws shown to decrese in liner fshion with incresing BMI, no such reltionship ws seen in our subjects with irwy obstruction. Thus, RV decresed exponentilly with incresing BMI but reciprocl increse in VC did not occur; incresing BMI hd miniml effect on the RV/TLC rtio. CHEST / 140 / 2 / AUGUST,

6 Figure 4. The effect of incresing BMI is shown on the progression of postbronchodiltor mesurements of % predicted, /FVC, FRC % predicted, IC % predicted, RV % predicted, nd srw % predicted cross GOLD stge subgroups. Arrows indicte reltionships with significnt ( P.0005) interction between BMI group nd GOLD stge (ie, the BMI effect on these mesurements ws different cross GOLD stges). See Figure 1-3 legends for expnsion of bbrevitions. In helth, incresing BMI is known to be ssocited with incresing single-breth D lco,32 possibly reflecting the incresed pulmonry blood volume in obesity.33,34 In the current study, no consistent reltionship ws found between incresing BMI nd D lco in individuls with irwy obstruction. It is well estblished tht, in helth, Rw normlly increses s lung volume declines. 35 As seen in the current study, the presence of irwy obstruction (nd lung hyperinfltion) my disrupt the norml reltionship between decresing lung volume nd incresed Rw tht occurs with obesity per se. In contrst to findings reported in helth, 36 we did not find n inverse reltionship between Rw nd FRC in our study group, wheres we did find significnt ssocition between srw nd the level of obesity. In fct, in those with severe obstruction, srw ws modestly better in the hevier groups compred with the NW. The lower srw (ie, product of Rw nd thorcic gs volume) in those with the highest BMI likely reflects the lung volume-reducing effect of obesity. Most of the reltionships between BMI nd lung volume components nd irwy function were not influenced by GOLD stge. An exception ws tht in the GOLD I group, the preservtion of IC with incresing BMI ws more pronounced thn in the higher GOLD stges. Whether this volume effect hs 466 Originl Reserch

7 functionl or prognostic implictions remins to be determined. Limittions This popultion ws not chrcterized comprehensively for smoking history, dignosis, mediction use, symptom intensity, or comorbidities. Although the predominnt dignosis ws likely COPD, we cnnot exclude the possibility tht some ptients hd sthm or other obstructive irwy diseses. The use of GOLD fixed rtio criteri vs LLN criteri my hve overestimted irwy obstruction in the elderly nd underestimted obstruction in the young. However, even ptients meeting GOLD stge I criteri hd significntly incresed lung hyperinfltion, incresed Rw, nd configurtionl chnges in the expirtory flowvolume loop tht suggested the presence of respirtory impirment beyond the effects of helthy ging. In ccordnce with the referrl pttern nd the inclusion criteri, ll hd some degree of irreversible irwy obstruction (by both GOLD nd LLN criteri) nd were likely to suffer from respirtory symptoms. No dt on body composition were vilble. The study popultion ws lmost exclusively white, with stisfctory proportionl representtion of sex, wide rnge of ges between 40 nd 80 y, nd with wide, but normlly distributed, rnge of irwy obstruction. Nonetheless, cre must be tken in extrpolting the results to other popultions. Finlly, s with ny retrospective nlysis, we cn highlight importnt ssocitions or reltionships but cnnot estblish cuse nd effect. Conclusions This is the first study to exmine the reltionship between incresing BMI nd prebronchodiltor nd postbronchodiltor plethysmogrphic lung volumes in popultion with irflow obstruction. FRC nd RV decresed exponentilly with incresing BMI, wheres VC ws not consistently relted to BMI. IC ws better preserved s function of incresing BMI, prticulrly in GOLD stge I. The ssocition between incresing BMI nd decresing FRC occurred regrdless of bseline. The reltionship between incresing BMI nd lung volumes nd cpcities in ptients with irflow obstruction hs potentilly importnt implictions for the ccurte interprettion of these common pulmonry function tests. Indices of lung hyperinfltion (eg, FRC. 120 % predicted) re incresingly used s entry criteri for phrmcologic studies without considering the effects of BMI; 30,37 mny ptients with COPD not meeting these criteri becuse of obesity re excluded from entry, which my hve implictions for the generlizbility of the results. IC nd IC/TLC rtios re used s independent predictors of mortlity in COPD popultions without, in some instnces, considering the influence of BMI on these predictive indices. Volume-derived equtions or rtios such s the /FVC nd srw re strongly influenced by the lung volume-reducing effects of incresing weight in ptients with COPD nd should be considered in ny clinicl interprettion of these physiologic prmeters. Bsed on the results of this study, future studies exmining mesurements of lung hyperinfltion should idelly ccount for the influence of BMI. Acknowledgments Author contributions: Dr O Donnell: contributed to the originl ide nd to the content nd writing of the mnuscript. Dr Deesomchok: contributed to performing nd collting the dt nlysis nd prepring it for presenttion nd to the content nd writing of the mnuscript. Dr Lm: contributed to providing sttisticl dvice, supervising the nlysis, nd to the content nd writing of the mnuscript. Dr Guenette: contributed to performing nd collting the dt nlysis nd prepring it for presenttion nd to the content nd writing of the mnuscript. Dr Amornputtisthporn: contributed to performing nd collting the dt nlysis nd prepring it for presenttion nd to the content nd writing of the mnuscript. Dr Forkert: contributed to supervising the pulmonry function lbortory, providing the dtbse, nd to the content nd writing of the mnuscript. Ms Webb: contributed to performing nd collting the dt nlysis nd prepring it for presenttion nd to the content nd writing of the mnuscript. Finncil/nonfinncil disclosures: The uthors hve reported to CHEST the following conflicts of interest: Dr O Donnell hs received reserch funding from Queen s University, Ontrio/ Cndin Thorcic Society, Cndin Institutes of Helth Reserch, AstrZenec, Boehringer Ingelheim, GlxoSmithKline, Merck Frosst Cnd, Novrtis, Nycomed, nd Pfizer Inc. He hs served on spekers bureus, consulttion pnels, nd dvisory bords for AstrZenec, Boehringer Ingelheim, GlxoSmithKline, Nycomed, nd Pfizer Inc. Drs Deesomchok, Lm, Guennette, Amornputtisthporn, nd Forkert nd Ms Webb hve reported tht no potentil conflicts of interest exist with ny compnies/ orgniztions whose products or services my be discussed in this rticle. Other contributions: The uthors cknowledge the pulmonry function lbortory stff Cthy Muir, RRT, RCPT(P); Denis Fubert, BSc, RRT; nd Robin McHrdy, RCPT(P), for their creful ttention to detil when conducting the tests reported s prt of this study. References 1. Interntionl Obesity Tsk Force. Prevlence dt. Interntionl Obesity Tsk Force Web site. index.sp. Lst updted My Accessed October Vele D, Rbec C, Lbn JP. Respirtory complictions of obesity. Brethe ;4(3): Sin DD, Jones RL, Mn SFP. Obesity is risk fctor for dyspne but not for irflow obstruction. Arch Intern Med ; 162 (13): Nimrk A, Chernick RM. Complince of the respirtory system nd its components in helth nd obesity. J Appl Physiol ;15(3): CHEST / 140 / 2 / AUGUST,

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