a 20 year follow up Lung function in adult idiopathic scoliosis: Kerstin Pehrsson, Bjorn Bake, Sven Larsson, Alf Nachemson

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1 474 Deprtment of Lung Medicine K Pehrsson Lrsson Deprtment of Clinicl Physiology B Bke Deprtment of Orthopedics A Nchemson University of Goteborg, Renstr8m's nd hlgren's Hospitls, Goteborg, weden Reprint requests to: Dr K Pehrsson, Renstrom's Hospitl, Box 1731, Goteborg, weden. Accepted 26 April 1991 Lung function in dult idiopthic scoliosis: 2 yer follow up Kerstin Pehrsson, Bjorn Bke, ven Lrsson, Alf Nchemson Abstrct evere idiopthic scoliosis my led to respirtory filure, which cn be treted by ssisted ventiltion. Twenty four ptients with surgiclly untreted idiopthic scoliosis who hd been exmined in 1968 were re-exmined in to ssess chnges in lung function nd risk fctors for respirtory filure. The ptients were ged yers in 1968 nd hd scoliotic ngle of 1-19 nd vitl cpcity of litres. pirometric vlues nd scoliotic ngles were determined in 1968 nd, nd rteril blood gs tensions in. The decline in spirometric vlues over the 2 yers ws of the sme mgnitude s the predicted decline due to ging. Arteril blood gs tensions in were strongly correlted with the scoliotic ngles nd spirometric indices recorded in Hypoxemi nd hypercpni ws seen in four ptients in (then ged yers) nd these were the four ptients who hd vitl cpcity below 43% predicted in The remining 2 ptients hd blood gs vlues within norml limits. Two further ptients hd died from respirtory filure before, so totl of six ptients hd developed respirtory filure. n multiple logistic nlysis vitl cpcity expressed s % predicted in 1968 ws the strongest predictor of the development of respirtory filure, followed by the scoliotic ngle. Respirtory filure occurred only in ptients who hd vitl cpcity below 45% predicted in 1968 nd n ngle greter thn 11. Thus respirtory filure develops in dults with scoliosis with lrge ngle nd low vitl cpcity when norml ging reduces the ventiltory cpcity further. uch individuls merit close follow up. Ptients with untreted scoliosis run n incresed risk of developing respirtory filure'2 nd of premture deth.34 urgicl tretment with Hrrington instrumenttion nd fusion hs been used in weden since n these ptients the risk of severe impirment of lung function5 is low. There re still ptients older thn 4 yers, however, who hve not undergone surgery nd who run n incresed risk of developing respirtory filure. We decided to study the long term Thorx 1991;46:47478 chnges in lung function nd its reltion to respirtory filure in ptients with untreted idiopthic scoliosis. n 1968 group of ptients with scoliosis ws studied in Goteborg nd scoliotic ngles, lung function, nd respirtory symptoms were ssessed.67 We hve now re-exmined those with unfused idiopthic scoliosis nd nlysed the dt on chnge in lung function, presence of respirtory filure, nd deth. The purpose ws to investigte the decline in lung function nd to identify risk fctors for the development of respirtory filure. Methods PATENT The ptients in the present study were tken from group of 45 ptients with scoliosis studied in 1968 by Bjure et l6 nd Bke et l.' Between 1968 nd eight ptients died, ll with unfused idiopthic scoliosis. Two ptients could not be trced, one ptient did not wish to tke prt in the present investigtion, nd seven ptients born in the 194s or 195s hd undergone spinl fusion. Three were excluded becuse they hd prlytic scoliosis. Hence 24 ptients with unfused idiopthic scoliosis remined for follow up in. The ge of the 24 ptients rnged from 15 to 67 yers in 1968, the scoliotic ngles from 1 to 19 nd the vitl cpcity from 1 to 6 litres. The scoliotic curves were clssified s thorcic if the picl vertebr ws between the third nd 1th thorcic vertebre nd s thorcolumbr if the pex of the curve ws between the 11th thorcic nd the second lumbr vertebre. No pure lumbr curves were seen but one ptient hd double primry curve. TUDY PROTOCOL n both nd 1968 we elicited (1) scoliotic ngles; (2) respirtory symptoms nd smoking hbits ccording to questionnire; (3) qusi-sttic vitl cpcity (VC), functionl residul cpcity (FRC), residul volume (RV), totl lung cpcity (TLC), nd forced expirtory volume in one second (FEV,). n we obtined in ddition (1) dignoses ccording to deth certifictes; (2) vilble cse records; (3) VC in supine position, mximl inspirtory pressure (MP), mximl expirtory pressure (MEP), nd rteril blood gs tensions. Thorx: first published s /thx on 1 July Downloded from on 6 July 218 by guest. Protected by copyright.

2 Lungfunction in dult idiopthic scoliosis: 2yerfollow up 475 Tble 1 Lung function results obtined in 1968 nd in in 24 ptients with unfused idiopthic scoliosis Men D n Men D n VC(1) VC (% pred) FEV,(1) FRC(1) RV(1) TLC(1) VC supine (1) MP (% pred) MEP (% pred) Po2 (kp) Pco2 (kp) tndrd bicrbonte (mmol/l) VC-vitl cpcity; FEV-forced expirtory volume in one second; FRC-functionl residul cpcity; RV-residul volume; TLC-totl lung cpcity; MP-mximum inspirtory pressure; MEP-mximum expirtory pressure; Pol-rteril oxygen tension; Pcol-rteril crbon dioxide tension. Percent of predicted norml , u v.5 U vc DETERMNATON OF THE DEGREE OF COLO (COBB) The scoliotic ngle ws determined by the sme orthopedic surgeon in s in Determintion of the picl vertebr nd ngle ws mde ccording to the method of Cobb8 from rdiogrphs tken in the stnding position. i FEVZ Figure ndividul results of some lung function tests from expresse predicted. The horizontl lines give men vlues. The four ptients with re! spirtory filure () re in the low rnge, especilly with regrd to vitl cpcity (1 T'C) nd totl lung cpcity (TLC). FEV%-forced expirtory volume in one second s VC; MP-mximum inspirtory pressure; MEP-mximum expirtory pressure... TLC -- MP QUETONNARE The sme trnsltion of British questionnire9 of respirtory symptoms ws used in 1968 nd in. t contins questions bout cough, phlegm, wheezing, dyspnoe, nd smoking hbits. Dyspnoe severity ws grded from 1 to 5. Grde 3 mens brethlessness when the subject is wlking with someone else on level ground. LUNG FUNCTON NVETGATON ttic lung volumes were determined by the helium dilution technique. FEV1 nd VC were mesured with wter spirometer (Bernstein) in the sitting position on both occsions nd in the supine position in. The sme lbortory technicin performed the investigtions in 1968 nd. Norml vlues were predicted ccording to formule from Berglund et ll' nd were corrected for VC for loss of height due to scoliosis ccording to the formul of Lindh nd Bjure.5 Mximl inspirtory pressure nd mximl expirtory pressure were obtined t FRC." 12 Norml vlues were predicted from Decrmer et l" nd Lurie et l.'2 Arteril blood gs mesurements, including oxygen tension (Po2), crbon dioxide tension (Pco2), nd stndrd bicrbonte, were determined (Rdiometer ABL2) in smples of blood obtined from the ptient when semirecumbent fter 1 minutes' rest. Respirtory filure ws defined s Po2 below 8 kp or PCo2 bove 6-5 kp, or both. TATTC Fisher's non-prmetric permuttion test'3 ws used for comprison between groups. A multivrite nlysis of predictors for respirtory filure ws crried out with stepwise logistic model.'4 Results The eight ptients studied in 1968 (five women nd three men) who hd died during the follow up period hd men ge t deth of 67 yers. Respirtory filure due to scoliosis ws the cuse of deth in two ptients (ged 54 nd 75 yers) ccording to their deth certifictes nd! cse records. They re included in the nlysis of risk for development of respirtory filure (see below). The men ge of the 24 ptients t follow up in ws 62 yers. There were 2 women nd four men. Twenty of the 24 ptients were ble to complete the study protocol nd four ptients cooperted only with the blood gs determintion. MEAUREMENT PERFORMED N (TABLE 1, FG 1). Men VC ws 2-1 litres (64% predicted) nd -r men TLC 3-9 1(75% predicted). M E P Respirtory filure ws present in four of the 24 ptients. Their blood gs vlues showed?d s % combintion of low Po2 ( kp) nd n incresed PCo2 (68-6 kp). percentge of Men supine VC ws 2-1 in the 2 ptients who were ble to cooperte. n three ptients Thorx: first published s /thx on 1 July Downloded from on 6 July 218 by guest. Protected by copyright.

3 476 Pehrsson, Bke, Lrsson, Nchemson Figure 2 Vitl cpcity (VC, % predicted) nd scoliotic ngles in 1968 plotted ginst rteril blood gs tensions in. The closed circles indicte the four ptients with respirtoryfilure. The correltion coefficients between VC % predicted in 1968 nd blood gs vlues (rteril oxygen nd crbon dioxide tensions) (Po2, Pco,) nd stndrd bicrbonte (BC)) in in n inverse model (y = + b/x) were - 74, 86, nd 72. Tble 2 Numbers ofptients who hd respirtory symptoms nd who smoked, ccording to questionnire nswered by 14 ptients with idiopthic nd unfused scoliosis in 1968 nd Cough 4 6 Phlegm 2 3 Wheezing 9 8 Dyspnoe 5 8 Current smokers 8 2 VC fell by more thn 15% on lying supine (VC sitting -VC supine) x 1/VC sitting). MP nd MEP showed wide vrition (fig 1). Men MP ws 47% of predicted (rnge %), nd men MEP 51% of predicted (rnge 5-97%). There ws no significnt correltion between rteril blood gs tensions in nd MP or MEP. COMPARON BETWEEN REULT N 1968 AND N The scoliotic ngle incresed in four ptients (from 3 to 4, 4 to 7, 4 to 55, nd 1 Co - V co ) Co ~ Co 1-3- E 2- r)1 e 8 49 Qeo to 125) nd ws unchnged in the rest of the group. This resulted in men (D) increse from 79 (49) to 86 (46). The respirtory symptoms nd smoking hbits, reported in the questionnires in 1968 nd by 14 ptients (it ws possible to trce only 14 questionnires from 1968), re summrised in tble 2. Wheezing nd dyspnoe were common symptoms on both occsions; the number of smokers hd decresed considerbly by. The men decline in both VC nd FEV, ws 4 1 (tble 1). PROGNOTC MPORTANCE OF REULT OBTANED N 1968 Arteril blood gs tensions obtined in re plotted in figure 2 ginst the scoliotic ngles nd VC % predicted determined in Both scoliotic ngles nd spirometric results showed strong non-liner correltions with blood gs tensions (p < -1). There is threshold vlue for the development of respirtory filure t VC recorded in 1968 of round 43%. The four ptients with VC below 43% predicted 12-1 Q 8- u.-t 12 8 ooooe g.. N -- V.... v o O OCP 8o8 8 o % ; o o o o Thorx: first published s /thx on 1 July Downloded from on 6 July 218 by guest. Protected by copyright. v 4 8 VC (% pred) --- no 12l Angle ()

4 Lungfunction in dult idiopthic scoliosis: 2yerfollow up 477 Tble 3 Comprison between vrious vribles determined in 1968 in ptients with nd without respirtory filure in Respirtory filure (n = 6) No respirtory filure (n = 2) Men EM Men EM A Angle( ) < 1 VC(1) <1 VC (% pred) < 1 VC (% pred, no correction) < 1 FEV, (1) <1 TLC ()t < 1 Dyspnoe < 5 Wheezing < 5 For loss of height due to scoliosis. tn = 4 nd 17. n = 6 nd 15. Dyspnoe ws rnked from 1 to 5, with incresing severity. Absence of wheezing ws grded s nd wheezing s 1. For FRC, RV, nd smoking hbit differences were non-significnt. Abbrevitions s in tble 1. in 1968 hd hypoxemi nd hypercpni in. The remining 2 ptients hd norml Po2 nd Pco2 vlues. ix of the ptients (two ded nd four living) with unfused idiopthic scoliosis developed respirtory filure during the follow up period; 2 ptients remined without respirtory filure. The results of the nlysis designed to predict the development of respirtory filure re s follows. A univrite nlysis between respirtory filure nd the different vribles obtined in 1968 ws crried out initilly nd showed tht lrge ngle, low spirometric vlues nd low TLC were strong predictors of the development of respirtory filure (tble 3). When respirtory symptoms nd smoking hbits in 1968 were relted to respirtory filure there ws sttisticl correltion for dyspnoe nd wheezing but not for smoking hbits. The reltive order of importnce of the different risk fctors ws then described on the bsis of multivrite stepwise logistic nlysis. VC % predicted in 1968 ws the strongest predictor nd ws the only vrible selected by this procedure. This vrible correctly predicted the presence or bsence of respirtory filure in in ll ptients. The scoliotic ngle in 1968 clssified 25 of 26 ptients correctly. The spirometric results nd the ngle were highly correlted; hence they excluded ech other in the multivrite nlysis. Discussion The lung function results recorded in in this study re in line with results reported by other investigtors'5 in cross sectionl studies of ptients with idiopthic scoliosis. The scoliosis ws clssified s idiopthic on the bsis of detiled clinicl exmintion. We found restrictive ventiltory impirment with low men VC nd TLC (tble 1, fig 1). These mesurements were strongly nd inversely relted to the scoliotic ngle. There ws wide rnge of MP nd MEP in our ptients (tble 1, fig 1), s in the norml popultion." 12 The men vlues were reduced, however, to 47% nd 51% predicted, indicting low respirtory muscle efficiency in our ptients. This is lso in line with results of other studies.'61' The mechnicl efficiency of the respirtory muscles, especilly the diphrgm, is probbly reduced by the unfvourble position of the diphrgm in severely distorted chest.'6 Lisbo et ll7 found significnt correltion between MP nd both Po, nd Pco2 in ptients with severe scoliosis. The present study did not confirm those results, s we found no correltion between blood gses nd either MP or MEP. The strongest predictors of respirtory filure in were lrge scoliotic ngle nd low spirometric results in The ptients in this study hd reched skeletl mturity in 1968 without developing respirtory filure. n such ptients respirtory filure might develop when there is further reduction of VC. Theoreticlly VC might deteriorte in these ptients more rpidly thn in people without scoliosis becuse of incresing deformity of the chest or other fctors, or it might decline s expected s result of ging. n the present study there ws no support for the first possibility. None of the ptients who developed respirtory filure hd progression of the thorcic curves. ncresing curves hve been reported by Weinstein nd Ponseti,'8 especilly in thorcic curves tht hd reched 5 8 t skeletl mturity. Our results show tht respirtory filure my develop despite n unchnged scoliotic ngle. An exggerted decline in VC due to other fctors might lso in some cses led to respirtory filure. This ws suggested by Brnthwite,2 who retrospectively collected lung function vlues from group of ptients with idiopthic scoliosis. Two ptients (fig 3) in the present study showed n exggerted decline of spirometric vlues despite n unchnged scoliotic ngle. n one the decline might be relted to the scoliotic process s she hd reduced mobility of the right hemidiphrgm nd lrge diphrgmtic herni. Poor diphrgmtic function in this ptient might be relted to the scoliosis. The other ptient ws n obese smoker. The expected reduction of VC resulting from incresing ge might provoke respirtory filure in ptients with severe idiopthic scoliosis. n our study the ptients s group showed only ge predicted chnges between 1968 nd (tble 1) nd the sme is true for the ptients who developed respirtory filure (fig 3). The expected decline due to incresing Thorx: first published s /thx on 1 July Downloded from on 6 July 218 by guest. Protected by copyright.

5 478 Figure 3 ndividul mesurements of vitl cpcity (VC) ndforced expirtory volume in one second (FEV,) in 1968 nd in. The four ptients with respirtory filure (broken lines) strted with the lowest vlues nd declined ccording to the ge prediction. - VC () ws 4 1..,: ::::::::::::::. : ge (clculted for sex rtio of 17 women nd 3 men) is 4 1 for VC nd -6 1 for FEVy. n our study the men decline in both VC nd FEV, Our results suggest therefore tht in dult ptients with idiopthic scoliosis ging is the mjor cuse of decline in VC nd therefore of the development of respirtory filure. ix ptients hd developed respirtory filure during the follow up, none hving hd respirtory filure in 1968 ccording to cse records. The picl vertebr ws locted between 6 nd 9 in these ptients. The scoliosis ws convex to the right in four nd to the left in two. Nchemson3 nd Nilsonne4 in two studies in 1968 described n incresed mortlity due to respirtory filure in ptients with idiopthic scoliosis. n contrst, Weinstein'9 in 1981 in follow up of round 2 ptients with idiopthic scoliosis reported tht their mortlity ws similr to tht of the norml popultion. Furthermore he reported 16 ptients with thorcic scoliotic ngle greter thn 8 nd yet found no one with respirtory filure. Our study confirms tht respirtory filure develops in some ptients with idiopthic scoliosis. Predicting the development of respirtory filure in the future for ptient with unfused scoliosis is importnt so tht respirtory filure cn be recognised t n erly stge, when tretment with ssisted ventiltion t night improves respirtory function2 nd qulity of sleep nd my prolong life.2' This study confirms tht scoliotic ngle greter thn 11, dyspnoe, nd wheeze re mrkers of poor prognosis tht cll for follow up. Our min finding is tht ptients with idiopthic scoliosis who hve reched skeletl mturity nd hve VC below 45% predicted run n incresed risk of developing respirtory filure when the ging process further reduces their lung function. uch ptients should be followed crefully to recognise respirtory filure t n erly stge. The study ws supported by the wedish Hert-Lung Foundtion nd the Goteborg Medicl ociety. We thnk lbortory FEV, (1) 6-2- Pehrsson, Bke, Lrsson, Nchemson technicin Eivor Jonsson for her skilful technicl ssistnce nd Nils-Gunnr Pehrsson for expert sttisticl guidnce. 1 Bergofsky EH. Respirtory filure in disorders of the thorcic cge. Am Rev Respir Dis 1979;119: Brnthwite MA. Crdiorespirtory consequences of unfused idiopthic scoliosis. Br J Dis Chest 1986;8: Nchemson A. A long term follow-up study of non-treted scoliosis. Act Orthop cnd 1968;39: Nilsonne U, Lundgren K-D. Long-term prognosis in idiopthic scoliosis. Act Orthop cnd 1968;39: Lindh M, Bjure J. Lung volumes in scoliosis before nd fter correction by the Hrrington instrumenttion method. Act Orthop cnd 1975;46: Bjure J, Grimby G, Kslichy J, Lindh M, Nchemson A. Respirtory impirment nd irwys closure in ptients with untreted idiopthic scoliosis. Thorx 197;25: Bke B, Bjure J, Kslichy J, Nchemson A. Regionl pulmonry ventiltion nd perfuson distribution in ptients with untreted idiopthic scoliosis. Thorx 1972;27: Cobb JR. Outline for the study of scoliosis. Am Acd Orthop urg Lect 1948;5: Chronic bronchitis in Gret Britin. A ntionl survey crried out by the respirtory diseses study group of the college of generl prctitioners. Br Med J 1961;ii: Berglund E, Birth G, Bjure J, et l. pirometric studies in norml subjects. Act Med cnd 1963;173: Decrmer M, Demedts M, Rochette F, Billiet L. Mximl trnsrespirtory pressures in obstructive lung disese. Bull Eur Physiopthol Respir 198;16: Lurie M, Cidhl K, Johnsson G, Bke B. Respirtory function in chronic primry fibromylgi. cnd J Rehb Med 199;22: Brdley JV. Distribution-free sttisticl test. London: Prentice-Hll, 1968: Press J, Wilson. Choosing between logistic regression nd discriminnt nlysis. Journl of the Americn ttisticl Assocition 1978;73: Kfer ER. diopthic scoliosis. Mechnicl properties of the respirtory system nd the ventiltory response to crbon dioxide. J Clin nvest 1975;55: Jones R, Kennedy JD, Hshm F, Oven R, Tylor JF. Mechnicl inefficiency in the thorcic cge in scoliosis. Thorx 1981;36: Lisbo C, Moreno R, Fv M, Ferretti R, Cruz E. nspirtory muscle function in ptients with severe kyphoscoliosis. Am Rev Respir Dis 1985;132: Weinstein L, Ponseti. Curve progression in idiopthic scoliosis. Long-term follow-up. J Bone Joint urg 1983;65A: Weinstein L, Zvl DC, Ponseti V. diopthic scoliosis. Long term follow-up nd prognosis in untreted ptients. J Bone Joint urg 1981;63A: Ellis ER, Grunstein RR, hu Chn, Bye PTP, ullivn CE. Noninvsive ventiltory support during sleep improves respirtory filure in kyphoscoliosis. Chest ;94: Gerrd M, Robert D, lmnd J, Bufft J, Chemorin B, Bertoye A. Etude de l survie chez 15 insuffisnts respirtoires chroniques trcheotomises trites pr l ventiltion ssistee domicile. Lyon Medicl 1981; 245: Thorx: first published s /thx on 1 July Downloded from on 6 July 218 by guest. Protected by copyright.