breathing motion of the chest wall in humans involves both the rib cage and abdomen 
 ( ab)1 . because the functional 
 characteristics of each site differ , studies on ventilation dynamics are generally conducted 
 according to these individual sites2 . furthermore , there is a pressure gradient in both the rib cage and ab3 , 4 and it is believed 
 that , along with anatomical characteristics5 , breathing - associated motion of the rib cage and ab varies according 
 to each local area6 . for example , in the 
 upper rib cage , a pump - handle motion is observed , whereas in the lower rib cage , a 
 bucket - handle motion is observed5 , 7 . the methods used to study these motions 
 include a calculation model2 , 7 and radiography5 ; however , there have been no studies on chest - wall motion of the 
 actual body surface . a typical method for the detailed examination of chest - wall motion is optoelectronic 
 plethysmography ( oep)8 . this method 
 involves dividing the chest wall into three areas , the pulmonary rib cage ( rcp ) , abdominal 
 rib cage ( rca ) , and ab , and then calculating volume changes at each site9 . however , few reports have thoroughly 
 examined the magnitude of chest motion at each location , i.e. , the anterior , dorsal , and 
 lateral surfaces6 . in particular , posture 
 has been reported to affect chest - wall motion10,11,12 , 
 and it is likely that local motion in the chest wall changes in various postures ; however , 
 de groote et al . only reported results for the sitting posture . unlike oep , magnetometry is unable to identify motion 
 direction , and the measurable sites are limited ; therefore , it is difficult to ascertain 
 chest - wall motion comprehensively using this method . in many situations , such as the early 
 postoperative period , clinical evaluation has to be performed in the supine position ; 
 however , this can be difficult on a daily basis using the aforementioned equipment . on the 
 other hand , clarification of changes in chest - wall movement according to each posture may be 
 important for the accurate assessment of changes in chest - wall motion as a result of 
 disease . the purpose of the present study was to examine the effects of posture on the diameter of 
 the chest wall , and the horizontal configuration , motion direction , and magnitude of motion 
 for each local area . to this end , we measured chest - wall motion during breathing at rest 
 using oep in healthy men placed in supine , lateral recumbent , and sitting positions . table 1table 1.subject demographics and anthropometric parametersage ( years)27.5  4.6weight ( kg)66.9  8.9height ( cm)175  7.1bmi ( kg / m)21.8  2.4bmi : body mass index , all data are expressed as means  sd shows the age and body composition values of the subjects . all subjects were 
 provided with a full explanation prior to the study , and the study was performed after 
 obtaining written consent . the study was performed with the approval of the ethical review 
 board of konan women s university . bmi : body mass index , all data are expressed as means  sd chest - wall motion measurements were performed using oep with eight cameras ( mac 3d system , 
 motion analysis corporation , san diego , ca , usa ) . reflective markers ( 9  mm in diameter ) were 
 pasted on the surface of the subject s body . in accordance with previous studies , the 
 reflective markers were pasted on 66 sites in the supine position , 81 sites in the right 
 lateral recumbent position ( lateral recumbent position ) , and 86 sites in the sitting 
 position8 , 12 . furthermore , the supine and lateral recumbent positions were on 
 the floor , and , for the lateral recumbent position , the subject was instructed to prop the 
 left upper arm on a cushion placed on the greater trochanter in order to support the 
 arm12 . in all patients , measurements were recorded for 2  min during breathing at rest in each 
 position , and the order of the measurements was randomized . for each position , the tidal 
 volume was measured during breathing at rest using a hot - wire flow meter ( ae300-s , minato 
 medical science , tokyo , japan ) and then synchronized with the chest - wall motion for input 
 into the analysis software . to avoid measuring motion not associated with breathing , all 
 patients were instructed not to alter their posture during measurements . the coordinate data 
 of each marker were entered into the analysis software ( evart5.04 , motion analysis 
 corporation ) at a sampling frequency of 100  hz . thereafter , the breaths in the last 20  s of 
 each measurement were extracted for analysis , and then , the chest - wall configuration and 
 breathing motion were analyzed . in accordance with the method of vellody et al.10 , chest - wall configuration analysis 
 involved calculation of the anteroposterior diameters of the rcp , anteroposterior diameters 
 of the rca , and anteroposterior and mediolateral diameters of the ab at the end - expiratory 
 lung volume ( eelv ) of breathing at rest in the positions shown in fig . 1.representation of the chest wall using external markers : model used to calculate the 
 anteroposterior ( a ) , mediolateral ( b ) , and craniocaudal diameters ( c ) . furthermore , on the basis of the coordinate values obtained by oep , we created a 
 horizontal cross - sectional view of the chest wall in the same position as fig . 1 using the image - processing software gnuplot 4.4 
 ( http://www.gnuplot.info/ ) , and visually compared the configurations . representation of the chest wall using external markers : model used to calculate the 
 anteroposterior ( a ) , mediolateral ( b ) , and craniocaudal diameters ( c ) . rcp : pulmonary rib cage , rca : abdominal ribcage , ab : abdomen chest - wall motion analysis involved calculating the coordinate variation associated with 
 breathing in the craniocaudal , mediolateral , and anteroposterior directions for each 
 reflective marker . coordinate variations in each direction were included if the chest wall 
 could be measured in all positions , and the mean value was calculated according to the 
 following five sites : anterior rcp ( 14 markers ; a - rcp ) , anterior rca ( 6 markers ; a - rca ) , 
 left rca ( 6 markers ; l - rca ) , anterior ab ( 12 markers ; a - ab ) , and left ab ( 6 markers ; l - ab ) 
 ( fig . 2fig . 2.division of the chest wall into compartments and placement of passive reflective 
 markers on the chest wall : rcp : pulmonary rib cage , rca : abdominal rib cage , ab : 
 abdomen . the chest wall was divided into 5 parts : anterior - rcp ( 14-markers ) , anterior - rca 
 ( 6-markers ) , left side - rca ( 6-markers ) , anterior - ab ( 12-markers ) , and left side - ab 
 ( 6-markers ) ) . using the image - processing software gnuplot 4.4 ( http://www.gnyplot.info/ ) , we 
 created a three - dimensional model of the chest wall in each position for all patients and 
 represented chest - wall motion during breathing at rest as a vector . chest - wall 
 configurations and vectors were visually examined in the horizontal and sagittal planes . division of the chest wall into compartments and placement of passive reflective 
 markers on the chest wall : rcp : pulmonary rib cage , rca : abdominal rib cage , ab : 
 abdomen . the chest wall was divided into 5 parts : anterior - rcp ( 14-markers ) , anterior - rca 
 ( 6-markers ) , left side - rca ( 6-markers ) , anterior - ab ( 12-markers ) , and left side - ab 
 ( 6-markers ) data are shown as means  standard deviations . study data included tidal volume , changes in 
 chest - wall diameter , and mean coordinate variation , which were examined using one - way anova 
 in order to determine how they were affected by posture , and in the event that a significant 
 difference was observed , a post - hoc test was performed using the bonferroni method . all 
 statistical tests were performed using spss version 20.0 for windows ( spss inc . , chicago , 
 il , usa ) , and a p - value of < 0.05 was considered significant . the tidal volumes in the supine , lateral recumbent , and sitting positions were 0.52  0.15 , 
 0.51  0.12 , and 0.56  0.20 l , respectively , and there was no effect of posture on tidal 
 volume . table 2table 2.chest-wall diameter changes during tidal breathing in three postures ( eelv ) 
 [ mm]supinelateralsittingrcpantero - posterior168.8  11.2206.0  15.3 * 201.0  13.0 * rcaantero - posterior192.6  21.9237.8  23.1 * 223.7  22.9 * medio - lateral325.1  13.5 + 282.8  14.3 * 323.5  14.6 + abantero - posterior181.1  20.4225.4  28.9 * 271.5  19.4 * + medio - lateral310.6  22.4271.5  19.4 * 312.0 p<0.01 vs. supine + p<0.01 vs. lateral shows that the anteroposterior diameters of the rcp and rca were significantly 
 lower in the supine position than in the sitting and lateral recumbent positions 
 ( p<0.001 ) in eelv , whereas the mediolateral diameter of the rca was significantly lower 
 in the lateral recumbent position than in the supine and sitting positions ( p<0.001 ) . the 
 ab anteroposterior diameters significantly increased in the following order : supine 
 position , lateral recumbent position , and sitting position ( p<0.001 ) . the mediolateral 
 diameter was significantly lower in the lateral recumbent position than in the supine and 
 sitting positions ( p<0.001 ) . * p<0.01 vs. supine + p<0.01 vs. lateral next , the horizontal configurations of the rcp , rca , and ab were visually compared ( fig . 3fig . 3.computed models of chest - wall configuration ( horizontal plane ) for all subjects ( a : 
 anterior , p : posterior , r : right , l : left ) . left fig . : supine position , center fig . : right lateral position , right fig . : sitting 
 position . the black dots represent markers and the center line of the chest wall divides the 
 chest into right and left . ) . in the front of the chest wall in the supine position , the mediolateral diameters , 
 in contrast to the anteroposterior diameters , presented larger elliptical shapes for the 
 rcp , rca , and ab , whereas the dorsal side showed a mediolateral symmetrical shape in contact 
 with the floor surface . in the lateral recumbent position , the anteroposterior diameters of 
 the rcp , rca , and ab increased , and the anteroposterior diameters and mediolateral diameters 
 presented approximately equal shapes . furthermore , a decrease in the mediolateral diameter 
 of the right side , i.e. , the weight - bearing side , was observed in the rca and ab , presenting 
 an asymmetrical shape with respect to the left side . moreover , we found that the midline of 
 the sternal angle and xiphoid process was rotated to the left relative to the umbilicus . the 
 chest wall does not come into contact with the surface of the floor in the sitting position , 
 and therefore , a rounded elliptical shape was presented on both the anterior and posterior 
 sides , and , as with the supine position , the mediolateral diameters showed a large 
 symmetrical shape . computed models of chest - wall configuration ( horizontal plane ) for all subjects ( a : 
 anterior , p : posterior , r : right , l : left ) . : supine position , center fig . : right lateral position , right fig . : sitting 
 position . the black dots represent markers and the center line of the chest wall divides the 
 chest into right and left . regarding motion of the anterior rcp , craniocaudal motion was significantly greater in the 
 sitting position than that in the lateral recumbent and supine positions ( p<0.01 and 
 p<0.05 , respectively ) ( table 3table 3.mean chest - wall coordinates during tidal breathing in three postures [ mm]supinelateralsitting a - rcpcranio - caudal1.14  0.680.68  0.341.94  1.07*++medio - lateral0.03  0.190.29  0.290.34  0.53++antero - posterior0.69  0.730.64  0.811.91  1.37**++ a - rcacranio - caudal1.69  0.611.03  0.372.58  1.26*++medio - lateral0.11  0.230.29  0.390.26  0.78 + antero - posterior1.50  0.730.94  0.532.81  1.14**++   l - rcacranio - caudal1.08  0.450.95  0.402.19  0.94**++ medio - lateral0.41  0.441.70  0.58 * * 0.96  0.85 + antero - posterior1.48  0.521.65  0.882.11  1.09 a - abcranio - caudal0.73  0.600.54  0.730.93  0.93medio - lateral0.15  0.230.54  0.68 * 0.32  1.04++antero - posterior5.55  1.835.23  1.664.79  2.60 0.37*++ medio - lateral0.77  0.401.17  0.500.55  0.61++ antero - posterior1.45  0.421.25  0.631.59  0.73a : anterior , l : left , craniocaudal : coordinate of vertical axis , mediolateral : 
 coordinate of the forehead axis , anteroposterior : coordinate of the sagittal axis . the 
 coordinate change to the upper left in the locus in front was defined as 
 plus.expressed as means  sd * p<0.05 , * * p<0.01 vs. supine + p<0.05 , 
 + + p<0.01 vs. lateral , fig . 4.computed models of the chest wall and mean tidal vectors for all subjects ( a : 
 anterior , p : posterior , r : right , l : left ) . left fig . medio - lateral motion showed a significant change in the sitting position compared 
 with that in the lateral recumbent position ( p<0.01 ) , and anteroposterior motion was 
 significantly greater in the sitting position than that in the supine and lateral recumbent 
 positions ( p<0.01 ) . a : anterior , l : left , craniocaudal : coordinate of vertical axis , mediolateral : 
 coordinate of the forehead axis , anteroposterior : coordinate of the sagittal axis . the 
 coordinate change to the upper left in the locus in front was defined as 
 plus.expressed as means  sd * p<0.05 , * * p<0.01 vs. supine + p<0.05 , 
 + + p<0.01 vs. lateral computed models of the chest wall and mean tidal vectors for all subjects ( a : 
 anterior , p : posterior , r : right , l : left ) . 4 ) , the rcp vector was shown to be large in the upper anterior area , and , 
 therefore , compared with that in the supine and lateral recumbent positions , in the rcp of 
 the sitting position , chest - wall motion occurred in the upper anterior area . regarding motion on the anterior side of the rca , craniocaudal motion was significantly 
 greater in the sitting position than in the lateral recumbent and supine positions 
 ( p<0.01 and p<0.05 , respectively ) . similarly , anteroposterior motion was significantly 
 greater in the sitting position than in the lateral recumbent and supine positions 
 ( p<0.01 ) . however , mediolateral motion showed a significant change in the lateral 
 recumbent position compared to the sitting position ( p<0.05 ) . regarding rca motion on the left side , i.e. , the non - weight - bearing side , craniocaudal 
 motion was significantly greater in the sitting position than in the supine and the lateral 
 recumbent positions ( p<0.01 ) , whereas mediolateral motion was significantly greater in 
 the lateral recumbent position than in the supine and the sitting positions ( p<0.01 and 
 p<0.05 , respectively ) ; however , no significant differences were observed between postures 
 with respect to anteroposterior motion . as with the rcp , in the sitting sagittal plane ( fig . 
 4 ) , however , for the left side 
 in the horizontal plane in the lateral recumbent position , we observed motion toward the 
 left lateral side , and we confirmed a trend different from that of chest - wall motion 
 direction at the same site in the sitting position . regarding motion on the anterior of the ab , in the craniocaudal and anteroposterior 
 directions , no significant differences were observed between the postures , whereas for 
 mediolateral motion , significant changes were observed in the lateral recumbent position 
 compared to the supine ( p<0.05 ) and sitting positions ( p<0.01 ) . regarding motion on the left lateral side , i.e. , the non - weight - bearing side of the ab , 
 there was significantly less craniocaudal motion in the lateral recumbent position compared 
 to the supine position ( p<0.05 ) . furthermore , craniocaudal motion in the sitting position 
 was significantly greater in the sitting position than that in the supine and lateral 
 recumbent positions ( p<0.05 and p<0.01 , respectively ) . mediolateral motion was 
 significantly greater in the lateral recumbent position than in the sitting position 
 ( p<0.01 ) . as with rca , there was no difference in anteroposterior motion between 
 postures . in the sagittal plane shown in fig . 4 , anterior 
 chest - wall motion was confirmed in all postures , and there was no difference observed 
 between postures . however , in the horizontal plane , a mediolateral symmetrical vector was 
 shown in the supine and sitting positions , whereas in the lateral recumbent position , the 
 vector for the right side , i.e. , the weight - bearing side , was more asymmetrical than the 
 vector for the left side . in the present study , we examined the effects of posture on the configuration and motion of 
 the chest wall in healthy men . regarding configuration , the anteroposterior diameters of the 
 rcp and rca were smallest in the supine position , the mediolateral diameter of the rca was 
 smallest in the lateral recumbent position , and the chest wall tended to decrease in the 
 direction of the force of gravity . furthermore , our analysis of chest - wall motion during 
 breathing at rest revealed that craniocaudal and anteroposterior motions of the rcp and rca 
 were characteristically greatest in the sitting position and that mediolateral motion was 
 greatest in the lateral recumbent position . to date , several reports have examined the effect of posture on chest - wall motion . vellody 
 et al.10 examined the configuration and 
 motion of the chest wall in the supine , lateral recumbent , and sitting positions using 
 magnetometry . they reported that in the direction of gravity , chest - wall configuration 
 reduced in size and that breathing motion was predominantly abdominal in the supine position 
 compared to the sitting position . furthermore , verschakelen et al.11 examined changes in the chest - wall diameter in the supine , 
 sitting , and standing positions using respiratory inductance plethysmography ( rip ) and 
 reported that breathing motion at rest tended to be predominantly abdominal in the supine 
 position compared to the standing position . however , both the magnetometry and rip devices 
 in these studies are characteristically incapable of examining chest - wall motion . similar to 
 our study , de groote a used oep to examine the direction and magnitude of breathing motion 
 at localized sites of the chest wall . their results revealed that for the rib cage , 
 breathing motion was greater in the craniocaudal and anteroposterior directions , whereas for 
 the ab , breathing motion was mainly in an anteroposterior direction . however , the number of 
 reflective markers used in their study was 36 and the measurement position was limited to 
 the sitting position6 . in our study , regarding eelv , the anteroposterior diameters of the rcp , rca , and ab were 
 smallest in the supine position . the mediolateral diameters of the rca and ab were small in 
 the lateral recumbent position , and the anteroposterior diameter of the ab was largest in 
 the sitting position . although the measurement method differed , our results were comparable 
 to those reported by vellody et al.10 , 
 probably because , despite using oep , when calculating coordinate values of the chest - wall 
 diameter , we calculated the distance between two typical markers . however , in the present study , we were able to obtain the characteristics of chest - wall 
 configuration as shown in fig . we found that the anteroposterior diameters were smallest in the supine position 
 with a mediolateral symmetrical and elliptical shape , whereas in the lateral recumbent 
 position , the anteroposterior diameters were large with small mediolateral diameters and 
 round shapes , indicating that the mediolateral chest - wall configuration was asymmetrical . 
 regarding the changes in configuration observed here , it is believed that changing to the 
 lateral recumbent position may have caused the mediastinum to shift in a sagittal plane 
 direction6 , 12 . on the basis of the results of the ab diameter and horizontal 
 plane configuration , it is believed that changes in the direction of the force of gravity 
 along with changes in posture cause a shift in the abdominal organs , which may expand the 
 abdominal wall and change the configuration14 . the most significant finding of the present study is that local chest - wall motion 
 associated with breathing is affected by posture . to date , it has been said that the local 
 breathing motion of the chest wall in the sitting position tends to be in a craniocaudal and 
 anteroposterior direction for the rib cage6 . however , the present study revealed that in postures , including the supine and lateral 
 recumbent positions , such breathing motion was reduced . furthermore , similar to de groote et 
 al.6 , regarding the sitting position , we 
 found that mediolateral motion of the rib cage was much less , whereas in the lateral 
 recumbent position , mediolateral motion was more , and , in particular , mediolateral motion of 
 the non - weight - bearing side of the abdominal rib cage was greatest in the lateral recumbent 
 position ( 1.704  0.578  mm ) . previously , in the lateral recumbent position , the change in 
 chest - wall volume associated with breathing was found to be characteristically greater for 
 the abdominal rib cage of the non - weight - bearing side12 , supporting our results in the present study . although the effect 
 of posture on these rib cage breathing motions can not be clarified by the results of the 
 present study alone , we believe that the mediolateral asymmetry of the chest wall in the 
 lateral recumbent position may have been caused by local pressure on the chest wall due to 
 the floor surface12 , in addition to 
 factors indicated by vellody et al.10 , 
 which include 1 ) difference in respiratory muscle action distribution , 2 ) change in the 
 mechanical advantage of the inspiratory muscles , and 3 ) change in local compliance . 
 furthermore , on the basis of our result indicating that the midline rotated to the left at 
 the level of the sternal angle and xiphoid process in the lateral recumbent position ( fig . 4 ) , it is believed that the angle made by the 
 ribs and vertebral body affects rib motion5 , 6 and that changes in the costovertebral joint 
 angle associated with changes in posture possibly caused the mediolateral diameters to 
 change . breathing motion of the ab has been found to be characteristically greater in the supine 
 position than in the sitting and standing positions11 . furthermore , de groote6 reported that abdominal motion in the sitting position was mainly in 
 an anteroposterior direction . however , our results demonstrated that abdominal motion was 
 not affected by posture , and , in all postures , the motion was greater in the anteroposterior 
 direction . as mentioned by konno et al.15 , this could be attributed to the effect of differences in compliance 
 between the ab , which consists of soft tissue , and the chest , which is supported by osseous 
 structures such as the sternum and ribs . furthermore , on comparing local motion of the ab , 
 in the present study , we observed no site at which motion was greatest in the supine 
 position . therefore , differences in our study compared to results of earlier studies could 
 have been caused by differences in the measurement methods . although only part of the chest 
 wall can be measured using conventional methods ( magnetometry and rip ) , with our method , we 
 were able to measure the entire chest wall , and we believe that this explains why we found 
 no such differences in the present study . chest - wall motion tends to vary in patients after surgery , and in patients with severe 
 chronic obstructive pulmonary disease13 , 16 , it is quite difficult to measure 
 chest - wall volume in clinical practice . in such instances , we believe that our results could be used as a 
 healthy reference , and , in particular , understanding which sites move the most according to 
 posture ( craniocaudal and anteroposterior direction of the rib cage in the sitting position , 
 and mediolateral motion of the non - weight - bearing side of the abdominal rib cage in the 
 lateral recumbent position ) will help detect abnormalities in breathing motion at each 
 site . chest - wall motion 
 differs between men and women11 , 14 , 17 , and , therefore , the results of the present study can not be applied 
 to women . furthermore , in the present study , measurements were recorded with subjects on the 
 floor in order to avoid the possibility of the chest wall sinking into the mattress if a bed 
 had been used . therefore , our results can not necessarily be applied to patients who are 
 bedridden . in the present study , we examined the effect of posture on chest - wall configuration and 
 breathing motion at various sites in healthy men . the results revealed that the anteroposterior diameters of the rcp and rca were smallest in 
 the supine position , the mediolateral diameter of the rca was smallest in the lateral 
 recumbent position , and the chest wall tended to decrease in the direction of gravitational 
 force . regarding breathing motion , in the supine and lateral recumbent positions , the motion of 
 the rib cage decreased in the craniocaudal and anteroposterior directions , and in the 
 lateral recumbent position , mediolateral motion in particular was greater . therefore , the chest - wall 
 configuration and local motion were affected by posture and the effects were particularly 
 notable in the rib cage .
[ purpose ] the purpose of this study was to clarify the impact of postural changes during 
 tidal breathing on the configuration and motion of chest - wall in order to further 
 breathing motion evaluation . 
 [ subjects and methods ] chest - wall configuration 
 and motion in the supine , right lateral , and sitting positions were measured using 
 optoelectronic plethysmography in 15 healthy adult men . 
 [ results ] the anteroposterior 
 diameters of the chest wall were significantly lower in the supine position for the 
 pulmonary and abdominal rib cages , whereas the mediolateral diameters in the lateral 
 position were lowest for the abdominal rib cage . regarding chest - wall motion , both 
 craniocaudal and anteroposterior motions of the anterior surface of the pulmonary and 
 abdominal rib cages were significantly greater in the sitting position . regarding motion 
 of the left lateral abdominal rib cage , lateral motion was greatest in the lateral 
 position . [ conclusion ] chest - wall configuration and motion changed according to posture in 
 healthy men , particularly in the pulmonary and abdominal rib cages .