Pediatric Pulmonology 12:227-232 (1992)
Effect of Posture on Regional Ventilation in Children H. Davies, MD, P. Helms, MD,
PhD,
and 1. Gordon, FRCR
SUMMARY. Little information has been published concerning the pattern of regional ventilation in children, yet many differences in lung and chest wall mechanics in childhood, supported by clinical observation, have led to the hypothesis that the pattern of regional ventilation seen in children may not be the same as in adults. Forty-threechildren and 16 adult volunteers underwent Krypton (Kr) 81m radionuclide ventilation lung scans in the supine and right and left decubitus postures. In children aged 2-1 0 years mean fractional ventilation to the right lung (VfR) was 46.1Yo.This fell to 36% when dependent and rose to 56.1% in the uppermost position. Redistribution of ventilation away from the dependent towards the uppermost lung was seen in all children. In children aged 10-18 years VfR was 57.2% (supine), 48.0% (dependent), and 62.9% (uppermost). An identicalpatternwas seen in children with normalor abnormal pulmonary functiontests (peak expiratory flow rate, and FEV,: FVC ratio). In subjects over 18 years of age a different pattern was seen: mean VfR was 52.4% (supine), rising to 53.4% (dependent), and falling to 48.9% (uppermost). Postural redistributionof ventilation, as assessed by Kr81m ventilation imaging, changes late in the second decade of life. This will have clinical consequences in the management of children o 1992 wiley-Liss, Inc. with unilateral lung disease. Pediatr Pulmonol. 1992; 12:227-232. Key words: Krypton 81m ventllation lung scan; dependent vs. uppermost lung; flow rates; effects of age, sex.
INTRODUCTION
MATERIALS AND METHODS
The distribution of ventilation and perfusion in the adult human lung has been extensively studied. Bronchospirometric lP3 and radioactive gas methodsk7 have consistently shown that both ventilation and perfusion are preferentially distributed to dependent lung regions during tidal breathing and that this pattern is seen regardless of posture. Remolina et al. have demonstrated that the preferential distribution of ventilation to dependent lung regions is clinically important in managing adults with unilateral lung disease.8 There is little published information concerning the pattern in children, yet there are many differences in lung and chest wall mechanics in childhood, which, along with clinical observation, have led to the hypothesis that the pattern of regional ventilation seen in adults may not be seen in ~ h i l d r e n . ” ~As with adults, this pattern may have important therapeutic implications for the care of sick infants with unilateral lung disease. If regional ventilation were distributed differently in children and adults, it would be crucially important to determine when children adopt the adult pattern of regional ventilation. To elucidate this changing pattern, the effect of posture on regional ventilation was investigated in older children.
Forty-three children, 22 boys and 21 girls, mean age 10.5 years (range, 2.0-16.9), undergoing Krypton (Kr) 8 1 m scans as part of clinical investigation were studied along with 17 volunteers, 8 men and 9 women, mean age 30.7 years (range, 18.9-50.2). Subjects lay supine on a reinforced gamma camera, set with a window of 190 KEV (? 10%) and were asked to breathe from a continuous supply of an air/Krypton 8 1 m mixture. When background activity had been reduced to a minimum, using an electric fan to blow expired gas away from the camera face, a 200 kilocount steady state image was acquired. Similar images were also acquired with the subject lying on the left and right side. For these images the gamma camera was rotated through 90” and the subject asked to realign against the vertical camera face. All children had a contemporaneous chest radiograph. The subjects had been divided into three age-related groups: Group A, 2-10 years; Group B, 11-18 years;
0 1992 Wiley-Liss, Inc.
Received October 30, 1991; (revision) accepted for publication December 20, 1991. Address correspondence and reprint requests to Dr. H. Davies, Department of Paediatrics, Central Middlesex Hospital, Acton Lane, London NWIO. England.
228
Davies et al.
1
2
Fig. 1. Fractional ventilation to right lung (%) when supine, dependent, and uppermost. Vertical lines represent one standard deviation. Children aged 2-10 years. SubG 1 (left panel), normal chest radiograph (n = 9); SubG 2 (right panel), bilateral radiographic abnormalities (n = 5).
Group C, 18 years and above. These age ranges were chosen because work by Mansell et al. has suggested that changes in airway closure during tidal breathing occur toward the end of the first decade of life. ' Groups A and B were further subdivided on the basis of the interpretation of their chest radiographs by a radiologist unaware of the radionuclide scans: Sub-G 1, normal chest radiograph; Sub-G 2, bilateral radiographic abnormalities; Sub-G 3, unilateral radiographic abnormalities.
'
Image Analysis
Quantification of the steady state image was accomplished using interactive computer programs. Images were stored in computer as 64 by 64 matrices and displayed on the TV monitor in 256 by 256. With the aid of a region of interest program, areas corresponding to the two lungs were defined. Within these regions Kr8Im activity was used to calculate fractional ventilation to the right lung (VfR), defined as: VfR=
activity over R lung x 100%. activity over R lung +activity over L lung
Differences between VfR in the three postures were tested for significance with the paired Student's t test. Standard spirometric pulmonary function tests (PFT) were performed on all subjects old enough to cooperate. Forced expiratory volume in one second (FEV,), forced vital capacity (FVC), and peak expiratory flow rate (PEFR) were recorded. Results of these tests were expressed as an FEV :FVC ratio or, in the case of PEFR, as
percent predicted by height. l6 Subjects were divided according to the results: Normal PFT, FEV,:FVC> 80%; FVC and PEFR > 80% predicted; abnormal PFT, FEV,:FVC or PEFR C 80% predicted. RESULTS Group A: Children Aged 2-10 Years MeanVfR(supine) was46.1% (+ 12.6SD). When the lungs were dependent, VfR fell to 36.0% (2 12.8) and when uppermost it rose to 56.1% (+ 9.9) (Fig. 1). Both changes were significant (P < 0.001). The difference between VfR (dependent) and VfR (uppermost) was also highly significant (P < 0.001). Redistribution of ventilation away from the dependent toward the uppermost lung was seen in all children. Only two chest radiographs were categorized as showing bilateral abnormalities (Sub-G 2), but there was no difference in this pattern of regional ventilation in Sub-G 1 and 3. Group B: Children Aged 11-18 Years
Mean VfR (supine) was 57.2% ( 2 7.3). When the lungs were dependent, VfR fell to 48.0% ( 2 8.2) and when uppermost it rose to 62.9% ( 5 7.9) (Fig. 2) Both changes were significant (P < 0.0005). The difference between VfR (supine) and VfR (uppermost) was also highly significant (P < 0.0005). Four children showed the adult or mixed pattern of regional ventilation. One child demonstrated the adult pattern in both right and left decubitus postures, while three others only had this pattern in the left decubitus posture. Again, only two chest radiographs were categorized as showing bilateral abnor-
Changing Regional Ventilation in Children and Adults TABLE 1-Fractional Ventilation to the Right Lung Initials
Age
(years)
X-ray
Children 2- 10 years AK 4.3 3 1 4.4 PC EH 1 4.6 1 JM 5.4 ID 1 5.8 JG 2 6.0 2 6.5 DJ u 1 7.7 3 PS 8.1 1 8.1 TJ 8.4 NC BS 1 8.4 JA 9.1 JB 3 9.2 1 KT 9.5 SN 3 9.6 KD 1 9.8 AK 3 9.9 3 JA 10.3 1 10.3 EW 3 11.1 RG 1 AH 11.9 3 12.6 JC I 12.8 CB 1 TW 12.9 3 13.4 RL SM 3 13.5 3 13.5 DH 3 SD 13.7 TF 2 14.7 IH 1 14.7 I JM 15.0 3 DH 15.1 AH 3 15.1 SE 3 15.6 2 16.1 PC 1 JB 16.1 3 ww 16.5 3 AP 16.9 PW 18.9 GB 19.7 GR 20.6 LS 24.4 RB 24.9 JB 25.1 RR 26.0 AD 26.6 AG 30.2 RK 31.1 HD 32.9 JF 33.8 MD 34.1 JS 35.8 UN 38.6 MP 39.1 KE 50.2
Supine
Posture Dependent
52.0 53.0 52.0 37.0 56.0 14.0 23.0 51.0 52.0 55.0 61.5 50.0 56.0 32.0 38.0 51.0 53.0 44.0 58.0 56.0 53.0 56.0 50.0 53.0 58.0 48.0 68.0 53.0 78.0 55.0 55.0 60.0 47.0 54.0 54.0 65.0 55.0 59.0 66.0 52.0 51.0 5 1.0 55.0 52.0 54.0 55.0 50.0 53.0 52.0 52.0 50.0 58.0 53.0 54.0 52.0 52.0
33.0 47.0 34.0 35.0 37.0 5.0 9.0 42.0 32.0 40.0 52.2 43.0 51.0 23.0 36.0 45.0 46.0 37.0 44.0 46.0 45.0 48.0 42.0 51.0 41.0 31.0 49.0 42.0 70.0 43.0 55.0 46.0 45.0 44.0 42.0 62.0 56.0 51.2 53.0 48.0 51.0 55.0 48.0 49.0 56.0 55.0 59.0 51.0 63.0 55.0 45.0 58.0 47.0 56.0 58.0 53.0
Uppermost 60.0 60.0 60.0 45 .O 69.0 31.0 -
58.0 67.0 68.0 0.0 59.0 0.0 51.0 47.0 57.0 59.0 51.0 72.0 66.0 57.0 69.0 59.0 63.0 70.0 59.0 72.0 61.0 77.0 59.0 50.0 68.0 50.0 61.0 59.0 71.0 50.0 57.0 70.0 62.0 36.0 53.0 60.0 58.0 37.0 50.0 52.0 50.0 43.0 49.0 43.0 47.0 42.0 57.0 43.0 49.0
229
malities (Sub-G 2) but there was no difference in this pattern of regional ventilation in sub-groups 1 and 3. Group C: 18 Years and Above
A different pattern was observed in this group. Mean
VfR (supine) was 52.4% (+ 1.5). This rose when the lungs were dependent, to 53.4% (* 4.9) and when they were uppermost it fell to 48.9 ( 2 7.7) (Fig. 3).The change in ventilation from supine to uppermost and from dependent to uppermost reached significance although the change from supine to dependent did not. When the right lung was dependent, VfR rose in nine subjects and fell in six; in two it remained unchanged. When uppermost, VfR fell in 1 1 and rose in 6. In eight subjects VfR rose when dependent and fell when uppermost. The opposite was observed in 3 subjects while in the remaining six the pattern was mixed. Effect of Pulmonary Function on Distribution of Ventilation
PFTs were recorded in 31 children able to cooperate. Three of these were not included in the analysis because left decubitus ventilation images were not performed; their inclusion did not affect the analysis of redistribution of ventilation from the supine to right decubitus posture. Distribution of ventilation in all 3 1 children is shown in Figure 4; a similar pattern was seen regardless of PFT result. Changing Pattern of Regional Ventilation in Childhood Data from all age groups and those previously reportedI4 were amalgamated and, using a standard linear regression program, the relationship between age and postural changes in regional ventilation was studied. The data were also analyzed to identify any difference between males and females. Change in VfR from supine to dependent was expressed as:
VfR (dependent) -VfR (supine) VfR (supine)
x 100%.
In the uppermost position, change in ventilation to the right lung was similarly expressed:
VfR (uppermost) - VfR (supine) x 100%. VfR (supine) Fractional ventilation to the right lung rose when its position changed from supine to uppermost, in all but two children under 10 years of age; a mixed pattern was seen in the second decade but the majority (10 of 14 subiects over 20 years) demonstrated the reverse pattern (Fig. 5 ) . I
_
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DISCUSSION AGE 18+
Supine
Dependent
Uppermost
Fig. 3. Fractional ventilation to right lung (%) when supine, dependent, and uppermost. Vertical lines represent one standard deviation. Adult volunteers (18 years and over).
The uppermost lung was preferentially ventilated until the age of 20, when the distribution was reversed. Ventilation was redistributed in a similar fashion in the other decubitus position (Fig. 6). There was no demonstrable difference between males and females. The slopes for the regression line for the two sexes were very similar (0.94 compared with 1.04, for males and females, respectively).
Ethical considerations prevent ventilation imaging in normal children. This study confirms and extends the and Davies et demonstrating work of Heaf et that ventilation is preferentially distributed to the uppermost lung in infants and young children, regardless of the radiographic appearances of the lungs. Possible explanations have been presented previously. l4 When nursing critically ill infants and children with unilateral lung disease these differences should be considered if optimal blood gases are to be achieved. The data shown here from the study of older children and adult volunteers demonstrate that preferential distribution of ventilation toward uppermost lung regions continues beyond infancy and early childhood. All children studied between the age of 2 and 10 demonstrated the “infant” pattern in both the left and right decubitus posture and no effect of age was observed. Beyond this age there was a gradual change until the adult pattern was adopted late in the second decade (Fig 5 , 6 ) . These figures suggest, however, that the relationship between age and the distribution of regional ventilation in different postures may not be a simple linear one. The adult pattern only emerges beyond the age of 10 and although there is a wide scatter of results in the group of adult volunteers the transition is virtually complete by the age of 20. The change is independent of sex, appearance of chest radiographs, and pulmonary function. The resting intrapleural pressure is nearer atmospheric in children and, therefore, airway closure is more likely to occur in
Changing Regional Ventilation in Children and Adults 100r
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dependent lung regions. Ventilation will be redistributed toward uppermost regions, and in the decubitus posture the uppermost lung will ventilate more effectively. If this is indeed the mechanism, the “infant” pattern should continue up to the age at which airway closure no longer occurs during tidal breathing. Work by Mansell et al. ‘ I has demonstrated that this occurs at the age of 10, the same age at which we observed a trend toward the “adult” pattern of regional ventilation. Further support is provided by studies of capillary oxygen tension and its relationship with age. Mean oxygen tension rises to peak values in adole~cence’~ and this could be partly explained by the changing pattern of regional ventilation seen in childhood. While ventilation
is preferentially distributed to uppermost lung regions in childhood, the dependent lung regions remain better perfused. I 8 This will result in ventilation/perfusion mismatch and hence lower arterial oxygen tension. When the adult pattern is adopted, ventilation and perfusion will be distributed to the same (dependent) lung regions and arterial oxygen tension would thus be expected to improve. The work of Gaultier et a].” suggests that this occurs from the age of 10, again the age at which we observed a transition to the “adult” pattern of regional ventilation
a
:
Conclusions
1. The pattern of regional ventilation in children is different from that seen in adults. Redistribution of venti-
232
Davies et al.
lation away from the dependent lung and toward the uppermost was seen in all but 2 of 37 children under 10 years of age. A mixed pattern was seen in the second decade and by the age of 20 the adult pattern predominated. 2. Radiographic appearances and results of pulmonary function tests were not different in boys and girls. 3. The differences can be explained by the properties of the immature lung and chest wall. 4. When nursing critically ill patients and very young children with unilateral lung disease these differences should be considered if optimum gas exchange is to be achieved. REFERENCES 1. Svanberg L. Influence of posture on lung volumes, ventilation and
2. 3.
4.
5.
6.
circulation in the normal: A bronchometric, bronchospirometric investigation. Scand J Clin Lab Invest (suppl]. 1957; 25:l-195. Martin C. Young AC. Ventilation perfusion variation within the lung. J Appl Physiol. 1977; 11:371-376. Lillington GA, Fowler WS, Miller RD, Helmholtz Junior MF. Nitrogen clearance rates on right and left lung in different positions. J Clin Invest. 1953; 38:202&2034. West JB, Dollery CT. Distribution of blood flow and ventilation perfusion ratio in the lung, measured with radioactive CO,. J Appl Physiol. 1960; 15:405410. Ball WC, Stewart, PV. N e w s h m LGS, Bates DB. Regional pulmonary function studies with Xenon 133. J Clin Invest. 1962; 4 I :5 19-5 3 1 . Milic-Emili J, Henderson JAM, Dolovitch MB, Trop D, Kaneko K. Regional distribution of inspired ga.. in the lung. J Appl Physiol. 1966: 21:749-759.
7. Amis TC, Jones HA, Hughes JMB. Effect of posture on intemgional distribution of pulmonary perfusion and VA-Q ratios in man. Respir Physiol. 1984; 56: 169-182. 8. Remolina C, Khan AU, Santiago TV. Edelman NH. Positional hypoxaemia in unilateral lung disease. N Engl J Med. 1981; 304:523-525. 9. Agostini E. Volume pressure relationships of the thorax and lung in the newborn. J Appl Physiol. 1959; 14:909-113. 10. Avery ME, Cook CD. Volume pressure relationships of lung and thorax in foetal, newborn and adult goats. J Appl Physiol I961 ;l6: 1034-1038. 1 I . Mansell A, Bryan C, Levison H. Airway closure in children. J Appl Physiol. 1972; 33:711-714. 12. Agostini E, Mead J. Handbook on Physiology, Vol. I , Section 3. Bethesda: American Physiological Society, 1964:393-394. 13. Heaf D, Helms P, Gordon 1, Turner H. Postural effects of gas exchange in infants. N Engl J Med. 1983; 308:1505-1508. 14. Davies H, Kitchman R, Helms P, Gordon 1. Regional ventilation in infants and very young children: Reversal of adult pattern. N Engl J Med. 1985; 1626-1628. 15. Cohen RS, Smith DW, Stevenson DK,Moscovitz PS, BenjaminGraham C . Lateral decubitus posturc as therapy for pcrsistent focal pulmonary interstitial emphysema in neonates: A preliminary report. J Pediatr. 1984; 1 0 4 : 4 4 1 4 3 . 16. Polgar G , Promadhat V. Pulmonary Function Testing in Children: Techniques and Standards 1971. Philadelphia: WB Saunders & n.
,n7,
LU., 1 ’ 1 1 1 .
17. Gaultier C, B o d e M, Allaire Y, Clement A, Buvry A, Girard F. Determination of capillary oxygen tension in infants and children. Assessment of methodology and normal values during growth. Bull Eur Physiopathol Respir. 1978; 14287-297. 18. Bhuyan U, Peters AM, Gordon I, Davies H, Helms P. Effects of posture on the distribution of pulmonary ventilation and perfusion in children and adults. Thorax. 1989; 44:480484.
Effect of Posture on Regional Ventilation in Children H. Davies, MD, P. Helms, MD,
PhD,
and 1. Gordon, FRCR
SUMMARY. Little information has been published concerning the pattern of regional ventilation in children, yet many differences in lung and chest wall mechanics in childhood, supported by clinical observation, have led to the hypothesis that the pattern of regional ventilation seen in children may not be the same as in adults. Forty-threechildren and 16 adult volunteers underwent Krypton (Kr) 81m radionuclide ventilation lung scans in the supine and right and left decubitus postures. In children aged 2-1 0 years mean fractional ventilation to the right lung (VfR) was 46.1Yo.This fell to 36% when dependent and rose to 56.1% in the uppermost position. Redistribution of ventilation away from the dependent towards the uppermost lung was seen in all children. In children aged 10-18 years VfR was 57.2% (supine), 48.0% (dependent), and 62.9% (uppermost). An identicalpatternwas seen in children with normalor abnormal pulmonary functiontests (peak expiratory flow rate, and FEV,: FVC ratio). In subjects over 18 years of age a different pattern was seen: mean VfR was 52.4% (supine), rising to 53.4% (dependent), and falling to 48.9% (uppermost). Postural redistributionof ventilation, as assessed by Kr81m ventilation imaging, changes late in the second decade of life. This will have clinical consequences in the management of children o 1992 wiley-Liss, Inc. with unilateral lung disease. Pediatr Pulmonol. 1992; 12:227-232. Key words: Krypton 81m ventllation lung scan; dependent vs. uppermost lung; flow rates; effects of age, sex.
INTRODUCTION
MATERIALS AND METHODS
The distribution of ventilation and perfusion in the adult human lung has been extensively studied. Bronchospirometric lP3 and radioactive gas methodsk7 have consistently shown that both ventilation and perfusion are preferentially distributed to dependent lung regions during tidal breathing and that this pattern is seen regardless of posture. Remolina et al. have demonstrated that the preferential distribution of ventilation to dependent lung regions is clinically important in managing adults with unilateral lung disease.8 There is little published information concerning the pattern in children, yet there are many differences in lung and chest wall mechanics in childhood, which, along with clinical observation, have led to the hypothesis that the pattern of regional ventilation seen in adults may not be seen in ~ h i l d r e n . ” ~As with adults, this pattern may have important therapeutic implications for the care of sick infants with unilateral lung disease. If regional ventilation were distributed differently in children and adults, it would be crucially important to determine when children adopt the adult pattern of regional ventilation. To elucidate this changing pattern, the effect of posture on regional ventilation was investigated in older children.
Forty-three children, 22 boys and 21 girls, mean age 10.5 years (range, 2.0-16.9), undergoing Krypton (Kr) 8 1 m scans as part of clinical investigation were studied along with 17 volunteers, 8 men and 9 women, mean age 30.7 years (range, 18.9-50.2). Subjects lay supine on a reinforced gamma camera, set with a window of 190 KEV (? 10%) and were asked to breathe from a continuous supply of an air/Krypton 8 1 m mixture. When background activity had been reduced to a minimum, using an electric fan to blow expired gas away from the camera face, a 200 kilocount steady state image was acquired. Similar images were also acquired with the subject lying on the left and right side. For these images the gamma camera was rotated through 90” and the subject asked to realign against the vertical camera face. All children had a contemporaneous chest radiograph. The subjects had been divided into three age-related groups: Group A, 2-10 years; Group B, 11-18 years;
0 1992 Wiley-Liss, Inc.
Received October 30, 1991; (revision) accepted for publication December 20, 1991. Address correspondence and reprint requests to Dr. H. Davies, Department of Paediatrics, Central Middlesex Hospital, Acton Lane, London NWIO. England.
228
Davies et al.
1
2
Fig. 1. Fractional ventilation to right lung (%) when supine, dependent, and uppermost. Vertical lines represent one standard deviation. Children aged 2-10 years. SubG 1 (left panel), normal chest radiograph (n = 9); SubG 2 (right panel), bilateral radiographic abnormalities (n = 5).
Group C, 18 years and above. These age ranges were chosen because work by Mansell et al. has suggested that changes in airway closure during tidal breathing occur toward the end of the first decade of life. ' Groups A and B were further subdivided on the basis of the interpretation of their chest radiographs by a radiologist unaware of the radionuclide scans: Sub-G 1, normal chest radiograph; Sub-G 2, bilateral radiographic abnormalities; Sub-G 3, unilateral radiographic abnormalities.
'
Image Analysis
Quantification of the steady state image was accomplished using interactive computer programs. Images were stored in computer as 64 by 64 matrices and displayed on the TV monitor in 256 by 256. With the aid of a region of interest program, areas corresponding to the two lungs were defined. Within these regions Kr8Im activity was used to calculate fractional ventilation to the right lung (VfR), defined as: VfR=
activity over R lung x 100%. activity over R lung +activity over L lung
Differences between VfR in the three postures were tested for significance with the paired Student's t test. Standard spirometric pulmonary function tests (PFT) were performed on all subjects old enough to cooperate. Forced expiratory volume in one second (FEV,), forced vital capacity (FVC), and peak expiratory flow rate (PEFR) were recorded. Results of these tests were expressed as an FEV :FVC ratio or, in the case of PEFR, as
percent predicted by height. l6 Subjects were divided according to the results: Normal PFT, FEV,:FVC> 80%; FVC and PEFR > 80% predicted; abnormal PFT, FEV,:FVC or PEFR C 80% predicted. RESULTS Group A: Children Aged 2-10 Years MeanVfR(supine) was46.1% (+ 12.6SD). When the lungs were dependent, VfR fell to 36.0% (2 12.8) and when uppermost it rose to 56.1% (+ 9.9) (Fig. 1). Both changes were significant (P < 0.001). The difference between VfR (dependent) and VfR (uppermost) was also highly significant (P < 0.001). Redistribution of ventilation away from the dependent toward the uppermost lung was seen in all children. Only two chest radiographs were categorized as showing bilateral abnormalities (Sub-G 2), but there was no difference in this pattern of regional ventilation in Sub-G 1 and 3. Group B: Children Aged 11-18 Years
Mean VfR (supine) was 57.2% ( 2 7.3). When the lungs were dependent, VfR fell to 48.0% ( 2 8.2) and when uppermost it rose to 62.9% ( 5 7.9) (Fig. 2) Both changes were significant (P < 0.0005). The difference between VfR (supine) and VfR (uppermost) was also highly significant (P < 0.0005). Four children showed the adult or mixed pattern of regional ventilation. One child demonstrated the adult pattern in both right and left decubitus postures, while three others only had this pattern in the left decubitus posture. Again, only two chest radiographs were categorized as showing bilateral abnor-
Changing Regional Ventilation in Children and Adults TABLE 1-Fractional Ventilation to the Right Lung Initials
Age
(years)
X-ray
Children 2- 10 years AK 4.3 3 1 4.4 PC EH 1 4.6 1 JM 5.4 ID 1 5.8 JG 2 6.0 2 6.5 DJ u 1 7.7 3 PS 8.1 1 8.1 TJ 8.4 NC BS 1 8.4 JA 9.1 JB 3 9.2 1 KT 9.5 SN 3 9.6 KD 1 9.8 AK 3 9.9 3 JA 10.3 1 10.3 EW 3 11.1 RG 1 AH 11.9 3 12.6 JC I 12.8 CB 1 TW 12.9 3 13.4 RL SM 3 13.5 3 13.5 DH 3 SD 13.7 TF 2 14.7 IH 1 14.7 I JM 15.0 3 DH 15.1 AH 3 15.1 SE 3 15.6 2 16.1 PC 1 JB 16.1 3 ww 16.5 3 AP 16.9 PW 18.9 GB 19.7 GR 20.6 LS 24.4 RB 24.9 JB 25.1 RR 26.0 AD 26.6 AG 30.2 RK 31.1 HD 32.9 JF 33.8 MD 34.1 JS 35.8 UN 38.6 MP 39.1 KE 50.2
Supine
Posture Dependent
52.0 53.0 52.0 37.0 56.0 14.0 23.0 51.0 52.0 55.0 61.5 50.0 56.0 32.0 38.0 51.0 53.0 44.0 58.0 56.0 53.0 56.0 50.0 53.0 58.0 48.0 68.0 53.0 78.0 55.0 55.0 60.0 47.0 54.0 54.0 65.0 55.0 59.0 66.0 52.0 51.0 5 1.0 55.0 52.0 54.0 55.0 50.0 53.0 52.0 52.0 50.0 58.0 53.0 54.0 52.0 52.0
33.0 47.0 34.0 35.0 37.0 5.0 9.0 42.0 32.0 40.0 52.2 43.0 51.0 23.0 36.0 45.0 46.0 37.0 44.0 46.0 45.0 48.0 42.0 51.0 41.0 31.0 49.0 42.0 70.0 43.0 55.0 46.0 45.0 44.0 42.0 62.0 56.0 51.2 53.0 48.0 51.0 55.0 48.0 49.0 56.0 55.0 59.0 51.0 63.0 55.0 45.0 58.0 47.0 56.0 58.0 53.0
Uppermost 60.0 60.0 60.0 45 .O 69.0 31.0 -
58.0 67.0 68.0 0.0 59.0 0.0 51.0 47.0 57.0 59.0 51.0 72.0 66.0 57.0 69.0 59.0 63.0 70.0 59.0 72.0 61.0 77.0 59.0 50.0 68.0 50.0 61.0 59.0 71.0 50.0 57.0 70.0 62.0 36.0 53.0 60.0 58.0 37.0 50.0 52.0 50.0 43.0 49.0 43.0 47.0 42.0 57.0 43.0 49.0
229
malities (Sub-G 2) but there was no difference in this pattern of regional ventilation in sub-groups 1 and 3. Group C: 18 Years and Above
A different pattern was observed in this group. Mean
VfR (supine) was 52.4% (+ 1.5). This rose when the lungs were dependent, to 53.4% (* 4.9) and when they were uppermost it fell to 48.9 ( 2 7.7) (Fig. 3).The change in ventilation from supine to uppermost and from dependent to uppermost reached significance although the change from supine to dependent did not. When the right lung was dependent, VfR rose in nine subjects and fell in six; in two it remained unchanged. When uppermost, VfR fell in 1 1 and rose in 6. In eight subjects VfR rose when dependent and fell when uppermost. The opposite was observed in 3 subjects while in the remaining six the pattern was mixed. Effect of Pulmonary Function on Distribution of Ventilation
PFTs were recorded in 31 children able to cooperate. Three of these were not included in the analysis because left decubitus ventilation images were not performed; their inclusion did not affect the analysis of redistribution of ventilation from the supine to right decubitus posture. Distribution of ventilation in all 3 1 children is shown in Figure 4; a similar pattern was seen regardless of PFT result. Changing Pattern of Regional Ventilation in Childhood Data from all age groups and those previously reportedI4 were amalgamated and, using a standard linear regression program, the relationship between age and postural changes in regional ventilation was studied. The data were also analyzed to identify any difference between males and females. Change in VfR from supine to dependent was expressed as:
VfR (dependent) -VfR (supine) VfR (supine)
x 100%.
In the uppermost position, change in ventilation to the right lung was similarly expressed:
VfR (uppermost) - VfR (supine) x 100%. VfR (supine) Fractional ventilation to the right lung rose when its position changed from supine to uppermost, in all but two children under 10 years of age; a mixed pattern was seen in the second decade but the majority (10 of 14 subiects over 20 years) demonstrated the reverse pattern (Fig. 5 ) . I
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DISCUSSION AGE 18+
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The uppermost lung was preferentially ventilated until the age of 20, when the distribution was reversed. Ventilation was redistributed in a similar fashion in the other decubitus position (Fig. 6). There was no demonstrable difference between males and females. The slopes for the regression line for the two sexes were very similar (0.94 compared with 1.04, for males and females, respectively).
Ethical considerations prevent ventilation imaging in normal children. This study confirms and extends the and Davies et demonstrating work of Heaf et that ventilation is preferentially distributed to the uppermost lung in infants and young children, regardless of the radiographic appearances of the lungs. Possible explanations have been presented previously. l4 When nursing critically ill infants and children with unilateral lung disease these differences should be considered if optimal blood gases are to be achieved. The data shown here from the study of older children and adult volunteers demonstrate that preferential distribution of ventilation toward uppermost lung regions continues beyond infancy and early childhood. All children studied between the age of 2 and 10 demonstrated the “infant” pattern in both the left and right decubitus posture and no effect of age was observed. Beyond this age there was a gradual change until the adult pattern was adopted late in the second decade (Fig 5 , 6 ) . These figures suggest, however, that the relationship between age and the distribution of regional ventilation in different postures may not be a simple linear one. The adult pattern only emerges beyond the age of 10 and although there is a wide scatter of results in the group of adult volunteers the transition is virtually complete by the age of 20. The change is independent of sex, appearance of chest radiographs, and pulmonary function. The resting intrapleural pressure is nearer atmospheric in children and, therefore, airway closure is more likely to occur in
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dependent lung regions. Ventilation will be redistributed toward uppermost regions, and in the decubitus posture the uppermost lung will ventilate more effectively. If this is indeed the mechanism, the “infant” pattern should continue up to the age at which airway closure no longer occurs during tidal breathing. Work by Mansell et al. ‘ I has demonstrated that this occurs at the age of 10, the same age at which we observed a trend toward the “adult” pattern of regional ventilation. Further support is provided by studies of capillary oxygen tension and its relationship with age. Mean oxygen tension rises to peak values in adole~cence’~ and this could be partly explained by the changing pattern of regional ventilation seen in childhood. While ventilation
is preferentially distributed to uppermost lung regions in childhood, the dependent lung regions remain better perfused. I 8 This will result in ventilation/perfusion mismatch and hence lower arterial oxygen tension. When the adult pattern is adopted, ventilation and perfusion will be distributed to the same (dependent) lung regions and arterial oxygen tension would thus be expected to improve. The work of Gaultier et a].” suggests that this occurs from the age of 10, again the age at which we observed a transition to the “adult” pattern of regional ventilation
a
:
Conclusions
1. The pattern of regional ventilation in children is different from that seen in adults. Redistribution of venti-
232
Davies et al.
lation away from the dependent lung and toward the uppermost was seen in all but 2 of 37 children under 10 years of age. A mixed pattern was seen in the second decade and by the age of 20 the adult pattern predominated. 2. Radiographic appearances and results of pulmonary function tests were not different in boys and girls. 3. The differences can be explained by the properties of the immature lung and chest wall. 4. When nursing critically ill patients and very young children with unilateral lung disease these differences should be considered if optimum gas exchange is to be achieved. REFERENCES 1. Svanberg L. Influence of posture on lung volumes, ventilation and
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circulation in the normal: A bronchometric, bronchospirometric investigation. Scand J Clin Lab Invest (suppl]. 1957; 25:l-195. Martin C. Young AC. Ventilation perfusion variation within the lung. J Appl Physiol. 1977; 11:371-376. Lillington GA, Fowler WS, Miller RD, Helmholtz Junior MF. Nitrogen clearance rates on right and left lung in different positions. J Clin Invest. 1953; 38:202&2034. West JB, Dollery CT. Distribution of blood flow and ventilation perfusion ratio in the lung, measured with radioactive CO,. J Appl Physiol. 1960; 15:405410. Ball WC, Stewart, PV. N e w s h m LGS, Bates DB. Regional pulmonary function studies with Xenon 133. J Clin Invest. 1962; 4 I :5 19-5 3 1 . Milic-Emili J, Henderson JAM, Dolovitch MB, Trop D, Kaneko K. Regional distribution of inspired ga.. in the lung. J Appl Physiol. 1966: 21:749-759.
7. Amis TC, Jones HA, Hughes JMB. Effect of posture on intemgional distribution of pulmonary perfusion and VA-Q ratios in man. Respir Physiol. 1984; 56: 169-182. 8. Remolina C, Khan AU, Santiago TV. Edelman NH. Positional hypoxaemia in unilateral lung disease. N Engl J Med. 1981; 304:523-525. 9. Agostini E. Volume pressure relationships of the thorax and lung in the newborn. J Appl Physiol. 1959; 14:909-113. 10. Avery ME, Cook CD. Volume pressure relationships of lung and thorax in foetal, newborn and adult goats. J Appl Physiol I961 ;l6: 1034-1038. 1 I . Mansell A, Bryan C, Levison H. Airway closure in children. J Appl Physiol. 1972; 33:711-714. 12. Agostini E, Mead J. Handbook on Physiology, Vol. I , Section 3. Bethesda: American Physiological Society, 1964:393-394. 13. Heaf D, Helms P, Gordon 1, Turner H. Postural effects of gas exchange in infants. N Engl J Med. 1983; 308:1505-1508. 14. Davies H, Kitchman R, Helms P, Gordon 1. Regional ventilation in infants and very young children: Reversal of adult pattern. N Engl J Med. 1985; 1626-1628. 15. Cohen RS, Smith DW, Stevenson DK,Moscovitz PS, BenjaminGraham C . Lateral decubitus posturc as therapy for pcrsistent focal pulmonary interstitial emphysema in neonates: A preliminary report. J Pediatr. 1984; 1 0 4 : 4 4 1 4 3 . 16. Polgar G , Promadhat V. Pulmonary Function Testing in Children: Techniques and Standards 1971. Philadelphia: WB Saunders & n.
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17. Gaultier C, B o d e M, Allaire Y, Clement A, Buvry A, Girard F. Determination of capillary oxygen tension in infants and children. Assessment of methodology and normal values during growth. Bull Eur Physiopathol Respir. 1978; 14287-297. 18. Bhuyan U, Peters AM, Gordon I, Davies H, Helms P. Effects of posture on the distribution of pulmonary ventilation and perfusion in children and adults. Thorax. 1989; 44:480484.
