ORIGINAL

Niger J Paed 2013; 40 (4): 406 –411

Oloyede IP

Ekrikpo UE

Ekanem EE

Normative values and

anthropometric determinants of

lung function indices in rural

Nigerian children: A pilot survey

DOI:http://dx.doi.org/10.4314/njp.v40i4,11

Accepted: 15th February 2013

Abstract Introduction: Respiratory

diseases represent some of the

most common causes of hospital

visits in childhood. Most of our

decision making rely on clinical

assessment without the benefit of

objective measures of pulmonary

function. The ability to measure

pulmonary function provides a tool

that can confirm clinical diagnosis,

monitor response to therapy and

follow progression of disease. Cor-

rect interpretation of pulmonary

function test requires an apprecia-

tion of normal values.

10.5+2.95 years while that of the

females was 10.7 + 3.19 years.

(

)

Oloyede IP

The mean PEFR, FVC and FEV

I

Department of Paediatrics,

Ekrikpo UE

Department of Medicine,

University of Uyo Teaching Hospital

PMB 1136, Uyo,

Akwa Ibom State, Nigeria.

E-mail: dreee11@yahoo.co.uk

Tel +2348022907609

were 3.95±1.55 litres per second

(l/s) 1.58±0.58 litres (l) and

1.57±0.56l in the males while for

the females 3.73±1.03l/s,

1.45±0.43l and 1.41±0.41l respec-

tively. The FVC and FEV1 of the

males were significantly higher

than that of the females (p=0.03

respectively). Height was the sig-

nificant predictor of PEFR

(p=0.04), while the height and

sitting height were the important

Ekanem EE

Department of Paediatrics,

University of Calabar Teaching

Hospital, Calabar Cross River State,

Nigeria.

Patients and methods: Lung

predictors of log FVC and FEV

1

function test was performed on

rural children in Akwa Ibom State,

Nigeria, to determine

normal values among healthy chil-

dren. One hundred and fifty two

children aged 6-16 years old com-

prising 89 males and 63

for the males respectively (p=

0.007 and 0.02; 0.004 and 0.027).

For the female subjects, age was a

significant predictor of log PEFR

and Log FVC (p=0.047 and

0.003), while Age and Sitting

height were the significant predic-

females were included in this

study. Anthropometric measure-

ments including height, weight,

sitting height, chest circumference

and body surface area were ob-

tained. The Peak Expiratory Flow

1

tors of log FEV (p=0.02 and 0.03

respectively).

Conclusion: The study has ob-

served higher lung function indices

in the males than in female chil-

dren. In addition to age and height,

sitting height has been observed as

an important predictor of the lung

function indices of the children

studied. This study should be seen

as a pilot study and will require

data from a large population to

establish normal values for our

population.

(

PEF), forced vital capacity (FVC)

and Forced Expiratory Volume in

one second (FEV ) were measured

1

using the spirolab III electronic

spirometer manufactured by Medi-

cal International Research (MIR)

Italy. It was a descriptive cross

sectional study.

Results: One hundred and fifty-five

children; 89 (58.6%) males and 63

Key words: Lung function, rural,

children, anthropometric determi-

nants

(

41.4%) females were studied. The

mean age (±SD) of the males was

Introduction

greatly influenced by individual weight, height, age, sex,

race, nu₂t_,r₃ition, body surface area and environmental

factors. . Objective measurements of pulmonary func-

tion can be useful in the diagnostic evaluation of chil-

dren who have a cough, exercise limitation, or other

symptoms and signs referable to the respiratory system.

Pulmonary function tests range from simple measure-

ments of peak flow and pulse oximetry to complex

evaluations of absolute lung volume and diffusing

1

capacity . Lung functions vary in healthy people and are

4

07

Correct interpretation of lung function test requires an

appreciation of normal values. Normal values for indi-

viduals of same age, gender, height and race are avail-

able from prediction fo₄ rmulae or reference tables for the

Caucasian population.

Spirometry machine, Spirolab III model no: 980067;

year of make: 2007, Italy. Each test was performed three

times with an interval of at least 30 seconds between

readings and the best of three readings was recorded.

The pulmonary₁f₆unction indices recorded included PEF,

1

FVC and FEV .

Reports on pulmonary function studies have been scanty

in Nigeria and mostly_-₉involve the estimation of peak

Data was analysed using STATA 10 (STATA Corp,

Texas, USA). The Student t-test was used in comparing

the means of continuous variables that were normally

distributed. The Spearman rho test was used to measure

the correlation of two continuous variables. Multivariate

linear regression was used to determine the independent

predictor of changes in the lung function indices of the

study population. The results were expressed as means

and standard deviations (SD). Data were summarized

into frequency tables and charts. The p-value<0.05 was

taken as statistically significant.

5

expiratory flow rate. Lung function measurements

made in Nigerian children are compared to Caucasian or

African-American children since there are few records

of spiro₈_,m₉ etric studies to determine a range of normal

values. However, this is unsatisfactory as reports have

shown children of African descen₁t₀_-t₁o₂ have lower values

than their Caucasian counterparts.

This is an attempt therefore to establish a range of nor-

mal values and anthropometric determinants of some

pulmonary function indices in healthy rural children

from the southern rain forest region of Nigeria.

Results

Subjects and methods

One hundred and fifty- two children were recruited for

the study. Eighty -nine (58.6%) of the subjects were

males and 63 (41.4%) were females giving a male:

female ratio of 1.4:1. The mean age of the males was

10.5±2.95 years, while that of the females was

10.7±3.19 years.

The subjects studied were normal healthy children with

ages ranging from six to sixteen years living in Oyubia

in Urue-Offong Oruko Local Government Area of Akwa

Ibom State, Nigeria. The children were recruited from

the only primary and secondary school in the commu-

nity. This was a descriptive cross sectional study. Ethi-

cal clearance was obtained from the University of Uyo

Teaching Hospital before embarking on the study. The

community leaders were informed on the details of the

study and written consent obtained Verbal consent was

also obtained from parents and older children.

Twelve (7.9%) of the subjects belonged to social class

II, and 140 (92.1%) belonged to social class III.

Table 1 shows the summary of the means of the meas-

ured variables. There was no statistically significant

difference in the age and anthropometric parameters of

rd

th

both genders. Height for age was within the 3 -97 per-

centile for 91.4% while, weight for age was within the

same percentile for 90.2% of the subjects, using the

Centre for Disease Control (CDC) growth chart.

The following criteria were required for acceptance as

normal subjects: (one) no history of cardiopulmonary

disease. (two) The ability to cooperate adequately during

the test, and (three) no physical evidence or history of

disease which might affect pulmonary function. A respi-

ratory questionnaire whose purpose was to identify any

child with a history of or current respiratory illness was

administered to the subjects. The socio-demographic

data of the children, evidence of current acute respira-

tory tract infection (cough, phlegm, wheeze, chest tight-

ness, nasal discharge, nasal congestion and fever), or

past history of chronic pulmonary diseases and other

illnesses that may limit activity were assessed using the

respiratory questionnaire. The parents’ socioeconomic

status wa₃s also assessed using the Olusanya et al classi-

The female subjects were heavier than the male subjects

at ages 11 (30.6±4.89kg vs 27.6±3.34kg); p=0.09 and 12

(36.5±9.06kg vs 28.5±5.38kg); p=0.04 and were taller at

ages 12 (143.9±5.25cm vs 137.2±6.28cm); p=0.03, 13

(153.3cm vs 146.6±5.12cm); p=0.04 and 14

(160.5±7.26cm vs 148.3± 9.32cm); p=0.20.

Table 1: Summary of the means of measured variables

Variables

Male (mean +

SD)

Female (mean

+ SD)

p-value

Age (years)

10.50 + 2.95

10.70 + 3.19

0.92

Weight (kg)

Height (cm)

Sitting height (cm)

Chest circumference (₂cm)

Body surface area (m )

29.60 ± 12.00

135.50±15.53

64.60± 8.95

80.80±6.24

1.00± 0.26

31.60± 11.91

137.80±14.32

66.30 ± 8.99

66.50±10.16

1.10± 0.25

0.78

0.86

0.59

0.51

0.71

1

fication. A general physical examination and a thor-

ough clinical examination of the cardiopulmonary sys-

tem were performed. This helped exclude any signifi-

cant cardiopulmonary disease that would affect lung

function. The subjects’ standing height, sitting height,

chest circumference and body weight were measured as

PEF (l/s)

FVC (l)

3.95±1.55

1.58±0.58

3.67±1.03

1.45±0.43

0.23

0.03**

1

4

FEV₁(l)

1.57±0.56

1.41±0.41

0.03**

per standard protocol, while the body surface a₁r₅ea was

**Significant p-values

calculated using the Dubois and Dubois formula.

Table 2 shows the pulmonary function parameters of the

subjects in relation to age and gender. The PEFR, FVC

and FEV of the males were significantly higher than

1

All the lung function tests were performed in standing

position using the Medical International Research (MIR)

4

08

Figure 1 and 2 shows the correlation of log PEFR, FVC

and FEV to sitting height in both the male and female

subjects. The lung function indices all increased with

increase in sitting height.

that of the females at ages 15 and 16. p= 0.01 and

.004, 0.04 and 0.001, 0.03 and 0.005 respectively. It

was also shown that the PEFR, FVC and FEV for ages

2 and 13 years were higher in the females but this did

not achieve statistical significance.

0

1

Table 2: Pulmonary function parameters of subjects in relation to age and gender

Age (yrs)

PEFR (L/S)

FEV

1

(L)

FVC (L)

M

F

p

M

F

p

M

F

p

6

7

8

9

1

2.36±0.61 2.26±0.55

2.71±0.60 2.65±0.60

3.10±0.62 2.91±0.66

3.60±0.39 3.51±0.43

3.48±0.55 3.63±0.77

3.75±0.72 3.76±0.96

0.73

0.96±0.12

1.14±0.24

1.23±0.15

1.19±0.11

1.36±0.20

1.47±0.18

0.89±0.19 0.42

0.99±0.01 0.21

1.11±0.17 0.19

1.15±0.08 0.46

1.23±0.13 0.15

1.38±0.24 0.28

0.98±0.15

1.17±0.25

1.26±0.27

1.23±0.11

1.40±0.06

1.56±0.20

0.90±0.19

1.01±0.12

1.12±0.16

1.18±0.08

1.28±0.11

1.42±0.23

0.36

0.20

0.17

0.43

0.18

0.12

0.80

0.61

0.71

0.62

0.98

0

1

2

3

4

5

3.34±0.81 4.31±1.04

3.89±0.71 4.36±0.11

5.26±1.28 4.81±0.19

6.58±1.03 4.96±0.58

0.06

0.35

0.66

0.01*

1.56±0.34

1.78±0.12

1.84±0.21

2.42±0.36

1.64±0.23 0.61

1.83±0.15 0.54

1.93±0.37 0.72

1.94±0.26 0.03*

1.64±0.37

1.82±0.14

1.88±0.20

2.46±0.39

1.67±0.25

1.85±0.14

1.94±0.35

2.00±0.05

0.84

0.60

0.77

0.04*

1

6

6.97±1.11 4.34±0.68

0.004* 2.96±0.48

1.92±0.24 0.005* 3.04±0.45

2.04±0.30

0.001*

*significant p-values

M=Male; F=Female; p=p-value

Fig 2 shows the relationship of log FVC, log PEFR and log

FEV to sitting height in the female subjects. The lung

function indices all increased with increase in sitting height.

1

Fig 1 shows the relationship of log FVC, log PEFR and log

FEV to sitting height in the male subjects. The lung function

1

indices all increased with increase in sitting height.

rho = 0.89, p<0.001

rho = 0.71, p<0.001

0

1

2

3

4

2

4

6

8

Peak Expiratoty flow rate (L/sec)

sittingheight Fitted values

Forced vital capacity (litres)

rho = 0.88; p<0.001

rho = 0.80; p<0.001

sittingheight Fitted values

0

1

2

3

4

2

4

6

8

Peak expiratory flow rate (L/sec)

sittingheight Fitted values

Forced Vital Capacity (Litres)

sittingheight Fitted values

rho = 0.88, p<0.001

0

1

2

3

4

rho = 0.89; p<0.001

Forced expiratory volume in 1 second

0

1

2

3

4

sittingheight

Fitted values

Forced expiratory volume in 1 second

sittingheight Fitted values

Table 3 shows the estimated normal ranges for the lung function indices measured in the subjects. These ranges were

calculated using the mean ± 2SD values of the lung functions.

Table 3: Estimated normal ranges of pulmonary function indices by age and gender

Age (years)

PEFR (L/S)

FEV

1

(L)

FVC (L)

M

F

M

F

M

F

6

7

8

9

1

1.14-3.58

1.51-3.91

1.86-4.34

2.82-4.38

2.38-4.58

2.31-5.19

1.72-4.96

2.47-5.31

2.25-7.82

4.42-8.64

4.75-9.19

1.16-3.36

1.45-3.85

1.59-4.23

2.65-4.37

2.09-5.17

1.94-5.58

2.23-6.39

4.14-4.58

4.43-5.19

3.80-6.12

2.98-5.70

0.72-1.20

0.66-1.62

0.93-1.53

0.97-1.41

0.96-1.76

1.11-1.83

0.88-2.24

1.54-2.02

1.42-2.26

1.74-3.14

2.00-3.92

0.51-1.27

0.97-1.01

0.77-1.45

0.99-1.31

0.97-1.49

0.90-1.86

1.18-2.10

1.53-2.13

1.19-2.67

1.42-2.46

1.84-2.40

0.68-1.28

0.67-1.67

0.72-1.70

1.01-3.91

1.28-1.52

1.16-1.96

0.90-2.38

1.54-2.10

1.48-2.28

1.68-3.24

2.14-3.94

0.52-1.28

0.77-1.25

0.80-1.44

1.02-1.34

1.06-1.50

0.96-1.88

1.17-2.17

1.57-2.13

1.24-2.64

1.90-2.10

1.44-2.64

0

1

2

3

4

5

6

*the ranges were obtained using mean± 2SD

4

09

Tables 4 and 5, show the univariate and multivariate

regression models showing the independent determi-

nants of changes in the natural logarithms of PEFR,

Table 5: Univariate and Multivariate regression models

showing the determinants of changes in log PEFR, log

FVC and log FEV

1

for the female subjects

1

FVC and FEV for both male and female subjects. For

Parameter

Univariate analysis Multivariate

analysis

the male subjects: height (p=0.04) was the significant

predictor of PEFR, while sitting height and height were

independent predictors of changes in FVC and FEV1.

*β

p-value

*β

p-value

Log PEFR

Age

Weight

Height

(

p=0.007 and 0.02; 0.004 and 0.027 respectively) For

0.065

0.014

<0.001** 0.052

<0.001** -0.054 0.162

<0.001** -0.006 0.652

0.047**

the female subjects, multivariate analysis showed age as

the most significant predictor of log PEFR and Log

FVC, (p=0.-47 and 0.03 respectively) while, age and

sitting height were the most important predictors of log

FEV1. (p=0.02 and 0.03 respectively)

Sitting height

0.022

<0.001** 0.014

0.174

BSA

0.717

<0.001** 2.395

<0.001** 0.002

0.353

0.839

Chest circumference 0.018

#

Log PEFR= -0.41+0.052(age)

Table 4: Univariate and Multivariate regression models show-

Log FVC

ing the determinants of changes in log PEFR, log FVC and log

Age

0.085

0.021

0.019

0.030

1.029

<0.001** 0.047

<0.001** -0.017 0.467

<0.001** 0.003

<0.001** 0.011

<0.001** 1.010

0.003**

FEV

1

for the male subjects

Weight

Height

Sitting height

BSA

0.719

0.076

0.516

Parameter

Univariate analysis

Multivariate

analysis

*β

p-value

*β

p-value

Chest circumference 0.025

<0.001** -0.008 0.164

Log PEFR

#

Log FVC= -1.39+0.47(age)

Age

Weight

Height

0.09

0.02

0.020

<0.001**

0.014

0.018

0.019

0.44

0.35

0.04**

Log FEV

Age

Weight

Height

Sitting height

BSA

1

0.082

0.020

0.018

0.029

0.991

<0.001** 0.037

<0.001** -0.008 0.740

<0.001** 0.007

<0.001** 0.015

<0.001** 0.217

0.020**

Sitting height

BSA

0.034

1.013

<0.001**

0.012

-1.42

0.004

0.09

0.24

0.59

0.400

0.030**

0.892

Chest circumference 0.034

#

Chest circumference 0.024

<0.001** -0.004 0.458

Log PEFR = -1.51 + 0.019[height]

Log FVC

#

Log FEV1= -1.74+0.037(age)+0.015(sitting height)

#

Age

Weight

0.010

0.024

<0.001**

0.016

0.007

0.15

0.58

*beta the slope of the graph; **significant p values; prediction

equations

Height

0.020

0.033

1.138

<0.001**

0.016

0.010

0.007**

0.02**

1

The PEFR, FVC, FEV of the males in the present study,

Sitting height

BSA

were higher than those of the females in the overall

me₁a₃n which is in ke₁e₉ping with the findings of Glew et

al. Neukrich et al also observed higher FVC and

-0.070 0.35

0.004 0.34

Chest circumference 0.034

#

Log FVC=-2.33=0.016(height cm) + 0.010(sitting height)

1

FEV in males than females in their series on Polyne-

Log FEV

Age

Weight

Height

Sitting height

BSA

1

sian, European and Chinese teenagers. This is because

of a gender dependent lung size difference, which is

present even when males and females are matched for

weight and height, the lung sizes of males are still

greater than that of females, the reason for this is still

0.010

0.024

0.019

0.033

1. 150 <0.001**

0.035 <0.001**

<0.001**

0.010

0.007

0.015

0.009

-0.584 0.390

0.005 0.280

0.260

0.540

0.004**

0.027**

1

9

Chest circumference

unknown. However, some studies have linked this ob-

servation to the higher values in the height and weight of

the boys when compared to the girls at the₁d₇_,i₂f₀ferent ages

except during the adolescent growth spurt.

#

Log FEV1= -2.31+0.05(height)+0.009(sitting height)

#

*

beta the slope of the graph; **significant p values; prediction

equations

The higher lung function indices observed in 12, 13 and

1

4 year old females than their male counterparts may be

attributed to the higher values of the various anthropom-

etric indices in the female subjects in this age range. The

varying changes with different lung function indices at

the age group mentioned may be attributed to the differ-

ent peak growth velocities for different lung function

Discussion

In the present study, there was an increase of PEFR,

FVC and FEV

reported in earlier studies.

1

with age; a₈_,f₁₀e_,a₁₇ture that has been

2

1

indices as observed by Wang et al. This increase in

height and weight are attributed to the growth spur₁t₇_,i₂n₀

females which occurs earlier than that of males.

These ₈observations are consistent with those made by

This is attributable to the

fact that as a child grows₈the lung gets more elastic up to

1

the age of 30-35 years. With this increased elasticity

there is an increase in lung volumes and capacities, but

as a person gets older this natural elasticity of the lungs

decreases,₁l₈eading to reduced lung volumes and

capacities.

1

22

Wang and Rosenthal et al who noted that during the

female pubertal growth spurt all female spirometric val-

ues were higher than those of males. The finding in the

current study is also consistent with that of Kivastik et

4

10

2

3

al who also noted that the growth spurt in sitting and

standing height occurred between ages 11 and 13 years

in girls, and 13 and 15 years in boys, with the growth

spurts of their lung function parameters occurring during

the same periods.

vations are similar to those of some south Indian chil-

dren.

2

6

With all these observations it could be possible that sit-

ting height is not only a factor to be considered in differ-

entiating between Caucasian and African lung function

3

indices, but should also be considered as a parameter in

The significant predictors of PEFR, FVC and FEV

the subjects in the current study were height and sitting

1

for

addition to standing height to be incorporated into pre-

diction equations for calculating lung function in Afri-

can children.

height. This observa₁t₀ion is similar to those of Aderele et

7

al and Olanrewaju who reported pulmonary function

values that correlated more with height than weight.This

is probably because during childhood the lungs increase

in proportion to the increase in height. The increase in

height leads to increase in lung volumes and capaci-

Conclusion

2

4

ties. Furthermore height can be accurately measured

without the use of special equipment or technique; it is

also less₃frequentl₂y₅abnormal than is weight, with chest

This study has attempted to provide a range of norma-

tive values for PEFR, FVC and FEV for rural children

1

in southern Nigeria. Sitting height has been observed to

be an important predictor of lung function indices in

these children. It is however imperative that a nation-

wide study be carried out to provide a pool for the estab-

lishment of normal spirometric values for Nigerian chil-

dren.

1

disease. Ip et al also noted that the standing height

and sitting height were equivalent predictors of lung

volumes. The authors attributed this to the fact that sit-

ting height or trunk length is the closest approximation

of chest size of all the commonly used anthropometric

parameter and recommended that in situations where

standing height cannot be measured, sitting height is an

adequate alternative.

Conflict of interest: none

Funding: none

It is worthy of note that for the male subjects height was

the significant predictor of PEFR while, height and sit-

ting height were significant predictors for the FVC and

Acknowledgement

FEV

1

. For the female subjects however, age was the

independent predictor for PEFR and FVC while Age and

sitting height were the predictors for FEV . These obser-

1

The authors wish to thank Mr Effiong Johnson for his

assistance in data collection.

References

1

2

.

Voter KZ, McBride JT. Diagnos-

tic test of lung function. Paediatr

Rev 1996; 17:53-63.

Pfaff JK, Morgan WJ. Pulmonary

function in infants and children.

Pediatr Cl N Am 1994; 41: 401-

8. Edemeka DBU, Udoma MG, Ibra-

him M. Peak expiratory flow rate

in rural Nigerian children. Sahel

Med J 2000; 3: 37-9.

9. Agaba PA, Thacher TD, Angyo

IA, Agaba EI. Peak expiratory

flow rates in healthy Nigerian

children. J Trop Paediatr 2003;

49: 157-9.

10. Olanrewaju DM. Spirometric

standards for healthy Nigerian

children and adolescents. East Afr

Med J 1991; 68: 812-9.

11. Glew RH, Kassam H, Vander

Voort J, Agaba PA, Harkins M,

VanderJagt DJ. Comparison of

pulmonary function between chil-

dren living in rural and urban areas

in northern Nigeria. J Trop Paedi-

atr 2004; 50: 209-16.

12. Mabrouk AA, Ibrahim SA. Normal

values of lung function test in

Sudanese children. East Afr Med J

1995 ;72: 258-62.

13. Olusanya O, Okpere E, Ezimokhai

M. The importance of social class

in voluntary fertility control in a

developing country. W Afr Med J

1985; 4: 205-12.

14. Harris R. Children and Neonates.

In: Swash M, Ed. Hutchinson’s

clinical methods. Saunders

(publishers) 2004: 376-94.

15. Du Bois, Du Bois EH. A height,

weight formula to estimate the

surface area of man. Proc Soc

Exper Biol Med 1916; 13: 77-9.

Quoted In: Edemeka DBU, Udoma

MG, Ibrahim M. Peak Expiratory

Flow Rate in Rural Nigerian Chil-

dren. Sahel Med J 2000; 3: 37-9.

16. American Association of Respira-

tory Care (AARC) clinical practice

update. Spirometry 1996 update.

Respir Care 1996; 41(7): 629-36

17. Abid Ali M, Vahalia KV, Murtuza

Ali M. A study of respiratory func-

tion in normal school children in

northern Nigeria. Afr J Med Sci

1990: 19; 207-12.

2

3.

3

.

Harik Khan RL, Muller DC, Wise

RA. Racial differences in pulmo-

nary function in African American,

Whites: Effect of racial, nutritional

and environmental factors. Am J

Epidemiol 2004; 160: 893-910.

Breus RAL. Practical pulmonary

functions test. Practitioner 1972;

4

.

2

19: 681-91.

5

6

7

Abid Ali M, Vahalia KV. Some

observations of peak expiratory

flow in normal school children in

Northern Nigeria. West Afr J Med

1

991; 10: 141-9.

.

Onadeko BO, Iyun AO, Sofowora

EO, Adamu SO. Peak expiratory

flow rate in normal Nigerian chil-

dren. Afr J Med med Sci 1984; 13:

18. Wang X, Dockery DW, Wypij D,

Fay M, Ferris BG. Pulmonary

function between 6 and 18 years of

age. Paed Pulmonol 1993; 15(2):

75-88

2

5-32.

.

Aderele WI, Oduwole O. Peak

flow rate in healthy school chil-

dren. Nig J Paediatr 1983; 10: 45-

5

5.

4

11

1

9. Neukrich F, Chansin R, Liard R,

Levallois M, Leproux P. Spiromet-

ric and maximal expiratory flow

volume curve reference standards

for Polynesian, European and Chi-

nese teenagers. Chest 1988; 94:

22. Rosenthal M, Ban SH, Cramer D,

Bush A, Warner JO. Lung function

in white children aged 4-19years. I

-Spirometry. Thorax 1993;

25. Ip MSM, Karlberg EM, Chan K-N,

Karlberg JPE, Luk KDK, Leog

JCY. Lung function reference val-

ues in Chinese children and adoles-

cents in Hong Kong. II. Prediction

equations for plethysmographic

lung volumes. Am J Respir Crit

Care Med 2000; 162: 430-5

48 :794-802

23. Kivastik J, Kingiseppe PH. Lung

function in Estonian children;

effect of sitting height. Clin

Physiol 1995; 15 (3): 287-96.

24. American Thoracic Society. Lung

function testing: selection of refer-

ence values and interpretative

strategies. Am Rev Respir Dis

1991; 144: 1202-18.

7

92-798.

2

0. Carson JWK, Hoey H, Taylor

MRH. Growth and other factors

affecting peak expiratory flow rate.

Arch Dis Child 1989; 64: 96-102

1. Wang X, Dockery DW, Wypjj D et

al. Pulmonary function growth

velocity in children 6 to 18 years

of age. Am Rev Resp Dis 1993;

26. Vijayan VK, Reetha AM, Kuppu-

rao KV, Venkatesan P,

Thilakavathy S. Pulmonary func-

tion in normal south Indian chil-

dren aged 7 to 19 years. Indian J

Chest Dis Allied Sci 2000; 42: 147

-156.

1

48: 1502-8.