Maximal Expiratory Flow Rates such as Peak Expiratory Flow Rate (PEFR).

rates at 25%, 50% and 75% of forced vita) capacity (V max 25%, V max 50% and V

max 75%) and forced expiratory flow during the middle half of forced vital capacity

(FEF 25-75%) were measured in 273 healthy non-smoking adults (144 males, 129

females) aged 15-63 years living in Madras. Regression equations were derived for

men and women for predicting maximal expiratory flow rates for adults in South India.

Expiratory Flow Rates at lower lung volumes in men were similar to those reported for

caucasians, but higher than those reported for western Indian Subjects. However, in

women the flow rates were similar to those of western Indians and lower than those of

caucasians, probably due to indoor air pollution since childhood. These data may suggest

that expiratory flow rates at lower lung volumes may not show ethnic variability

Kuppurao, K V

Sankaran, K

Venkatesan, P

Vijayan, V K

NIRT Institutional Repository

Indian J Physiol Pharmacol 1993; 37(4): 291-297REFERENCE VALUES AND PREDICTION EQUATIONS FOR MAXIMAL EXPIRATORYFLOW RATES IN-NON-SMOKING NORMAL SUBJECTS IN MADRASV. K.VIJAYAN*, K. V. KUPPU RAO, P. VENKATESAN AND K. SANKARANCardio-Pulmonary Medicine Unit,TB Research Centre,Indian Council of Medical Research,Madras - 600 031( Received on November 23,1992 )Abstract : Maximal Expiratory Flow Rates such as Peak Expiratory Flow Rate (PEFR).rates at 25%, 50% and 75% of forced vita) capacity (V max 25%, V max 50% and Vmax 75%) and forced expiratory flow during the middle half of forced vital capacity(FEF 25-75%) were measured in 273 healthy non-smoking adults (144 males, 129females) aged 15-63 years living in Madras. Regression equations were derived formen and women for predicting maximal expiratory flow rates for adults in South India.Expiratory Flow Rates at lower lung volumes in men were similar to those reported forcaucasians, but higher than those reported for western Indian Subjects. However, inwomen the flow rates were similar to those of western Indians and lower than those ofcaucasians, probably due to indoor air pollution since childhood. These data may suggestthat expiratory flow rates at lower lung volumes may not show ethnic variability.Key words : expiratory flow rates lung function prediction equationsI N T R O D U C T I O NAs differences in pulmonary functions are knownto occur due to various reasons such as ethnic origin,environmental conditions and altitude (1), we hadreported regression equations for men and women forpredicting normal pulmonary functions (spirometry, lungvolumes and diffusing capacity measurements) for youngadults in South India (2). However, such regressionequations are not currently available for maximalexpiratory flow volume measurements in healthy SouthIndian subjects, although such a study had been reportedfor western Indian subjects (3). We, therefore, undertooka study to derive regression equations for predictingnormal expiratory Flow-volume measurements in healthySouth Indian subjects.SubjectsWe studied 273 Non-smoking Indians (144 malesand. 129 females) living in Madras and aged 15-63years (mean age, males 29.9±12.7 yr and females30.l±9.4 yr). They included relatives of patientsatte ding the Tuberculosis Research Centre, staffmembers, manual workers and executives, to obtain across section of the normal inhabitants of Madras city.Th  pr portion of subjects who declined to take partin this study was less than 1%. Subjects were eligiblefor the study if they were ethnic South Indians, had nostructural deformity of the thoracic cage and were freefro  respiratory infections and had been so for at leastthree months before the test. None of the subjects hadany car io-respiratory disease, as assessed by detailedhistory, physical examination, chest radiography and12 lead electrocardiography.TestsMaximal Expiratory Flow Rates such as peakexpiratory flow rate (PEFR), rates at 25%, 50% and75% of Forced Vital Capacity (V max 25%, V max50% and V max 75%) and forced expiratory flow during*Corresponding Author292 Vijayan et al Indian J Physiol Pharmacol 1993; 37(4)the middle half of forced vital capacity (FEF 25-75%)were carried out with Transfer Test Model C (PKMorgan, Chatham UK), readings being obtained froma Data Dec Computer. Sex, ethnic identity, standingheight to the nearest centimeter without shoes, weightin kilograms, age, smoking habit, occupation andspirometer temperature were recorded for all subjectsbefore testing. The tests were carried out with thesubjects seated and with a nose clip applied. The equipment was calibrated fully every day. The coefficient ofvariation of six subjects studied over one year was lessthan 3% for PEFR, FEF 25-75% and V max 25%;<5% for V max 50% and 10% for V max 75%.Maximal Expiratory Flow Rates: Maximalexpiratory flow-volume loops were recorded by askingthe subject to take a deep breath until he/she breathedin to total lung capacity (TLC) and to wrap his/hermouth tightly around a mouth piece, and on a givensignal to breath out to residual volume, and finallysuck it all back in again as fast as possible to TLC,taking care to keep his/her back against the chair-backall of the time (4). At least three such flow-volumeloop (F-V loop) manoeuvres were obtained for eachsubject. The highest value (5) obtained from any ofthe three tracings was used for calculation of PEFR.Values of FEF 25-75%, V max 25%, V max 50% andV max 75% were derived from the single best test andthe best test was defined as the one with the largestsum of FEV1 and FVC (6,7).Statistical methodsBest fining cross sectional equations were derivedseparately for men and women by multiple linearregression analysis. Age, height and weight were enteredinto the equation for all expiratory flow measurements.Age, height and weight interactions were tested forsignificance by means of stepwise regression procedure.Residuals were calculated and tested for each of thesebest fitting models for each sex. The goodness of fit ofthe models was also tested by examining correlationsof residuals with age, height and weight and byinspecting groups of residuals versus predicted valuesto confirm the absence of a curvilinear pattern.All analysis were performed with the SPSS/PCstatistical computing packagee on an IBM/XTcompatible personal computer. Unless otherwise stated,the term significant is used to imply a P value of lessthan 0.05.RESULTSThe mean (SD) height was 166.1 (7.7) cm inmen and 151.8 (5.8) cm in women, and weight was56.0 (12.7) and 45.7 (9.1) kg. In men, the mean FVCwas 3.42 (0.64) litres, FEV1 2.92 (0.60) litres and FEV1/FVC % 85 (7.2); in women the mean FVC 2.30 (0.35)litres, FEV1 1.99 (0.31) litres and FEV1/FVC % 86.8(6.4).Both height and weight in men showed significantpositive correlations with PEFR, FEF 25 -75%, V max25% and V max 50%. Age had significant negativecorrelation with FEF 25-75% and V max 50% inaddition. V max 75% had significant negative correlationwith age and positive correlation with height in men(Table 1). In women, height and weight had significantpositive correlations with PEFR and V max 25%. FEF25-75% and V max 50% had significant negativecorrelation with age and positive correlation with height.Age was negatively correlated with V max 75% inwomen (Table II). Flow Volume loop recorded from anormal non-smoking South Indian subject is shown inFig. 1. Typical F-V loops obtained from patients withbronchial asthma and chronic obstructive airways diseaseare given in Fig. 2 and 3.PEFR = Peak expiratory flow ratePIFR = Peak inspiratory flow rateFVC = Forced vital capacityRV = Residual volumeFig. 1 : Flow-Volume Loop in a normal non-smokingS. lndian subject.Indian J Physiol Pharmacol 1993; 37(4) Maximal Expiratory Rates in S. Indian Subjects293PRE = Pre -bronchodilator testPOST = Post -bronchodilatar testFig. 2 : Flow-Volmnc Loop in patient with bronchialasthma.The multiple regression- equations for menand women based on age, height and weight areshown in Tables I and II. In order to have homogenousVolume (litres)groups and also to eliminate the influence of growth,separate regression equations were derived for the ageroup 15-24 years and 25-63 years in both sexes andTABLE I: Regression relationships for predicting maximal expiratory flow rates (litres/second)for age group 15-63 years from age (y), height (cm) and weight (kg) in healthySouth Indian men.Regression coefficients Correlation coefficientsMeasurement Mean SDConstant Standard         Age Height Weight     Multiple RError Age Height WeightPEFR 7.21 1.87 –5.837 –0.017 0.064 0.054 0.553 1.574 0.023 0.504** 0.495**V Max 25% 5.80 1.72 –5.163 –0.027 0.054 0.051 0.549  1.455  –0.060 0.454** 0.458**V Max 50% 4.01 1.28 –2.969 –0.033 0.036 0.037 0.544 1.087 –0.210* 0.423** 0.416**V MAX 75% 1.77 0.90 –4.846 –0.033        0.046               – 0.568 0.749 –0.426** 0.354** 0.136FEF 25-75% 3.96 1.18 –4.626 –0.031 0.048 0.029 0.587 0.966 –0.244* 0.474** 0.411***P<0.01; **P<0.001PEFR : Peak Expiratory Flow RateV max 25%, V max 50%, V max 75% : Maximal expiratory flow rates at 25%, 50% and 75% of Forced Vital Capacity.FEF 25-75%: Forced Expiratory Flow during the middle half of Forced Vital Capacity.294  Vijayan et al Indian J Physiol Pharmacol 1993; 37(4)TABLE II: Regression relationships for predicting maximal expiratory flow rates (litres/second)for age group 15-63 years from age (y), height (cm) and weight (kg) in healthySouth Indian women.Measurement Mean SD ConstantRegression coefficients Correlation coefficientsStandardAge Height Weight    Multiple RError Age Height WeightPEFR 4.42 1.04 –0.179 –0.006 0.025 0.021 0.275 1.013 –0.118 0.230* 0.230*V Max 25% 3.64 1.03 –3.934 –0.004 0.045 0.019 0.360 0.970 –0.011 0.322** 0.269*V Max 50% 2.69 0.75 –0.075 –0.020 0.020 0.007 0.320 0.699 –0.241* 0.225* 0.073V MAX 75% 1.35 0.58 0.346 –0.027 0.012 – 0.473 0.512 –0.457** 0.171 –0.159FEF 25-75% 2.68 0.70 –2.001 –0.015 0.034 – 0.368 0.653 -0.239” 0.305** 0.113*P<0.01  ** P< 0.001Abbreviations as in Table I.results are shown in Tables III and IV. PredictedPredicted values= K + (age in years x agevalues are derived from the regression equations asc efficient) + (standing height in cms x heightfollows: coefficient) + (weight in kg x weight coefficient), whereK is the constantTABLE III: Regression equations for predicting maximal expiratory flow rates (litres/second)for age group 15-24 years from age (y), height (cm) and weight (kg).Mean SD ConstantRegression coefficientMultiple R Standard ErrorAge Height WeightMales ( n : 67)PEFRV max 25%V max 50%V max 75%FEF 25-75%Females ( n:37 )PEFRV max 25%V max 50%V max 75%FEF 25-75%6.93 1.88 –11.939 0.155 0.096 0.562 1.5765.77 1.71 –11.181 0.190 0.081 0.577 1.4164.20 1.40 –9.109 0.189 0.059 0.584 1.1532.14 0.88 –6.391 0.088 0.042 0.559 0.7374.16 1.28 –5.795 0.140 0.036 0.027 0.654 0.9874.25 1.163.41 0.962.83 0.831.63 0.582.77 0.76–1.299 0.035 0.017 0.054 0.317 1.145–1.223 –0.021 0.016 0.064 0.394 0.9240.153 0.020 0.003 0.045 0.313 0.824–1.345 0.011 0.015 0.011 0.216 0.593–0.921 0.013 0.012 0.037 0.319 0.754Abbreviations as in Table I.Indian J Physiol Pharmacol 1993; 37(4) Maximal Expiratory Rates in S. Indian Subjects295TABLE  IV : Regression equations for predicting maximal expiratory flow rates (litres/second)for age group 25-63 years from age (y), height (cm) and weight (kg).Mean SD ConstantRegression coefficientsMultiple R Stanard ErrorAge Height WeightMales (n : 77)PEFR 7.46 1.84 –6.558 –0.047 0.677 0.049 0.557 1.559V max 25% 5.82 1.74 –7.276 –0.039 0.068 0.053 0.561 1.472V max 50% 3.84 1.15 –3.706 –0.034 0.043 0.028 0.537 0.992V max 75% 1.45 0.81 –4.018 –0.029 0.040 0.494 0.710FEF 25-75% 3.80 1.07 –5.521 –0.033 0.055 0.023 0.592 0.880Females (n:92)PEFR            4.48 0.99 0.320 –0.0196 0.027 0.015 0.310 0.958V max 25% 3.74 1.04 –5.155 –0.0161 0.062 0.392 0.969V max 50% 263 0.68 –0.445 –0.0226 O.025 0.371 0.640V max 75% 1.23 0.53 –0.262 –0.0242 0.019 –0.011 0.475 0.476FEF 25-75% 266 0.68 –1.955 –0.0250 0.036 0.465 0.606Abbreviations as in Table LThe predicted values of various expiratory flow rates155 cms for women) and weight (55 kg for men, 45 kgobtained from these regression equations for subjectsfor women) are compared with those from other studiesof specified age (30 years), height (165 cms for men,in Tables V and VI.TABLE V : Maximal Expiratory Flow Rates from various studies in men of specifiedage (30 years), height (165 cm) and weight (55 kg).Reference PEFR(l/s) V max 25% (l/s) V max 50% (1/s) V max 75% (l/s) FEF 25-75% (l/s)Udwadia3Bass8Knudson9Amin10Natarajan11Ayub12Vijayan(This study)7.3 – 3.9 1.6 3.27.7 7.1 5.0 1.9 –– – 4.6 1.9 4.07.1 – – – –8.4 – – – –8.6 7.0 4.4 1.6 –7.2 5.7 3.9 1.8 4.0Abbreviations as in Table LTABLE VI : Maximal Expiratory Flow Rates from various studies in women of specifiedage (30 years), height (150 an) and weight (45 kg).Reference PEFR(l/s) V max 25% (1/s) V max 50% (l/s) V max 75% (1/s) FEF 25-75% (1/s)Udwadia3Bass8Knudson9Amin10Natarajan11Ayub12Vijayan(This study)4.9 – 3.1 1.4 2.75.7 5.5 4.5 1.9 –– – 3.8 1.8 3.24.5 – – – –6.1 – – – –3.9 3.8 2.8 1.3 –4.5 3.8 2.7 1.4 2.8Abbreviations as in Table I.296 Vijayan et al Indian J Physiol Phamacol 1993; 37(4)DISCUSSIONThe detection of pulmonary function abnormalitiesbefore clinical symptoms or signs develop helps inearly diagnosis and treatment, thus helping in haltingthe progression of disease. The maximal expiratoryflow rates at specific lung volumes recorded during aflow-volume loop manoeuvre especially the terminalsegment of the curve can be utilised as useful screeningtests for early detection of pulmonary functionabnormalities (8). While setting up a pulmonary functionlaboratory, the most important test to be establishedinitially is flow-volume loop measurements (4). Thesefactors along with the observation that differences inpulmonary function may be due to various reasonsespecially goegraphic differences (1), emphasise theneed for establishing regression equations to predictinstantaneous flow rates at specific lung volumes on aregional basis in a subcontinent like India.The significant negative correlation of age withexpiratory flow rates in both men and women in thisstudy is similar to the findings reported in earlier studies(3.8). suggesting that there will be an age-related declinein these measurements as age advances. We had shownpreviously that pulmonary function measurements suchas spirometry, lung volumes and diffusing capacitymeasurements in South Indians were similar to thosereported for subjects from Western India, but lowerthan those for North Indians and Caucasians (2).A similar study of maximal expiratory flow-volumecurve in normal subjects had been reported in WesternIndians living in Bombay (3). Expiratory flow rate athigher lung volumes (PEFR) in males in the presentstudy was similar to that of subjects from Bombay.However. the flow rates at lower lung volumes (Vmax 75% and FEF 25-75%) were higher in our studysubjects and comparable to those reported in Caucasians(8,9). On the other hand, in females, the flow rates atlower lung volumes were similar to those of subjectsfrom Bombay (3) and lower than those of Caucasians(8, 9). The Peak expiratory flow rate in both sexes inthis study was similar to those reported by Amin andPande (10), but lower than those published by Natarajan(11) and Knudson (9). In a previous study in normalPakistanis (12), it had been found that expiratory flowrates at high lung volumes in men were similar tothose of European and American studies, and it hadbeen suggested that either elastic recoil of the lung ata given lung volume in men was greater in Pakistanisand/or large airways resistance was high. They hadalso noticed that maximal expiratory flow rates in womenwere lower than those reported in European populationsand thought it to be due to their smaller lung volumes.Since the early segment of the maximal expiratoryflow volume loop is effort dependent, flow rates inthis part are less reproducible and co-operation fromthe patients is required for optimal results (13). On theot r hand, the terminal segment of the maximal flowvolume loop is effort- independent, and maximal flowin this part is governed by the elastic recoil of thelungs and cross-sectional area of the airways betweenalv oli and the airways in which dynamic compressionoccurs. The flow rates in the terminal portion of theexpiratory F-V loop are therefore, considered to reflectthe changes in small airways, and F-V curves obtainedafter a week effort may also thus, provide informationregarding flow rates in small airways (13). However,the flow rates in the terminal portion of the flow-volumecurves have high coefficients of variation, but thecurvilinearity of the F-V curve to the volume axis inairway obstruction is reproducible. Separate F-V loopsrecorded while breathing air and a mixture of helium(80%) and oxygen (20%) reduce the intersubjectvariability by using the subject as his own control (14).The volume at which flow is same for air and helium/oxygen mixture during comparable forced expiratorymanoeuvres (volume of isoflow) is considered as oneof the best tests of small airway dysfunction (14).It had been suggested that environmental pollutionespecially in a city like Bombay (3) may produce silentdi ease of the small airways resulting in lower V maxat lower lung volumes. The higher V max at lowerl ng volumes in non-smoking males from Madrascompared to Bombay subjects may, therefore, be dueto comparatively low levels of environmental pollutionin Madras city. The similar flow rates (V max 75%and FEF 25-75%) in females from Madras and Bombaymay then, be due to the domestic (Indoor) air pollution,s these women rely on biomass fuels (wood, cropresidues and animal dug) for cooking since childhood(15). Expiratory flow rates at lower lung volumes arereduced as a result of flow limitations in small airwaysIndian J Physiol Pharmacol 1993; 37(4) Maximal Expiratory Rates in S. Indian Subjects297(8). Small airways are defined as those with diameterless than 2 mm (16). Therefore, flow rates in airwaysless than 2 mm diameter in normal subjects should betheoretically similar in all ethnic groups, as revealedby this study. Similarly, there should also be nodifferences in flow rates at lower lung volumes betweensexes and this has been brought out by similar V max75% in both sexes in studies reported by Bass andKnudson (8, 9). More studies are required to clarifythese points.REFERENCES1. Woolcock JA, Colman MH, Blackbum CRB. Factor affecting9. Knudson RJ, Lebowitz MD, Holberg CJ, Burrows B. Changesnormal values for ventilatory lung functions. Am Rev Respir in the normalmaximal expiratory flow-volume curve with growthDir 1972; 106: 692-709. and aging. Am Rev Respir Dir 1983; 127: 725-734.2. Vijayan VK, Kuppurao KV, Venkatesan P, Sankaran K,Prabhakar R. Pulmonary functions in healthy young adult Indiansin Madras. Thorax 1990.45: 611-615.10. Amin SK, Pande RS. Peak Expiratory Flow Rate in Normalsubjects. Ind J Chest Dir & All Sci 1978;20: 80-83.3. Udwadia FE, Sunavala JD, Shetye VM, Jain PK. The MaximalExpiratory Flow - Volume curve in normal subjects in India.Chest 1986; 89: 852-856.11. Natarajan A, Radha K. Peak Expiratory Flow Rate in NormalSouth Indians. Ind J Chest Dir & All Sci 1978; 20: 178-182.4. Denison DM. Physiology. In: Clarke TJH. Clinical Investigationof Respiratory Disease: London. Chapman and Hall. 1981; 33-94.12. Ayub M, Zaidi SH, Burki NK. Spirometry and Flow-Volumecurves in healthy, normal Pakistanis. Br J Dis Chest 1987;81: 35-44.5. Gregg I, Nunn AJ. Peak expiratory flow in normal subjects.Brit Med J 1973; 3: 282-284.13. Hinsbaw HC, Murray JF. Diagnostic Procedures: Respiratoryphysiology and respiratory function testing in diseases of thechest Ed. Hinshaw and Murray, Philadelphia. WB Saundersco. 4th Edition 1980: 75-143.6. ATS statement Snowbird workshop on standadisation ofspirometry. Am Rev Respir Dir 1979; 119: 831-838.7. Mathew V, Walter S. Spirometry - A companion of the beattest, the mean test and the maximal test. Indian J Chest Dir &All Sci 1987; 29: 198-203.14. Cochrane GM, Screeing. In: Clinical investigation of respiratorydiseases. Ed. Clark TJH, Chapman and Hall, London 1981 :117-137.15. Deknoning HW, Smith KR, Last JM. Biomass fuel combustionand health. Bull WHO 1985; 63: 11-26.8. Bass H. The Flow Volume Loop: Normal standards andabnormalities in chronic obstructive pulmonary disease. Che t1973; 63: 171-176.16. Macklem P, Thurlbeck WM, Fraser RG. Chronic obstructivedisease of small airways. Ann Intern Med 1971; 74: 167-177.

Reference values and prediction equations for maximal expiratory flow rates in non-smoking normal subjects in Madras

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Reference values and prediction equations for maximal expiratory flow rates in non-smoking normal subjects in Madras

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