Document Gm9y8eLxbK7rdE38KDRXNOJdx

lo00 NOTES which obstruction of the main bronchi cannot be distinguished. a fact also reported by Miller and Hyatt.26 In some patients, the recordiw of the Bowvolume curves were extremely noisy, as noted by Miller and Hyattw; noisy records of the relationship of inspiratory flow to alveolar pmsure also were observed. In 6 of the patients, there was a systematic difference between the FRC measured by the helium dilution method and the plethysmographic TGV. This difference did not seem to be due to technical e m , since it was reproducible during a few days. In patients with obstruction of the main bronchi (No.13 and 14). it was readily explained by air trapping, which was evident in radiographs of the chest. In the patients with upper airway stenosis, i n whom disturbance of the distribution of ventilation usualIy does not m r , 2 2 . , 2 4 , 3 1 the significance of this difference Grimaud,C.: C. R. Soc. Biol. (Paris), 1971,165, 178. 31 Simonsson, B. G., and Malmberg, R.: Thor- ax, 1964,19,416. was not clear. Whatever the cam, Raw will be underestimated if SRaw is not considered. After surgical correction of the stemxis. tbc difference between FRC and TGV disappeared(Patient5 No. 4, 8, 9). Also, all parametem studied were dramatically impmved, the changes in SRaw being the most importar.t. It is noteworthy that total lung capaaty measured by the helium dilation method did not changesignificantly. c.J. YEJUiAULT32 M. ENCLERT R.SE~CYSW A. DE Cosm Departments of Resfi'ratory Diseases and Cardiology, Hdpital Universitaire Saint-Pime, Brusseb, Belgium 82-We thank Dr. P. Vanderhoeft (Head, Department of Thoracic Surgery) and Dr. H e m . bert (Head, Department of Otorhinolaryngology), who referred to us most of the patienu studied. \ NORMAL VALUES FOR THE RATIO OF ONE-SECOND FORCED EXPIRATORY VOLUME TO FORCED VITAL CAPACITY'*' Summary Normal standards for the ratio of 1-second forced expiratory valume to forced vital capacity have previously either assumed a value m a t e r than 70 or 75 per cent or else provided prediction formulas based on populations of small size or groups that included agarette smokers. The ratio was measured in 963 healthy, nonsmoking men and women. Negative correlation was obtained with age, and no significant correlation was found with standing height, Regression equations were derived for men and women. T h e addition o standing height did not affect the multiple correlation ooefficient and standard error of the estimate for women but did have a small influence for men. Normal mean values and standard devi- ations by age decade were tabulated. With thesc more precise values, differentiation between restrictive and obstructive abnormalities is improved. The relative contribution of each process to impairment of ventilation is revealed by the relationship of the forced vital capacity and the ratio of 1-second forced expiratory to forced vital capaaty. (Received in original form June I , I973 and in r&d form July 13,1973) 1suppofied by a grant from the Oregon TU& d a ~a d Respiratory Disease M a t i o n . 2Rquests for reprints should be addressed to Dr. Jamea F. Morris, Veterans Administration Hospital, Portland, Oregon9i297. The ratio of the forced expiratory volume in 1 second (FEV1) to the forced vital capacity (FK) is a cormonly computed vzlue. The *kction normal predicted values for the ratio has been even less precise than that of other spirometric measurements, Many investigators recommend either 70 or 75 per cent as the lower limit of nor- AMERICAN REVIEW OF RESPIR.4TORY DISEASE, VOLUME 108. 1973 Ii t 1 i I I 1 I I I I b \ I I 1 NOTES 1001 mal for the ratio.3-10 Prediction formulas have been reported by others, using populations varying in number, smoking habits, test position, and health status.11-15 The present report provides normal standards for the ratio, FEVJFVC, based on a healthy, nonsmoking population. A previously published study described the population and testing procedures.16 Briefly, the subjects were all healthy nonsmokers, 509 men and 454 women, 20 to 79 years of age. They l i d in an area of Oregon relatively free from urban air pollution. A questionnaire eliminated subjects with a history of cigarette smoking, pulmonary disease, or occu- pational exposure to airborne pollutants. Standing height was measured without shoes. Spirometric tests were performed in the standing position using a calibrated Stead-Wells spirometer and a nose clip. T h e best &ort of at least 2 maximal efforts was selected. The volumes were corrected to body temperature and pressure, saturated with water vapor (BTPS). The normal values f o r FEV,/FVC of the 963 healthy, nonsmoking men and women were cal- d a t e d for each age decade and are shown in table 1. There was a progressive decline in the Values with age, except for the eighth decade in men, but this group had a small sample num- SGaensler. E. A., and Wright, G. W.: Arch. bviron. Health (Chicago), 1966,12,46. 4Snider, G. L.: J. A. M. A., 1966,197,1095. SLeiner, G. C., Abramowitz, S., Small, J. J,, M y , V. B., and Lewis, W. A: Amer. Rev. Rep. Dis., 1963,88,644. 6Dickman. M. L.,Schmidt, C. D., and GardW, R. M.: Amer. Rev. Resp. Dis., 1971. 104, 680. TTiffeneau, R., Bousser, J., and Drutel, P.: Paris Med., 1949,39,543. aMiller, W. F., Johnson, R. L., Jr., and Wu, N.:J. Appl. Physiol., 1959,14,157. OPemberton, J., and Flanagan, E. G.: J. Appl. Phgsiol.. 1956,9,291. 10 Kory, R. C.. Callahan, R., Boren, H. G., and Syner. J. C.: Amer. J. Med., 1961,30,243. IlBerglund, E.,Birath, G., Bjure, J., Crimby, G., Kjellmer, I., Wqvist, L., and %derholm, B.:Acta Med. Scand., 1963,173,185. 12Grimby. G., and Soderholm, B.: Acta Med. stand., 1965,173,199. IaCotes, J. E.,Rwiter, C. E., Higgins, I. T. T., .nd Gilson, J. C., Brit. Med. J., 1966, 1, 1016. 14Anderson, T. W., Brown, J. R., Hall, J. W.. md Shephard, R. J.: Respiration, 1968.21, 140, 16 Ringqvist, T.: Scand. J. Clin. Lab. Invest., 1% (Supplement, p. 1). 16 Morris, J. F., Koski, A., and Johnson, L. C.: h e r . Rev.R e p . Dia., 1971.103,57. TABLE 1 NORMAL VALUES FOR THE RATIO OF 1- SECOND FORCED EXPIRATORY VOLUME TO FORCED VITAL CAPACITY BY AGE DECADES Age Mean Mean FEW/ Group Age Height N C . % (years) (years)(inches) (mean) No.of Sub/SD) jecrs Men 20-29 23.54 70.78 30-39 34.37 70.22 40-49 44.15 69.89 50-59 53.82 69.86 60-69 64.00 68.29 70-79 72.75 66.67 Women 20-29 24.99 64.71 30-39 34.37 64.65 40-49 44.61 64.22 50-59 53.54 63.59 60-69 64.17 63.41 70-79 74.07 62.56 80.21 75.40 75.03 72.13 70.73' 73.91 80.44 77.21 76.01 74.49 73.59 70.10 6.80 9.38 5.68 7.57 11.37 4.82 166 143 94 67 27 12 6.09 6.38 5.78 7.48 9.06 9.45 125 103 88 69 41 28 ber. Regression equations were derived using variables of age and sex as shown in table 2. The correlations coefficients for variables of age, sex and standing height are shown in table 3. When height was included in the regression equations, no measurable change occurred in the multiple correlation coefficients and standard deviations for women. There was, however, a l per cent increase in the values for men. This agrees with the findings of Anderson and associates.14 It appean that the correlation is primarily between age and height variables for men rather than between FEV,/FVC and height. 0.0 The use of the FEV,/FEV was first advocated by Tiffeneau and associates in 19497 and later by Gaensler in 1951.1: Since then, reports have proposed its use for determining the presence of airway obstruction. Various values for mean normal standards or regression equations for adults tested in sitting or standing position have been reported.3-15 The lack of precision in normal values may have hampered use of the ratio. The value of the ratio has been in the interpretation of the f o r d expiratory curve. The relationship between FVC or VC and the FEV,/FVC is believed to aid in the discrimination between pulmonary impairment due to a restricting process which limits lung inflation and that due to airway obstruction (table 4). If only the 2 measurements are calculated. the r e l a t i d i p does lTGaensler, E. A.: Amer. Rev. Tuberc, 1951, 64,256. . 1002 NOTES TABLE 2 PREDICTION FORMULAS FOR THE RATIO OF 1-SECOND FORCED EXPIRATORY VOLUME TO FORCED VITAL CAPACITY WITH MULTIPLE CORREIATtON COEFFlClENTS .PredictionFormula R SEE' Men -FEVi /FVC,% 84.64 0.2253At FEW /FVC.%= 107.12-0.3118H" -0.242% -Women F W i/FVC.% = 84.23 0.1789A - -FWi /FVC,% J 88.70 0.0679H 0.181% 'SEE = standarderror of the estimate tA = m e inyears **H=heightin inches 0.38 7.83 040 7.79 0.39 6.84 0.39 6.84 3 71 provide an approximate method of differentiation. In normal persons. VC and FVC are similar. With increasing airway obstruction, the VC can remain in the normal range while air trap ping diminishes the FVC. When this occurs, us= of the ratio to differentiate between restrictive and obstructive impairment becomes less useful. Other elements of the forced expiratory curve are also used to demonstrate the presence of airway obstruction. In particular, the forced midexpiratory flow (FEF2F,5& has been reported to possess more sensitivity for determining airway obstruction than the FEV,, either as per cent of predicted or per cent of FVC.l%lQ Kuperman and Riker found the correlation of the mwimum midexpiratory flow with FEV,/VC sufficiently high that they recommended that the FEV,/VC should suftice for ventilatory function screening of asymptomatic individuaIs.20 The FEF,,, is believed to reflect frictional resistance of small airways, particularly, the diameter of the small poorly supported ainvays.21 .4fter the initial 25 per cent of the forced expiratory curve, there is little or no effort-dependence except for the terminal portion22 The effect of a reduced VC or FVC upon the forced midexpiratory flow is difficult to estimate. Objections have been raised to the use of the FEV,/FVC.23. 2.) The objections result from ob- 1s Leuallen, F. C., and Fowler, W. S.: Amer. Rev. Tuberc, 1955,72,783. lOLloyd, T. C., Jr., and Wright, G. W.: Amer. Rev. Resp. Dis., 1963.87,529. 20 Kuperman, A. S. and Riker. J. B.: Amer. Rev. Resp. Dis., 1973,Z07,251. 21 McFadden, E. R.. Jr.. and Linden. D. A.: Amer. J. Med., 1972.52,725. 22 Mead, J.,,Turner. J. M.,Macklem, P.T., and Little, J. B.: J. Appl. Physiol., 1967,22,95. 29Hugh-Jones. P.: Brit. J. Anaesth., 1958, 30, 107. xrvations of respiratory conditions prod- parallel effects of impairment of both the and FEV,. Reference to table 4 would inthat if the FVC is reduced but the FEV,/FVC, is maintained in the normal range, this would indicate a restrictive procgs rather than a arm. bined restrictive and obstructive process even if the FEV, was below the predicted normal w. Certain hazards of interpretation of the "EVI/ FVC should be pointed out to avoid too liinterpretation. If a primary disease such as b n chopenic carcinoma obstructs a larger airway producing atelectasis, this could lead to a redFVC or VC. The secondary restriction might ma& the basic obstructive p'ocess. Similarly, the de. velopment of parenchymal emphysema may re. sult in airway obstruction from loss of peribm. chiolar radial traction produang functional airway obstruction. Probably the greatest limitation to interpreting the FEV,/FVC as an indicator of airway obstruction is the relative h e n sitivity of the FEV, to obstruction of terminal bronchioles. The time of day when the tests are performed probably has no important influence on the mtio either in normal subjects or patients, Lewinsohn, and co-workers25 found large spontaneous variations in both FVC and FEV, from 9 a.m. to 5 p.m. in patients with chronic obstructive pulmonary disease. The variation was reported to bt similar in magnitude and direction in individual subjects, producing a relatively constant FEV,/FVC. Use of the SD is valuable to avoid i n t e r p e a relatively low FEV,/FVC as abnormal when resulting from an above mean normal FVC OI 24 Higgins, I. T. T., and Cochrane, A. L.:Brit. J. Ind. Med.,1961,Z8,93. 25Lewinsohn, H.C., Capel, L. H.,and smut. J.: Brit. Med.J., 1960,1,462. i ! I I I I NOTES loo3 wing FVC licate FVC, ..odd corn. en if ingr. 3',i teral ron. PO. rad M,k de re. .on ' air. ita. idi. sn. nal Id nin. .U* IO IItw d. nt '8 .n -Df 1. b v t 'ABLE 3 :OEFFICIENTS OF AGE, __ 4T. AND RATIO OF 1-SECOND FORCED __ -4TORY VOLUME TO FORCED VITAL CAPACITY BY AGE DECADES ioht K/NC 1.00 -0.27 -0.38 -0.27 1.oo 0.003 -0.38 O.qO3 1.oo TABLE 4 RELATIONSHIP OF FORCED VITAL CAPACITY AND FORCED EXPIRATORY VOLUME IN 1 SECOND FVC FEV, /FVC Interpretation Normal Normal LOW LOW Normal Low Normal Low Normal Airway obstruction Lungrestriction Both obstruction and restriction 'PNv/NC 1.00 -0.25 -0.39 -0.25 1.oo 0.08 -0.39 0.08 1.oo iro and co-worked6 found that athhad relatively greater than normal VC than FEV,. The resulting FEV,/FVC to be relatively low. This might have re m development of acfeSSOry m d e s of the volume of the thorax. es, the same workers found that if the low ratio remained low after bronche y, it could indicate either insuffi- Or withS f S h 1 2 types of patients could be distients with asthma had a amstant the patient's normal vc ; then, with continued treatment, ., ,W., and Patterson. J. L..Jr.: h e r . *9. Dia.. 1962,85,191. -&n, W. B., and Hugh-Jones, P.:Brit. J.0 1m,I, 109% the FEV,/FVC of patients with emphysema remained low. Because the FVC and FEV, are probably th most commonly used tests of pulmonaq function. it would Seem desirable to include rhe measurement of FEV,/FVC routinely. Despite the limitations inherent in the ratio, it d m otfcr a reasonable estimate of the degree of restrictive and obstructive pulmonary impairment. The use of the values in table 1 will provide maximal accuracy in using the ratio. With the advent ot newer techniques of determining airway ob struction such as frequency-dependent aomplia c e and closing lung volume, more sensitipe testing can be done. Until such a test c a b~c ~ made simple and inexpensive, spirometry will bc commonly used to assess P U ~ ~ O M I Yfunctiooll impairment. F. WILLIAMp, TEMPLE Aamua KosKI of Medin'ne University of Oregon Medical School, Veterans Administration Hosfiital Oregon and Deportment of Health Education Oregon State University Coroollis, Oregon