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Variations in the response of normal persons and cardiac patients to the Nylin heart function test
VARIATIONS IN THE RESPONSE OF NORMAL CARDIAC PATIENTS TO THE NYLIX FUNCTION TEST
PERSONS HEART
.4ND
GEORGE C. SUTTON, M.D.,
WILLIAM P. SWSHEK, M.D., .mm DON C. SCYTTON,M.D.
with organic cardiac disease metabolize I NDIVIDUALS oxygen in performing an amount of physical work than
a larger amount of do normal persons. ‘4 disproportionate increase in oxygen consumption occurs during the period immediately foIIowing the cessation of work, resulting in a slower than normal return to the initia1 rate of oxygen consumption. Measurement of this oxygen debt following standardized work has been utilized as an objective measurement of cardiac functional capacity by NyIin,l by Katz and associates,z and others.X,ks5 The Nylin staircase test has found broad acceptance due to the ease of walking stairs as a standardized work and, especiaIl>. in Scandinavia, a large amount of clinical investigation stands behind this test. IJtilization of the test at (‘(~01; (.ounty Hospital has brought forward a greater variation in the response of human beings to the procedure than was generally recognized. Accordingl> an investigation was undertaken of the reliability and variability of the test in reference to standards published by XyIin.
The function test was performed according to the criteria of Xylin. :\ standard staircase 1 M. high, having six steps, was employed in such a fashion that the individual being examined waIked up and down it in a circular fashion. The low-output test, waIking five rounds (cIimbing up and down the 1 M. staircase ten times) at a rate of 8.5 steps per minute, and the middIe-output test, waIking five rounds at 160 steps per minute, were analyzed. Oxygen consumption was determined at rest and then between the second and fifth minute after the cessation of the work. A Benedict-Roth type machine, manufactured h!, The Sanborn Company, was employed. The increase in oxygen consumption after cessation of work was calculated as a percentage of the resting vaIues. Two methods of anaIysis were employed. Single tests were first performed on a group of individuaIs with normal cardiovascular systems. Eighteen normal men, mean age 37.3 years, performed the .5/‘85 test, while fourteen normal men* Frmn Treble! Laboratory, Cook County Hospital, Chicago, Ill. Aided by a grant from Mrs. Albert Emtire. Rweiwd for publicat,ion March 13, 19.56. 171
and
Nort,hwestern
Clniversity
Ltedical
8rlmol~
172
SUTTON,
SWISHER,
AND
Am. Heart J. February, 1957
SUTTON
mean age 32.4 years, performed the 5/160 test. The minimum, maximum, and mean increases in oxygen consumption were obtained, and the standard deviation and error were calculated for the mean. Secondly the consistency of the tests in a single person was examined. In a group of twelve normal individuals and persons with cardiac disease, stable by all other criteria, the S/85 test was performed two or three times at intervals of a few days by each individual for a total of 31 tests. The .5/160 test was also done at least twice by each of a group of six persons, a total of 16 tests. In this case the minimum, maximum, and mean variations observed in the respective individuals were obtained. RESULTS
AND
DISCUSSION
The results are summarized in Tables I and II. In single tests performed by normal men the per cent of increase in oxygen consumption after the S/8.5 test ranged from 0 to 59 per cent (mean = 29, S. D. = * 17), after the 5/160 test they ranged from 15 to 89 per cent (mean = 55, S. D. = * 26.9). The mean figures are remarkedly similar to those arrived at by Nylin many years ago and which are still employed by him, mainly; the highest normal value for the relative &debit for the 5/85 test was 30 per cent, for the 5/160 test was 75 per cent. It deserves emphasis that this range for normal persons is much greater than that published by North American observers (Sutton, F. C.4 : 5/80 test-mean = 19 per cent and 5/160 test-mean = 30 per cent; also Sodeman3: loo-step rate = + 31 per cent, 200-step rate = + 41 per cent). The statistical analysis of the present figures illustrates the great range of normalcy and contriKnowledge of the standard deviation butes the first such analysis presented. and error of the mean were essential to compare groups of individuals on whom the tests were performed. The unpublished statistical values employed by Nylin for the 5/80 test are: e(M) = 3.47.6 TABLE
I.
RANGEINTHERESPONSEOF~ORMALMAL~;INDIVIDUALSTOTHENYLINHEA~TFUNCTION TEST. RESULTS OFSINGLETESTS PERFOKMEDONA GROUP OF INDIVIDUALS
GROUP
Test 10180 lo/l60
OF INDIVIDUALS
Number Individuals 18 14
of
RELATIVEOXYGENDEBTIN
Mean Age (Years) 37.3 32.4
Min.
Max.
1:
59 89
Mean
2
PERCENT
S. D.
e OfI
*17 d26.9
k4.1 h7.8
While the above illustrated the range within which comparison of group response to the oxygen debt test will be found, no other figures were available for the reliability of the test in a single individual. In the course of other experiments it was found that individual responses were widely variable. As seen in Table II, the oxygen debt seen in one individual in the same clinical status subjected to repeated daily testing varied day by day by as little as 2 per cent and by as much as 53 per cent. For the group of eighteen studies the results of daily
'GABLE
II.
~ARIATI~NINTHE SUBJECTEDTOTHENYLIN
GROUP
Test 10/80 lo/t60
Number , Individuals I ~
12 6
KE~P~NSEOF NORM~~L ~'ERSONS~~XD CARDIAC INVALIDS KEPMTI~~I~Y KESULTSOF REPEATED DA11"y HEARTFUNCTION~~EST. 'I~STINGOFAGROUP~F I~DIVIIK~~LS
OF INDIVIDUALS of
Mean Age (Years) S3.8 37.3
tests differed in the mean individual by about 26 per cent increase in oxyge11 debt for both the lo/SO and lo/l60 tests. This variation in individual response to the test was so great that the procedure lost value as a method of following This spontaneous variation may b( the course of any single cardiac patient. due to the fact that the cardiac patient is so limited by his dyspnea, to a varying degree, that insufficient and different amounts of muscular activity cati be (1011tx without causing the same amount of oxygen debt. It should be added th. Sodeman:j: the test is slow and time consuming; overlapping between normal persons and patielits with heart disease is considerable; and it is a measure of pulmonar!. as ~~11 2~5 cardiac function. 1. The Nylin staircase cardiac function test was performed repeatedI!, on normal individuals and on a group of cardiac patients. 2. Results and statistical characteristics indicate that the mean figtIres obtained from a group of persons studied had wicle variations, but could 1~ satisfactorily compared. 3. The spontaneous daily variation seen in the response of an indivi(lu;~I to the test is of such a magnitude that the test was not satisfactory to follow ~1 single individual’s cardiac status. REFERENC'ES la. lb. lc. 2. 3. 4. 5. 6.
Nylin, NyIin, Nylin, Katz,
G.: Acta Med. scandinav. (Suppl.)93:1-24, 1938. G.: Arch. Inst. Cardiot. Mbxico 17:243, 1947. G.: J. A. M. A. lw:l933, 1937. L. N., Soskin, S., Schutz, W. J., Ackerman, LV., and Plaut, J. L.: Arch. tnt, 53:710, 1934. Sodeman, W. A.: PathoIogical Physiology, Philadelphia, 1950, W. B. Saunders Company. Sutton, F. C., Britton, J. A., and Carr, J. G.: ‘4~. HEART J. 20:423, 1940. Meakins, J., and Long, C. N. H.: J. Clin. Invest. 4:273, 1927. Nylin, G.: Personal communication.
Med.
PERSONS HEART
.4ND
GEORGE C. SUTTON, M.D.,
WILLIAM P. SWSHEK, M.D., .mm DON C. SCYTTON,M.D.
with organic cardiac disease metabolize I NDIVIDUALS oxygen in performing an amount of physical work than
a larger amount of do normal persons. ‘4 disproportionate increase in oxygen consumption occurs during the period immediately foIIowing the cessation of work, resulting in a slower than normal return to the initia1 rate of oxygen consumption. Measurement of this oxygen debt following standardized work has been utilized as an objective measurement of cardiac functional capacity by NyIin,l by Katz and associates,z and others.X,ks5 The Nylin staircase test has found broad acceptance due to the ease of walking stairs as a standardized work and, especiaIl>. in Scandinavia, a large amount of clinical investigation stands behind this test. IJtilization of the test at (‘(~01; (.ounty Hospital has brought forward a greater variation in the response of human beings to the procedure than was generally recognized. Accordingl> an investigation was undertaken of the reliability and variability of the test in reference to standards published by XyIin.
The function test was performed according to the criteria of Xylin. :\ standard staircase 1 M. high, having six steps, was employed in such a fashion that the individual being examined waIked up and down it in a circular fashion. The low-output test, waIking five rounds (cIimbing up and down the 1 M. staircase ten times) at a rate of 8.5 steps per minute, and the middIe-output test, waIking five rounds at 160 steps per minute, were analyzed. Oxygen consumption was determined at rest and then between the second and fifth minute after the cessation of the work. A Benedict-Roth type machine, manufactured h!, The Sanborn Company, was employed. The increase in oxygen consumption after cessation of work was calculated as a percentage of the resting vaIues. Two methods of anaIysis were employed. Single tests were first performed on a group of individuaIs with normal cardiovascular systems. Eighteen normal men, mean age 37.3 years, performed the .5/‘85 test, while fourteen normal men* Frmn Treble! Laboratory, Cook County Hospital, Chicago, Ill. Aided by a grant from Mrs. Albert Emtire. Rweiwd for publicat,ion March 13, 19.56. 171
and
Nort,hwestern
Clniversity
Ltedical
8rlmol~
172
SUTTON,
SWISHER,
AND
Am. Heart J. February, 1957
SUTTON
mean age 32.4 years, performed the 5/160 test. The minimum, maximum, and mean increases in oxygen consumption were obtained, and the standard deviation and error were calculated for the mean. Secondly the consistency of the tests in a single person was examined. In a group of twelve normal individuals and persons with cardiac disease, stable by all other criteria, the S/85 test was performed two or three times at intervals of a few days by each individual for a total of 31 tests. The .5/160 test was also done at least twice by each of a group of six persons, a total of 16 tests. In this case the minimum, maximum, and mean variations observed in the respective individuals were obtained. RESULTS
AND
DISCUSSION
The results are summarized in Tables I and II. In single tests performed by normal men the per cent of increase in oxygen consumption after the S/8.5 test ranged from 0 to 59 per cent (mean = 29, S. D. = * 17), after the 5/160 test they ranged from 15 to 89 per cent (mean = 55, S. D. = * 26.9). The mean figures are remarkedly similar to those arrived at by Nylin many years ago and which are still employed by him, mainly; the highest normal value for the relative &debit for the 5/85 test was 30 per cent, for the 5/160 test was 75 per cent. It deserves emphasis that this range for normal persons is much greater than that published by North American observers (Sutton, F. C.4 : 5/80 test-mean = 19 per cent and 5/160 test-mean = 30 per cent; also Sodeman3: loo-step rate = + 31 per cent, 200-step rate = + 41 per cent). The statistical analysis of the present figures illustrates the great range of normalcy and contriKnowledge of the standard deviation butes the first such analysis presented. and error of the mean were essential to compare groups of individuals on whom the tests were performed. The unpublished statistical values employed by Nylin for the 5/80 test are: e(M) = 3.47.6 TABLE
I.
RANGEINTHERESPONSEOF~ORMALMAL~;INDIVIDUALSTOTHENYLINHEA~TFUNCTION TEST. RESULTS OFSINGLETESTS PERFOKMEDONA GROUP OF INDIVIDUALS
GROUP
Test 10180 lo/l60
OF INDIVIDUALS
Number Individuals 18 14
of
RELATIVEOXYGENDEBTIN
Mean Age (Years) 37.3 32.4
Min.
Max.
1:
59 89
Mean
2
PERCENT
S. D.
e OfI
*17 d26.9
k4.1 h7.8
While the above illustrated the range within which comparison of group response to the oxygen debt test will be found, no other figures were available for the reliability of the test in a single individual. In the course of other experiments it was found that individual responses were widely variable. As seen in Table II, the oxygen debt seen in one individual in the same clinical status subjected to repeated daily testing varied day by day by as little as 2 per cent and by as much as 53 per cent. For the group of eighteen studies the results of daily
'GABLE
II.
~ARIATI~NINTHE SUBJECTEDTOTHENYLIN
GROUP
Test 10/80 lo/t60
Number , Individuals I ~
12 6
KE~P~NSEOF NORM~~L ~'ERSONS~~XD CARDIAC INVALIDS KEPMTI~~I~Y KESULTSOF REPEATED DA11"y HEARTFUNCTION~~EST. 'I~STINGOFAGROUP~F I~DIVIIK~~LS
OF INDIVIDUALS of
Mean Age (Years) S3.8 37.3
tests differed in the mean individual by about 26 per cent increase in oxyge11 debt for both the lo/SO and lo/l60 tests. This variation in individual response to the test was so great that the procedure lost value as a method of following This spontaneous variation may b( the course of any single cardiac patient. due to the fact that the cardiac patient is so limited by his dyspnea, to a varying degree, that insufficient and different amounts of muscular activity cati be (1011tx without causing the same amount of oxygen debt. It should be added th
Nylin, NyIin, Nylin, Katz,
G.: Acta Med. scandinav. (Suppl.)93:1-24, 1938. G.: Arch. Inst. Cardiot. Mbxico 17:243, 1947. G.: J. A. M. A. lw:l933, 1937. L. N., Soskin, S., Schutz, W. J., Ackerman, LV., and Plaut, J. L.: Arch. tnt, 53:710, 1934. Sodeman, W. A.: PathoIogical Physiology, Philadelphia, 1950, W. B. Saunders Company. Sutton, F. C., Britton, J. A., and Carr, J. G.: ‘4~. HEART J. 20:423, 1940. Meakins, J., and Long, C. N. H.: J. Clin. Invest. 4:273, 1927. Nylin, G.: Personal communication.
Med.