Shortterm Physical Training in Patients with Rheumatic Heart Disease

Shortterm Physical Training in Patients with Rheumatic Heart Disease ]. Howland Auchincloss, ]r., M.D.• and Robert Gilbert, M.D.•

Seven women with rheumatic heart disease, ages 30 to 57, were hospitalized for 11 to 18 days during which time repeated testing and efforts at physical train· ing were made. All testing was performed with a continuously progressive treadmill test; oxygen uptake (VO:!) was measured with an unsteady state technique previously described. A significant increase in endurance after training occurred in two patients; in one this was accompanied by higher oxygen uptake and heart rate (HR). In one of the five patients who was not significantly improved by training. higher HR values at the limit of endurance were associated with lower values of V0.2. Similar differences in response could be demonstrated within, as well as between, sessions; thus, repeated testing in different patients might im· prove or worsen the relationship between VO:! and HR. Two test sessions on different days sufficed to demonstrate a vo2 value for any subject within 200 ml/min of the highest achieved during the entire series. Therefore, two weeks of physical training, which was difficult to achieve, was of comparatively little value in increasing vo2 values at the limit of endurance.

The effects of physical training in rheumatic heart disease ( RHD ) have, to our knowledge, not been systematically studied, although there has been speculation that it may be beneficial. 1 The present study originated from two considerations: ( 1) physical training might increase exercise tolerance and thereby benefit the patient; and ( 2) physical training might improve test scores obtained in evaluation procedures used in estimating benefit from valvular heart surgery. The present study was exploratory and therefore cautious. Subjects were hospitalized so that possible adverse effects could be promptly treated. Although the facilities of a Clinical Research Center were available, patient acceptance of hospitalization was Professor of Medicine, State University of New York, Upstate Medical Center, Syracuse. This study was supported, in part, by Public Health Service Research Career Development Award 1-K3-HE-19414 from the National Heart Institute ( R. Gilbert), and Public Health Service Grant H-2800 from the National Heart Institute. This work was also supported in part by the division of Research Facilities and Resources of the National Institutes of Health through Grant FR-00353. Manuscript received November 1, 1972; revision accepted February 1, 1973. Reprint requests: Dr. Auchincloss, Upstate Medical Center, Syracuse, New York 13210 0

CHEST, VOL. 64, NO. 2, AUGUST, 1973

not enthusiastic; as a result, the duration of the program for each patient lasted only two weeks. Saltin et al2 demonstrated that the effects of 20 days of bed rest on maximum oxygen uptake ( vo2 max ) in three unconditioned normal subjects could be corrected within this period. It seemed possible that the life style of patients with RHD might cause a similar deconditioning effect. From the standpoint of cardiac surgery, a two-week program in the hospital would probably represent the longest feasible period for a baseline study in any situation other than a research program. It was decided that a progressive test in which endurance, heart rate ( HR) and oxygen uptake (V02) were measured would have a number of advantages: ( 1) all subjects would perform the same test at all stages of evaluation; ( 2) the measurements would, collectively, provide the desired data regarding benefit from physical training without recourse to invasive techniques; and ( 3) the test itself might, if repeated often enough, enhance any other efforts to improve physical performance. The subjects underwent training sessions and testing sessions; both types of exercise might improve

163

164

AUCHINCLOSS, GILBERT

physical performance. However, in a preliminary study such as this it was considered unnecessary to identify the relative contributions of training and testing to improve performance; rather, the essential question was whether the two in combination would have any demonstrable effect. The same considerations resulted in the absence of a control series. Such a series would have consisted of a comparable group of patients hospitalized for the same period and evaluated by the same techniques. The difficulties would have been not only technical but also ethical, since, according to selection criteria, there would be no indication on usual medical grounds for hospitalization and no prospect for improvement. MATERIALS AND METHODS

Seven women with RHD were studied. In all instances diagnosis was confirmed by cardiac catheterization. The essential data of the patients and of a part of the study are given in Table 1. One extra patient with mitral stenosis was also studied because she had previously undergone determination of maximum oxygen uptake.:! She did not undergo physical training and therefore is not included in Table 1. Changes in medication during the study were limited to those believed to be absolutely essential. Only cases 1 and 7 had changes in cardiac drugs; these were the most advanced and unstable cases. The average change in body weight for all seven cases during the study was -0.3 kg with extremes of + 1.2 kg (gain) to -2.2 kg (loss). YO~ in the unsteady state was determined with one of two

circuits and analytical systems developed in this laboratory.3.4 With either of these circuits V0 2 could be estimated at any time, either by direct observation of the oscillographic tracing or by calculation from recorded values of ventilation and mixed expired gas concentration. For each patient the same circuit was used throughout the study. A single exception was the study of Case 1 (Fig 1) in which the newer circuit was used after operation; the older circuit had been used in the determinations before operation. All patients walked on the treadmill to the limit of endurance, with YO:~ and HR measured continuously. Values of YO:~ reported represent the values obtained at the limit of endurance for the test, with the exception of those values discussed in relation to accuracy of measurements and changes in efficiency; these are discussed separately. Patients could signify that the limit of endurance had been achieved by grasping the handrails. Unsteadiness of gait or any other disturbing feature of the patient's appearance was considered also as the basis for immediate discontinuation of the test. YO~ at any of these times is referred to as "Y0 2 BP," in which BP breaking point. Heart rate was continuously measured from the ECG during the tests by a cardiotachometer with an internal calibration system. The exercise procedure for testing had been under development for two years before the study began. A continuous, progressively increasing work load was imposed by having all subjects walk at 2 mph ( 3.2 kph) on a treadmill, with the incline raised continuously at the rate of 6 percent per minute. The treadmill was flat at the onset of the test, and both the hoist and belt motors were activated simultaneously. Since in engineering terminology a continuously increasing function is often referred to as a "ramp function" and since

=

Table I --Clinical and Phy•iolo«ic Data of RHD Patienta Under6oin6 Phy•ical Training

yo, yo, !Patient], Case No.

Age

Diagnosis, Class, Rhythm

Previous History of Heart Failure

YO.,

~().,Max.

Highest

Pred.

~().,

Highest/

Highest Minus

vo.,

1st Test

Highest Minus

YO.

Highest 1st 2 Sessiona

Number of Days PT

Average Endurance Minutes Day Day No. 1-4 No. 11-17

30

MS,TR,III AF,SR*

yes

600

38

0

0

4

1.79

2.38

2

44

MR,EH,II SR

no

1500

100

500

160

7

3.18

4.00

3

51

AS,AR,MP,III AF

yes

1250

96

180

180

9

2.89

3.44

49

AS,AR,MR,TR,III SR

yes

1275

85

245

0

8

2.16

2.28

5

54

AS,AR,MS,MR,III AF

yes

850

65

290

0

8

1.26

1.75

6

38

MS,AR,II SR

no

1442

90

0

0

7

3.36

3.67

7

57

MS ,MR,AS, TR,III AF

yes

1025

79

228

0

8

!.58

1.75

MS=mitral stenosis. TR=tricuspid regurgitation. MR=mitral regurgitation. AR=aortic regurgitation. AS=aortic stenosis. EH=essential hypertension MP= mitral prosthesis. Roman numerals refer to class according to American Heart Association. AF= atrial fibrillation. SR= sinus rhythm. •- rhythm following cardiac surgery. VO., max pred= maximum oxygen uptake predicted from Astrand "fair" series.8 VO., highest= highest single value of VO., BP in entire series. Day no. refers to day following admission to hospital. PT= physical training in Dept. of Rehabilitation. Endurance-duration of test limited by breaking point.

CHEST, VOL. 64, NO. 2, AUGUST, 1973

SHORTTERM PHYSICAL TRAINING IN RHEUMATIC HEART DISEASE the continuous increase in work load distinguished it from the more usual "multistage test,"5 the term "RF" is used to describe it. The test continued for four minutes, at which time a grade of 24 percent had been achieved. Most normal women below 50 years of age can complete the test. Women with moderate or advanced cardiac disease of any age studied in our laboratory have rarely been able to complete it. The test was usually performed without warmup; as the project progressed, more frequent attempts were made to perform two tests at the same session because of the knowledge that a second test might lead to a higher value or, in som!'! cases, demonstrate a lower value attributable to fatigue. In a preliminary series of 11 patients with cardiopulmonary disorders undergoing exercise tolerance testing in which two RF tests were performed and in whom other efforts were made at the same session to achieve V02 max, values of V02 90 percent or more of the highest recorded value of the test session were achieved during the RF test runs in all patients. The detem1ination of V02 max in two of the patients, Case 2 and the extra patient, was reported in a previous study.a Physical training was performed in the Department of Rehabilitation Medicine of the State University Hospital. It consisted of 30-60 minute sessions, once or twice daily, in which the patient walked on a motor-driven treadmill or pedaled a stationary bicycle. No efforts were made to select walking or cycling as the training mode for a given patient; both techniques were used for the sake of variety. The instructors were guided by expressions of fatigue, and sessions were often limited to one per day or omitted at the request of the patient when fatigue from a previous session persisted. No training sessions were held on weekends. Case 1 was studied only by repetition of the previously described RF test; there were no training sessions outside of the laboratory, since a protocol had not at that time been devised. Because of complications apparently resulting from the repeated tests in this patient, the program was interrupted, but she is included because the training effort was made, and because the data obtained were compared to those obtained after cardiac surgery. Patients were admitted for the study to the Adult Clinical Research Center. Usual history and physical examination plus blood count, urinalysis, electrocardiogram and chest radiograph were performed. The latter was repeated at the termination of the study. Exercise testing was performed daily except for weekend interruptions until the training sessions began. Training sessions began on the second to eighth hospital day. For Case 1 there were three laboratory sessions in addition to the sessions in 'which V02 and HR were measured, and for Cases 2 through 7 there were 8-14 sessions in the Department of Rehabilitation Medicine (average, 12). Although the exercise was very mild by ordinary standards, most of the patients felt fatigued as a result of it. One patient, Case 7, was monitored with a portable tape recorder and demonstrated a persistent elevation in heart rate after a training session. The research nature of the study was explained to all of the patients, and their consent in writing obtained. RESULTS

Accuracy of V02 Measurements The accuracy of an unsteady state method for estimation of vo2 cannot be directly estimated unless comparison is limited to apparent steady states or to conditions in which V02 max exists. With the first approach a percent error of 8.4 percent ( SD of CHEST, VOL. 64, NO. 2, AUGUST, 1973

165

differences) was found 6 and with the second approach the comparable figure was 7.9 percent. 4 In the same study the mean difference was 2.1 percent, which was not significant. In the present report we have estimated only the reproducibility of the method, since the two previous studies had failed to show a systematic error. Furthermore, the major concern of the study lies with changes in vo2 obtained with repeated determinations. In order to accomplish this analysis vo2 was calculated for all tests on each subject at the longest time for, which data were available in every test. This value will be referred to as "V02-isotime." This time was actually the duration of the shortest test in each series for a given patient and was therefore different for each patient. In this way differences in V02 due to differences in the endurance of a patient at the time of testing were eliminated. However, differences in efficiency between different tests were not eliminated. Assuming that the accuracy of the measurements in a technical sense was unchanged for each series of values, the estimates of reproducibility by this method would furnish an upper limit for technical errors. The standard deviation ( SD) of V02 at the constant time values was calculated, and 4 SD was taken as the range of variation. This value was 204 ml/min or less in three patients (cases 1, 3 and 4) and was 312-668 ml/min in the remaining four patients. It was concluded that the method was capable of accuracy within 204 ml/ min and that the wider variation in the four patients was probably caused by variations in efficiency; inspection of the data did not suggest that efficiency was changed in a consistent fashion throughout the course of the study; in only one case (Case 4) was there evidence of significant improvement. In this patient the average of V02-isotime was lower after training (days 1117) than before training (days 1-4) by 280 ml/ min.

Adequacy of RF Test as an Estimate of V02 Max In addition to the preliminary series of 11 patients referred to in the methods section in which the vo2 BP by RF test was found to be within 90 percent of the highest V02 of the test session, data on Case 2 and the extra patient were available from a previous study. 3 In these two patients V02 max was determined by the method of Chapman et aF V02 by RF test exceeded these vo2 max values by 81 ml/min in Case 2 and by 210 ml/min in the extra patient. These differences are within the estimate of methodologic variation of 204 ml/ min stated previously and suggest that V02 BP during RF testing may approximate vo2 max when vo2 max is measured by a technique such as that used by Chapman et aF

AUCH I NCLOSS, GILBERT

166

Aerobic Capacity of Patients Predicted values for V02 max were calculated for each patient by use of the data of Astrand 8 on normal subjects, using the lower limit of the "fair" category in her data. The value of highest V02 was obtained during one of the 4-12 tests done in each subject, and 88 percent of the predicted was taken as the lower limit of normal based on an earlier study of 13 normal subjects also stressed to the limit of endurance. 4 In four of seven patients in the present study, the V02 BP obtained at any time during the study was less than 88 percent ( 38-85 percent) of the predicted value of V02 max. In three of these four patients (cases 1, 5 and 7) the highest V02 BP values were 600, 850, and 1025 ml/min, which were clearly subnormal according to our experience as well as according to the predicted values. In Case 4 the value of 1275 ml/ min might represent a value at the lower limit of normal. Effect of Physical Training on Endurance and VOz BP

If endurance (the time between onset of test and voluntary discontinuation) was estimated as the average of tests on hospital days 1-4 and 11-17, all seven patients demonstrated an increase (Table 1). Eighty percent of this increase was demonstrated by the fifth hospital day in four of the seven patients and after the tenth day in the other three. Greatest endurance, however, was achieved on the last day in all cases. Only in cases 2 and 3 was there a significant relationship between hospital day and endurance (Case 2 P < .001; Case 3 P < .003). In these two cases V02 BP was also significantly and positively correlated with hospital day ( P < .05 in both cases). An effect of training on reducing HR at the same vo2 was sought in the calculations made at vo2isotime; in only one (Case 6) was there a reduction of HR at the same V02 after training. Relation between V02 BP and HR BP Further analysis of the data in cases 2 and 3 demonstrated that in Case 2 (but not in Case 3) there was a significant positive linear relationship between V02 BP and HR BP ( P < .01). This is graphically shown in Figure 1. In Case 2, therefore, the training program was associated not only with increase in endurance and V02 BP but also in HR BP. No such clear positive relationship was demonstrated in any of the other six patients. However, a significant negative linear relationship between vo2 BP and HR BP was demonstrated in Case 7, one of the five patients in whom there was failure to dem-

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R•.843

LO

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ISEE•IIt.7 Po<.OI

_j

j

.5

N

·~ 2

3

4

0 60 L5

100

140

180

220 •• 7

~

~ ~

LO

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.5 , /

_j

2

3

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0 60 L5

100

4

0

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LO

2

140

R•.763 ISEE•I8.4

60

100

TIME(min.)

140

180

220

H.R. (beala/min.l

FIGURE 1. (Left) vo2 VS time. ( Right) VO:~ vs HR. Solid squares represent BP values. All data during RF testing (see text ) . Shaded area represents regression ± 1 SEE for BP values. V02 at breaking point positively correlated with HR in Case 2 and negatively correlated in Case 7. Improvement after surgery shown in Case 1 both in V02 vs time and VO:! vs HR.

onstrate a significant increase in endurance. This relationship is also shown in Figure 1. Figure 2 shows the varying effects of the program on cases 2 and 7, demonstrable during individual test sessions as well as by the previous analysis of all the sessions. Thus, in Case 2, test repetition within the same session appeared to increase the vo2 response as a function both of time and HR, while in 1.5 -LO

.: ~

:d.

.I

0~--~--~--~--~ 0 I 2 3 4

TIME(min.l

1.5 R.C.

case•

140

180

7

0~--~--~--~--~

0

100

H.R. (beala/min.l

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TIME (min. I

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0~---:-':-:----''----' 60 100 140 180 H.R. (beats/min)

2. (Left pair) vo:! VS time. (Right pair) VOz VS HR. ( Top ) Case 2. ( Bottom) Case 7. Test repetition at same

FIGURE

sess!on elicits higher V02 and HR in Case 2 but lower values of VO:~ in Case 7. Curve displacement is similar with both VO:~ VS time and vo2 VS HR.

CHEST, VOL. 64, NO. 2, AUGUST, 1973

SHORTTERM PHYSICAL TRAINING IN RHEUMATIC HEART DISEASE

Case 7 test repetition caused a decreased response.

Clinical Effects of the Program Although six patients said that they "felt improved" by the program, the statements were considered uninterpretable, since their questioner was their physician and all patients had been selected on the basis of willingness to cooperate. The other subject, Case 1, developed unmistakable evidence of pulmonary congestion on the third hospital day after two testing sessions. This patient had severe mitral stenosis with right ventricular pressure of 80/9 mm Hg. Testing was resumed on the eighth hospital day, but no regular training program was undertaken.

Value of Retesting in Estimating Value of Highest V02BP The highest individual value of V02 BP was obtained within two sessions in five cases, and in the remaining two cases the highest value of the first two sessions was within 200 ml/ min of the highest value of all sessions (Table 1). It is of interest that in these two patients (cases 2 and 3), who were the only two in whom statistically significant relationships were obtained between endurance and hospital day, such a close approximation of the highest V02 BP was obtained so early in the test series. In Case 2 (Fig 1 ) a definite increase in endurance, V02 BP and HR BP occurred on the second test, which was performed after a weekend of rest in the hospital.

Program as a Means of Assessing Benefit from Surgery Patient 1, following the negative experience with physical conditioning, underwent mitral valvuloplasty under cardiopulmonary bypass. The curves in Figure 1 demonstrate that V02 BP was higher after surgery, both with respect to time arid heart rate; this was the case no matter which of the studies was used for comparison before operation. The patient was in atrial fibrillation before surgery and in sinus rhythm at the time of the study after operation. DISCUSSION

Despite the small number of patients studied, the short duration of physical training and the differences in response to repeated testing and physical training, the study does provide information relevant to the two possibilities stated in the first paragraph of this report. The first possibility was that physical training might increase exercise tolerance. Some increase in exercise tolerance was achieved in all seven patients, CHEST, VOL. 64, NO. 2, AUGUST, 1973

167

and in two the increases were statistically significant. In one of these two (Case 2) endurance increased from less than three minutes to four minutes. An increase in endurance of this magnitude in a progressive test is of greater significance than in a test at a fixed work load, because the work requirement is increasing during the extra period and is therefore greater than any work load experienced in the first test. Calculations of vertical height traveled during the early period (days 1-4) and later period (days 11-17) indicated that in the later period five of the seven women ascended the equivalent of one or more Bights of stairs above and beyond the height achieved at the breaking point during days 1-4. There is no reason to believe that this increased ability to lift their weight against gravity could not have been realized in ordinary daily living. From the data in these patients, especially cases 2 and 3 one can reasonably conclude that endurance can be increased in some patients with valvular heart disease in as short a period as two weeks. This increase in endurance was not reflected, as a rule, either in increased efficiency (lower vo2 at same task) or in increased physical fitness (lower HR at same V02). It can therefore be considered to represent increased "tolerance" for work due either to improved motivation or to greater familiarity with the test procedure. There was no indication that motivation changed in so short a period. Therefore, familiarity with the exercise test would appear to be the most logical explanation for the increased tolerance. Davies et al, 9 in a study of five healthy men subjects, demonstrated an 8 percent improvement in vo2 max which was statistically significant after 16 days of exercise over a three-week period. Saltin et aJ2 found that in their three previously untrained subjects the reductions in vo2 max caused by 20 days of bed rest were eliminated within about ten days following institution of a training program. These observations on short-term physical training programs supplement the more numerous data regarding the effects of prolonged physical training in middle-aged sedentary men, 10 patients with coronary artery disease"·12 and patients with chronic obstructive lung disease. 13 The brief duration of the program leaves unanswered the question of whether or not a longer period of training would have benefited a larger proportion of the group. For this question. to be answered a much greater organizational . effort would be necessary, and it would be desirable to select patients in whom the effort would be safe and productive. The study offers a few clues as to how this problem of selection might be approached. The appearance of pulmonary edema in a patient with tight

168

mitral stenosis during the testing period suggests that such patients should be excluded and accords with clinical experience that they are especially prone to this complication. However, a broader method of selection is suggested from the data provided in Figures 1 and 2. Figure 1 shows that Patient 2, who appeared to benefit from training, possessed a much greater ability to elevate vo2 with increasing values of HR than was true in Patient 1 with the case of mitral stenosis previously discussed. Of greater importance, however, was the contrast in V02-HR relationships between Case 2 and Case 7, also shown in Figure l. Patient 7 was one of the five who did not have a significant increase in endurance from training, and she complained frequently of fatigue during the training period. It was shown in her case that the relationsh:p between V02 BP and HR BP, rather than being positive, as in Case 2, was actually negative. The difference is reflected not only in the breaking point values analyzed but in the values obtained while standing, before the exercise began. There was no evidence of a change in clinical status to explain this difference and thereby suggest a way in which all tests could start from the same values of V02 and HR. The lower V02 BP with a higher value of HR in Case 7 raised the possibility that exercise tachycardia beyond 120 beats per minute might be counterproductive. We were unable to demonstrate a fall in V02 with increased HR during a single test run; presumably, if the vo2 were to fall with continued exercise, the stress would be intolerable and the patient would signal for cessation of the test. The manner in which the negative relationship between V02 BP and HR BP. occurred is shown in Figure 2; test repetition caused a downward displacement of V02 for any value of HR throughout the test run. The usual explanation for such a phenomenon is that the two tests were performed in too rapid a sequence; however, the heart rate at the time of starting the second test, as shown in Figure 2, was only seven beats/min higher than on the first test, and no effort was made to curtail the rest period. Therefore, it does not appear that the tests were repeated in too rapid a sequence. The physiologic basis of such a marked displacement of the curves of vo2 VS HR in Case 7 is not clear, but the displacement appears to us to be greater than that seen in physically unconditioned normal subjects whom we have studied with repeated testing, and it occurred at values of V02 well below one liter/min. We would propose, therefore, that the displacement was related directly to the presence of heart disease and to a reduced response of the cardiac output to exercise rather than by poor physical condition per se. According to

AUCHINCLOSS, GILBERT

this explanation the patient with advanced heart disease is so easily fatigued that relations between V02 and HR will vary on different days and be easily changed by any preceding exercise. A reasonable conclusion from the experience in cases 2 and 7 would be that Patient 2 might benefit from a longer program of training but that Patient 7 was an unpromising candidate unless a considerable amount of care was to be undertaken to avoid excessive work loads. However, the problem of fatigue was also apparent in Case 2, even though the total response of this patient to physical training was the best of the group. Figure 1 shows that curves of V02 varied greatly between the first two sessions, regardless of whether vo2 was plotted against time or against HR. This patient was aware of the improved performance between the two sessions and believed that it was explained by a restful weekend in the hospital where she was free of the pressures of family life. Separate information from a social worker who visited her home prior to the admission was corroborating; the patient had assumed responsibility for the care of a household in which there were numerous children and performed many of the chores herself. From these experiences we conclude that rest is as important as physical training in determining the physical performance in these patients. In regard to the possibility of future programs, the overall experience with the present effort prompts a few suggestions. Excluding the patient with mitral stenosis (Case 1 ) the highest V02 achieved in the study ranged from 0.85 to 1.5 liters/ min. This would suggest that, in a training program in which the work load was not more than that necessary to achieve 70 percent vo2 max, the desired vo2 would range from about 0.5 to 1.0 liter/min. It seems questionable whether an organized program should be devised in order to achieve such low levels of performance. The patient might be advised to walk to the point of mild fatigue or perhaps to perform five or ten minutes of exercise on a calibrated bicycle ergometer set initially at a very low setting such as zero to 200 kg meters per minute. The expense of such an instrument would be small compared with that of an organized program for a group, and the program could be continued indefinitely. Redwood et aP 4 in a recent study of physical training in coronary artery disease recommended bicycle exercise for their subjects following completion of a sixweek hospital program. While the study provides only tentative and preliminary evidence of the value of physical training for women with RHD and tends, as we have discussed, to emphasize difficulties rather than benefits, CHEST, VOL. 64, NO. 2, AUGUST, 1973

169

SHORTTERM PHYSICAL TRAINING IN RHEUMATIC HEART DISEASE

it provides a fairly satisfactory answer to the second hypothesis: physical training might improve test scores used in estimating benefit from valvular heart surgery. The data in Table 1 show that if the results of the first two test sessions were taken, the vo2 value obtained was within 200 ml/ min of the highest value obtained in the test series. This was true regardless of whether or not the total program produced an increase of V02 BP. If V02 BP values are considered approximate values of vo2 max, the conclusion is reasonable that vo2 max can be estimated within 200 ml/ min in two test sessions using the RF test in which the patient with RHD walks until she experiences a definite desire to stop. The approximate equality of V02 BP with V02 max during this specific ( RF) test was actually demonstrated in Case 2 and one other patient (the extra patient), both of whose data are included in the results section. The use of the patient's symptoms as an indication that vo2 max has been achieved appears at first to expose the measurement to the likelihood of gross underestimation. However, Detry and Bruce 12 have also used the same concept, designating the value "V02 max SL" in which SL refers to symptom limitation. They found it a useful index of improvement in judging the effect of physical training in patients with coronary artery disease. In a study designed to investigate this problem Auchincloss et al 4 found that the average value of vo2 derived from a completed two-minute run at fixed settings and a BP run at a higher setting agreed within 2.9 percent (group average) with vo2 max computed from two runs in which "leveling off" of vo2 occurred and calculations were made from timed collections of expired air. Neither the results of the present study nor of the previous one just mentioned mean that vo2 max can be estimated from single test runs without further testing. The present study, in particular, suggests that initial determinations may be gross underestimates; such was the finding in Case 2. In addition to fatigue, there are also the problems of motivation and anxiety due to unfamiliarity with the procedure. We conclude that two sessions on different days should be sufficient and would recommend that, if possible, two test runs at each session be performed with a resting period between tests long enough to allow the HR to fall to within ten beats of the previous resting value. This will permit identification of the pattern of fatigue encountered in Case 7 (Fig 2) and should furnish values of V02 approx-. imately equal to those obtained with a two-week program of physical training and frequent retesting. The ability of the RF test to furnish objective

CHEST, VOL. 64, NO. 2, AUGUST, 1973

evidence of improved response of V02 and HR to exercise following corrective surgery is well shown in Figure 1 (Case 1 ) . The interpretation would be unchanged regardless of which of the tests was used :1fter operation. In an earlier study, 3 the effect of successful cardiac surgery on the curve of vo2 versus time was demonstrated in each of the three patients studied. The combination of a higher vo2 both with respect to time and HR suggests improvement in the response of cardiac output. ACKNOWLEDGMENTS: The authors thank Mr. David Peppi, Mrs. Jane Bowman and Mr. Nicholas Gardinier for technical assistance and Mrs. Alice Vogt and ~liss Judy Spaulding for aid in preparation of the manuscript. REFERE:>
2

3 4 5 6 7 8 9 10 11 12 13 14

Rapaport E: Exercise responses in patients with heart failure or valvular or congenital heart disease. J SC Med Assoc (Suppl1, no 12) 65:61-64, 1969 Saltin B, Blomqvist G, Mitchell JH, et al: Response to exercise after bed rest after training: a longitudinal study of adaptive changes in oxygen transport and body composition. Circulation ( Suppl7) 38:1-78, 1968 Auchincloss JH Jr, Gilbert R, Baule GH: Unsteady state measurement of oxygen transfer in patients with rheumatic heart disease. Clin Sci 39:21-37, 1970 Auchincloss JH Jr, Gilbert R, Bowman RP, et al: Determination of maximal oxygen uptake with unsteady-state measurements. J Appl Physiol31:191-197, 1971 McDonough JR, Bruce RA: Maximal exercise testing in assessing cardiovascular function. J SC Med Assoc ( Suppl 1, no 12) 65:26-33, 1969 Auchincloss JH Jr, Gilbert R, Baule GH: Unsteady-state measurement of oxygen transfer during tradmill exercise. J Appl Physiol25:283-293, 1968 Chapman CB, ~1itchell JH, Sproule BJ, et al: The maximum oxygen intake test in patients with predominant mitral stenosis. Circulation 22:4-13, 1960 Astrand I: Aerobic work capacity in men and women with special reference to age. Acta Physiol Scand ( Suppl 169) 49:1-92, 1960 Davies CTM, Tuxworth W, Young JM: Physiological effects of repeated exercise. Clin Sci 39:247-258, 1970 Siegel W, Blomqvist G, Mitchell JH: Effects of a quantitated physical training program on middle-aged sedentary men. Circulation 41:19-29, 1970 Clausen JP, Larsen OA, Trap-Jensen J: Physical training in the management of coronary artery disease. Circulation 40:143-154, 1969 Detry JM, Bruce RA: Effects of physical training on exertional S-T -segment depression in coronary heart disease. Circulation 44:390-396, 1971 Haas A, Cardon H: Rehabilitation in chronic obstructive pulmonary disease. A 5-year study of 252 male patients. Med Clin North Am 53:593-606, 1969 Redwood DR, Rosing DR, Epstein SE: Circulatory and symptomatic effects of physical training in patients with coronary artery disease and angina pectoris. N Eng[ J Med 286:959-965, 1972