Exercise studies with elderly volunteers

Age and Ageing,  May, 1994  by C.A. Greig,  A. Young,  D.A. Skelton,  E. Pippet,  F.M.M. Butler,  S.M. Mahmud

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Subjects often experience problems wearing a mouthpiece and this had led to tests being stopped prematurely. We do not know why our elderly subjects find the mouthpiece so difficult. It is not simply a question of whether or not they have false teeth, although these can add to the problem. Presumably the discomfort results from both reduced elasticity of oral soft-tissues and gingival recession. In an attempt to resolve this, the most difficult aspect of cardiopulmonary testing in this age group, time is given before the test to practise inserting a spare mouthpiece, not connected to the gas analysers.

Safety: Treadmill tests require two investigators, and for the first test we require one to be medically qualified. All non-medical investigators receive instruction and 3-monthly updating in cardiopulmonary resuscitation (CPR) from the hospital's Resuscitation Officer. The laboratory is equipped with a semi-automatic defibrillator and is clearly signposted for the hospital's cardiac arrest team. The treadmill (P. K. Morgan) has an overhead gantry, front and side-rails. The volunteer performs the test wearing a harness attached to a trip switch on the gantry.

The subject's resting blood pressure and 12-lead electrocardiogram (ECG) are recorded. Then, after explanation, demonstration and familiarization, they perform their first submaximal progressive exercise test, without a mouthpiece and following the conventional Naughton protocol (17). The ECG is monitored continuously and blood pressure is measured during each 3-minute stage. The test is halted if (i) the subject requests it, (ii) the ECG shows [greater than or equal to] 0.2 mV of ST depression or elevation, coupled ventricular extrasystoles, [greater than or equal to] 10 ventricular extrasystoles per minute, extrasystoles approaching R on T, (iii) blood pressure fails to rise with increasing work rate, or (iv) the subject develops pallor with sweating, chest pain, undue breathlessness or other evidence of intolerance of exercise. ECG monitoring is also used throughout all subsequent progressive treadmill tests. Of a total of 58 such tests, only one has been stopped, owing to the subject developing an increasing number of ventricular ectopic beats.

Choice of test protocol: It seemed unwise to use truly maximal exercise tests until we had acquired substantial experience in exercise testing elderly people. To date, therefore, we have used a protocol in which the test is stopped when the subject reaches 70% of their predicted maximum heart-rate, calculated as 70% of (210 -- 0.65 x age in years) (18). The first test usually follows the conventional Naughton protocol (17). Thereafter, a suitable protocol must strike a compromise among the following three conditions: (1) The protocol must be such that, despite a rather low maximum work rate, the elderly person can complete a sufficient number of stages adequately to characterize their response to submaximal exercise, in particular the relationship of heart rate and ventilation to oxygen intake. (2) Since the majority of elderly volunteers experience difficulty wearing a mouthpiece, the total duration of the test must be kept to a minimum. (3) Each stage should be long enough to allow achievement of a 'steady-state' condition with respect to the variable of greatest interest. Our current protocols (Tables VI and VII) were based on the Naughton protocol with these three criteria in mind. (The increments in work rate are sufficiently small for the heart rate not to differ between the first and fourth 15s periods of the second minute of each 2-minute stage.) Occasionally, however, further modification may be necessary for individual subjects. With these protocols, repeated tests with healthy elderly subjects (four women and three men, mean age 76, range 73-80) gave reproducible results for heart rate interpolated to oxygen consumptions of 10 and 15 ml[multiplied by][kg.sup.-1][multiplied by][min.sup.-1], viz. coefficients of variation of 4.4% and 6.6%, respectively. The slope of the heart rate versus oxygen consumption relationship was less securely identified (coefficient of variation = 22%).