Normal pulse-rates for children

One of the most striking indices of apparent changes in metabolic activity, induced either by muscular activity or by febrile conditions, is the pulse-rate. In our earlier treatment of the physiology of normal infants, 1 we laid special emphasis upon the importance of knowing the fluctuations in the activity as exhibited by the kymograph record of the movements of the crib and particularly upon the relationships between this curve for activity and both the pulse-rate and the metabolism.

Before the study of new-born infants, our observations on children were so scattered and represented so few normal subjects that we were unable to record normal pulse-rates for children of various ages. With the new-born infants, however, this was perfectly feasible, and in the report of that study, 2 data were recorded giving the average pulse-rate for the first 8 days after birth as 112 on the first day, and for the 7 subsequent days 114, 116, 116, 116, 122, 119, and 126, respectively. These average values were obtained from a considerable number of counts for different children. Those for the first day after birth represented 50 new-born infants, but on the later days the number of subjects was less, particularly on the seventh and eighth days.

In our report of the observations on the few normal subjects, made in the first study of the gaseous metabolism of infants, 1 we were primarily interested in such alterations in the pulse-rate of an individual infant as were due to changes in activity and not in the alterations due to changes in age. Accordingly, in this earlier study the period of observation did not exceed 30 to 45 days, except with a single infant. In the accumulation of our new data, however, special stress was laid upon the trend of the pulse-rate as the age increased. This could be studied advantageously in those series of observations in which the metabolism of the same child was studied over periods of 4 months or more, and in a few cases 3½ years. Finally, with the older children, the unusually advantageous conditions under which the data were obtained make it seem desirable for us to record the pulse-rates and deduce therefrom average values which might be expected from children under quiet conditions.

Even the earliest observers noted that the pulse-rate of infants was very difficult to obtain and varied under different circumstances. The great difficulties in securing accurate records can perhaps be no better expressed than by quoting from the earliest report that we have found in English of observations on the pulse-rate of children. Publishing in 1694, Walter Harris of London stated:

"But the Pulses of Children are naturally, or upon every little Alteration, do become so swift and frequent, that they always seem somewhat Feverish. Moreover, they are for the most part, so chagreen and froward, that not keeping their Wrest one moment in the same posture, do not suffer their Pulse to be touched. Lastly, there are so many things that do accelerate or otherways change their Pulses, that Sentiments taken thence should prove very uncertain, if not altogether false."

In the interesting book of Benjamin Waterhouse 2 we find a quotation from a paper read in 1768 at the Royal College of Physicians in London by the venerable Dr. Heberden:

"The pulse of children under two years old should be felt when they are asleep; for their pulses are greatly quickened by every new sensation, and the occasions of these are perpetually happening to them while they are awake. The pulse then of a healthy infant asleep on the day of its birth, is between 130 and 140 in one minute; and the mean rate for the first month is 120, for, during this time, the artery often beats as frequently as it does the first day, and I have never found it beat slower than 108. During the first year the limits may be fixed at 108 and 120. For the second year at 90 and 108. For the third year at 80 and 100. The same will very nearly serve for the fourth, fifth, and sixth years. In the seventh year the pulsations will be sometimes so few as 72, though generally more; and therefore, except only that they are more easily quickened by illness, or any other cause, they will differ but little from the healthy pulse of an adult, the range of which is from a little below 60 to a little above 80. It must be remembered, that the pulse becomes more frequent, by ten or twelve in a minute after a full meal."

No further evidence as to the difficulties of making these physiological records is necessary. Perhaps the best confirmation of this evidence is the fact that so little is now known regarding the quiet resting pulse of children. On looking over the literature on the normal pulse-rate of children, it is at once obvious that very little interest has been taken in the subject and few accurate counts have been made which take into consideration all the factors which modify the normal rate of the heart. It has been the custom of practically all writers to report minimum and maximum pulse-rates and to follow what seems to us the very confusing and entirely irrational procedure of averaging these and reporting the result as the average pulse-rate. A summation of our data shows that any pulse-rate above the minimum is profoundly affected by the degree of activity; therefore, little, if any, value can be placed upon observations of pulse-rate other than those obtained with the child in repose. It is of importance to know to what extent maximum pulse may develop during paroxysms of crying and with such activity as a child may exhibit when lying in bed, but for all normal purposes such records have but little, if any, scientific value.

The younger the infant the greater is the difficulty of obtaining the pulse-rate. With older children the element of apprehension should not be entirely disregarded. If this apprehension is not present to any great degree, the special precautions necessary for small children will not be required for the older individuals. Our measurements were all made while the child was inside a hermetically sealed chamber, and the routine was invariable for all children studied.