As the blood pressure is an important factor such determinations were made a part of the regular clinical examinations by Dr. H. W. Goodall when the men came to Boston for the experiments in the group respiration chamber. Standard technique was used, namely, the apparatus of the Taylor Instrument Company (Tycos) and the auscultatory method for both systolic and diastolic pressures. The particular instrument employed had the usual Bourdon gage. This was frequently compared with a mercury manometer to insure the accuracy of the blood-pressure records. The blood pressures recorded by Dr. Goodall were always taken with the subject in the sitting position and with the cuff on the left arm. These determinations were almost invariably made between 8 and -10 p. m., before the subjects entered the respiration chamber.

In the latter part of the research, a series of blood-pressure tests was made with a second instrument by one of us and by the skilled superintendent of the Huntington Memorial Hospital, Miss Anna L. Gibson. This instrument (a duplicate of the one used by Dr. Goodall) was likewise compared with a mercury manometer and its accuracy established. We have every confidence, therefore, in the two instruments used. Special emphasis is laid upon this fact, for the astounding changes in blood pressure render the technique liable to special scrutiny.

The second series of blood-pressure observations included a considerable number of blood pressures which were taken prior to the walking experiments. Successive observations were also recorded immediately after the cessation of walking. The subject was always in the standing position during these determinations, for the first few records, but additional records were made with the subject sitting, usually from 5 to 9 minutes after the walking had ceased. The series of observations after walking provided data for studying the influence of a moderate amount of physical work upon the blood pressure, both systolic and diastolic, and likewise upon the pulse pressure. Such records were deemed significant inasmuch as Cotton, Rapport, and Lewis1 found a pronounced influence upon blood pressure with strenuous muscular work, even when continued only a short time.

Of special interest in this study is the course of the systolic and diastolic blood pressures and the pulse pressure as the investigation progressed. Unfortunately, we were not able to obtain records of blood pressure for Squad A prior to dietetic restriction. The need of such data is specially brought out in examining the blood pressures of the 12 members of Squad B. With Squad A the blood pressure was measured first on October 13; the subjects had therefore been upon a reduced diet for 9 days prior to the first measurement.

1 Cotton. Rapport, and Lewis. Heart. 1017, 6. p. 269.

Systolic And Diastolic Blood Pressure. Squad A

The records of the systolic and diastolic pressures and pulse pressure obtained between October 13 and February 2, inclusive, for Squad A are given in table 76. A glance at this table shows instantly that the blood pressure, both systolic and diastolic, greatly decreased as the diet period continued. The highest values for the systolic pressure were always found in the initial observation. In the majority of instances the highest values for diastolic pressure were likewise obtained at that time but some of the later records show a slight rise. The highest systolic pressure recorded, 140 mm., is that for Kon on October 27, 1917. It will be recalled that this subject had not then been subjected to a restriction in the diet, and hence this value represents for him a normal, unaffected blood pressure. A very striking fall in his blood pressure took place in the 2 weeks between the records of October 27 and November 10; that is, the systolic blood pressure fell from 140 mm. to 110 mm.

Table 76. - Blood-Pressure Measurements During Period Of Reduced Diet - Squad A

1 All blood-pressure measurements were taken with the Tycos sphygmomanometer with the subject sitting.

2 Blood-pressure measurements were obtained with Fre on Oct. 13, as follows: Systolic, 110; diastolic, 80; pulse pressure, 30. .

3The averages for Oct. 27, omitting Ron's values, are as follows: Systolic, 100; diastolic, 72; pulse pressure, 28.

Considering first the systolic pressures, the difference between the initial record and the absolute minimum found during the experiment is as follows: Bro, 25 mm.; Can, 28 mm.; Kon, 50 mm.; Gar, 30 mm.; Gul, 38 mm.; Mon, 25 mm.; Moy, 30 mm.; Pea, 10 mm.; Pec, 30 mm.; Spe, 26 mm. (last observation December 8); Tom, 40 mm.; and Vea, 28 mm. If one uses the record at the end of the observations, these differences become somewhat smaller with all but Bro, Pea, and Spe. In other words, we note, roughly speaking, an average fall of 20 mm. systolic blood pressure from October 13 until the end of the experiment. We have every reason to believe that the blood pressure fell perceptibly in the 9 days between the beginning of the reduction in diet and October 13, so this 20 mm. represents a distinctly minimum value.

The average systolic pressures for all of the men are given in the last column of table 76. The irregularity in number of subjects, i. e., 11 on the first and the last four dates, and 12 on the other dates, affects the averages but little. The high values for Kon on October 27 raise the averages for the three pressures about 3 mm.; the averages for that date without Kon are therefore given in a footnote. The maximum average systolic blood pressure is 115 mm. on October 13, while the minimum average is recorded for both December 8 and 19, i. e., 89 mm., this being a total average fall of 26 mm.

The diastolic pressure likewise decreased profoundly, the initial and minimum values being as follows: Bro, 90 and 65 mm.; Can, 100 and 65 mm.; Kon, 90 and 65 mm.; Gar, 75 and 60 mm.; Gul, 75 and 55 mm.; Mon, 80 and 65 mm.; Moy, 70 and 60 mm.; Pea, 70 and 60 mm.; Pec, 85 and 64 mm.; Spe, 88 and 70 mm.; Tom, 80 and 65 mm.; Vea, 80 and 50 mm. In other words, diastolic blood pressures as low as 60 mm. appear with 5 of our subjects; all of the subjects except Spe show at some time during the experiment diastolic blood pressures of 65 mm. or less.

The average diastolic pressures, which are also subject to the slight irregularities of averaging noted for the systolic pressures, show a maximum of 81 mm. on October 13 and a minimum of 63 mm. on January 26, a total fall of 18 mm. It is important to note that the average values for 11 men on January 26 and February 2 are 63 and 64 mm., respectively.