Introduction of the Blood Pressure Cuff into U.S. Medical Practice: Technology and Skilled Practice

Harvey Cushing in Baltimore

In 1901, while traveling in Europe, U.S. surgeon Harvey Cushing saw a new blood pressure instrument in clinical use at the Ospedale de S. Matteo in Pavia, Italy [1]. The instrument, a version of the modern blood pressure cuff, had been devised by Italian physician Scipione Riva-Rocci a few years earlier [11]. Cushing, stimulated perhaps by his own recent study of cerebral perfusion pressures, solicited a gift of one of the Riva-Rocci cuffs and brought it back with him to Baltimore, where he began to encourage its use among the house officers at Johns Hopkins Hospital [12]. Although other tools existed for estimating the force of blood flow, this new blood pressure cuff attracted the attention of early supporters, such as Theodore Janeway in New York City and George Crile in Cleveland [2, 3]. Cushing himself became an energetic proponent of the cuff. After 2 years' experience on the wards of the hospital, he and two of his surgical house officers, Henry Wireman Cook and John Briggs, set out to promote wider clinical use of the cuff.

All three physicians recognized substantial barriers to their efforts. The introduction of the new cuff challenged the already well-established practice of pulse palpation. Physicians throughout the 19th century had taught that careful palpation of the radial pulse revealed valuable information about the force of blood flow. A standard U.S. medical text on physical examination published in the late 19th century advised the physician to palpate the patient's radial pulse for “the fullness of the vessel … the tension of the artery … the size of the [pulse] wave … the force of the wave … [and] the duration of the wave” [13]. The new blood pressure cuff offered a way to replace this expert, subjective assessment of the pulse with a simple number: systolic blood pressure.

Briggs and Cook showed some wariness about potential conflict with this established practice in their early efforts to promote the new blood pressure cuff. In 1903, they published two papers about blood pressure measurement, each tailored to a different audience. In Maryland Medical Journal, which had a readership of practicing, community-based physicians, Cook and Briggs deferred to the accepted value of expert pulse palpation [14]. They praised “that delicacy of pulse palpation which only years of experience can develop” and acknowledged that “the masterhand of the trained clinician derives information from the pulse that is beyond the reach of the tyro, and can never be obtained mechanically” (that is, by the blood pressure cuff) [14]. They presented their new tool to this particular audience as only a modest accessory to existing clinical practices.

However, in a publication for a different audience, Briggs and Cook presented a different estimate of the relative values of pulse palpation and blood pressure measurement [15]. In their second report, in Johns Hopkins Hospital Reports, Briggs and Cook addressed a readership that was more familiar with the new physiology laboratories of the time and was perhaps more open to innovation in practice. In this report, Briggs and Cook were openly critical of pulse palpation, arguing that the physician's finger on the radial pulse was “the most deceptively and grossly inaccurate of all sphygmomanometers” [15]. Briggs and Cook argued candidly that the new blood pressure cuff should replace an outdated reliance on complex, qualitative judgments about the pulse.

Harvey Cushing in Boston

Harvey Cushing took a more straightforward approach to promoting the new blood pressure cuff. In 1903, he traveled to Boston to speak at Harvard Medical School about the use of the new cuff. He opened his talk in Boston with a passing reference to pulse palpation, asserting his wish not to “disparage the value of an educated touch [on the pulse]” [1]. The crux of Cushing's talk, however, was his favorable comparison between the new cuff and other, familiar tools for objective medical measurement. Nurses, Cushing pointed out, already regularly used the pocket watch and the thermometer to measure pulse rate and body temperature. The cuff could be used to provide similarly standardized, quantitative data. Measuring systolic blood pressure with Riva-Rocci's new cuff required little additional skill beyond the abilities to feel the radial pulse and to read a number on a pressure gauge at the point at which the pulse was obliterated. The new blood pressure cuff, Cushing asserted, filled the need for an instrument “which like the watch and the thermometer enable[d] the nurse or orderly to accumulate data, the interpretation of which remains for the visiting physician” [1].

Cushing's characterization of the new blood pressure cuff was potentially reassuring. He presented the use of the cuff as distinct from expert pulse palpation and perhaps more appropriate for nonphysicians. This characterization, however, led to other concerns. Could a novel medical device be introduced into regular medical practice as a tool of nonphysicians? How would the nurse's measurement of pulse obliteration pressure with the cuff reflect on the physician's practice of assessing the tension, size, force, and duration of the pulse?

The group that heard Cushing's talk in Boston immediately took up the challenge presented by the new blood pressure cuff. A group of surgeons at Harvard Medical School organized a clinical trial, distributing cuffs to three affiliated hospitals-Massachusetts General Hospital, Children's Hospital, and Boston City Hospital [16]. Physicians at the three hospitals were instructed to put the cuff into regular clinical use and to report back to a committee about the value of measuring systolic blood pressure. The group also acted on Cushing's suggestion that the cuff was appropriate for use by different medical personnel. Dr. Fred Murphy at Massachusetts General Hospital had nurses take measurements with the new cuff [17].

When the committee brought together the three reports, the verdict went against the new cuff. The investigators found that the blood pressure cuff did what it was supposed to do. It supplied a ready measurement of the pressure required to obliterate the radial pulse. In most cases, however, they found that the new data on systolic blood pressure could at best only confirm other information already available through the established practices of pulse palpation and physical examination.

In other cases, the new cuff actually provided conflicting information. One physician cited an instance in which an obvious change in the quality of the pulse as assessed by palpation required rapid medical intervention, whereas the blood pressure cuff failed to register any change in the systolic pressure [18]. Such a difference was resolved in favor of the established practice of pulse palpation.

The investigators at Massachusetts General Hospital did find some patients with brain injury in whom the new cuff was helpful. They noted that in some such cases, the pulse rate decreased and the circulatory force of the blood flow increased [17]. The new blood pressure cuff was helpful in documenting this unusual combination of changes, a phenomenon already noted by Cushing and later identified with his name. The Boston committee acknowledged Cushing's expert interest in brain surgery, but they showed little enthusiasm for a tool that challenged their reliance on pulse palpation.

The Success of Auscultation

The new cuff seems never to have gained wide acceptance for use in the manner that Cushing advocated. It did, of course, enter mainstream U.S. medical practice. After it attained more general use a decade later, however, it was frequently used in combination with the new method of auscultation with the stethoscope. It was the method of auscultation, rather than Cushing's method, that seems to have displaced pulse palpation as the standard medical practice for assessing the force of blood flow.

This change was obvious and dramatic in one of Boston's academic medical institutions. At Massachusetts General Hospital, where Cushing's method met with resistance, physicians rapidly integrated the method of auscultation into standard practice. The idiosyncrasies and conservatism of academic medicine in Boston were accepted topics for public speculation at the time [19]. Generalizing from events in Boston has its risks now as it did then. Massachusetts General Hospital however, was well recognized as a major site for establishing and disseminating new medical practices [20]. A sudden change in the use of the blood pressure cuff in Boston may well have had substantial influence.

The general outlines of this same change are evident in the U.S. medical literature of the period. In 1905, physician Nikolai Korotkoff published an outline in Russian of his novel method of auscultation to measure systolic and diastolic blood pressure [21]. Physicians in the United States saw an account of the method in the U.S. medical literature in 1910 [9, 22]; many, however, probably first learned of auscultation from reports in 1909 in the closely followed German medical literature, which was systematically indexed within weeks of publication in the Journal of the American Medical Association [23-25].

After 1910, U.S. physicians steadily simplified their practice of pulse palpation and accepted auscultation of systolic and diastolic blood pressure in its place. In the previous decade, clinical case reports in the Journal of the American Medical Association rarely reported blood pressure but often reported the tension and volume of the palpated pulse in such terms as “soft, full and regular” [26]. Beginning in the 1910s, systolic and diastolic blood pressures began to appear more regularly in clinical case reports and gradually replaced pulse tension and volume as routine data. Practices were inevitably heterogeneous among different hospitals and cities across the United States. Physicians sometimes mixed information about blood pressure and the pulse in novel ways. In 1917, for example, one case report still noted the volume and tension of the pulse but reported the “tension” as the measured blood pressure [27].

The displacement of pulse palpation by auscultation in the medical literature was in some cases rapid and distinct. Richard Cabot wrote a widely used textbook on physical examination that went through several editions during this period. Between the fourth edition in 1909 and the fifth edition in 1913, Cabot radically changed his discussion of pulse palpation with the introduction of auscultation. In the 1909 edition, Cabot included both a lengthy discussion of pulse tension and volume and an explanation of the use of the cuff to measure systolic pulse obliteration pressure [28]. In the 1913 edition, he added a discussion of the new method of auscultation with the blood pressure cuff. At the same time, he substantially shortened his discussion of pulse palpation and completely dismissed his earlier endorsement of pulse palpation for tension or volume. He noted that “this method seems to me so unreliable that it should be abandoned in favor of the instrumental method” [29].

Practice at Massachusetts General Hospital

Actual medical practice may not closely follow changes in the medical literature. In Boston during this period, however, the practice of blood pressure measurement changed remarkably. Nurses and physicians at Massachusetts General Hospital left meticulous records of clinical practice on the wards at this time. Seventy-seven surviving volumes of bound patient records from the hospital dating from 1903 to 1910 demonstrate change in the use of the blood pressure cuff.

Cushing's method of measuring systolic blood pressure by pulse obliteration never attained routine application at the hospital. Twenty patient records, selected from each volume by using random-number sampling, did not mention blood pressure on either the medical or surgical service in the years after his 1903 talk. In contrast, notations on the tactile qualities of the palpated pulse appeared routinely during this period. Notes on the initial physical examination in 1906, for example, might read, “pulses-equal, regular, synchronous, of small volume and low tension” [30]. Page-by-page review of records from 1905 on identified sporadic cases for which systolic blood pressure was recorded, often in the margins of the main medical note. These reports also typically retained information on pulse tension and volume in its usual place in the physical examination. During this same period, despite Cushing's advice, the nurses' records showed regular notations on pulse, respiration, and temperature but not blood pressure.

In 1909-1910, physicians on the medical service changed their use of the blood pressure cuff. Detailed review of all available records from 1906 to 1910 revealed a sharp increase in the use of the cuff in 1909-1910, as shown in the (Figure 1). Blood pressure data simultaneously moved out of the margins of the chart and became integrated into the initial examination for nearly every medical patient. In the rare case in which blood pressure was omitted, the note might read “Bld Press = not obtained” [31]. It was a systematic change in practice.

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Figure 1. White bars represent the absence of any recorded blood pressure in 20 randomly selected medical cases from 1903 to 1905. Striped bars represent the proportion of all medical cases from available records with recorded pressures from 1906 to 1910. The total number of cases reviewed for each year appears above each bar. Measurement of blood pressure on the medical service at Massachusetts General Hospital, 1903 to 1910.

Simultaneously with this large increase in use, physicians also changed their method of using the cuff. This change encompassed the practices of several attending physicians and many house officers, suggesting the establishment of a consensus on blood pressure measurement at the hospital immediately after the appearance of German reports on auscultation in 1909. Before 1909-1910, the medical charts recorded only systolic blood pressures, easily provided by Cushing's method of pulse obliteration. Beginning in 1909-1910, however, both systolic and diastolic blood pressures appeared, paired in the familiar form used today with the method of auscultation. Although the surgeons at the hospital in 1910 continued to record only sporadic systolic blood pressures, they soon adopted the routine use of both systolic and diastolic pressures [32].

The rapid adoption of auscultation also seems to have unseated the practice of pulse palpation at the hospital. Until 1909-1910, sporadic use of the cuff to measure systolic blood pressure coexisted with the routine use of pulse palpation. After 1910, however, attention to the complex qualities of the pulse faded. By 1917, an entire volume of medical cases from the hospital contained no mention of the tension or volume of the pulse [33]. The section of the physician's note in which the qualities of the pulse had been recorded now routinely contained blood pressure data.

Skilled Medical Practice

How did the skills associated with using the blood pressure cuff influence its acceptance by physicians? The early 1900s was a period of considerable change in medicine in the United States. Many new medical tools were just entering practice. Some were being passed into the hands of nurses and technical assistants, who were taking increasingly active roles in medical work in the hospital [34]. In this setting, physicians may have felt it necessary to distinguish a level of skill appropriate for their own practices.

Cushing, Briggs, and Cook introduced the blood pressure cuff as a relatively simple tool, appropriate for use by nurses and requiring little skill to operate. The new cuff, used in this way, fell into an ambiguous middle ground. Physicians were perhaps reluctant to put a novel medical device directly into the hands of nurses. The ability of nurses to use the cuff may also have implied that the practice was insufficiently skilled for physicians. The example of the clinical thermometer, a specialized physician's tool of the 19th century, offers a valuable comparison. By 1900, records from hospitals in Boston, Philadelphia, and Baltimore showed that nurses made hundreds of measurements with the thermometer daily (as Cushing had noted), whereas physicians rarely used the tool, sometimes simply copying results from a nurse's chart into their own notes [35, 36].

The introduction of auscultation with the stethoscope created a way to measure blood pressure that required more skill. It made the practice exclusive to physicians and seemed to secure it a regular place in the clinical realm. By 1910, the stethoscope was an essential tool of the practicing physician. Auscultation of heart and lung sounds had become a hallmark of the physician's highly skilled physical examination [13, 28]. In addition, the stethoscope was one medical tool that had not passed into the hands of the nursing staff. It would be another half-century before nurses began to routinely acquire stethoscopes in conjunction with the gradual acceptance of blood pressure measurement as a nursing practice in the 1960s [36]. When stethoscopes did routinely come into the hands of nurses, great care was exercised to avoid any confusion between the nurse's tool and the physician's. The new nursing stethoscopes of the 1960s had such names as the assistoscope and the nurse-o-scope and were made of lightweight, pastel-colored materials to clearly distinguish them from the heavy, black tubes that were still the exclusive property of physicians (Advertisement. American Journal of Nursing. 1968; 68:1190). More serious tools implied more serious practices, helping to avoid the appearance of overlap in the practices of the two professions.

Standardized Medical Practice

Auscultation to measure blood pressure found wide acceptance as a skilled practice for physicians. As such, it retained a need for the individual physician's experience and judgment that was missing in Cushing's method. Cushing had argued that the blood pressure cuff could be used in a completely standard way that would yield the same results regardless of the operator. If the operator was a physician, however, standardization of practice was not essential or even, perhaps, desirable.

As U.S. physicians began using auscultation to measure blood pressure, they emphasized the complex, subjective elements of this practice. Korotkoff's original report in 1905 [21] had proposed the simple method of listening for the appearance and disappearance of pulse sounds to mark maximal and minimal pressures. Early U.S. articles on auscultation encouraged physicians instead to divide the changing sounds heard in the artery into five distinct “Korotkoff phases,” each marking its own pressure change [37]. In the clinical literature, physicians began reporting systolic and diastolic pressures, but they also recorded other, subjective data available with auscultation; for example, they noted when “the sharp click of the systolic is weak” [38].

The more complex (and subjective) method of auscultation also permitted flexibility in how physicians used the cuff. Although a blood pressure of 120/80 mm Hg in the medical record in 1917, for example, looked like a standard, objective measurement, the diastolic pressure of 80 mm Hg actually meant different things to different physicians. For most of the 20th century, physicians in the United States determined diastolic pressure according to either of two distinct, incommensurable definitions: at the “muffling” of pulse sounds (the fourth Korotkoff phase) or at the disappearance of sounds (the fifth phase) [39]. The choice depended on a physician's training and experience. About the lack of a standard definition for diastolic pressure, one commentator in 1918 remarked that “time alone will settle this question” [39]. It was not until the 1970s-after blood pressure measurement was already being delegated to nurses-that a standard definition prevailed [40].

In the interim, attempts were made from outside medicine to impose such a standard. In 1924, the U.S. Bureau of Standards, at the behest of the U.S. military, established standards for the construction and calibration of blood pressure cuffs [41]. In its initial report, however, the Bureau warned that their efforts should be considered in light of the absence of a standard method for operating the cuff. As early as 1917, a U.S. insurance company called for a standard definition of diastolic blood pressure among their medical examiners [42]. Physicians, however, showed no interest in further standardizing a practice that was already securely under the control of individual physicians.

Conclusions

Physicians in the United States during the 20th century have exercised considerable influence over the introduction of new medical technologies. Even a simple tool, such as the blood pressure cuff, offered them significant choices about who would use it and how it would be used. The evolving use of the blood pressure cuff manifested the concerns of physicians about the skills involved and reflected in their clinical practice. The blood pressure cuff did not replace the expert practice of pulse palpation initially, and it did not become a routine nursing tool for many decades. Physicians did replace the practice of pulse palpation with the more objective practice of auscultation for blood pressure. However, well into the 20th century, the cuff continued to be used in a way that yielded individualized, subjective data.

Despite some external efforts to standardize this practice, U.S. physicians continued to treat the blood pressure cuff as a tool for skilled physical examination. It remained for the individual practitioner to determine how to measure diastolic blood pressure, despite the uncertainty that this introduced into the interpretation of the measurement.

Concern about the control of medical technology and medical practice has arisen today in various debates. Contemporary controversy over the use of the flexible sigmoidoscope by nonphysicians is one notable example. Modern debates over the standardization of medical practice and medical decision making engage related concerns about preserving a role for expert skills in the physician's work. Examination of the early history of the blood pressure cuff shows just how deeply such concerns may be woven into the basic practices and tools of medicine.