Blood pressure measurements in obese persons: Comparison of intra-arterial and auscultatory measurements∗

Abstract

1.1. Simultaneous direct intra-arterial blood pressure measurements and indirect measurements with the auscultatory method were made in 100 subjects. The subjects were grouped according to their Ponderal Index W/H, weight per inch of height. Sixty-one subjects were obese, thirty-nine were nonobese. 2.2. Nine out of the ten stoutest subjects were hypertensive, whereas only one of the ten leanest subjects was hypertensive. 3.3. The indirect method generally underestimates systolic and overestimates diastolic pressure. This holds for lean persons as well as for moderately obese persons. 4.4. The discrepancies between the direct and indirect methods were usually minor among the lean and the moderately obese subjects and went in both directions. Falsely high blood pressure readings in lean and moderately obese persons are not common. 5.5. In extremely obese persons the indirect method is subject to considerable error. In eight out of ten such persons the systolic pressure was overestimated, and in nine out of ten such persons the diastolic pressure was overestimated. 6.6. Overestimation of systolic pressure in very obese persons can be much greater than was heretofore known; it amounted to 44, 50 and 51 mm. in three of our stoutest subjects. 7.7. Falsely high readings in extremely obese subjects are caused by the large size of their arms. If this possibility is borne in mind, an unwarranted diagnosis of hypertension is not likely to be made. In dubious cases, intraarterial measurement should be resorted to. 8.8. Many factors other than arm size may cause inaccuracies of the indirect method, and the large arm does not regularly cause falsely high readings. It is not feasible to apply a correction to an individual reading.