title: Bell or diaphragm in the measurement of blood pressure?
abstract: BACKGROUND
  International guidelines have given diverse recommendations as to which side of the stethoscope should be used in the measurement of blood pressure.
  
  
  OBJECTIVE
  To determine if there is any difference between the bell and the diaphragm sides of the ordinary acoustic stethoscope in the measurement of blood pressure.
  
  
  METHODS
  We compared, in random order, the bell and the diaphragm side of the ordinary acoustic stethoscope and also the effect of low- and high-frequency amplification with an electronic stethoscope in the measurement of blood pressure, in 250 adults.
  
  
  METHODS
  Department of Medicine, Turku University Central Hospital.
  
  
  RESULTS
  No statistically significant difference was seen between the bell side and the diaphragm side of the acoustic stethoscope, either in systolic blood pressure (SBP; mean +/- SD 129.5 +/- 21.7 and 129.4 +/- 20.8 mmHg, respectively) or diastolic blood pressure (DBP; 77.0 +/- 12.0 and 77.1 +/- 12.0 mmHg, respectively). Both the low-frequency (130.7 +/- 22.5 mmHg) and the high-frequency (131 +/- 22.2 mmHg) amplification of systolic Korotkoff sounds yielded significantly greater values of SBP than were measured either with the bell (P = 0.008 compared with low frequency, P = 0.0005 compared with high frequency) or the diaphragm (P = 0.004 compared with low frequency, P = 0.0001 compared with high frequency). Low-frequency amplification of DBP (76.4 +/- 12.3 mmHg) yielded values significantly lower than those measured with the bell (P = 0.04) or the diaphragm (P = 0.01). Values from high-frequency amplification of DBP (77.2 +/- 12.3 mmHg) did not differ significantly from those measured with the acoustic stethoscope.
  
  
  CONCLUSIONS
  Both sides of the acoustic stethoscope give similar results in the measurement of office blood pressure and either side can be used in the reliable measurement of blood pressure.
authors.affiliation: Department of Medicine, Turku University Central Hospital, Turku, Finland. ilkka.kantola@tyks.fi
authors.forename: Ilkka
authors.initials: I
authors.lastname: Kantola
authors.forename: Risto
authors.initials: R
authors.lastname: Vesalainen
authors.forename: Kari
authors.initials: K
authors.lastname: Kangassalo
authors.forename: Antti
authors.initials: A
authors.lastname: Kariluoto
mesh_terms: D000328:Adult; D001314:Auscultation / Q000295:instrumentation / Q000379:methods; D001795:Blood Pressure Determination / Q000295:instrumentation* / Q000379:methods* / Q000592:standards; D004581:Electronics; D005260:Female; D006801:Humans; D006973:Hypertension / Q000175:diagnosis*; D008297:Male; D015203:Reproducibility of Results; D019023:Stethoscopes