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Stethoscope head to body weight ratios in the extremely preterm infant
  1. D S Urquhart,
  2. V P Balasubramaniam
  1. Neonatal Unit, Northwick Park Hospital, Watford Road, Harrow, Middlesex HA1 3UJ, UK; donurquhart72{at}

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    It has been our observation that large nursing style stethoscopes are often used on extremely premature infants, whereas paradoxically a smaller neonatal stethoscope is usually used for the term neonate. Stethoscope heads were weighed using precision scales, and a ratio of stethoscope head weight to baby weight was calculated (SHBW ratio). This somewhat crude ratio does not take into account the added effect of the clinician pressing the stethoscope on to the chest. The weight of a large stethoscope head was 41 g and that of a small stethoscope head was 28 g. Figure 1 shows auscultation of a 25 week baby weighing 675 g. The SHBW ratio was 1:15 for the large stethoscope head shown.

    Auscultation with a large stethoscope head may place undue force on the chest or abdomen of a tiny baby. Using the same ratio (1:15), a 70 kg male would have a stethoscope head weighing 4.4 kg placed on his chest, an uncomfortable experience for both patient and examiner! Auscultation and the associated pressure applied by the auscultator may well be an unpleasant experience for extremely low birthweight infants. Care should be taken to use the smallest stethoscope possible and to apply minimal pressure when examining low birthweight infants.

    Figure 1

    Auscultation of a premature (25 weeks gestation) baby.

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