1. Head of bed angle does not accurately reflect patient position
A semi-recumbent body position has been demonstrated to reduce the incidence of nosocomial pneumonia in mechanically ventilated patients1. The Scottish Patient Safety Programme advocates a head of bed angle > 30° for ventilated patients.
A modified goniometer was developed which provides a simple means of measuring the patient position relative to the horizontal. By placing the instrument on two points on the patient's sternum, a mathematical model utilising basic angle properties allows patient angle to be calculated by means of a simple formula (see figure 1).
S Gillon†, R Sundaram†, A Gillon‡
†Dept of Anaesthetics and Intensive Care
Royal Alexandra Hospital, Paisley
‡Dept of Mathematics
Gourock High School, Gourock
When angle of the bedrest was measured using the modified goniometer, target was achieved on 47 occasions (78.33%) (range 22-60; mean 41.6°). On measuring the angle of the patient, in only eighteen observations (30.51%) was target achieved (range ; mean 25.45°). There was a mean difference between bed anglemeter and patient angle of °(range 4 – 35°).
Figure 2 Relationship between bed angle meter and directly measured patient angle.
Figure 1 Modified Goniometer. Angle y represents the patient angle relative to the horizontal y = 180 – (75 + (x + 30)), therefore y = 75 – x.
The anglemeter incorporated into the ICU bed does not accurately reflect the angle of the patient. This may be in part due to inaccuracies in the anglemeter. The discrepancy between bed and patient angle, when both are measured using the modified goniometer, suggests that bed angle measured by any means is of little use in determining patient position. The implications of this finding on the relevance of the ≥30° bed angle in the prevention of VAP, require further investigation.
Over a seven day period on our seven-bed general adult ICU, the bed angle - as indicated by both the bed anglemeter and by our modified goniometer – and the patient angle were recorded. Twice daily recording yielded fifty-nine observations.
On all occasions the anglemeter displayed value greater than 30° (range 30-60; mean 41.6°).
1. Drakulovic MB et al (1999) Supine body position as a risk factor for nosocomial pneumonia in mechanically ventilated patients: a randomised trial. The Lancet. 354: