Basic life support providers' assessment of centre of the chest and inter-nipple line for hand position and their underlying anatomical structures

Introduction: Effective chest compression is an integral part of good quality cardiopulmonary resuscitation. There remains uncertainty over the optimal method for identifying the correct hand position for chest compression. The aim of this study was to identify the relationship between basic life support (BLS) providers assessment of the inter-nipple line (INL) versus the centre of the chest (CoC) and to identify the anatomical structures underneath these landmarks.

Method: Thirty consecutive patients having elective CT scans of the thorax were recruited and photographs of the patient fully clothed were taken in the supine position. 30 healthcare students trained in BLS were asked to mark the 'point between the nipples' and the 'centre of the chest' on each photograph in a random sequence. Corresponding points were marked on the CT images and the underlying anatomical structures were identified.

Results: Hand positions using CoC landmark were significantly higher and were more variable than INL landmark (measurement represented as ratio of sternal length: mean CoC 0.709, 95% CI 0.677, 0.740 versus mean INL 0.803 95% CI 0.772, 0.835; p<0.0001). Structures underneath CoC and INL hand positions were significantly different; CoC compressing predominantly the aortic arch and ascending aorta and INL compressing the left ventricle and left ventricular outflow (p<0.001). Hand positions were not significantly affected by gender of patients.

Conclusion: Both the centre of the chest landmark and inter-nipple line identify positions on the lower third of the sternum. The centre of the chest technique identifies a point that is consistently higher and more variable than the inter-nipple line. Structures compressed under both landmarks were different although the implications of this are unknown.