Upper ribs move like a pump handle, lower ribs like a bucket handle
Mnemonic
“Pump handle up and forward, bucket handle up and out”:
- Pump handle - the upper ribs (2 to 6) rotate about a transverse axis, raising the sternum forwards and increasing the anteroposterior diameter
- Bucket handle - the lower ribs (7 to 10) swing about an anteroposterior axis, raising the shafts laterally and increasing the transverse diameter
- Caliper movement - the floating ribs (11 and 12) swing outwards
The difference arises from the orientation of the costovertebral and costotransverse joints, which lie more transversely in the upper ribs and more obliquely lower down.
Together they increase thoracic volume in all three dimensions, the vertical dimension being provided by the diaphragm, which alone accounts for about two thirds of quiet tidal volume.
In emphysema the chest is already hyperinflated, so the ribs are near their maximum elevation and further movement gains little, producing the barrel chest and the inefficient breathing that drives accessory muscle use.
Expansion
- Pump handle - ribs 2 to 6. The sternal end swings upwards and forwards, increasing the anteroposterior diameter
- Bucket handle - ribs 7 to 10. The middle of the shaft swings upwards and outwards, increasing the transverse diameter
The difference comes from the axis of the costovertebral and costotransverse joints. In the upper ribs that axis lies close to the coronal plane, so movement is forwards; in the lower ribs it lies closer to the sagittal plane, so movement is sideways.
The diaphragm adds the third dimension by increasing the vertical diameter, and together the three account for the volume change of quiet inspiration.