A bounding pulse means a high volume pulse, which can be felt on the radial or carotid artery. There are a lot of reasons for that.
Collapsing pulse means high pulse pressure. Pulse pressure is the gap between systolic blood pressure and diastolic blood pressure. Systolic blood pressure is the blood pressure in the aorta when the heart is contracting. Diastolic blood pressure is the blood pressure of the aorta when the heart is relaxing. When we felt the pulse, we felt the pulse pressure. That means the gap between systolic and diastolic blood pressure. To feel high pulse pressure, systolic blood pressure can be increased, diastolic blood pressure can be decreased, or both can happen simultaneously. Because of this reason, a collapsing pulse can be present. The most common example of that is aortic regurgitation.
In aortic regurgitation, blood can go out via the aortic valve when the heart is contracting. But in the comfortable position of the heart, blood can come back to the ventricles. That is the abnormal condition in aortic regurgitation.
In most of the chances, a bounding pulse should be present if a patient has a collapsing pulse. But every patient with a bounding or high volume pulse does not necessarily have a collapsing pulse. If a patient has collapsed and both bounding pulses, it is most probably aortic regurgitation. That means an incompetent aortic valve.
There are two complicated common words related to that. They are Watson’s water hammer pulse and Corrigan’s sign. These two are common examination findings of the patient with aortic regurgitation. In aortic regurgitation, patients have high volume pulse and increased pulse pressure. Because of the high pulse volume, the carotid pulse can be easily visible on the neck. That sign is called Corrigan’s sign. But in elevated jugular venous pressure, pulsation can be seen on the channel. It can be falsely taken as Corrigan’s sign. To differentiate these two things, you can palpate over the visible pulse. If you can feel and see the pulse, it is carotid. But if you can only see and can’t think, it is a jugular venous pulse. In the same situation with Corrigan’s sign, if you can see the brachial and wrist pulses, which are radial and ulnar, that is called Watson’s water hammer pulse.
In summary, a bounding pulse means just a high volume pulse. Collapsing pulse means wide pulse pressure. Corrigan’s sign is visible pulsation on the neck due to the high volume in carotids.
Watson’s water hammer pulse means visible arterial pulsation on the neck, brachial, radial and ulnar areas.