Where does pulse collide?

The rhythmic wave of pressure and distension that travels along an artery each time the heart ejects blood: it can be felt where a vessel runs near the surface, and its rate, rhythm, and shape carry clinical information. O'Rourke's 2001 Pulse wave analysis described how the arterial waveform is generated by the ejected stroke and shaped by wave reflection along the vascular tree, and how it is recorded and decomposed. The referent is a mechanical wave in a living artery, timed in beats per minute and described by its contour, not a coded sample in a wire, a seed on a plant, or a flash from a star.[1]

Unit

A heartbeat's pressure wave in an artery, in beats per minute

Recovery means

The vessel wall recoils between beats, and the diastolic decay of the waveform reflects that elastic return

Measured by

Counted by palpation as rate and rhythm, and recorded in detail by tonometry or pressure transducers for waveform analysis

A brief, bounded excursion of a signal from its baseline, used as the elementary unit that carries information in a discrete communication or timing system: a pulse has a width, an amplitude, and a position in time, and a train of them can encode a sampled value. Oliver, Pierce, and Shannon's 1948 The Philosophy of PCM set out how a continuous waveform can be sampled, quantised, and sent as coded pulses that resist noise. The referent is an engineered transient in a channel, defined by its shape and timing, and it is unrelated to a wave felt in an artery, a crop in a field, or a beam from a neutron star.[2]

Unit

A bounded signal excursion, described by width, amplitude, and timing

Recovery means

Not applicable

Measured by

Characterised on an oscilloscope or in sampled data by pulse width, rise time, amplitude, and inter-pulse interval

The regular burst of radiation received from a pulsar: a rotating, magnetised neutron star sweeps a beam of radio emission past the observer, so a detector records a sharp, highly periodic pulse once per rotation. Hewish, Bell, Pilkington, Scott, and Collins's 1968 Observation of a rapidly pulsating radio source reported the first such source and the clock-like regularity of its pulses. The referent is a periodic astrophysical signal set by a star's spin, timed to fractions of a second, and it is not a pulse felt at the wrist, a pulse sent down a wire, or a pulse grown in a field.[3]

Unit

A neutron star's periodic radiation burst, one per rotation

Recovery means

Not applicable

Measured by

Detected by radio telescopes and folded at the spin period to recover the average pulse profile and its precise timing