The valuable information about a person's stroke volume can be obtained from the arterial pulse pressure, as long as the arterial compliance is normal. Individuals with severe congestive heart failure or severe hemorrhage typically have a very low arterial pulse pressure due to their abnormally small stroke volumes. On the other hand, individuals with large stroke volumes, such as those with aortic valve regurgitation, are likely to have an increased arterial pulse pressure. Similarly, well-trained athletes at rest tend to have large stroke volumes because their heart rates are usually low. The prolonged ventricular filling times in these individuals cause the ventricles to pump a large stroke volume, resulting in a large pulse pressure.

The pressure wave initiated by the radial stretch of the ascending aorta during left ventricular ejection travels down the aorta and its branches at a much faster rate than the blood itself (approximately 4 to 12 m/second). This pressure wave, also known as the "pulse," can be detected through palpation of a peripheral artery.

In individuals with chronic hypertension, a condition characterized by a persistent elevation in total peripheral resistance (TPR), the arterial pressure-volume curve resembles the one shown in Figure 17.17B. As arteries become less compliant when the TPR increases, the systolic pressure becomes more elevated than the diastolic pressure. Diastolic pressure is elevated in these individuals, but usually not more than 10 to 40 mmHg above the average normal level of 80 mmHg. However, systolic pressure is commonly elevated by 50 to 100 mmHg above the average normal level of 120 mmHg.

The velocity of the pressure wave is inversely related to arterial compliance. Generally, the transmission velocity increases with age, indicating that arteries become less compliant with advancing age. Velocity also increases progressively as the pulse wave travels from the ascending aorta towards the periphery, reflecting the decrease in vascular compliance in the more distal portions of the arterial system compared to the more proximal portions.

The pressure wave contour becomes distorted as it is transmitted down the arterial system. This distortion in the pressure wave contour of the human arterial tree is demonstrated by age and recording site in Figure 17.19. Damping of the high-frequency components of the arterial pulse is primarily caused by the viscoelastic properties of the arterial walls. The pulse pressure wave travels more rapidly in older people than in younger people due to reduced compliance. Several factors, including wave reflection and resonance, vascular tapering, and pressure-induced changes in transmission velocity, contribute to the peaking of the pulse wave.

Blood pressure is commonly estimated indirectly using a sphygmomanometer. In hospital intensive care units, needles or catheters may be inserted into peripheral arteries of patients to directly measure arterial blood pressure using strain gauges. When blood pressure readings are taken from the arm, the systolic pressure can be estimated by palpating the radial artery at the wrist (palpatory method). When the pressure in the cuff exceeds the systolic level, no pulse is felt. As the pressure falls just below the systolic level, a spurt of blood passes through the brachial artery under the cuff during the peak of systole, and a slight pulse is felt at the wrist (Figure 17.20A).
Arterialpulsepressureprovidesvaluableinformationaboutaperson’sstrokevolume,providedthatarterialcomplianceisessentiallynormal.Patientswhohaveseverecongestiveheartfailureorwhohavesufferedaseverehemorrhagearelikelytohaveaverylowarterialpulsepressurebecausetheirstrokevolumesareabnormallysmall.Conversely,individualswithlargestrokevolumes,asinaorticvalveregurgitation,arelikelytohaveanincreasedarterialpulsepressure.Similarly,well-trainedathletesatresttendtohavelargestrokevolumesbecausetheirheartratesareusuallylow.Theprolongedventricularfillingtimesintheseindividualsinducetheventriclestopumpalargestrokevolume,andhencetheirpulsepressureislarge.
The radial stretch of the ascending aorta brought about by left ventricular ejection initiates a pressure wave that is propagated down the aorta and its branches. The pressure wave travels much faster (≈4 to 12 m/second) than the blood itself does. This pressure wave is the “pulse” that can be detected through palpation of a peripheral artery.
Inchronichypertension,aconditioncharacterizedbyapersistentelevationinTPR,thearterialpressure-volumecurveresemblesthatshownin
Fig.17.17B . BecausearteriesbecomesubstantiallylesscompliantwhenParises,anincreaseinTPRcausessystolicpressuretobemoreelevatedthandiastolicpressure.Diastolicpressureiselevatedinsuchindividualsbutordinarilynotmorethan10to40mmHgabovetheaveragenormallevelof80mmHg.Notuncommonly,however,systolicpressureiselevatedby50to100mmHgabovetheaveragenormallevelof120mmHg.
Thevelocityofthepressurewavevariesinverselywitharterialcompliance.Ingeneral,transmissionvelocityincreaseswithage,whichconfirmstheobservationthatthearteriesbecomelesscompliantwithadvancingage.Velocityalsoincreasesprogressivelyasthepulsewavetravelsfromtheascendingaortatowardtheperiphery.Thisincreaseinvelocityreflectsthedecreaseinvascularcomplianceinthemoredistalportionsthaninthemoreproximalportionsofthearterialsystem.
ThePacontourbecomesdistortedasthewaveistransmitteddownthearterialsystem.Thisdistortioninthepressurewavecontourofthehumanarterialtreeisdemonstratedasafunctionofageandofrecordingsitein
Fig.17.19 .Dampingofthehigh-frequencycomponentsofthearterialpulseiscausedlargelybytheviscoelasticpropertiesofthearterialwalls.Thepulsepressurewavetravelsmorerapidlyinolderpeoplethanintheyoungerpeople,asaconsequenceofreducedcompliance.Severalfactors—includingwavereflectionandresonance,vasculartapering,andpressure-inducedchangesintransmissionvelocity—contributetopeakingofthePawave.
Most commonly, blood pressure is estimated indirectly by means of a sphygmomanometer. In hospital intensive care units, needles or catheters may be introduced into the peripheral arteries of patients to measure arterial blood pressure directly by means of strain gauges. When blood pressure readings are taken from the arm, systolic pressure may be estimated by palpation of the radial artery at the wrist (palpatory method). While pressure in the cuff exceeds the systolic level, no pulse is perceived. As pressure falls just below the systolic level (
Fig. 17.20A ), a spurt of blood passes through the brachial artery under the cuff during the peak of systole, and a slight pulse is felt at the wrist.