segmental pressure measurement and plethysmography · pdf filesegmental pressure measurement...

Segmental Pressure Measurementand Plethysmography

Ann Marie Kupinski PhD RVT

Introduction

The current status and rapidly evolving capabilitiesof duplex ultrasonography are hard to overlook In-vestigators are presented with a myriad of transduc-ers image and Doppler formats and system configu-rations However ultrasound technology has onlywidely impacted vascular laboratories for the past twodecades Before the 1980s indirect techniques wereused to noninvasively detect arterial disease Thesetechniques include segmental pressure measurementsand plethysmographic waveforms Although the tech-nology involved is not as complex as duplex ultraso-nography these modalities yield information on thestatus of the peripheral arterial system and the pres-ence or absence of disease can be rapidly ascertainedThe degree of severity of the occlusive process can bedetermined and ranked into appropriate categoriesusing qualitative terms such as mild moderate or se-vere Last anatomic details pertaining to the level ofdisease can be interpreted from pressure measure-ments and waveforms These types of noninvasivetests are used as primary screening tools when assess-ing patients with suspected peripheral arterial diseaseThe results of these tests can help the clinician selectpatients for further testing intervention or othercourses of treatment

Segmental Pressure Measurement

The measurement of pressure within a limb is doneby placing a cuff around the part of limb to be inves-tigated The cuff is inflated with enough pressure toocclude the artery and stop blood flow The cuff isthen slowly deflated while using some method to de-tect the pressure at which blood flow resumes distal tothe cuff The methods available to detect the return ofblood flow are varied and include strain-gauge pleth-ysmography1 photoplethysmography2 and Dopplerinstrumentation The most common device used to de-tect blood flow is a continuous wave (CW) DopplerThe frequency selected is typically between 4ndash8 MHz

which allows for the insonation of both deep and su-perficial vessels

Cuff Size

The measurement of limb pressure is significantlyaffected by the size of the pressure cuff used Accuratereadings can only be achieved by using the appropri-ate sized cuff The cuff itself surrounds an inflatablebladder It is the width of this bladder that is criticallyimportant If the cuff bladder is too narrow the bloodpressure reading will be falsely high If the cuff blad-der is too wide the pressure measurement will befalsely low Inappropriate cuff use during the mea-surement of brachial artery blood pressures has beenshown to produce an average error of 85 mmHg3 TheAmerican Heart Association recommends that thebladder width be 40 of the circumference of the limbor 20 wider than the limb diameter4 Table 1 listsrecommended cuff bladder sizes for lower limb pres-sure determinations5ndash7 For extremely obese patientsor patients with unusually small limbs the cuff se-lected should be appropriately sized

Examination Technique

The technique for obtaining segmental pressuremeasurements begins with placing the patient in a su-pine position The feet should be elevated on a smallcushion so that the ankles are at approximately thesame level as the heart This position will reduce theeffects of added hydrostatic pressure Brachial bloodpressure should be measured bilaterally By doing soany latent subclavian artery disease will be revealedand the most accurate calculation of an anklendashbrachialindex (ABI) can be determined Pneumatic cuffs arethen placed around the legs at the ankle calf andthigh levels The ankle cuff should be placed justabove the malleolus The calf cuff should be aroundthe widest portion of the calf just below the tibialtuberosity One singular contoured thigh cuff may beused or two cuffs may be placed around the upperand lower thigh The high thigh cuff should be posi-tioned such that the upper edge of the cuff is at thehighest level of the inner thigh The low thigh cuffshould be positioned such that the lowest edge of thecuff is just above the patella

The measurement of systolic pressure begins at theankle The Doppler stethoscope is used to detect flow

From Karmody Vascular Laboratory Institute for VascularHealth amp Disease Albany Medical Center Albany NY

Address correspondence to Ann Marie Kupinski PhD RVTKarmody Vascular Laboratory MC-157 Institute for VascularHealth amp Disease Albany Medical Center 47 New Scotland AveAlbany NY 12208

The Journal of Vascular Technology 26(1)32ndash38 2002

within either the posterior tibial artery or the dorsalispedis artery While listening to the flow signal theankle cuff is inflated above the brachial systolic pres-sure until the flow signal is no longer heard The cuffsshould continue to be inflated 20ndash30 mmHg beyondthe pressure at which the last audible signal was ob-tained8 This is done to ensure complete closure of theartery The cuff is then slowly deflated until the Dopp-ler signal returns The rate of deflation should be ap-proximately 2ndash4 mmHg per sec This will allow for aprecise measurement of the systolic pressure Aftermeasurement of the ankle pressure the calf and thenthe thigh pressures are recorded

If the Doppler signal is absent at the ankle level theankle cuff can be removed and the mid to distal tibialarteries can be examined with the Doppler stetho-scope If a flow signal is obtained within the mid-calfthis can be use to determine the calf and thigh pres-sures If no signal can be appreciated from the tibiallevel the popliteal artery is then examined A Dopplersignal from the popliteal fossa can be used to deter-mine the thigh pressure

Interpretation

Because ankle systolic pressures are compared withthe brachial artery pressures it is important to haveaccurate measurements of brachial artery pressureThe right and left brachial pressures should be equalIf these pressures differ by more than 20 mmHg anabnormality exists9 The arm with the lower pressurelikely contains a hemodynamically significant obstruc-tion within the subclavian artery However furthertesting would be needed to determine the exact loca-tion of such an obstruction Thus the higher of the twobrachial artery pressures should be used for calcula-tions of the ABI

As stated earlier both the posterior tibial and dor-salis pedis arteries can be used to determine anklepressure The pressure measured at these two arteriesshould not differ by more than 10 mmHg and varia-tions greater than 15 mmHg suggest a proximal ob-struction in the artery with the lower pressure10 Thehigher pressure reading is the value used in the cal-culation of the ABI The ankle systolic pressure nor-mally is greater than the brachial systolic pressure by12ndash24 mmHg11 12 This occurs as a result of an aug-mentation in the pulse pressure as blood travels to the

periphery This augmentation is due to less elastic dis-tal arterial walls and reflections of the pressure wavefrom distal branch points and the peripheral vascularbed

One of the most common technical errors that canoccur in the measurement of ankle pressures is due tothe presence of medial calcification13 14 Calcificationcan result in falsely elevated pressure measurementsor the inability to completely occlude the arterial flowsignal Medical calcification is frequently encounteredin diabetic patients or patients with chronic renal fail-ure Calcific vessels are suspected when the anklepressures exceed 300 mmHg Although the medial cal-cification has a pronounced affect on ankle pressuremeasurements it does not have an impact on plethys-mographic or Doppler waveforms

Ankle Brachial Index

Pressure measured at any point along the vascularsystem is going to vary because the dynamic pressuresupplied by the heart varies Because of this calculat-ing the ABI can normalize the ankle pressure The ABIis simply the ankle systolic pressure divided by thebrachial systolic pressure The range for normal ABI isbetween 10 and 1115ndash18 In the presence of significantarterial disease the ABI is typically less than 1015 18

However it is possible for a patient to have arterialdisease yet have a resting ABI of 10 or greater18 19

Other studies have shown that only rarely does anindividual without arterial disease have an ABI of lessthan 09220 If a patient has ldquonormalrdquo resting ABIs butdescribes symptoms associated with exercise this pa-tient should undergo exercise testing to detect the pre-sent of a subcritical stenosis

In early work by Yao21 the degree of functionalimpairment within subjects was compared with themeasured ABI He identified the following groups nosymptoms ABI 10 claudication ABI = 05ndash10 restpain ABI = 025ndash050 impeding tissue loss ABI 025Even though some overlap occurred it is clear thatwith increasing severity of symptoms there is a pro-gressive decrease in the ABI It has also been observedthat differences in the ABI occur with increasing num-ber of diseased segments of the arterial tree22 An ABIof 05 is found in patients with only a single levelobstruction whereas an ABI of lt05 is often associatedwith multilevel disease Within an individual themeasurement of the ABI is fairly stable between ex-aminations providing there is no significant change inthe degree of disease A change in the ABI of 015from one examination to the next has been shown tobe a good indicator of increasing severity of disease23

Segmental Pressures

Although an ABI will identify those patients withsignificant arterial disease it does not specify the seg-ments involved By measuring the pressure gradientsdown the limb additional information can be ob-tained The systolic pressure measured with a highthigh cuff is normally 30ndash50 mmHg greater than thebrachial systolic pressure24 There is a great deal of

Table 1

Recommended Cuff Bladder Width for Lower Limb Pressures inthe Average Adult

Cuff Level Cuff Width (in cm)

Upper thigh 11Lower thigh 19Single contoured thigh cuff 22Calf 12Ankle 10ndash12Transmetatarsal 7ndash8Toe 25ndash3

2002 SEGMENTAL PRESSURES AND PVRs 33

inaccuracy with pressure measurements at this levelThe pressure within the common femoral artery is al-most always equal to the brachial artery pressurewhen measured by invasive techniques25 The differ-ence between the thigh diameter and cuff size resultsin a higher thigh pressures in patients with largerthighs and lower more accurate pressures in patientswith smaller thighs The presence of hemodynami-cally significant disease will result in thigh pressuresequal to or lower than the brachial pressure24

The normal variation in pressure measurement be-tween limb segments should be no more than 20ndash30mmHg26 A gradient of greater than 30 mmHg is sug-gestive of significant arterial obstruction between thesegments measured27 If an artery is completely oc-cluded a gradient of greater than 40 mmHg is ob-served26 In addition to measuring differences withinthe same limb it is also beneficial to compare pres-sures between limbs The limb pressures recorded inthe right and left lower extremity should be similar atthe same level A difference of greater than 20 mmHgis considered hemodynamically significant16 It is pos-sible for normal pressure gradients to be obtainedwithin limbs with arterial obstructions if large collat-eral vessels are present This does not reflect an errorin the measurement Pressure measurements are re-flective of the functional status of the arterial circula-tion rather than the anatomic condition of the vessels

Plethysmography

A plethysmograph is a device that records varia-tions in volume or blood flow through an extremityThe volume of an extremity changes between systoleand diastole as a result of the pulsatile blood flow intothat region There are a number of different types ofplethysmographs that use various means to measurethese changes These include water air electrical im-pedance mercury in rubber strain gauge and photo-electric plethysmography Segmental air plethysmog-raphy is an important part of the noninvasive assess-ment of arterial disease In the 1970s the pulse volumerecorder (PVR) was developed and tested at the Mas-sachusetts Institute of Technology and MassachusettsGeneral Hospital28 2 9 The PVR measures pressurechanges in the bladder of the cuff wrapped around thelimb The cuff pressure changes actually reflectchanges in the cuff volume which is a direct reflectionof changes within the limb volume PVR units are cali-brated so that a 1 mmHg pressure change in the cuffproduces a 20-mm deflection (amplitude) on the chartrecorder In normal patients these noninvasive ple-

thysmographic waveforms strongly resemble directintraarterial pressure pulse contours29


The operation of a PVR is straightforward but careneeds to be taken to ensure reproducible results Bloodpressure cuffs are placed around the limb and at-tached to the plethysmograph The same cuffs used tomeasure segmental pressures are used for the record-ing of the PVRs The appropriate size should be se-lected as previously described for the pressure mea-surements (see Table 1) A measured quantity of air isinjected until a preset pressure is achieved The pres-sure within the cuff must be sufficient enough to pro-duce adequate contact between the limb and the cuffbladder Once the appropriate pressure is reachedwithin the cuff the plethysmographic tracings are re-corded over three to four complete cardiac cycles Theoriginal criteria developed with the PVR are listed inTable 230 Although slight variations occur betweenlaboratories it is important to develop standardizedcriteria for obtaining PVRs so that results may becomparable between visits

Interpretation

The PVR amplitude is highly reproducible in thesame patient when care is taken to maintain consistentcuff volumes and pressures29 The PVR amplitude willvary between patients and is affected by ventricularstroke volume blood pressure vasomotor tone bloodvolume and the size and position of the limb In veryobese patients or those with extensive edema the PVRwaveforms can be attenuated With increasing sever-ity of disease the pulse amplitude decreases PVR re-cordings have been classified into five categoriesbased on pulse amplitude and contour which are de-fined in Table 3 Other grading systems may use terms

Table 2

Original Criteria for the Pulse Volume Recorder (PVR)

Anatomic Level Bladder Size Inflation Pressure Inflation Volume Gain

Thigh 36 times 18 cm 65 mmHg 400 plusmn 75 cc 1Calf and ankle 22 times 12 cm 65 mmHg 75 plusmn 25 cc 1Transmetatarsal 12 times 7 cm 65 mmHg 50 plusmn 10 cc 25Digits 9 times 3 or 7 times 2 cm 40 mmHg 5 plusmn 3 cc 5

Table 3

Definition of Pulse Volume Recorder (PVR) Categories

PVR Category

Chart Deflection (in mm)

Thigh and Ankle Calf

1 gt15 gt202 gt15dagger gt20dagger3 5ndash15 5ndash204 lt5 lt55 Flat Flat

With reflected wavedaggerNo reflected wave

34 KUPINSKI JVT 26(1)

Figure 1

Pulse volume recordings demonstrating normal characteristics (A) and progressive changes with disease (B) mild obstruction (C)moderate obstruction (D) severe obstruction or occlusion

Figure 2

A PVR study demonstrating abnormal inflow to the right leg These waveforms are consistent with iliofemoral disease The left leg iswithin normal limits


such as ldquonormalrdquo ldquomildly abnormal or mild diseaserdquoldquomoderately abnormal or moderate diseaserdquo or ldquose-verely abnormal or severe diseaserdquo rather than origi-nal grading system proposed in Table 3 Normally the

amplitude at the calf exceeds that at the thigh Thiscalf augmentation occurs because of the differences inmuscle mass and cuff volumes between the thigh andthe calf Essentially although the actual volume

Figure 3

These PVRs waveforms demonstrate mild inflow disease Because the thigh tracings are abnormal bilaterally this likely representsaortoiliac disease There is also outflow disease present bilaterally as the waveform contour and amplitude worsen distally

Figure 4

The left leg in this PVR study demonstrates superficial femoral artery disease as indicated by the presence of a normal thigh waveformand abnormal calf and ankle tracings The right leg is within normal limits


change is greater within the thigh the measured pres-sure change is diluted and reflected as decreased am-plitude

The PVR amplitude is universally affected by exer-cise In normal patients the amplitude increases aftera standard exercise protocol as a result in the in-creased blood flow to the limb In patients with sig-nificant arterial disease there is diminished amplitudeafter exercise There is a definite correlation with thedegree of ischemia as measured by the walking dis-tance and the fall in the PVR amplitude

The contour of the PVR is very important in deter-mining the arterial status of a limb A normal PVR willdemonstrate a sharp systolic upstroke that risesquickly to a peak (Figure 1) The waveform thencurves downward toward the baseline and usuallydisplays a prominent dicrotic notch midway betweenthe peak and the baseline This dicrotic notch or waverepresents the reverse flow component of the normalperipheral arterial pulse If the dicrotic notch is pre-sent this in essence excludes the existence of signifi-

cant proximal disease If improper pressure is main-tained within the cuffs the pulse contour can be dis-torted In the presence of significant arterial occlusivedisease the upstroke is less steep the peak becomesrounded and delayed the downslope bows awayfrom the baseline and the reflected dicrotic wave isabsent As the disease progresses the rise and fall ofthe waveform becomes nearly equal and the overallamplitude of the curve decreases

In the presence of aortoiliac disease the thigh wave-form may lose the dicrotic notch and become slightlyrounded with a decrease in amplitude The waveformcontours at all levels will be abnormal although theamplitude of the calf PVR will remain augmentedcompared with the thigh The ankle waveform will besimilar to the thigh If the thigh waveform in one limbis abnormal while the contralateral thigh waveform isnormal this represents iliofemoral disease becauseaortoiliac disease would impact both thigh waveforms(Figure 2)

In a patient with combined inflow and outflow dis-

Figure 5

These PVR waveforms represent distal tibial level disease The thigh calf and ankle tracings demonstrate good pulsatility however thewaveforms flatten out at the transmetatarsal level


ease the thigh will be abnormal as described in thepreceding paragraph (Figure 3) The calf and anklewaveforms will be reduced in amplitude comparedwith the thigh The contour will be blunted with aprolonged upstroke at all levels

A patient with superficial femoral artery diseasewill display a normal thigh waveform providing thedisease is within the mid to distal portions of thisvessel (Figure 4) The calf waveform will be abnormalwith a blunted contour and decreased amplitude Theankle waveforms will look similar in contour to thecalf but may have a slightly lower amplitude

In the presence of more distal disease the more dis-tal waveforms will be affected If the popliteal artery isdiseased calf and ankle tracings will be affected Ifonly tibial level disease exists the ankle level PVR willbe abnormal with the thigh and calf tracings beingnormal With very distal tibial level disease the thighcalf and ankle waveforms will be normal but those atthe transmetatarsal level will be abnormal (Figure 5)This level of disease is commonly seen in diabetic pa-tients

Plethysmographic waveforms provide a reliable in-dicator of global arterial perfusion The PVR wave-forms and segmental pressures are complimentarytests and results should be evaluated concomitantlyIf a discrepancy exists possible sources of errorshould be investigated If the PVR waveforms indicatedisease but ankle pressures are normal or elevated thepossibility of calcified vessels should be consideredCuff placement should always be checked to rule outany occurrences of cuff artifact

Conclusion

More sophisticated equipment may provide greaterdetail than the simple indirect tests of segmental pres-sures and PVRs However the cost of obtaining thisadditional information must be taken into consider-ation Segmental pressures and plethysmographicwaveforms are quick and reliable methods to detectarterial disease Results from these modalities can helpdirect the care and management of patients withsymptoms of peripheral arterial disease

References

1 Nielsen PE Bell G Lassen NA The measurement of digitalsystolic blood pressure by strain-gauge technique Scand J Clin LabInvest 197229371ndash379

2 Nielsen PE Poulsen NL Gyntelberg F Arterial blood pressurein the skin measured by a photoelectric probe and external counterpressure Vasa 1973265ndash74

3 Manning DM Kuchirka C Kaminski J Miscuffing Inappro-priate blood pressure cuff application Circulation 198368763ndash766

4 Kirkendall WM Feinleib M Freis ED Mark AL Recommen-dations for human blood pressure determinations by sphygmoma-nometers Subcommittee of the AHA Postgraduate Education Com-mittee Circulation 198062(5)1146Andash1155A

5 Gundersen J Segmental measurements of systolic blood pres-sure in the extremities including the thumb and the great tow ActaChir Scand Suppl 19724261ndash90

6 Hirai M Schoop W Hemodynamic assessment of the iliac dis-

ease by proximal thigh pressure and Doppler femoral flow velocityJ Cardiovasc Surg 198425365ndash369

7 Barnes RW Wilson MR Doppler Ultrasound Evaluation of Pe-ripheral Arterial Disease A Programmed Audiovisual Instruction IowaCity IA University of Iowa 1976

8 Burnham CB Segmental pressures and Doppler velocity wave-forms in the evaluation of peripheral arterial occlusive disease JVasc Technol 199418249ndash255

9 Bridges RA Barnes RW Segmental limb pressures InKempszinski RF Yao JST eds Practical Noninvasive Vascular Diag-nosis 1s t ed Chicago Year Book Medical Publishers 1982 pp 79ndash92

10 Carter SA Clinical measurements of systolic pressures inlimbs with arterial occlusive disease JAMA 19692071869ndash1874

11 Carter SA Response of ankle systolic pressure to leg exercisein mild or questionable arterial disease N Engl J Med 1972287578ndash582

12 Lorentsen E Calf blood pressure measurements the applica-bility of a plethysmographic methods and the result of measure-ments during reactive hyperemic Scan J Clin Lab Invest 19733169ndash77

13 Fronek A Coel M Bernstein EF The importance of combinedmultisegmental pressure and Doppler flow velocity studies in thediagnosis of peripheral arterial occlusive disease Surgery 197884840ndash847

14 Raines JK Darling RG Buth J Brewster DC Austen WGVascular laboratory criteria for the management of peripheral vas-cular disease of the lower extremities Surgery 1976l7921ndash29

15 Yao JST New techniques in objective arterial evaluation ArchSurg 1973106600ndash604

16 Fronek A Johansen KH Dilley RB Bernstein EF Noninvasivephysiologic tests in the diagnosis and characterization of peripheralarterial occlusive disease Am J Surg 1973126205ndash214

17 Rutherford RB Lowenstein DH Klein MF Combining seg-mental systolic pressures and plethysmography to diagnose arterialocclusive disease of the legs Am J Surg 1979138211ndash218

18 Carter SA Indirect systolic pressure and pulse waves in ar-terial occlusive disease of the lower extremities Circulation 196837624ndash637

19 Yao JST Hobbs JT Irvine WT Ankle systolic pressure mea-surements in arterial disease affecting the lower extremities Br JSurg 196956676ndash679

20 Osmundson PJ Chesebro JH OrsquoFallon WM Zimmerman BRKazmier FJ Palumbo PJ A prospective study of peripheral occlu-sive arterial disease in diabetes II Vascular laboratory assessmentMayo Clin Proc 198156223ndash232

21 Yao JST Hemodynamic studies in peripheral arterial diseaseBr J Surg 197057761ndash766

22 Sumner DS Strandness DE The relationship between calfblood flow and ankle blood pressure in patients with intermittentclaudication Surgery 196965763ndash771

23 Johnston KW Hosang MY Andrews DF Reproducibility ofnoninvasive vascular laboratory measurements of the peripheralcirculation J Vasc Surg 19876147ndash151

24 Cutajar CL Marston A Newcombe JF Value of cuff occlusionpressures in assessment of peripheral vascular disease BMJ 19732392ndash395

25 Pascarelli EF Bertrand CA Comparison of blood pressures inthe arms and legs N Engl J Med 1964270693ndash698

26 Strandness DE Jr Bell JW Peripheral vascular disease diag-nosis and objective evaluation using a mercury strain gauge AnnSurg 1965161(Suppl 4)1ndash35

27 Allen JS Terry HJ The evaluation of an ultrasonic flow de-tector for the assessment of peripheral vascular disease CardiovascRes 19693503ndash509

28 Raines JK Jaffrin MY Rao S A noninvasive pressure pulerecorder development and rationale Med Instrum 19737245ndash250

29 Darling RC Raines JK Brener BJ Austen WG Quantitativesegmental pulse volume recorder a clinical tool Surgery 197272873ndash877

30 Buckley CJ Darling RC Raines JK Instrumentation and ex-amination procedures for a clinical vascular laboratory Med In-strum 19759181ndash185


within either the posterior tibial artery or the dorsalispedis artery While listening to the flow signal theankle cuff is inflated above the brachial systolic pres-sure until the flow signal is no longer heard The cuffsshould continue to be inflated 20ndash30 mmHg beyondthe pressure at which the last audible signal was ob-tained8 This is done to ensure complete closure of theartery The cuff is then slowly deflated until the Dopp-ler signal returns The rate of deflation should be ap-proximately 2ndash4 mmHg per sec This will allow for aprecise measurement of the systolic pressure Aftermeasurement of the ankle pressure the calf and thenthe thigh pressures are recorded

If the Doppler signal is absent at the ankle level theankle cuff can be removed and the mid to distal tibialarteries can be examined with the Doppler stetho-scope If a flow signal is obtained within the mid-calfthis can be use to determine the calf and thigh pres-sures If no signal can be appreciated from the tibiallevel the popliteal artery is then examined A Dopplersignal from the popliteal fossa can be used to deter-mine the thigh pressure

Interpretation

Because ankle systolic pressures are compared withthe brachial artery pressures it is important to haveaccurate measurements of brachial artery pressureThe right and left brachial pressures should be equalIf these pressures differ by more than 20 mmHg anabnormality exists9 The arm with the lower pressurelikely contains a hemodynamically significant obstruc-tion within the subclavian artery However furthertesting would be needed to determine the exact loca-tion of such an obstruction Thus the higher of the twobrachial artery pressures should be used for calcula-tions of the ABI

As stated earlier both the posterior tibial and dor-salis pedis arteries can be used to determine anklepressure The pressure measured at these two arteriesshould not differ by more than 10 mmHg and varia-tions greater than 15 mmHg suggest a proximal ob-struction in the artery with the lower pressure10 Thehigher pressure reading is the value used in the cal-culation of the ABI The ankle systolic pressure nor-mally is greater than the brachial systolic pressure by12ndash24 mmHg11 12 This occurs as a result of an aug-mentation in the pulse pressure as blood travels to the

periphery This augmentation is due to less elastic dis-tal arterial walls and reflections of the pressure wavefrom distal branch points and the peripheral vascularbed

One of the most common technical errors that canoccur in the measurement of ankle pressures is due tothe presence of medial calcification13 14 Calcificationcan result in falsely elevated pressure measurementsor the inability to completely occlude the arterial flowsignal Medical calcification is frequently encounteredin diabetic patients or patients with chronic renal fail-ure Calcific vessels are suspected when the anklepressures exceed 300 mmHg Although the medial cal-cification has a pronounced affect on ankle pressuremeasurements it does not have an impact on plethys-mographic or Doppler waveforms

Ankle Brachial Index

Pressure measured at any point along the vascularsystem is going to vary because the dynamic pressuresupplied by the heart varies Because of this calculat-ing the ABI can normalize the ankle pressure The ABIis simply the ankle systolic pressure divided by thebrachial systolic pressure The range for normal ABI isbetween 10 and 1115ndash18 In the presence of significantarterial disease the ABI is typically less than 1015 18

However it is possible for a patient to have arterialdisease yet have a resting ABI of 10 or greater18 19

Other studies have shown that only rarely does anindividual without arterial disease have an ABI of lessthan 09220 If a patient has ldquonormalrdquo resting ABIs butdescribes symptoms associated with exercise this pa-tient should undergo exercise testing to detect the pre-sent of a subcritical stenosis

In early work by Yao21 the degree of functionalimpairment within subjects was compared with themeasured ABI He identified the following groups nosymptoms ABI 10 claudication ABI = 05ndash10 restpain ABI = 025ndash050 impeding tissue loss ABI 025Even though some overlap occurred it is clear thatwith increasing severity of symptoms there is a pro-gressive decrease in the ABI It has also been observedthat differences in the ABI occur with increasing num-ber of diseased segments of the arterial tree22 An ABIof 05 is found in patients with only a single levelobstruction whereas an ABI of lt05 is often associatedwith multilevel disease Within an individual themeasurement of the ABI is fairly stable between ex-aminations providing there is no significant change inthe degree of disease A change in the ABI of 015from one examination to the next has been shown tobe a good indicator of increasing severity of disease23

Segmental Pressures

Although an ABI will identify those patients withsignificant arterial disease it does not specify the seg-ments involved By measuring the pressure gradientsdown the limb additional information can be ob-tained The systolic pressure measured with a highthigh cuff is normally 30ndash50 mmHg greater than thebrachial systolic pressure24 There is a great deal of

Table 1

Recommended Cuff Bladder Width for Lower Limb Pressures inthe Average Adult

Cuff Level Cuff Width (in cm)

Upper thigh 11Lower thigh 19Single contoured thigh cuff 22Calf 12Ankle 10ndash12Transmetatarsal 7ndash8Toe 25ndash3




Plethysmography





Interpretation


Table 2




Table 3


PVR Category






Figure 1


Figure 2





Figure 3


Figure 4









Figure 5







Conclusion


References



































Plethysmography





Interpretation


Table 2




Table 3


PVR Category






Figure 1


Figure 2





Figure 3


Figure 4









Figure 5







Conclusion


References

































Figure 1


Figure 2





Figure 3


Figure 4









Figure 5







Conclusion


References



































Figure 3


Figure 4









Figure 5







Conclusion


References







































Figure 5







Conclusion


References





































Conclusion


References

































segmental pressure measurement and plethysmography · pdf filesegmental pressure measurement...

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