Comparative diagnostic test characteristics of oscillometric and Doppler ultrasonographic methods in the detection of systolic hypertension in dogs

Comparison of test characteristics allows a clinician to choose the optimal diagnostic test method for an individual patient. This study assessed the comparative test characteristics of noninvasive (NI) blood pressure measurement methods (oscillometric and Doppler) and used this information to develop optimal cutoff values for diagnosis of systolic hypertension in dogs by these NI methods. Simultaneous NI (oscillometric or Doppler methods) and invasive (arterial puncture [AP]) systolic blood pressure (SBP) measurements were obtained prospectively from normal dogs and dogs suspected of having systemic hypertension based on clinical signs. Oscillometric SBP readings were obtained from the distal hind limb (Osc-L, n = 54) or the proximal tail (T. n = 27). Doppler BP measurements were obtained using a forelimb cuff (n = 57). AP-SBP was categorized as hypertensive if > or = 160 mmHg, and sensitivity (Se). specificity (Sp), and likelihood ratios (LR) were calculated for diagnostic cutoff values ranging from 130 to 220 mmHg. Receiver operator characteristic (ROC) curves were analyzed to determine optimal cutoff values for diagnosis of AP-SBP > or = 160 mmHg. Optimal NI SBP cutoff values considered to reflect AP values > or = 160 mmHg were: Osc-L = 160 mmHg (Se: 65%, Sp: 85%. LR = 4.33: 1), Osc-T = 150 mmHg (Se: 84%, Sp: 75%, LR = 3.36: 1), and Doppler = 160 mmHg (Se: 71%,     

Doppler Ultrasonographic, Oscillometric Sphygmomanometric, and Photoplethysmographic Techniques for Noninvasive Blood Pressure Measurement in Anesthetized Cats

Blood pressure (BP) measurements obtained using 3 indirect BP measuring instruments, a Doppler ultrasonic flowmeter, an oscillometric device, and a photoplethysmograph, were compared with direct arterial pressure measurements in 11 anesthetized cats. The standard deviation of the differences (SOD) between direct and indirect pressure measurements were not significantly different from each other ( P <.01), and ranged from 10.82 to 24.32 mm Hg. The high SDD values indicate that indirect BP estimates obtained with all these devices must be interpreted cautiously in individual patients. The mean errors (calculated as the sum of the differences between direct and indirect pressure measurements divided by the number of observations) of the 3 indirect devices were significantly different for systolic (SAP), diastolic (DAP), and mean (MAP) arterial pressures ( P <.05). The Doppler and photoplethysmographic devices had the highest overall accuracy, as indicated by mean error values of less than 10 mm Hg. Correlation coefficients varied from .88 to .96 for the Doppler flowmeter, and from .85 to .94 for the photoplethysmograph; for both devices, the regression line slopes were close to unity. The Doppler flowmeter detected a pulse under all experimental conditions. The photoplethysmograph was also efficient in obtaining BP measurements, obtaining over 90% of SAP, DAP, and MAP readings attempted. The oscillometric device was the least accurate, with mean error values varying from 10 to 22 mm Hg. Correlation coefficients were high (.90 to .94) for this device, but the slopes of the regression lines were 0.7 to 0.8, indicating a trend for increased error at higher BP. The oscillometric device tended to underestimate BP by increasing amounts as the BP increased. The oscillometric device was the least efficient device for obtaining BP measurements ( P <.01).     

Evaluation of a new oscillometric blood pressure monitor in isoflurane-anesthetized dogs

Objective This study was conducted to evaluate the performance of a new veterinary oscillometric noninvasive blood pressure (NIBP) monitor in anesthetized dogs. Study design Assessment was made to determine how closely indirect measurements were associated with direct measurements, and if there were statistically significant differences between the measurements by site. Animals Six mongrel dogs weighing 27.8 ± 2.9 kg. Methods Dogs were anesthetized with thiopental and maintained with isoflurane, which was delivered with controlled ventilation. Direct pressure measurements were obtained via a percutaneously placed arterial catheter. A range of systolic arterial pressures (SAP) were achieved by changing the isoflurane concentrations. Sites of cuff placement for indirect measurements were identified as metacarpus, metatarsus, and anterior tibial. Results At pressures below 80 mm Hg, indirect systolic measurements averaged 4 ± 3 mm Hg, higher than the direct values. At normal and high levels, indirect systolic measurements underestimated direct values by 18 ± 6 and 23 ± 6 mm Hg, respectively. Diastolic and mean pressure measurements followed the same trend, with indirect values being lower than the direct arterial pressures. Systolic, diastolic and mean arterial pressure measurements differed by cuff‐placement site. Conclusions When analyzed by site and level, indirect systolic and mean arterial blood pressures during hypotension were essentially the same as direct pressures. However, at pressures within the normal or high range, indirect measurements underestimated the direct pressures. Clinical relevance Noninvasive blood pressure measurements with a new oscillometric monitor provided an excellent means of detecting arterial hypotension in anesthetized dogs. The metatarsal site for cuff placement was slightly better than the metacarpal or anterior tibial site, considering that the regression line was closest to complete equality between the indirect and direct measurements for SAP.     

Evaluation of an indirect oscillometric blood pressure monitor in normotensive and hypotensive anesthetized dogs

Objective – To determine the accuracy and precision of an oscillometric noninvasive blood pressure device as a predictor of invasive direct blood pressure in healthy anesthetized hypotensive and normotensive dogs. Design – Prospective observational study. Setting – University teaching hospital. Animals – Eight crossbred adult dogs. Interventions – Anesthesia was induced with propofol and maintained with isoflurane. A catheter was placed in the dorsal pedal artery to record systolic, mean, and diastolic arterial blood pressures (aSAP, aMAP, and aDAP, respectively). The noninvasive blood pressure device cuff was placed around the contralateral front limb to record noninvasive systolic, mean, and diastolic blood pressure (nSAP, nMAP, and nDAP). Two states of blood pressure (BP) were studied: baseline state was established by keeping end‐tidal isoflurane concentration at 1.2±0.1%. The hypotensive state was achieved by maintaining the same isoflurane concentration while withdrawing approximately 40% of the animal's blood volume until aMAP was stable at approximately 40 mm Hg. At the end of the study, blood was returned to the animal and it was allowed to recover from anesthesia. Measurements and Main Results – Agreement between the direct and indirect BP measurements was determined by the Bland‐Altman method. The SAP and MAP but not DAP bias varied significantly between each BP state. Normotensive absolute biases (mean [SD]) for SAP, MAP, and DAP were ?14.7 mm Hg (15.5 mm Hg), ?16.4 mm Hg (12.1 mm Hg), and ?14.1 mm Hg (15.8 mm Hg), respectively. Absolute biases during the hypotensive state for SAP, MAP, and DAP were ?32 mm Hg (22.6 mm Hg), ?24.2 mm Hg (19.5 mm Hg), and ?16.8 mm Hg (17.2 mm Hg), respectively. Conclusion – The oscillometric device was not reliably predictive of intra‐arterial BP during hypotension associated with acute hemorrhage.     

Evaluation of indirect blood pressure monitoring in awake and anesthetized red-tailed hawks (Buteo jamaicensis): effects of cuff size, cuff placement, and monitoring equipment

ObjectiveTo compare Doppler and oscillometric methods of indirect arterial blood pressure (IBP) with direct arterial measurements in anesthetized and awake red-tailed hawks.Study designProspective, randomized, blinded study.AnimalsSix, sex unknown, adult red-tailed hawks.MethodsBirds were anesthetized and IBP measurements were obtained by oscillometry (IBP-O) and Doppler (IBP-D) on the pectoral and pelvic limbs using three cuffs of different width based on limb circumference: cuff 1 (20–30% of circumference), cuff 2 (30–40%), and cuff 3 (40–50%). Direct arterial pressure measurements were obtained from the contralateral superficial ulnar artery. Indirect blood pressure measurements were compared to direct systolic arterial pressure (SAP) and mean arterial pressure (MAP) during normotension and induced states of hypotension and hypertension. Measurements were also obtained in awake, restrained birds. Three-way anova, linear regression and Bland–Altman analyses were used to evaluate the IBP-D data. Results are reported as mean bias (95% confidence intervals).ResultsThe IBP-O monitor reported errors during 54% of the measurements. Indirect blood pressure Doppler measurements were most accurate with cuff 3 and were comparable to MAP with a bias of 2 (?9, 13 mmHg). However, this cuff consistently underestimated SAP with a bias of 33 (19, 48 mmHg). Variability in the readings within and among birds was high. There was no significant difference between sites of cuff placement. Awake birds had SAP, MAP and diastolic arterial pressure that were 56, 43, and 38 mmHg higher than anesthetized birds.Conclusions and clinical relevanceIndirect blood pressure (oscillometric) measurements were unreliable in red-tailed hawks. Indirect blood pressure (Doppler) measurements were closer to MAP measurements than SAP measurements. There was slightly better agreement with the use of cuff 3 on either the pectoral or pelvic limbs. Awake, restrained birds have significantly higher arterial pressures than those under sevoflurane anesthesia.     

Comparison of high definition oscillometric and Doppler ultrasound devices with invasive blood pressure in anaesthetized dogs

Objective To use the American College of Veterinary Internal Medicine (ACVIM) validation criteria to evaluate the performance of high definition oscillometric (HDO) and Doppler blood pressure measurement techniques against invasive blood pressure measurements in anaesthetized dogs. Study design Prospective clinical study. Animals Twenty client‐owned dogs. Materials and Methods Invasive blood pressure was measured using a catheter inserted into a pedal artery and an electronic transducer. The sites of cuff placement for the HDO measurements were the mid antebrachium or the proximal tail and, for the Doppler technique, the distal tibia. Agreement between invasive and non‐invasive blood pressure measurements was estimated by the Bland–Altman method. Results Only 10% and 34% of Doppler measurements were within 10 and 20 mmHg of invasive blood pressure values, respectively. The Doppler device failed to meet the ACVIM validation criteria for blood pressure measurement devices. The best agreement between HDO and invasive blood pressure measurement technique was observed for mean arterial blood pressure (MAP); 67% and 95% of readings were within 10 and 20 mmHg of invasive blood pressure values respectively. In addition, 52% and 87% of diastolic arterial blood pressure (DAP) measurements were within 10 and 20 mmHg of invasive readings. High definition oscillometric readings did not meet ACVIM recommended limits for SAP. Conclusion and clinical relevance The Doppler technique overestimated and the HDO device showed limited agreement with invasive blood pressure measurement in anaesthetized dogs. High definition oscillometry met most of the ACVIM requirements for MAP and DAP while the Doppler technique did not.     

Comparison of Doppler,oscillometric, auricular and carotid arterial blood pressure measurements in isoflurane anesthetized New Zealand white rabbits

ObjectiveTo assess agreement between carotid arterial pressure and auricular arterial, thoracic limb Doppler or thoracic limb oscillometric blood pressure measurements.Study designProspective experimental study.AnimalsSix adult New Zealand white rabbits.MethodsRabbits were anesthetized with isoflurane in oxygen at 1, 1.5 and 2 MAC on two separate occasions. Catheters in the auricular and the contralateral external carotid artery were connected to calibrated pressure transducers via non-compliant tubing. Inflatable cuffs of width equal to approximately 40% of the limb circumference were placed above the carpus on both thoracic limbs with a Doppler transducer placed distal to the cuff on one. Systolic (SAP) and mean (MAP) arterial blood pressure measurements were obtained at each dose, on each occasion. Agreement between measurement techniques was evaluated by repeated measures Bland Altman analysis with carotid pressure as the reference. Variation in bias over the measurement range was evaluated by regression analysis.ResultsCarotid MAP and SAP ranged from 20 to 65 mmHg and 37 to 103 mmHg respectively. Bias and 95% limits of agreement for auricular and oscillometric MAP were 7 (0–14) and ?5 (?21–11) mmHg, respectively, and for auricular, oscillometric and Doppler SAP were 23 (8–37), ?2 (?24–20) and 13 (?14–39) mmHg, respectively. Bias varied significantly over the measurement range (p < 0.001) for all three SAP techniques but not for MAP measurements.Conclusions and clinical relevanceLimits of agreement for all measurements were large but less so for MAP than SAP. Variation in bias with SAP should be considered when using these measurements clinically.     

A clinical evaluation of an oscillometric blood pressure monitor on anesthetized horses

The accuracy of an oscillometric blood pressure monitor (Vet/BP 6000, Sensor Devices, Inc., Waukesha, WI) was assessed in 13 anesthetized horses undergoing a variety of clinical procedures. The oscillometric blood pressure measurements using a cuff placed around the base of the tail were compared to simultaneously recorded direct pressure readings. One hundred nine sets of blood pressure measurements were recorded. In addition the pulse rates, as determined by digital palpation and oscillometric measurement, the time required for an oscillometric measurement, and the number of attempts required by the oscillometric unit were recorded. The average difference between the direct and oscillometric blood pressures were 18, 9, and 11 mmHg for the systolic, diastolic and mean arterial blood pressures, respectively. The oscillometric and direct pressure measurements showed significant correlation with a correlation coefficient of 0.93 for the mean arterial pressure. The oscillometrically determined pulse rate (average-33 pulses/min) was significantly different than the pulse rate determined by palpation (average-33.4 pulses/minute) but the difference was less than one. The average time required for a determination was 69 seconds and the average number of attempts required was 1.02 per determination.     

Indirect measurement of systemic blood pressure in conscious dogs in a clinical setting

The present study compared 2 indirect methods, Doppler sphygmomanometry and oscillometry, for measurement of the systemic blood pressure level in 100 conscious, client-owned dogs in a clinical setting on 2 separate occasions. The mean systemic blood pressure values, measured by Doppler sphygmomanometry on 2 separate occasions, were 156 +/- 38.2 mmHg and 150 +/- 34.1 mmHg, respectively. Using oscillometry, the mean systolic blood pressure values were 138 +/- 36.9 mm Hg and 133 +/- 33.5 mm Hg on 2 separate occasions. There were significant differences between the systemic blood pressure readings for both methods on the same occasion (P<0.001). The coefficients of variance from 5 consecutive measurements in the same dog obtained by Doppler sphygmomanometry on the 2 separate occasions were 4.1 +/- 3.2% and 3.1 +/- 1.7%; that of the oscillometric method on the 2 separate occasions were 18.7 +/- 11.3% and 17.2 +/- 12.5%. The coefficients of variance of these 2 methods were statistically different on each occasion (P<0.001). Five consecutive systemic blood pressure readings were obtained for each dog within 6 min on both occasions using Doppler sphygmomanometry. More than 15 min was required to complete 5 consecutive systemic blood pressure readings by oscillometric sphygmomanometry for all dogs on each occasion. The results of this study indicate that Doppler sphygmomanometry provides more efficient and precise measurements of the systemic blood pressure level than oscillometric testing in conscious dogs in a clinical setting.     

Evaluation of an oscillometric blood pressure monitor for use in anesthetized sheep

ObjectiveTo determine the accuracy of an oscillometric blood pressure monitor in anesthetized sheep.Study designProspective study.AnimalsTwenty healthy adult sheep, 11 males and nine females, weighing 63.6 ± 8.6 kg.MethodsAfter premedication with buprenorphine or transdermal fentanyl, anesthesia was induced with ketamine‐midazolam and maintained with isoflurane and ketamine, 1.2 mg kg^?1 hour^?1, ± lidocaine, 3 mg kg^?1 hour^?1. Invasive blood pressure measurements were obtained from an auricular arterial catheter and noninvasive measurements were from a cuff on the metatarsus or antebrachium. Simultaneous invasive and noninvasive measurements were recorded over a range (55–111 mmHg) of mean arterial pressures (MAP). Isoflurane concentration was increased to decrease MAP and decreasing the isoflurane concentration and infusing dobutamine achieved higher pressures. Invasive and noninvasive measurements were compared.ResultsCorrelation (R²) was good between the two methods of measurement (average of three consecutive readings) for systolic (SAP) (0.87), diastolic (DAP) (0.86), and mean (0.90) arterial pressures (p < 0.001). Bias ± SD between noninvasive and invasive measurements for SAP was 3 ± 8 mmHg, for DAP was ?10 ± 7 mmHg, and MAP was ?7 ± 6 mmHg. There was no significant difference between the average of three measurements and use of the first measurement. Correlations using the first measurement were SAP (0.82), DAP (0.84), and MAP (0.89). Bias ± SD for SAP was 3 ±10 mmHg, for DAP was ?11 ± 7 mmHg, and MAP was ?7 ± 6 mmHg. The oscillometric monitor slightly overestimated SAP and underestimated DAP and MAP for both average values and the first reading.Conclusions and clinical relevanceThis oscillometric model provided MAP measurements that were acceptable by ACVIM standards. MAP measurements with this monitor were lower than those found with the invasive technique so a clinical diagnosis of hypotension may be made in sheep that are not hypotensive.     

A comparative study of invasive and oscillometric methods of arterial blood pressure measurement in the anesthetized rabbit

INTRODUCTION: The aim of this project was to evaluate the reliability and accuracy of direct, using the central ear artery (CEA), and oscillometric, using limb-cuffs, methods of arterial blood pressure (AP) measurement in the anesthetized rabbit. METHODS: New Zealand rabbits were anesthetized using a xylazine-ketamine-isoflurane protocol. Using the abdominal aorta (ABA) as direct "gold standard" for AP measurements, ABA pressure readings, via femoral artery catheterization, were compared with those made simultaneously from the ascending aorta after median sternotomy. Thereafter, direct CEA as well as forelimb-(FL) and hindlimb-(HL) cuff oscillometric readings were compared with those made simultaneously from ABA. RESULTS: The blood pressure in the ABA correlated with that from ascending aorta. Furthermore, CEA correlated with the ABA readings. Nevertheless, at high pressures, their divergence from "true" pressure tended to increase. Oscillometric readings at the FL site correlated well with "true" pressure while those at the HL site did not. Their divergence tended to increase at high pressures when using the FL site, while it varied when using the HL site. The accuracy of measurements was moderate for the FL site while poor for the HL site. DISCUSSION: Our results suggest that the CEA can be readily used with high reliability and accuracy for direct AP measurements in the anesthetized rabbit. On the other hand, the FL-cuff oscillometric method should only be used for the evaluation of AP at low and normal pressure ranges.     

Agreement between direct, oscillometric and Doppler ultrasound blood pressures using three different cuff positions in anesthetized dogs

ObjectiveTo evaluate the agreement between invasive blood pressure (IBP) and Doppler ultrasound blood pressure (DUBP) using three cuff positions and oscillometric blood pressure (OBP) in anesthetized dogs.Study designProspective study.AnimalsNine adult dogs weighing 14.5–29.5 kg.MethodsThe cuff was placed above and below the tarsus, and above the carpus with the DUBP and above the carpus with the OBP monitor. Based on IBP recorded via a dorsal pedal artery catheter, conditions of low, normal, and high systolic arterial pressures [SAP (mmHg) <90, between 90 and 140, and >140, respectively] were induced by changes in isoflurane concentrations and/or dopamine administration. Mean biases ± 2 SD (limits of agreement) were determined.ResultsAt high blood pressures, regardless of cuff position, SAP determinations with the DUBP underestimated invasive SAP values by more than 20 mmHg in most instances. With the DUBP, cuff placement above the tarsus yielded better agreement with invasive SAP during low blood pressures (0.2 ± 16 mmHg). The OBP underestimated SAP during high blood pressures (?42 ± 42 mmHg) and yielded better agreement with IBP for mean (MAP) and diastolic (DAP) arterial pressure measurements [overall bias: 2 ± 15 mmHg (MAP) and 0.2 ± 16 mmHg (DAP)].ConclusionsAgreement of SAP determinations with the DUBP is poor at SAP > 140 mmHg, regardless of cuff placement. Measurement error of the DUBP with the cuff placed above the tarsus is clinically acceptable during low blood pressures. Agreement of MAP and DAP measurements with this OBP monitor compared with IBP was clinically acceptable over a wide pressure range.Clinical relevanceWith the DUBP device, placing the cuff above the tarsus allows reasonable agreement with IBP obtained via dorsal pedal artery catheterization. Only MAP and DAP provide reasonable estimates of direct blood pressure with the OBP monitor evaluated.     

Indirect oscillometric and direct blood pressure measurements in anesthetized and conscious neonatal foals

Objective: To investigate the agreement between indirect oscillometric and direct blood pressure measurement in the equine neonate. Design: Prospective observational study. Setting: University Veterinary Teaching Hospital. Animals: Ten crossbred foals of 30–46 hours of age. Interventions: Six animals (Group 1) were anesthetized. Four animals (Group 2) were restrained on a mat. All animals were instrumented with a catheter in the greater metatarsal artery and an oscillometric blood pressure cuff over the coccygeal artery. Blood pressure was varied with dobutamine, phenylephrine, nitroprusside, and increased depth of anesthesia (Group 1) or dopamine (Group 2). Measurements and main results: Simultaneous direct and indirect blood pressure measurements were obtained from the greater metatarsal artery and the coccygeal artery, respectively. There was good agreement between the 2 methods for mean and diastolic blood pressures in both groups, but not for systolic pressure. The agreement was best in mean blood pressure of anesthetized foals (mean bias –1.07; limits of agreement – 9.39, 7.25 mmHg). Conclusions: Indirect oscillometry appears to be an acceptable method for measuring mean arterial blood pressure in both anesthetized and conscious neonatal foals, and may be a valid method of monitoring critically ill foals.     

RESEARCH PAPER: Comparison of an implantable telemetry device and an oscillometric monitor for measurement of blood pressure in anaesthetized and unrestrained green iguanas (Iguana iguana)

Objective The objective of this study was to compare an implanted direct blood pressure monitor and a non‐invasive oscillometric unit for use in anesthetized and awake green iguanas. Study design Prospective experimental trial. Animals Four male and four female adult green iguanas (Iguana iguana) weighing 1833 ± 534 g. Methods For each animal, the carotid artery was surgically exposed and the catheter tip of the pressure transducer was placed in the aortic arch. Non‐invasive blood pressure was measured using a cuff over the left femoral region. Pulse rate, respiratory rate and arterial blood pressure (ABP) measurements were taken every 5 minutes. Direct ABP measurements consisted of recording numerical values and graphic output. Simultaneous direct and indirect measurements were repeated in awake animals. Results The oscillometric device failed to provide a reading in over 80% of attempts, and failed to provide readings that correlated with direct measurements. The implanted direct transducer was capable of detecting blood pressures throughout all ABP ranges examined. Conclusions The implantable transducer was a reliable means of determining blood pressure in this study, while the oscillometric device was unreliable and often failed to provide any reading. Clinical relevance We do not recommend using the oscillometric device as described in a research or clinical setting for green iguanas. The advantages of an implantable device include the ability to monitor awake and anesthetized subjects remotely and continuously. These monitors are small, biocompatible and function across a wide range of ABP.     

Evaluation of Transmittance and Reflectance Pulse Oximetry in a Canine Model of Hypotension and Desaturation

Ten, anesthetized dogs were instrumented with three pulse oximeter probes; two lingual transmittance probes and one rectal reflective probe. Arterial oxygen desaturation was produced by decreasing the inspired oxygen concentration. Hypotension was produced with an infusion of nitroprusside. Simultaneous pulse oximeter readings (SpO₂) were compared to co-oximeter measured arterial saturation (SaO₂) collected over a range of SaO₂ (50–100%) and mean arterial pressures (40–100mmHg). Each of the monitors and means of evaluating SpO₂ studied provided accurate SpO₂ measurements over a range of mean arterial pressure from 40–100mmHg. All of the monitors tested tended to overestimate the SaO₂ when the arterial saturation was less than 70%.     

Evaluation of oscillometric and Doppler ultrasonic methods of indirect blood pressure estimation in conscious dogs

To assess the accuracy and precision of indirect measurements of systemic arterial blood pressure (BP), results obtained with an oscillometric device (BPo) and a Doppler ultrasonic device (BPud) were compared with those obtained by direct radiotelemetry (BPrt) in 12 conscious beagles. The correlation between indirectly obtained and directly measured values for BP parameters ranged widely for the different indirect methods and sites of cuff placement, with R2 between 0.001 and 0.901. Both indirect methods underestimated all BP parameters, the degree of underestimation increasing at higher values for the BP. The highest correlation occurred when estimates were the average of 5 values consecutively obtained with the oscillometric device and cuff placement at the coccygeal artery (R2 = 0.854 for mean BPo, 0.886 for systolic BPo, and 0.901 for diastolic BPo; P < 0.0001 for all parameters) or with the ultrasonic Doppler device at the metatarsal arteries (R2 = 0.810 for systolic BPud; P < 0.0001). Multiple consecutively obtained values are advised, as this approach improves the reliability of indirect BP measurements. The strong correlation between directly measured values and estimates derived as the average of 5 consecutive indirectly obtained values indicates that the latter approach provides a useful estimate of BP in conscious dogs and is likely to be useful in monitoring disease progress and treatment in dogs with abnormal BP.     

A comparison of CAT Doppler and oscillometric Memoprint machines for non-invasive blood pressure measurement in conscious cats

Indirect blood pressure measurements were compared in 28 conscious cats using Doppler and oscillometric blood pressure-measuring devices. Ten cats were used to compare Doppler measurements between two examiners and 18 cats were used to compare Doppler and oscillometric measurements. The Doppler machine obtained systolic and diastolic blood pressure readings in 100% and 51% of attempts, respectively. With the oscillometric machine, systolic and diastolic blood pressure readings were obtained in 52% of the attempts. With the Doppler, measures of mean systolic blood pressure between two examiners were positively correlated, but there was no correlation for diastolic blood pressure measures. When comparing the results obtained by Doppler and oscillometric machines there was no significant difference between mean systolic blood pressure readings, but the oscillometric machine produced significantly higher estimates of diastolic blood pressure. In both cases, the standard deviations for the oscillometric machine were considerably larger than those for the Doppler machine. The first reading of systolic blood pressure obtained with the Doppler machine was an excellent predictor of the mean of five readings, but this was not so for the oscillometric machine. It took less than 5 min to obtain five readings in 37.5% of cases with the Doppler machine but this was true for only 5% of cases with the oscillometric machine. Two cats with ophthalmological lesions consistent with systemic hypertension were identified. In these two patients, systolic blood pressure measurements were between 200 and 225 mmHg when measured by Doppler, and between 140 and 150 mmHg when measured by the oscillometric machine. This suggests that a lower reference range for normal systolic blood pressure values should be used for the oscillometric device.     

Agreement between noninvasive oscillometric and invasive blood pressure measurements in isoflurane-anesthetized guinea pigs (Cavia porcellus)

ObjectiveTo assess the agreement between an oscillometric device and invasive blood pressure (IBP) measurements in anesthetized healthy adult guinea pigs.Study designProspective experimental study.AnimalsA total of eight adult Hartley guinea pigs.MethodsAll animals were anesthetized; a carotid artery was surgically exposed and catheterized for IBP measurements. A size 1 cuff placed on the right thoracic limb was connected to an oscillometric device for noninvasive blood pressure (NIBP) assessment. Concurrent pairs of systolic (SAP), diastolic (DAP) and mean (MAP) arterial pressures were recorded simultaneously with both methods every 3 minutes for 30 minutes. Agreement between IBP and NIBP measurements was determined using the Bland–Altman method, considering the recommended standards for the validation of NIBP measurement devices proposed by the American College of Veterinary Internal Medicine (ACVIM).ResultsThe bias and the 95% limits of agreement were: –14 (–31 to 3) mmHg, –2 (–14 to 10) mmHg and –1 (–13 to 11) mmHg for SAP, DAP and MAP, respectively.Conclusions and clinical relevanceThe oscillometric device used in this study to measure NIBP did not meet ACVIM criteria for validation. It showed good agreement for DAP and MAP but not for SAP measurements. Considering the small size of these animals and the resulting difficulty in performing percutaneous arterial catheterization, this device might be a useful tool to assess MAP and DAP during anesthetic procedures in adult guinea pigs.     

Evaluation of the Doppler ultrasonic method of measuring systolic arterial blood pressure in cats.

The accuracy of the Doppler technique for indirect systolic blood pressure measurement was assessed in 16 anesthetized cats. Eight cats were anesthetized with isoflurane and 8 were anesthetized with halothane. Anesthetic depth and mode of ventilation were varied to obtain a wide range of arterial blood pressure. A Doppler transducer was placed on the palmer surface of the left forelimb over the common digital branch of the radial artery to detect blood flow, and a blood pressure monitoring cuff with a width 37% the limb circumference was placed half way between the elbow and the carpus. To enable direct arterial pressure measurements, the left femoral artery was catheterized and the blood pressure waveforms recorded simultaneously. Systolic blood pressure measured by use of the Doppler ultrasonic technique was significantly lower than that obtained from the femoral artery catheter. Using linear regression, we determined a clinically useful calibration adjustment for Doppler indirect blood pressure measurement in cats: femoral systolic pressure = Doppler systolic pressure + 14 mm of Hg.     

Accuracy of an oscillometric blood pressure monitor during phenylephrine-induced hypertension in dogs

OBJECTIVE: To examine the agreement between direct arterial blood pressure measurements obtained from 2 arteries and indirect blood pressure measurements obtained with an oscillometric blood pressure monitor (OBPM) during normotension and phenylephrine-induced hypertension in dogs. ANIMALS: 16 male Beagles. PROCEDURES: In anesthetized dogs, arterial catheters were placed in the lingual and dorsal pedal arteries for measurement of arterial blood pressure. A blood pressure cuff was placed on either the dog's fore- or hind limb and connected to an OBPM. Systolic, diastolic, and mean arterial blood pressures (SAP, DAP, and MAP, respectively) were recorded from both arteries and the OBPM every 5 minutes for 30 minutes (baseline), during a 30-minute period in which dogs received a phenylephrine infusion IV to induce hypertension, and for 30 minutes after discontinuation of the infusion. Mean differences in blood pressure values and confidence intervals were calculated to compare the indirect and direct measurement techniques. RESULTS: In dogs, oscillometry underestimated SAP during normotension, and the difference between oscillometric and direct measurements increased during hypertension. Oscillometry underestimated DAP, but the difference between oscillometric and direct measurements decreased during hypertension. There was close agreement among techniques for MAP determinations. Biases between direct measurements and OPBM blood pressure values measured from dogs' forelimbs or hind limbs were not significantly different. CONCLUSIONS AND CLINICAL RELEVANCE: In normotensive dogs, oscillometric measurements of MAP and SAP agreed more closely with direct arterial pressure measurements than oscillometric estimates of DAP. Oscillometric measurement of MAP was accurate during both normotension and hypertension in dogs.