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 oscillometric and Doppler ultrasonic devices for blood pressure measurements in anesthetized and conscious dogs

Two non-invasive blood pressure (NIBP) devices (oscillometry and Doppler) were compared to invasive blood pressure using a Bland–Altman analysis, in anesthetized and conscious dogs. When considering the systolic arterial pressure only during general anesthesia, both NIBP devices slightly underestimated the systolic arterial blood pressure however the precision and the limits of agreement for the Doppler were of a greater magnitude. This indicates a worse clinical performance by the Doppler. The performance of both NIBP devices deteriorated as measured in conscious animals. In general, for the oscillometric device, determination of invasive diastolic and mean arterial pressures was better than the invasive systolic arterial pressure. Overall, the oscillometric device satisfied more of the criteria set by the American College of Veterinary Internal Medicine consensus statement. Based upon these results, the oscillometric device is more reliable than the Doppler in the determination of blood pressure in healthy medium to large breed dogs.     

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.     

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.     

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%,     

Indirect measurement of blood pressure using a pulse oximeter in isoflurane anesthetized dogs

Objective: To determine the accuracy of indirect blood pressure (BP) measurements obtained with a pulse oximeter as compared with direct measurements in dogs under isoflurane anesthesia. The Doppler and oscillometric BP monitors were included for comparison. Design: Prospective, experimental study. Animals: Twenty healthy dogs (23 ± 8 kg) anesthetized for research or teaching. Interventions: Dogs were anesthetized with propofol or thiopental and maintained using positive pressure ventilation with isoflurane in 100% O₂. Random adjustment of BP was achieved by inhalant adjustment or dopamine infusion to achieve low (≤85 mmHg), normal (90–120 mmHg), or high systolic BP (≥125 mmHg). Triplicate measurements for BP were taken with direct (dorsal pedal artery), Doppler (forelimb), oscillometric (same forelimb), and plethysmographic (pulse oximeter on tongue) methods. Measurements and main results: Using regression analysis and a modified Bland–Altman's technique, the lowest bias was achieved with the Doppler. Systolic BP readings at low, normal, and high BP were within 10 mmHg of direct recordings 95%, 70%, and 30% of the time for pulse oximetry; 95%, 85%, and 55% of the time for Doppler; 42%, 65%, and 30% of the time for oscillometric determination, respectively. Oscillometric mean BP readings were within 10 mmHg of direct measurements 53%, 60%, and 45% of the time, respectively. Conclusions: The pulse oximeter is an acceptable method for measuring BP in anesthetized dogs if assessment of trends is sufficient. All indirect methods showed greater bias and poorer precision at high BP. The Doppler may be the preferred indirect method.     

Comparison of ultrasonic Doppler flow monitor,oscillometric, and direct arterial blood pressure measurements in ill dogs

Objective – To compare blood pressure measurements obtained via ultrasonic Doppler flow monitor (DOP) and 2 oscillometric noninvasive blood pressure monitors (CAR and PAS) to invasive blood pressure (IBP) in hospitalized, conscious dogs with a range of blood pressures. Design – Prospective clinical study. Setting – University teaching hospital. Animals – Eleven client‐owned dogs aged between 4 months and 11.5 years (median 6 y), and weighing between 5.8 and 37.5 kg (median 30.2 kg). Interventions – Blood pressure measurement. Measurements and Main Results – Three consecutive measurements of systolic, diastolic, and mean arterial pressure (MAP) were recorded for each of the 3 indirect devices (only systolic for DOP), along with concurrent IBP measurements. The data were categorized into 3 groups: hypotensive (direct MAP<80 mm Hg), normotensive (80 mm Hg≤direct MAP≥100 mm Hg), and hypertensive (direct MAP>100 mm Hg). Each indirect method was compared with the corresponding direct arterial pressure using the Bland‐Altman method. Within the hypotensive group, each indirect method overestimated the corresponding IBP. Within the normotensive group all indirect systolic measurements and the PAS diastolic measurements underestimated the corresponding IBP. The remaining indirect measurements overestimated the corresponding IBP. Within the hypertensive group, DOP and CAR systolic measurements underestimated the corresponding IBP, and the remaining indirect measurements overestimated the corresponding IBP. In hypertensive dogs oscillometric systolic measurements were more accurate than MAP. In hypotensive dogs MAP measurements were more accurate than systolic measurements. All indirect measurements were most accurate in hypertensive dogs. Conclusions – The noninvasive blood pressure monitors in our study did not meet the validation standards set in human medicine. However, CAR diastolic and MAP measurements within the normotensive group, CAR MAP measurements within the hypertensive group, and PAS diastolic measurements in all groups were close to these standards. All indirect measurements showed greater bias during hypotension. Precision was poorer for all indirect systolic measurements than for MAP.     

Adaptation of human oscillometric blood pressure monitors for use in dogs

Two digital oscillometric human blood pressure measuring devices were modified and evaluated as blood pressure monitors in 12 healthy anesthetized dogs. Direct arterial pressures were measured via cannulation of the dorsal pedal artery and were correlated with indirect measurements through an inflatable cuff placed over the dorsal pedal artery below the hock joint of the contralateral limb. Direct and indirect measurements were compared for systolic, diastolic, and calculated mean arterial pressures. Blood pressure ranges between 215/145 mm of Hg and 65/30 mm of Hg were obtained, using combinations of halothane, phenylephrine, calcium, and IV administered fluids. Machine A was found to be insufficient for clinical application, on the basis of correlation coefficients between direct and indirect pressures of 0.78, 0.65, and 0.74 for systolic, diastolic, and mean arterial pressures, respectively. Higher correlation coefficients between direct and indirect pressures (0.77, 0.87, and 0.87, respectively) were obtained with machine B. The results of the study reported here suggest machine B may be an effective blood pressure monitoring device in anesthetized dogs.     

Comparison of direct and indirect blood pressure measurements in anesthetized dogs.

The precision and accuracy of an indirect oscillometric blood pressure measurement technique (Dinamap 8100) was assessed in 11 anesthetized Beagle dogs weighing 8 to 11.5 kg. Direct blood pressure measurements were made by catheterization of the lingual artery, and simultaneous indirect measurements were determined by placing a cuff over the median artery (midradial area). Blood pressure measurements at 2 different planes of anesthesia (light and deep) were recorded in triplicate. At a light plane of anesthesia, the Dinamap 8100 underestimated diastolic and mean arterial pressure, and at a deep anesthetic plane overestimated systolic pressure. The indirect technique had good repeatability of systolic pressures. Regression analysis for the 2 techniques showed excellent correlation (r = 0.93). The results indicate that the indirect oscillometric blood pressure measurement technique provides a good estimate of systolic, diastolic, and mean arterial pressure in dogs weighing 8-11.5 kg.     

INDIRECT BLOOD PRESSURE MEASUREMENT IN ANAESTHETISED ANIMALS

The technique of indirect blood pressure measurement described by Wilson and Clark (1964) has been found to be applicable to anaesthetised animals and the technique has been easily modified for use in sheep, cattle and horses. Experimental work in dogs has shown that the width of the cuff has an important bearing on the accuracy of the indirect readings obtained. It would appear at present that for dogs at least two cuff widths should be used. A cuff 2.5 cm wide should be used for dogs under 12 kg and one 3.75 cm wide for heavier dogs. The length of the cuff appears to be unimportant providing the inflatable portion encircles the limb and the cuff is not applied too loosely or too tightly. A cuff length of 25 cm should be suitable for most animals. The occluding cuff used by Wilson and Clark (1964) measured 25 times 3.2 cm and these authors found good correlation with directly measured systolic pressure in a 12 kg dog. The technique can be readily applied to horses and sheep but careful placement of the occluding cuff in cattle is required to provide adequate transmission of the cuff pressure to the coccygeal vessels. Cuff widths of 3.75 cm are recommended for use on the tail in horses and cattle and a cuff 2.5cm wide on the hind limb for sheep. In dogs good correlation has been found between indirect and direct systolic pressure even with cuffs of different widths. This is adequate for routine anaesthetic work where changes in pressure are of more importance than absolute values. For comparative work between different animals it would be important to use cuffs of the correct width for the different sizes of animal.     

Determination of reference arterial blood pressure values by indirect methods for Kangal dogs

OBJECTIVES: To obtain reference arterial blood pressure values from Kangal dogs, a local giant breed found in Turkey. METHODS: Arterial blood pressure measurements were obtained from 48 healthy Kangal dogs using oscillometric and Doppler techniques. The ages of the dogs ranged from two to 96 months, with a mean (sd) age of 36 (16) months. RESULTS: The effect of age on systolic, diastolic and mean arterial pressures determined by the oscillometric technique and on systolic pressure determined by the Doppler technique was significant (P<0.001). Blood pressure was found to be higher in mature dogs compared with that in immature dogs. The effect of sex and the interaction between age and sex were not significant (P>0.05). There was a direct relationship between age and oscillometric systolic, diastolic and mean arterial pressures and Doppler systolic arterial blood pressure both in the whole group and the immature group (P<0.05). Correlation between age and systolic arterial blood pressure measured either by oscillometric or Doppler techniques was not significant in the mature group. CLINICAL SIGNIFICANCE: The Kangal dog is bred in various countries including Turkey. It is known that giant breed dogs, such as the Kangal dog, are predisposed to cardiovascular disease. Canine arterial blood pressure values are highly breed and age dependent, so a reference value for any other breed is inappropriate for Kangal dogs. Therefore, it is important to measure arterial blood pressure of Kangal dogs.     

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 the arterial blood pressure of dogs by two noninvasive methods.

The determination of the arterial blood pressure was done on 12 healthy mixed breed dogs in both the anesthetized and the conscious state, to evaluate two instruments (Doppler flow detector and infrasonde D4000), in their ability to indirectly determine arterial blood pressure. The coefficients of variation were higher with indirect methods when compared with the results obtained by cannulation. These coefficients were lower with the Doppler flow detector. The correlation study showed that both apparatuses were reliable in most situations. The infrasonde D4000 was more accurate than the Doppler in the conscious animals. However the results showed a lack of precision in hypertensive conscious dogs. The diastolic arterial blood pressure was particularly precise in the case of the anesthetized hypotensive dogs. Its sensitivity allowed it to register muscle movement artifacts. The Doppler flow detector showed less variation and was particularly accurate in both anesthetized and conscious hypertensive dogs. Its sensitivity allowed artifact movement sounds to be detected. The Doppler should be used in quiet surroundings or earphones should be worn by the evaluator. Some form of restraint is needed with the use of both instruments. Even if the correlations with the direct arterial blood pressure values were better with the infrasonde D4000, greater variations were found in the individual readings. The Doppler instrument represents in the hands of the investigators a better instrument for routine monitoring of blood pressure in the dog.     

Effect of long-term adaptation on indirect measurements of systolic blood pressure in conscious untrained beagles

To evaluate the effect of an adaptation period on systemic blood pressure readings, systolic blood pressure was measured in 12 young adult untrained beagles over several weeks by means of a Doppler flow detector and oscillometric devices. The pressure decreased gradually and significantly, and levelled out after 14 days. The median (range) of values obtained by Doppler were 166 (149 to 200) mmHg initially, 145 (119 to 176) mmHg on day 9, 138 (118 to 165) mmHg on day 10, 127 (111 to 139) mmHg on day 35, 124 (115 to 143) mmHg on day 94 and 127 (114 to 142) mmHg on day 161. All the later measurements were significantly lower than the initial measurement. Male dogs had higher blood pressures than females on each occasion. The blood pressure readings obtained with one of the oscillometric devices and the Doppler device were comparable and correlated significantly.     

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.     

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.     

Accuracy of indirect measurement of blood pressure in neonatal foals

The objectives of this study were to assess, in anesthetized neonatal foals, the accuracy of 2 automated indirect oscillometric monitors for measurement of mean arterial pressure (MAP), to determine the optimal site of cuff placement for MAP monitoring, and to determine the relationship between arterial blood pressure and cardiac output. Ten neonatal foals were anesthetized and instrumented with a catheter in the metatarsal artery for direct MAP monitoring and measurement of cardiac output by lithium dilution. Concurrent MAP measurements were obtained with Cardell and Dinamap oscillometric monitors with cuffs placed at 3 different sites (coccygeal, metatarsal, and median arteries). Blood pressure was manipulated by varying the depth of anesthesia and by administration of dobutamine or phenylephrine. A statistically significant (P = .025) interaction was found between the type of monitor and cuff placement site. With the Cardell monitor, placement of the cuff over the coccygeal artery resulted in a significantly lower bias than placement over the median or dorsal metatarsal artery (P < .0001 and P = .0149, respectively). No significant difference in bias was found with cuff placement site when using the Dinamap monitor. The correlation coefficient (r) between MAP and cardiac output was 0.47. Indirect oscillometry with a cuff placed over the coccygeal artery or dorsal metatarsal artery is an acceptable method for measuring MAP in foals. Blood pressure does not correlate well with cardiac output in anesthetized foals.     

A comparison of direct and indirect (oscillometric) measurements of arterial blood pressure in anaesthetised dogs, using tail and limb cuffs

Oscillometric measurements of arterial blood pressure were compared with direct measurements in anaesthetised dogs being monitored during routine surgery. Readings were obtained with tail cuffs and limb cuffs and the reproducibility (precision) of the readings from various cuff sites was also compared in conscious dogs. Tail cuffs gave the best precision in conscious dogs and the closest correlation with direct measurements in anaesthetised dogs, especially for systolic pressure. The proximal hindlimb site gave results with a slightly lower precision.