Review of non–invasive blood pressure measurement in animals: Part 2 — Evaluation of the performance of non-invasive devices

Abstract

Arterial blood pressure is a common parameter evaluated in conscious and anesthetized veterinary patients for a variety of reasons. Non-invasive blood pressure measurement techniques, such as Doppler ultrasound and oscillometry, are attractive in certain veterinary patients due to their availability and ease of use. The greatest limitation to non-invasive blood pressure monitoring can be its inaccuracy, particularly in hypotensive or hypertensive patients and in certain species. Part 1 of this 2-part review summarized the current techniques available to non-invasively measure arterial blood pressure in veterinary species and discussed validation of non-invasive devices. Part 2 summarizes the veterinary literature that evaluates the use of non-invasive blood pressure measurement techniques in conscious and anesthetized species and develops general conclusions for proper use and interpretation of non-invasive blood pressure devices.

Introduction

In the first part of this 2-part review, the physiology of arterial blood pressure (BP), techniques for its evaluation in veterinary species, and validation of non-invasive monitors were discussed. The second part of this review considers the veterinary literature that evaluates the use of non-invasive blood pressure (NIBP) measurement techniques in conscious and anesthetized animals. The findings are compared to the validation criteria of the American College of Veterinary Internal Medicine (ACVIM) Hypertension Consensus Panel and the Veterinary Blood Pressure Society Recommendations in an attempt to develop general conclusions for proper use and interpretation of NIBP devices. Evaluation of arterial BP plays an important role in veterinary care and disease management. Non-invasive blood pressure can be evaluated using a number of techniques including auscultatory, Doppler ultrasonic flow detector, oscillometry, high definition oscillometry, and plethysmography methods. Doppler and oscillometry techniques are used most often (1,2).

The gold standard for arterial BP measurement in animals is via direct arterial catheter placement; however, this technique is not without risk, requires specific technical skill and equipment, is invasive, and is not always justified for most noncritical cases. Therefore, NIBP measurement techniques are attractive alternatives due to their ease of use, availability, and non-invasiveness. In order for an NIBP measurement device to be considered a “validated device,” it must meet specific criteria to demonstrate that it is an acceptable alternative to the gold standard measurement technique. In veterinary medicine, validation standards have not been established, except for recommendations from the ACVIM Hypertension Consensus Panel and Veterinary Blood Pressure Society Recommendations (AHCP-VBPS Validation) (3). These validation standards were discussed in detail in the first part of this review (4).

Doppler ultrasonic flow detector

Doppler in canine species

In conscious, normotensive dogs, Doppler consistently underestimates direct systolic arterial BP taken from the femoral (5,6) or dorsal pedal artery (7,8). In anesthetized dogs, Doppler has been evaluated against direct systolic arterial BP measured from the dorsal pedal, femoral, radial, or coccygeal artery with conflicting results. In some studies, Doppler tended to underestimate direct systolic arterial BP (8,9), while overestimation was reported in others (10,11). Doppler has also been unreliable in detecting hypotension in anesthetized dogs, correctly identifying hypotension (defined as direct mean arterial BP < 60 mmHg or Doppler pressures of < 90 mmHg) only 66.7% to 69.2% of the time (11). Despite an acceptable mean bias of 2.8 mmHg, the 95% limits of agreement were −46.4 to 51.9 mmHg, demonstrating poor precision (11) (Table 1).

Table 1.

Published studies evaluating Doppler ultrasound and oscillometric non-invasive blood pressure measurement in dogs in comparison with the American College of Veterinary Internal Medicine (ACVIM) criteria for technique validation.

Parameter	Number of animals	Bias (mmHg)	Standard deviation (mmHg)	Correlation	< 10 mmHg (% of measurements)	< 20 mmHg (% of measurements)
ACVIM criteria	8	≤ 10	≤ 15	≥ 0.9	≥ 50	≥ 80
Doppler Ultrasound
Conscious dogs (5)
Direct BP source: Femoral artery
NIBP cuff location: Median artery
SAP	28	NR	NR	NR	48	70
Conscious dogs (6)
Direct BP source: Femoral artery
NIBP cuff location: Metatarsal artery
SAP	12	11.6	19.7	0.827	43	NR
Conscious dogs (7)
Direct BP source: Metatarsal artery
NIBP cuff location: Metatarsal artery
MAP < 80 mmHg		−16.6	18.9	0.63
MAP 80–100 mmHg	11	16.1	41.2	−0.16	NR	NR
MAP > 100 mmHg		8.2	37.9	−0.12
Anesthetized dogs (9)
Direct BP source: Dorsal pedal artery
NIBP cuff location: Cranial tibial artery
SAP < 90 mmHg		0.2			73	100
SAP 90–140 mmHg	9	−6	NR	0.05	63.6	86.4
SAP > 140 mmHg		−18			23.7	45.8
Anesthetized dogs (9)
Direct BP source: Dorsal pedal artery
NIBP cuff location: Metatarsal artery
SAP < 90 mmHg		−6			60	94.3
SAP 90–140 mmHg	9	−13	NR	0.08	42.6	72.3
SAP > 140 mmHg		−25			21.7	48.3
Anesthetized dogs (9)
Direct BP source: Dorsal pedal artery
NIBP cuff location: Median artery
SAP < 90 mmHg		10			41.9	100
SAP 90–140 mmHg	9	−3	NR	0.39	66.7	88.1
SAP > 140 mmHg		−26			17.6	39.2
Anesthetized dogs (8)
Direct BP source: Dorsal pedal artery
NIBP cuff location: Median artery
SAP	10	−4.1	24.7	NR	60	70
Conscious dogs (8)
Direct BP source: Dorsal pedal artery
NIBP cuff location: Median artery
SAP	10	−15.1	21.6	NR	20	40
Anesthetized dogs (12)
Direct BP source: Dorsal pedal artery
NIBP cuff location: Median or cranial tibial artery
SAP < 90 mmHg	10	−5.7	12.3	NR	61	90
SAP 90–160 mmHg		−17.3	14.9		23	60
Anesthetized dogs (13)
Direct BP source: Dorsal pedal artery
NIBP cuff location: Metatarsal artery
MAP < 60 mmHg	41	10	27.9	0.8	47.8	51.1
MAP 60–120 mmHg		8.2	20.9	0.9	31.6	65.8
Anesthetized dogs (11)
Direct BP source: 76.7% dorsal pedal artery, 17.8% coccygeal artery, 2.7% femoral artery, 2.7% radial artery
NIBP cuff location: Median or cranial tibial artery
MAP < 60 mmHg	85	2.8	NR	NR	NR	NR
Oscillometry
Conscious dogs (5)
Direct BP source: Femoral artery
NIBP cuff location: Median artery
Oscillometric technology: NR
SAP					37	59
MAP	28	NR	NR	NR	59	89
DAP					41	70
Anesthetized dogs (25)
Direct BP source: Cranial tibial artery
NIBP cuff location: Metacarpal artery
Oscillometric technology: Cardell Veterinary BP Monitor 9301V, CAS Medical
SAP 50–80 mmHg
SAP		−6	4
MAP		6	5
DAP		11	8
SAP 90–120 mmHg
SAP		15	7
MAP	6	10	8	NR	NR	NR
DAP		10	8
SAP 120–150 mmHg
SAP		23	7
MAP		13	10
DAP		12	14
Anesthetized dogs (25)
Direct BP source: Cranial tibial artery
NIBP cuff location: Metatarsal artery
Oscillometric technology: Cardell Veterinary BP Monitor 9301V, CAS Medical
SAP 50–80 mmHg
SAP		−4	3
MAP		6	3
DAP		12	6
SAP 90–120 mmHg
SAP		16	5
MAP	6	15	4	NR	NR	NR
DAP		13	5
SAP 120–150 mmHg
SAP		20	0
MAP		16	0
DAP		19	0
Anesthetized dogs (25)
Direct BP source: Cranial tibial artery
NIBP cuff location: Cranial tibial artery
Oscillometric technology: Cardell Veterinary BP Monitor 9301V, CAS Medical
SAP 50–80 mmHg
SAP		−3	3
MAP		9	3
DAP		13	6
SAP 90–120 mmHg
SAP		21	5
MAP	6	16	4	NR	NR	NR
DAP		15	4
SAP 120–150 mmHg
SAP		25	5
MAP		23	5
DAP		24	4
Anesthetized dogs (28)
Direct BP source: Lingual artery
NIBP cuff location: Median artery
Oscillometric technology: Cardell Veterinary Monitor 9402, CAS Medical
SAP		0.88	1.92
MAP	8	9.95	1.28	NR	NR	NR
DAP		20.11	1.83
Anesthetized dogs (28)
Direct BP source: Lingual artery
NIBP cuff location: Cranial tibial artery
Oscillometric technology: Cardell Veterinary Monitor 9402, CAS Medical
SAP		2.79	1.93
MAP	8	12.25	1.28	NR	NR	NR
DAP		23.95	1.83
Anesthetized dogs (28)
Direct BP source: Dorsal pedal artery
NIBP cuff location: Median artery
Oscillometric technology: Cardell Veterinary Monitor 9402, CAS Medical
SAP		7.75	2.00
MAP	8	6.36	1.59	NR	NR	NR
DAP		13.67	2.17
Anesthetized dogs (28)
Direct BP source: Dorsal pedal artery
NIBP cuff location: Cranial tibial artery
Oscillometric technology: Cardell Veterinary Monitor 9402, CAS Medical
SAP		5.4	2.00
MAP	8	8.81	1.59	NR	NR	NR
DAP		17.27	2.17
Anesthetized dogs (31)
Direct BP source: Femoral or dorsal pedal artery
NIBP cuff location: Dorsal pedal artery (metacarpal artery in two dogs)
Oscillometric technology: Surgivet V60046
SAP < 90 mmHg
SAP		1.9	11.06	0.65
MAP		3.4	7.68	0.65
DAP		8.2	8.85	0.50
SAP 91–120 mmHg
SAP		8.6	11.89	0.39	36	68
MAP	34	2.1	0.79	0.74	68	89
DAP		5.2	12.10	0.66	53	80
SAP > 121 mmHg
SAP		22.7	17.90	0.49
MAP		5.5	9.58	0.79
DAP		9.4	10.78	0.76
Conscious dogs (7)
Direct BP source: Metatarsal artery
NIBP cuff location: Metatarsal artery
Oscillometric technology: Datascope Passport
MAP < 80 mmHg
SAP		−15.3	20.4	0.50
MAP		−12.1	6.9	0.75
DAP		−6.4	3.5	0.84
MAP 80–100 mmHg
SAP		14.6	6.9	0.17
MAP	11	−5.2	9.2	0.30	NR	NR
DAP		1.6	7.8	0.21
MAP > 100 mmHg
SAP		−3.9	41.5	−0.34
MAP		−17.2	10.5	0.81
DAP		−3.5	14.6	−0.28
Conscious dogs (7)
Direct BP source: Metatarsal artery
NIBP cuff location: Metatarsal artery
Oscillometric technology: Cardell Veterinary Monitor 9401, Sharn Veterinary
MAP < 80 mmHg
SAP		−22.5	5.2	0.97
MAP		−12.6	3.3	0.96
DAP		−15.0	5.7	0.86
MAP 80–100 mmHg
SAP		15.9	27.6	0.47
MAP	11	−1.3	8.5	0.60	NR	NR
DAP		−4.6	9.1	0.57
MAP > 100 mmHg
SAP		3.0	29.4	0.22
MAP		−5.8	11.7	0.73
DAP		−12.1	13.4	0.40
Anesthetized dogs (29)
Direct BP source: Dorsal pedal artery
NIBP cuff location: Median artery
Oscillometric technology: PetMap, Ramsey Medical
Normotension
SAP		−14.7	15.5
MAP		−14.1	15.8
DAP		−16.3	12
MAP ≤ 40 mmHg	8			NR	NR	NR
SAP		−32.2	22.6
MAP		−16.8	17.2
DAP		−24.2	19.8
Anesthetized dogs (9)
Direct BP source: Dorsal pedal artery
NIBP cuff location: Median artery
Oscillometric technology: PC Scout Monitor
SAP < 90 mmHg
SAP		6			66.7	100
MAP		NR			85.4	100
DAP		NR			96.5	100
SAP 90–140 mmHg
SAP		−15			31.8	63.6
MAP	9	NR	NR	NR	86.4	100
DAP		NR			81.0	95.2
SAP > 140 mmHg
SAP		−42			4.0	16
MAP		NR			63.6	90.9
DAP		NR			66.7	95.8
Anesthetized dogs (30)
Direct BP source: Dorsal pedal artery
NIBP cuff location: Median artery
Oscillometric technology: PetMap graphic, Ramsey Medical
SAP		9.9
MAP	21	−6.3	NR	NR	NR	NR
DAP		−8.9
Anesthetized dogs (31)
Direct BP source: Metatarsal artery
NIBP cuff location: Metatarsal artery
Oscillometric technology: Surgivet V9203
MAP < 60 mmHg
SAP		7.89	10.2
MAP		1.30	5.89
DAP		8.33	7.53
MAP 60–80 mmHg
SAP		15.4	15.4
MAP	29	6.67	6.67	NR	NR	NR
DAP		7.63	7.63
MAP > 80 mmHg
SAP		55.11	26.77
MAP		5.71	8.73
DAP		5.82	9.90
Anesthetized dogs (8)
Direct BP source: Dorsal pedal artery
NIBP cuff location: Median artery
Oscillometric technology: PetMap, Ramsey Medical
SAP		−6.1	−6.1		60	90
MAP	10	−2.9	−2.9	NR	NR	NR
DAP		−6.9	−6.9		60	100
Conscious dogs (8)
Direct BP source: Dorsal pedal artery
NIBP cuff location: Median artery
Oscillometric technology: PetMap, Ramsey Medical
SAP		−5.8	16.5		50	70
MAP	10	3.8	8.9	NR	NR	NR
DAP		4.6	7.9		70	100
Anesthetized dogs (34)
Direct BP source: Median caudal artery
NIBP cuff location: Median artery
Oscillometric technology: CAS (SunTech) Medical System
SAP		0.2	6.2	0.9	100	100
MAP	20	−2.5	5.0	1.0	100	100
DAP		−2.6	6.0	0.9	100	100
Anesthetized dogs (34)
Direct BP source: Median caudal artery
NIBP cuff location: Median artery
Oscillometric technology: SunTech Medical
SAP		3.4	6.3	0.9	100	100
MAP	20	1.6	3.8	1.0	100	100
DAP		2.2	4.5	1.0	100	100
Anesthetized dogs (33)
Direct BP source: Median sacral artery
NIBP cuff location: Median artery
Oscillometric technology: SunTech Medical
SAP		3.96	6.31	0.95	100	100
MAP	17	2.12	5.14	0.98	100	100
DAP		2.65	4.54	0.97	100	100

NR — not reported. Highlighted values meet validation criteria.

Recently, 2 studies evaluated the level of agreement between Doppler and direct arterial BP in dogs weighing < 5 kg (12,13). In 1 study, conditions of an acceptable direct systolic arterial BP (90 to < 160 mmHg) and low systolic arterial BP (< 90 mmHg) were used for comparisons between Doppler and direct BP measurements (12). In the other study, acceptable direct arterial BP was defined as a mean arterial BP of 60 to 120 mmHg, and low arterial BP as < 60 mmHg (13). It has been hypothesized that when measuring arterial BP using Doppler in dogs of this body weight, the measured value may be more reflective of mean arterial BP rather than systolic arterial BP, which has been previously identified in cats, in which Doppler values tend to underestimate direct systolic arterial BP (14–17). In both canine studies (12,13), Doppler overestimated both direct systolic and mean arterial BP measured from the dorsal pedal artery. The smallest bias was found when Doppler was used as an estimate of direct systolic arterial BP rather than mean arterial BP, during conditions of acceptable and low arterial blood pressures (12,13) (Table 1). In the second study, both values for bias in normotensive and hypotensive conditions were acceptable, but the standard deviation (SD) was exceeded for both situations and the number of measurements within 10 to 20 mmHg of the reference method was always below the desired percentages (13) (Table 1). In both studies, there were large differences between Doppler systolic arterial BP and direct mean arterial BP and Doppler did not meet any of the AHCP-VBPS validation criteria (12,13). The conclusion from these studies is that Doppler BP measurements provide values that are not accurate as an estimate of direct mean arterial BP values in dogs weighing < 5 kg. In at least 1 of these studies the Doppler values were reliable for estimation of direct systolic arterial BP, but only when mean arterial blood pressures were < 60 mmHg (12) (Table 1).

Doppler in feline species

Initial evaluation of NIBP measurement techniques in cats began at similar times as studies in dogs, but there are fewer published studies. An early evaluation of Doppler in anesthetized cats identified that the measurement underestimates direct systolic arterial BP and better predicts direct mean arterial BP, obtained from the femoral artery (15). As a result, the authors proposed a calibration factor such that:

$$\text{femoral\hspace{0.17em}systolic\hspace{0.17em}arterial\hspace{0.17em}BP}=\text{Doppler\hspace{0.17em}systolic\hspace{0.17em}BP}+14\hspace{0.17em}\text{mmHg}$$(15)

In another study, similar findings were obtained: Doppler underestimated direct systolic arterial BP measured from the femoral artery but was a good predictor of direct mean arterial BP with a bias ± precision of −0.8 ± 6 mmHg (14) (Table 2). This interpretation of Doppler measurement reflecting mean arterial BP rather than systolic arterial BP seems to be unique to cats and continues to be published in the veterinary literature. Studies in cats have invariably demonstrated that Doppler measurements as an estimation of systolic arterial BP values do not comply with the AHCP-VBPS. In anesthetized cats, Doppler measurements in comparison to direct systolic and mean arterial blood pressures measured from the femoral and dorsal pedal arteries were found to be a poor predictor of both direct systolic and mean arterial BP (18) (Table 2).

Table 2.

Published studies evaluating Doppler ultrasound and oscillometric non-invasive blood pressure measurement in cats in comparison with the American College of Veterinary Internal Medicine (ACVIM) criteria for technique validation.

Parameter	Number of animals	Bias (mmHg)	Standard deviation (mmHg)	Correlation	< 10 mmHg (% of measurements)	< 20 mmHg (% of measurements)
ACVIM criteria	8	≤ 10	≤ 15	≥ 0.9	≥ 50	≥ 80
Doppler Ultrasound
Anesthetized cats (19)
Direct BP source: Femoral artery
NIBP cuff location: Dorsal pedal artery
SAP	11	9.4	14.86	0.96	46	31
MAP		8.6	15.25	0.95	39	37
Anesthetized cats (19)
Direct BP source: Femoral artery
NIBP cuff location: Coccygeal artery
SAP	11	−4.7	22.87	0.91	45	27
MAP		−1.8	19.68	0.91	42	32
Anesthetized cats (14)
Direct BP source: Femoral artery
NIBP cuff location: Median artery
SAP	8	−25	7.4	0.88	NR	NR
MAP		−0.8	6	0.89
Anesthetized cats (18)
Direct BP source: Dorsal pedal artery (19 cats), femoral artery (20 cats)
NIBP cuff location: Median artery
SAP		−8.8		0.65
MAP	39	14	NR	0.66	NR	NR
DAP		27.9		0.68
Oscillometry
Anesthetized cats (16)
Direct BP source: Femoral artery
NIBP cuff location: Median artery
Oscillometric technology: Cardell Veterinary BP Monitor 9301V, CAS Medical
MAP < 60 mmHg
SAP		−5.2	4.2
MAP		0.7	4.3
DAP		−3.9	5.9
MAP 60–140 mmHg
SAP		−12.1	6.5
MAP	6	0.1	3	NR	NR	NR
DAP		−0.3	5.6
MAP > 140 mmHg
SAP		−17.7	7.8
MAP		−3.3	4.2
DAP		3.7	6.2
Anesthetized cats (35)
Direct BP source: Dorsal pedal artery
NIBP cuff location: Median artery
Oscillometric technology: PetMap, Ramsey Medical
SAP		−14.9
MAP	21	−1.3	NR	NR	NR	NR
DAP		4.4
Anesthetized cats (35)
Direct BP source: Dorsal pedal artery
NIBP cuff location: Median artery
Oscillometric technology: Cardell Max-1 Veterinary Monitor
SAP		−13.4
MAP	21	−3.6	NR	NR	NR	NR
DAP		8.0
Anesthetized cats (36)
Direct BP source: Femoral artery
NIBP cuff location: Coccygeal artery
Oscillometric technology: Cardell Veterinary Monitor 9403, Midmark
SAP		−10.1	16.7	0.896
MAP	6	10.0	13.3	0.917	NR	NR
DAP		20.2	12.7	0.898
Anesthetized cats (37)
Direct BP source: Dorsal pedal artery
NIBP cuff location: Median artery
Oscillometric technology: PetMap Classic, Ramsey Medical
SAP		4.2	28.5
MAP	8	−1.9	14.6	NR	NR	NR
DAP		−6.1	13.2
Anesthetized cats (37)
Direct BP source: Dorsal pedal artery
NIBP cuff location: Coccygeal artery
Oscillometric technology: PetMap Classic, Ramsey Medical
SAP		7.2	31.3
MAP	8	−1.1	11.7	NR	NR	NR
DAP		−6.1	11.6
Anesthetized cats (37)
Direct BP source: Dorsal pedal artery
NIBP cuff location: Median artery
Oscillometric technology: PetMap Graphic, Ramsey Medical
SAP		7.7	27.0
MAP	8	0.2	13.0	NR	NR	NR
DAP		−4.3	11.5
Anesthetized cats (37)
Direct BP source: Dorsal pedal artery
NIBP cuff location: Coccygeal artery
Oscillometric technology: PetMap Graphic, Ramsey Medical
SAP		10.9	29.6
MAP	8	−0.1	12.1	NR	NR	NR
DAP		−4.4	11.7

NR — Not reported. Highlighted values meet validation criteria.

All of the previous studies in cats that have evaluated Doppler for arterial BP measurement in comparison to direct arterial BP readings have placed the BP cuff on the antebrachium over the median artery and have utilized a cuff width which is 35% to 45% of the circumference of the antebrachium (14–19) (Table 2). A discrepancy in systolic arterial BP values has been identified depending on cuff placement when utilizing Doppler in conscious cats such that cuff placement over the coccygeal artery resulted in consistently higher systolic arterial BP values in comparison to values obtained when the cuff was placed on the antebrachium over the radial artery (20). However, this study made no comparison to direct arterial BP values and therefore conclusions on which location was more accurate cannot be made. It has been shown that Doppler measurements had the highest overall accuracy and lowest failure rate in anesthetized cats (17), probably because it is easier to measure arterial BP with this technique in the anesthetized versus the conscious animal and therefore there is less source of error.

Doppler in equine species

In the last 30 y only a single study was published that evaluated the use of Doppler for NIBP measurement in horses (21). This study compared systolic arterial BP measured invasively via the facial artery to those measured by Doppler using the coccygeal artery in dorsally recumbent, anesthetized horses. The authors concluded that Doppler could not be recommended as the sole technique for BP monitoring in anesthetized horses due to the inaccuracy of the technique, reporting an error range of ± 20 mmHg in 5% of horses (21).

Doppler in exotic species

Extensive investigation of NIBP measurement techniques in exotic species is similarly limited. One validation study in anesthetized Hispaniolan Amazon parrots (Amazona ventralis) evaluated Doppler and oscillometry with the NIBP cuffs placed over the superficial ulnar artery of the wing and the ischiatic artery of the leg in comparison to direct arterial BP readings from the superficial ulnar artery or the ischiatic artery of the contralateral limbs (22). This study found that the readings obtained via Doppler disagreed considerably from direct systolic arterial BP readings (Table 3), leading the authors to conclude that this technique could not be recommended for use in this species (22), and the technique did not meet the passing criteria of AHCP-VBPS validation (3). Another study evaluated the same 2 NIBP measurement techniques in conscious and anesthetized red-tailed hawks (Buteo jamaicensis) against direct mean arterial BP over a range of arterial BP values, using 3 cuff sizes: 20% to 30% of circumference, 30% to 40% of circumference, and 40% to 50% of circumference of the superficial ulnar artery or median metatarsal artery. This study demonstrated good agreement for Doppler, according to the combined bias of 2 ± 13 mmHg when a cuff width:limb circumference ratio of 40% to 50% was used (23), complying with the passing criteria of AHCP-VBPS validation (3) (Table 3).

Table 3.

Published studies evaluating Doppler ultrasound non-invasive blood pressure measurement technique in exotic species in comparison with the American College of Veterinary Internal Medicine (ACVIM) criteria for technique validation.

Parameter	Number of animals	Bias (mmHg)	Standard deviation (mmHg)	Correlation	< 10 mmHg (% of measurements)	< 20 mmHg (% of measurements)
ACVIM criteria	8	≤ 10	≤ 15	≥ 0.9	≥ 50	≥ 80
Doppler Ultrasound
Anesthetized Hispaniolan Amazon parrots (22)
Direct BP source: Superficial ulnar artery
NIBP cuff location: Superficial ulnar artery (wing)
SAP	16	24	NR	NR	NR	NR
Anesthetized Hispaniolan Amazon parrots (22)
Direct BP source: Superficial ulnar artery
NIBP cuff location: Ischiatic artery (leg)
SAP	16	14	NR	NR	NR	NR
Conscious red-tailed hawks (23)
Direct BP source: Superficial ulnar artery
NIBP cuff location: Superficial ulnar artery (cuff width 40–50% of circumference)
SAP	6	59	33	NR	NR	NR
MAP		20	33
Anesthetized rabbits (24)
Direct BP source: Auricular artery
NIBP cuff location: Median artery
SAP	17	1	8	0.82	85	NR
MAP		−13	8	0.79	NR

NR — Not reported. Highlighted values meet validation criteria.

In anesthetized rabbits, Doppler measured from the dorsal carpal branch of the radial artery using an average cuff width:limb circumference ratio of 50% was in good agreement with direct systolic arterial BP readings from the auricular artery, and was found to be a reliable technique in positively predicting systolic arterial BP values below 80 mmHg 91% of the time (24). The bias of 1 ± 8 mmHg and 95% limits of agreement from −14 to 17 mmHg of Doppler with respect to direct arterial BP measurements in this study (24) is within the recommended minimum passing criteria of AHCP-VBPS validation (3) (Table 3).

Oscillometry

Oscillometry in canine species

Many studies in veterinary species have evaluated the performance of oscillometric BP monitors in comparison with direct arterial BP values. Conclusions across studies are difficult because not all technologies of oscillometric monitors are the same; the algorithms are likely to vary between manufacturers and have an impact on the performance of the monitor. The first oscillometric monitor for veterinary use was the Dinamap Veterinary Blood Pressure monitor, developed in 1993 by Critikon (Tampa, Florida, USA) (25). This monitor received a lot of attention in the earlier veterinary studies that evaluated oscillometric BP measurement in dogs (26,27). In studies in conscious dogs, acceptable readings were obtained with the Dinamap monitor when the oscillometric cuff was placed over the coccygeal artery at the base of the tail (6,27).

Critikon discontinued their monitor in 1999 and the following year Sharn Veterinary (Caledonia, Michigan, USA) developed the Cardell Veterinary Blood Pressure monitor (25). As this and newer oscillometric BP monitors have become available, studies evaluating their performance have emerged in the veterinary literature. The most extensively studied oscillometric monitors in canine patients have been the Cardell Veterinary Monitor, the SurgiVet Monitor by Smiths Medical (Minneapolis, Minnesota, USA) and the petMAP Blood Pressure Measurement Device by Ramsay Medical (Ramsay Medical, NSW, Australia).

In anesthetized dogs, the performance of the Cardell Veterinary Blood Pressure monitor has been evaluated over a range of systolic arterial BP values: > 200 mmHg, 120 to 150 mmHg, 90 to 120 mmHg, and 50 to 80 mmHg as well as cuff positions: metacarpal artery, median artery, metatarsal artery, and cranial tibial artery (25,28). Results between studies are sometimes conflicting and make conclusions and generalization difficult in terms of which of the arterial BP readings — systolic, diastolic or mean — is more reliable with this technology. This is due to different methodology used to evaluate the arterial BP ranges. In one study, when arterial BP was increased with administration of phenylephrine, the bias and precision for all pressures were better and there were slight variations among comparisons in the measurements between forelimb and hind limb versus direct measurement from the dorsal pedal artery or lingual artery (28). The measurements were usually below the established mean error of 10 ± 15 mmHg (mean ± SD) by the AHCP-VBPS validation (3). In the latter study (28), diastolic arterial BP tended to have less accurate bias and precision than systolic and mean arterial BP (Table 1). Conversely, in another study (25), arterial BP ranges were manipulated by anesthetic depth, and bias and precision for systolic and mean arterial BP were within the limits of the AHCP-VBPS validation, only when systolic arterial BP values were in the 50 to 80 mmHg range (Table 1).

In conscious dogs, placing the cuff above the tibiotarsal joint over the cranial tibial artery during conditions of low arterial BP (mean arterial BP < 80 mmHg), measured directly from the dorsal pedal artery, demonstrated that the Cardell monitor performed better than another oscillometric device (Datascope Passport; Datascope Corp, Paramus, New Jersey, USA) or Doppler, despite a tendency for overestimating most direct arterial BP values (systolic, diastolic and mean) (7). In conditions of higher arterial BP values (mean arterial BP > 80 mmHg), the Cardell monitor underestimated systolic and overestimated both diastolic and mean arterial BP values. Conditions of AHCP-VBPS validation were only met, or almost met, for mean arterial BP during low arterial BP and for diastolic and mean arterial BP during higher arterial BP values (7) (Table 1).

The petMAP is a portable, oscillometric BP measurement device that claims to provide species and cuff site optimization for enhanced accuracy of NIBP measurement. In a model of hypotension (MAP < 40 mmHg) created via significant blood loss in anesthetized dogs, considerable disagreement was identified between NIBP measurements taken from a cuff placed over the median artery and direct arterial BP readings taken from the dorsal pedal artery with this monitor (29). The monitor was found to greatly overestimate hypotension, and the performance of the monitor during normotension (defined as mean arterial BP 66 ± 9 mmHg) was no better, demonstrating consistently large biases and SD (29) (Table 1). These findings led the authors to conclude that the monitor was unreliable in identifying hypotension, and of clinical importance, it is likely to overestimate hypotension (29). The monitor has been evaluated in anesthetized dogs with NIBP measurements taken from a cuff placed over the median artery and compared to direct arterial BP readings from the dorsal pedal artery (8,30). These studies identified poor agreement (30) and poor precision (8) between the petMAP and directly measured arterial BP values, leading one group of authors to conclude that the device could not be recommended (30). Both studies reported very wide limits of agreement for systolic, mean, and diastolic arterial BP measurements (Table 1).

The SurgiVet monitor has a unique BP cuff, having the entire cuff inflate during measurement. This monitor has been evaluated in 2 studies in anesthetized dogs; 1 utilized clinical cases (31), while the other induced hypotension via blood loss (32). The performance of the monitor was evaluated over a range of arterial BP values: systolic arterial BP > 121 mmHg, between 91 and 120 mmHg, and < 90 mmHg (31); or mean arterial BP values > 80 mmHg, between 60 and 80 mmHg, and < 60 mmHg (32). Both studies compared oscillometric BP measured from a cuff placed on the metatarsal artery to direct arterial BP readings from the dorsal pedal artery. The results showed that the monitor tended to underestimate arterial BP across the range of BP values evaluated, but provided the best agreement with direct mean arterial BP (31,32) (Table 1). These results meet the AHCP-VBPS validation criteria; however, data for correlation and the percentage of BP measurements that fell within 10% and 20% of the direct arterial BP readings were not provided. Furthermore, the criteria for mean error and SD were only met when the heart rate of the study dogs was < 120 bpm (32). Of clinical importance, in both studies the monitor correctly predicted hypotension.

Devices in 2 studies in anesthetized, normotensive dogs have met all the AHCP-VBPS validation criteria of the ACVIM for NIBP measurement devices (33,34) (Table 1). The oscillometric technology used in both of these studies was from Suntech Medical (Morrisville, North Carolina, USA) and is available in the company’s own veterinary monitors or the multiparameter monitors manufactured by DRE Veterinary (Louisville, Kentucky, USA), the DRE Waveline Pro and the DRE Waveline Touch. In both studies, the dogs were anesthetized and the oscillometric cuff was placed on the antebrachium over the median artery and direct arterial BP readings were measured from the median caudal artery (34) or the median sacral artery (33) (Table 1).

Oscillometry in feline species

When oscillometric BP monitoring was first investigated in feline patients, the Dinamap Veterinary Blood Pressure monitor (Critikon) was used to evaluate the clinical utility. These studies found that this monitor did not accurately measure arterial BP in comparison to direct arterial BP readings taken from the femoral artery (14,19). This may be the reason for the initial conclusion that oscillometric devices were inaccurate in cats.

Studies evaluating the performance of the Cardell Veterinary Blood Pressure monitor in cats demonstrated similar results. The first study evaluated the monitor in 6 isoflurane-anesthetized cats over 3 BP ranges: mean arterial BP > 140 mmHg, 60 to 140 mmHg, and < 60 mmHg. It was found that the Cardell monitor provided a good estimate of mean and diastolic arterial BP but tended to underestimate systolic arterial BP, which became worse as BP increased: the oscillometric cuff was placed on the antebrachium over the median artery and compared to direct arterial BP readings from the femoral artery (16) (Table 2). The same study also identified no effect of clipping the hair on the limb prior to placement of the oscillometric BP cuff. Evaluation of the Cardell monitor with the cuff also placed on the antebrachium over the median artery and compared to direct arterial BP readings from the dorsal pedal artery also showed poor agreement, but the monitor came closest to correctly estimating mean arterial BP (35). The bias was smallest for mean arterial BP (Table 2); however, the limits of agreement were very wide (−31.6 to 24.5 mmHg), and similar findings for systolic and diastolic arterial BP values were identified (35). Placement of the cuff on the base of the tail and comparison to direct arterial BP readings from the femoral artery in 6 anesthetized cats met the AHCP-VBPS validation criteria for bias, limits of agreement, and correlation coefficient for mean arterial BP evaluation using the Cardell monitor (36) (Table 2).

The petMAP has been evaluated in anesthetized cats in 2 studies (35,37), both of which compared the NIBP measurements to direct arterial BP readings from the dorsal pedal artery. In both studies, the monitor performed poorest with estimation of systolic arterial BP, regardless of the cuff being placed on the antebrachium or the tail (35,37). The monitor did meet some of the AHCP-VBPS validation criteria (Table 2).

Oscillometry in equine species

Oscillometric BP monitoring techniques have only recently been evaluated in the veterinary literature in horses, with 6 papers being published in the last 3 y (38–43). Four oscillometric BP monitors have been evaluated in horses. In a clinical study of anesthetized horses, the Sentinel Blood Pressure monitor (Sentinel Healthcare, Seattle, Washington, USA) was found to result in a high degree of variability and was not recommended as an alternative to direct arterial BP monitoring in horses (38) (Table 4). The authors recommended that in laterally recumbent horses the oscillometric cuff should be placed on the tail and in dorsally recumbent horses the oscillometric cuff should be placed on the cannon bone as these cuff placements resulted in the lowest difference between NIBP readings compared to direct arterial BP values; however, the study did not report a Bland-Altman analysis (38). One study that evaluated 17 combinations of cuff size and measurement location via oscillometry using the Cardell Veterinary Blood Pressure monitor in anesthetized horses, reported that only when the cuff was placed on the tail and had a cuff width of 25% of the tail circumference did the monitor provide mean arterial BP measurements that were comparable to direct arterial BP readings taken from the transverse facial artery, reporting an acceptable bias of 0.39 mmHg and SD of 2.96 mmHg, which both meet the AHCP-VBPS validation criteria (41) (Table 4). The oscillometric technology within the Datex Ohmeda Multiparameter monitor (GE Healthcare, St. Louis, Missouri, USA) has been evaluated in standing (40) and anesthetized (43) horses, with placement of the oscillometric cuff over the coccygeal artery at the base of the tail (Table 4). The study in conscious, standing horses varied BP pharmacologically and utilized the facial or transverse facial artery to measure direct arterial BP. A correction factor of +0.736 mmHg/cm difference in height was applied (40). The authors identified that the monitor was not reliable during periods of second-degree atrioventricular block, a common arrhythmia in horses, but may be acceptable to measure mean arterial BP in standing horses (40). The authors did not recommend the use of the monitor in anesthetized horses after comparison to direct arterial BP values measured from the facial or metatarsal artery due to the wide limits of agreement (43) (Table 4). In both studies only bias and SD were reported; however, the Datex Ohmeda monitor met the AHCP-VBPS validation criteria for mean and diastolic arterial BP (40,43).

Table 4.

Published studies evaluating oscillometric non-invasive blood pressure measurement technique in foals and horses in comparison with the American College of Veterinary Internal Medicine (ACVIM) criteria for technique validation.

Parameter	Number of animals	Bias (mmHg)	Standard deviation (mmHg)	Correlation	< 10 mmHg (% of measurements)	< 20 mmHg (% of measurements)
ACVIM criteria	8	≤ 10	≤ 15	≥ 0.9	≥ 50	≥ 80
Oscillometry
Anesthetized foals (45)
Direct BP source: Metatarsal artery
NIBP cuff location: Coccygeal artery
Oscillometric technology: ProPaq Encore
SAP		8.0
MAP	6	−1.1	NR	NR	NR	NR
DAP		−1.3
Conscious foals (45)
Direct BP source: Metatarsal artery
NIBP cuff location: Coccygeal artery
Oscillometric technology: ProPaq Encore
SAP		15.0
MAP	4	−0.5	NR	NR	NR	NR
DAP		−0.4
Anesthetized foals (44)
Direct BP source: Metatarsal artery
NIBP cuff location: Coccygeal artery
Oscillometric technology: Cardell Veterinary Monitor 9402, CAS Medical
MAP	10	−0.5	8.8	NR	NR	NR
Anesthetized foals (44)
Direct BP source: Metatarsal artery
NIBP cuff location: Median artery
Oscillometric technology: Cardell Veterinary Monitor 9402, CAS Medical
MAP	10	−10.8	8.8	NR	NR	NR
Anesthetized foals (44)
Direct BP source: Metatarsal artery
NIBP cuff location: Metatarsal artery
Oscillometric technology: Cardell Veterinary Monitor 9402, CAS Medical
MAP	10	−4.1	8.8	NR	NR	NR
Anesthetized horses (41)
Direct BP source: Transverse facial artery
NIBP cuff location: Coccygeal artery
Oscillometric technology: Cardell 9401 BP Monitor
MAP	6	0.39	2.96	NR	NR	NR
Conscious horses (40)
Direct BP source: Facial or transverse facial artery
NIBP cuff location: Coccygeal artery
Oscillometric technology: Datex-Ohmeda B30, GE Healthcare
SAP		−8	17
MAP	7	−4	10	NR	NR	NR
DAP		−7	14
Anesthetized horses (56)
Direct BP source: Facial or transverse facial artery
NIBP cuff location: Coccygeal artery
Oscillometric technology: Cardell Veterinary Monitor 9402, CAS Medical
SAP		3.3	8.5	0.92	80	95
MAP	8	0.5	12.0	0.81	55	95
DAP		0.6	11.6	0.76	70	90
Conscious horses (56)
Direct BP source: Facial or transverse facial artery
NIBP cuff location: Coccygeal artery
Oscillometric technology: Cardell Veterinary Monitor 9402, CAS Medical
SAP		30.0	24.9	0.84	17	34
MAP	8	16.4	16.6	0.88	31	72
DAP		8.9	17.5	0.84	52	79
Anesthetized horses (43)
Direct BP source: Facial or metatarsal artery
NIBP cuff location: Coccygeal artery
Oscillometric technology: Datex Ohmeda S/5 Compact
SAP		2.96	12.69
MAP	40	3.78	8.77	NR	NR	NR
DAP		2.30	8.65

NR — Not reported. Highlighted values meet validation criteria.

In anesthetized and conscious foals 2 studies found oscillometry to provide an acceptable estimate of mean arterial BP when measured from the tail in comparison to direct mean arterial BP measured from the metatarsal artery regardless of the monitor used (ProPaq Encore, Cardell or Dinamap) (44,45) (Table 4). The lowest bias (−1.07 mmHg) and narrowest limits of agreement (−9.39 to 7.25 mmHg) were identified for the ProPaq Encore monitor (45), although all 3 monitors were clinically acceptable for estimation of mean arterial BP.

Oscillometry in ruminant species

The authors are aware of only 4 studies evaluating NIBP measurement techniques in ruminant species; all of which evaluated oscillometry in anesthetized animals using 3 different monitors (46–49). The Datascope Passport Monitor was evaluated in anesthetized alpacas, llamas (46), and sheep, goats, and cattle (48) comparing NIBP measured via a cuff placed on the metacarpal artery to direct arterial BP readings from the auricular artery in most animals, or the medial saphenous artery of some camelids (Table 5). Both studies identified significant variability and wide limits of agreement in NIBP measurements, leading the authors to conclude that oscillometry cannot be recommended as an alternative to invasive BP monitoring in these species (46,48). Two other monitors have been evaluated in sheep anesthetized for concurrent prospective surgical studies (47,49). The petMAP oscillometric BP monitor demonstrated similar findings in anesthetized sheep with narrow limits of agreement when the BP cuff was placed over the metatarsal artery or metacarpal artery and compared to direct arterial BP readings from the auricular artery (49), but did not meet the AHCP-VBPS validation criteria for other parameters. Good agreement was also found for non-invasive oscillometric BP measured in sheep by the Surgivet V9203 monitor using a cuff placed on the median artery or metatarsal artery in comparison to direct arterial BP readings from the auricular artery (47) (Table 5). In this study, the Surgivet V9203 monitor came very close to meeting all the AHCP-VBPS validation criteria.

Table 5.

Published studies evaluating oscillometric non-invasive blood pressure measurement in domestic ruminants in comparison to the American College of Veterinary Internal Medicine (ACVIM) criteria for technique validation.

Parameter	Number of animals	Bias (mmHg)	Standard deviation (mmHg)	Correlation	< 10 mmHg (% of measurements)	< 20 mmHg (% of measurements)
ACVIM criteria	8	≤ 10	≤ 15	≥ 0.9	≥ 50	≥ 80
Oscillometry
Anesthetized camelids (46)
Direct BP source: Auricular or medial saphenous artery
NIBP cuff location: Metacarpal artery
Oscillometric technology: Datascope Passport
SAP		−9.9	21.9
MAP	20	−2.9	17.0	NR	NR	NR
DAP		1.8	15.6
Anesthetized sheep (47)
Direct BP source: Auricular artery
NIBP cuff location: Median or metatarsal artery
Oscillometric technology: SurgiVet Advisor Vital Signs monitor V9203, Smiths Medical PM
SAP		3	8	0.87	79	97
MAP	20	−7	6	0.90	69	100
DAP		−10	7	0.86	48	92
Anesthetized sheep and goats (48)
Direct BP source: Auricular artery
NIBP cuff location: Metacarpal artery
Oscillometric technology: Datascope Passport
SAP		0	16
MAP	20	8	13	NR	NR	NR
DAP		13	16
Anesthetized cattle < 150 kg (48)
Direct BP source: Auricular artery
NIBP cuff location: Metacarpal artery
Oscillometric technology: Datascope Passport
SAP		0	19
MAP	20	4	16	NR	NR	NR
DAP		6	18
Anesthetized cattle > 150 kg (48)
Direct BP source: Auricular artery
NIBP cuff location: Metacarpal artery
Oscillometric technology: Datascope Passport
SAP		−18	32
MAP	20	−5	28	NR	NR	NR
DAP		7	29
Anesthetized sheep (49)
Direct BP source: Auricular artery
NIBP cuff location: Metacarpal artery
Oscillometric technology: PetMap, Ramsey Medical
SAP		0	12		70.2	91.7
MAP	13	−10	11	0.87	44.6	NR
DAP		−16	13		NR	NR
Anesthetized sheep (49)
Direct BP source: Auricular artery
NIBP cuff location: Metatarsal artery
Oscillometric technology: PetMap, Ramsey Medical
SAP		12	13		NR	NR
MAP	13	−4	12	0.83	61.2	91.7
DAP		−11	14		NR	NR

NR — not reported. Highlighted values meet validation criteria.

Oscillometry in exotic species

In 2 previously mentioned studies in avian species (22,23), the oscillometric Cardell Veterinary Blood Pressure monitor failed to provide any measurements in either of the evaluated locations and was therefore excluded from statistical analysis, leading the authors to conclude that the use of this monitor could not be recommended in avian species (22). In conscious and anesthetized red-tailed hawks (Buteo jamaicensis), the study also demonstrated that the Cardell monitor performed poorly, with 54% of measurements failing to return a reading; thus the authors did not perform a statistical analysis (23).

It has been reported that NIBP measurement obtained via the oscillometric Dash 3000 Patient Monitor in anesthetized rabbits demonstrated better correlation with direct arterial BP readings from the abdominal aorta, although it tended to underestimate the BP measurements. Unfortunately, this study does not report numerical values for level of agreement making conclusions regarding the monitor’s suitability as a substitute for direct arterial BP monitoring difficult (50).

Oscillometric BP measurement in anesthetized boid snakes using the Cardell Veterinary Monitor with the BP cuff placed just distal to the vent was found to underestimate mean and diastolic arterial BP, and overestimate systolic arterial BP, in comparison with direct arterial BP readings from the aortic arch (51). The significant bias ± SD (3.71 ± 15.29 mmHg for systolic arterial BP, −14.75 ± 10.37 mmHg for mean arterial BP, and −26.46 ± 7.70 mmHg for diastolic arterial BP) and wide limits of agreement (−26.26 to 33.69 mmHg for systolic arterial BP, −35.08 to 5.59 mmHg for mean arterial BP, and −41.56 to −11.37 mmHg for diastolic arterial BP) led the authors to conclude that this measurement technique could not be used as a substitute for invasive BP monitoring in this species (51). The performance of the monitor in this species did not meet any of the AHCP-VBPS validation criteria.

High definition oscillometry in veterinary species

With claims of increased accuracy of high definition oscillometric monitors (HDO), studies have begun to be published evaluating its use in canine patients (10,52). However, the technology has not been found to perform much better than traditional oscillometric monitors. In anesthetized dogs, and in comparison to direct arterial BP readings from the dorsal pedal artery, HDO demonstrated better agreement with mean arterial BP while performing poorest when measuring systolic arterial BP. While both studies identified an acceptable bias for mean arterial BP [−0.5 mmHg (10) and −1 mmHg (52)], the wide limits of agreement in both [−20 to 20 mmHg (10) and −22 to 19 mmHg (52)] demonstrated poor precision of the monitor. Similar results were identified for systolic and diastolic arterial BP values. The HDO was also found to overestimate hypotension, whether the oscillometric cuff was placed over the coccygeal artery (52) or the median artery (10). The monitor only met AHCP-VBPS validation criteria for the bias from these 2 studies (Table 6).

Table 6.

Published studies evaluating high definition oscillometric non-invasive blood pressure measurement in comparison with the American College of Veterinary Internal Medicine (ACVIM) criteria for technique validation.

Parameter	Number of animals	Bias (mmHg)	Standard deviation (mmHg)	Correlation	< 10 mmHg (% of measurements)	< 20 mmHg (% of measurements)
ACVIM criteria	8	≤ 10	≤ 15	≥ 0.9	≥ 50	≥ 80
Anesthetized dogs (10)
Direct BP source: Dorsal pedal artery
NIBP cuff location: Median or coccygeal artery
SAP		7			36	70
MAP	20	−0.5	NR	NR	67	95
DAP		−7			52	87
Anesthetized dogs (52)
Direct BP source: Dorsal pedal artery
NIBP cuff location: Coccygeal artery
SAP		5
MAP	50	−1	NR	NR	NR	NR
DAP		3
Conscious cats (53)
Direct BP source: Femoral artery
NIBP cuff location: Coccygeal artery
SAP		−2.2	1.1	0.92	88	96
MAP	6	NR	NR	NR	NR	NR
DAP		22.3	1.6	0.81	13	38
Anesthetized cheetahs (55)
Direct BP source: Dorsal pedal artery
NIBP cuff location: Coccygeal artery
SAP		−3.2	18.2	0.88	33.8	73.0
MAP	8	1.1	12.4	0.92	66.9	95.3
DAP		−0.04	14.6	0.88	55.4	89.9
Anesthetized cheetahs (55)
Direct BP source: Femoral artery
NIBP cuff location: Coccygeal artery
SAP		−10.4	13.8	0.93	38.9	77.8
MAP	8	−1.2	11.1	0.95	75.9	96.3
DAP		−1.8	13.4	0.91	60.2	92.6
Anesthetized horses (39)
Direct BP source: Facial artery
NIBP cuff location: Coccygeal artery
MAP < 60 mmHg
SAP		−20.0	20.9
MAP		−11.4	19.6
DAP		−4.7	20.1
MAP 60–110 mmHg
SAP		0.1	19.6
MAP	7	0.5	14.0	NR	NR	NR
DAP		4.7	15.6
MAP > 110 mmHg
SAP		26.1	37.3
MAP		4.2	19.4
DAP		1.5	16.8
Inhalant-anesthetized horses (42)
Direct BP source: Facial artery
NIBP cuff location: Coccygeal artery
SAP		3.5	13.6		63.3
MAP	24	6.3	10.0	NR	75.0	NR
DAP		7.8	13.6		59.5
Injectable-anesthetized horses (42)
Direct BP source: Facial artery
NIBP cuff location: Coccygeal artery
SAP		3.8	28.3		37.2
MAP	24	4.0	23.3	NR	33.6	NR
DAP		4.0	21.2		38.7

NR — Not reported. Highlighted values meet validation criteria.

In awake cats, the monitor reportedly performed well when measuring systolic arterial BP with the oscillometric cuff placed over the coccygeal artery, in comparison with direct arterial BP readings measured from the femoral artery (53). The authors concluded that their study findings validate this monitor for measurement of systolic arterial BP in cats; however, the monitor cannot in fact be validated based on the results of this study because it failed to meet the criteria for the minimum number of animals (3) (Table 6). Furthermore, the authors do not report bias or limits of agreement for mean arterial BP measured via HDO in comparison with direct arterial BP values. In anesthetized cats, HDO overestimated the degree of hypotension, which has important clinical implications, when the cuff was placed on the antebrachium over the median artery and compared to direct arterial BP readings taken from the dorsal pedal artery. Despite an acceptable bias, the limits of agreement were very wide (−52.9 to 32.2 mmHg for systolic arterial BP, −32.9 to 51.2 mmHg for mean arterial BP, and −32.1 to 58.0 mmHg for diastolic arterial BP), similar to the results in dogs, demonstrating poor precision of the monitor in cats as well (35). An additional study evaluating HDO in anesthetized cats also concluded that the device overestimated hypotension (54). This latter study was in comparison to Doppler ultrasonic flow detection rather than direct arterial BP readings and therefore final conclusions are difficult. Based on the current studies, the monitor does not meet the AHCP-VBPS validation criteria for NIBP evaluation in cats (Table 6).

High definition oscillometric monitor (HDO) readings measured from the coccygeal artery have been recently evaluated in anesthetized cheetahs (Acinonyx jubatus) in comparison with direct arterial BP readings measured from the femoral or dorsal pedal artery (55). The best agreement was identified with directly measured dorsal pedal arterial BP and HDO provided the best estimate of mean arterial BP; however, the limits of agreement in the study demonstrate that the precision of the monitor is also poor in this species (55). The monitor did meet a number of AHCP-VBPS validation criteria (Table 6).

In horses, HDO has only been evaluated in 2 studies (39,42). One study evaluated the performance of the HDO during hypotension (mean arterial BP < 60 mmHg), normotension (mean arterial BP 60 to 110 mmHg) and hypertension (mean arterial BP > 110 mmHg) via pharmacologic manipulation of arterial BP in healthy adult horses (39). This study identified that the monitor demonstrated the best agreement between systolic and mean arterial BP measured non-invasively via the coccygeal arterial and directly via the facial artery during normotension, but underestimated hypertension and overestimated hypotension. This led the authors to conclude that the monitor is unreliable during hemodynamic instability and direct arterial BP monitoring in horses was recommended (39). Recently, the monitor’s performance was evaluated during inhalant versus total intravenous anesthesia and it was found that variability of non-invasively measured BP was greater during total intravenous anesthesia, which is of important clinical relevance in horses, although the authors did not advise against its use (42). The limits of agreement from both studies demonstrate poor precision of the monitor however; the monitor did meet the AHCP-VBPS validation criteria for use in isoflurane-anesthetized horses for those values that were reported (Table 6).

In canine patients, Doppler provides an estimate of systolic arterial BP but it is likely to poorly predict hypotension in anesthetized dogs (11) and should not be used as a substitute for direct arterial BP measurement in high-risk cases. In dogs weighing < 5 kg, Doppler provides a better estimate of direct systolic arterial BP but it is likely to overestimate it (12,13). In cats, Doppler provides a good estimate of direct mean arterial BP (14,15). Doppler may, or may not, have clinical utility for NIBP measurement in exotic species. In rabbits, Doppler provides a good estimate of direct systolic arterial BP and performs well in identifying hypotension (24). Doppler has not been well-studied in horses or other large animal species.

Oscillometric BP measurement depends significantly on the monitor that is being used. The Cardell Veterinary Blood Pressure monitor provides a good estimate of mean arterial BP especially during normotension in dogs (28) and cats (16,35). The Surgivet monitor also provides a good estimate of mean arterial BP and accurately predicts hypotension in canine patients (31,32) and good agreement with direct arterial BP readings in ruminant species (47). The petMAP monitor has poor precision in studies evaluating its use in dogs (8,29,30), cats (35,37), and ruminant species (49), and cannot be recommended for clinical use. In large animal species, oscillometric BP monitors in general demonstrate a high degree of variability and are not appropriate substitutes for direct arterial BP monitoring (41,43,46,48,49). In adult horses, oscillometric cuff placement over the coccygeal artery at the base of the tail (40) and in foals oscillometric cuff placement over the metatarsal artery (44,45) provide the most appropriate location for estimation of mean arterial BP. In the few studies evaluating oscillometric BP measurement in exotic species, the technology performs poorly (22,23,51) and cannot be recommended as a substitute for direct arterial BP evaluation.

With respect to HDO, the performance of this technology does not differ much from that of traditional oscillometric monitors, demonstrating the best agreement with direct mean arterial BP and the poorest agreement with direct systolic arterial BP (52,57). High definition oscillometric monitors demonstrate (HDO) consistently poor precision across species in which it has been evaluated (10,35,39,42,52,53,55). Of significant clinical importance, in anesthetized dogs (10,52), cats (35,54), and horses (39,42), HDO has been consistently found to overestimate arterial BP during periods of hypotension meaning that significantly low arterial BP may go unidentified if this monitor is utilized as the sole agent for trending arterial BP values. CVJ