Comparison of Doppler ultrasonic sphygmomanometry, oscillometry and high-definition oscillometry for non-invasive blood pressure measurement in conscious cats

OBJECTIVES

Systemic arterial hypertension is a common occurrence and can have serious adverse consequences in cats. Therefore, measuring blood pressure is very important. There are many indirect blood pressure measurement devices available. This study compared Doppler, oscillometric (petMAP Graphic II, SunTech Vet20, the Cardell Insight-X0000) and high-definition oscillometry devices for the non-invasive measurement of blood pressure in conscious cats.

METHODS

In this prospective study, blood pressure was measured in 32 cats using the different devices according to the recommendations of the American College of Veterinary Internal Medicine Consensus Statement. Blood pressures (systolic blood pressure [SBP], diastolic blood pressure [DBP], mean arterial pressure [MAP]), time to complete measurements, number of attempts needed, coefficient of variation (CV) between the blood pressure measurements of the different devices, ease of completing measurements and apparent stress level of the cat were assessed.

RESULTS

There was a significant difference between devices in the time taken to obtain blood pressure readings and the number of attempts necessary to obtain six reliable measurements. The CV of the Doppler device was significantly smaller than that of the rest of the devices, but there were no other differences between the devices. The mean SBP, DBP and MAP measured by the petMAP device were significantly higher than the measurements from the other devices. The perceived ease of measurement was not significantly different between the various machines. The perceived level of stress of measurement with the Doppler device was significantly higher compared with the other devices but did not lead to an increased SBP.

CONCLUSIONS AND RELEVANCE

Using a Doppler device to measure blood pressure in conscious cats is fast, relatively easy and gives reliable results. A disadvantage is that the Doppler device can only measure SBP, while oscillometric devices also provide DBP and MAP. However, in veterinary medicine, systolic hypertension is considered the most relevant.

Systolic blood pressure measurements with Doppler ultrasonic flow detector and high-definition oscillometry are comparable on population level but show large intra-individual differences in apparently healthy elderly dogs

OBJECTIVE

Agreement of systolic blood pressure measurements (SBP) between noninvasive blood pressure devices in conscious dogs is poorly studied. Situational hypertension is expected in clinics, but studies are lacking. This study aimed to compare SBP measurements obtained with Doppler ultrasonic flow detector (Doppler) versus high-definition oscillometry (HDO) in clinics and at home and to estimate the prevalence of situational hypertension in conscious, apparently healthy elderly dogs.

ANIMALS

122 apparently healthy elderly or geriatric dogs were prospectively recruited.

PROCEDURES

Systolic blood pressure was obtained consecutively with Doppler and HDO techniques in a randomized order per dog, following a standardized protocol. An at-home measurement was advised for in-clinic hypertensive dogs (SBP ≥ 160 mmHg), also using both devices.

RESULTS

Dual measurements were available in 102 dogs. Median SBP was 147.3 mmHg (range, 105 to 239 mmHg) for Doppler and 152.3 mmHg (range, 113 to 221 mmHg) for HDO. Forty-six percent (56/122) were hypertensive, of which 9% (11/122) were hypertensive with both methods. No significant difference was found between the 2 devices in the global study population or within the group of hypertensive dogs. Repeated at-home measurements were performed in 20/56 (35.7%) hypertensive dogs, resulting in a 10 and 26 mmHg lower median SBP value for Doppler and HDO, respectively (P > .05). In-clinic situational hypertension was presumed in 8/20 (40%) dogs.

CLINICAL RELEVANCE

The choice of the noninvasive blood pressure device did not significantly impact SBP results, but large interindividual differences in SBP between techniques occurred. Situational hypertension was frequently observed in clinic.

Comparison between the Parks Medical Doppler and the Mano Médical Vet BP Doppler for recording indirect systemic blood pressure in conscious dogs

Background:

The acquisition of systemic blood pressure (SBP) provides valuable information regarding cardiovascular function and tissue perfusion in human and veterinary species.

Aim:

To evaluate the agreement between Parks Medical Doppler (PMD) and Mano Médical Vet BP (MMVBP) Doppler for assessing SBP in conscious dogs.

Methods:

40 client-owned dogs were prospectively enrolled; SBP measurements were acquired by a single operator using the PMD and then the MMVBP. The mean of five consecutive measurements for each device was classified according to target organ damage (TOD) risk scores (1: <140 mmHg; 2: 140–160 mmHg; 3: 160–180 mmHg; 4: ≥ 180 mmHg).

Results:

Total mean SBP for the devices was not statistically different (p = 0.77). However, the Bland–Altman analysis revealed wide limits of agreement (LoA), with MMVBP slightly underestimating SBP compared to PMD (bias = −0.6 mmHg, 95% LoA: −26.3 to 25.09). Both devices correlated well ( r = 0.8269; p < 0.0001) and had identically acceptable intra-observer repeatability (coefficients of variation = 4.09% for MMVBP and 3.86% for PMD). Four dogs (10%) had a TOD score of 3 by one device but scored <3 with the other.

Conclusion:

A good agreement and correlation was observed between the PMD and the MMVBP, suggesting that both devices can be used interchangeably for assessment of SBP in conscious dogs. The wide LoA observed between both devices was most likely associated with intraindividual variability in SBP over time.

Evaluation of noninvasive blood pressure in anesthetized horses: Bias, limits of agreement, and comparative detection of a predetermined mean blood pressure warranting treatment

Oscillometric blood pressure monitoring may be a practical tool for short procedures or those performed outside of the operating room. Oscillometric and direct blood pressure values in 30 juvenile and adult horses in a clinical setting using mixed effect models were compared. The limits of agreement and percentage errors were also calculated. We evaluated the sensitivity and false positive rate for the oscillometric method to trigger an intervention for treating blood pressure [direct mean arterial pressure (MAP) < 70 mmHg]. Oscillometric MAP and diastolic arterial pressure (DAP) differed from direct values (P < 0.001); systolic arterial pressure (SAP) did not (P = 0.08). Wide limits of agreement were observed. Percentage errors were smaller for SAP (39%) than for MAP and DAP (48% and 72%). The oscillometric monitor indicated there was a requirement for blood pressure treatment with a true positive rate of 82%, consequently, it failed 18% of the times. The false positive rate (unnecessary treatment) was 55%.

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

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.

Assessment of a commercially available veterinary blood pressure device used on awake and anesthetized dogs

OBJECTIVE

To compare results of a commercially available device for oscillometrically measured blood pressure (OBP) with invasively measured blood pressure (IBP) in awake and anesthetized dogs.

ANIMALS

19 adult dogs (mean ± SD body weight, 17.8 ± 7.5 kg).

PROCEDURES

Blood pressures were measured in dogs while they were awake and anesthetized with isoflurane. The OBP was recorded on a thoracic limb, and IBP was simultaneously recorded from the median caudal artery. Agreement between OBP and IBP was evaluated with the Bland-Altman method. Guidelines of the American College of Veterinary Internal Medicine (ACVIM) were used for validation of the oscillometric device.

RESULTS

In awake dogs, mean bias of the oscillometric device was -11.12 mm Hg (95% limits of agreement [LOA], -61.14 to 38.90 mm Hg) for systolic arterial blood pressure (SAP), 9.39 mm Hg (LOA, -28.26 to 47.04 mm Hg) for diastolic arterial blood pressure (DAP), and -0.85 mm Hg (LOA, -40.54 to 38.84 mm Hg) for mean arterial blood pressure (MAP). In anesthetized dogs, mean bias was -12.27 mm Hg (LOA, -47.36 to 22.82 mm Hg) for SAP, -3.92 mm Hg (LOA, -25.28 to 17.44 mm Hg) for DAP, and -7.89 mm Hg (LOA, -32.31 to 16.53 mm Hg) for MAP. The oscillometric device did not fulfill ACVIM guidelines for the validation of such devices.

CONCLUSIONS AND CLINICAL RELEVANCE

Agreement between OBP and IBP results for awake and anesthetized dogs was poor. The oscillometric blood pressure device did not fulfill ACVIM guidelines for validation. Therefore, clinical use of this device cannot be recommended.

Non-invasive blood pressure measurement in animals: Part 1 - Techniques for measurement and validation of non-invasive devices

Arterial blood pressure is a common parameter evaluated in conscious and anesthetized veterinary species. Non-invasive blood pressure measurement techniques, such as Doppler ultrasonic flow detector and oscillometry, are attractive in certain animals 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 summarizes the current techniques available to non-invasively measure arterial blood pressure in animals and discusses 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 data from non-invasive blood pressure devices.

Oscillometric and Doppler arterial blood pressure measurement in conscious goats

The objective of this study was to characterize arterial blood pressure (BP) measurements obtained by using 2 indirect methods, oscillometry and Doppler ultrasonic sphygmomanometry, in conscious goats. Agreement between systolic BP yielded by these 2 methods was then assessed. Sixty female dairy goats aged from 1.5 to 11.8 y (median: 5.5 y) were examined in a standing position with a cuff placed on the tail. All goats had a severe arthritic form of caprine arthritis-encephalitis. Three to 5 repeated measurements of each BP type were averaged for each goat and considered as a final measurement. With oscillometry, systolic blood pressure (O-SBP), diastolic blood pressure, and mean blood pressure, as well as heart rate (HR) were measured, while only systolic blood pressure was measured with Doppler (D-SBP). The O-SBP did not correlate with D-SBP [correlation coefficient (r) = 0.24, P = 0.067]; the mean difference (± standard deviation) was 24.5 ± 26.3 mmHg and limits of agreement were from -27.2 mmHg [95% confidence interval (CI): -39.0, -15.4 mmHg] to 76.1 mmHg (95% CI: 64.3, 87.9 mmHg). No significant linear correlation was found between any BPs and HR (r: -0.10 to 0.22) or age (r: -0.26 to 0.07) of the goats. The study showed that, while BP could be measured in conscious goats using both oscillometry and Doppler ultrasonic sphygmomanometry, the results obtained were so inconsistent that these methods could not be used interchangeably.

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.

Systolic arterial blood pressure estimated by mitral regurgitation velocity, high definition oscillometry, and Doppler ultrasonography in dogs with naturally occurring degenerative mitral valve disease

INTRODUCTION

To determine if systolic blood pressure estimated by mitral regurgitation (MR) velocity can be used interchangeably with that estimated by high definition oscillometry (HDO) and Doppler ultrasonography (DU) in dogs with naturally occurring mitral valve disease (MVD).

ANIMALS

Forty-nine client-owned dogs with naturally occurring MVD.

MATERIALS AND METHODS

This is a retrospective study. Medical records were reviewed and dogs with MR caused by degenerative MVD were included if systolic blood pressure was estimated from MR velocity determined by continuous wave Doppler (CW), DU and HDO at the same visit. A Pearson product moment correlation coefficient was determined for each combination of measures and tested for significance with a paired t-test. Limits of agreement between 2 measures were determined by the 95% confidence interval of the average difference of the means and illustrated by Bland-Altman plots.

RESULTS

Systolic pressure estimated from CW was significantly but only moderately correlated to DU (r = 0.42, p=0.0015) and HDO (r = 0.40, p=0.0021). Pressure estimated from DU was significantly but only moderately correlated to HDO (r = 0.57, p≤0.0001). Limits of agreement were wide for all measures including DU and CW (-61.9to 44.6 mmHg), HDO and CW (-65.2to 26.9 mmHg), and HDO and DU (-63.1 to 42.06 mmHg).

DISCUSSION

Systolic blood pressure estimated by CW cannot be used interchangeably with HDO or DU in dogs with naturally occurring MVD.

Relationship between clinical signs and results of impulse oscillometry in pigs originating from the field

The aim of the present study was to assess the contribution of clinical data to the variability of impulse oscillometric test results observed previously by Püllen et al. (2014). Fifty-eight German hybrid pigs from 29 different herds with unknown respiratory status were examined in the context of routine diagnostics as part of herd health service. Routine clinical examination was extended to a total set of 29 parameters, representing detailed clinical signs of the respiratory system, and to lung function testing applying the impulse oscillometry system (IOS). The resulting linear relationship between clinical data and variables of pulmonary mechanics had a mean r(2) of 0.52. Clinical parameters predominantly representing the lower respiratory tract closely correlated with established impulse oscillometric indices reflecting peripheral airways. Because of a restricted relationship between pulmonary functional disorders and clinical data, additional diagnostic methods are required to reveal the proportion of variance undefined by clinical examination.

[Noninvasive blood pressure measurement using high definition oscillometry in horses with heart diseases]

OBJECTIVE

This study evaluated a device for blood pressure measurement using high definition oscillometry (HDO) for its acceptability and practicability in the horse. Furthermore, we evaluated whether this device can determine differences in blood pressure between healthy horses and horses with heart diseases and between different measurement times.

MATERIAL AND METHODS

The study population consisted of 60 horses (aged 4-31 years). All horses underwent clinical examination, conventional echocardiography (including cardiac output measurement at the pulmonary artery), repeated noninvasive blood pressure measurement at the coccygeal artery (measurement of systolic [SAP], diastolic [DAP] and mean [MAP] arterial blood pressure) and Doppler sonographic measurement of arterial blood flow at the lateral digital artery. Thirty horses were considered to be cardiologically healthy based upon previous examination. In 30 horses, various heart diseases (mitral valve insufficiency, aortic valve insufficiency and atrial fibrillation) were diagnosed. The diurnal variations in blood pressure in 18 healthy horses and 18 horses with heart disease were determined in the morning and evening. In three horses suffering from atrial fibrillation, the blood pressure was determined before and after successful cardioversion.

RESULTS

In healthy horses the following mean blood pressures were found: SAP 118 ± 21 mmHg, DAP 70 ± 19 mmHg and MAP 87 ± 19 mmHg. No significant difference was found between healthy horses and horses with heart diseases. An insufficiency of the aortic valve tended to result in a higher SAP (p = 0.05), whereas atrial fibrillation lowered blood pressure compared to healthy horses. With respect to the diurnal rhythm of the blood pressure, healthy horses displayed a slight increase in the systolic arterial pressure in the evening.

CONCLUSION

The HDO-sphygmomanometer facilitates a straightforward, indirect way to determine blood pressure that delivers meaningful values. However, the method is unsuited to monitor the development or therapy of cardiac diseases.

Interday variation and effect of transportation on indirect blood pressure measurements, plasma endothelin-1 and serum cortisol in Standardbred and Icelandic horses

BACKGROUND

Systemic hypertension is a prominent feature in humans with metabolic syndrome (MS) and this is partly caused by an enhanced endothelin-1 (ET-1) mediated vasoconstriction. There are indications that systemic hypertension might be a feature in equine metabolic syndrome (EMS) but if ET-1 is involved in the development of hypertension in horses is not known. Increased levels of cortisol have also been found in humans with MS but there are no reports of this in horses. Before blood pressure, plasma ET-1 and serum cortisol can be evaluated in horses with EMS, it is necessary to investigate the interday variation of these parameters on clinically healthy horses. The aims of the present study were therefore to evaluate the interday variation and influence of transportation on systemic blood pressure, plasma ET-1 and serum cortisol in healthy Standardbred and Icelandic horses, and to detect potential breed differences.

METHODS

Nine horses of each breed were included in the study. Blood pressure was measured and blood samples were collected between 6 and 9 am on two separate days. Eight of the horses (four of each breed) were transported to a new stable were they stayed overnight. The next morning, the sampling procedure was repeated.

RESULTS

The interday variation was higher for plasma ET-1 (37%) than for indirect pressure measurements (8-21%) and serum cortisol (18%). There were no differences in systemic blood pressure between the two breeds. The Icelandic horses had significantly lower serum cortisol and significantly higher plasma ET-1 concentrations compared to the Standardbred horses. Plasma ET-1 was significantly elevated after transportation, but systemic blood pressure and serum cortisol did not differ from the values obtained in the home environment.

CONCLUSIONS

Indirect blood pressure, plasma ET-1 and serum cortisol are of interest as markers for cardiovascular dysfunction in horses with EMS. The elevated plasma ET-1 concentrations recorded after transportation was likely caused by a stress response. This needs to be considered when evaluating plasma ET-1 in horses after transportation. The differences detected in plasma ET-1 and serum cortisol between the two breeds might be related to differences in genetic setup, training status as well as management conditions.

Comparison of telemetry and high-definition oscillometry for blood pressure measurements in conscious dogs: effects of torcetrapib

This study compared torcetrapib-induced blood pressure (BP) changes simultaneously obtained by high-definition oscillometry (HDO) and telemetry. Male beagles (n = 6) received single oral doses of vehicle or torcetrapib at 10 or 30 mg/kg; BP were acquired simultaneously by HDO and telemetry from 2 h before dosage until 7 h afterward. Systolic, diastolic, and mean arterial pressures (MAP) and heart rate were compared by using Altman-Bland agreement analysis. Dogs were allocated into subgroups according to temperament and baseline MAP (less than 110 mm Hg and 110 mm Hg or greater). Both methods demonstrated high precision. HDO recordings exhibited higher variability for all parameters (inclusive MAP SDs were 7.0 +/- 2.7 mm Hg for HDO compared with 3.4 +/- 1.9 mm Hg for telemetry), accompanied by a positive bias for all pressures (systolic, 10.4 mm Hg; diastolic, 5.7 mm Hg; MAP, 1.9 mm Hg). Both methods detected similar maximal increases in MAP with 30 mg/kg torcetrapib (HDO, 15.8 +/- 10.4 mm Hg; telemetry, 15.8 +/- 5.3 mm Hg). No significant effects were noted for heart rate. Torcetrapib elicited a dose-dependent increase in BP in dogs with baseline MAP of less than 110 mm Hg, whereas increases were maximal with 10 mg/kg in the other group, and dose-dependence was no longer observed. BP changes were influenced by animal temperament, demonstrating that HDO results must be interpreted with caution. HDO may provide a useful and accurate method for noninvasive BP measurements in canine studies.

Within-day and between-day variability of blood pressure measurement in healthy conscious Beagle dogs using a new oscillometric device

OBJECTIVES

The main objective of this study was to determine the within- and between-day variability of blood pressure measurement in dogs using an oscillometric device, pet-MAP.

ANIMALS, MATERIALS AND METHODS

Five healthy conscious adult Beagle dogs were used. The dogs were presented in a random order for examinations and the investigators were blinded to the dogs. Blood pressure was measured using a standardized procedure. Three investigators with the same level of experience, trained for 1 h with pet-MAP the day before starting the study, performed 480 blood pressure measurements in 5 healthy conscious dogs on two different days.

RESULTS

The within- and between-day CVs for systolic blood pressure were 9.0-10.1% and 12.8-16.4%, respectively. The corresponding SD values were 14.7-16.6 mm Hg and 21.0-27.1 mm Hg respectively. For diastolic blood pressure, the within- and between-day CVs were 10.3-14.4% and 14.2-24.9% respectively. The corresponding SD values were 9.7-13.9 mm Hg and 13.0-24.0 mm Hg.

CONCLUSIONS

The within- and between-day CVs for systolic blood pressure, measured with pet-MAP by investigators with a minimal period of training, seem to be acceptable in Beagle dogs without hypertension or hypotension. This study suggests that, using this device, one investigator can be replaced by another under the described circumstances.

Measurement of respiratory function by impulse oscillometry in horses

REASONS FOR PERFORMING STUDY

Due to technical implementations and lack of sensitivity, pulmonary function tests are seldom used in clinical practice. Impulse oscillometry (IOS) could represent an alternative method.

OBJECTIVES

To define feasibility, methodology and repeatability of IOS, a forced oscillation technique that measures respiratory resistance (Rrs) and reactance (Xrs) from 5 to 35 Hz during spontaneous breathing, in horses.

METHODS

Using 38 healthy horses, Rrs and Xrs reference values were defined and influence of individual biometrical parameters was investigated. In addition, IOS measurements of 6 horses showing clinical signs of heaves were compared to those of 6 healthy horses.

RESULTS

Airtightness and minimal dead space in the facemask were prerequisites to IOS testing and standardisation of head position was necessary to avoid variations in Rrs due to modified upper airway geometry. In both healthy and diseased animals, measurements were repeatable. In standard-type breeds, the influence of the horse's size on IOS parameters was negligible. An increase in R5Hz greater than 0.10 kPa/l/sec and R5Hz>R10Hz, combined with negative values of Xrs between 5 and 20 Hz, was indicative of heaves crisis.

CONCLUSIONS

IOS is a quick, minimally invasive and informative method for pulmonary function testing in healthy and diseased horses.

POTENTIAL RELEVANCE

IOS is a promising method for routine and/or field respiratory clinical testing in the equine species.

Qualitative and quantitative evaluation of equine respiratory mechanics by impulse oscillometry

REASONS FOR PERFORMING STUDY

The long-established conventional reference technique (CRT) for measuring respiratory mechanics in horses lacks sensitivity and there is a need for further refinement in new technology, such as the impulse oscillometry system (IOS).

OBJECTIVES

To evaluate the potential use of the IOS as a clinical respiratory function test and compare it to the current CRT in horses suffering from common upper and lower airway dysfunctions.

METHODS

Six healthy horses were tested before and after induction of a unilateral nasal obstruction (UNO) or transient left laryngeal hemiplegia (LLH). Six heaves-affected horses were tested in clinical remission and during a heaves crisis, before and after nebulisation of cumulative doses of a bronchodilator therapy (ipratropium bromide; IPB).

RESULTS

As opposed to the CRT, the IOS was able to detect partial upper airway obstruction (UAO) caused by UNO or LLH in resting horses, without differentiating both conditions. Upper airway obstruction caused an upward shift of resistance (R(rs)) from 5 to 35 Hz without altering reactance (X(rs)). As for the CRT, IOS respiratory parameters measured in heaves-affected horses in crisis differed significantly from values measured during remission. The difference in frequency-dependent behaviour of R(rs) and X(rs) allowed discrimination between upper and lower airway obstructions. Bronchodilator treatment induced significant dose-dependent changes in X(rs) at 5 and 10 Hz, from the first dose. Total pulmonary resistance (RL) and R(rs) at 5 Hz were affected from the second dose and displayed similar sensitivity. Although post treatment RL values were comparable to remission, R(rs) and X(rs) remained significantly different, characterising persistent peripheral obstruction.

CONCLUSIONS

The IOS was more sensitive than the CRT in detecting partial UAO in resting horses and persistent post treatment peripheral dysfunction in heaves-affected horses. The IOS is a sensitive test that provides graded quantitative and qualitative information on disease-induced respiratory dysfunctions as well as on treatment efficiency in horses.

POTENTIAL RELEVANCE

The IOS could represent a practical and sensitive alternative respiratory function test for routine clinical investigations of common airway obstructive diseases and therapy in horses.

Influence of subclinical inflammatory airway disease on equine respiratory function evaluated by impulse oscillometry

REASONS FOR PERFORMING STUDY

Inflammatory airway disease (IAD) is a nonseptic condition of the lower respiratory tract. Its negative impact on respiratory function has previously been described using either forced expiration or forced oscillations techniques. However, sedation or drug-induced bronchoconstriction were usually required. The impulse oscillometry system (IOS) is a noninvasive and sensitive respiratory function test validated in horses, which could be useful to evaluate IAD-affected horses without further procedures.

OBJECTIVES

To determine the sensitivity of IOS in detecting alterations of the respiratory function in subclinically IAD-affected horses without inducing bronchoprovocation and to characterise their respiratory impedance according to frequency for each respiratory phase.

METHODS

Pulmonary function was evaluated at rest by IOS in 34 Standardbred trotters. According to the cytology of bronchoalveolar lavage fluid (BALF), 19 horses were defined as IAD-affected and 15 horses were used as control (CTL). Total respiratory resistance (Rrs) and reactance (Xrs) from 1-20 Hz as well as their inspiratory and expiratory components were compared between groups.

RESULTS

A significant increase of Rrs at the lower frequencies (R1-10 Hz) as well as a significant decrease of Xrs beyond 5 Hz (X5-20 Hz) was observed in IAD compared to CTL horses. IOS-data was also significantly different between inspiration and expiration in IAD-affected horses. In the whole population, both BALF eosinophil and mast cell counts were significantly correlated with IOS measurements.

CONCLUSIONS

Functional respiratory impairment may be measured, even in the absence of clinical signs of disease. In IAD-affected horses, the different parameters of respiratory function (Rrs or Xrs) may vary depending on the inflammatory cell profiles represented in BALF.

POTENTIAL RELEVANCE

Impulse oscillometry could be used in a routine clinical setting as a noninvasive method for early detection of subclinical respiratory disease and of the results of treatment in horses.

Chronobiologic blood pressure assessment: maturation of the daily rhythm in newborn foals

Circadian rhythmicity of physiological processes in animals has been described for some variables. In order to investigate the daily rhythmicity of blood pressure, seven foals (Equus caballus) were used for 40 days after birth. Measurements of blood pressure were done by means of an oscillometric apparatus (Argus TM-7, Schiller, Barr Switzerland) with the foals in a standing position and the cuff placed around the tail. Blood pressure was recorded twice a day, 1 hour before dawn and 1 hour before dusk for the first 10 days of life, every 2 days from the 11th to the 32nd day, on the 36th and on the 40th day. Two-way repeated measures analysis of variance (ANOVA) were used to determine statistically significant differences between the mean values recorded at dawn and dusk during the study. Analysis of variance showed a significant effect of time (p<0.0001), during the first 40 days of life. This study confirms a strong correlation between age and blood pressure in horse and the absence of blood pressure maturation in foals 40 days old. The results on the maturation of the daily rhythm of blood pressure in foals is a contribution to the study of the development of circadian rhythms in mammals. These results are also useful for the chronophysiological assessment of blood pressure in the horse.

Patterns of acoustic variation in Cicada barbara Stål (Hemiptera, Cicadoidea) from the Iberian Peninsula and Morocco

Field recordings of the calling song and of an amplitude modulated signal produced by males of Cicada barbara from North Africa and the Iberian Peninsula were analysed in order to assess the geographical acoustic variation and the potential usefulness of acoustic data in the discrimination of subspecies and populations. Sound recordings were digitized and the frequency and temporal properties of the calls of each cicada were analysed. In all regions studied, peak frequency, quartiles 25, 50 and 75% and syllable rate showed low coefficients of variation suggesting inherent static properties. All frequency variables were correlated with the latitude, decreasing from south to north. In addition, most acoustic variables of the calling song showed significant differences between regions, and PCA and DFA analyses supported a partitioning within this species between Iberian Peninsula+Ceuta and Morocco, corroborating mtDNA data on the same species. Therefore, the subspecific division of C. barbara into C. barbara barbara from Morocco and C. barbara lusitanica from Portugal, Spain and Ceuta finds support from the present acoustic analyses, a result which is also reinforced by molecular markers.

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.

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.

Synchrony during acoustic interactions in the bushcricket Mecopoda 'Chirper' (Tettigoniidae:Orthoptera) is generated by a combination of chirp-by-chirp resetting and change in intrinsic chirp rate

In several bushcricket species, individual males synchronise their chirps during acoustic interactions. Synchrony is imperfect with the chirps of one male leading or lagging the other by a few milliseconds. Imperfect synchrony is believed to have evolved in response to female preferences for leading chirps. We investigated the mechanism underlying synchrony in the bushcricket species Mecopoda 'Chirper' from Southern India using playback experiments and simulations of pairwise interactions. We also investigated whether intrinsic chirp period is a good predictor of leading probability during interactions between males. The mechanism underlying synchrony in this species differs from previously reported mechanisms in that it involves both a change in the oscillator's intrinsic rate and resetting on a chirp-by-chirp basis. The form of the phase response curve differs from those of previously reported firefly and bushcricket species including the closely related Malaysian species Mecopoda elongata. Simulations exploring oscillator properties showed that the outcome of pairwise interactions was independent of initial phase and alternation was not possible. Solo intrinsic chirp period was a relatively good predictor of leading probability. However, changing the intrinsic period during interactions could enable males with longer periods to lead during acoustic interactions.

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 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.

[Non-invasive blood pressure measurement in dogs and cats]

Bloodpressure measurements are of interest for todays veterinary practice. It can be used for screening of incoming patients, the emergency case, the intensive care patient and sedated animal. Furthermore, like in human medicine, blood pressure can be influenced by several diseases. The most reliable method of arterial blood pressure measurement is the direct or invasive method. Only the non-invasive methods doppler and oscillometric methods are used in veterinary medicine. The article describes the method of measurement, and provides a review of the literature. The oscillometric method especially in dogs. Both methods measure a lower bloodpressure if compared with an invasive method. The difference in bloodpressure is for the oscillometric method in cats greater then in dogs and appears to increase at higher blood pressures. Keeping these facts in focus, and if one is able to work in a quiet environment, repeat the measurements and maintain a critical attitude, blood pressure measurements can be performed in veterinary practice.

Hypertension in renal disease: Diagnosis and treatment

Hypertension is a common sequela to renal disease in cats and dogs, affecting as many as 61% cats and 93% of dogs, respectively. Undiagnosed and untreated, elevations in blood pressure can have deleterious effects on the brain and heart as well as promote further renal injury. In this article, we discuss the identification of patients at risk for hypertension as well as methods for measuring blood pressure and the treatment of hypertensive patients.

Influence of breathing pattern and lung inflation on impulse oscillometry measurements in horses

The objective of this paper was to determine if changes in ventilation patterns could influence the outcome of respiratory function measurements performed with our impulse oscillometry system (IOS) in horses. In a first study, IOS tests were performed in vitro on six isolated equine lungs. Lung inflation levels were controlled by modifying depressurisation inside an artificial thorax and different ventilation patterns were imposed. In a second in vivo study, transient variations in breathing pattern were evaluated both with the IOS and a current reference technique (CRT) in five healthy mature horses after an intravenous (i.v.) injection of lobeline hydrochloride. In both studies, respiratory rate (RR, range: 7-42 breaths/min.) and tidal volume (V(T), range: 0.4-25 L) had minor or no influence on IOS parameters. The influence of lung inflation, most marked for resistance at 5 Hz (R(5 Hz)), was limited for the considered physiological range. In vivo, statistical models indicated that maximal changes in pleural pressure (Max Delta Ppl) and peak flows were the main determinants of the variability of the resistance (R(rs)) and the reactance (X(rs)) of the respiratory system. The fourfold increase in baseline Max Delta Ppl and peak flows obtained during hyperpnoea caused a significant increase in R(rs) at 5 and 10 Hz and a decrease in X(rs) at all frequencies. We conclude that IOS parameters are not influenced by tachypnoea, but will reflect alterations in respiratory mechanics caused by hyperpnoeic breathing.

Respiratory mechanics in conscious swine: effects of face mask, head position and bronchoconstriction evaluated by impulse oscillometry

Airway obstruction in pigs (sedated or non-sedated) fixed in a sling was studied using impulse oscillometry (IOS). (i) Vertical flexion of the pig's head was used to simulate an artificial obstruction of the upper airways. (ii) Bronchial obstruction was induced by inhaling differing quantities of an aerosol produced from 0.33% carbachol solution. The ventilatory pattern was examined by measuring respiratory rate (RR) and tidal volume (V(t)). To evaluate respiratory mechanics, impedance parameters resistance (R) and reactance (X) as well as coherence (Co) were examined, each at frequencies of 5, 10, 15, 20, 25 and 35 Hz. Using a simple 7-element-model introduced by J. Mead [Physiological Review 41 (1961) 281], distal respiratory resistance (R(dist)), proximal airway resistance (R(prox)), and additional shunt compliance (C(a)) of the animal's snout and the air inside the facemask were evaluated. By fitting this model to the primary measured impedance spectra, the influence of the face mask could be eliminated in the model calculation to allow assessment of the real respiratory impedance. This recalculation made clear that the facemask had an influence on the spectral course of R and X, depending on the clinical situation, and the upper frequency range was altered the most. Under conditions of (i) upper airway obstruction, especially the X values were distorted by facemask almost over the whole frequency range. Once the data were corrected for the mask, resistance was increased across all frequencies by a fixed amount while reactance was not affected. Under (ii) bronchial airway obstruction (bronchospasm) caused the resistance spectrum to be increased mainly in the lower frequency range. This became visible in both, originally measured impedance spectra and spectra after correction of the mask influence. The reactance course (originally measured and recalculated) decreased at all frequencies during bronchospasm. Coherence over the whole frequency range was lowered at both bronchial and upper airway obstruction.

Effect of aerosolized albuterol sulfate on resting energy expenditure determined by use of open-flow indirect calorimetry in horses with recurrent airway obstruction

OBJECTIVE

To evaluate effects of sedation on stability of resistance of the respiratory system (RRS) and measures of resting energy expenditure (REE) by use of open-flow indirect calorimetry (IC) and treatment with aerosolized albuterol on REE in horses with recurrent airway obstruction (RAO).

ANIMALS

9 clinically normal horses and 8 horses with RAO.

PROCEDURE

In phase 1, RRS was measured by using forced oscillometry (FOT) in 5 clinically normal horses before and after sedation with xylazine. In phase 2, REE was measured in 4 clinically normal horses between 20 and 25 minutes and again 35 to 40 minutes after sedation with xylazine. In phase 3, IC was performed between 20 and 25 minutes and FOT was performed between 30 and 35 minutes after xylazine administration in 8 horses with RAO; after administration of 450 microg of albuterol, IC and FOT were repeated.

RESULTS

In phase 1, RRS values were significantly lower 5 and 10 minutes after sedation. In phase 2, diminishing sedation did not significantly affect REE. In phase 3, there was a significant decrease in mean RRS (1.15 +/- 0.25 vs 0.84 +/- 0.14 cm H20/L/s) and REE (30.68 +/- 17.89 vs 27.46 = 16.54 kcal/kg/d) after albuterol administration.

CONCLUSIONS AND CLINICAL RELEVANCE

FOT and IC are useful in obtaining repeatable measurements of RRS and REE, respectively, in sedated horses. Concurrent bronchodilation and decreased REE after albuterol administration suggest that increased work of breathing as a result of airway obstruction may contribute to increased energy demands in horses with RAO.

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 arterial blood pressure measurement in nonsedated Irish wolfhounds: reference values for the breed

Arterial blood pressure measurements were obtained from 158 healthy Irish wolfhounds using the oscillometric technique to establish reference values for the breed. In contrast to other sight hounds, Irish wolfhounds have low arterial blood pressure. Mean systolic pressure for the group was 116.0 mm Hg. Mean diastolic pressure was 69.2 mm Hg, and the mean value for mean arterial pressure was 87.8 mm Hg. Blood pressure measurements were higher in older wolfhounds than in young dogs. There was no difference between systolic and mean arterial blood pressures in lateral recumbency compared to standing position. However, diastolic pressure was slightly lower when standing. Calm dogs had lower pressure than anxious wolfhounds. There was a significant interaction between the effects of age, gender, and mood on systolic, diastolic, and mean arterial blood pressure values.

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

OBJECTIVE

To determine accuracy of an oscillometric blood pressure monitor used over a wide range of pressures in anesthetized cats.

DESIGN

Prospective study.

ANIMALS

6 healthy cats.

PROCEDURE

4 female cats and 2 male cats that weighed 2.7 to 4.5 kg (5.9 to 9.9 lb) and were 2 to 8 years old were anesthetized. Blood pressure was measured directly with an arterial catheter placed in the right femoral artery and indirectly from the left antebrachium by use of an oscillometric monitor. A series of diastolic arterial pressure (DAP), mean arterial pressure (MAP), and systolic arterial pressure (SAP) measurements were obtained during hypotension, normotension, and hypertension. Values obtained indirectly and directly were compared.

RESULTS

The oscillometric monitor was accurate for DAP and MAP throughout the entire pressure range and met the standards of the Association for the Advancement of Medical Instrumentation (mean +/- SD difference from values obtained directly, < or = 5 +/- 8 mm Hg). The SAP was increasingly underestimated with increasing overall pressure; mean differences from direct measurements were -5.2, -12.1, and -17.7 mm Hg during hypo-, normo-, and hypertension, respectively. Standard deviations for SAP were all < or = 8 mm Hg. The monitor gave readings during all attempts. The direct blood pressure recording system appeared to perform well with neither under- nor overdamping.

CONCLUSIONS AND CLINICAL RELEVANCE

Except for a minor underestimation of SAP during normo- and hypertension, the oscillometric monitor yielded reliable and easily obtainable blood pressure measurements in anesthetized cats.

Comparative evaluation of ultrasonography and lung function testing with the clinical signs and pathology of calves inoculated experimentally with Pasteurella multocida

Seventeen calves were inoculated intratracheally with Pasteurella multocida 0 on three consecutive days with 10 ml of an inoculum containing 10(9) colony forming units/ml per day per calf. Before the first inoculation and 24 hours after the third, each calf was examined non-invasively by means of a clinical examination, chest ultrasonography, and impulse oscillometry to measure the impedance of the respiratory system. The inoculation of P multocida caused fever and a significant increase in respiratory rate and a decrease in tidal volume. There were also significant changes in the ultrasonographic results and in the impedance of the respiratory system. The percentage of the total surface area of the lungs showing pathological changes when the calves were euthanased 48 hours after the third inoculation ranged from 0.4 to 39 per cent. There were statistically significant correlations between the ultrasound scores and the pathological findings and between the ultrasound scores and the respiratory rate and tidal volume. The changes in the impedance of the respiratory system were not correlated with either the ultrasonographic or the pathological findings.

Substrate vibrations during acoustic signalling in the cicada Okanagana rimosa

Males of the North American cicada Okanagana rimosa (Homoptera: Cicadidae, Tibicininae) emit loud airborne acoustic signals for intraspecific communication. Specialised vibratory signals could not be detected; however, the airborne signal induced substrate vibrations. Both auditory and vibratory spectra peak in the range from 7-10 kHz. Thus, the vibrations show similar frequency components to the sound spectrum within biologically relevant distances. These vibratory signals could be important as signals involved in mate localization and perhaps even as the context for the evolution of the ear in a group of parasitoid flies.

Analysis of respiratory mechanics by impulse oscillometry in non-sedated and diazepam-sedated swine

Analysis of respiratory mechanics using impulse oscillometry is applicable to sedated, or non-sedated (trained) pigs when they are fixed in a sling. In this study, the influence of the following sources of variability on measurement results was examined: (i) sedation with diazepam; (ii) body weight of animals (ranging in age: 40 to 102 days); and (iii) time of the measurement (circadian influences). The following parameters were examined: respiratory rate (RR), tidal volume (v(t)), spectral resistance, reactance and coherence, each at 5, 10, 15 and 20 Hz (R5,...R20, X5,...X20, CO5...CO20, respectively), distal respiratory resistance (Rdist), and proximal airway resistance (Rprox). After sedation (using 1.5 mg diazepam per kg body weight), RR and v(t) decreased significantly. There was a significant improvement of CO5, CO10 and CO15. Increase in body weight was strongly correlated to v(t), furthermore to spectral resistance parameters. Impulse oscillometry system (IOS) parameters showed only slight non-significant alterations in dependency on the time of day. In consequence, different sources of variability must be taken into account when performing IOS measurements in swine.

Mechanics of the respiratory system in healthy newborn calves using impulse oscillometry

Arterial blood gases, acid-base balance and respiratory function tests using impulse oscillometry (IOS) were performed on 40 clinically healthy newborn calves during the first 24 hours of life to evaluate their respiratory adaptation to extrauterine life. Gas exchange efficiency of the lung was significantly improved with time and was accompanied by the correction of the mixed acidosis observed at birth and by significant changes in respiratory mechanics. Major changes were detected within the first 6 hours. The significant decrease in resistance (R) and the increase in reactance (X) with time, demonstrate the improvement in respiratory mechanics of both upper and lower airways, and reflect the increase in lung volume, the improved lung tissue elasticity and/or distribution of the ventilation. Respiratory mechanical, arterial blood gases and acid-base balance data provided in this study describe a successful respiratory adaptation to extrauterine life in healthy newborn calves.

Clinical comparison of three methods to measure blood pressure in nonsedated dogs

OBJECTIVE

To determine arterial blood pressure in client-owned dogs, using direct arterial puncture, oscillometry, and Doppler ultrasonography in a clinical setting.

DESIGN

Prospective study.

ANIMALS

8 clinically normal client-owned dogs.

PROCEDURE

Blood pressures of nonsedated dogs were measured simultaneously, using each of the 3 methods. Mean values obtained were compared with published mean values. Ability of noninvasive methods (Doppler ultrasonography and oscillometry) to accurately predict results of the invasive method, and relationships between blood pressure and age, body weight, and degree of patient anxiety were determined.

RESULTS

Calculated ranges of values (mean +/- 2 SD) determined by direct arterial puncture were: systolic pressure, 114 to 194 mm Hg; diastolic pressure, 66 to 102 mm Hg; and mean pressure, 85 to 129 mm Hg. Ranges determined by use of oscillometry were: systolic, 110 to 190 mm Hg; diastolic, 35 to 107 mm Hg; and mean, 78 to 138 mm Hg. Ultrasonographic and oscillometric values did not accurately predict direct values, but mean values of systolic and mean pressures were similar among methods. Relationships were not detected between age or body weight and blood pressure. Significant differences in blood pressure were not detected between anxious and nonanxious dogs.

CONCLUSIONS AND CLINICAL RELEVANCE

Mean values of systolic, diastolic, and mean arterial blood pressure measured in nonsedated client-owned dogs, using invasive and noninvasive methods in a clinical setting, are comparable with those determined for acclimatized, trained, or sedated dogs. However, results of noninvasive methods may not accurately reflect direct values.

Epidemiological study of blood pressure in domestic cats

Blood pressure was measured indirectly in 203 cats using an oscillometric technique in conjunction with a tail cuff. Systolic blood pressure was found to be log normally distributed across the population, while diastolic pressure was log log normally distributed. Blood pressure was found to rise with age (systolic, diastolic, mean arterial and pulse pressure were significantly higher in animals aged 11 years or over than in animals aged under 11 years) but this rise did not parallel an increase in plasma urea or creatinine. Cats with clinical renal disease did however have higher blood pressures than normal cats, as did cats with ocular change consistent with hypertensive retinopathy.

Validation of impulse oscillometry in Friesian and Blue Belgian calves with respect to changes in extrathoracic upper airway resistance

Impulse oscillometry (IOS) was compared with conventional pulmonary function techniques (using oesophageal balloon and airflow measurements). Healthy Friesian (FR) and Blue Belgian (BB) calves were examined in different conditions of extrathoracic airway resistance (physiological and vertical head position). Higher resistance values were detected in BB calves compared with FR calves with both conventional and forced oscillation techniques in both head positions. Upper airway narrowing was characterised by increasing resistance values without changes in frequency dependence. Measuring input impedance in animals using a face mask, a considerable capacitive shunt of the upper airways (including the capacitive components of the mask) has to be taken into account. Even if the absolute value of this capacitive component is constant, its influence on the measurement results increases with growing frequency and with an increase in upper airway resistance. In conclusion, (1) impulse oscillometry is sensitive to upper airway resistance changes and (2) face mask capacitance is important and has frequency dependent effects on the respiratory impedance.

[Review of respiratory mechanics in animals. 3. Methodical and physiologic aspects of the use of the impulse oscilloresistometry system (OIS)]

The impulse oscillometry system (IOS) which was originally developed for human medicine was found to be suitable for analysing respiratory mechanics in spontaneously breathing animals. This technique is non-invasive.

METHODOLOGICAL ASPECTS

In order to use the IOS-technique in animals, a tightly fitting face mask is necessary. Furthermore, a flexible tube needs to be inserted into the measuring system. While the tube does not influence the measured results significantly, the face mask may affect the measurements. Therefore, its influence on the measured respiratory impedance must be taken into account. To prevent methodological errors, the head and body position of the animal should be standardised during the IOS-measurement. Since the methodological variability of the system is very small, the measuring results are highly reproducible. PHYSIOLOGICAL ASPECTS: In growing subjects, all parameters of respiratory mechanics depend on body weight. Since respiratory physiology is influenced by circadian rhythms, measurements of different days are only comparable when they have been done each day at the same hour. Comparing the respiratory impedance of different animals of similar age and body weight, a considerable inter-individual variability was observed. Due to the low level of physiological intra-individual variability, the method seems to be especially useful for studying influences on the respiratory system (i.e. pharmaceutics, therapeutics) in long-term studies using the same group of subjects.

[Review of respiratory mechanics in animals. 4. The diagnostic affirmation ability of research using the impulse oscilloresistometry system (IOS) in calves]

Taking methodological and physiological aspects into account (see Part 3), the impulse oscillometry system (IOS) was found to be sensitive to detecting and to quantifying clinically relevant changes in respiratory mechanics in calves. Therefore, the complex respiratory impedance needs to be measured in terms of resistance and reactance within the frequency range between 5 Hz and 20 Hz. The behaviour of resistance and reactance in dependence of frequency allows to differentiate and to localise airway obstructions. Obstructions of upper (extrathoracic) airways were mainly characterised by a frequency independent increase in the resistance. Within the reactance curve, no change in the resonant frequency could be observed. In a peripheral airway obstruction both resistance and reactance changed. The most typical finding concerning resistance was that a negative frequency dependence occurred. The reactance became more negative. Following this, the resonant frequency increased. With progressive obstruction of the peripheral airways, the reactance became more informative than resistance.

A comparison of indirect blood pressure monitoring techniques in the anesthetized cat

OBJECTIVE

To determine the accuracy of three indirect blood pressure monitoring techniques (oscillometric technique [OS], Doppler [DOP], and optical plethysmography [OP] [blood pressure determined with a pulse oximeter waveform]) when compared with direct arterial pressure measurement in cats.

STUDY DESIGN

Prospective study.

ANIMAL POPULATION

Eight healthy (five female, three male), domestic short-hair cats weighing 3.5 +/- 0.8 kg

METHODS

Cats were anesthetized with isoflurane. The inspired concentration of isoflurane was adjusted to produce mild hypotension (80 to 100 mm Hg direct systolic), moderate hypotension (60 to 80 mm Hg direct systolic), and severe hypotension (< 60 mm Hg direct systolic). Indirect pressure measurements were obtained from the thoracic limb and compared with concurrent direct measurement using regression analysis and a modification of Bland and Altman's technique.

RESULTS

All three techniques underestimated systolic pressure. OS produced the best prediction of systolic pressure with a bias +/- precision of -15.9 +/- 8.1 mm Hg. DOP and OP were relatively inaccurate with a bias +/- precision of -25 +/- 7.4 mm Hg and -25 +/- 7.5 mm Hg. All three techniques correlated well with direct pressure with r values of 0.81, 0.88, and 0.88 for OS, DOP, and OP. DOP and OP provided an accurate prediction of direct mean arterial pressure with a bias +/- precision of -0.8 +/- 6 mm Hg and 0.6 +/- 5.5 mm Hg. Correlation was good between DOP and mean arterial pressure with r = 0.89. Correlation was also good between OP and mean arterial pressure with r = 0.90.

CONCLUSIONS

OS provided the most accurate prediction of direct systolic pressure. DOP and OP provided a good prediction of mean arterial pressure in the cat.

CLINICAL RELEVANCE

All three of these techniques are useful for detecting trends. Direct monitoring of blood pressure should be considered if accurate blood pressure measurement is required.

Measurement of respiratory impedance in healthy calves using the impulse oscillation technique--physiological and methodological aspects

The aim of the present study was to investigate methodological and physiological aspects of complex respiratory impedance measurements in calves using the impulse oscillation technique. To apply the system to animals, a tightly fitting face mask was used. The measuring system was modified by placing a flexible tube between the pneumotachograph and the loudspeaker. Complex respiratory impedance measurements were not significantly influenced by the modification. Linear correlations were found between body weight and respiratory impedance; as body weight increased, resistance decreased and reactance increased. The methodological variability of impedance measurements using the impulse technique was found to be extremely small. Diurnal variations of respiratory impedance were considered to be the main source of intra-individual variability. When comparing different animals (even when healthy and matched for age and body weight) our results suggest that inter-individual biological variability must be carefully considered.

Longitudinal studies of reproducibility and variability of indirect (oscillometric) blood pressure measurements in dogs: evidence for tracking

To be clinically reliable, blood pressure readings taken in quiet surroundings with good technique from healthy, unstressed subjects accustomed to the procedure, should be reasonably constant between occasions. Apart from changes attributable to age or stress, sustained rises suggest hypertension. Yet it is increasingly realised that arterial pressure shows great short-term lability. Despite this, 'tracking' occurs in groups of humans, i.e. when ranked by blood pressure they tend to maintain their rank order. This paper examines month-on-month variability of arterial pressure, measured by non-invasive oscillometry (Dinamap) in both pet dogs and kennel populations. 'Tracking' occurred and there was also evidence of 'white coat' effects. Heart rate was more variable than arterial pressure and should not be used to reject pressure readings unless changes are extreme. There was further evidence that canine blood pressure rises with age.

Comparison of blood pressure measurements obtained in dogs by use of indirect oscillometry in a veterinary clinic versus at home

OBJECTIVE

To compare blood pressure and heart rate measurements performed in a veterinary clinic to similar measurements performed in a dog's home.

DESIGN

Prospective study.

ANIMALS

14 client-owned, clinically normal dogs.

PROCEDURE

Sequential blood pressure and heart rate measurements were recorded from the metatarsus and metacarpus of conscious dogs by indirect oscillometry. Measurements were performed in the dogs' homes and were repeated in a veterinary clinic. Blood pressures and heart rate were derived from 7 serial estimates over 8 to 10 minutes. Statistical differences between the home and clinic and between recording sites were calculated.

RESULTS

Systolic, diastolic, and mean blood pressure and heart rate measurements obtained from the metatarsus and metacarpus in the dogs' homes were significantly lower than measurements from the metatarsus in the clinic, but were similar to measurements from the metacarpus in the clinic. Significant differences were not found between blood pressure measurements from the metatarsus and metacarpus in the dogs' homes, but systolic and mean blood pressure and heart rate measurements from the metacarpus in the clinic were significantly lower than measurements from the metatarsus. Whereas all dogs had normal blood pressure in their homes, 5 of 14 dogs had transient hypertension (systolic pressure > 165 mm of Hg or diastolic pressure > 95 mm of Hg) in the clinic.

CLINICAL IMPLICATIONS

Blood pressure and heart rate measurements obtained in the clinic initially overestimate comparable measurements in a dog's home. The differences are best explained by transient autonomic responses to the stress of the clinic. Blood pressure must be measured by use of standardized techniques on dogs acclimated to the clinic environment.

Comparison of the indirect oscillometric and direct arterial methods for blood pressure measurements in anesthetized dogs

The indirect oscillometric method of blood pressure measurement was compared to the direct arterial puncture method in 15 anesthetized dogs, divided into three weight groups, undergoing a variety of surgical procedures. The objectives of this study were to determine the accuracy of the indirect oscillometric method at a single point in time and when sequential values were averaged. Additionally, the ability to detect systemic hypotension (i.e., mean systemic arterial pressure less than 60 mmHg) was evaluated. The method had the highest correlation coefficient (r of 0.8) when five sequential values were averaged and compared, and it appeared to be sensitive (100%) and specific (91%) for detecting hypotension.

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 (SDD) 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).