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  • Author or Editor: Pierre M. Lekeux x
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Abstract

Objective—To characterize the accuracy of an ultrafine 99m-technetium-labeled carbon dry aerosol for use in assessment of regional ventilation in calves with pulmonary dysfunction.

Animals—7 Belgian White and Blue calves.

Procedure—The ultrafine aerosol was assessed by comparing deposition (D) images with ventilation (V) images obtained by use of 81m-krypton (81mKr) gas via D-to-V ratio (D:V) image analysis in calves during spontaneous breathing (SB) and during experimentally induced pulmonary dysfunction (ePD).

Results—Mismatching index (LrTot) calculated on the D:V images revealed a good match (LrTot, 0.96 ± 0.01) between D and V distribution patterns in calves during SB. Calculation of the ultrafine aerosol penetration index relative to 81mKr (PIRel) revealed preferential distribution of the ultrafine aerosol in lung parenchyma (PIRel, 1.13 ± 0.11). In ePD, heterogeneity in the D:V distribution was observed (LrTot, 0.78 ± 0.10) as a result of ultrafine aerosol particles impaction in airways as indicated by PIRel (0.66 ± 0.16) and a proportion of pixels more radioactive in D images, compared with V images, that was located in the central part of the lung (47.5 ± 7.7% in ePD vs 32.8 ± 5.7% in SB). However, this central deposition did not prevent visual examination of the entire ventilated lung.

Conclusions and Clinical Relevance—The ultrafine aerosol appears suitable for use in examination of ventilated parts of lungs of cattle, even those with impaired pulmonary function. However, airway impaction of ultrafine aerosol particles impedes the quantification of regional ventilation in cattle with abnormal lung function. (Am J Vet Res 2001;62: 1881–1886)

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in American Journal of Veterinary Research

Abstract

Objective—To use Doppler ultrasonography and singlefiber laser Doppler flowmetry (LDF) to evaluate blood flow in the dependent and nondependent hind limbs of anesthetized horses and to evaluate changes in femoral arterial blood flow and microvascular skeletal muscle perfusion in response to administration of phenylephrine hydrochloride or dobutamine hydrochloride.

Animals—6 healthy adult horses.

Procedure—Horses were anesthetized and positioned in left lateral recumbency. Doppler ultrasonography was used to measure velocity and volumetric flow in the femoral vessels. Single-fiber LDF was used to measure relative microvascular perfusion at a single site in the semimembranosus muscles. Phenylephrine or dobutamine was then administered to decrease or increase femoral arterial blood flow, and changes in blood flow and microvascular perfusion were recorded.

Results—Administration of phenylephrine resulted in significant decreases in femoral arterial and venous blood flows and cardiac output and significant increases in mean aortic blood pressure, systemic vascular resistance, and PCV. Administration of dobutamine resulted in significant increases in femoral arterial blood flow, mean aortic blood pressure, and PCV. Significant changes in microvascular perfusion were not detected.

Conclusion and Clinical Relevance—Results suggest that Doppler ultrasonography and single-fiber LDF can be used to study blood flows in the hind limbs of anesthetized horses. However, further studies are required to determine why changes in femoral arterial blood flows were not associated with changes in microvascular perfusion. (Am J Vet Res 2000;61:286–290)

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in American Journal of Veterinary Research

Abstract

Objective—To evaluate the hemodynamic effects of dobutamine hydrochloride (0.5 µg/kg of body weight/min) in halothane-anesthetized horses.

Animals—6 adult Thoroughbred horses.

Procedure—Anesthesia was induced by use of romifidine (100 µg/kg) and ketamine (2.2 mg/kg), IV. Anesthesia was maintained by halothane (end-tidal concentration 0.9 to 1.0%). Aortic, left ventricular, and right atrial pressures were measured, using cathetermounted strain gauge transducers. Cardiac output (CO), velocity time integral, maximal aortic blood flow velocity and acceleration, and left ventricular preejection period and ejection time were measured from aortic velocity waveforms obtained by transesophageal Doppler echocardiography. Velocity waveforms were recorded from the femoral vessels, using Doppler ultrasonography. The time-averaged mean velocity and early diastolic deceleration slope (EDDS) were measured. Pulsatility index (PI) and volumetric flow were calculated. Microvascular perfusion was measured in the semimembranosus muscles by laser Doppler flowmetry. Data were recorded 60 minutes after induction of anesthesia (control) and at 15 and 30 minutes after start of an infusion of dobutamine (0.5 µg/kg/min).

Results—Aortic pressures were significantly increased during the infusion of dobutamine. No change was observed in the indices of left ventricular systolic function including CO. Femoral arterial flow significantly increased, and the PI and EDDS decreased. No change was observed in the femoral venous flow or in microvascular perfusion.

Conclusions and Clinical Relevance—At this dosage, dobutamine did not alter left ventricular systolic function. Femoral blood flow was preferentially increased as the result of local vasodilatation. The lack of effect of dobutamine on microvascular perfusion suggests that increased femoral flow is not necessarily associated with improved perfusion of skeletal muscles. (Am J Vet Res 2000;61:1282–1288)

Full access
in American Journal of Veterinary Research

Abstract

Objective—To compare sensitivity of the impulse oscillometry system (IOS) with that of the conventional reference technique (CRT; ie, esophageal balloon method) for pulmonary function testing in horses.

Animals—10 horses (4 healthy; 6 with recurrent airway obstruction [heaves] in remission).

Procedure—Healthy horses (group-A horses) and heaves-affected horses (group-B horses) were housed in a controlled environment. At each step of a methacholine bronchoprovocation test, threshold concentration (TC2SD; results in a 2-fold increase in SD of a value) and sensitivity index (SI) were determined for respiratory tract system resistance (Rrs) and respiratory tract system reactance (Xrs) at 5 to 20 Hz by use of IOS and for total pulmonary resistance (RL) and dynamic lung compliance (Cdyn), by use of CRT.

Results—Bronchoconstriction resulted in an increase in Rrs at 5 Hz (R5Hz) and a decrease in Xrs at all frequencies. Most sensitive parameters were Xrs at 5 Hz (X5Hz), R5Hz, and R5Hz:R10Hz ratio; RL and the provocation concentration of methacholine resulting in a 35% decrease in dynamic compliance (PC35Cdyn) were significantly less sensitive than these IOS parameters. The TC2SD for Xrs at 5 and 10 Hz was significantly lower in group-B horses, compared with group-A horses. The lowest TC2SD was obtained for X5Hz in group-B horses and R5Hz in group-A horses.

Conclusions and Clinical Relevance—In contrast to CRT parameters, IOS parameters were significantly more sensitive for testing pulmonary function. The IOS provides a practical and noninvasive pulmonary function test that may be useful in assessing subclinical changes in horses. (Am J Vet Res 2003;64:1414–1420)

Full access
in American Journal of Veterinary Research