Assessment of distribution of ventilation by electrical impedance tomography in standing horses.

The aim was to evaluate the feasibility of using electrical impedance tomography (EIT) in horses. Thoracic EIT was used in nine horses. Thoracic and abdominal circumference changes were also measured with respiratory ultrasound plethysmography (RUP). Data were recorded during baseline, rebreathing of CO2 and sedation. Three breaths were selected for analysis from each recording. During baseline breathing, horses regularly took single large breaths (sighs), which were also analysed. Functional EIT images were created using standard deviations (SD) of pixel signals and correlation coefficients (R) of each pixel signal with a reference respiratory signal. Left-to-right ratio, centre-of-ventilation and global-inhomogeneity-index were calculated. RM-ANOVA and Bonferroni tests were used (P < 0.05). Distribution of ventilation shifted towards right during sighs and towards dependent regions during sighs, rebreathing and sedation. Global-inhomogeneity-index did not change for SD but increased for R images during sedation. The sum of SDs for the respiratory EIT signals correlated well with thoracic (r(2) = 0.78) and abdominal (r(2) = 0.82) tidal circumferential changes. Inverse respiratory signals were identified on the images at sternal location and based on reviewing CT images, seemed to correspond to location of gas filled intestines. Application of EIT in standing non-sedated horses is feasible. EIT images may provide physiologically useful information even in situations, such as sighs, that cannot easily be tested by other methods.

In vitro and in vivo evaluation of a new large animal spirometry device using mainstream CO2 flow sensors.

REASONS FOR PERFORMING STUDY: A spirometry device equipped with mainstream CO2 flow sensor is not available for large animal anaesthesia. OBJECTIVES: To measure the resistance of a new large animal spirometry device and assess its agreement with reference methods for volume measurements. STUDY DESIGN: In vitro experiment and crossover study using anaesthetised horses. METHODS: A flow partitioning device (FPD) equipped with 4 human CO2 flow sensors was tested. Pressure differences were measured across the whole FPD and across each sensor separately using air flows (range: 90-720 l/min). One sensor was connected to a spirometry monitor for in vitro volume (3, 5 and 7 l) measurements. These measurements were compared with a reference method. Five anaesthetised horses were used for tidal volume (VT) measurements using the FPD and a horse-lite sensor (reference method). Bland-Altman analysis, ANOVA and linear regression analysis were used for data analysis. RESULTS: Pressure differences across each sensor were similar suggesting equal flow partitioning. The resistance of the device increased with flow (range: 0.3-1.5 cmH2 O s/l) and was higher than that of the horse-lite. The limits of agreement for volume measurements were within -1 and 2% in vitro and -12 and 0% in vivo. Nine of 147 VT measurements in horses were outside of the ± 10% limits of acceptance but most of these erroneous measurements occurred with VTs lower than 4 l. The determined correction factor for volume measurements was 3.97 ± 0.03. CONCLUSIONS: The limits of agreement for volume measurements by the new device were within ± 10% using clinically relevant range of volumes. The new spirometry device can be recommended for measurement of VT in adult Warmblood horses.

Laryngeal perforation during a standard intubation procedure in a pig.

Pigs are frequently anaesthetized in animal research settings. Due to the unique laryngeal anatomy, endotracheal intubation is demanding in pigs. Several complications associated with endotracheal intubation have been reported in pigs, but laryngeal perforation following difficult intubation has not been documented so far. The present case report describes laryngeal perforation in a three-month-old pig following difficult intubation.

The use of an acoustic device to identify the epidural space in cattle.

Twelve healthy cattle (weighing 188-835 kg) were placed in stocks and sedated with xylazine. Caudal epidural puncture was performed using an acoustic device that indicated a decrease in resistance with a change in pitch. Lidocaine was injected to verify correct needle placement by assessing needle prick stimuli applied on the left and right side of the tail root and the perineal region, and the loss of tail and anal sphincter tone. Pressure measurements were recorded during penetration of the different tissue layers and in the epidural space. A clear and sudden decrease in the pitch of the acoustic signal was audible in all 12 cattle. All cows showed clinical effects indicating successful epidural anaesthesia. The pressure in the epidural space after puncture was -19±10 mm Hg. The device may be of assistance in identifying the epidural space in cattle.

Prolonged recovery and respiratory depression after fentanyl infusion in a sheep undergoing mitral valve reconstruction.

A sheep was anaesthetized for implantation of a novel device (MitroFast) to replace the posterior leaflet of the mitral valve. Anaesthetic management included a balanced anaesthetic protocol and consisted of propofol or isoflurane combined with fentanyl infusion (0.15-0.4 microg/kg/min). Deliberate hypothermia during cardiopulmonary bypass was set at 34.5-35.5 degrees C. Surgery proceeded uneventfully. Total time of aortic cross-clamping was 35 min and total time on extracorporeal circulation was 60 min. Visual inspection, intracardiac pressure testing and transesophageal echocardiography indicated proper functioning of the device. The anaesthetic period was uneventful, but recovery was prolonged with central nervous and respiratory depression and marked hypoxaemia. Administration of naloxone (1.5 microg/kg, repeated twice at 15-20 min intervals) reversed the central nervous and attenuated the respiratory depressions. An initially low rate of urine production normalized after rewarming and a single intravenous administration of furosemide.