In vitro validation of a Pitot-based flow meter for the measurement of respiratory volume and flow in large animal anaesthesia

Objective  To remodel and validate commercially available monitors and their Pitot tube-based flow sensors for use in large animals, using in vitro techniques.
Study design  Prospective, in vitro experiment.
Methods  Both the original and the remodelled sensor were studied with a reference flow generator. Measurements were taken of the static flow-pressure relationship and linearity of the flow signal. Sensor airway resistance was calculated. Following recalibration of the host monitor, volumes ranging from 1 to 7 L were generated by a calibration syringe, and bias and precision of spirometric volume was determined. Where manual recalibration was not available, a conversion factor for volume measurement was determined. The influence of gas composition mixture and peak flow on the conversion factor was studied.
Results  Both the original and the remodelled sensor showed similar static flow–pressure relationships and linearity of the flow signal. Mean bias (%) of displayed values compared with the reference volume of 3, 5 and 7 L varied between −0.4% and +2.4%, and this was significantly smaller than that for 1 L (4.8% to +5.0%). Conversion factors for 3, 5 and 7 L were very similar (mean 6.00 ± 0.2, range 5.91–6.06) and were not significantly influenced by the gas mixture used. Increasing peak flow caused a small decrease in the conversion factor. Volume measurement error and conversion factors for inspiration and expiration were close to identity.
Conclusion  The combination of the host monitor with the remodelled flow sensor allowed accurate in vitro measurement of flows and volumes in a range expected during large animal anaesthesia.
Clinical relevance  This combination has potential as a reliable spirometric monitor for use during large animal anaesthesia.     

Measurement of the puncture profile and extradural pressure of cattle during extradural anaesthesia

ObjectiveTo measure the pressure profile during caudal extradural puncture and subsequent extradural anaesthesia in cattle and to investigate the presence of extradural pressure waves.Study designProspective experimental study.AnimalsEleven cattle aged 4.1 ± 2.5 years (range 0.8 to 8.8 years), with a body weight of 613 ± 162 kg (range 302–840 kg).MethodsCaudal extradural puncture was performed. To measure the extradural pressure profile, the needle was connected to an electronic pressure transducer placed at the height of the base of the tail. The pressure profile was recorded for 3 minutes following extradural puncture. Lack of resistance to injection of saline was assessed. One minute and 10 minutes after extradural anaesthesia with procaine extradural pressure was recorded. Correct extradural needle placement was assessed by clinical response.ResultsThree minutes after extradural puncture the median pressure was ?16 (range ?25 to 25) mmHg. Pressure in the extradural space 1 minute after the lack of resistance, 3 seconds after injection, and 10 minutes after injection was ?15 (?24 to 33) mmHg, 8 (?17 to 84) mmHg, and ?7 (?25 to 27) mmHg respectively. Pressure waves were visible after puncture, after lack of resistance, 3 seconds and 10 minutes after injection, in 4, 6, 8 and 7 cattle respectively. Pressure after testing lack of resistance, after the injection of local anaesthetic, as well as at the end of the measurement, period was significantly higher than baseline. All cattle showed clinical signs indicative of successful extradural needle placement.Conclusion and clinical relevance Extradural pressure was sub-atmospheric in 82% of the animals. Pressure waves were not consistently present before or after extradural injection, which limits their usefulness to confirm correct extradural needle placement. Extradural pressures increase significantly after injection of local anaesthetic solution. However, the clinical significance of the increase in extradural pressures was not clear.     

Relationship between clinical signs and pulmonary function estimated by the single breath diagram for CO(2) (SBD-CO(2)) in horses with chronic obstructive pulmonary disease

The pulmonary health of 66 horses was assessed by a clinical examination and simple supplementary diagnostic methods. Single breath diagrams for CO(2) (SBD-CO(2)) and derived lung function indices were used to determine pulmonary function. The clinical signs in different groups were related to the results of the lung function indices derived from the SBD-CO(2). In horses with moderate to severe chronic obstructive pulmonary disease (COPD), a significant relationship was found between the respiratory frequency and the ratio of Bohr's dead space to the tidal volume (VD(Bohr)/VT), and between the physiological dead space/tidal volume ratio (VD(phys)/VT) and the ratio of the alveolar dead space to the alveolar tidal volume (VD(alv)/VT(alv)), but no significant associations were found between the arterial oxygen tension (P(a)O(2)) and lung function indices derived from the SBD-CO(2). The occurrence of cough, the viscosity of tracheobronchial mucus and the amount of polynuclear neutrophils in tracheobronchial aspirates were significantly related to the expiratory tidal volume (VT), the total expired volume of CO(2) (VCO(2)), VD(Bohr)/VT, VD(phys)/VT and VD(alv)/VT(alv).We conclude that abnormal findings in these clinical parameters indicate a measurable ventilation and perfusion (V(A)/Q) mismatch which is reflected by increases in dead space, VD(Bohr)/VT and VD(phys)/VT as well as VD(alv)/VT(alv).     

Effect of spray volume on the deposition, viability and infectivity of entomopathogenic nematodes in a foliar spray on vegetables

BACKGROUND: Spray volume can influence the amount of free water on the leaf surface and subsequently the ability of entomopathogenic nematodes (EPNs) to move. In this study, an investigation was made of the effect of spray volume (548, 730 and 1095 L ha⁻¹) on the deposition, viability and infectivity of EPNs against Galleria mellonella on savoy cabbage, cauliflower and leek. RESULTS: Increasing spray volume decreased nematode deposition on 7.1 cm² leek leaf discs at a 15° angle with the spray nozzle. Although the number of living nematodes observed on leek after 240 min of exposure was not significantly different between the low-volume application (548 L ha⁻¹) and the high-volume application (1095 L ha⁻¹), a greater infectivity was obtained in the latter application. The higher number of droplets deposited on the leek discs in the high-volume application may have stimulated nematode movement. No significant effect of spray volume was observed on the relative deposition of Steinernema carpocapsae on the bottom side of cauliflower and savoy cabbage leaf discs. In spite of the low S. carpocapsae deposition on the bottom side of the savoy cabbage discs, high infectivity was obtained against G. mellonella. Using the lowest spray volume on savoy cabbage, infectivity decreased with increasing exposure time, while infectivity was not affected by exposure time when a spray volume of 730 L ha⁻¹ or more was used. CONCLUSION: Spray volume is an important application parameter, as it affects nematode infectivity. Future research should investigate the effect of spray volume in the field and its influence on the effect of adjuvants. Copyright © 2012 Society of Chemical Industry     

Parapoxvirus papillomatosis in the muskoxen (Ovibos moschatus): genetical differences between the virus causing new outbreak in a vaccinated herd, the vaccine virus and a local orf virus

Since 1981 a domesticated muskoxen herd had been successfully vaccinated against papillomatosis with homogenated, glutaraldehyde inactivated papilloma tissue. In the fall of 1985 a new clinical outbreak of disease occurred, affecting previously infected as well as vaccinated animals. The purification of parapox virions directly from papilloma tissue and orf scabs collected in a local sheep farm was followed by restriction endonuclease analysis of viral DNA. The morphological identity of purified virus was controlled by electron microscopy. Comparison of restriction endonuclease digests (10 different enzymes) by gel electrophoresis demonstrated that the muskoxen parapoxvirus from the new outbreak 1985 differed considerably from the 2 other isolates (muskoxen 1981 and local orf). The latter viruses demonstrated a high degree of homology, but differences were evident after digestion with the enzyme EcoRI. During metrizamide gradient purification minor bands containing morphologically intact virions were isolated in addition to the major fractions. The restriction enzyme digests indicated that the virions of the minor bands differed from those in the major bands.     

Vertical distribution of the plant-parasitic nematode, Meloidogyne chitwoodi, under field crops

The root-knot nematode Meloidogyne chitwoodi is a severe pest on sandy soils in Belgium and causes quality damage to economically important crops such as carrot, potato and black salsify. Pre-planting soil sampling to detect infestations has proven useful to farmers when taking decisions on the crop rotation. To develop an adequate sampling strategy, the vertical distribution of M. chitwoodi was examined under summer barley, carrot, fodder beet, bean, marigold and black fallow on two fields with a sandy soil. Soil samples were collected at monthly intervals from April 2004 to April 2006. Cores were taken to a depth of 70 cm and split into 10 cm segments. Nematodes were extracted by zonal centrifugation. Fodder beet increased the population of M. chitwoodi immensely; carrot was also a good host. Barley was a moderate host and under bean and marigolds the population decreased. The relative distribution of M. chitwoodi over the different soil layers during two successive years was consistent in each field. The different successions with good, moderate and poor hosts did not influence this distribution significantly. A logistic model was fitted to the mean cumulative percentages of nematodes at increasing soil depth. Farmers are advised to take soil samples for detection of M. chitwoodi immediately after harvest, especially after crops with a long field period. Adapting the depth of the cores taken to the vertical distribution of the population can increase the chances of detection. Our results suggest that this distribution is persistent in crop rotations and depends on field characteristics.     

A tracheal tube-in-tube technique for functional separation of the lungs in the horse.

The tube-in-tube technique for the functional separation of the lungs in intact anaesthetised adult horses is based on fibre-optic-guided left-sided endobronchial intubation avoiding tracheostomy. It facilitates a valid separation of the two lungs despite variability in bronchial and carinal anatomy. No clinical complications that could be related to its use have been seen.