Chylothorax associated with pulmonary compressive atelectasis in an emperor tamarin (Saguinus imperator).

Chylothorax is the accumulation of lymph in the thoracic cavity, and it has never been reported in neotropical primates. An emperor tamarin died and at necropsy chylothorax associated with pulmonary compressive atelectasis was diagnosed. Idiopathic chylothorax can be a cause of respiratory insufficiency and death in tamarins.

CT features of rounded atelectasis in chronic inflammatory pleural effusions in cats and dogs.

Rounded atelectasis is well described in human medicine as focal lung deformation and collapse secondary to inflammatory pleural effusions and pleuritis. Specific CT features (round to ovoid soft tissue pulmonary attenuations, creation of an acute angle with the adjoining visceral pleura, and the presence of perinodular comet tail signs) support the diagnosis of rounded atelectasis in humans so that further diagnostic workup is not necessary in defining the nodules. In this retrospective case series, we described the CT characteristics of rounded atelectasis in eight cats and three dogs diagnosed with restrictive pleuritis secondary to either a chylothorax or pyothorax. Thirty-six soft tissue attenuating pulmonary nodular lesions were identified on CT. Comet tail signs, consisting of bundles of bronchi and vessels coalescing into the pulmonary nodules, were associated with 92% of the nodules (33/36), and 92% of the nodules abutted and created an acute angle with the pleura (33/36). Other prevalent features included location in gravity-dependent regions of the lung lobes (33/36, 92%), blurred hilar margins with sharper pleural margins of the nodules (33/36, 92%), presence of air bronchograms (30/36, 83%), homogeneous contrast-enhancement (23/36, 64%), and volume loss of the affected lung lobe (22/36, 61%). Pulmonary malignant neoplasms were not found cytologically (6/11 patients) or histologically (5/11 patients). To avoid a misdiagnosis of neoplasia, veterinary radiologists should be aware of the CT features of rounded atelectasis and consider it as a differential for pulmonary nodular lesions in patients with concurrent inflammatory pleural effusion and pleuritis.

Diagnostic imaging and histopathologic features of rounded atelectasis in four cats and one dog: A descriptive case series study.

In humans, rounded atelectasis is defined as focal lung collapse that radiologically appears as a round mass-like lesion in the periphery of the lung. In general, human patients with rounded atelectasis have a history of pleural effusion and abnormal pleura and characteristic CT findings help to distinguish rounded atelectasis from pulmonary neoplasia without the need for invasive surgical biopsy. This retrospective multi-center case series describes rounded atelectasis in four cats and one dog. Chylothorax was seen in four patients and an eosinophilic and lymphoplasmacytic effusion was seen in one patient. All patients had solitary or multifocal subpleural pulmonary masses (26 masses total in 5 patients) with diffuse, multifocal, or focal visceral and parietal pleural thickening. All the masses but one were broad-based towards the visceral pleura. Masses were most common in the ventral or lateral aspect of the lungs. Indistinctness at the hilar aspect of the lesion was seen in all masses; a "comet tail" sign was seen in 14 of 26 masses. On postcontrast images, the lesions were homogeneously enhanced in 24 of 26 masses and heterogeneous in two of 26 masses. Other findings include ground glass opacities (n = 5), parenchymal bands (n = 4), mild to moderate lymphadenopathy (n = 4), and compensatory hyperinflation of the lung lobes not affected by atelectasis (n = 2). Histopathology of four cases revealed atelectasis with fixed pleural folds, chronic pleuritis, and mild to moderate pleural fibrosis. Awareness of rounded atelectasis in veterinary species will enable inclusion of a benign etiology into the differential diagnosis for subpleural masses in cases with pleural abnormalities.

Prevalence of lung atelectasis in sedated dogs examined with computed tomography.

BACKGROUND: Computed tomography (CT) scanning of the lung is known to be a valuable tool when investigating lung pathology of the dog. During CT-scan the dog needs to be immobilized and general anesthesia has historically been considered as gold standard although being a more expensive and time-consuming alternative to sedation. Today, modern high speed multidetector CT-scanners offer new possibilities for sedation as an alternative. Both anesthesia and sedation can cause lung atelectasis, and this can be problematic when reading the CT-images since it potentially can masque or mimic lung pathology leading to misdiagnosis. The objective of this prospective analytic study was to investigate the prevalence of lung atelectasis and changes in lung attenuation over time in dogs that receive intravenous sedation and positioned in sternal recumbency. RESULTS: 20 dogs without known lung pathology underwent three consecutive CT-scans of the lung; the first scan was initiated as soon as the dog was sufficiently sedated, the second scan approximately 5 min after the first one and the last scan after the dog's orthopaedic scan was completed. The dogs received intravenous sedation in a combination of dexmedetomidine and butorphanol and were kept positioned in a strict sternal recumbency during sedation and exam. Each lung lobe was individually examined in an axial plane and measurements of dorsal, ventral, and mean lung attenuation were made. Atelectasis or areas with poorly aerated lung tissue were not detected as all parts of the lobes were normally aerated at all three scans. A statistically significant increase in lung attenuation between the first and the second scan (P = 0.03) and between the first and the third scan (P = 0.0004) was seen in the ventral part of the lobes. CONCLUSIONS: This study indicates that CT-examination of the lungs can be performed on sedated dogs that are kept in a sternal recumbency without development of atelectasis. It also suggests that there is an early correlation between time and increase in lung attenuation.

Comparison of the efficacy of two alveolar recruitment manoeuvres in improving the lung mechanics and the degree of atelectasis in anaesthetized healthy sheep.

The aim of the present study was to evaluate whether the application of two types of alveolar recruitment manoeuvres (ARMs) followed by a positive end-expiratory pressure (PEEP) improved lung mechanics and the degree of atelectasis caused by general anaesthesia. Twenty-one female Merino sheep were divided into three groups: sustained inflation ARM (ARMsust), stepwise ARM (AMRstep), and control (without ARM). Sheep received detomidine-morphine for premedication, propofol for induction, and isoflurane during general anaesthesia in a volume-controlled mode with 100% oxygen during the first 15 min of anaesthesia and 40% the rest of the study. The right jugular vein and metacarpal artery were catheterised for mixed venous and arterial blood sample collection, respectively. The quasistatic compliance (Cqst), oxygenation parameters, and shunt fraction (Qs/Qt) were monitored before ARM application (TpreARM), and at 10 (T10) and 60 min (T60) after ARM application. A pulmonary histopathological study was conducted on five animals from each group. A significant increase in Cqst was observed in both ARM groups at T10 compared to TpreARM (ARMsust: P = 0.001; ARMstep: P = 0.002), although only the ARMsust group showed significant differences compared to the control group. The ARMstep group presented a significant improvement in oxygenation parameters and Qs/Qt fraction (T10: 4.84 (3.26-16.48)%, P = 0.048; T60: 4.40 (4.31-14.16)%, P = 0.004) compared with TpreARM (21.48 (20.61-28.32)%). The ARMstep group had the highest percentage of alveolar area and the most homogeneous values. In conclusion, the application of a stepwise ARM followed by PEEP improved atelectasis caused by isoflurane anaesthesia in healthy sheep.

Minimal atelectasis and poorly aerated lung on thoracic CT images of normal dogs acquired under sedation.

General anesthesia optimizes image quality of thoracic CT in dogs by providing patient immobilization and respiratory control. However, it also comes with disadvantages that may serve as a detractor to the use of CT in veterinary practice. With the use of multidetector helical CT combined with injectable sedation for restraint, parameters such as atelectasis and poorly aerated lung should not be appreciably different from what has been observed in dogs under general anesthesia. This prospective pilot study aimed to evaluate the mean lung attenuation and the amount of atelectasis and poorly aerated lung on thoracic CT images acquired under injectable sedation in normal dogs. The entire thorax of 10 client-owned dogs was scanned. Attenuation measurements were generated by three-dimensional reconstruction software. Mean ± SD lung attenuation was -707.0 ± 60.0. Atelectasis was not identified on any of the scans. Hypoinflated lung, the percentage of lung parenchyma with attenuation greater than -500 and -250 Hounsfield units (HU), was 10.7 ± 4.7% and 2.4 ± 1.2% (mean ± SD), respectively. There was no significant change in these percentages over time. Compared to previously published data, thoracic CT images obtained under sedation had mean attenuation comparable to normal expiratory lung and a lower percentage of poorly aerated lung compared to that of anesthetized dogs. Using sedation to complete canine thoracic CT does not itself lead to alterations of lung attenuation and may confer less hypoinflation and atelectasis than general anesthesia.

First isolation of Klebsiella variicola from a horse pleural effusion.

BACKGROUND: Respiratory diseases are the second most common cause of illnesses in horses, their etiology can be viral, bacterial, immune-mediated, or mechanical (Racklyeft and Love DN, Aust Vet J 78:549-59, 2000; Austin et al., J Am Vet Med Assoc 207:325-328, 1995; Arroyo et al., J Vet Intern Med 31:894-900, 2017). Klebsiella variicola is a Gram-negative bacterium that was initially identified as an endophyte in soil and plants such as bananas, rice, sugar cane and maize but recent studies have identified this microorganism as an emerging pathogen in humans (Rodríguez-Medina et al., Emerg Microbes Infect 8:973-988, 2019; Fontana et al., J Clin Microbiol 57:e00825-18, 2019; Rosenblueth et al., Syst Appl Microbiol 27:27-35, 2004). This paper describes, for the first time to our knowledge, the isolation of K. variicola from pleural effusion in a male adult horse. CASE PRESENTATION: 17-years Italian Saddle Horse with respiratory distress and fever was admitted to the Veterinary Teaching Hospital of the Department of Veterinary Medical Sciences, University of Bologna. At home, the patient had undergone antibiotic therapy without clinical improvement. Vital signs on admission revealed an increased respiratory rate, tachycardia, pyrexia and weight loss. The animal was submitted for collateral examination including thoracic radiology and ultrasound and thoracoscopy that showed bilateral pleural effusion associated with multifocal pulmonary atelectasis. During the thoracoscopic examination, that confirmed the presence of a seropurulent pleural effusion, a sample of pleural fluid was collected and Gram-negative bacteria were isolated and subjected to matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) that allowed the identification of K. variicola. The isolate was sensitive to amikacin, cefazolin, enrofloxacin, marbofloxacin, tetracycline, and trimethoprim-sulfamethoxazole;the horse was treated with Oxytetracycline and amikacin. Despite a general health improvement of the subject, the pleural effusion did not resolve after treatment. CONCLUSIONS: This paper describes, for the first time, the isolation of K. variicola in a horse with respiratory disease. The misidentification between K. variicola and K. pneumoniae has caused unawareness about significant aspects of this bacterial species. In fact, even though in animals the role of this bacterium is not clear, in humans it has been recognized as an emerging pathogen. The use of new methods for bacterial identification will probably lead to the isolation of a greater number of strains which will have to be studied to acquire knowledge that will be useful to clarify the clinical importance and relevance of K. variicola also in animals.

Infection of calves with in-vivo passaged bovine parainfluenza-3 virus, alone or in combination with bovine respiratory syncytial virus and bovine coronavirus.

Bovine respiratory disease complex is etiologically complex and usually involves co-infection by several agents, including bovine parainfluenza virus-3 (BPIV-3), bovine respiratory syncytial virus (BRSV), and bovine coronavirus (BCoV). Traditionally, vaccines have been tested in seronegative calves infected with a single in vitro-passaged agent, often with little disease, resulting in unvaccinated subjects. To overcome the potential problem of attenuation coincident with in vitro culture of the viruses, cocktails of field isolates of BPIV-3s and BCoVs were passaged in the lungs of neonatal colostrum-deprived calves. Lung lavage fluids were used as inocula, alone and in combination with in-vivo passaged BRSV, and aerosolized into a trailer containing conventionally reared 9-week-old weaned Holstein calves with decayed, but still measurable, maternal antibodies. Calves developed acute respiratory disease of variable severity. Upon necropsy, there were characteristic gross and histologic lesions in the respiratory tract, associated immunohistochemically with BPIV-3, BRSV, and BCoV. In-vivo passage of viruses is an alternative to in vitro culture to produce inocula to better study the pathogenesis of infection and more rigorously and relevantly assess vaccine efficacy.

Le complexe des maladies respiratoires bovines possède une étiologie complexe et implique habituellement une co-infection par plusieurs agents, incluant le virus parainfluenza bovin 3 (BPIV-3), le virus respiratoire syncitial bovin (BRSV) et le coronavirus bovin (BCoV). Traditionnellement, les vaccins ont été testés chez des veaux séronégatifs infectés avec un seul agent cultivé in vitro, présentant souvent peu de maladie, résultant en des sujets non-vaccinés. Afin de contrecarrer le problème potentiel d'atténuation associé à la culture in vitro des virus, des cocktails d'isolats de champs de BPIV-3 et de BCoV furent passés dans des poumons de veaux nouveau-nés privés de colostrum. Les liquides de lavage pulmonaire furent utilisés comme inoculum, seul et en combinaison avec des BRSV passés in vivo, et aérosolisés dans une remorque contenant des veaux Holstein sevrés élevés de manière conventionnelle âgés de 9 semaines ayant des anticorps maternels en déclin mais toujours mesurables. Les veaux ont développé une maladie respiratoire aiguë de sévérité variable. Lors de la nécropsie, il y avait des lésions macroscopiques et histologiques caractéristiques dans le tractus respiratoire, associées immuno-histochimiquement avec BPIV-3, BRSV et BCoV. Le passage in vivo de virus est une alternative à la culture in vitro afin de produire un inoculum permettant de mieux étudier la pathogénie de l'infection et d'évaluer plus rigoureusement et plus pertinemment l'efficacité de vaccins.(Traduit par Docteur Serge Messier).

Arterial blood gas analysis in dogs with bronchomalacia.

Canine bronchomalacia (CBM) is a structural airway disease leading to chronic cough and intermittent respiratory distress, primarily affecting elderly dogs of small breeds. Results of blood gas analysis have been reported in dogs with several diseases, but not yet in those with CBM. Eleven dogs with CBM were recruited in this study. Most dogs presented with mild hypoxemia and normocapnia, and all with increased alveolar-arterial difference for O2 (A-aDO2). In computed tomography, abnormal lung patterns, such as atelectasis and parenchymal band, were detected in all dogs, consistent with the regions affected by CBM. We conclude that CBM causes abnormal lung patterns and results in impaired oxygenation. Blood gas analysis is a useful tool for detecting mild pulmonary lesions and concurrent CBM.

Effect of body position and time on quantitative computed tomographic measurements of lung volume and attenuation in healthy anesthetized cats.

OBJECTIVE To quantify the effect of time and recumbency on CT measurements of lung volume and attenuation in healthy cats under general anesthesia. ANIMALS 8 healthy research cats. PROCEDURES Anesthetized cats were positioned in sternal recumbency for 20 minutes and then in left, right, and left lateral recumbency (40 minutes/position). Expiratory helical CT scan of the thorax was performed at 0 and 20 minutes in sternal recumbency and at 0, 5, 10, 20, 30, and 40 minutes in each lateral recumbent position. For each lung, CT measurements of lung volume and attenuation and the extent of lung areas that were hyperaerated (-1,000 to -901 Hounsfield units [HU]), normoaerated (-900 to -501 HU), poorly aerated (-500 to -101 HU), or nonaerated (-100 to +100 HU [indicative of atelectasis]) were determined with a semiautomatic threshold-based technique. A restricted maximum likelihood analysis was performed. RESULTS In lateral recumbency, the dependent lung had significantly greater attenuation and a lower volume than the nondependent lung. Within the dependent lung, there was a significantly higher percentage of poorly aerated lung tissue, compared with that in the nondependent lung. These changes were detected immediately after positioning the cats in lateral recumbency and remained static with no further significant time-related change. CONCLUSIONS AND CLINICAL RELEVANCE Results indicated that once anesthetized healthy cats were positioned in lateral recumbency, the dependent lung lobes underwent a rapid reduction in lung volume and increase in lung attenuation that did not progress over time, predominantly attributable to an increase in poorly aerated lung tissue.

Profiling of miRNAs in neonatal cloned bovines with collapsed lungs and respiratory distress.

Neonatal respiratory distress is a major mortality factor in cloned animals; however, the pathogenesis of this disease has rarely been investigated. Previous studies have shown that miRNAs regulate critical genes related to lung development, cell differentiation, surfactant synthesis, secretion and lung disease. This study aimed to examine differentially expressed miRNAs in collapsed lungs of cloned bovine neonates and normal lungs in order to identify key pathways and functions that might be related to the pathogenesis of neonatal respiratory distress. In this study, miRNA transcriptomes of collapsed lungs of neonatal cloned bovines and normal lungs were analysed by next-generation sequencing and the results were validated using quantitative real-time PCR (qRT-PCR). A total of 177 differentially expressed miRNAs were identified in the two groups (fold change > 2, RPM ≥ 5), some of which were associated with type II cell differentiation, for example, mmu-miR-29a-5p_L-2R+1, hsa-miR-200c-5p_L-1R+1 and mmu-miR-18a-3p_R+1. The differentially expressed miRNAs were predicted to 6,031 target genes. By Gene Ontology (GO) and Kyoto Encyclopeida of Genes and Genomes (KEGG) DATA base, 133 significant GO terms (p < .05) and 13 significant KEGG pathways (p < .05) were obtained. Many of them were associated with lung development and surfactant homoeostasis, such as lipid biosynthetic processes, protein transport, endocytosis, lysosome, endosome, Golgi apparatus and membrane. Our results of miRNAs express profiles may partially explain the respiratory distress and lung collapse in neonatal bovine clones and could provide novel insights into roles of miRNAs in regulation of lung collapse and neonatal respiratory distress in cloned farm animals.

Does the computed tomographic appearance of the lung differ between young and old dogs?

In computed tomographic (CT) images of humans, decreased lung attenuation, bronchial dilation, and/or thickening, air trapping, cysts, and thickened interlobular septa have been associated with increasing age. To determine if there are differences in the CT appearance of the lungs of young and old dogs that could affect interpretation of diagnostic studies, pulmonary CT images of dogs with conditions unrelated to the thorax were reviewed retrospectively in a case-control study. Computed tomography studies of 42 young dogs (range 0.3-4.8 years) and 47 old dogs (range 9-15.1 years) were jumbled and reviewed by an observer blinded to dog age. Computed tomography was performed under sedation in 62 (70%) dogs and under general anesthesia in 27 (30%). Heterotopic bone was more prevalent (62% vs. 14%) in old dogs. Lung collapse was significantly associated with old age, greater body weight, and anesthesia. There were no significant differences in median lung attenuation or occurrence of ground glass pattern, cysts, bronchial thickening, bronchial dilation, or degree of tracheal calcification. No examples of reticular pattern, emphysema, pleural thickening, or septal thickening were observed in any dog. Despite previous studies describing age-related changes in the radiographic appearance of the lungs of old dogs, it appears that there are minimal observable differences in CT images. Old dogs are more likely to have visible foci of heterotopic bone and may be more prone to lung lobe collapse than young dogs, but neither of these differences should contribute to misdiagnosis of pulmonary disease.

Effect of fixed value positive end expiratory pressure valves on canine thoracic volume and atelectasis.

OBJECTIVES: The objective of this study was to investigate whether a fixed 10 cm H2 O positive end-expiratory pressure valve would increase the aeration of, and reduce atelectasis formation in, the lungs after induction of anaesthesia in dogs undergoing thoracic CT. MATERIALS AND METHODS: 28 dogs were paired based on breed, bodyweight and body condition score and then randomly allocated to either Group Z (0 cm H2 O) or Group P (10 cm H2 O positive end-expiratory pressure valve) immediately after the induction of anaesthesia. All patients received a standardised anaesthetic protocol, and their lungs were manually hyperventilated before image acquisition. Cardiorespiratory parameters were recorded every 5 minutes. Total lung volume, lung density and degree of atelectasis were determined for each dog from the acquired images. RESULTS: The 10 cm H2 O positive end-expiratory pressure valve significantly increased lung volume (mL/kg) (Group Z: 52 ±14; Group P: 83 ±17; P<0·001) whilst significantly reducing lung density (Hounsfield units) (Group Z: -775 ±30; Group P: -856 ±22; P<0·001) and the amount of atelectasis (P=0·004). Dogs in Group P had significantly higher end-tidal carbon dioxide (P<0·05), but there was no difference between the groups for respiratory rate or any cardiovascular variable. CLINICAL SIGNIFICANCE: A fixed-value positive end-expiratory pressure valve provides a simple, cost-effective technique for improving expiratory thoracic CT studies by increasing lung volume and decreasing atelectasis formation.

Effect of position and time held in that position on ground-glass opacity in computed tomography images of dogs.

OBJECTIVE To evaluate effects of position, time in that position, and positive end-expiratory pressure on ground-glass opacity caused by physiologic atelectasis on lung CT images and to determine effects of recumbency position before CT. ANIMALS 6 healthy Beagles. PROCEDURES In a crossover study, dogs were placed in 4 positions (sternal, dorsal, right lateral, and left lateral recumbency) for 2 holding times (30 and 60 minutes). Dogs were then repositioned in sternal recumbency, and CT was performed at 2 positive end-expiratory pressures (0 and 15 mm Hg). Location, distribution, and degree of ground-glass opacities were evaluated on lung CT images. Volume and mean density of the lungs and ground-glass opacities as well as maximum density of ground-glass opacities were evaluated. RESULTS Ground-glass opacities were mainly observed in parts of the lungs that were dependent during the various positions before CT, except for sternal recumbency. Opacities were reversible and decreased or disappeared after lung inflation. Ground-glass opacities were observed most frequently and had greatest severity when dogs were positioned in left lateral recumbency before CT. Ground-glass opacities were negligible for dogs positioned in sternal recumbency before CT. CONCLUSIONS AND CLINICAL RELEVANCE Location and reversibility of ground-glass opacities may help clinicians distinguish whether they are attributable to atelectasis or a result of pathological changes. Dogs should be positioned in sternal recumbency to minimize the occurrence of ground-glass opacities, particularly when several procedures are performed before CT, which increases the time that a dog will remain in the same position.

Effects of positive end-expiratory pressure and 30% inspired oxygen on pulmonary mechanics and atelectasis in cats undergoing non-bronchoscopic bronchoalveolar lavage.

Objectives The objective of this study was to determine if modification of inspired oxygen concentration or positive end-expiratory pressure (PEEP) would alter bronchoalveolar lavage (BAL)-induced changes in pulmonary mechanics or atelectasis, as measured using ventilator-acquired pulmonary mechanics and thoracic CT. Methods Six experimentally asthmatic cats underwent anesthesia and non-bronchoscopic BAL, each under four randomized treatment conditions: 100% oxygen, zero PEEP; 30% oxygen, zero PEEP; 100% oxygen, PEEP 2 cmH2O; and 30% oxygen, PEEP 2 cmH2O. Pulse oximetry was used to estimate oxygen saturation (SpO2). Ventilator-acquired pulmonary mechanics and thoracic CT scans were collected prior to BAL and at 1, 5 and 15 mins post-BAL. Results While receiving 100% oxygen, no cat had SpO2 <91%. Some cats receiving 30% oxygen had decreased saturation immediately post-BAL (mean ± SD 70.8 ± 31%), but 6/8 of these had SpO2 >90% by 1 min later. There was a significant increase in airway resistance and a decrease in lung compliance following BAL, but there was no significant difference between treatment groups. Cats receiving no PEEP and 30% oxygen conserved better aeration of the lung parenchyma in BAL-sampled areas than those receiving no PEEP and 100% oxygen. Conclusions and relevance Alterations in pulmonary mechanics or atelectasis may not be reflected by SpO2 following BAL. The use of 30% inspired oxygen concentration failed to show any significant improvement in pulmonary mechanics but did diminish atelectasis. In some cats, it was also associated with desaturation of hemoglobin. The use of PEEP in this study did not show any effect on our outcome parameters. Further studies using higher PEEP (5-10 cmH2O) and intermediate inspired oxygen concentration (40-60%) are warranted to determine if they would confer clinical benefit in cats undergoing diagnostic BAL.

Regional distribution of ventilation in horses in dorsal recumbency during spontaneous and mechanical ventilation assessed by electrical impedance tomography: a case series.

OBJECTIVE: To evaluate the regional distribution of ventilation in horses during spontaneous breathing and controlled mechanical ventilation (CMV) using electrical impedance tomography (EIT). STUDY DESIGN: Prospective, experimental case series. ANIMALS: Four anaesthetized experimental horses. METHODS: Horses were anaesthetized with isoflurane in an oxygen-air mixture and medetomidine continuous rate infusion, placed in dorsal recumbency with an EIT belt around the thorax, and allowed to breathe spontaneously until PaCO2 reached 13.3 kPa (100 mmHg), when volume CMV was started. For each horse, the EIT signal was recorded for at least 2 minutes immediately before (T1), and at 30 (n = 3) or 60 (n = 1) minutes after the start of CMV (T2). The centre of ventilation (CoV), dependent silent spaces (DSS) (likely to represent atelectatic lung areas), non-dependent silent spaces (NSS) (likely to represent lung areas with low ventilation) and total ventilated area (TVA) were evaluated. Cardiac output (CO) was measured and venous admixture and oxygen delivery (DO2) were calculated at T1 and T2. Data are presented as median and range. RESULTS: After the initiation of CMV, the CoV moved ventrally towards the non-dependent lung by 10% [from 57.4% (49.6-60.2%) to 48.3% (41.9-54.4%)]. DSS increased [from 4.1% (0.2-13.9%) to 18.7% (7.5-27.5%)], while NSS [21.7% (9.4-29.2%) to 9.9% (1.0-20.7%)] and TVA [920 (699-1051) to 837 (662-961) pixels] decreased. CO, venous admixture and DO2 also decreased. CONCLUSIONS AND CLINICAL RELEVANCE: In spontaneously breathing anaesthetized horses in dorsal recumbency, ventilation was essentially centred within the dependent dorsal lung regions and moved towards non-dependent ventral regions as soon as CMV was started. This shows a major lack of ventilation in the dependent lung, which may be indicative of atelectasis.

Use of manual alveolar recruitment maneuvers to eliminate atelectasis artifacts identified during thoracic computed tomography of healthy neonatal foals.

OBJECTIVE To evaluate use of single manual alveolar recruitment maneuvers (ARMs) to eliminate atelectasis during CT of anesthetized foals. ANIMALS 6 neonatal Standardbred foals. PROCEDURES Thoracic CT was performed on spontaneously breathing anesthetized foals positioned in sternal (n = 3) or dorsal (3) recumbency when foals were 24 to 36 hours old (time 1), 4 days old (time 2), 7 days old (time 3), and 10 days old (time 4). The CT images were collected without ARMs (all times) and during ARMs with an internal airway pressure of 10, 20, and 30 cm H2O (times 2 and 3). Quantitative analysis of CT images measured whole lung and regional changes in attenuation or volume with ARMs. RESULTS Increased attenuation and an alveolar pattern were most prominent in the dependent portion of the lungs. Subjectively, ARMs did not eliminate atelectasis; however, they did incrementally reduce attenuation, particularly in the nondependent portion of the lungs. Quantitative differences in lung attenuation attributable to position of foal were not identified. Lung attenuation decreased significantly (times 2 and 3) and lung volume increased significantly (times 2 and 3) after ARMs. Changes in attenuation and volume were most pronounced in the nondependent portion of the lungs and at ARMs of 20 and 30 cm H2O. CONCLUSIONS AND CLINICAL RELEVANCE Manual ARMs did not eliminate atelectasis but reduced attenuation in nondependent portions of the lungs. Positioning of foals in dorsal recumbency for CT may be appropriate when pathological changes in the ventral portion of the lungs are suspected.

Computed tomographic findings of pulmonary atelectasis in healthy anesthetized Beagles.

OBJECTIVE To characterize the extent and location of atelectasis in healthy anesthetized dogs positioned in lateral recumbency and to determine whether repositioning dogs in sternal recumbency would resolve atelectasis. ANIMALS 6 healthy adult Beagles. PROCEDURES Each dog was anesthetized and underwent a CT examination twice with a 2-week interval between examinations. Once anesthetized, each dog was positioned in sternal recumbency, and a breath-hold helical transverse thoracic CT scan was acquired. The dog was then positioned in lateral recumbency for 30 minutes, and images were obtained at 5 preselected sites at 3, 8, 13, 20, and 30 minutes after repositioning (phase 1). Then, the dog was repositioned in sternal recumbency, and CT images were obtained at the 5 preselected sites at 5, 10, and 20 minutes after repositioning (phase 2). The protocol for the second examination was the same as the first except the dog was positioned in the opposite lateral recumbency during phase 1. The attenuation and cross-sectional area of the lung lobes at the preselected sites were measured and compared over time. RESULTS Lateral recumbency did not cause atelectasis in any of the dogs. Patchy areas of abnormally increased attenuation were infrequently detected in the left cranial lung lobe when dogs were positioned in left lateral recumbency, and those areas failed to resolve when dogs were positioned in sternal recumbency. CONCLUSIONS AND CLINICAL RELEVANCE Results indicated that the extent of lung attenuation changes was minimal in healthy anesthetized Beagles positioned in lateral recumbency and should not preclude CT examination.

WHICH AIRWAY PRESSURE SHOULD BE APPLIED DURING BREATH-HOLD IN DOGS UNDERGOING THORACIC COMPUTED TOMOGRAPHY?

This randomized controlled trial study aimed to identify the optimal positive pressure (PP) level that can clear atelectasis while avoiding pulmonary hyperinflation during the breath-hold technique in dogs undergoing thoracic computed tomography (CT). Sixty dogs affected by mammary tumors undergoing thoracic CT for the screening of pulmonary metastases were randomly assigned to six groups with different levels of PP during the breath-hold technique: 0 (control), 5 (PP5), 8 (PP8), 10 (PP10), 12 (PP12), and 15 (PP15) cmH2 O. The percentage of atelectatic lung region was lower in the PP10 (3.7 ± 1.1%; P = 0.002), PP12 (3.4 ± 1.3%; P = 0.0001), and PP15 (2.8 ± 0.9%; P = 0.006) groups than in the control group (5.0 ± 2.3%), and the percentage of poorly aerated lung region was lower in the PP8 (15.1 ± 2.6%; P = 0.0009), PP10 (13.0 ± 2.0 %; P = 0.002), PP12 (13.0 ± 2.2 %; P = 0.0002), and PP15 (11.1 ± 1.9%; P = 0.0002) groups than in the control group (19.8 ± 5.0). The percentage of normally aerated lung region, however, was higher in the PP10 (79.7 ± 4.1%; P = 0.005), PP12 (79.8 ± 5.1%; P = 0.0002), and PP15 (80.2 ± 4.9%; P = 0.002) groups than in the control group (73.4 ± 6.6%). A PP of 10-12 cmH2 O during the breath-hold technique should be considered to improve lung aeration during a breath-hold technique in dogs undergoing thoracic CT.