Cardiopulmonary effects of positive end-expiratory pressure during one-lung ventilation in anesthetized dogs with a closed thoracic cavity

OBJECTIVE: To evaluate the effects on oxygen delivery (DO2) of 2.5 and 5 cm H2O of positive end-expiratory pressure (PEEP) applied to the dependent lung during one-lung ventilation (OLV) in anesthetized dogs with a closed thoracic cavity. ANIMALS: 7 clinically normal adult Walker Hound dogs. PROCEDURE: Dogs were anesthetized, and catheters were inserted in a dorsal pedal artery and the pulmonary artery. Dogs were positioned in right lateral recumbency, and data were collected during OLV (baseline), after application of 2.5 cm H2O of PEEP for 15 minutes during OLV, and after application of 5 cm H2O of PEEP for 15 minutes during OLV. Hemodynamic and respiratory variables were analyzed and calculations performed to obtain DO2, and values were compared among the various time points by use of an ANOVA for repeated measures. RESULTS: PEEP induced a significant decrease in shunt fraction that resulted in a significant increase in arterial oxygen saturation. However, it failed to significantly affect arterial oxygen content (CaO2) or cardiac output. Thus, DO2 was not affected in healthy normoxemic dogs as a net result of the application of PEEP. CONCLUSIONS AND CLINICAL RELEVANCE: The use of PEEP during OLV in anesthetized dogs with a closed thoracic cavity did not affect DO2. Use of PEEP during OLV in dogs with a closed thoracic cavity is recommended because it does not affect cardiac output and any gain in CaO2 will be beneficial for DO2 in critically ill patients.     

Thoracoscopic Subphrenic Pericardectomy Using Double‐Lumen Endobronchial Intubation for Alternating One‐Lung Ventilation

Objective— To report the technique, complications, and effectiveness of thoracoscopic subphrenic pericardectomy (SPP) using double‐lumen endobronchial intubation for alternating 1‐lung (OLV) in healthy dogs. Study Design— Prospective cohort study. Animals— Mature purpose‐bred dogs (n=7). Methods— Bronchoscope‐assisted placement of a left‐sided double‐lumen endobronchial tube, immediately before surgery, allowed intraoperative alternation of ventilation between lung fields. A camera portal was established in a subxyphoid location. Two instrument portals were established at the 4th–6th intercostal spaces on the right and left sides. A vessel‐sealing device was used to create the subphrenic pericardectomy. After termination of the procedure, dogs were humanely euthanatized under anesthesia and necropsy performed. In each dog, the extent of pericardectomy and any complications were evaluated. Results— Technical difficulties with tube placement occurred in 4 dogs, but alternating OLV was achieved in all dogs and SPP completed successfully. Median surgical time was 87.5 minutes (range, 80–105 minutes). At necropsy, 0.5–2 cm of pericardial tissue remained ventral to the intact phrenic nerve in 6 dogs; in 1 dog, the phrenic nerve was transected on the left side only. Conclusions— Thoracoscopic subphrenic pericardectomy is a technically feasible procedure in healthy dogs. Double‐lumen endobronchial intubation allowed alternating OLV without intraoperative bronchoscopically guided tube manipulation in all but 1 dog. Clinical Relevance— Thoracoscopic subphrenic pericardectomy could potentially be used for management of conditions where relief of pericardial constriction or access to intrapericardial structures is desired.     

Thoracoscopic-assisted lung lobectomy in the dog: report of two cases

The benefits and application of thoracoscopy with selective ventilation, as an adjunct to thoracotomy, in facilitating pleural exploration and lung lobectomy in two dogs are presented. Similar thoracoscopic-assisted procedures are commonly used in human patients because there is better exposure and they are technically less demanding than thoracoscopy alone, while causing less postoperative morbidity than conventional thoracotomy. There are no previous reports of thoracoscopic-assisted surgery in the veterinary literature. In the cases described, thoracoscopic-assisted mini-thoracotomy was an effective, minimally-invasive approach for ipsilateral hemithorax exploration and lung lobectomy.     

Endoscopic removal of a bronchial carcinoma in a dog using one-lung ventilation

Objective— To describe anesthetic management of endoscopic electrosurgical removal of a bronchial carcinoma, partially blocking the right main stem bronchus in a Cocker Spaniel.
Study Design— Clinical case report.
Animals— Dog with a bronchial carcinoma.
Methods— To allow sufficient space for the endoscope and to avoid an oxygen-rich gas mixture in the trachea, which carries the risk of an airway fire when electrocautery is used, a 1 lumen endobronchial tube (EBT) was inserted into the left main stem bronchus. One-lung ventilation (OLV) started with a volume-controlled ventilator was switched to pressure-controlled ventilation in combination with positive end-expiratory pressure (PEEP).
Results— Resection of the bronchial carcinoma was successful. The dog was hypercapnic throughout the procedure and a high alveolar-arterial oxygen gradient was measured.
Conclusion— An EBT may be a feasible and safe option to provide OLV for bronchoscopic electrocautery with a closed thoracic cavity in dogs.
Clinical Relevance— EBT intubation for OLV should be considered as part of the anesthetic management of airway diseases treated with bronchoscopic electrocautery.     

Spontaneous midlobar lung lobe torsion in a 2-year-old Newfoundland

A 2-year-old, intact male Newfoundland was presented for evaluation of a 1- to 2-day history of coughing, retching, and progressive lethargy. Thoracic radiographs demonstrated right-sided pleural effusion and lobar vesicular emphysema. An exploratory thoracotomy revealed midlobar torsion of the right caudal lung lobe. A partial lung lobectomy was performed, and following surgery, the dog recovered without complications. Lung lobe torsions in dogs typically occur at the hilus of the affected lung lobe. This report documents that midlobar lung lobe torsions occur in dogs and should be considered as a differential diagnosis in cases of lobar vesicular emphysema and pleural effusion.     

Bronchial cartilage dysplasia with multifocal lobar bullous emphysema and lung torsions in a pup.

Bronchial cartilage dysplasia is believed to have caused lobar bullous emphysema in a 5-month-old Chow Chow that had exercise intolerance, progressive dyspnea, and episodic cough. Radiography of the thorax revealed hyperlucency of the left hemithorax, displacement of the mediastinum and heart to the right, and flattening of the diaphragm. The pup died shortly after the radiographs were obtained. Necropsy revealed massive hyperinflation with 180 degrees torsion of the cranial portion of the left cranial lung lobe, and hyperinflation with less than 180 degrees torsion of the right accessory lung lobe. Histologic examination of the affected lung lobes revealed a lack of bronchial cartilage, loss and displacement of alveolar walls, and bulla formation that resembled congenital (infantile) lobar emphysema of human beings. In this pup, lung lobe torsions may have been predisposed by bronchial cartilage dysplasia.     

Thoracoscopic foreign body removal and right middle lung lobectomy to treat pyothorax in a dog

A three-year-old, 30-kg, spayed female German wirehaired pointer was presented for coughing, pyrexia and lethargy. Thoracic radiographs showed mild right-sided pleural effusion, moderate pneumothorax and a pulmonary lesion in the right middle or caudal lung lobe. A diagnosis of pyothorax was established by fine needle aspiration of the pleural effusion. Thoracoscopic exploration was performed using one-lung ventilation. A vegetal foreign body (grass awn) and an abscess were observed in the distal part of the right middle lung lobe. The foreign body was removed and a right middle lung lobectomy was performed, both thoracoscopically. No complications were noted. The dog was discharged 48 hours after surgery, and no recurrence of the clinical signs was observed during the follow-up time period (three years and three months). Thoracoscopy is a minimally invasive alternative to thoracotomy to explore and successfully treat some non-chronic pyothoraces in dogs, including lesions affecting the right middle lung lobe.     

One-lung versus two-lung ventilation in the closed-chest anesthetized dog: a comparison of cardiopulmonary parameters

OBJECTIVE: To evaluate cardiopulmonary effects of one-lung ventilation (OLV) versus two-lung ventilation (TLV) in closed-chest anesthetized dogs. STUDY DESIGN: Controlled, randomized experiment. ANIMALS: Fourteen, 2- to 7-year-old adult dogs, weighing 23 +/- 6 kg. METHODS: The dogs were anesthetized with acepromazine, morphine, thiopental, and halothane in oxygen, ventilated, and paralyzed with vecuronium. Tidal volume was 10 mL/kg. Respiratory rate was set to maintain end-tidal CO2 (ETCO2) at 40 +/- 2 mm Hg before instrumentation then not changed. The left bronchus of 7 dogs was obstructed with a Univent bronchial blocker (Fuji Systems Corp, Tokyo, Japan). Blood gas analysis and hemodynamic measurements were taken at predetermined intervals for 1 hour in the TLV group and at baseline and following bronchial obstruction in the OLV group. RESULTS: Shunt fraction was not significantly different between groups, but in OLV shunt increased from baseline at 5 minutes. Arterial oxygen (PaO2) decreased after baseline in OLV compared with TLV. Arterial carbon dioxide (PaCO2) increased with OLV and decreased with TLV. In OLV, systemic vascular resistance was variable and decreased compared with TLV. Cardiac index increased over time in both groups but was not affected by treatment. Heart rate, mean arterial pressure, and diastolic arterial pressure increased with OLV compared with TLV but did not change over time. CONCLUSION: This study shows that OLV statistically decreases oxygen tension and transiently increases shunt fraction, but with 100% O2 it appears to be a feasible procedure with minimal cardiopulmonary side effects in healthy dogs. CLINICAL RELEVANCE: OLV is a feasible procedure in anesthetized dogs to better facilitate thoracic procedures such as bronchopleural fistula repair and thoracoscopy.     

Near-fatal misuse of medical tape around an endotracheal tube connector during inhalation anesthesia in a horse

A 7-year-old gelded Irish sports horse weighing 650 kg was anesthetized on 2 consecutive days for lavage of a septic right radio-carpal joint. On both occasions the endotracheal tube connector, which had been bound in medical tape to produce an airtight seal, functioned as a unidirectional valve during mechanical ventilation, retarding expiration, imposing positive end expiratory pressure (PEEP), and probably continuous positive airway pressure (CPAP). The equipment dysfunction was not identified on either occasion despite close inspection prompted by progressive increases in airway pressure and thoracic distension. Whilst the PEEP and CPAP exerted unexpectedly modest cardiovascular effects and the horse recovered uneventfully on both occasions, the improvisation may have proven fatal in a higher-risk subject.     

Equine thoracoscopy: normal anatomy and surgical technique

Six normal, healthy horses age 3-10 years underwent left and right thoracoscopic examination using a rigid telescope. A minimum of 30 days was allowed between procedures. Horses were restrained in stocks and sedated with a continuous detomidine infusion. After surgical preparation of the hemithorax elected for surgery, and administration of local or regional anaesthesia of the surgery sites, thoracoscopy was completed during two 15 min pneumothorax periods. During the procedures, the thoracic structures were viewed using a 57 cm, 10 mm diameter, 30 degrees rigid telescope connected to a digital camcorder to allow computer capture of digital images. The telescope was inserted into the thoracic cavity via 3 different intercostal spaces. The 8th, 10th and 12th intercostal spaces were randomly selected and used among horses. The exploration of each hemithorax started from the dorsal-caudal quadrant continued toward the cranial thorax and was completed by observing the diaphragmatic and caudal pulmonary region. Collapsed lung, aorta, oesophagus and diaphragm were viewed readily in either hemithorax. On exploration of the right hemithorax, the azygos vein, thoracic duct and pulmonary veins were also identified. Horses tolerated thoracoscopy well. Signs of discomfort, such as increased respiratory rate, coughing and decreased level of sedation, were associated with lung collapse in one horse, with pneumothorax on 2 occasions, and when the thorax was approached through the 8th intercostal space. Surgery performed via the 8th intercostal space was hindered by the rigidity of the 8th and 9th ribs, and by the presence of a greater musculature, which did not allow easy cranial and caudal movements of the telescope.     

Pleuropulmonary and cardiovascular consequences of thoracoscopy performed in healthy standing horses

Six healthy, awake, and pharmacologically restrained mature horses were studied in order to define the changes in cardiopulmonary function during and after exploratory thoracoscopy and to determine the presence of postoperative complications occurring 48 hours after thoracoscopy. In a randomised 3 x 3 latin square design with 2 replications, 18 procedures were performed: 6 right (RTH) and 6 left thoracoscopies (LTH) and 6 sham procedures (STH). Prior to each procedure a physical examination and a bronchoalveolar lavage fluid analysis were performed. During thoracoscopy and sham protocols, horses were sedated with a continual drip of detomidine HCl and data were collected at 6 time intervals: T1 (baseline), T2 (10 min detomidine administration), T3 (first 15 min pneumothorax), T4 (5 min recovery from pneumothorax), T5 (second 15 min pneumothorax), and T6 (10 min recovery from the second pneumothorax and detomidine). An endoscopic thoracic examination was conducted during the 2 pneumothorax periods. An identical protocol was followed for sham procedures without surgery or pneumothorax. Data were analysed by ANOVA with time and surgical procedure as main factors. Physical examinations, thoracic radiography and ultrasound, CBC and bronchoalveolar lavage fluid analysis were performed 48 h after thoracoscopy. Heart rate, respiratory rate, and cardiac output decreased following detomidine administration. There was a trend for cardiac output to be lower during thoracoscopy. Mild systemic hypertension was associated with thoracoscopy although there was no effect on pulmonary arterial pressure. Total and pulmonary vascular resistances were increased following detomidine administration. Thoracoscopy caused a further increase in systemic and pulmonary vascular resistances especially during the second pneumothorax. Arterial O2 tension decreased following detomidine administration and was further decreased during the second pneumothorax period. PaO2 values were lower when thoracoscopy was performed on the left rather than the right hemithorax. No significant complications were found during the 48 h follow-up evaluation. A subclinical postoperative pneumothorax occurred in 2 horses, one of which had sustained a lung laceration by the trocar. Thoracoscopy performed in healthy, awake, and pharmacologically restrained horses did not have detrimental cardiopulmonary effects and did not cause postoperative complications within the first 48 h period.     

Thoracoscopic visualization and ligation of the thoracic duct in dogs

OBJECTIVE: To develop a technique for thoracoscopic visualization and ligation of the thoracic duct in dogs. STUDY DESIGN: In vivo experimental study. ANIMALS: Five mature, healthy dogs. METHODS: Dogs were normal based on physical examination, negative occult heartworm test, normal complete blood count and biochemical profile, and normal thoracic radiographs. The dogs were anesthetized, and a ventral midline laparotomy was performed for catheterization of a mesenteric lymphatic. Lymphangiography was performed to determine thoracic duct anatomy. Thoracoscopy was performed in the caudal, right hemithorax after single lung intubation or bronchial blockade. At least two 10-mm clips were placed across the thoracic duct in each dog. Lymphangiography was repeated to assess duct ligation. If complete duct occlusion was not achieved, thoracoscopy was repeated for additional clip placement. After surgery the dogs were euthanatized, and necropsies were performed. RESULTS: Lymphangiography showed that multiple branches of the thoracic duct were present in every dog; bilateral thoracic duct branches were most common. Thoracoscopic identification and ligation of the thoracic duct was successful in all five dogs. Two dogs required a second thoracoscopic procedure to completely occlude flow of contrast through the thoracic duct. Surgery time for thoracoscopy averaged 59 plus minus 9.6 minutes. Retroperitoneal contrast accumulation after thoracic duct ligation occurred in two dogs. One dog required bilateral pulmonary ventilation. CONCLUSION: Thoracoscopy can be used to visualize the thoracic duct for ligation in normal dogs. CLINICAL RELEVANCE: Thoracoscopic ligation of the thoracic duct may be a therapeutic option for management of chylothorax in dogs.     

Accidental entrapment of an endo-bronchial blocker tip by a surgical stapler during selective ventilation for lung lobectomy in a dog

OBJECTIVE: To describe the use of an endobronchial blocker (EBB) and to perform selective ventilation during pulmonary lobe resection via thoracotomy in a dog and report its accidental stapling in the resection site. STUDY DESIGN: Clinical case report. ANIMAL: One female dog with a suspected abscess or neoplasia of the right caudal pulmonary lobe. METHODS: One-lung ventilation was performed using a wire-guided EBB to seal the contaminated parenchyma and facilitate surgical access. The affected lung parenchyma was resected and the resection site was closed with staples. RESULTS: Lobar resection was performed successfully, but the loop of the EBB guide wire was inadvertently entrapped in the staple line of the lobectomy. Staples were removed to release the wire loop, and the resulting air leak caused loss of ventilation control until the parenchyma was re-sealed. CONCLUSIONS: We recommend removing the wire guide associate with the EBB after successful lung separation to avoid accidents that could have life-threatening consequences if not recognized. CLINICAL RELEVANCE: One-lung ventilation is useful to isolate healthy parenchyma from diseased parenchyma during lobectomy. Anesthesiologists and surgeons need to be aware of the potential complications associated with use of EBB.     

Right cranial lung lobe torsion after a diaphragmatic rupture repair in a Jack Russell terrier

A seven-year-old male Jack Russell terrier was presented with a history of coughing, generalised weakness and lethargy 10 days after an abdominal coeliotomy to repair a large diaphragmatic rupture. Thoracic radiographs demonstrated a soft tissue mass in the midcaudal right thoracic cavity. Ultrasonographic studies, bronchoscopy and subsequent exploratory thoracotomy confirmed a diagnosis of a right cranial lung lobe torsion (LLT), with an anomalous caudodorsal displacement of the affected lobe. LLT should be considered as a differential diagnosis for respiratory tract disease following diaphragmatic rupture repair.     

Concurrent torsion of the right cranial and right middle lung lobes in a whippet

A four-year-old, entire male whippet was presented with a three-day history of lethargy, inappetence, occasional retching, a soft cough and intermittent episodes of haemoptysis. Clinical and laboratory findings, and thoracic radiographic and ultrasonographic studies suggested a diagnosis of lung lobe torsion. A concurrent lung lobe torsion of the right cranial and right middle lung lobes was confirmed at exploratory thoracotomy. Management included resection of both the affected lung lobes. No obvious underlying aetiology for the condition was apparent. The dog made a full recovery from the procedure and at the time of writing (11 months postoperatively) was reported to be well, exercising normally and showing no breathing abnormalities.     

The influence of ventilation mode (spontaneous ventilation, IPPV and PEEP) on cardiopulmonary parameters in sevoflurane anaesthetized dogs

The purpose of this study was to investigate the cardiopulmonary influences of sevoflurane in oxygen at two anaesthetic concentrations (1.5 and 2 MAC) during spontaneous and controlled ventilation in dogs. After premedication with fentany-droperidol (5 microg/kg and 0.25 mg/kg intramuscularly) and induction with propofol (6 mg/kg intravenously) six dogs were anaesthetized for 3 h. Three types of ventilation were compared: spontaneous ventilation (SpV), intermittent positive pressure ventilation (IPPV), and positive end expiratory pressure ventilation (PEEP, 5 cm H2O). Heart rate, haemoglobin oxygen saturation, arterial blood pressures, right atrial and pulmonary arterial pressures, pulmonary capillary wedge pressure and cardiac output were measured. End tidal CO2%, inspiratory oxygen fraction, respiration rate and tidal volume were recorded using a multi-gas analyser and a respirometer. Acid-base and blood gas analyses were performed. Cardiac index, stroke volume, stroke index, systemic and pulmonary vascular resistance, left and right ventricular stroke work index were calculated. Increasing the MAC value during sevoflurane anaesthesia with spontaneous ventilation induced a marked cardiopulmonary depression; on the other hand, heart rate increased significantly, but the increases were not clinically relevant. The influences of artificial respiration on cardiopulmonary parameters during 1.5 MAC sevoflurane anaesthesia were minimal. In contrast, PEEP ventilation during 2 MAC concentration had more pronounced negative influences, especially on right cardiac parameters. In conclusion, at 1.5 MAC, a surgical anaesthesia level, sevoflurane can be used safely in healthy dogs during spontaneous and controlled ventilation (IPPV and PEEP of 5 cm H2O).     

Unusual congenital pulmonary anomaly with presumed left lung hypoplasia in a young dog

A seven‐month‐old, entire, male miniature schnauzer dog was referred with acute vomiting, inappetence and depression primarily as a result of a gastric foreign body (pine cones). During investigations, thoracic radiographs revealed increased volume of the right lung lobes, deviated cardiomediastinal structures and elevation of the heart from the sternum. Thoracic computed tomography revealed left cranial lung lobe hypoplasia and extension of the right cranial lung parenchyma across the midline to the left hemithorax. Branches of the right pulmonary vessels and bronchi also crossed the midline and extended to the left caudal lung lobe. These findings suggested that the right and left lungs were fused. In humans this finding is consistent with horseshoe lung, which is an uncommon congenital malformation. To the authors’ knowledge, this case represents the first report of such a pulmonary anomaly in a dog.     

Intermittent positive pressure ventilation with constant positive end-expiratory pressure and alveolar recruitment manoeuvre during inhalation anaesthesia in horses undergoing surgery for colic, and its influence on the early recovery period

Objective To compare, ventilation using intermittent positive pressure ventilation (IPPV) with constant positive end‐expiratory pressure (PEEP) and alveolar recruitment manoeuvres (RM) to classical IPPV without PEEP on gas exchange during anaesthesia and early recovery. Study design Prospective randomized study. Animals Twenty‐four warm‐blood horses, weight mean 548 ± SD 49 kg undergoing surgery for colic. Methods Premedication, induction and maintenance (isoflurane in oxygen) were identical in all horses. Group C (n = 12) was ventilated using conventional IPPV, inspiratory pressure (PIP) 35–45 cmH₂O; group RM (n = 12) using similar IPPV with constant PEEP (10 cmH₂O) and intermittent RMs (three consecutive breaths PIP 60, 80 then 60 cmH₂O, held for 10–12 seconds). RMs were applied as required to maintain arterial oxygen tension (PaO₂) at >400 mmHg (53.3 kPa). Physiological parameters were recorded intraoperatively. Arterial blood gases were measured intra‐ and postoperatively. Recovery times and quality of recovery were measured or scored. Results Statistically significant findings were that horses in group RM had an overall higher PaO₂ (432 ± 101 mmHg) than those in group C (187 ± 112 mmHg) at all time points including during the early recovery period. Recovery time to standing position was significantly shorter in group RM (49.6 ± 20.7 minutes) than group C (70.7 ± 24.9). Other measured parameters did not differ significantly. The median (range) of number of RMs required to maintain PaO₂ above 400 mmHg per anaesthetic was 3 (1–8). Conclusion Ventilation using IPPV with constant PEEP and RM improved arterial oxygenation lasting into the early recovery period in conjunction with faster recovery of similar quality. However this ventilation mode was not able to open up the lung completely and to keep it open without repeated recruitment. Clinical relevance This mode of ventilation may provide a clinically practicable method of improving oxygenation in anaesthetized horses.     

Recurrent pneumothorax associated with a pulmonary emphysematous bulla in a dog: surgical correction and proposed pathogenesis

A three year old dog was affected with recurrent dyspnea for two months, due to a recurrent pneumothorax. This followed an episode of mild blunt trauma to the thorax and transient strangulation. Conservative therapy of aspiration of air by repeated thoracentesis gave only temporary relief. Thoracic radiographs indicated the presence of a bulla in the right middle lung lobe. An exploratory thoracotomy confirmed the diagnosis, and a lobectomy was successfully performed. The pathogenesis of acquired pulmonary bullae is postulated. Reasons for the predisposition of the right middle lung lobe are outlined. These are related to the anatomy of the right middle bronchus, and include its position between the right pulmonary artery and vein, its oval shape, and the absence of cartilagenous support at its origin.     

The effects of intrathoracic pressure during continuous two-lung ventilation for thoracoscopy on the cardiorespiratory parameters in sevoflurane anaesthetized dogs

The cardiopulmonary effects of different levels of carbon dioxide insufflation (3, 5 and 2 mm Hg) under two-lung ventilation were studied in six sevoflurane (1.5 minimum alveolar concentration; MAC) anaesthetized dogs during left-sided thoracoscopy. An arterial catheter, Swan-Ganz catheter and multianaesthetic gas analyser were used to monitor the cardiopulmonary parameters during the experiment. Baseline data were obtained before intrathoracic pressure elevation and the measurements were repeated at intervals after left lung collapse induced by insufflation with carbon dioxide gas. The intrapleural pressure levels used were 3, 5 and 2 mm Hg. Arterial blood pressures, cardiac index, stroke index, left and right ventricular stroke work index, arterial haemoglobin saturation, arterial oxygen tension and systemic vascular resistance decreased significantly during hemithorax insufflation, whereas heart rate, right atrial pressure, mean, systolic and diastolic pulmonary arterial pressure, pulmonary capillary wedge pressure, pulmonary vascular resistance and arterial carbon dioxide tension significantly increased during intrapleural pressure elevation. Although carbon dioxide insufflation into the left hemithorax with an intrapleural pressure of 2-5 mm Hg compromises cardiac functioning in 1.5 MAC sevoflurane anaesthetized dogs, it can be an efficacious adjunct for thoracoscopic procedures. Intrathoracic view was satisfactory with an intrapleural pressure of 2 mm Hg. Therefore, the intrathoracic pressure rise during thoracoscopy with two-lung ventilation should be kept as low as possible. Additional insufflation periods should be avoided, since a more rapid and more severe cardiopulmonary depression can occur.