Valentina De Monte

Inhomogeneity of lung parenchyma during the open lung strategy: a computed tomography scan study.

RATIONALE The open lung strategy aims at reopening (recruitment) of nonaerated lung areas in patients with acute respiratory distress syndrome, avoiding tidal alveolar hyperinflation in the limited area of normally aerated tissue (baby lung). OBJECTIVES We tested the hypothesis that recruited lung areas do not resume elastic properties of adjacent baby lung. METHODS Twenty-five anesthetized, mechanically ventilated pigs were studied. Four lung-healthy pigs served as controls and the remaining 21 were divided into three groups (n = 7 each) in which lung injury was produced by surfactant lavage, lipopolysaccharide infusion, or hydrochloride inhalation. Computed tomography scans, respiratory mechanics, and gas exchange parameters were recorded under three conditions: at baseline, during lung recruitment maneuver, and at end-expiration and end-inspiration when ventilating after an open lung protocol. MEASUREMENTS AND MAIN RESULTS During recruitment maneuver and open lung protocol, the gas volume entering the insufficiently aerated compartment was 96% (75-117%) and 48% (41-63%) (median [interquartile range]) of the functional residual capacity measured before and at zero end-expiratory pressure, respectively. Nonetheless, the volume of hyperinflated lung increased during both recruitment maneuver (by 1-28% of total lung volume; P < 0.01) and open lung protocol ventilation at end-inspiration (by 1-15% of total lung volume; P < 0.01). Regional elastance of recruited lung tissue was consistently higher than that of the baby lung regardless of the ARDS model (P < 0.01). CONCLUSIONS Alveolar recruitment is not protective against hyperinflation of the baby lung because lung parenchyma is inhomogeneous during ventilation with the open lung strategy.

Physiological effects of an open lung ventilatory strategy titrated on elastance-derived end-inspiratory transpulmonary pressure: Study in a pig model*

Rationale:In the presence of increased chest wall elastance, the airway pressure does not reflect the lung-distending (transpulmonary) pressure. Objective:To compare the physiological effects of a conventional open lung approach titrated for an end-inspiratory airway opening plateau pressure (30 cm H2O) with a transpulmonary open lung approach titrated for a elastance-derived end-inspiratory plateau transpulmonary pressure (26 cm H2O), in a pig model of acute respiratory distress syndrome (HCl inhalation) and reversible chest wall mechanical impairment (chest wall and abdomen restriction). Methods:In eight pigs, physiological parameters and computed tomography were recorded under three conditions: 1) conventional open lung approach, normal chest wall; 2) conventional open lung approach, stiff chest wall; and 3) transpulmonary open lung approach, stiff chest wall. Measurements and Main Results:As compared with the normal chest wall condition, at end-expiration non aerated lung tissue weight was increased by 116 ± 68 % during the conventional open lung approach and by 28 ± 41 % during the transpulmonary open lung approach (p < .01), whereas cardiac output was decreased by 27 ± 19 % and 22 ± 14 %, respectively (p = not significant). Conclusion:In this model, the end-inspiratory transpulmonary open lung approach minimized the impact of chest wall stiffening on alveolar recruitment without causing hemodynamic impairment.

Effects of two fractions of inspired oxygen on lung aeration and gas exchange in cats under inhalant anaesthesia

OBJECTIVE To compare the effects of two fractions of inspired oxygen (FiO(2)) (0.4 and 1) on lung aeration and gas exchange during general anaesthesia in cats. STUDY DESIGN Randomized, blinded, controlled study. ANIMALS Thirty healthy, mixed breed, client owned female cats. MATERIALS AND METHODS Cats were premedicated intramuscularly with acepromazine (0.03 mg kg(-1)) and medetomidine (0.015 mg kg(-1)). Anaesthesia was induced with propofol (5 mg kg(-1)) and, after orotracheal intubation, maintained with isoflurane carried by either 100% oxygen (G100, n=15) or an oxygen-air mixture with 40% oxygen (G40, n=15). All cats were placed in dorsal recumbency and breathed spontaneously throughout the entire procedure. Following surgery (ovariectomy), a spiral computed tomography (CT) of the thorax was performed, arterial oxygen (PaO(2)) and carbon dioxide (PaCO(2)) tensions were measured and alveolar-arterial gradient of oxygen [P(A-a)O(2) ] calculated. The CT images were analysed for lung aeration by the analysis of radiograph attenuations (Hounsfield units, HU), according to the following classification: hyperinflated area (-1000 to -900 HU), normally aerated area (-900 to -500 HU), poorly aerated area (-500 to -100 HU) and non-aerated area (-100 to +100 HU). The groups were compared using one-way anova. RESULTS Compared to G100, the normally-aerated lung area was significantly greater and the poorly-aerated and non-aerated areas were significantly smaller in G40. PaCO(2) was similar in both groups. PaO(2) and P(A-a)O(2) were significantly higher in G100. In both groups, pulmonary atelectasis developed preferentially in the caudal lung fields. CONCLUSION In cats anaesthetised with isoflurane, the administration of an FiO(2) of >0.9 significantly impaired lung aeration and gas exchange as compared to an FiO(2) of 0.4. CLINICAL RELEVANCE An FiO(2) of 0.4 may better preserve lung aeration and gas exchange in anaesthetised spontaneously breathing cats but monitoring is essential to ensure oxygenation is adequate.

Effects of positive end-expiratory pressure on anesthesia-induced atelectasis and gas exchange in anesthetized and mechanically ventilated sheep.

OBJECTIVE To evaluate the effects of 10 cm H(2)O of positive end-expiratory pressure (PEEP) on lung aeration and gas exchange in mechanically ventilated sheep during general anesthesia induced and maintained with propofol. ANIMALS 10 healthy adult Bergamasca sheep. PROCEDURES Sheep were sedated with diazepam (0.4 mg/kg, IV). Anesthesia was induced with propofol (5 mg/kg, IV) and maintained with propofol via constant rate infusion (0.4 mg/kg/min). Muscular paralysis was induced by administration of vecuronium (25 microg/kg, bolus IV) to facilitate mechanical ventilation. After intubation, sheep were positioned in right lateral recumbency and mechanically ventilated with pure oxygen and zero end-expiratory pressure (ZEEP). After 60 minutes, 10 cm H(2)O of PEEP was applied for 20 minutes. Spiral computed tomography of the thorax was performed, and data were recorded for hemodynamic and gas exchange variables and indicators of respiratory mechanics after 15 (T(15)), 30 (T(30)), and 60 (T(60)) minutes of ZEEP and after 20 minutes of PEEP (T(PEEP)). Computed tomography images were analyzed to determine the extent of atelectasis before and after PEEP application. RESULTS At T(PEEP), the volume of poorly aerated and atelectatic compartments was significantly smaller than at T(15), T(30), and T(60), which indicated that there was PEEP-induced alveolar recruitment and clearance of anesthesia-induced atelectasis. Arterial oxygenation and static respiratory system compliance were significantly improved by use of PEEP. CONCLUSIONS AND CLINICAL RELEVANCE Pulmonary atelectasis can develop in anesthetized and mechanically ventilated sheep breathing pure oxygen; application of 10 cm H(2)O of PEEP significantly improved lung aeration and gas exchange.

Use of the oxygen content-based index, Fshunt, as an indicator of pulmonary venous admixture at various inspired oxygen fractions in anesthetized sheep

OBJECTIVE To evaluate the use of the oxygen content-based index, Fshunt, as an indicator of venous admixture (Qs/Qt) at various fractions of inspired oxygen (FIO(2)s) in anesthetized sheep undergoing Flung or 2-lung ventilation. Animals-6 healthy adult female sheep. PROCEDURES Sheep were anesthetized and administered 5 different FIO(2)s (0.21, 0.40, 0.60, 0.80, and 1.00) in random order during 2-lung mechanical ventilation. Arterial and mixed venous blood samples were obtained at each FIO(2) after a 15-minute stabilization period. Vital capacity alveolar recruitment maneuvers were performed after blood collection. The previously used FIO(2) sequence was reversed for sample collection during Flung ventilation. Blood samples were analyzed for arterial, pulmonary end-capillary, and mixed venous oxygen content and partial pressure and for hemoglobin concentration. Oxygen hemoglobin saturation, Qs/Qt, Fshunt, and oxygen tension-based indices (OTIs; including PAO(2):FIO(2), alveolar-arterial difference in partial pressure of oxygen [PAO(2) - PAO(2)], [PAO(2) - Pao(2)]:FIO(2), [PAO(2) - PAO(2)]:PAO(2), and PAO(2):PAO(2)) were calculated at each FIO(2); associations were evaluated with linear regression analysis, concordance, and correlation tests. Intermethod agreement between Qs/Qt and Fshunt was tested via Bland-Altman analysis. RESULTS Strong and significant associations and substantial agreement were detected between Fshunt and Qs/Qt. Relationships between OTIs and Qs/Qt varied, but overall correlations were weak. Conclusions and Clinical Relevance-Whereas OTIs were generally poor indicators of Qs/Qt, Fshunt was a good indicator of Qs/Qt at various FIO(2)s, regardless of the magnitude of Qs/Qt, and could be potentially used as a surrogate for Qs/Qt measurements in healthy sheep.

Long-term stability, functional competence, and safety of microencapsulated specific pathogen-free neonatal porcine Sertoli cells: a potential product for cell transplant therapy

Porcine Sertoli cells (pSCs) have been employed for cell therapy in pre‐clinical studies for several chronic/immune diseases as they deliver molecules associated with trophic and anti‐inflammatory effects. To be employed for human xenografts, pSCs products need to comply with safety and stability. To fulfill such requirements, we employed a microencapsulation technology to increase pre‐transplant storage stability of specific pathogen‐free pSCs (SPF‐pSCs) and evaluated the in vivo long‐term viability and safety of grafts.

Noninvasive continuous positive airway pressure delivered using a pediatric helmet in dogs recovering from general anesthesia

OBJECTIVE To evaluate the feasibility and efficacy of noninvasive continuous positive airway pressure (CPAP) administered with a pediatric helmet in healthy dogs recovering from general anesthesia. DESIGN Randomized, cross-over, clinical study. SETTING University teaching hospital. ANIMALS Fifteen healthy female, client-owned dogs recovering from general anesthesia following elective ovariohysterectomy. INTERVENTIONS All dogs received the same standardized anesthetic protocol (acepromazine, morphine, propofol, and isoflurane in oxygen). After extubation, a pediatric helmet was placed on all dogs and connected to a venturi valve supplied with medical air. In all patients, the gas flow was set to 50 L/minute and the FiO2 to 0.21. Dogs received the following sequence of treatments, each lasting 20 minutes: 0 CPAP (pre-CPAP), CPAP of 5 cm H2 O (CPAP), and again 0 CPAP (post-CPAP). MEASUREMENTS AND MAIN RESULTS During the entire study, the following data were collected: pressure and FiO2 inside the helmet, mean arterial pressure, respiratory rate, heart rate, sedation score (0 = awake, 10 = deep sedation), and tolerance to the helmet (0 = excellent, 4 = poor). At the end of each phase, an arterial blood sample was sampled. As compared with the pre-CPAP and the post-CPAP periods, during the CPAP period, the PaCO2 , alveolar-arterial oxygen gradient (P[A-a]O2 ), and respiratory rate significantly decreased. The PaO2 was higher at CPAP (105.6 ± 4.0 mm Hg) compared with pre-CPAP (80.6 ± 6.9 mm Hg) and post-CPAP (86.7 ± 5.8 mm Hg). Tolerance and sedation scores during the CPAP period were not different from those in the pre-CPAP and post-CPAP periods. CONCLUSIONS Noninvasive CPAP applied through a helmet is a feasible and effective supportive technique in dogs recovering from general anesthesia.

Ultrasonographic findings and outcomes of dogs with suspected migrating intrathoracic grass awns: 43 cases (2010–2013)

OBJECTIVE To describe ultrasonographic findings and outcomes for dogs with suspected migrating intrathoracic grass awns. DESIGN Retrospective case series. ANIMALS 43 client-owned dogs. PROCEDURES Records for dogs with suspected migrating intrathoracic grass awns examined between 2010 and 2013 were reviewed. Ultrasonographic images and additional information such as signalment and pleural fluid analysis, radiographic, bronchoscopic, and CT findings were collected. Surgical treatments and outcomes were also reviewed. RESULTS Transthoracic or transesophageal ultrasonography revealed grass awns in the pleural space (n = 13) or pulmonary parenchyma (10) of 23 dogs. Surgical removal of grass awns was successful on the first attempt in 21 of these 23 dogs (including 11/23 that had intraoperative ultrasonography performed to aid localization and removal of the awn). In the remaining 2 dogs, a second surgery was required. Twenty dogs with evidence of migrating intrathoracic grass awns had no foreign body identified on initial ultrasonographic evaluation and were treated medically; 16 developed draining fistulas, and awns identified ultrasonographically at follow-up visits were subsequently removed from the sublumbar region (n = 10) or thoracic wall (6). The remaining 4 dogs had no grass awn visualized. Clinical signs resolved in all dogs. CONCLUSIONS AND CLINICAL RELEVANCE Transthoracic, transesophageal, and intraoperative ultrasonography were useful for localization and removal of migrating intrathoracic grass awns. Ultrasonography may be considered a valuable and readily available diagnostic tool for monitoring dogs with suspected migrating intrathoracic grass awns.

EVALUATION OF A BUTORPHANOL, DETOMIDINE, AND MIDAZOLAM COMBINATION FOR IMMOBILIZATION OF CAPTIVE NILE LECHWE ANTELOPES (KOBUS MAGACEROS)

Field immobilization of captive antelope may be required for medical examination, blood sample collection, and animal identification. The aim of this study was to evaluate the effects of a combination of butorphanol, detomidine, and midazolam (BDM) and its partial reversibility in Nile lechwe antelope (Kobus megaceros). Nine captive lechwes, weighing 28–64 kg, were immobilized, in February 2011, with butorphanol 0.20±0.05 (mean±SD) mg/kg, detomidine 0.20±0.05 mg/kg, and midazolam 0.31±0.08 mg/kg administered intramuscularly (IM) with a blowpipe. Physiologic parameters and depth of anesthesia were recorded when the animals became recumbent at 19.55±8.36 min after darting (T0) and after 10 (T10), 20 (T20), and 30 (T30) min. An arterial blood sample was collected at T20. At the end of the procedures, immobilization was partially reversed with atipamezole 0.25 mg/kg IM. Quality of induction, immobilization, and recovery was scored. The BDM combination induced immobilization and lateral recumbency in 13.44±5.61 min. Median induction score (scored 1 [excellent] to 4 [poor]) was 1 (range 1–2). Heart rate varied 40–104 beats/min, respiratory rate 16–108 breaths/min, and rectal temperature 36.5–40.3 C. Hyperthermia was observed and rapidly treated in three animals that demonstrated insufficient immobilization after darting. Arterial blood gas analyses revealed a mean pH of 7.43±0.07, partial arterial pressure of CO2 of 44.1±6.0 mmHg, partial arterial pressureof O2 of 74.0±13.5 mmHg, and an arterial O2 saturation of 94.77±3.96%. Recovery was smooth and animals were walking in 13.44±7.85 min. Median recovery score (1 = excellent to 4 = poor) was 1 (range 1–2). The BDM was effective in immobilizing captive healthy lechwes with minimal cardiorespiratory changes.

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.