Objective: To evaluate, in a lung model simulating a mechanically ventilated patient, the efficiency and safety of the manual hyperinflation (MH) maneuver as a means of removing pulmonary secretions. Methods: Eight respiratory therapists (RTs) were asked to use a self-inflating manual resuscitator on a lung model to perform MH as if to remove secretions, under two conditions: as routinely applied during their clinical practice; and after receiving verbal instructions based on expert recommendations. In both conditions, three clinical scenarios were simulated: normal lung function, restrictive lung disease, and obstructive lung disease. Results: Before instruction, it was common for an RT to compress the resuscitator bag two times, in rapid succession. Proximal pressure (Pprox) was higher before instruction than after. However, alveolar pressure (Palv) never exceeded 42.5 cmH2O (median, 16.1; interquartile range [IQR], 11.7-24.5), despite Pprox values as high as 96.6 cmH2O (median, 36.7; IQR, 22.9-49.4). The tidal volume (VT) generated was relatively low (median, 640 mL; IQR, 505-735), and peak inspiratory flow (PIF) often exceeded peak expiratory flow (PEF), the median values being 1.37 L/s (IQR, 0.99-1.90) and 1.01 L/s (IQR, 0.55-1.28), respectively. A PIF/PEF ratio < 0.9 (which theoretically favors mucus migration toward the central airways) was achieved in only 16.7% of the maneuvers. Conclusions: Under the conditions tested, MH produced safe Palv levels despite high Pprox. However, the MH maneuver was often performed in a way that did not favor secretion removal (PIF exceeding PEF), even after instruction. The unfavorable PIF/PEF ratio was attributable to overly rapid inflations and low VT.

Keywords: Physical therapy modalities; Respiratory therapy; Respiratory mechanics; Positive-pressure respiration.

Objective: To analyze psychological morbidity as a moderator of the relationship between smoking representations and quality of life in smokers and former smokers, as well as to determine which psychological variables discriminate between smokers with and without the intention to quit smoking. Methods: This was a quantitative, correlational cross-sectional study involving a convenience sample of 224 smokers and 169 former smokers. Results: In smokers and former smokers, psychological morbidity had a moderating effect on the relationship between mental/physical quality of life and smoking representations (cognitive representations, emotional representations, and comprehensibility). Smokers with the intention to quit smoking more often presented with low comprehensibility, threatening emotional representations, behavioral beliefs, and perceived behavioral control, as well as with normative/control beliefs, than did those without the intention to quit. Conclusions: The results of this study underscore the importance of the moderating effect exerted by psychological morbidity, as well as that of sociocognitive variables, among smokers who have the intention to quit smoking.

Objective: The reproduction of an experimental emphysema model in rats by intratracheal instillation of papain was proposed for the evaluation of lung volume reduction surgeries. Method: The study used orotracheal instillation of papain (20 mg/kg) dissolved in 0.9% saline solution. Forty days after instillation, animals underwent mechanical ventilation. Elastance and resistance of the respiratory system were measured, and the rats were sacrificed by having their lungs removed. The pulmonary tissue of the animals was qualitatively analyzed with hematoxylineosin staining and submitted to morphometric analysis for the measurement of the mean alveolar diameter. The pulmonary tissue was also subjected to resorcin-fuchsin staining for the identification of elastic fibers, which were quantified in alveolar septa by digital imaging. Results: In the animals instilled with papain, the histological analysis of the lungs showed pan-acinar emphysema, with rupture of alveolar septa and hyperdistention. Morphometric analysis showed higher mean values for mean alveolar diameter in the lungs of the animals submitted to papain (149.08 μm and 100.56 μm) as compared to the group receiving saline solution (64.08 μm and 75.90 μm). The quantification of elastic fibers of alveolar septa of papain-treated animals was 70% lower than in the animals receiving saline solution. Mechanic ventilation did not show differences in respiratory system resistance of animals receiving papain or saline solution. Respiratory system elastance was lower in the group receiving papain than in the group receiving saline solution, showing a functional status compatible with pulmonary emphysema, with decreased elasticity of the pulmonary tissue. Conclusion: The reproduction of an experimental model of pan-acinar pulmonary emphysema in rats was achieved by papain instillation through the respiratory tree with functional and morphologic evidences.

Keywords: Pulmonary emphysema. Experimental model. Papain. Rats. Drug instillations.

Objective: To compare the resistance of manual suture with that of mechanical suture immediately after the suture of the left bronchial stump of dogs submitted to pneumonectomy. Methods: A total of 15 mixed-breed dogs of both genders, each weighing between 8 and 23 kg, were randomly divided into 2 groups. In group I (n = 7), the bronchial stump was sutured manually (the Sweet method) and, in group II (n = 8), it was stapled. Immediately after the closure of the bronchial stump, the intratracheal pressure was progressively increased in a controlled manner. Results: The mean rupture pressure of the bronchial stump suture line was 33.71 mmHg in group I and 89.87 mmHg in group II (p < 0.01). Conclusion: These data allowed us to conclude that mechanical suture of the bronchial stump, submitted to pressure immediately after closure, is more resistant than is manual suture in dogs submitted to pneumonectomy.

Keywords: Comparative study; Suture techniques; Bronchial fistula; Pneumonectomy.

Introduction: Surgical procedures requiring aortic occlusion have been associated with pulmonary reperfusion injury. The authors studied the pulmonary edema in a reperfusion injury model by aortic occlusion in rats. Material and methods: Thirty-three Wistar rats were anesthetized with intraperitoneal injection of sodium pentobarbital (20 mg/kg). Using a midline abdominal incision, the infra-renal aorta was isolated and the animals were randomized into three groups. Ischemia-reperfusion group (IRG, n = 5): rats that underwent 30 min of aorta occlusion and were followed during 120 min of reperfusion. Ischemia group (IG, n = 5): rats that underwent 30 min of aorta occlusion. Control group (CG, n = 5): rats that underwent sham operations without aorta occlusion and were followed during 150 min. Histopathologic examination of the right lung was performed. The pulmonary edema was studied by morphometric analysis and so was the leukocytes infiltration. Eighteen rats (6 rats in each group) were studied with respect to lung fresh/dry weight ratio. ANOVA was used to analyze the morphometric results and the lung fresh/dry weight ratio, with Bonferroni adjustment for paired multiple comparisons. Animals of the IRG presented more pulmonary edema than those of the IG and CG (0.24 vs. 0.17 and 0.17, p < 0.001). There was no difference between the groups regarding the lung fresh/dry weight ratio. There were more inflammatory cells in the lungs of the rats submitted to ischemia-reperfusion. The authors concluded that infra-renal abdominal aorta cross-clamping and unclamping are associated with pulmonary edema. This edema is not induced by elevation of the hydrostatic pressure due to the aortic occlusion, since it was not seen in animals that were only submitted to ischemia.

Keywords: ischemia, reperfusion, pulmonary edema, inbred strains rats

Diabetes mellitus is an endocrine/metabolic disorder characterized by hyperglycemia. Its impact on the respiratory system is characterized by functional changes and alterations in gas exchange. The objective of this study was to evaluate the increase in oxidative stress and the potential damages to the lung structure in an experimental model of streptozotocin-induced diabetes. We conducted histological, biochemical and blood gas analyses in the lungs of diabetic rats. We concluded that the effects of experimental diabetes mellitus include oxidative stress, structural changes in the lung tissue and altered gas exchange.

Keywords: Lung; Diabetes mellitus; Oxidative stress; Diabetes mellitus, experimental; Free radicals.

Objective: The aim of this study was to identify the best experimental model in which to observe the pulmonary alterations characterizing hepatopulmonary syndrome (HPS). Methods: Male Wistar rats, with mean weight of 250 g, were used in four experimental models: inhaled carbon tetrachloride; intraperitoneal carbon tetrachloride; partial portal vein ligation; and bile duct ligation (BDL). The animals in all groups were divided into control and experimental subgroups. The following variables were measured: transaminase levels; blood gases; lipoperoxidation, using thiobarbituric acid reactive substances (TBARS) and chemiluminescence; and levels of superoxide dismutase (SOD) anti-oxidant activity. Anatomopathological examination of the lung was also performed. Results: There were statistically significant differences between the BDL control and BDL experimental groups: aspartate aminotransferase (105.3 ± 43 vs. 500.5 ± 90.3 IU/L); alanine aminotransferase (78.75 ± 37.7 vs. 162.75 ± 35.4 IU/L); alkaline phosphatase (160 ± 20.45 vs. 373.25 ± 45.44 IU/L); arterial oxygen tension (85.25 ± 8.1 vs. 49.9 ± 22.5 mmHg); and oxygen saturation (95 ± 0.7 vs. 73.3 ± 12.07%). Lipoperoxidation and antioxidant activity also differed significantly between the two BDL groups (control vs. experimental): TBARS (0.87 ± 0.3 vs. 2.01 ± 0.9 nmol/mg protein); chemiluminescence (16008.41 ± 1171.45 vs. 20250.36 ± 827.82 cps/mg protein); and SOD (6.66 ± 1.34 vs. 16.06 ± 2.67 IU/mg protein). The anatomopathological examination confirmed pulmonary vasodilatation in the BDL model. In the other models, there were no alterations that were characteristic of HPS. Conclusions: The data obtained suggest that the BDL model can be used in future studies involving hepatic alterations related to oxidative stress and HPS.

Keywords: Hepatopulmonary syndrome; Lung; Oxidative stress; Rats.

Objective: To determine whether pulmonary mechanics are altered in mice with sepsis. Methods: A total of 40 Balb/c mice were divided into two groups: survival (n = 21) and pulmonary mechanics (n = 19). The survival group was divided into three subgroups: control (n = 7), sublethal (n = 7) and lethal (n = 7). The pulmonary mechanics group was also divided into three subgroups: control (n = 5), sublethal (n = 7) and lethal (n = 7). Sepsis was induced through cecal ligation and puncture, the latter varying in degree (sublethal or lethal). At eight hours after the intervention, pulmonary mechanics were measured through end-inflation occlusion. In the pulmonary mechanics group, the following variables were studied: total pressure, resistance, viscoelasticity, dynamic compliance and static compliance. The data obtained were analyzed using one-way ANOVA. Results: The data for the survival group indicate the efficacy of the model employed. There were no statistically significant differences among the pulmonary mechanics subgroups in terms of dynamic compliance, static compliance, total pressure, resistance or viscoelasticity. Conclusion: At eight hours after cecal ligation and puncture, there were no changes in the lung parenchyma, nor were any alterations observed in the viscous and viscoelastic components of the lung.

Keywords: Sepsis; Respiratory mechanics; Lung/injuries; Punctures/instrumentation; Respiratory distress syndrome, adult; Mice

Objective: To compare two models of pulmonary hypertension (monocrotaline and monocrotaline+pneumonectomy) regarding hemodynamic severity, structure of pulmonary arteries, inflammatory markers (IL-1 and PDGF), and 45-day survival. Methods: We used 80 Sprague-Dawley rats in two study protocols: structural analysis; and survival analysis. The rats were divided into four groups: control; monocrotaline (M), pneumonectomy (P), and monocrotaline+pneumonectomy (M+P). In the structural analysis protocol, 40 rats (10/group) were catheterized for the determination of hemodynamic variables, followed by euthanasia for the removal of heart and lung tissue. The right ventricle (RV) was dissected from the interventricular septum (IS), and the ratio between RV weight and the weight of the left ventricle (LV) plus IS (RV/LV+IS) was taken as the index of RV hypertrophy. In lung tissues, we performed histological analyses, as well as using ELISA to determine IL-1 and PDGF levels. In the survival protocol, 40 animals (10/group) were followed for 45 days. Results: The M and M+P rats developed pulmonary hypertension, whereas the control and P rats did not. The RV/LV+IS ratio was significantly higher in M+P rats than in M rats, as well as being significantly higher in M and M+P rats than in control and P rats. There were no significant differences between the M and M+P rats regarding the area of the medial layer of the pulmonary arteries; IL-1 and PDGF levels; or survival. Conclusions: On the basis of our results, we cannot conclude that the monocrotaline+pneumonectomy model is superior to the monocrotaline model.

Keywords: Monocrotaline; Hypertension, pulmonary; Pneumonectomy; Interleukin-1; Receptor, platelet-derived growth factor beta.

Since they were first established, ex vivo models of lung reconditioning have been evaluated extensively. When rejected donor lungs are used, the great variability among the cases can hinder the progress of such studies. In order to avoid this problem, we developed a technique that consists of separating the lung block into right and left blocks and subsequently reconnecting those two blocks. This technique allows us to have one study lung and one control lung.

Keywords: Lung transplantation; Transplantation conditioning; Organ preservation; Organ preservation solutions.

Objective: To evaluate the effects that administering dexamethasone before the induction of ventilator-induced lung injury (VILI) has on the temporal evolution of that injury. Methods: Wistar rats were allocated to one of three groups: pre-VILI administration of dexamethasone (dexamethasone group); pre-VILI administration of saline (control group); or ventilation only (sham group). The VILI was induced by ventilation at a high tidal volume. Animals in the dexamethasone and control groups were euthanized at 0, 4, 24, and 168 h after VILI induction. We analyzed arterial blood gases, lung edema, cell counts (total and differential) in the BAL fluid, and lung histology. Results: At 0, 4, and 24 h after VILI induction, acute lung injury (ALI) scores were higher in the control group than in the sham group (p < 0.05). Administration of dexamethasone prior to VILI induction decreased the severity of the lung injury. At 4 h and 24 h after induction, the ALI score in the dexamethasone group was not significantly different from that observed for the sham group and was lower than that observed for the control group (p < 0.05). Neutrophil counts in BAL fluid were increased in the control and dexamethasone groups, peaking at 4 h after VILI induction (p < 0.05). However, the neutrophil counts were lower in the dexamethasone group than in the control group at 4 h and 24 h after induction (p < 0.05). Pre-treatment with dexamethasone also prevented the post-induction oxygenation impairment seen in the control group. Conclusions: Administration of dexamethasone prior to VILI induction attenuates the effects of the injury in Wistar rats. The molecular mechanisms of such injury and the possible clinical role of corticosteroids in VILI have yet to be elucidated.

Keywords: Ventilator-induced lung injury; Dexamethasone; Respiratory distress syndrome, adult.

Objective: Although manual hyperinflation (MH) is widely used for pulmonary secretion clearance, there is no evidence to support its routine use in clinical practice. Our objective was to evaluate the effect that MH combined with expiratory rib cage compression (ERCC) has on the length of ICU stay and duration of mechanical ventilation (MV). Methods: This was a prospective randomized controlled clinical trial involving ICU patients on MV at a tertiary care teaching hospital between January of 2004 and January of 2005. Among the 49 patients who met the study criteria, 24 and 25 were randomly assigned to the respiratory physiotherapy (RP) and control groups, respectively. Of those same patients, 6 and 8, respectively, were later withdrawn from the study. During the 5-day observation period, the RP patients received MH combined with ERCC, whereas the control patients received standard nursing care. Results: The two groups were similar in terms of the baseline characteristics. The intervention had a positive effect on the duration of MV, as well as on the ICU discharge rate and Murray score. There were significant differences between the control and RP groups regarding the weaning success rate on days 2 (0.0% vs. 37.5%), 3 (0.0% vs. 37.5%), 4 (5.3% vs. 37.5%), and 5 (15.9% vs. 37.5%), as well as regarding the ICU discharge rate on days 3 (0% vs. 25%), 4 (0% vs. 31%), and 5 (0% vs. 31%). In the RP group, there was a significant improvement in the Murray score on day 5. Conclusions: Our results show that the use of MH combined with ERCC for 5 days accelerated the weaning process and ICU discharge.

Keywords: Physical therapy modalities; Ventilator weaning; Length of stay.

Objective: To investigate the effects of manual chest compression (MCC) on the expiratory flow bias during the positive end-expiratory pressure-zero end-expiratory pressure (PEEP-ZEEP) airway clearance maneuver applied in patients on mechanical ventilation. The flow bias, which influences pulmonary secretion removal, is evaluated by the ratio and difference between the peak expiratory flow (PEF) and the peak inspiratory flow (PIF). Methods: This was a crossover randomized study involving 10 patients. The PEEP-ZEEP maneuver was applied at four time points, one without MCC and the other three with MCC, which were performed by three different respiratory therapists. Respiratory mechanics data were obtained with a specific monitor. Results: The PEEP-ZEEP maneuver without MCC was enough to exceed the threshold that is considered necessary to move secretion toward the glottis (PEF − PIF difference > 33 L/min): a mean PEF − PIF difference of 49.1 ± 9.4 L/min was achieved. The mean PEF/PIF ratio achieved was 3.3 ± 0.7. Using MCC with PEEP-ZEEP increased the mean PEF − PIF difference by 6.7 ± 3.4 L/min. We found a moderate correlation between respiratory therapist hand grip strength and the flow bias generated with MCC. No adverse hemodynamic or respiratory effects were found. Conclusions: The PEEP-ZEEP maneuver, without MCC, resulted in an expiratory flow bias superior to that necessary to facilitate pulmonary secretion removal. Combining MCC with the PEEP-ZEEP maneuver increased the expiratory flow bias, which increases the potential of the maneuver to remove secretions.

Keywords: Physical therapy modalities; Critical care; Respiration, artificial; Bodily secretions.

Small animal models are particularly suitable for lung preservation studies, because they are simple and cost-effective. This brief communication focuses on the technical description of an ex vivo lung perfusion model in rats by means of a commercially available apparatus, which was the first to be installed in a thoracic surgery research laboratory in Brazil. The model and its preparation, together with its applications for lung preservation studies, are described in detail. All technical details can also be seen in a video posted on the website of the Brazilian Journal of Pulmonology.

Keywords: Lung transplantation; Reperfusion injury; Rats; Models, animal.

Objective: To describe the development of a silicone stent and perform in vivo testing for biocompatibility/applicability in the normal canine trachea. Methods: Four different densities were tested in order to obtain the silicone prototypes. The pressure required for compression considering a contact area of 1 cm2, and a 30% reduction in diameter was calculated for each density. The best density was 70-75 Shore A hardness. Powdered barium sulfate was added to the silicone to make the stent radiopaque and easily identifiable in radiological imaging. This novel stent presents a corrugated external surface with discontinuous and protruding arcs resembling the tracheobronchial rings (for intercalation and fixation in the lumen of the lower airways), a highly polished inner surface and smooth extremities (to prevent friction-related damage). The prototype considered most appropriate in terms of rigidity and flexibility was bronchoscopically implanted in normal canine tracheas. After eight weeks, the animals were euthanized, and the tracheas were removed for anatomopathological analysis. Results: There were no postimplantation complications, and none had to be removed. After eight weeks, the devices were found to be well-positioned. Histopathology revealed a well-preserved epithelial basal membrane, foci of denuded epithelium, mild submucosal inflammatory infiltrate with scattered granulation tissue, vascular neoformation, and no microorganisms. Conclusions: The stent developed proved resistant to mechanical stress, biocompatible in the canine trachea and well-preserved at the study endpoint.

Keywords: Implants, experimental; Silicones; Biocompatible materials.

Background - The critical donor shortage in pediatric pulmonary transplantation has prompted lobar transplantation from living-related. However, in the case of great size discrepancy between the adult donor and the small child recipient, a pulmonary segment or medium lobe represents grafts with restricted vascular bed. The authors hypothesized that this type of graft may develop pulmonary hypertension in the recipient by the end of the growth period. Methods - This hypothesis was investigated in a porcine survival model of lung transplantation in piglets. There were three groups for comparison purposes: I (n = 4) - transplantation of the upper lobe from an adult donor, graft being proportional to the recipient but irrigated by two arterial rami only; II (n = 5) - transplantation of the lower lobe from an adult donor, graft being oversized to the recipient and having adequate vascular bed; III (n = 6) - transplantation of immature lung, from matched-sized donor. Graft function was studied three months after the transplantation, when the growth period was completed. Results - The pulmonary artery pressure of grafts in group I (51.8 ± 2.1 mmHg) was increased compared to that of group II (40.4 ± 2.5 mmHg) and of group III (34.8 ± 1.5 mmHg), reaching statistical significance (p = 0.0003). Conclusions - The lobar graft proportional to the recipient, with restricted vascular bed, had hampered hemodynamic performance in the growing animal. These results suggest that graft proportionality should be secondary to an adequate vascular bed.

Keywords: Lung transplantation. Lobar transplantation, experimental. Swine.

We aimed to test a new model of self-expanding tracheal stent so that it might be made available for clinical use. Using direct laryngoscopy, we placed polyurethane-coated, nitinol stents into the middle third of the trachea in 25 New Zealand rabbits. After a mean observation period of 26 days, we evaluated stent migration, degree of expansion, attachment, adherence, formation of granulation tissue, presence of inflammatory infiltrate, parietal involvement, and epithelial lining. The results showed complete radial expansion, little adherence to the tracheal mucosa, and low tissue attachment, as well as high rates of granuloma formation and stent migration. This new model proved to be biocompatible and showed a behavior similar to that of other stents on the market.

Keywords: Prosthesis implantation; Tracheal stenosis; Rabbits; Stents.

We evaluated the effect of aminoguanidine on pulmonary oxidative stress and lung structure in an experimental model of diabetes mellitus. Thiobarbituric acid reactive substances (TBARS), histology and arterial blood gases were evaluated in animals with diabetes mellitus (DM group), animals with diabetes mellitus treated with aminoguanidine (DM+AG group), and controls. The TBARS levels were significantly higher in the DM group than in the control and DM+AG groups (2.90 ± 1.12 vs. 1.62 ± 0.28 and 1.68 ± 0.04 nmol/mg protein, respectively), as was PaCO2 when compared with that of the control group (49.2 ± 1.65 vs. 38.12 ± 4.85 mmHg), and PaO2 was significantly higher in the control group (104.5 ± 6.3 vs. 16.30 ± 69.48 and 97.05±14.02 mmHg, respectively). In this experimental model of diabetes mellitus, aminoguanidine reduced oxidative stress, structural tissue alterations, and gas exchange.

Keywords: Oxidative stress; Diabetes mellitus, experimental; Lung.