Effects of hyperoxia in the presence of acute lung injury

We employed a multiple-dose, oleic acid (OA) model to evaluate the susceptibility to oxygen toxicity of rabbits with acute lung injury (ALI). The rabbits were partitioned into four groups: ALI group (n = 8) received OA (0.04 ml/kg iv) and again at two consecutive 24-h intervals and breathed room air (RA); hyperoxic O2/ALI group (n = 8) underwent similar OA injection protocol and breathed an FIO2 greater than or equal to 0.96; oxygen group (n = 8) received identical injection protocol with normal saline (NS) and breathed an FIO2 greater than or equal to 0.96; and control (CTR) group (n = 5) received isovolume NS injections and breathed RA. Arterial blood pH and gas tensions were measured before and 24, 48, and 60 h after ALI. Surviving animals were killed at 72 h and body weight (BW) was determined at autopsy; then the lungs were removed and weighed (LW). The mortality for animals exposed to hyperoxia was significantly (p less than or equal to .02) greater than those breathing RA, regardless of the presence or absence of ALI. Blood pH was lower (p less than or equal to .05) in all animals but the CTR group. However, acidemia was significantly greater in both hyperoxic groups compared to animals in the CTR and ALI/RA. Inflation and deflation lung-thorax compliances were lower (p less than or equal to .05) and percent lung weight of terminal body weight (LW/BW) was higher (p less than or equal to .05) after hyperoxia with or without ALI compared to CTR animals regardless of FIO2.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effect of hyperbaric oxygen on endotoxin-induced lung injury in rats

Oxygen therapy remains the main component of the ventilation strategy for treatment of patients with acute lung injury. Hyperbaric oxygen therapy (HBO(2)) is the intermittent administration of 100% oxygen at pressure greater than sea level and has been applied widely to alleviate a variety of hypoxia-related tissue injuries. The purpose of this study was to evaluate the effect of hyperbaric oxygen on acute lung injury induced by intratracheal spraying of lipopolysaccharide (LPS) in rats. Male Sprague-Dawley rats underwent implantation of a carotid artery catheter under general anesthesia. Aerosolized LPS was delivered twice into the lungs via intratracheal puncture. Animals were either breathing room air (n = 27) or subjected to hyperbaric oxygen (HBO(2)) exposure (n = 27) 1 h after LPS spraying. Acute lung injury was evaluated 5 h and 24 h later. Compared with the control group, intratracheal spraying of LPS caused profound hypoxemia, greater wet/dry weight ratio (W/D) of the lung (5.67 +/- 0.22 vs. 4.98 +/- 0.19), and higher protein concentration (1706 +/- 168 vs. 200 +/- 90 mg/L) and LDH activity (129 +/- 30 vs. 46 +/- 15, mAbs/min) in bronchoalveolar lavage (BAL) fluid. Intratracheal spraying of LPS also caused significant WBC sequestration in the lung tissue. HBO2 treatment significantly reverted hypoxemia, reduced lung injury measures evaluated at 5 and 24 h, and enhanced 24-h animal survival rate (chi = 5.08, P = 0.024). The malondialdehyde (MDA) concentrations in lung tissue and serum were both increased after LPS spraying. Neither single HBO(2) therapy nor five sequential daily treatments enhanced MDA production in lung tissue or serum. Our results suggested that hyperbaric oxygen might reduce acute lung injury caused by intratracheal spraying of LPS in rats. This treatment modality is not associated with enhancement of oxidative stress to the lung.     

高压氧对油酸诱导大鼠急性肺损伤作用的实验研究

目的 探讨高压氧(HBO)对油酸(OA)诱导大鼠急性肺损伤(ALI)的干预作用.方法 80只SD大鼠按随机数字表法分为4组.OA组30只,经鼠尾静脉注射OA 0.15 ml/kg制备ALI模型,分别于制模后4 h、3 d、7 d各随机活杀10只;OA+HBO组20只,在HBO治疗箱给予2.5 atm(1 atm=101.325 kPa)下单次治疗90 min,分别于HBO治疗后3 d、7 d各随机活杀10只;单纯HBO干预组20只,分别于HBO治疗后3 d、7 d各随机活杀10只;另设正常对照组10只.取腹主动脉血进行血气分析,测定血清肿瘤坏死因子-α(TNF-α)、白细胞介素-1β(IL-1β)、IL-6;取左肺标本,观察大体形态改变及镜下病理学改变;取右肺,测定湿/干重(W/D)比值.结果 OA组4 h后动脉血氧分压(PaO2,mm Hg,1 mm Hg=0.133 kPa)由107.70±5.37降至57.40±2.63;肉眼可见肺脏明显淤血、水肿;光镜下肺泡正常结构消失,间质水肿增宽,大量炎性细胞浸润,毛细血管明显扩张、透明膜形成;W/D比值较正常对照组明显增加(6.94±0.44比4.59±0.44,P<0.05),血清TNF-α、IL-1β、IL-6水平升高[TNF-α(μg/L):18.52±1.20比5.27±0.61,IL-1β(μg/L):13.73±1.37比6.13±1.51,IL-6(μg/L):14.51±1.21比11.14±0.89].经HBO治疗3 d、7 d时PaO2(mm Hg,3 d:79.20±1.68比59.00±2.70,7 d:94.30±3.77比74.00±3.85)、肺W/D比值(3 d:7.43±0.73比9.82±0.99,7 d:6.75±1.14比8.77±1.60)均较OA组同期有不同程度改善(P<0.05或P<0.01).治疗3 d后HBO有降低血清中IL-1β(μg/L)的作用(6.46±1.99比9.09±1.09,P<0.05).结论 HBO治疗有改善ALI大鼠氧合,促进肺水吸收、抑制部分炎症介质产生的作用.     

Arterial oxygen values achieved by COPD patients breathing oxygen alternately via nasal mask and nasal cannula.

Ten patients with known but clinically stable chronic obstructive pulmonary disease (COPD) were studied while breathing low-flow (1-2 L/min) supplemental oxygen by nasal cannula and by biflow nasal mask. Although the increase in inspired oxygen when breathing with the cannula has been documented, the nasal mask has not been tested by measurement of PaO2 change. The mean age of the group was 64.6 years, and their mean PaO2 was 54 +/- 10.5 torr while they were at rest and breathing room air. Patients were each given oxygen alternately with the mask and cannula, with no change in flowrate; time was allowed between the two for equilibration and return to baseline values. PaO2 values were compared by t test for nonindependent samples, which provided a t value of 1.893, with P = 0.09. Differences in measured arterial saturation (SaO2) and PaCO2 also proved to be insignificant when patients breathed via the two devices. The conclude that the nasal cannula and the biflow nasal mask produce comparable PaO2 in patients who may need low-flow supplemental oxygen at rest. The mask can be considered an alternative oxygen appliance if preferred by patients because of comfort.     

Aerosolized beta(2)-adrenergic agonists achieve therapeutic levels in the pulmonary edema fluid of ventilated patients with acute respiratory failure

OBJECTIVE: Experimental studies demonstrate that beta-adrenergic agonists markedly stimulate alveolar fluid clearance if concentrations of 10(-6) M are achieved in alveolar fluid. However, no studies have determined whether aerosolized beta-adrenergic agonists are delivered to the distal air spaces of the lung in therapeutic concentrations in patients with pulmonary edema. DESIGN AND SETTING: This retrospective study measured albuterol levels in the pulmonary edema fluid and plasma from mechanically ventilated patients with pulmonary edema from a hydrostatic mechanism ( n=10) or from acute lung injury ( n=12). MEASUREMENTS AND RESULTS: After a total aerosolized albuterol dose of 4.2+/-3.2 mg in the prior 6 h the median pulmonary edema fluid albuterol level was 1,250 ng/ml (10(-6) M) in patients with hydrostatic pulmonary edema; after 3.5+/-2.6 mg the figure was 1,240 ng/ml (10(-6) M) in patients with pulmonary edema from acute lung injury. Plasma albuterol levels were much lower, with a median of 5.2 ng/ml (0.01 x 10(-6) M) in patients with hydrostatic pulmonary edema and 3.1 ng/ml (0.01 x 10(-6) M) in patients with pulmonary edema from acute lung injury. CONCLUSIONS: These results provide the first evidence that levels of beta-adrenergic agonists that are physiologically efficacious in experimental models can be achieved with conventional delivery systems in ventilated, critically ill patients with acute respiratory failure from pulmonary edema.     

Measurement of minute ventilation in ventilator-dependent patients: need for standardization

OBJECTIVES: a) To determine the variation in methods used to measure minute ventilation (VE) in patients who receive mechanical ventilation; b) to determine the effect of supplemental oxygen on VE, respiratory rate (RR), and tidal volume (VT) measurements. DESIGN: Telephone survey of hospitals, and a randomized control trial. SETTING: Medical and surgical ICUs in a university hospital. PATIENTS: Thirty-three patients who had required mechanical ventilation because of the inability to sustain adequate spontaneous ventilation. All patients were considered ready to undergo a weaning trial by their physicians. INTERVENTIONS: Spontaneous VE, RR, VT, and SaO2 were measured both in the presence and absence of supplemental oxygen; measurements were obtained in a randomized manner. MEASUREMENTS AND MAIN RESULTS: a) In a telephone survey of hospitals throughout the country, we found that the measurement of VE is variably obtained during room air breathing or in the presence of supplemental oxygen. b) Measurements of VE increased from 11.0 +/- 0.8 L/min while patients received supplemental oxygen to 13.5 +/- 1.1 L/min while patients breathed room air (p less than .001). Of 15 patients who had a VE less than 10 L/min while receiving supplemental oxygen, seven developed a value greater than 10 L/min while breathing room air; thus, a weaning trial might have been inappropriately deferred in these patients. c) Mean SaO2 decreased from 95.0 +/- 0.6% while breathing supplemental oxygen to 90.2 +/- 1.1% while breathing room air (p less than .001). CONCLUSIONS: Measurements of VE in patients being considered for a weaning trial can result in significant oxygen desaturation if obtained during room air breathing, and the values obtained can significantly overestimate the patient's true ventilatory requirements, since most patients receive supplemental oxygen during a weaning trial. Standardized methods of measuring VE in critically ill patients need to be developed.     

The dependence of maximal flow in man on the airway gas physical properties

The changes in maximum expiratory flow rates after washing out lung air with a helium/oxygen mixture (He/O2, 80 : 20) were measured in 24 patients with chronic irreversible airflow obstruction (FEV1 1.77 +/- SD 0.39 litres; FVC 3.62 +/- 0.59 litres), and in six normal subjects. The percentage increase in flow breathing He/O2 was variable; however, it was similar in normal subjects and in patients with airflow obstruction, and in both groups decreased at low lung volumes. Contrary to previous studies, only three patients with chronic airflow obstruction failed consistently to increase flow rates by greater than or equal to 20% when breathing He/O2 at all lung volumes measured. In six normal subjects and 12 patients with chronic airflow obstruction airway gas viscosity was increased by breathing a neon/oxygen mixture (Ne/O2, 80 : 20). The response to Ne/O2 was again variable (normal subjects delta Vmax.40 4 +/- SD 14%; patients delta Vmax.40 18 +/- 8%). Only two normal subjects and one patient with airflow obstruction consistently reduced their flow rates when breathing Ne/O2. These results indicate either that there is no difference in the distribution of airflow resistance in normal subjects and in patients with chronic airflow obstruction, or that density as well as viscosity is an important determinant of flow in very small airways. In either case, He/O2 breathing is not a good discriminator of the site of airflow obstruction.     

水通道蛋白5在高氧肺损伤中的表达及调节机制

目的探讨水通道蛋白5(AQP5)在高氧肺损伤中的表达及其地塞米松对AQP5的调节作用。方法2周左右Wistar大鼠64只,按随机数字表法分为空气对照组、高氧暴露3、7、14d组和相应的地塞米松干预组。高氧暴露组置于常压氧仓中(O2体积分数≥95%);空气对照组置于同室常压空气中(O2体积分数为21%);各地塞米松干预组在暴露于空气或高氧的同时,经腹腔注射地塞米松5mg·kg-1·d-1,连续3d。采用逆转录聚合酶链反应(RT PCR)和免疫组化方法观察AQP5的mRNA表达和分布变化,并与地塞米松干预后进行比较分析。结果AQP5主要表达在肺泡型上皮细胞及气道分泌上皮顶质膜;与空气对照组相比,高氧暴露不同时间后,AQP5特异性表达部位保持不变,但随暴露时间延长,AQP5表达呈逐渐减弱趋势,高氧暴露3、7和14d,AQP5mRNA较空气对照组均降低(P均<0.05)。与同期高氧暴露组比较,地塞米松干预后不同时间点AQP5mRNA表达均无明显变化(P均>0.05)。结论高氧肺损伤时AQP5表达降低,可能是高氧肺损伤肺水肿形成的原因之一;而未见地塞米松对高氧肺损伤AQP5的表达有调节作用。     

Increases in lung and brain water following experimental stroke: effect of mannitol and hypertonic saline

OBJECTIVE: Pulmonary edema is a serious condition following brain injury of diverse etiologies, including large hemispheric infarctions. We have previously shown that treatment with hypertonic saline attenuates cerebral edema associated with experimental ischemic stroke. In a well-characterized animal model of large ischemic stroke, we tested the hypotheses that lung water increases following cerebral ischemia and determined the effects of osmotherapy with hypertonic saline and mannitol on total lung water, as well as on cerebral edema. DESIGN: Prospective laboratory animal study. SETTING: Research laboratory in a university teaching hospital. SUBJECTS: Adult male Wistar rats (300-450 g, n = 103). INTERVENTIONS: Under controlled conditions of normoxia, normocarbia, and normothermia, spontaneously breathing, halothane-anesthetized (1.0-1.5%) rats were subjected to permanent middle cerebral artery occlusion by the intraluminal occlusion technique. MEASUREMENTS AND MAIN RESULTS: Cerebral perfusion was monitored by laser-Doppler flowmetry over ipsilateral parietal cortex to ensure adequate vascular occlusion. At 6 hrs following middle cerebral artery occlusion, rats were treated in a blinded randomized fashion with no intravenous fluids (n = 24), a continuous intravenous infusion (0.3 mL/hr) of 0.9% saline (n = 21), 20% mannitol (2 g/Kg) (n = 20), 5% hypertonic saline (n = 20), or 7.5% hypertonic saline (n = 18) as a chloride/acetate mixture (50:50) until the end of the experiment. Brains and lungs were harvested, and tissue water content was estimated by comparing wet-to-dry weight ratios of ipsilateral and contralateral cerebral hemispheres at 48 hrs postischemia. Sham-operated rats served as controls (n = 20). Serum osmolality was determined at the end of the experiment in all animals. Lung water content was increased significantly in rats subjected to middle cerebral artery occlusion and treated with no intravenous fluids (76.7 +/- 0.7%, 317 +/- 7 mOsm/L) (mean +/- sd) and saline (76.8 +/- 1.2%, 311 +/- 10 mOsm/L), compared with sham-operated controls (74.5 +/- 0.9%, 302 +/- 4 mOsm/L). Treatment with 20% mannitol (74.4 +/- 1.2%, 352 +/- 15 mOsm/L), 5% hypertonic saline (75.6 +/- 1.3%, 339 +/- 16 mOsm/L), and 7.5% hypertonic saline (74.9 +/- 0.7%, 360 +/- 23 mOsm/L) significantly attenuated lung water content. Hemispheric brain water content increased both in the ipsilateral ischemic and contralateral hemispheres treated with saline (ipsilateral, 85.1 +/- 1.7%; contralateral, 80.7 +/- 0.7%), compared with sham-operated controls (ipsilateral, 79.6 +/- 0.9%; contralateral, 79.5 +/- 0.9%), as well as in rats that received no fluids (ipsilateral, 84.6 +/- 1.8%; contralateral, 80.4 +/- 0.9%). Treatment with 5% hypertonic saline (ipsilateral, 83.8 +/- 1.0%; contralateral, 79.7 +/- 0.6%) and 7.5% hypertonic saline (ipsilateral, 82.3 +/- 1.3%; contralateral, 78.6 +/- 0.7%) resulted in attenuation of stroke-associated increases in brain water content to a greater extent than mannitol (ipsilateral, 83.6 +/- 1.6%; contralateral, 79.1 +/- 1.0%). CONCLUSIONS: In a well-characterized animal model of large ischemic stroke, total lung water content increases, which is likely neurogenic in origin. Attenuation of stroke-associated increases in lung and brain water content with continuous infusion of hypertonic saline may have therapeutic implication in the treatment of cerebral and pulmonary edema following ischemic stroke.     

Platelet activating factor mediates interleukin-2-induced lung injury in the rat.

Interleukin-2 was recently shown to cause acute lung injury characterized by microvascular permeability defect, interstitial edema, and leukosequestration. Similar responses can also be produced by platelet activating factor (PAF). Thus, the present study aimed to examine whether PAF plays a key role in the development of IL-2-induced lung injury in the anesthetized rat. Intravenous infusion (60 min) of recombinant human IL-2 at 10(5)-10(6) U/rat (n = 7-9) dose-dependently elevated lung water content (27 +/- 1%, P less than 0.01), myeloperoxidase activity (+84 +/- 23%, P less than 0.05), and serum thromboxane B2 (990 +/- 70%, P less than 0.01), but failed to alter blood pressure, hematocrit, serum tumor necrosis factor-alpha, and circulating leukocytes and platelets. Pretreatment (-30 min) with a potent and specific PAF antagonist, BN 50739 (10 mg/kg, intraperitoneally, n = 6) prevented the pulmonary edema (P less than 0.05) and thromboxane B2 production (P less than 0.01), and attenuated the elevation of lung myeloperoxidase activity (+18 +/- 16%, P less than 0.05) induced by IL-2. These data suggest that PAF is involved in the pathophysiological processes leading to IL-2-induced lung injury, and point to the potential therapeutic capacity of PAF antagonists in preventing pulmonary edema during IL-2 therapy.     

Effects of erythrapheresis on pulmonary haemodynamics and oxygen transport in patients with secondary polycythaemia and cor pulmonale

Reducing packed cell volume has been advocated as a therapeutic procedure in patients with polycythaemia secondary to hypoxic cor pulmonale. The aim of this investigation was to evaluate the effects of this manoeuvre on resting pulmonary haemodynamics and tissue oxygenation in 12 such patients. The subjects were studied whilst they were breathing air (n = 12), after breathing 35% oxygen for 30 min (n = 11) and breathing air 30 min after isovolaemic reduction in packed cell volume, from 0.61 +/- 0.02 to 0.50 +/- 0.02 (mean +/- SEM), by erythrapheresis (n = 12). Initial values for the group were: PaO2 6.5 +/- 0.3 kPa; red cell mass 152 +/- 12% predicted; mean pulmonary artery pressure (PAP) 41 +/- 3 mmHg; cardiac index 3.1 +/- 0.31 min-1 m-2. Breathing 35% oxygen reduced PAP by 3.1 +/- 1.0 mmHg (P less than 0.02), cardiac index by 0.28 +/- 0.121 min-1 m-2 (P less than 0.05) and right ventricular stroke work by 0.05 +/- 0.01 J (P less than 0.01). Systemic vascular resistance was unchanged. Systemic oxygen transport increased and peripheral oxygen consumption was unaltered. Erythrapheresis reduced blood viscosity at shear rates 23 S-1 and 230 S-1. PAP fell by 2.4 +/- 1.1 mmHg (P less than 0.05) and cardiac index increased by 0.32 +/- 0.091 min-1 m-2 (P less than 0.01), but right ventricular stroke work was unchanged. Systemic vascular resistance was reduced by 25 +/- 7 kPa S l-1 (P less than 0.01). Systemic oxygen transport decreased but peripheral oxygen consumption was unchanged.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effects of heparin and lisofylline on pulmonary function after smoke inhalation injury in an ovine model

OBJECTIVE: This study evaluates the effects of heparin alone and in combination with lisofylline, 1-(5-R-hydroxyhexyl)3,7-dimethylxanthine, on severe smoke injury. DESIGN: Prospective animal study with concurrent controls. SETTING: An animal laboratory. SUBJECTS: Eighteen 1-yr-old female sheep, weighing 24-32 kg. INTERVENTIONS: After smoke exposure and tracheostomy, animals were divided into three groups. Group S (n = 6) received nebulized saline through an endotracheal tube every 4 hrs for 48 hrs. Group H (n = 6) received 10,000 units of nebulized heparin every 4 hrs. Group LH (n = 6) was treated with nebulized heparin and intravenous infusion of lisofylline (10 mg x kg(-1) x hr(-1)) for 48 hrs after a bolus injection (20 mg/kg). Animals initially breathed room air spontaneously. If PaO2 was <50 torr and PaCO2 >60 torr, animals were mechanically ventilated. Sheep were killed 48 hrs postinjury. MEASUREMENTS AND MAIN RESULTS: Blood gases were measured serially. At 48 hrs, ventilation perfusion distribution mismatching was analyzed by using the multiple inert gas elimination technique. Lung malondialdehyde was determined. The postinjury increase in alveolar-arterial oxygen tension gradient (LH, 36.7 +/- 3.5 vs. S, 89.0 +/- 24.6 torr at 48 hrs) was significantly attenuated in those animals receiving LH. The percentage of pulmonary shunt, Qs/Qt (LH, 20.8 +/- 4.9 vs. S, 36.6 +/- 4.6%), and the percentage of animals that required ventilation (LH, 0 vs. S, 67%) were significantly reduced in LH. Multiple inert gas elimination technique study showed that the true shunt fraction was decreased in LH. Lung malondialdehyde was significantly less in LH (LH, 0.33 +/- 0.06 vs. S, 0.56 +/- 0.09 nmol/mg protein). There was no significant difference in any of these variables between H and S. CONCLUSION: Treatment with heparin alone did not attenuate pulmonary dysfunction after severe smoke injury. Combined treatment with nebulized heparin and systemic lisofylline had beneficial effects on pulmonary function in association with a decrease in blood flow to poorly ventilated areas and less lipid peroxidation.     

Effects of helium-oxygen on respiratory mechanics,gas exchange,and ventilation-perfusion relationships in a porcine model of stable methacholine-induced bronchospasm

OBJECTIVE: To explore the consequences of helium/oxygen (He/O(2)) inhalation on respiratory mechanics, gas exchange, and ventilation-perfusion (VA/Q) relationships in an animal model of severe induced bronchospasm during mechanical ventilation. DESIGN: Prospective, interventional study. SETTING: Experimental animal laboratory, university hospital. INTERVENTIONS: Seven piglets were anesthetized, paralyzed, and mechanically ventilated, with all ventilator settings remaining constant throughout the protocol. Acute stable bronchospasm was obtained through continuous aerosolization of methacholine. Once steady-state was achieved, the animals successively breathed air/O(2) and He/O(2) (FIO(2) 0.3), or inversely, in random order. Measurements were taken at baseline, during bronchospasm, and after 30 min of He/O(2) inhalation. RESULTS: Bronchospasm increased lung peak inspiratory pressure (49+/-6.9 vs 18+/-1 cm H(2)O, P<0.001), lung resistance (22.7+/-1.5 vs 6.8+/-1.5 cm H(2)O x l(-1).s, P<0.001), dynamic elastance (76+/-11.2 vs 22.8+/-4.1 cm H(2)O x l(-1), P<0.001), and work of breathing (1.51+/-0.26 vs 0.47+/-0.08, P<0.001). Arterial pH decreased (7.47+/-0.06 vs 7.32+/-0.06, P<0.001), PaCO(2) increased, and PaO(2) decreased. Multiple inert gas elimination showed an absence of shunt, substantial increases in perfusion to low VA/Q regions, and dispersion of VA/Q distribution. He/O(2) reduced lung resistance and work of breathing, and worsened hypercapnia and respiratory acidosis. CONCLUSIONS: In this model, while He/O(2) improved respiratory mechanics and reduced work of breathing, hypercapnia and respiratory acidosis increased. Close attention should be paid to monitoring arterial blood gases when He/O(2) is used in mechanically ventilated acute severe asthma.     

Biologically variable ventilation increases arterial oxygenation over that seen with positive end-expiratory pressure alone in a porcine model of acute respiratory distress syndrome

OBJECTIVES: We compared biologically variable ventilation (BVV) (as previously described) (1) with conventional control mode ventilation (CV) in a model of acute respiratory distress syndrome (ARDS) both at 10 cm H2O positive end-expiratory pressure. DESIGN: Randomized, controlled, prospective study. SETTING: University research laboratory. SUBJECTS: Farm-raised 3- to 4-month-old swine. INTERVENTIONS: Oleic acid (OA) was infused at 0.2 mL/kg/hr with FIO2 = 0.5 and 5 cm H2O positive end-expiratory pressure until PaO2 was < or =60 mm Hg; then all animals were placed on an additional 5 cm H2O positive end-expiratory pressure for the next 4 hrs. Animals were assigned randomly to continue CV (n = 9) or to have CV computer controlled to deliver BVV (variable respiratory rate and tidal volume; n = 8). Hemodynamic, expired gas, airway pressure, and volume data were obtained at baseline (before OA), immediately after OA, and then at 60-min intervals for 4 hrs. MEASUREMENTS AND MAIN RESULTS: At 4 hrs after OA injury, significantly higher PaO2 (213+/-17 vs. 123+/-47 mm Hg; mean+/-SD), lower shunt fraction (6%+/-1% vs. 18%+/-14%), and lower PaCO2 (50+/-8 vs. 65+/-11 mm Hg) were seen with BVV than with CV. Respiratory system compliance was greater by experiment completion with BVV (0.37+/-0.05 vs. 0.31+/-0.08 mL/cm H2O/kg). The improvements in oxygenation, CO2 elimination, and respiratory mechanics occurred without a significant increase in either mean airway pressure (14.3+/-0.9 vs. 14.9+/-1.1 cm H2O) or mean peak airway pressure (39.3+/-3.5 vs. 44.5+/-7.2 cm H2O) with BVV. The oxygen index increased five-fold with OA injury and decreased to significantly lower levels over time with BVV. CONCLUSIONS: In this model of ARDS, BVV with 10 cm H2O positive end-expiratory pressure improved arterial oxygenation over and above that seen with CV with positive end-expiratory pressure alone. Proposed mechanisms for BVV efficacy are discussed.     

Prevention of granulocyte-mediated oxidant lung injury in rats by a hydroxyl radical scavenger, dimethylthiourea

Toxic, partially reduced metabolites of oxygen (toxic oxygen radicals) are increasingly implicated in acute leukocyte-mediated tissue injury. To further probe the roles of oxygen radicals in acute lung edema, I studied the effects of a recently described and very potent oxygen radical scavenger, dimethylthiourea (DMTU) (Fox, R. B., R. N. Harada, R. M. Tate, and J. E. Repine, 1983, J. Appl. Physiol., 55:1456-1459) on polymorphonuclear leukocyte (PMN) oxidant function and on two types of lung injury mediated by oxygen radicals and PMN. DMTU (10 mM) blocked 79% of hydroxyl radical (OH) production by PMN in vitro without interfering with other PMN functions, such as O-2 production, myeloperoxidase activity, chemotaxis, degranulation, or aggregation. When isolated rat lung preparations were perfused with PMN activated to produce OH, lung weights were increased from 2.3 +/- 0.2 to 11.2 +/- 0.8 g. DMTU (10 mM) prevented 70% of these increases (lung weights, 5.0 +/- 1.1 g, P less than 0.005). Finally, when intact rats were exposed to 100% O2 for 66 h, lung weight:body weight ratios were increased from 5.78 +/- 0.33 to 8.87 +/- 0.16 g. DMTU (500 mg/kg) prevented 83% of this hyperoxia-induced lung edema in vivo (lung:body weight ratios, 6.05 +/- 0.21, P less than 0.001). Pharmacokinetic studies showed that DMTU diffused effectively into lung interstitial fluids and had a relatively long half-life (25-35 h) in the circulation. Because a variety of oxygen radicals, such as superoxide (O-2), hydrogen peroxide (H2O2), or OH are produced by PMN, there is usually some uncertainty about which one is responsible for injury. However, in these studies, DMTU did not scavenge O-2 and scavenged H2O2 only very slowly while scavenging OH very effectively. Therefore, DMTU may be useful in the investigation of the roles of oxygen radicals, especially OH, in acute granulocyte-mediated tissue injury.     

Hyperbaric oxygen attenuates lipopolysaccharide-induced acute lung injury

OBJECTIVES: To study the effect of hyperbaric oxygen therapy in alleviating acute lung injury induced by lipopolysaccharide (LPS) in rats.DESIGN AND INTERVENTIONS: The rats received an intraperitoneal injection of LPS (15 mg/kg). Animals were either breathing air at 1 ATA or subjected to hyperbaric oxygen (HBO(2)) therapy. The HBO(2) therapy was carried out in a hyperbaric chamber at a pressure of 3 ATA for 90 min. In another two groups, LPS-treated rats also received intraperitoneal injection of N(omega)-nitro-L-arginine (LNAME, 25 mg/kg) or L-N(6)-(iminoethyl)lysine (LNIL, 10 ml/kg). Another two groups of LPS-treated rats were subjected to HBO(2) exposure after the injection of L-NAME or L-NIL.MEASUREMENTS AND MAIN RESULTS: The bronchoalveolar lavage (BAL) was done into the left lung at 7.5 h after intraperitoneal injection of LPS. Parts of the right lung were excised for myeloperoxidase measurement, whereas the rest was collected for wet/dry ratio determination. LPS significantly increased the nitrite/nitrate (NO(x)(-)) concentration (34.4+/-15.7 vs 4.5+/-3.1 microM), LDH activity (66+/-17 vs 46+/-15 mAbs/min), and protein concentration (373+/-119 vs 180+/-90 mg/l) in the BAL fluid. Treatment with HBO(2) immediately after the injection of LPS enhanced the increase of NO(x)(-) production, but reduced the LDH and protein in BAL fluid to the control levels. Pretreatment with either L-NAME or L-NIL abolished the increase of NO(x)(-) in the BAL fluid and further elevated the LDH level and protein concentration.CONCLUSION: Our results suggested that HBO(2) alleviates the LPS-induced acute lung injury, which may be related to the enhancement of nitric oxide production.     

Pulmonary Artery Pressure and Alveolar Gas Exchange in Man during Acclimatization to 12,470 ft

Pulmonary hemodynamics and gas exchange were studied in four physicians during 72 hr acclimatization to 12,470 ft. Pulmonary catheters were left in three subjects for 72 hr. Resting mean pulmonary arterial pressure (PAP) rose progressively during the first 24 hr from 10.3 +/-1.0 to 21.1 +/-4.0 torr and remained at this level. During this same 24 hr period cardiac output increased from 7.1 +/-1.4 to 8.4 +/-2.0 liters/min and total pulmonary resistance rose from 122 +/-16 to 209 +/-40 dynes.sec/cm(-5). Excercise at 60 w after 24 hr of hypoxia increased PAP to 28.8 +/-5.1 torr and decreased total pulmonary resistance to 155 +/-25. Shunt fractions were 11 +/-3.8% after 24 hr at altitude and fell to 7 +/-0% after 72 hr. Alveolar to arterial O(2) difference (P(A-a)(O2)) breathing oxygen fell from 116 +/-10.8 to 92 +/-33.3 torr during the same period of acclimatization, whereas dead space to tidal volume ratio (V(D)/V(T)) rose from 33 +/-4.0% to 40 +/-5.3% and P(A-a)(O2) breathing ambient air rose from 8 +/-2.6 to 11 +/-3.0 torr. Inspiratory static lung compliance decreased significantly from a control of 176 +/-8 to 141 +/-8 ml/cm H(2)O after 72 hr of hypoxia.After 4-7 days at altitude, further deterioration in gas exchange was observed after a 5 mile, 1800 ft climb to the summit (14,255 ft) and return. P(A-a)(O2) on air rose from 2.5 +/-2.1 just before starting, to 16.3 +/-2.8 at the summit (rested), and was still 9.0 +/-2.2 several hours after returning. The O(2)-breathing values paralleled these, whereas dead space appeared to fall. We speculate that the hypoxic pulmonary hypertension which develops over 24 hr in some way may be responsible for a reduction of compliance and deterioration in oxygen exchange efficiency, possibly representing a sub-clinical form of pulmonary edema of high altitude. The increased alveolar to arterial O(2) difference induced by hypoxic exercise persists for several hours of hypoxic rest.     

Protection of pirfenidone against an early phase of oleic acid-induced acute lung injury in rats

The potential role of PFD [5-methyl-L-phenyl-2-(1H)-pyridone], an antifibrotic compound with anti-inflammatory effects, in several models of acute lung injury (ALI) has gained increasing attention; however, the protective effect of PFD in oleic acid (OA)-induced ALI remains unknown. We hypothesized that PFD protects from OA-induced ALI in rats, and we hoped to obtain the optimum preclinical conditions with PFD in ALI. Sprague-Dawley rats were randomized into five groups (five rats per group): normal control group, OA-treated group (0.15 ml/kg), and three PFD-treated groups (20, 40, and 80 mg/kg p.o., respectively). Arterial blood gases, lung wet/dry weight ratio, and postmortem histological changes were determined 0.5, 1, 2, 6, and 24 h after OA challenge. Electron spin resonance spectroscopy was used for free radical detection and measurement. Experiments were examined based on the orthogonal test L4 (4(2)) setting two factors (PFD dose and PFD valid time) with four different levels. The results of the orthogonal test showed that the sequence of effect of PFD was 0.5 h (oxygen radicals), 1 h (histological changes), 2 h (lung edema), and 6 h (partial pressure of oxygen) after OA challenge, and 40 mg/kg PFD was the most effective dose in this study. We conclude that PFD protects against OA-induced ALI in rats. The mechanism of these protective effects partly involves decrease of oxygen radicals. The data of this study proves that the orthogonal test will be a powerful method to help obtain the optimum experimental conditions with PFD in ALI in the future.     

Aerosolized alpha-tocopherol ameliorates acute lung injury following combined burn and smoke inhalation injury in sheep

Victims of fire accidents who sustain both thermal injury to the skin and smoke inhalation have gross evidence of oxidant injury. Therefore, we hypothesized that delivery of vitamin E, an oxygen superoxide scavenger, directly into the airway would attenuate acute lung injury postburn and smoke inhalation. Sheep (N = 17 female, 35 +/- 5 kg) were divided into 3 groups: (1) injured, then nebulized with vitamin E (B&S, Vitamin E, n = 6); (2) injured, nebulized with saline (B&S, Saline, n = 6); and (3) not injured, not treated (Sham, n = 5). While under deep anesthesia with isoflurane, the sheep were subjected to a flame burn (40% total body surface area, 3rd degree) and inhalation injury (48 breaths of cotton smoke, <40 degrees C). All groups were resuscitated with Ringer lactate solution (4 mL/kg/%burn/24 h) and placed on a ventilator [positive end-expiratory pressure (PEEP) = 5 cm H2O, tidal volume = 15 mL/kg] for 48 h. B&S injury halved the lung alpha-tocopherol concentrations (0.9 +/- 0.1 nmol/g) compared with sham-injured animals (1.5 +/- 0.3), whereas vitamin E treatment elevated the lung alpha-tocopherol concentrations (7.40 +/- 2.61) in the injured animals. B&S injury decreased pulmonary gas exchange (PaO2/FiO2 ratios) from 517 +/- 15 at baseline to 329 +/- 49 at 24 h and to 149 +/- 32 at 48 h compared with sham ratios of 477 +/- 14, 536 +/- 48, and 609 +/- 49, respectively. Vitamin E treatment resulted in a significant improvement of pulmonary gas exchange; ratios were 415 +/- 34 and 283 +/- 42 at 24 and 48 h, respectively. Vitamin E nebulization therapy improved the clinical responses to burn and smoke inhalation-induced acute lung injury.     

大黄附子汤对重症急性胰腺炎肺损伤大鼠肺泡上皮屏障功能的影响

目的 探讨大黄附子汤对重症急性胰腺炎肺损伤大鼠肺上皮屏障功能的影响及意义.方法 96只SD大鼠随机分为假手术组、重症急性胰腺炎肺损伤组(SAP-ALI组)及大黄附子汤组三组,每组32只.各组再按3,6,12,24 h时间点分为四个亚组,每个亚组各8只.假手术组开腹后行空肠造瘘,翻动胰腺数次后关腹;SAP-ALI组在假手术组基础上经胰胆管逆行注入4%牛磺胆酸钠(1mL/kg),建立重症急性胰腺炎急性肺损伤模型;大黄附子汤组在SAP-ALI组基础上经空肠造瘘管注入大黄附子汤10 mL.各组按时间点分别于伤后3,6,12,24 h测定肺泡上皮通透性(AEP)、肺泡内液体清除率(ALCR)、总肺水量(TLW)和肺血管外肺水量(EVLW),同时测定血浆内毒素(ET)、血清淀粉酶含量,光镜下观察肺脏病理组织学变化.结果 与假手术组比较,SAP-ALI组大鼠术后3,6,12,24 h ALCR显著降低,TLW,EVLW及AEP呈明显升高趋势(P＜0.05或P＜0.01).与SAP-ALI组比较,大黄附子汤组对大鼠术后3,6,12,24 h ALCR均显著升高,TLW,EVLW及AEP呈明显降低趋势(P＜0.05或P＜0.01),且肺组织的水肿、出血、炎症程度及肺损伤学评分和肺湿/干重比均明显好转.结论 重症急性胰腺炎并急性肺损伤大鼠存在严重的肺泡上皮屏障功能障碍;大黄附子汤通过抑制内毒素过度释放,可降低炎症反应,改善肺泡上皮功能障碍,减轻肺损伤程度.

Abstract：

Objective To investigate effect of Dahuang Fuzi decoction on alveolaur epithelial barrier in rats with lung injury with severe acute pancreatitis. Method Ninty-six health SD rats were randomly divided into three groups: sham operation group, SAP-ALI group, Dahuang Fuzi decoction group, and then according to the time point of sacrifice after operation, each group was subdivided into 3,6,12,24 hour subsets ( each, n = 8). After the belly of a rat in the sham operation group was cut open, the pancreas was flipped several times,and then a stoma was made in the jejunum to form its fistula. In the SAP-ALl group,1 mL/kg sodium taurocholate was reversely injected into the pancreatobile duct to establish the model of SAP, and then the jejimum fistula was performed. The SAP-ALI model in Dahuang Fuzi decoction group was treated by injection of 10ml of Dahuang Fuzi decoctionon into the fistula respectively. Blood was collected from heart to detect serum amvlase and endotoxin (ET) levels before the rat being executed. The lung histopathologic changes, pulmonary injury scores and wet/dry weight(W/D) ratios were observed after the rats were executed. The alveolar liquid clearance rate(ALCR), total lung water content (TLW), extravascular lung water content(EVLW) and alveolar epithelial permeability (AEP) were examined in 3,6, 12,24 h after injury.Results There was continuous increase of AEP,TLW and EVLW,as well as progressive reduction of ALCR compared with sham operation group at 3,6,12,24 h after operation. Compared with SAP-ALI group, there was continuous decrease of AEP,TLW and EVLW, and elevated of ALCR at 3,6,12,24 h after operation.Conclusions Dahuang Fuzi decoction can significantly reduce alveolaur epithelial barrier and degree of lung tissue of SAP-ALI rats by inhibiting the elevation of LPS and inflammation reaction.