Osteopontin is associated with inflammation and mortality in a mouse model of polymicrobial sepsis.

BACKGROUND: Osteopontin (OPN) is a multifunctional glycoprotein with pro-inflammatory properties. In severe sepsis, levels of plasma OPN are significantly higher in non-survivors than in survivors. We hypothesized that OPN results in greater inflammation and worse outcome through modulation of endogenous glucocorticoid production in sepsis. METHODS AND RESULTS: Sepsis was induced by cecal ligation and puncture (CLP) in wild type (WT) and OPN gene knockout (OPN(-/-) ) mice. In response to sepsis, the OPN(-/-) mice had lower levels of plasma cytokines and chemokines than the WT mice. The levels of corticosterone in plasma were similar between WT and OPN(-/-) sham animals but they increased 24 h after CLP induction in the WT mice, but not in the OPN(-/-) mice. The mortality rate was lower in the OPN(-/-) mice than in the WT mice. CONCLUSION: OPN is associated with greater inflammatory response and increased mortality, despite the higher corticosterone levels in plasma. Corticosterone production is not impaired in the absence of OPN.

Additives in intravenous anesthesia modulate pulmonary inflammation in a model of LPS-induced respiratory distress.

BACKGROUND: It has been suggested that propofol with ethylenediaminetetraacetic acid (EDTA) can modulate the systemic inflammatory response. Prolonged higher levels of pulmonary inflammation are associated with poor outcome of patients with acute lung injury. In the present study, we hypothesized that pulmonary inflammation could be modulated by propofol with EDTA compared with propofol with sulfite. METHODS: Respiratory distress was induced in rats (n=25) by intratracheal nebulization of lipopolysaccharide (LPS). After 24 h, animals were randomized to either propofol with EDTA (Propofol(EDTA)), propofol with sulfite (Propofol(sulfite)) or ketamine/midazolam (Ket/Mid); control animals received saline (n=30). Animals were ventilated for 4 h and blood gases were measured hourly. Bronchoalveolar lavage (BAL) was performed for cytokine analysis of: tumor necrosis factor (TNF), interleukin (IL)-6 and macrophage inflammatory protein (MIP)-2. RESULTS: LPS led to increased pulmonary inflammation in all groups compared with the control groups. Gas exchange deteriorated over time only in the LPS Propofol(sulfite) group and was significantly lower than the Ket/Mid group. Only IL-6 was significantly higher in the LPS Propofol(sulfite) group compared with both the Ket/Mid group and the Propofol(EDTA) group. CONCLUSION: Pulmonary IL-6 can be modulated by additives in systemic anesthesia. IMPLICATION STATEMENT: This study demonstrates that pulmonary inflammation caused by direct lung injury can be modulated by intravenous anesthesia used in critically ill patients.

ACE mediates ventilator-induced lung injury in rats via angiotensin II but not bradykinin.

Ventilator-induced lung injury is characterised by inflammation and apoptosis, but the underlying mechanisms are poorly understood. The present study proposed a role for angiotensin-converting enzyme (ACE) via angiotensin II (Ang II) and/or bradykinin in acute lung injury. The authors assessed whether ACE and, if so, Ang II and/or bradykinin are implicated in inflammation and apoptosis by mechanical ventilation. Rats were ventilated for 4 h with low- or high-pressure amplitudes in the absence or presence of the ACE inhibitor captopril. Nonventilated animals served as controls. ACE activity, Ang II and bradykinin levels, as well as inflammatory parameters (total protein, macrophage inflammatory protein-2 and interleukin-6) were determined. Apoptosis was assessed by the number of activated caspase-3 and TUNEL (terminal deoxynucleotidyltransferase-mediated deoxyuridine triphosphate nick-end labelling)-positive cells. Bronchoalveolar lavage fluid ACE activity, levels of total protein, inflammatory parameters and the number of apoptotic cells were increased in the high-pressure amplitude group as compared with the control group. Blocking ACE activity by captopril attenuated inflammation and apoptosis in the latter group. Similar results were obtained by blocking Ang II receptors, but blocking bradykinin receptors did not attenuate the anti-inflammatory and anti-apoptotic effects of captopril. The current authors conclude that inflammation and apoptosis in ventilator-induced lung injury is, at least in part, due to angiotensin-converting enzyme-mediated angiotensin II production.

Ventilator-induced coagulopathy in experimental Streptococcus pneumoniae pneumonia.

Pneumonia, the main cause of acute lung injury, is characterised by a local pro-inflammatory response and coagulopathy. Mechanical ventilation (MV) is often required. However, MV can lead to additional injury: so-called ventilator-induced lung injury (VILI). Therefore, the current authors investigated the effect of VILI on alveolar fibrin turnover in Streptococcus pneumoniae pneumonia. Pneumonia was induced in rats, followed 48 h later by either lung-protective MV (lower tidal volumes (LV(T)) and positive end-expiratory pressure (PEEP)) or MV causing VILI (high tidal volumes (HV(T)) and zero end-expiratory pressure (ZEEP)) for 3 h. Nonventilated pneumonia rats and healthy rats served as controls. Thrombin-antithrombin complexes (TATc), as a measure for coagulation, and plasminogen activator activity, as a measure of fibrinolysis, were determined in bronchoalveolar lavage fluid (BALF) and serum. Pneumonia was characterised by local (BALF) activation of coagulation, resulting in elevated TATc levels and attenuation of fibrinolysis compared with healthy controls. LV(T)-PEEP did not influence alveolar coagulation or fibrinolysis. HV(T)-ZEEP did intensify the local procoagulant response: TATc levels rose significantly and levels of the main inhibitor of fibrinolysis, plasminogen activator inhibitor-1, increased significantly. HV(T)-ZEEP also resulted in systemic elevation of TATc compared with LV(T)-PEEP. Mechanical ventilation causing ventilator-induced lung injury increases pulmonary coagulopathy in an animal model of Streptococcus pneumoniae pneumonia and results in systemic coagulopathy.

Effects of PEEP levels following repeated recruitment maneuvers on ventilator-induced lung injury.

BACKGROUND: Different levels of positive end-expiratory pressure (PEEP) with and without a recruitment maneuver (RM) may have a significant impact on ventilator-induced lung injury but this issue has not been well addressed. METHODS: Anesthetized rats received hydrochloric acid (HCl, pH 1.5) aspiration, followed by mechanical ventilation with a tidal volume of 6 ml/kg. The animals were randomized into four groups of 10 each: (1) high PEEP at 6 cm H(2)O with an RM by applying peak airway pressure at 30 cm H(2)O for 10 s every 15 min; (2) low PEEP at 2 cm H(2)O with RM; (3) high PEEP alone; and (4) low PEEP alone. RESULTS: The mean arterial pressure and the amounts of fluid infused were similar in the four groups. Application of the higher PEEP improved oxygenation compared with the lower PEEP groups (P<0.05). The lung compliance was better reserved, and the systemic cytokine responses and lung wet to dry ratio were lower in the high PEEP than in the low PEEP group for a given RM (P<0.05). CONCLUSIONS: The use of a combination of periodic RM and the higher PEEP had an additive effect in improving oxygenation and pulmonary mechanics and attenuation of inflammation.

Surfactant as a carrier: influence of immunosuppressive agents on surfactant activity.

INTRODUCTION: It has been proposed that exogenous pulmonary surfactant can be used as a drug delivery system for immunosuppressive agents to the alveolar compartment of the lung while reducing the risk of systemic toxicity. Before using this combination, however, alterations in activity of both substances should be examined. Therefore, this study investigated whether the activity of a natural derived surfactant preparation is changed after it is mixed with cyclosporine A (CsA) or rapamycin (RPM). METHODS: A surfactant suspension was mixed with CsA or RPM and minimal surface tension of these mixtures was measured in vitro. Surfactant activity was evaluated in vivo by its capacity to restore gas exchange in an established model of surfactant deficiency in rats. CsA-surfactant, RPM-surfactant or surfactant alone was instilled intratracheally and blood gases were measured under standardized ventilatory conditions. RESULTS: Minimal surface tension of surfactant-CsA was comparable with that of surfactant alone, whereas minimal surface tension of the surfactant-RPM mixture was increased. In vivo partial arterial oxygen pressure levels increased immediately to prelavage values after instillation of CsA-surfactant, RPM-surfactant and surfactant only and were comparable during the entire study period. CONCLUSION: The activity of a naturally derived surfactant was affected when mixed with RPM but not when mixed with CsA at the used concentrations.

Liver-type fatty acid binding protein in serum and broncho-alveolar lavage in a model of acute respiratory failure because of surfactant depletion--a possible marker for lung damage?

INTRODUCTION: Liver-type fatty acid binding proteins (L-FABP) have been shown to be present in alveolar macrophages and type II pneumocytes of the lung. This study determined levels of L-FABP in serum and broncho-alveolar lavage (BAL) during experimental acute respiratory failure (ARF) to evaluate whether this molecule can serve as a marker for lung damage. METHODS: Male Sprague-Dawley rats (n = 24) were ventilated and either lung lavaged or lavaged and treated with surfactant, and compared to ventilated, non-lavaged controls. Blood samples were drawn every hour for 4 h to measure L-FABP concentrations in serum. At the end of the experiment a BAL was performed to determine L-FABP levels in BAL fluid. L-FABP was measured with a sandwich enzyme-linked immunosorbent assays. RESULTS: Serum L-FABP concentrations rose significantly during the first 2 h of ventilation in all groups compared with baseline values. After 2 h L-FABP levels were significantly higher in lavaged animals compared with the ventilated controls and to animals treated with surfactant. After 4 h of ventilation, L-FABP in BAL was significantly higher in lavaged, non-surfactant treated animals compared with the ventilated controls. CONCLUSION: In the early phase of experimental ARF serum L-FABP levels correlate well with the degree of lung injury.

Respiratory inductive plethysmography accuracy at varying PEEP levels and degrees of acute lung injury.

BACKGROUND AND OBJECTIVE: This study was performed to assess the accuracy of respiratory inductive plethysmographic (RIP) estimated lung volume changes at varying positive end-expiratory pressures (PEEP) during different degrees of acute respiratory failure. METHODS: Measurements of inspiratory tidal volume were validated in eight piglets during constant volume ventilation at incremental and decremental PEEP levels and with increasing severity of pulmonary injury. RIP accuracy was assessed with calibration from the healthy state, from the disease state as the measurement error was assessed, and at various PEEP levels. RESULTS: Best results (bias 3%, precision 7%) were obtained in healthy animals. RIP accuracy decreased with progressing degrees of acute respiratory failure and was PEEP dependent, unless RIP was calibrated again. When calibration was performed in the disease state as the measurement error was assessed, bias was reduced but precision did not improve (bias -2%, precision 9%). CONCLUSIONS: RIP accuracy is within the accuracy range found in monitoring devices currently in clinical use. Most reliable results with RIP are obtained when measurements are preceded by calibration in pulmonary conditions that are comparable to the measurement period. When RIP calibration is not possible, fixed weighting of the RIP signals with species and subject size adequate factors is an alternative. Measurement errors should be taken into account with interpretation of small volume changes.

Complement activation contributes to ventilator-induced lung injury in rats.

The complement system contributes to ventilator induced lung injury (VILI). We hypothesized that pretreatment with the C1 esterase inhibitor (C1INH) Berinert® constrains complement activation consecutively inducing improvements in arterial oxygenation and histological pulmonary damage. At baseline, male Sprague-Dawley rats underwent mechanical ventilation in a conventional mode (PIP 13 cm H2O, PEEP 3 cm H2O). In the Control group, the ventilator setting was maintained (Control, n = 15). The other animals randomly received intravenous pretreatment with either 100 units/kg of the C1-INH Berinert® (VILI-C1INH group, n = 15) or 1 ml saline solution (VILI-C group, n = 15). VILI was induced by invasive ventilation (PIP 35 cm H2O, PEEP 0 cm H2O). After two hours of mechanical ventilation, the complement component C3a remained low in the Control group (258 ± 82 ng/ml) but increased in both VILI groups (VILI-C: 1017 ± 283 ng/ml; VILIC1INH: 817 ± 293 ng/ml; P < 0.05 for both VILI groups versus Control). VILI caused a profound deterioration of arterial oxygen tension (VILI-C: 193 ± 167 mmHg; VILI/C1-INH: 154 ± 115 mmHg), whereas arterial oxygen tension remained unaltered in the Control group (569 ± 26 mmHg; P < 0.05 versus both VILI groups). Histological investigation revealed prominent overdistension and interstitial edema in both VILI groups compared to the Control group. C3a plasma level in the VILI group were inversely correlated with arterial oxygen tension (R = -0.734; P < 0.001). We conclude that in our animal model of VILI the complement system was activated in parallel with the impairment in arterial oxygenation and that pretreatment with 100 units/kg Berinert® did neither prevent systemic complement activation nor lung injury.

Influence of phosphatidylglycerol on the uptake of liposomes by alveolar cells and on lung function.

The effect of phosphatidylglycerol on the uptake of surfactant-like liposomes by alveolar type II cells and alveolar macrophages as well as the effect on endogenous surfactant function was studied in vivo. Healthy ventilated rats were intratracheally instilled with fluorescent labeled liposomes with different concentrations of phosphatidylglycerol. Lung function was determined by monitoring arterial oxygenation and, at the end of the experiment, by recording static pressure-volume curves. In addition, alveolar cells were isolated, and cell-associated fluorescence was determined using flow cytometry. The results show that, in the presence of cofactors (Ca(2+), Mg(2+)), phosphatidylglycerol stimulates the uptake by alveolar macrophages but hardly affects the uptake by alveolar type II cells. High concentrations of phosphatidylglycerol reduce the number of alveolar macrophages in the alveolar space and deteriorate lung function. On the other hand, the presence of cofactors protects the lung against the negative effects of phosphatidylglycerol on endogenous surfactant and alveolar macrophages. This study indicates that the phosphatidylglycerol concentration may play a fundamental role in the surfactant function and metabolism depending on the presence of so-called cofactors like calcium and magnesium; further study is needed to clarify the mechanisms involved.

Exogenous surfactant as a drug delivery agent.

Pulmonary surfactant is a complex mixture of lipids and several specific surfactant proteins, which together render it with unique spreading properties and a dynamic surface tension behavior. These characteristics are heralded as ideal for a carrier of choice to instil therapeutic agents into the lung, because this combination enables high local therapeutic levels while minimizing systemic side-effects of the instilled agent. This review outlines the rationale to use exogenous surfactant in lung injury, including opening-up inaccessible regions of the lung to other therapeutic agents. Especially the combination of anti-microbial agents and surfactant offers an alternative for critically ill patients with pneumonia. Some caution is also indicated in combining surfactant with antibiotics without proper evaluation of possible interactions. Some other applications for surfactant as a carrier are discussed. Overall, the benefits of surfactant as a carrier warrants clinical trials and promises additional therapeutic tools for the clinician.

Ventilator-induced lung injury leads to loss of alveolar and systemic compartmentalization of tumor necrosis factor-alpha.

OBJECTIVES: To determine the effect on compartmentalization of the tumor necrosis factor (TNF)-alpha response in the lung and systemically after ventilation with high peak inspiratory pressure with and without positive end-expiratory pressure (PEEP). DESIGN AND SETTING: Prospective, randomized, animal study in an experimental laboratory of a university. SUBJECTS AND INTERVENTIONS: 85 male Sprague-Dawley rats. Lipopolysaccharide was given intratracheally or intraperitoneally to stimulate TNF-alpha production; control animals received a similar amount of saline. Animals were subsequently ventilated for 20 min in a pressure control mode with peak inspiratory pressure/PEEP ratio of either 45/0 or 45/10 (frequency 30 bpm, I/E ratio 1:2, FIO2 = 1). MEASUREMENTS AND RESULTS: Blood gas tension and arterial pressures were recorded at 1, 10, and 20 min after start of mechanical ventilation. After killing of the animals pressure-volume curves were recorded, and bronchoalveolar lavage (BAL) was performed for assessment of protein content and the small/large surfactant aggregate ratio. TNF-alpha was determined in serum and BAL. TNF-alpha levels were significantly increased after lipopolysaccharide stimulation; furthermore ventilation without PEEP resulted in a significant shift of TNF-alpha to the nonstimulated compartment as opposed to ventilation with a PEEP level of 10 cmH2O. CONCLUSIONS: Ventilation strategies which are known to induce ventilation-induced lung injury (VILI) disturb the compartmentalization of the early cytokines response in the lung and systemically. Furthermore, the loss of compartmentalization is a two-way disturbance, with cytokines shifting from the vascular side to the alveolar side and vice versa. A ventilation strategy (PEEP level of 10 cmH2O) which prevents VILI significantly diminished this shift in cytokines.

Mechanical ventilation with positive end-expiratory pressure preserves arterial oxygenation during prolonged pneumoperitoneum.

BACKGROUND: Laparoscopic surgery usually requires a pneumoperitoneum by insufflating the abdominal cavity with carbon dioxide (CO2). Increased intraabdominal pressure causes diaphragmatic displacement resulting in compressed lung areas, which leads to formation of atelectasis, especially during mechanical ventilation. Application of positive end-expiratory pressure (PEEP) can maintain pulmonary gas exchange. The objective of this study was to investigate the effect of abdominal gas insufflation on arterial oxygenation during mechanical ventilation with and without PEEP in rats. METHODS: In experiment 1, two groups of six rats were continuously insufflated with CO2 at 12 mmHg for 180 min. Group 1 was ventilated with 8 cm H2O PEEP and group 2 had 0 cm H2O PEEP. Group 3 served as a control. This group had abdominal wall lifting and was ventilated with 0 cmH2O PEEP. In experiment 2, two groups of six rats had abdominal CO2 insufflation and were ventilated with or without PEEP during 180 min (group 4 and 5). In this experiment, abdomens were desufflated in both groups for 5 min at 60 and 120 min. Blood pressure monitoring and measurement of arterial pO2 was performed by placement of an indwelling carotid artery catheter in both experiments. RESULTS: In both experiments, paO2 values decreased significantly in insufflation groups that were ventilated with 0 cmH2O PEEP (groups 2 and 5). Insufflation groups ventilated with 8 cmH2O PEEP had paO2 values comparable to these of control group. There were no significant differences in mean arterial pressure between insufflation groups ventilated with or without PEEP. CONCLUSION: PEEP preserves arterial oxygenation during prolonged pneumoperitoneum in rats with minimal adverse hemodynamic effects.

Impact of carbon dioxide and helium insufflation on cardiorespiratory function during prolonged pneumoperitoneum in an experimental rat model.

BACKGROUND: Experimental studies on laparoscopic surgery are often performed in rats. However, the hemodynamic and respiratory responses related to the pneumoperitoneum have not been studied extensively in rats. Therefore, the aim of this study was to investigate in spontaneously breathing rats the effects of CO2 and helium, insufflation pressure, and duration of pneumoperitoneum on blood pressure, arterial pH, pCO2, pO2, HCO3-, base excess, and respiratory rate. METHODS: Five groups of 9 Brown Norway rats were anesthetized and underwent CO2 insufflation (6 or 12 mmHg), helium insufflation (6 or 12 mmHg), or abdominal wall lifting (gasless control) for 120 min. Blood pressure was monitored by an indwelling carotid artery catheter. Baseline measurements of mean arterial pressure (MAP), respiratory rate, arterial blood pH, pCO2, pO2, HCO3-, and base excess were recorded. Blood gases were analyzed at 5, 30, 60, 90, and 120 min during pneumoperitoneum, and MAP and respiratory rate were recorded at 5 and 15 min and at 15-min intervals thereafter for 2 h. RESULTS: CO2 insufflation (at both 6 and 12 mmHg) caused a significant decrease in blood pH and increase in arterial pCO2. Respiratory compensation was evident since pCO2 returned to preinsufflation levels during CO2 insufflation at 12 mmHg. There was no significant change in blood pH and pCO2 in rats undergoing either helium insufflation or gasless procedures. Neither insufflation pressure nor the type of insufflation gas had a significant effect on MAP over time. CONCLUSION: The cardiorespiratory changes during prolonged pneumoperitoneum in spontaneously breathing rats are similar to those seen in clinical practice. Therefore, studies conducted in this animal model can provide valuable physiological data relevant to the study of laparoscopic surgery.

Brain glucose and lactate levels during ventilator-induced hypo- and hypercapnia.

OBJECTIVE: Levels of glucose and lactate were measured in the brain by means of microdialysis in order to evaluate the effects of ventilator-induced hypocapnia and hypercapnia on brain metabolism in healthy non-brain-traumatized animals. DESIGN AND SETTING: Prospective animal study in a university laboratory. SUBJECTS: Eight adult Landrace/Yorkshire pigs. INTERVENTIONS: The microdialysis probe was inserted in the brain along with a multiparameter sensor and intracranial pressure (ICP) probe. The animals were ventilated in a pressure-controlled mode according to the open lung concept with an inspired oxygen fraction of 0.4/1.0. Starting at normoventilation (PaCO(2) +/-40 mmHg) two steps of both hypercapnia (PCO(2) +/- 70 and 100 mmHg) and hypocapnia (PaCO(2) +/- 20 and 30 mmHg) were performed. Under these conditions, brain glucose and lactate levels as well as brain oxygen (PbrO(2)), brain carbon dioxide (PbrCO(2)), brain pH (brpH), brain temperature and ICP were measured. RESULTS: At hypercapnia (PaCO(2) = 102.7 mmHg) there were no significant changes in brain glucose and lactate but there was a significant increase in PbrCO(2), PbrO(2) and ICP. In contrast, at hypocapnia (PCO(2) = 19.8 mmHg) there was a significant increase in brain lactate and a significant decrease in both brain glucose and PbrCO(2). CONCLUSIONS: Hypocapnia decreases brain glucose and increases brain lactate concentration, indicating anaerobic metabolism, whereas hypercapnia has no influence on levels of brain glucose and brain lactate.

Lung protective ventilation in ARDS: role of mediators, PEEP and surfactant.

Lung protective ventilation such as the ARDSnet low tidal volumes strategy can reduce mortality in ARDS patients. The knowledge that an essential therapy such as mechanical ventilation on the intensive care influences patient outcome has given rise to the re-evaluation of current ventilation practices. This review addresses the current state of lung protective strategies and their physiological rationale. Latest knowledge on the instigation and progression of lung injury by mechanical ventilation is explored, particularly the interaction between ventilation and the inflammatory response occurring in an ARDS lung. Furthermore, the role of tidal volume, PEEP, recruitment manoeuvres and surfactant on lung injury is discussed. Finally, we discuss results from clinical studies on mechanical ventilation and elucidate these results with data acquired in experimental studies. Guidelines for future strategies and/or investigations are presented.

Plasma-derived human antithrombin attenuates ventilator-induced coagulopathy but not inflammation in a Streptococcus pneumoniae pneumonia model in rats.

BACKGROUND: Mechanical ventilation exaggerates pneumonia-associated pulmonary coagulopathy and inflammation. We hypothesized that the administration of plasma-derived human antithrombin (AT), one of the natural inhibitors of coagulation, prevents ventilator-induced pulmonary coagulopathy, inflammation and bacterial outgrowth in a Streptococcus pneumoniae pneumonia model in rats. METHODS: Forty-eight hours after induction of S. pneumoniae pneumonia rats were subjected to mechanical ventilation (tidal volume 12 mL kg(-1), positive end-expiratory pressure 0 cmH(2)O and inspired oxygen fraction 40%). Rats were randomized to systemic treatment with AT (250 IU administered intravenously (i.v.) before the start of mechanical ventilation) or placebo (saline). Non-ventilated, non-infected rats and non-ventilated rats with pneumonia served as controls. The primary endpoints were pulmonary coagulation and inflammation in bronchoalveolar lavage fluid (BALF). RESULTS: Pneumonia was characterized by local activation of coagulation and inhibition of fibrinolysis, resulting in increased levels of fibrin degradation products and fibrin deposition in the lung. Mechanical ventilation exaggerated pulmonary coagulopathy and inflammation. Systemic administration of AT led to supra-normal BALF levels of AT and decreased ventilator-associated activation of coagulation. AT neither affected pulmonary inflammation nor bacterial outgrowth from the lungs or blood. CONCLUSIONS: Plasma-derived human AT attenuates ventilator-induced coagulopathy, but not inflammation and bacterial outgrowth in a S. pneumoniae pneumonia model in rats.

Effect of SP-B peptides on the uptake of liposomes by alveolar cells.

BACKGROUND: Exogenous surfactant has been accepted worldwide as a therapy of RDS in premature and term infants. Exogenous surfactant is usually derived from lung extracts containing phospholipids and the surfactant proteins SP-B and SP-C. Synthetic peptides of SP-B and SP-C are being tested with the aim to develop a completely synthetic surfactant preparation. Nevertheless, the effects of these peptides on the endogenous surfactant metabolism remain unknown. OBJECTIVES: The effect of synthetic SP-B peptides on uptake of surfactant-like liposomes was investigated in alveolar cells. Native SP-B and seven SP-B peptides were included: monomeric and dimeric SP-B(1-25) (Cys-11 --> Ala-11), SP-B(63-78)and Ala-SP-B(63-78) (Cys-71 --> Ala-71;Cys-77 --> Ala-77)and their serine mutants. METHODS: In vitro, alveolar macrophages (AM) and alveolar type II cells (ATII) were incubated with liposomes containing SP-B or one of its peptides. In vivo, rats received intratracheally various SP-B peptides (SP-B/lipid ratio 1:33 w/w) incorporated in fluorescent surfactant-like liposomes. One hour after instillation, AM and ATII were isolated and cell-associated fluorescence was determined using flow cytometry. Confocal laser microscopy was performed to ensure internalization of the liposomes. RESULTS: In vitro uptake by AM or ATII was not influenced by the SP-B peptides. In vivo, SP-B(1-25) and Ser-SP-B(1-25) increased the uptake by AM whereas dSP-B(1-25) decreased the uptake. Neither SP-B(1-25) nor dSP-B(1-25 )affected total uptake by ATII. The overall uptake by SP-B(63-78) variants was not changed. CONCLUSIONS: Surface-active synthetic SP-B peptides do not interfere with the normal uptake of surfactant by ATII.

Lung protective ventilation in ARDS: the open lung maneuver.

This review addresses the current state of lung protective strategies and their physiological rationale. Lung protective ventilation can reduce mortality in adult respiratory distress syndrome (ARDS) patients. We review the latest knowledge on the progression of lung injury by mechanical ventilation. Results from clinical studies on mechanical ventilation are compared with results obtained in experimental studies. Furthermore, we discuss possible future improvements to mechanical ventilation; especially the open lung maneuver. The rationale behind the open lung maneuver and steps to accomplish an open lung are described, as well as data from animal and human studies. Finally, guidelines for future strategies and/or investigations are presented.

Small-dose perfluorocarbon reduces the recruitment pressure needed to open surfactant-deficient atelectatic lungs.

BACKGROUND: This study was undertaken to investigate the effect of a small dose of perfluorocarbon on the recruitment pressure needed to open atelectatic lung areas. METHODS: In 12 Yorkshire pigs (body weight, 9 kg), lung injury was induced by whole lung lavage. After 1 h of conventional ventilation, an open lung maneuver was performed to obtain PaO2 values equal to the pre-lavage PaO2 values (+/-10%). After 1 h of ventilation at the lowest possible airway pressure that stabilized the recruited lung volume, the animals were disconnected from the ventilator to allow the lung to collapse. Six animals received a 5 ml/kg intratracheal dose of perfluorocarbon and a second open lung maneuver was performed. Six animals served as controls and received no perfluorocarbon but also underwent a second open lung maneuver. RESULTS: In both groups, an open lung maneuver resulted in a significant increase in oxygenation. The peak pressures needed to open the lung after 1 h of mechanical ventilation in the perfluorocarbon and control groups were 43.8 +/- 8.4 cmH2O and 46.6 +/- 4 cmH2O, respectively. The addition of perfluorocarbon significantly reduced the opening pressure to 34.5 +/- 6.3 cmH2O (P < 0.01), whereas the opening pressure in the control group, 45.0 +/- 0.2 cmH2O, did not change. CONCLUSION: The instillation of a small amount of perfluorocarbon significantly reduces the opening pressures needed to recruit atelectatic lung areas.