Low PEEP Research Articles

Cardiac effects of positive pressure ventilation in ARDS assessed by NT-proBNP, Troponin T and Troponin I

IntroductionPositive pressure ventilation may potentially affect the heart in ARDS patients with structurally normal hearts and maybe correlated with respiratory parameters. AimWe aimed at observing NT-proBNP, Troponin I and Troponin T levels in relation to respiratory parameters and positive pressure ventilation during the first week of ARDS (day 0, 2, 7). Patients and methodsThe study comprised 20 patients with mean age of 58.9 ± 20.69 years, 11 men vs. 9 women (p > 0.05). Inclusion criteria were any adult patient diagnosed to have ARDS according to the criteria of the American–European Consensus Conference in 1994. Exclusion criteria were any structural heart disease by echo, pulmonary embolism, atrial fibrillation, renal insufficiency, age less than 18. All patients were placed on a lung protective ventilation strategy. Plasma NT-proBNP, Troponin I and Troponin T were measured on day 0 and on day 2 and day 7 of ARDS diagnosis. PH, PaCO2, PaO2, PaO2/FiO2 ratio, PEEP, PIP (peak airway pressure), Pmean, Pplat (plateau pressure) and Ceff (effective compliance), RaW (airway resistance) were monitored daily. ResultsNT-proBNP was negatively correlated with PH on day 2 (p 0.008, r −0.53) and day 7 with (p 0.02, r −0.50). NT-proBNP was positively correlated with PEEP on day 2 (p 0.05, r 0.46) and day 7 (p 0.035, r 0.48). NT-proBNP was negatively correlated with PaO2/FiO2 ratio on day 7 (p 0.0035, r 0.60). However, there was no significant correlation between NT-proBNP and other respiratory indices including PaCO2, HCO3, PaO2, SaO2, FiO2 (p > 0.05). Neither Troponin I nor Troponin T showed any significant correlation with any respiratory indices PH, PEEP, PaO2/FiO2, PaCO2, HCO3, PaO2, SaO2, FiO2 at any day (p > 0.05). None of the cardiac markers NT-proBNPP, Troponin I or Troponin T showed any significant correlation with lung mechanics parameters Cdyn, RaW, Ceff, PIP, Pplat, Pmean (p > 0.05). ConclusionsIn patients with ARDS positive pressure ventilation may adversely affect the heart as reflected by elevations of NT-proBNP. High NT-proBNP level was correlated with high PEEP, low PH and low PaO2/FiO2 ratio while Trop T and Trop I did not show significant correlations with respiratory parameters. None of the cardiac markers NT-proBNP, Troponin I or Troponin T showed any significant correlation with lung mechanics parameters (Cdyn, RaW, Ceff, PIP, Pplat, Pmean, p > 0.05) in ARDS patients with structurally normal hearts.Although the increase in cardiac markers are insignificant, yet they point to the potentially harmful role played by high PEEP, low PH and low PaO2/FiO2 ratio on the heart. Currently, no clinically relevant conclusion can be drawn apart from the recommendation to attempt to lower PEEP and shorten the duration of positive pressure ventilation, even in patients with structurally normal hearts.

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Introduction: Alveoli in the acutely injured lungs may repetitively collapse and expand at expiration having a negative impact on ventilation/perfusion match. Hypothesis: Low tidal ventilation with PEEP optimized to maintain the end-expiratory transpulmonary pressure?0 cmH2O will improve oxygenation and shunt fraction, as compared to strategies that may allow for negative expiratory transpulmonary pressures. Methods: Ten Yorkshire pigs were instrumented and mechanically ventilated using transpulmonary pressure measurements. Baseline lung mechanics were obtained for the following parameters: Vt=10mL/kg, PEEP=5cmH2O, and FiO2 = 0. 21. Lungs were injured by instilling 5% Tween-20 (3ml/kg), and ARDS was established when PF ratios fell <200. After a single recruitment maneuver (40 cmH2O x 40sec.), the animals were randomized into a PtpPEEP Group with PEEP adjusted to maintain the end-expiratory transpulmonary pressure?0 cmH2O, or the Control Group where PEEP was adjusted based on the lower PEEP scale as per ARDSNet guidelines. Cardiovascular and respiratory parameters were recorded hourly for 24hr. Results: After 12hr, the PtpPEEP Group started separating from the Control Group, maintaining, as per protocol, PtpPEEP pressures?0 cmH2O, while the Control Group showed negative values 48% of time. Overall, the PtpPEEP Group had an odds ratio of 4.3 for normal oxygenation (PF ratio>300), and intrapulmonary shunting significantly lower than the Control Group (p<0.01). Regression analysis showed that shunt fractions increased with time (p<0.01) associated with decreasing PF ratios (<0.01); however, for the same PF ratios, the PtpPEEP Group showed lower shunt fractions than the Control (p<0.01). Conclusions: In our study, the extent of shunting was a consequence of the PEEP optimization strategy. The PtpPEEP Group improved the oxygenation and shunt fractions, indicating that maintaining a PtpPEEP?0 cmH2O may have a significant impact on ventilation/perfusion matching.

The Effect of Alveolar Dead Space on the Measurement of End-Expiratory Lung Volume by Modified Nitrogen Wash-Out/Wash-In in Lavage-Induced Lung Injury

The accuracy of end-expiratory lung volume measurement by the modified nitrogen wash-out/wash-in method (EELV-N(2)) depends on the precise determination of carbon dioxide elimination (V(CO(2))), which is affected by alveolar dead space (V(D-alv)). The purpose of this study was to investigate the influence of V(D-alv) on EELV-N(2). Six piglets with lavage-induced acute lung injury were mechanically ventilated in a decremental PEEP trial that was reduced from 20 to 4 cm H(2)O in steps of 4 cm H(2)O every 10 min. EELV was measured by the modified EELV-N(2) method and computed tomography scan (EELV-CT), volumetric capnography, blood gas measurements, and hemodynamic data were recorded at each PEEP level. The data were divided into higher and lower PEEP groups. During the decremental PEEP trial, EELV-N(2) exhibited a high correlation (r(2) = 0.86, P < .001) with EELV-CT, with a bias of -48.6 ± 150.7 mL (1 ± 18%). In the higher PEEP group, EELV-N(2) was not correlated with EELV-CT, with a bias of -168.1 ± 171.5 mL (-14 ± 14%). However, in the lower PEEP group, EELV-N(2) exhibited a high correlation (r(2) = 0.86, P < .001) with EELV-CT, with a bias of 11.2 ± 97.2 mL (6 ± 17%). The measurement bias was negatively correlated with V(D-alv) (r(2) = 0.44, P = .04) and V(CO(2)) (r(2) = 0.47, P = .03) in the higher PEEP group. In this surfactant-depleted model, EELV measurement by the modified EELV-N(2) method reveals a systematic underestimation at high PEEP levels that is partly due to an increase in V(D-alv).

Outcome of Adults Acute Lung Injury in High vs Low Positive End-Expiratory Pressure: Systematic Review

Background: Studies contrasting higher and lower PEEP in individuals with ALI have not been sufficiently powered to examine differences or identify subtle but potentially significant impacts on mortality. Our objective was to evaluate the association between high versus low PEEP and patient-important outcomes in individuals with ALI receiving low TVs ventilation. Method: The PRISMA statement was followed in the course of this systematic review investigation. Randomized trials that qualified for this review examined higher and lower PEEP levels in critically ill patients diagnosed with ALI. To locate relevant trials, we performed an electronic search of MEDLINE, Cochrane, and EMBASE (all from 2000 to 2011). We only included English-language randomized controlled trials. Results: Four trials yielded 2394 patients met our eligibility criteria. In the Assessment of Low TV and Elevated End-Expiratory Pressure to ALI and the Lung Open Ventilation to Reduce Mortality in the ARDS, PEEP levels were titrated to oxygenation using equivalent PEEP to FIO2 charts. The Expiratory Pressure Study's experimental strategy titrated PEEP levels based on plateau pressure data, regardless of the effect on oxygenation. Conclusion: Higher PEEP levels associated with a lower hospital death rate in patients with ARDS. Additionally, our findings suggest that this is unlikely to be beneficial for patients with less severe lung injuries; in fact, treating these patients with high PEEP levels may be harmful.

Optimal Method for Selecting Peep Level in Ali/Ards Patients under Mechanical Ventilation

The PEEP in ALI/ARDS had been used since its' description (1967). Up-to-date no optimal approach to PEEP setting had been introduced, however common approaches that had been introduced included Pressure volume curves, increasing PEEP trial, decreasing PEEP trial & PEEP/FiO2 tables adopted by ARDS network. The present work assessed the safety and efficacy of three introduced approaches for PEEP setting namely increasing PEEP trial, decreasing PEEP trial and PEEP/FiO2 table. Sixty patients fulfilling the American-European Consensus Conference (AECC) criteria for ALI/ARDS were enrolled in this study, patients were randomly allocated into three equal groups (n = 20) 1, 2 & 3 using closed envelope technique. In GA: patients received an increasing PEEP trial, GB: patients received a decreasing PEEP trial and GC: PEEP was set according to PEEP/FiO2 tables of the ARDS network trial. Hemodynamic parameters (mean arterial blood pressure (MAP) and heart rate (Hr) were recorded. Respiratory & oxygenation parameters (peak airway pressure (Paw), plateau pressure (Pplat), mean airway pressure (Pmean), PEEP, PaO2, PaO2/FiO2 and arterial oxygen saturation (Sao2) were also recorded at eight specific times, prior to randomization (baseline), following PEEP setting and twice daily for 72 hours. Both increasing and decreasing PEEP trials were considered superior to PEEP/FiO2 tables in identifying desired PEEP level. Although increasing and decreasing PEEP trials had demonstrated increased PaO2, and decreased FiO2 and better PaO2/FiO2 ratios compared to baseline values, however increasing PEEP trial was associated with lower Paw and Pplat due to lower PEEP values compared to decreasing PEEP trial. Decremental trial was associated with best PaO2, FiO2, and PaOz/FiO2 compared to increasing PEEP trial and PEEP/FiO2 tables.

Differential pulmonary and circulatory effects of preventive lung protective ventilation in an experimental postoperative sepsis model

It has been proposed that low tidal volume (VT) ventilation combined with higher PEEP should be used in patients with risk of developing postoperative lung injury instead of the commonly used VT of 10 ml/kg with lower PEEP [1]. Such a ventilatory mode would in theory reduce postoperative lung and organ dysfunction. However, this hypothesis has neither been tested clinically nor experimentally. Therefore we developed an experimental endotoxemic postoperative sepsis model to evaluate the effect of different modes of ventilation.

Effects of mechanical ventilation on cell apoptosis in lung tissue of rat with acute lung injury

Objective To investigate the effects of different tidal volumes and positive end expiratory pressures on cell apoptosis in lung tissue of rats with acute lung injury.Methods Forty healthy male Sprague-Dawley rats were randomly(random number)divided into five groups,namely low tidal volume group(LV,VT 8 mL/kg),high tidal volume group(HV,VT 30 mL/kg),low tidal volume group with PEEP 2cmH2O(LV2P,VT 8 mL/kg,PEEP 2 cmH2O),low tidal volume group and PEEP 5cmH2O (LV5P,VT 8 mL/kg,PEEP 5 cmH2O)and low tidal volume group and PEEP 8 cmH2O(LV8P,VT 8 mL/kg,PEEP 8 cmH2O).After intravenous administration of oleic acid(OA,0.1 mL/kg),the rat model of acute lung injury was made.Mechanical ventilation was employed in rats of the experiment groups.Rats were sacrificed and their whole lungs were taken after mechanical ventilation for 2 hours.The transferase d-UTP end labeling assay(TUNEL)was used to define the extent and distribution of apoptotic cells in bronchus and lung tissues.The level of caspase-3 protein was determined by immunohistochemistry.Results The apoptotic cells on both alveolar septum and bronchial epithelium obviously increased with high level of caaspase-3 protein in HV group.The number of apoptotic cells obviously decreased with decrease in caspase-3 protein after PEEP ventilation.These changes were more significant in LV5P than those in other groups(P ＜ 0.01).Conclusions The mechanical ventilation with low tidal volume and PEEP produces protective effects on lung from injury.The cell apoptosis plays an important role in the course of VILI. Key words: Acute lung injury; Ventilation; Apoptosis; Caspase-3 protein

Approaches to Conventional Mechanical Ventilation of the Patient With Acute Respiratory Distress Syndrome

To minimize ventilator-induced lung injury, attention should be directed toward avoidance of alveolar over-distention and cyclical opening and closure of alveoli. The most impressive study of mechanical ventilation to date is the Acute Respiratory Distress Syndrome (ARDS) Network study of higher versus lower tidal volume (V(T)), which reported a reduction in mortality from 39.8% to 31.0% with 6 mL/kg ideal body weight rather than 12 mL/kg ideal body weight (number-needed-to-treat of 12 patients). To achieve optimal lung protection, the lowest plateau pressure and V(T) possible should be selected. What is most important is limitation of V(T) and alveolar distending pressure, regardless of the mode set on the ventilator. Accumulating observational evidence suggests that V(T) should be limited in all mechanically ventilated patients-even those who do not have ALI/ARDS. Evidence does not support the use of pressure controlled inverse-ratio ventilation. Although zero PEEP is probably injurious, an area of considerable controversy is the optimal setting of PEEP. Available evidence does not support the use of higher PEEP, compared to lower PEEP, in unselected patients with acute lung injury (ALI)/ARDS. However, results of a meta-analysis using individual patients from 3 randomized controlled trials suggest that higher PEEP should be used for ARDS, whereas lower PEEP may be more appropriate in patients with ALI. PEEP should be set to maximize alveolar recruitment while avoiding over-distention. Many approaches for setting PEEP have been described, but evidence is lacking that any one approach is superior to any other. In most, if not all, cases of ALI/ARDS, conventional ventilation strategies can be used effectively to provide lung-protective ventilation strategies.

Clinical Year in Review III:: Mechanical Ventilation, Acute Respiratory Distress Syndrome, Nonpulmonary Intensive Care Unit, and Quality Performance Assessment Metrics in Your Practice

18.6%; RR, 0.64; 95% CI, 0.54‐0.75; P , 0.001), and moreover, the rate of death after rescue therapies was significantly lower (7.5 vs. 11.3%; RR, 0.65; 95% CI, 0.52‐0.80; P , 0.001) (3). In patients with ARDS, there was an insignificant increase in risk of pneumothorax with higher PEEP (RR, 1.23; 95% CI, 0.94‐1.68; P ¼ 0.13), and no difference in fatal consequences from barotrauma (RR, 1.2; 95% CI, 0.79‐1.81; P ¼ 0.39) (3). The use of neuromuscular blockers, corticosteroids, and vasopressors was similar between groups treated with higher and lower PEEP. In summary, this analysis suggests that higher PEEP is safe in patients with ARDS and may reduce the need for performing rescue therapies. Further, low to moderate levels of PEEP should be used for most patients with ALI.

P-76 Effects of different tidal volumes and positive end-expiratory pressure during one lung ventilation of normal lungs

The goal of one lung ventilation (OLV) management is prevention of arterial hypoxaemia. There have been debates regarding tidal volumes for prevents hypoxaemia and lung injury during OLV. We investigated the effects of ventilation using different tidal volumes with or without low PEEP on airway mechanics and oxygenation during OLV.

Higher PEEP in Patients With Acute Lung Injury: A Systematic Review and Meta-Analysis

Studies of ventilation strategies that included higher PEEP in patients with acute lung injury (ALI) or acute respiratory distress syndrome (ARDS) have yielded conflicting results. To determine whether higher PEEP during volume-limited and pressure-limited ventilation is associated with 28-day mortality or barotrauma rates in patients with ALI/ARDS. We searched MEDLINE, CENTRAL, EMBASE, CINAHL, Web of Science, and the bibliographies of retrieved papers to identify randomized controlled trials that compared higher and lower PEEP in adult patients with ALI/ARDS who were already receiving volume-limited or pressure-limited ventilation. Two of us independently abstracted study-level data, including study design, patient characteristics, study methods, intervention, and main results. We pooled the study-level data with a random-effects model, unless heterogeneity was low (I(2) < 50%), in which case we used a fixed-effects model. The primary outcome was 28-day mortality. Four randomized trials (2,360 participants) were evaluated. Higher PEEP had a nonsignificant trend toward lower 28-day mortality (pooled relative risk 0.90, 95% CI 0.79-1.02). There was no difference in barotrauma between the 2 groups (pooled relative risk 1.17, 95% CI 0.90-1.52). Two studies reported an adjusted hospital death rate, and the pooled results of sensitivity analysis with those adjusted rates were identical to those of the unadjusted analysis. In 4 recent studies that used volume-limited or pressure-limited ventilation in ALI/ARDS patients, higher PEEP was not associated with significantly different short-term mortality or barotrauma. This study does not support the routine use of higher PEEP in patients with ALI/ARDS.

Heart–lung interactions with different ventilatory settings during acute lung injury and hypovolaemia: an experimental study

BackgroundThe functional haemodynamic variables pulse pressure variation (PPV), stroke volume variation (SVV), and systolic pressure variation (SPV) are widely used to assess haemodynamic status. However, it is not known how these perform during acute lung injury (ALI). This study evaluated the effects of different ventilatory strategies on haemodynamic parameters in pigs with ALI during normovolaemia and hypovolaemia. MethodsEight anaesthetized Agroceres pigs [40 (1.9) kg] were instrumented with pulmonary artery, PiCCO, and arterial catheters and ventilated. Three ventilatory settings were randomly assigned for 10 min each: tidal volume (VT) 15 ml kg−1 and PEEP 5 cm H2O, VT 8 ml kg−1 and PEEP 13 cm H2O, or VT 6 ml kg−1 and PEEP 13 cm H2O. Data were collected at each setting at baseline, after ALI (lung lavage+Tween 1.5%), and ALI with hypovolaemia (haemorrhage to 30% of estimated blood volume). ResultsAt baseline, high VT increased PPV, SVV, and SPV (P<0.05 for all). During ALI, high VT significantly increased PPV and SVV [(P = 0.002 and P = 0.008) respectively.]. After ALI with hypovolaemia, ventilation at VT 6 ml kg−1 and PEEP 13 cm H2O decreased the accuracy of functional haemodynamic variables to predict hypovolaemia, with the exception of PPV (area under the curve 0.875). The parameters obtained by PiCCO were less influenced by ventilatory changes. ConclusionsVT is the ventilatory parameter which influences functional haemodynamics the most. During ventilation with low VT and high PEEP, most functional variables are less able to accurately predict hypovolaemia secondary to haemorrhage, with the exception of PPV.

Analysis of Dynamic Intratidal Compliance in a Lung Collapse Model

For mechanical ventilation to be lung-protective, an accepted suggestion is to place the tidal volume (V(T)) between the lower and upper inflection point of the airway pressure-volume relation. The drawback of this approach is, however, that the pressure-volume relation is assessed under quasistatic, no-flow conditions, which the lungs never experience during ventilation. Intratidal nonlinearity must be assessed under real (i.e., dynamic) conditions. With the dynamic gliding-SLICE technique that generates a high-resolution description of intratidal mechanics, the current study analyzed the profile of the compliance of the respiratory system (C(RS)). In 12 anesthetized piglets with lung collapse, the pressure-volume relation was acquired at different levels of positive end-expiratory pressure (PEEP: 0, 5, 10, and 15 cm H(2)O). Lung collapse was assessed by computed tomography and the intratidal course of C(RS) using the gliding-SLICE method. Depending on PEEP, C(RS) showed characteristic profiles. With low PEEP, C(RS) increased up to 20% above the compliance at early inspiration, suggesting intratidal recruitment; whereas a profile of decreasing C(RS), signaling overdistension, occurred with V(T) > 5 ml/kg and high PEEP levels. At the highest volume range, C(RS) was up to 60% less than the maximum. With PEEP 10 cm H(2)O, C(RS) was high and did not decrease before 5 ml/kg V(T) was delivered. The profile of dynamic C(RS) reflects nonlinear intratidal mechanics of the respiratory system. The SLICE analysis has the potential to detect intratidal recruitment and overdistension. This might help in finding a combination of PEEP and V(T) level that is protective from a lung-mechanics perspective.

S107 Comparison of high-stretch versus atelectasis in the pathophysiology of ventilator-induced lung injury using the mouse isolated perfused lung

IntroductionMechanical ventilation promotes pulmonary inflammation and oedema formation, a process known as ventilator-induced lung injury (VILI). Various aspects of ventilation have been proposed as injurious, including over distension of alveoli...

Positive end-expiratory pressure

In the last 2 years, several reports have dealt with recruitment/positive end-expiratory pressure (PEEP) selection. Most of them confirm previous results and few add new information. It has been definitely confirmed that opening pressures are different throughout the acute respiratory distress syndrome lung parenchyma, ranging from 5-10 up to 30-40 cmH2O. The highest opening pressures are required to open the most dependent lung regions. It has been found that in 2 s, most of the recruitable lung regions may be open when a proper pressure is applied. The best way to assess recruitment is computed tomography scanning, whereas lung mechanics are a reasonable bedside surrogate. Impedance tomography has been increasingly tested, whereas gas exchange is the less reliable indicator of recruitment. A large outcome study showed that higher PEEP might provide survival benefit in a subgroup of more severe patients as compared with lower PEEP. To set PEEP in each individual patient, the use of the expiratory limb of the pressure-volume curve has been suggested. Setting PEEP according to transpulmonary pressure has a robust physiological background, although it requires confirmatory study. Indiscriminate application of recruitment maneuver in unselected acute respiratory distress syndrome population does not provide benefits. However, in the most severe patients, recruitment maneuver has to be considered and higher PEEP applied. To individualize PEEP, the expiratory phase has to be considered, and the esophageal pressure measurement to compute the transpulmonary pressure should be progressively introduced in clinical practice.

Conventional mechanical ventilation can injury intact lungs in severe trauma patients

Conventional mechanical ventilation (MV) may cause additional lung injury in ALI/ARDS due to overdistention of aerated lung regions (high Vt) and cyclic lung reopening (low PEEP level). Hyperproduction of inflammatory mediators is one of the side effects in these cases. This factor could delay or prevent resolution of respiratory failure [1,2]. However, it is not clear whether conventional mechanical ventilation damages intact lungs. The aim of this study was to evaluate the effects of conventional and protective mechanical ventilation on intact lungs in patients with severe trauma.

Tracheal rupture post-emergency intubation

Tracheal rupture is an uncommon and potentially lifethreatening complication of endotracheal intubation. We present a case of intrathoracic tracheal rupture in a female patient who required emergent endotracheal intubation for acute respiratory distress related to chronic obstructive pulmonary disease exacerbation. Possible contributing factors to tracheal injury included overinflation of the tube cuff, chronic obstructive pulmonary disease, and chronic steroid use. The patient underwent surgical repair without complication. Postoperatively, the tube cuff was placed far distally, close to the carina, and mechanical ventilation was performed using low tidal volume and PEEP in order to avoid high ventilatory pressures.

Akutes Lungenversagen - Therapeutische Optionen im Überblick

The treatment of acute lung injury is one of the most challenging tasks in intensive care medicine. Conventional therapeutic options cover lung protective mechanical ventilation with low tidal volumes and adequate PEEP, restrictive fluid management, prone positioning, and early recruitment maneuvers. These options should be used in parallel and should be accompanied by a suitable anti-infective therapy. In cases of refractory hypoxemia, inhaled nitric oxide offers in most patients a successful rescue option. In specialized centers the application of ECMO remains as a final ultima ratio.

A reply

We are grateful to Drs McCormack and Kelly for their interest in our publication on the accuracy of non-invasive carbon dioxide monitoring. They correctly point out that transcutaneous Pco2 (Ptcco2) measurement may be influenced by low cardiac output, and that we did not obtain cardiac index values at the time of the measurements. Because most of our study patients had normal cardiac function, insertion of a pulmonary arterial catheter was rarely indicated or justified. Therefore, cardiac index values were available only in a small minority of our patients. However, pre-existing normal cardiac function and haemodynamic stability make low cardiac output a very unlikely confounder of our study. Drs McCormack and Kelly have also missed data on the effects of vasopressor therapy on Ptcco2 values in our study. We have not reported these data in detail but stated in the Results section that vasopressors did not influence the accuracy of Ptcco2 monitoring in our study patients. As mentioned in the discussion, these findings are in agreement with those of two recent studies [1, 2] that also failed to find an influence of administered of vasopressors on Ptcco2 measurements. Drs McCormack and Kelly postulate that interpretation of data from patients with pulmonary pathologies may be difficult because of the disturbed pulmonary carbon dioxide transfer. We agree that pulmonary pathologies may influence the arterial Pco2 level. However, why should transcutaneous carbon dioxide transfer be influenced by pulmonary disease, unless the latter is combined with major haemodynamic consequences? The same holds true for low PEEP (2–8 mmHg), as used in our patients. PEEP has been found to influence Ptcco2 measurements only at higher PEEP levels [3]. Drs McCormack and Kelly correctly state that findings of industry-sponsored trials may not necessarily be invalid. However, conflicts of interest may arise at various levels when industry representatives perform or co-author studies involving their own products, thus questioning the reliability of their study results [4]. We are grateful to the manufacturers for providing the monitors and all disposables based on a contract that confirmed our unrestricted right to interpret and publish the data. We fully support Drs McCormack and Kelly's call for further scientific evaluation of transcutaneous Pco2 monitoring. We only tested its usefulness in the specific setting of patients during and shortly after major surgery. Our conclusion may not apply to patients in different clinical settings.

Moderate hypothermia attenuates changes in respiratory system mechanics and cytokine production during low lung volume ventilation in rats

Hypothermia was shown to attenuate ventilator-induced lung injury (VILI) in high end-inspiratory lung volume models of VILI [1-3]. Experimental evidence suggests that moderate tidal volumes may, under certain clinical conditions that induce alveolar instability, lead to a lung injury [4]. Recent studies have also suggested that insults like shock [5] or surgery [6] sensitize the lung to injury by priming for an exaggerated response to a second stimulus. The aim of this study was to investigate whether moderate hypothermia attenuates low lung volume injury during low PEEP, high FiO2 and moderate tidal volume ventilation in animals sensitized to injury by previous anesthesia and surgery.