Alveolar fluid clearance in healthy pigs and influence of positive end-expiratory pressure

Furosemide and Albumin for Diuresis of Edema (FADE): A parallel-group, blinded, pilot randomized controlled trial

PURPOSE

To assess the feasibility of a trial evaluating whether hyperoncotic albumin, in addition to diuretics, improves diuresis and facilitates liberation from mechanical ventilation in critically ill adults.

MATERIALS AND METHODS

We randomized 46 hemodynamically stable patients with hypoalbuminemia, prescribed diuretics by treating clinicians, to receive 100 mL of 25% albumin or 0.9% saline placebo BID, for three days, in blinded fashion. We chose five feasibility measurements: enrolment of 50% of eligible patients, at least one patient/week; administration of study treatment within 2 h of diuretics in 85% of patients; completion of study regimen in 80% of patients; and avoidance of open label albumin in 85% of patients. Clinical outcomes included fluid balance, ventilator-free days, and mortality.

RESULTS

We randomized 85% of eligible patients. Eighty-four percent received study treatment within 2 h of diuretics, 69% received all doses of study treatment. Study treatment was held in the albumin and placebo groups because of no further need for diuresis (4 vs. 1), hypotension (2 v. 4), and albumin > 35 (1 v. 0). Twenty percent of patients received open-label albumin. Clinical outcomes were similar between groups.

CONCLUSIONS

The current study design did not demonstrate feasibility, but can inform the design of a definitive trial.

Comparison of continuous compression with regular ventilations versus 30:2 compressions-ventilations strategy during mechanical cardiopulmonary resuscitation in a porcine model of cardiac arrest

Background

A compression-ventilation (C:V) ratio of 30:2 is recommended for adult cardiopulmonary resuscitation (CPR) by the current American Heart Association (AHA) guidelines. However, continuous chest compression (CCC) is an alternative strategy for CPR that minimizes interruption especially when an advanced airway exists. In this study, we investigated the effects of 30:2 mechanical CPR when compared with CCC in combination with regular ventilation in a porcine model.

Methods

Sixteen male domestic pigs weighing 39±2 kg were utilized. Ventricular fibrillation was induced and untreated for 7 min. The animals were then randomly assigned to receive CCC combined with regular ventilation (CCC group) or 30:2 CPR (VC group). Mechanical chest compression was implemented with a miniaturized mechanical chest compressor. At the same time of beginning of precordial compression, the animals were mechanically ventilated at a rate of 10 breaths-per-minute in the CCC group or with a 30:2 C:V ratio in the VC group. Defibrillation was delivered by a single 150 J shock after 5 min of CPR. If failed to resuscitation, CPR was resumed for 2 min before the next shock. The protocol was stopped if successful resuscitation or at a total of 15 min. The resuscitated animals were observed for 72 h.

Results

Coronary perfusion pressure, end-tidal carbon dioxide and carotid blood flow in the VC group were similar to those achieved in the CCC group during CPR. No significant differences were observed in arterial blood gas parameters between two groups at baseline, VF 6 min, CPR 4 min and 30, 120 and 360 min post-resuscitation. Although extravascular lung water index of both groups significantly increased after resuscitation, no distinct difference was found between CCC and VC groups. All animals were successfully resuscitated and survived for 72 h with favorable neurologic outcomes in both groups. However, obviously more numbers of rib fracture were observed in CCC animals in comparison with VC animals.

Conclusions

There was no difference in hemodynamic efficacy and gas exchange during and after resuscitation, therefore identical 72 h survival with intact neurologic function was observed in both VC and CCC groups. However, the incidence of rib fracture increases during the mechanical CPR strategy of CCC combined with regular ventilations.

Variations of Postresuscitation Lung Function after Thrombolysis Therapy in a Cardiac Arrest Porcine Model Caused by Pulmonary Thromboembolism

BACKGROUND

Study of lung function in survivor from cardiac arrest (CA) caused by pulmonary thromboembolism (PTE) was rare. The aim of this study was to investigate the variations of postresuscitation lung function after thrombolysis treatment in a CA porcine model caused by PTE.

METHODS

After 2 min of untreated CA, pigs of 10-12 weeks with a weight of 30 ± 2 kg (n = 24) were treated with recombinant human tissue plasminogen activator (50 mg). Cardiopulmonary resuscitation (CPR) and ventilation were initiated after drug administration. Pulmonary function and arterial blood gas parameters were measured at baseline, return of spontaneous circulation (ROSC) immediately, and 1 h, 2 h, 4 h, and 6 h after ROSC.

RESULTS

The dynamic lung compliance decreased significantly at ROSC immediately and 1 h after ROSC compared to baseline (21.86 ± 2.00 vs. 26.72 ± 2.20 ml/mmHg and 20.38 ± 1.31 vs. 26.72 ± 2.20 ml/mmHg, respectively; P < 0.05; 1 mmHg = 0.133 kPa). Compared with baseline, airway resistance increased significantly at ROSC immediately and 1 h after ROSC (P < 0.05). Respiratory index also increased after ROSC and showed significant differences among baseline, ROSC immediately, and 2 h after ROSC (P < 0.05). Oxygen delivery decreased at ROSC immediately compared to baseline (P < 0.05). The oxygenation index decreased significantly at any time after ROSC compared to baseline (P < 0.05). Extravascular lung water index and pulmonary vascular permeability index (PVPI) showed significant differences at ROSC immediately compared to baseline and 1 h after ROSC (P < 0.05); PVPI at ROSC immediately was also different from 6 h after ROSC (P < 0.05). Ventilation/perfusion ratios increased after ROSC (P < 0.05). Histopathology showed fibrin effusion, bleeding in alveoli, and hemagglutination in pulmonary artery.

CONCLUSIONS

Lung function remains abnormal even after CPR with thrombolysis therapy; it is essential to continue anticoagulation and symptomatic treatment after ROSC.

Transpulmonary thermodilution: advantages and limits

Background

For complex patients in the intensive care unit or in the operating room, many questions regarding their haemodynamic management cannot be answered with simple clinical examination. In particular, arterial pressure allows only a rough estimation of cardiac output. Transpulmonary thermodilution is a technique that provides a full haemodynamic assessment through cardiac output and other indices.

Main body

Through the analysis of the thermodilution curve recorded at the tip of an arterial catheter after the injection of a cold bolus in the venous circulation, transpulmonary thermodilution intermittently measures cardiac output. This measure allows the calibration of pulse contour analysis. This provides continuous and real time monitoring of cardiac output, which is not possible with the pulmonary artery catheter. Transpulmonary thermodilution provides several variables beyond cardiac output. It estimates the end-diastolic volume of the four cardiac cavities, which is a marker of cardiac preload. It provides an estimation of the systolic function of the combined ventricles. It is more direct than the pulmonary artery catheter, but does not allow the distinct estimation of right and left cardiac function. It is easier and faster to perform than echocardiography, but does not provide a full evaluation of the cardiac structure and function. Transpulmonary thermodilution has the unique advantage of being able to estimate at the bedside extravascular lung water, which quantifies the volume of pulmonary oedema, and pulmonary vascular permeability, which quantifies the degree of a pulmonary capillary leak. Both indices are helpful for guiding fluid strategy, especially in case of acute respiratory distress syndrome.

Conclusions

Transpulmonary thermodilution provides a full cardiovascular evaluation that allows one to answer many questions regarding haemodynamic management. It belongs to the category of “advanced” devices that are indicated for the most critically ill and/or complex patients.

Increased Extravascular Lung Water and Plasma Biomarkers of Acute Lung Injury Precede Oxygenation Impairment in Primary Graft Dysfunction After Lung Transplantation

BACKGROUND

After lung transplantation (LT), early prediction of grade 3 pulmonary graft dysfunction (PGD) remains a research gap for clinicians. We hypothesized that it could be improved using extravascular lung water (EVLWi) and plasma biomarkers of acute lung injury.

METHODS

After institutional review board approval and informed consent, consecutive LT recipients were included. Transpulmonary thermodilution-based EVLWi, plasma concentrations of epithelial (soluble receptor for advanced glycation endproducts [sRAGE]) and endothelial biomarkers (soluble intercellular adhesion molecule-1 and endocan [full-length and cleaved p14 fragment]) were obtained before and after LT (0 [H0], 6, 12, 24, 48 and 72 hours after pulmonary artery unclamping). Grade 3 PGD was defined according to the International Society for Lung and Heart Transplantation definition, combining arterial oxygen partial pressure (PaO2)/inspired fraction of oxygen (FiO2) ratio and chest X-rays. Association of clinical risk factors, EVLWi and biomarkers with grade 3 PGD was analyzed under the Bayesian paradigm, using logistic model and areas under the receiver operating characteristic curves (AUCs).

RESULTS

In 47 LT recipients, 10 developed grade 3 PGD, which was obvious at H6 in 8 cases. Clinical risk factors, soluble intercellular adhesion molecule-1 and endocan (both forms) were not associated with grade 3 PGD. Significant predictors of grade 3 PGD included (1) EVLWi (optimal cutoff, 13.7 mL/kg; AUC, 0.74; 95% confidence interval [CI], 0.48-0.99), (2) PaO2/FiO2 ratio (optimal cutoff, 236; AUC, 0.68; 95% CI, 0.52-0.84), and (3) sRAGE (optimal cutoff, 11 760 pg/mL; AUC, 0.66; 95% CI, 0.41-0.91) measured at H0.

CONCLUSIONS

Immediate postreperfusion increases in EVLWi and sRAGE along with impaired PaO2/FiO2 ratios were early predictors of grade 3 PGD at or beyond 6 hours and may trigger early therapeutic interventions.

Patients Admitted to Three Spanish Intensive Care Units for Poisoning: Type of Poisoning, Mortality, and Functioning of Prognostic Scores Commonly Used

Objectives. To evaluate the gravity and mortality of those patients admitted to the intensive care unit for poisoning. Also, the applicability and predicted capacity of prognostic scales most frequently used in ICU must be evaluated. Methods. Multicentre study between 2008 and 2013 on all patients admitted for poisoning. Results. The results are from 119 patients. The causes of poisoning were medication, 92 patients (77.3%), caustics, 11 (9.2%), and alcohol, 20 (16,8%). 78.3% attempted suicides. Mean age was 44.42 ± 13.85 years. 72.5% had a Glasgow Coma Scale (GCS) ≤8 points. The ICU mortality was 5.9% and the hospital mortality was 6.7%. The mortality from caustic poisoning was 54.5%, and it was 1.9% for noncaustic poisoning (p < 0.001). After adjusting for SAPS-3 (OR: 1.19 (1.02–1.39)) the mortality of patients who had ingested caustics was far higher than the rest (OR: 560.34 (11.64–26973.83)). There was considerable discrepancy between mortality predicted by SAPS-3 (26.8%) and observed (6.7%) (Hosmer-Lemeshow test: H = 35.10; p < 0.001). The APACHE-II (7,57%) and APACHE-III (8,15%) were no discrepancies. Conclusions. Admission to ICU for poisoning is rare in our country. Medication is the most frequent cause, but mortality of caustic poisoning is higher. APACHE-II and APACHE-III provide adequate predictions about mortality, while SAPS-3 tends to overestimate.

Transpulmonary thermodilution enables to detect small short-term changes in extravascular lung water induced by a bronchoalveolar lavage

OBJECTIVE

To take the opportunity of a bronchoalveolar lavage to challenge the transpulmonary thermodilution for detecting the time course of changes in extravascular lung water.

DESIGN

Observational study.

SETTING

Medical ICU.

PATIENTS

Mechanically ventilated patients in whom a bronchoalveolar lavage by bronchoscopy was performed.

INTERVENTION

Transpulmonary thermodilution before and after bronchoalveolar lavage.

MEASUREMENTS AND MAIN RESULTS

Before and at different times after bronchoalveolar lavage, transpulmonary thermodilution was performed to record the value of indexed extravascular lung water. For each measurement, the values of three thermodilution measurements were averaged at the following steps: before bronchoalveolar lavage, after bronchoalveolar lavage, and 1 hour, 2 hours, 4 hours, and 6 hours after bronchoalveolar lavage. The amount of saline infusion left in the lungs after bronchoalveolar lavage was also recorded. Twenty-five patients with suspicion of pneumonia were included. Twenty-eight bronchoalveolar lavages were finally analyzed. On average, 200 mL (180-200 mL) of saline were injected and 130 mL (100-160 mL) were left in the lungs. Between before and immediately after bronchoalveolar lavage, indexed extravascular lung water significantly increased from 12 ± 4 to 15 ± 5 mL/kg, respectively, representing a 169 ± 166 mL increase in nonindexed extravascular lung water. After bronchoalveolar lavage, the value of indexed extravascular lung water was significantly different from the baseline value until 2 hours after bronchoalveolar lavage and became similar to the baseline value thereafter.

CONCLUSIONS

Transpulmonary thermodilution enabled to detect small short-term changes of indexed extravascular lung water secondary to bronchoalveolar lavage.

Extravascular lung water in critical care: recent advances and clinical applications

Extravascular lung water (EVLW) is the amount of fluid that is accumulated in the interstitial and alveolar spaces. In lung oedema, EVLW increases either because of increased lung permeability or because of increased hydrostatic pressure in the pulmonary capillaries, or both. Increased EVLW is always potentially life-threatening, mainly because it impairs gas exchange and reduces lung compliance. The only technique that provides an easy measurement of EVLW at the bedside is transpulmonary thermodilution. The validation of EVLW measurements by thermodilution was based on studies showing reasonable correlations with gravimetry or thermo-dye dilution in experimental and clinical studies. EVLW should be indexed to predicted body weight. This indexation reduces the proportion of ARDS patients for whom EVLW is in the normal range. Compared to non-indexed EVLW, indexed EVLW (EVLWI) is better correlated with the lung injury score and the oxygenation and it is a better predictor of mortality of patients with acute lung injury or acute respiratory distress syndrome (ARDS). Transpulmonary thermodilution also provides the pulmonary vascular permeability index (PVPI), which is an indirect reflection of the integrity of the alveolocapillary barrier. As clinical applications, EVLWI and PVPI may be useful to guide fluid management of patients at risk of fluid overload, as during septic shock and ARDS. High EVLWI and PVPI values predict mortality in several categories of critically ill patients, especially during ARDS. Thus, fluid administration should be limited when EVLWI is already high. Whatever the value of EVLWI, PVPI may indicate that fluid administration is particularly at risk of aggravating lung oedema. In the acute phase of haemodynamic resuscitation during septic shock and ARDS, high EVLWI and PVPI values may warn of the risk of fluid overload and prevent excessive volume expansion. At the post-resuscitation phase, they may prompt initiation of fluid removal thereby achieving a negative fluid balance.

TIP peptide inhalation in experimental acute lung injury: effect of repetitive dosage and different synthetic variants

Background

Inhalation of TIP peptides that mimic the lectin-like domain of TNF-α is a novel approach to attenuate pulmonary oedema on the threshold to clinical application. A placebo-controlled porcine model of acute respiratory distress syndrome (ARDS) demonstrated a reduced thermodilution-derived extravascular lung water index (EVLWI) and improved gas exchange through TIP peptide inhalation within three hours. Based on these findings, the present study compares a single versus a repetitive inhalation of a TIP peptide (TIP-A) and two alternate peptide versions (TIP-A, TIP-B).

Methods

Following animal care committee approval ARDS was induced by bronchoalveolar lavage followed by injurious ventilation in 21 anaesthetized pigs. A randomised-blinded three-group setting compared the single-dosed peptide variants TIP-A and TIP-B as well as single versus repetitive inhalation of TIP-A (n = 7 per group). Over two three-hour intervals parameters of gas exchange, transpulmonary thermodilution, calculated alveolar fluid clearance, and ventilation/perfusion-distribution were assessed. Post-mortem measurements included pulmonary wet/dry ratio and haemorrhage/congestion scoring.

Results

The repetitive TIP-A inhalation led to a significantly lower wet/dry ratio than a single dose and a small but significantly lower EVLWI. However, EVLWI changes over time and the derived alveolar fluid clearance did not differ significantly. The comparison of TIP-A and B showed no relevant differences. Gas exchange and ventilation/perfusion-distribution significantly improved in all groups without intergroup differences. No differences were found in haemorrhage/congestion scoring.

Conclusions

In comparison to a single application the repetitive inhalation of a TIP peptide in three-hour intervals may lead to a small additional reduction the lung water content. Two alternate TIP peptide versions showed interchangeable characteristics.

Effect of rescue breathing during cardiopulmonary resuscitation on lung function after restoration of spontaneous circulation in a porcine model of prolonged cardiac arrest

OBJECTIVE

The destruction of the pulmonary structure after cardiopulmonary resuscitation may lead to lung function breakdown. The aim of this study was to investigate lung function after cardiopulmonary resuscitation and the influence of rescue breathing on lung function.

DESIGN

Prospective, randomized animal study.

SETTING

A university animal research laboratory.

SUBJECTS

Twenty-eight male domestic pigs weighing 30 ± 2 kg.

INTERVENTIONS

The animals were randomized into three groups: continuous compressions (n = 12), 30:2 compression/rescue ventilation cardiopulmonary resuscitation (n = 12), and sham cardiopulmonary resuscitation (n = 4). Ventricular fibrillation was induced in the continuous compressions and compression/rescue ventilation groups.

MEASUREMENTS AND MAIN RESULTS

Cardiac output, extravascular lung water, and airway resistance were measured at baseline and 1, 2, and 4 hrs after restoration of spontaneous circulation. Thoracopulmonary compliance, lower inflection point, and dead space were calculated. Lung ventilation/perfusion scans with Tc were performed 48 hrs before the experiment and 24 hrs after restoration of spontaneous circulation. Conventional histopathology evaluation was performed. Dead space, airway resistance, lower inflection point, and extravascular lung water significantly increased and compliance decreased after restoration of spontaneous circulation in the continuous compressions and compression/rescue ventilation groups. Lung injury was more severe in the continuous compressions group. Significant differences were found between the two groups in the three time points after restoration of spontaneous circulation (p < 0.05). Variables of the sham cardiopulmonary resuscitation group remained stable during the whole protocol. Poor ventilation/perfusion and mismatch were found after restoration of spontaneous circulation, but the injury was mitigated in the compression/rescue ventilation group. Histopathology injury in the compression/rescue ventilation group was also improved.

CONCLUSIONS

Appropriate rescue breathing during cardiopulmonary resuscitation does not influence the prognosis of cardiac arrest or the hemodynamics after restoration of spontaneous circulation but can improve lung function and alleviate lung injury.

Prediction of pulmonary edema by plasma protein levels in patients with sepsis

PURPOSE

The difficulties of fluid therapy in patients with septic shock are to maintain sufficient vascular volume while preventing pulmonary edema formation. Thus, it is important to find a biomarker that can reliably predict pulmonary edema formation after fluid loading. We evaluated the association of plasma protein levels with the increase in extravascular lung water index (ΔEVLWI) after fluid loading.

METHODS

This was an observational study in which we retrospectively reviewed medical records of septic patients in whom hemodynamic variables were measured by transpulmonary thermodilution technique before and after fluid loading. Plasma protein levels were measured before fluid loading. Patients were divided into 2 groups according to the changes in EVLWI (ΔEVLWI ≥ 10%) after fluid loading. Diagnostic performance of plasma proteins in predicting pulmonary edema formation was assessed.

RESULTS

A total of 62 patients were included, and 27 of them showed a ΔEVLWI 10% or higher after fluid loading. Plasma albumin and transferrin were significantly lower in this group than in the group with ΔEVLWI less than 10% (21.7 ± 5.8 vs 25.3 ± 5.0 g/L for albumin, P < .05; 107.9 ± 50.1 vs 136.8 ± 44.2 mg/dL for transferrin, P < .05). Areas under the curve of albumin and transferrin were 0.68 (cardiac index, 0.54-0.83) and 0.72 (cardiac index, 0.59-0.86), respectively. At a cutoff value of 87.9 mg/dL, transferrin had a sensitivity of 0.91 in predicting ΔEVLWI 10% or higher.

CONCLUSIONS

Plasma transferrin and albumin levels were associated with ΔEVLWI 10% or higher after fluid loading. The high sensitivity of both biomarkers indicated that patients with normal values were less likely to develop pulmonary edema after fluid loading.

Aiming for a negative fluid balance in patients with acute lung injury and increased intra-abdominal pressure: a pilot study looking at the effects of PAL-treatment

INTRODUCTION

Achievement of a negative fluid balance in patients with capillary leak is associated with improved outcome. We investigated the effects of a multi-modal restrictive fluid strategy aiming for negative fluid balance in patients with acute lung injury (ALI).

METHODS

In this retrospective matched case-control study, we included 114 mechanically ventilated (MV) patients with ALI. We compared outcomes between a group of 57 patients receiving PAL-treatment (PAL group) and a matched control group, abstracted from a historical cohort. PAL-treatment combines high levels of positive end-expiratory pressure, small volume resuscitation with hyperoncotic albumin, and fluid removal with furosemide (Lasix®) or ultrafiltration. Effects on extravascular lung water index (EVLWI), intra-abdominal pressure (IAP), organ function, and vasopressor therapy were recorded during 1 week. The primary outcome parameter was 28-day mortality.

RESULTS

At baseline, no significant intergroup differences were found, except for lower PaO2/FIO2 and increased IAP in the PAL group (174.5 ± 84.5 vs 256.5 ± 152.7, p = 0.001; 10.0 ± 4.2 vs 8.0 ± 3.7 mmHg, p = 0.013, respectively). After 1 week, PAL-treated patients had a greater reduction of EVLWI, IAP, and cumulative fluid balance (-4.2 ± 5.6 vs -1.1 ± 3.7 mL/kg, p = 0.006; -0.4 ± 3.6 vs 1.8 ± 3.8 mmHg, p = 0.007; -1,451 ± 7,761 vs 8,027 ± 5,254 mL, p < 0.001). Repercussions on cardiovascular and renal function were limited. PAL-treated patients required fewer days of intensive care unit admission and days on MV (23.6 ± 15 vs 37.1 ± 19.9 days, p = 0.006; 14.6 ± 10.7 vs 25.5 ± 20.2 days, respectively) and had a lower 28-day mortality (28.1% vs 49.1%, p = 0.034).

CONCLUSION

PAL-treatment in patients with ALI is associated with a negative fluid balance, a reduction of EVLWI and IAP, and improved clinical outcomes without compromising organ function.

β-Adrenergic agonists differentially regulate highly selective and nonselective epithelial sodium channels to promote alveolar fluid clearance in vivo

β-Adrenergic receptors (β-AR) increase epithelial sodium channel (ENaC) activity to promote lung fluid clearance. However, the effect of selective β-AR agonist on highly selective cation (HSC) channels or nonselective cation (NSC) channels in alveolar type 1 (T1) and type 2 (T2) cells is unknown. We hypothesized that stimulation with β(1)-AR agonist (denopamine) or β(2)-AR agonist (terbutaline) would increase HSC and/or NSC channel activity in alveolar epithelial cells. We performed single-channel measurements from T1 and T2 cells accessed from rat lung slices. Terbutaline (20 μM) increased HSC ENaC activity (open probability, NP(o)) in T1 (from 0.96 ± 0.61 to 1.25 ± 0.71, n = 5, P <0.05) and T2 cells (from 0.28 ± 0.14 to 1.0 ± 0.30, n = 8, P = 0.02). Denopamine (20 μM) increased NSC NP(o) in T1 cells (from 0.34 ± 0.09 to 0.63 ± 0.14, n = 7, P = 0.02) and in T2 cells (from 0.47 ± 0.09 to 0.68 ± 0.10, P = 0.004). In vivo X-ray imaging of lung fluid clearance and ICI 118,551 selective inhibition of β(2)-ARs confirmed patch-clamp findings. cAMP concentrations increased following treatment with denopamine or terbutaline (n = 3, P < 0.002). The effects of systemic (intraperitoneal, IP) and local (intratracheal, IT) modes of delivery on lung fluid clearance were assessed. IT delivery of denopamine promoted alveolar flooding, whereas IP delivery promoted delayed fluid clearance. In summary, β-AR agonists differentially regulate HSC and NSC in T1 and T2 cells to promote lung fluid clearance in vivo, and the mode of drug delivery is critical for maximizing β-AR agonist efficacy.

Year in review 2010: Critical Care--Respirology

In this review, 21 original papers published last year in the respirology and critical care sections of Critical Care are classified and analyzed in the following categories: mechanical ventilation, lung recruitment maneuvers, and weaning; the role of positive end-expiratory pressure in acute lung injury models; animal models of ventilator-induced lung injury; diaphragmatic dysfunction; the role of mechanical ventilation in heart-lung interaction; and miscellanea.

Effects of surfactant depletion on regional pulmonary metabolic activity during mechanical ventilation

Inflammation during mechanical ventilation is thought to depend on regional mechanical stress. This can be produced by concentration of stresses and cyclic recruitment in low-aeration dependent lung. Positron emission tomography (PET) with (18)F-fluorodeoxyglucose ((18)F-FDG) allows for noninvasive assessment of regional metabolic activity, an index of neutrophilic inflammation. We tested the hypothesis that, during mechanical ventilation, surfactant-depleted low-aeration lung regions present increased regional (18)F-FDG uptake suggestive of in vivo increased regional metabolic activity and inflammation. Sheep underwent unilateral saline lung lavage and were ventilated supine for 4 h (positive end-expiratory pressure = 10 cmH(2)O, tidal volume adjusted to plateau pressure = 30 cmH(2)O). We used PET scans of injected (13)N-nitrogen to compute regional perfusion and ventilation and injected (18)F-FDG to calculate (18)F-FDG uptake rate. Regional aeration was quantified with transmission scans. Whole lung (18)F-FDG uptake was approximately two times higher in lavaged than in nonlavaged lungs (2.9 ± 0.6 vs. 1.5 ± 0.3 10(-3)/min; P < 0.05). The increased (18)F-FDG uptake was topographically heterogeneous and highest in dependent low-aeration regions (gas fraction 10-50%, P < 0.001), even after correction for lung density and wet-to-dry lung ratios. (18)F-FDG uptake in low-aeration regions of lavaged lungs was higher than that in low-aeration regions of nonlavaged lungs (P < 0.05). This occurred despite lower perfusion and ventilation to dependent regions in lavaged than nonlavaged lungs (P < 0.001). In contrast, (18)F-FDG uptake in normally aerated regions was low and similar between lungs. Surfactant depletion produces increased and heterogeneously distributed pulmonary (18)F-FDG uptake after 4 h of supine mechanical ventilation. Metabolic activity is highest in poorly aerated dependent regions, suggesting local increased inflammation.