Nebulized ceftazidime in experimental pneumonia caused by partially resistant Pseudomonas aeruginosa

PURPOSE

Ventilator-associated pneumonia caused by Pseudomonas aeruginosa with impaired sensitivity to ceftazidime is frequent in critically ill patients. The aim of the study was to compare lung tissue deposition and antibacterial efficiency between nebulized and intravenous administrations of ceftazidime in ventilated piglets with pneumonia caused by Pseudomonas aeruginosa with impaired sensitivity to ceftazidime.

METHODS

Ceftazidime was administered 24 h following the intra-bronchial inoculation of Pseudomonas aeruginosa (minimum inhibitory concentration = 16 microg ml(-1)), either by nebulization (25 mg kg(-1) every 3 h, n = 6) or by continuous intravenous infusion (90 mg kg(-1) over 24 h after an initial rapid infusion of 30 mg kg(-1), n = 6). Four non-treated inoculated animals served as controls. All piglets were killed 48 h (intravenous and control groups) or 51 h (aerosol group) after inoculation. Lung tissue concentrations and lung bacterial burden were assessed on multiple post-mortem sub-pleural lung specimens [(lower limit of quantitation = 10(2) colony forming unit (cfu g(-1))].

RESULTS

Ceftazidime trough lung tissue concentrations following nebulization were greater than steady-state lung tissue concentrations following continuous intravenous infusion [median and interquartile range, 24.8 (12.6-59.6) microg g(-1) vs. 6.1 (4.6-10.8) microg g(-1)] (p < 0.001). After 24 h of ceftazidime administration, 83% of pulmonary segments had bacterial counts <10(2) cfu g(-1) following nebulization and only 30% following intravenous administration (p < 0.001). In control animals, 10% of lung segments had bacterial counts <10(2) cfu g(-1) 48 h following bronchial inoculation.

CONCLUSION

Nebulized ceftazidime provides more efficient bacterial killing in ventilated piglets with pneumonia caused by Pseudomonas aeruginosa with impaired sensitivity to ceftazidime.

Chest computed tomography with multiplanar reformatted images for diagnosing traumatic bronchial rupture: a case report

INTRODUCTION

Unnoticed bronchial injury during the early stage of resuscitation of multiple trauma is not rare and increases mortality and morbidity.

METHODS

Three-dimensional reconstruction of the airways using a workstation connected to a multidetector chest computed tomography (CT) scanner may change the diagnostic strategy in patients with blunt chest trauma with clinical signs evocative of bronchial rupture.

RESULTS

In this case report of a young motor biker, a complete disruption of the intermediary trunk was first misdiagnosed using standard chest helical CT and bronchoscopy. Postprocessing procedures including three-dimensional extraction of the tracheobronchial tree were determinants for establishing the diagnosis, and emergent surgical repair was successfully performed. Follow-up using CT with three-dimensional reconstructions evidenced a bronchial stenosis located at the site of the rupture.

CONCLUSION

The present study demonstrates the potential interest of performing three-dimensional reconstructions by extraction of the tracheal-bronchial tree in patients with severe blunt chest trauma suspected of bronchial rupture.

Is bronchoalveolar lavage with quantitative cultures a useful tool for diagnosing ventilator-associated pneumonia?

The results of a recently published Canadian study suggest that bronchoalveolar lavage and endotracheal aspiration are associated with similar clinical outcomes and similar overall use of antibiotics in critically ill patients with suspected ventilator-associated pneumonia (VAP). The study, however, does not provide convincing information on the best strategy to diagnose VAP, to accurately choose initial treatment and to exclude VAP in order to avoid administering antibiotics to patients without bacterial infection. In fact, this trial has several limitations or drawbacks: patients at risk for developing VAP due to Pseudomonas aeruginosa or methicillin-resistant Staphylococcus aureus were excluded, far from the real-life scenario; a significant number of patients were receiving recent antimicrobial therapy at the time of sampling, with, consequently, difficult-to-interpret culture results; randomization of included patients for initial treatment – meropenem plus ciprofloxacin or meropenem alone – resulted in a high rate of inappropriate initial empirical therapy due to the absence of customization to local epidemiology; and the initial decision to treat and the re-evaluation at day 3 were, in fact, based on clinical judgment and not on direct examination and quantitative culture results. In summary, because antimicrobial treatment was initiated in all suspected patients and was rarely withheld in patients with negative cultures, the study does not suggest an appropriate strategy for improving the use of antibiotics in intensive care unit patients. Such a strategy has two requirements: immediate administration of adequate therapy in patients with true VAP, and avoidance of administering antibiotics in patients without bacterial infection.

Incidence of Chest Tube Malposition in the Critically Ill

Background

Malposition of percutaneously inserted chest tubes is considered as a rare complication in critically ill patients. Its incidence, however, remains uncertain. The aims of the study were to assess the true incidence of chest tube malposition in critically ill patients and to identify predicting factors.

Methods

The authors prospectively studied 122 chest tubes percutaneously inserted in 75 consecutive critically ill patients. For clinical reasons independent of the study, thoracic computed tomography scanning was performed in 63 patients, allowing direct visualization of 106 chest tubes. Based on these findings, chest tube position was classified as intrapleural, intrafissural, or intraparenchymal. Factors predicting chest tube malposition were analyzed by univariate and multivariate analysis.

Results

The mean delay between chest tube placement and thoracic scan was 3.5+/-2.9 days. Twenty-two chest tubes were diagnosed as being intrafissural (21%), and 10 were diagnosed as being intraparenchymal (9%). The only predicting factor associated with the risk of malposition was the use of a trocar for the percutaneous insertion of the chest tube (P=0.032).

Conclusions

Malposition was detected in 30% of percutaneously inserted chest tubes, a higher incidence than previously reported. Avoiding the use of a trocar may reduce significantly the incidence of chest tube malposition.

Response to recruitment maneuver influences net alveolar fluid clearance in acute respiratory distress syndrome

BACKGROUND

Alveolar fluid clearance is impaired in the majority of patients with acute respiratory distress syndrome (ARDS). Experimental studies have shown that a reduction of tidal volume increases alveolar fluid clearance. This study was aimed at assessing the impact of the response to a recruitment maneuver (RM) on net alveolar fluid clearance.

METHODS

In 15 patients with ARDS, pulmonary edema fluid and plasma protein concentrations were measured before and after an RM, consisting of a positive end-expiratory pressure maintained 10 cm H2O above the lower inflection point of the pressure-volume curve during 15 min. Cardiorespiratory parameters were measured at baseline (before RM) and 1 and 4 h later. RM-induced lung recruitment was measured using the pressure-volume curve method. Net alveolar fluid clearance was measured by measuring changes in bronchoalveolar protein concentrations before and after RM.

RESULTS

In responders, defined as patients showing an RM-induced increase in arterial oxygen tension of 20% of baseline value or greater, net alveolar fluid clearance (19 +/- 13%/h) and significant alveolar recruitment (113 +/- 101 ml) were observed. In nonresponders, neither net alveolar fluid clearance (-24 +/- 11%/h) nor alveolar recruitment was measured. Responders and nonresponders differed only in terms of lung morphology: Responders had a diffuse loss of aeration, whereas nonresponders had a focal loss of aeration, predominating in the lower lobes.

CONCLUSION

In the absence of alveolar recruitment and improvement in arterial oxygenation, RM decreases the rate of alveolar fluid clearance, suggesting that lung overinflation may be associated with epithelial dysfunction.

Clinical review: Bedside lung ultrasound in critical care practice

Lung ultrasound can be routinely performed at the bedside by intensive care unit physicians and may provide accurate information on lung status with diagnostic and therapeutic relevance. This article reviews the performance of bedside lung ultrasound for diagnosing pleural effusion, pneumothorax, alveolar-interstitial syndrome, lung consolidation, pulmonary abscess and lung recruitment/derecruitment in critically ill patients with acute lung injury.

Mechanical ventilation and lung infection in the genesis of air-space enlargement

Introduction

Air-space enlargement may result from mechanical ventilation and/or lung infection. The aim of this study was to assess how mechanical ventilation and lung infection influence the genesis of bronchiolar and alveolar distention.

Methods

Four groups of piglets were studied: non-ventilated-non-inoculated (controls, n = 5), non-ventilated-inoculated (n = 6), ventilated-non-inoculated (n = 6), and ventilated-inoculated (n = 8) piglets. The respiratory tract of intubated piglets was inoculated with a highly concentrated solution of Escherichia coli. Mechanical ventilation was maintained during 60 hours with a tidal volume of 15 ml/kg and zero positive end-expiratory pressure. After sacrifice by exsanguination, lungs were fixed for histological and lung morphometry analyses.

Results

Lung infection was present in all inoculated piglets and in five of the six ventilated-non-inoculated piglets. Mean alveolar and mean bronchiolar areas, measured using an analyzer computer system connected through a high-resolution color camera to an optical microscope, were significantly increased in non-ventilated-inoculated animals (+16% and +11%, respectively, compared to controls), in ventilated-non-inoculated animals (+49% and +49%, respectively, compared to controls), and in ventilated-inoculated animals (+95% and +118%, respectively, compared to controls). Mean alveolar and mean bronchiolar areas significantly correlated with the extension of lung infection (R = 0.50, p < 0.01 and R = 0.67, p < 0.001, respectively).

Conclusion

Lung infection induces bronchiolar and alveolar distention. Mechanical ventilation induces secondary lung infection and is associated with further air-space enlargement. The combination of primary lung infection and mechanical ventilation markedly increases air-space enlargement, the degree of which depends on the severity and extension of lung infection.

Transthoracic ultrasound approach of thoracic aorta in critically ill patients with lung consolidation

PURPOSE

Normally, the aortic arch and the descending aorta are not visible using transthoracic ultrasonography. We hypothesize that lung consolidation of upper and lower lobes, by opening an acoustic window, may allow the ultrasound examination of the thoracic aorta.

METHODS

During a 2-month period, 18 consecutive patients hospitalized in the intensive care unit with consolidation of upper and/or lower lobes diagnosed by lung ultrasound were studied. The ascending and descending aorta and the aortic arch were systematically searched for by positioning the probe on the anterior, lateral, and posterior regions of the chest wall.

RESULTS

Among the 16 patients with left lower lobe consolidation, the descending aorta was always visible by positioning the probe on lateral and posterior parts of the chest wall. In the 4 patients with consolidation of the left upper lobe, the aortic arch was visible when positioning the probe on anterior and upper parts of the left chest wall. In the patient with right upper lobe consolidation, both the ascending aorta and the aortic arch were visible when positioning the probe on anterior and upper parts of the right chest wall.

CONCLUSIONS

In critically ill patients, the presence of consolidated upper and left lower lobes may allow the ultrasound examination of the different parts of the thoracic aorta.

Lung deposition of continuous and intermittent intravenous ceftazidime in experimental Pseudomonas aeruginosa bronchopneumonia

OBJECTIVE

Lung tissue deposition of intravenous ceftazidime administered either continuously or intermittently was compared in ventilated piglets with experimental bronchopneumonia.

DESIGN

Prospective experimental study

ANIMALS

Eighteen anesthetized and ventilated piglets

INTERVENTIONS

Bronchopneumonia was produced by the intrabronchial inoculation of Pseudomonas aeruginosa characterized by an impaired sensitivity to ceftazidime (MIC 16 mg/l). Ceftazidime was administered either through a continuous infusion of 90 mg/kg per 24 h after a bolus of 30 mg/kg or by an intermittent infusion of 30 mg/kg per 8 h.

MEASUREMENTS AND RESULTS

Piglets were killed 24 h after the initiation of continuous ceftazidime (n = 6), and 1 h (peak, n = 6) and 8 h (trough, n = 6) after the third dose following intermittent administration. Lung tissue concentrations of ceftazidime, measured by HPLC, and lung bacterial burden were assessed on multiple postmortem lung specimens. During continuous administration ceftazidime lung tissue concentrations were 9.7 +/- 3.8 microg/g. Following intermittent administration peak and trough lung tissue concentrations were, respectively, 7.1 +/- 2.4 microg/g and 0.6 +/- 1 microg/g. Lung bacterial burden was different after continuous and intermittent administration (median 7.10(3) vs. 4.10(2) cfu/g).

CONCLUSIONS

Continuous infusion of ceftazidime maintained higher tissue concentrations than intermittent administration.

Aggressive Management of Nonocclusive Ischemic Colitis Following Aortic Reconstruction

HYPOTHESIS

Under standard conditions following aortic reconstruction, nonocclusive ischemic colitis (IC) type 1 (mucosal ischemia) and type 2 (mucosal and muscularis ischemia) can be managed nonoperatively, whereas type 3 (transmural ischemia) requires emergency surgery. Our objective was to standardize the surgical approach for IC complicating aortic reconstruction.

DESIGN

Retrospective cohort study.

SETTING

General surgery, vascular surgery, anesthesiology, and critical care units in a university-affiliated hospital.

METHODS

From January 5, 1997, to December 15, 2003, 49 cases of IC complicating aortic reconstruction were diagnosed (rate, 2.7%). Nonoperative management was used for patients with type 1 or type 2 without multiple organ failure (MOF). All patients with type 3 or with type 2 with MOF underwent urgent resection of the ischemic colon without anastomosis.

RESULTS

Immediate surgery was performed on 24 patients (49.0%). Nineteen (76.0%) of 25 patients without MOF and with transient endoscopic findings underwent secondary surgery for progression to final IC type 3 (16 patients) or to final IC type 2 with MOF (3 patients). Twenty-three (53.5%) of 43 patients died after colorectal resection (overall mortality, 46.9%). Factors causing significant risk of death were surgery, MOF, final IC type, and amount of perioperative transfusion. The mortality was 57.1% for final IC type 3, 37.5% for final IC type 2 with MOF, and 0% for final IC type 1 or type 2 without MOF.

CONCLUSIONS

Selective management of postoperative IC, based on MOF and the degree of ischemia, is the suggested course of action. For patients with mild ischemia and MOF, an aggressive approach is recommended.

Measurement of alveolar derecruitment in patients with acute lung injury: computerized tomography versus pressure-volume curve

INTRODUCTION

Positive end-expiratory pressure (PEEP)-induced lung derecruitment can be assessed by a pressure-volume (P-V) curve method or by lung computed tomography (CT). However, only the first method can be used at the bedside. The aim of the study was to compare both methods for assessing alveolar derecruitment after the removal of PEEP in patients with acute lung injury or acute respiratory distress syndrome.

METHODS

P-V curves (constant-flow method) and spiral CT scans of the whole lung were performed at PEEPs of 15 and 0 cmH2O in 19 patients with acute lung injury or acute respiratory distress syndrome. Alveolar derecruitment was defined as the difference in lung volume measured at an airway pressure of 15 cmH2O on P-V curves performed at PEEPs of 15 and 0 cmH2O, and as the difference in the CT volume of gas present in poorly aerated and nonaerated lung regions at PEEPs of 15 and 0 cmH2O.

RESULTS

Alveolar derecruitments measured by the CT and P-V curve methods were 373 +/- 250 and 345 +/- 208 ml (p = 0.14), respectively. Measurements by both methods were tightly correlated (R = 0.82, p < 0.0001). The derecruited volume measured by the P-V curve method had a bias of -14 ml and limits of agreement of between -158 and +130 ml in comparison with the average derecruited volume of the CT and P-V curve methods.

CONCLUSION

Alveolar derecruitment measured by the CT and P-V curve methods are tightly correlated. However, the large limits of agreement indicate that the P-V curve and the CT method are not interchangeable.

Open and closed-circuit endotracheal suctioning in acute lung injury: efficiency and effects on gas exchange

BACKGROUND

Closed-circuit endotracheal suctioning (CES) is advocated for preventing hypoxemia caused by the loss of lung volume resulting from open endotracheal suctioning (OES). However, the efficiency of CES and OES on tracheal secretion removal has never been compared in patients with acute lung injury. The authors designed a two-part study aimed at comparing gas exchange and efficiency between OES and CES performed at two levels of negative pressure.

METHODS

Among 18 patients with acute lung injury, 9 underwent CES and OES at 3-h intervals in a random order using a negative pressure of -200 mmHg. Nine other patients underwent CES twice using two levels of negative pressure (-200 and -400 mmHg) applied in a random order. After each CES, a recruitment maneuver was performed using 20 consecutive hyperinflations. Tracheal aspirates were weighed after each suctioning procedure. Arterial blood gases were continuously recorded using an intravascular sensor.

RESULTS

Open endotracheal suctioning induced a significant 18% decrease in arterial oxygen tension (Pa(O2)) (range, +13 to -71%) and an 8% increase in arterial carbon dioxide tension (Pa(CO2)) (range, -2 to +16%) that persisted 15 min after the end of the procedure. CES using -200 cm H2O did not change Pa(O2), but tracheal aspirate mass was lower compared with OES (0.6 +/- 1.0 vs. 3.2 +/- 5.1 g; P = 0.03). Increasing negative pressure to -400 cm H2O during CES did not change Pa(O2) but increased the tracheal aspirate mass (1.7 +/- 1.6 vs. 1.0 +/- 1.3 g; P = 0.02).

CONCLUSIONS

Closed-circuit endotracheal suctioning followed by a recruitment maneuver prevents hypoxemia resulting from OES but decreases secretion removal. Increasing suctioning pressure enhances suctioning efficiency without impairing gas exchange.

Novel and Innovative Strategies to Treat Ventilator-Associated Pneumonia: Optimizing the Duration of Therapy and Nebulizing Antimicrobial Agents

Ventilator-associated pneumonia (VAP) is responsible for approximately half of the infections acquired in the intensive care unit (ICU) and represents one of the principal reasons for prescribing antibiotics in this setting. Because unnecessary prolongation of antimicrobial therapy and insufficient dosing of antibiotics at the site of infection in patients with true bacterial infection may lead to the selection of multidrug-resistant microorganisms without improving clinical outcome, efforts to reduce the duration of therapy and optimize pulmonary penetration of antimicrobial agents are warranted. An 8-day regimen can probably be standard for patients with VAP. Possible exceptions to this recommendation include immunosuppressed patients, those whose initial antimicrobial treatment was not appropriate for the causative microorganism(s), and patients whose infection was caused by very difficult-to-treat microorganisms and had no improvement in clinical signs of infection. Nebulizing concentration-dependent antibiotics such as aminoglycosides during mechanical ventilation can markedly increase tissue penetration in foci of pneumonia as compared with intravenous administration. The superiority in terms of pulmonary penetration and antibacterial efficacy of this route of administration was demonstrated in a model of ventilated piglets with and without bronchopneumonia.

Bench-to-bedside review: adjuncts to mechanical ventilation in patients with acute lung injury

Mechanical ventilation is indispensable for the survival of patients with acute lung injury and acute respiratory distress syndrome. However, excessive tidal volumes and inadequate lung recruitment may contribute to mortality by causing ventilator-induced lung injury. This bench-to-bedside review presents the scientific rationale for using adjuncts to mechanical ventilation aimed at optimizing lung recruitment and preventing the deleterious consequences of reduced tidal volume. To enhance CO₂ elimination when tidal volume is reduced, the following are possible: first, ventilator respiratory frequency can be increased without necessarily generating intrinsic positive end-expiratory pressure; second, instrumental dead space can be reduced by replacing the heat and moisture exchanger with a conventional humidifier; and third, expiratory washout can be used for replacing the CO₂-laden gas present at end expiration in the instrumental dead space by a fresh gas (this method is still experimental). For optimizing lung recruitment and preventing lung derecruitment there are the following possibilities: first, recruitment manoeuvres may be performed in the most hypoxaemic patients before implementing the preset positive end-expiratory pressure or after episodes of accidental lung derecruitment; second, the patient can be turned to the prone position; third, closed-circuit endotracheal suctioning is to be preferred to open endotracheal suctioning.

Intravenous versus nebulized ceftazidime in ventilated piglets with and without experimental bronchopneumonia: comparative effects of helium and nitrogen

BACKGROUND

Lung deposition of intravenous cephalosporins is low. The lung deposition of equivalent doses of ceftazidime administered either intravenously or by ultrasonic nebulization using either nitrogen-oxygen or helium-oxygen as the carrying gas of the aerosol was compared in ventilated piglets with and without experimental bronchopneumonia.

METHODS

Five piglets with noninfected lungs and 5 piglets with Pseudomonas aeruginosa experimental bronchopneumonia received 33 mg/kg ceftazidime intravenously. Ten piglets with noninfected lungs and 10 others with experimental P. aeruginosa bronchopneumonia received 50 mg/kg ceftazidime by ultrasonic nebulization. In each group, the ventilator was operated in half of the animals with a 65%/35% helium-oxygen or nitrogen-oxygen mixture. Animals were killed, and multiple lung specimens were sampled for measuring ceftazidime lung tissue concentrations by high-performance liquid chromatography.

RESULTS

As compared with intravenous administration, nebulization of ceftazidime significantly increased lung tissue concentrations (17 +/- 13 vs. 383 +/- 84 microg/g in noninfected piglets and 10 +/- 3 vs. 129 +/- 108 microg/g in piglets with experimental bronchopneumonia; P < 0.001). The use of a 65%/35% helium-oxygen mixture induced a 33% additional increase in lung tissue concentrations in noninfected piglets (576 +/- 141 microg/g; P < 0.001) and no significant change in infected piglets (111 +/- 104 microg/g).

CONCLUSION

Nebulization of ceftazidime induced a 5- to 30-fold increase in lung tissue concentrations as compared with intravenous administration. Using a helium-oxygen mixture as the carrying gas of the aerosol induced a substantial additional increase in lung deposition in noninfected piglets but not in piglets with experimental bronchopneumonia.

Low spatial resolution computed tomography underestimates lung overinflation resulting from positive pressure ventilation*

OBJECTIVE

In acute lung injury, lung overinflation resulting from mechanical ventilation with positive end-expiratory pressure (PEEP) can be assessed using lung computed tomography. The goal of this study was to compare lung overinflation measured on low and high spatial resolution computed tomography sections.

DESIGN

Lung overinflation was measured on thick (10-mm) and thin (1.5-mm) computed tomography sections obtained at zero end-expiratory pressure (ZEEP) and PEEP 10 cm H2O using a software including a color-coding system.

SETTING

A 20-bed surgical intensive care unit of a university hospital.

PATIENTS

Thirty mechanically ventilated patients with acute lung injury.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Overinflated lung volume was measured as the end-expiratory volume of lung regions with computed tomography attenuations <-900 Hounsfield units. Lung overinflation, expressed in percentage of the total lung volume, was significantly underestimated by thick computed tomography sections compared with thin computed tomography sections (0.4 +/- 1.6% vs. 3.0 +/- 4.0% in ZEEP and 1.9 +/- 4% vs. 6.8 +/- 7.3% in PEEP, p < .01). In patients with a diffuse loss of aeration, the overinflated lung volumes of thick and thin computed tomography sections were, respectively, 0.6 +/- 0.8 mL vs. 16 +/- 10 mL in ZEEP (p < .01) and 8 +/- 9 mL vs. 73 +/- 62 mL in PEEP (p < .05). In patients with a focal loss of aeration, this underestimation was more pronounced: 18 +/- 56 mL vs. 127 +/- 140 mL in ZEEP (p < .01) and 85 +/- 161 mL vs. 322 +/- 292 mL in PEEP (p < .01).

CONCLUSIONS

In patients with acute lung injury, an accurate computed tomography estimation of lung overinflation resulting from positive pressure mechanical ventilation requires high spatial resolution computed tomography sections, particularly when the lung morphology shows a focal loss of aeration.

Incidence and regional distribution of lung overinflation during mechanical ventilation with positive end-expiratory pressure

OBJECTIVE

In patients with acute lung injury, alveolar recruitment resulting from positive end-expiratory pressure (PEEP) may be associated with overinflation of previously aerated lung regions. The aim of this study was to assess the incidence and regional distribution of lung overinflation resulting from mechanical ventilation with PEEP.

DESIGN

Reanalysis with a specific software including a color-coding system of quantitative lung computed tomography data obtained in four previous prospective studies.

SETTING

A 20-bed surgical intensive care unit of a Parisian university hospital.

PATIENTS

Thirty-two patients with acute lung injury in whom computed tomography of the whole lung was obtained at zero end-expiratory pressure (ZEEP) and PEEP 15 cm H2O.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Total lung recruitment was measured as the reaeration of poorly aerated (computed tomography attenuations ranging between -500 and -100 Hounsfield units) and nonaerated (computed tomography attenuations > or = -100 Hounsfield units) lung areas, and overinflation was measured as the lung volume characterized by computed tomography attenuations < or = -900 Hounsfield units. PEEP was associated with a significant alveolar recruitment (423 +/- 178 mL). Concomitantly, a lung overinflation of 123 +/- 138 mL was found in 14 patients (44%). In eight patients without chronic obstructive pulmonary disease, lung overinflation was predominantly found in nondependent lung regions located beneath the dome of diaphragm. In six patients with a past history of chronic obstructive pulmonary disease, PEEP increased the volume of emphysematous areas present in apical lung regions and produced an overinflation of nondependent lung regions located beneath the dome of diaphragm.

CONCLUSION

Lung overinflation resulting from mechanical ventilation with PEEP is observed in more than one third of patients with acute lung injury lying supine and predominates in caudal and nondependent lung regions. Furthermore, in patients with a history of chronic obstructive pulmonary disease, PEEP markedly increases the volume of emphysematous lung regions.