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

Positive end-expiratory pressure in acute respiratory distress syndrome: should the 'open lung strategy' be replaced by a 'protective lung strategy'?

In patients with acute respiratory distress syndrome, positive end-expiratory pressure is associated with alveolar recruitment and lung hyperinflation despite the administration of a low tidal volume. The best positive end-expiratory pressure should correspond to the best compromise between recruitment and distension, a condition that coincides with the best respiratory elastance

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 cmH(2)O 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 cmH(2)O on P–V curves performed at PEEPs of 15 and 0 cmH(2)O, and as the difference in the CT volume of gas present in poorly aerated and nonaerated lung regions at PEEPs of 15 and 0 cmH(2)O. 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

Computed tomography assessment of exogenous surfactant-induced lung reaeration in patients with acute lung injury

Introduction: Previous randomized trials failed to demonstrate a decrease in mortality of patients with acute lung injury treated by exogenous surfactant. the aim of this prospective randomized study was to evaluate the effects of exogenous porcine-derived surfactant on pulmonary reaeration and lung tissue in patients with acute lung injury and acute respiratory distress syndrome (ALI/ARDS).Methods: Twenty patients with ALI/ARDS were studied (10 treated by surfactant and 10 controls) in whom a spiral thoracic computed tomography scan was acquired before (baseline), 39 hours and 7 days after the first surfactant administration. in the surfactant group, 3 doses of porcine-derived lung surfactant (200 mg/kg/dose) were instilled in both lungs at 0, 12 and 36 hours. Each instillation was followed by recruitment maneuvers. Gas and tissue volumes were measured separately in poorly/nonaerated and normally aerated lung areas before and seven days after the first surfactant administration. Surfactant-induced lung reaeration was defined as an increase in gas volume in poorly/non-aerated lung areas between day seven and baseline compared to the control group.Results: At day seven, surfactant induced a significant increase in volume of gas in poorly/non-aerated lung areas (320 +/- 125 ml versus 135 +/- 161 ml in controls, P = 0.01) and a significant increase in volume of tissue in normally aerated lung areas (189 +/- 179 ml versus -15 +/- 105 ml in controls, P < 0.01). PaO2/FiO(2) ratio was not different between the surfactant treated group and control group after surfactant replacement.Conclusions: Intratracheal surfactant replacement induces a significant and prolonged lung reaeration. It also induces a significant increase in lung tissue in normally aerated lung areas, whose mechanisms remain to be elucidated.Univ Paris 06, Multidisciplinary Intens Care Unit, Dept Anesthesiol & Crit Care Med, La Pitie Salpetriere Hosp,Assistance Publ Hop Par, F-75013 Paris, FranceZhejiang Univ, Sch Med, Affiliated Hosp 2, Dept Emergency Med, Hangzhou 310009, Zhejiang, Peoples R ChinaUniversidade Federal de São Paulo, Dept Anesthesiol, Escola Paulista Med, BR-04024002 São Paulo, BrazilUniv Med Ctr Utrecht, Dept Intens Care Med, NL-3584 CX Utrecht, NetherlandsUniversidade Federal de São Paulo, Dept Anesthesiol, Escola Paulista Med, BR-04024002 São Paulo, BrazilWeb of Scienc

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-ventilatednon- 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

Accuracy and precision of end-expiratory lung-volume measurements by automated nitrogen washout/washin technique in patients with acute respiratory distress syndrome

Introduction End-expiratory lung volume (EELV) is decreased in acute respiratory distress syndrome (ARDS), and bedside EELV measurement may help to set positive end-expiratory pressure (PEEP). Nitrogen washout/washin for EELV measurement is available at the bedside, but assessments of accuracy and precision in real-life conditions are scant. Our purpose was to (a) assess EELV measurement precision in ARDS patients at two PEEP levels (three pairs of measurements), and (b) compare the changes (Δ) induced by PEEP for total EELV with the PEEP-induced changes in lung volume above functional residual capacity measured with passive spirometry (ΔPEEP-volume). The minimal predicted increase in lung volume was calculated from compliance at low PEEP and ΔPEEP to ensure the validity of lung-volume changes. Methods Thirty-four patients with ARDS were prospectively included in five university-hospital intensive care units. ΔEELV and ΔPEEP volumes were compared between 6 and 15 cm H2O of PEEP. Results After exclusion of three patients, variability of the nitrogen technique was less than 4%, and the largest difference between measurements was 81 ± 64 ml. ΔEELV and ΔPEEP-volume were only weakly correlated (r 2 = 0.47); 95% confidence interval limits, -414 to 608 ml). In four patients with the highest PEEP (≥ 16 cm H2O), ΔEELV was lower than the minimal predicted increase in lung volume, suggesting flawed measurements, possibly due to leaks. Excluding those from the analysis markedly strengthened the correlation between ΔEELV and ΔPEEP volume (r 2 = 0.80). Conclusions In most patients, the EELV technique has good reproducibility and accuracy, even at high PEEP. At high pressures, its accuracy may be limited in case of leaks. The minimal predicted increase in lung volume may help to check for accuracy