Safety of bronchoalveolar lavage in patients with adult respiratory distress syndrome

Nitric oxide and nitrotyrosine in the lungs of patients with acute respiratory distress syndrome

Nitric oxide (NO) end-products (nitrate and nitrite) are present in bronchoalveolar lavage (BAL) fluid of patients with inflammatory lung diseases. Reactive oxygen-nitrogen intermediates damage macromolecules by oxidation or nitration of critical residues in proteins. The goal of this study was to measure NO end-products (nitrate+ nitrite), in BAL fluid before and after the onset of acute respiratory distress syndrome (ARDS) and to determine if these products are associated with expression of inducible nitric oxide synthase enzyme (iNOS) in BAL cells and nitration of BAL proteins. We performed bronchoalveolar lavage (BAL) in patients at risk for ARDS (n = 19), or with ARDS (n = 41) on Days 1, 3, 7, 14, and 21 after onset, and measured total nitrite (after reducing nitrate to nitrite) and protein-associated nitrotyrosine concentration in each BAL fluid sample. Cytospin preparations of BAL cells were analyzed by immunocytochemistry for iNOS and nitrotyrosine. Nitrate+nitrite were detected in BAL fluid from patients at risk for ARDS, and for as long as 21 d after the onset of ARDS. Nitrotyrosine was detectable in all BAL fluid samples for as long as 14 d after the onset of ARDS (range, 38.8 to 278.5 pmol/mg of protein), but not in BAL of normal volunteers. Alveolar macrophages of patients with ARDS were positive for iNOS and nitrotyrosine, and remained positive for as long as 14 d after onset of ARDS. The BAL nitrate+nitrite did not predict the onset of ARDS, but the concentration was significantly higher on Days 3 and 7 of ARDS in patients who died. Thus, NO end products accumulate in the lungs before and after onset of ARDS; iNOS is expressed at high levels in AM during ARDS; and nitration of intracellular and extracellular proteins occurs in the lungs in ARDS. The data support the concept that NO-dependent pathways are important in the lungs of patients before and after the onset of ARDS.

Continuous positive airway pressure during fiberoptic bronchoscopy in hypoxemic patients. A randomized double-blind study using a new device

Fiberoptic bronchoscopy (FOB) may worsen oxygenation and clinical status in severely hypoxemic patients. We conducted a prospective, randomized double-blind trial to compare the delivery of continuous positive airway pressure (CPAP) as a tool for maintaining oxygenation during FOB, to the delivery of oxygen only. Thirty consecutive patients who needed FOB for diagnostic purposes were enrolled. Their arterial oxygen pressure (Pa(O(2))) to inspired oxygen fraction (FI(O(2))) ratio was below 300 mm Hg. CPAP was generated by a simple new device open to the atmosphere. During FOB and the 30 min thereafter, pulse oximetry values (Sp(O(2))) were significantly higher in the CPAP than the Oxygen group (95.7 +/- 1.9% versus 92.6 +/- 3.1, p = 0.02). The lowest Sp(O(2)) values were observed in the Oxygen group (93.5 +/- 2.4% versus 88.6 +/- 3.4, p = 0.002). Arterial blood gases 15 min after FOB showed that Pa(O(2)) had increased in the CPAP group and decreased in the Oxygen group (DeltaPa(O(2)) = +10.5% +/- 16.9 versus -15% +/- 16.6, p = 0.01). Five patients in the Oxygen group, but none in the CPAP group, developed respiratory failure in the 6 h after FOB and required ventilatory assistance (p = 0.03). We conclude that in hypoxemic patients, the use of a new CPAP device during FOB allowed minimal alterations in gas exchange and prevented subsequent respiratory failure.

In vivo measurement of lung capillary-alveolar macromolecule permeability by saturation bronchoalveolar lavage

OBJECTIVE

Measurement of capillary-alveolar permeability to fluorescein isothiocyanate-dextran (FITC-D) (molecular mass, 71,300 daltons) by a sequential bronchoalveolar lavage (BAL) technique.

DESIGN

Animal research.

SETTING

The Department of Physiology at a scientific and medical university.

SUBJECTS

Nine anesthetized and mechanically ventilated dogs.

INTERVENTIONS

Two separate experiments were performed in each subject-an initial control experiment followed by an oleic acid-induced lung injury. The indicator was administered at constant blood concentration before serial BAL including eight fluid instillation-recovery cycles.

MEASUREMENTS

Plasma to BAL solute clearance at saturation (capillary-alveolar clearance at saturation, mL/min) was calculated and normalized to lavage fluid volume (measured by 1251 serum albumin dilution) to obtain a transport rate (TR) constant.

MAIN RESULTS

TR for FITC-D70 was 4.0+/-0.8 and 46.1+/-18.1 x 10(-5) x min(-1) in control and injured lung, respectively (p < .02). Capillary-alveolar clearance of FITC-D70 was not affected by the lavage procedure itself. TR reflected essentially epithelial permeability in normal lung and combined epithelial and endothelial permeability in injured lung. A significant correlation was found between cardiac output and TR in injured lung.

CONCLUSIONS

Saturation BAL allowed us to estimate capillary-alveolar macromolecule permeability in vivo in dogs. Further study may allow bedside evaluation of lung injury by BAL in patients.

Pleural Disease in the Intensive Care Unit

Pleural disease itself is an unusual cause for admission to the intensive care unit (ICU). Pleural complications of diseases and procedures in the ICU are common, however, and the impact on respiratory physiology is additive to that of the underlying cardiopulmonary disease. Pleural effusion and pneumothorax may be overlooked in the critically ill patient due to alterations in radiologic appearance in the supine patient. The development of a pneumothorax in a patient in the ICU represents a potentially life-threatening situation. This article reviews the etiologies, pathophysiology, and management of pleural effusion, pneumothorax, tension pneumothorax, and bronchopleural fistula in the critically ill patient. In addition, we review the potential complications of thoracentesis and chest tube thoracostomy, including re-expansion pulmonary edema.

Induction of interleukin-8 release by lung epithelium with cystic fibrosis epithelial lining fluid is marginally affected by inhibitors of interleukin-1beta

Interleukin-1beta (IL-1beta) and neutrophil elastase (NE) are present in the epithelial lining fluid (ELF) of patients with cystic fibrosis (CF). Both factors activate surrounding cells including lung epithelial cells, causing release of IL-8, a potent chemoattractant for neutrophils. Previous studies showed up-regulation of IL-8 release by lung epithelial cells as a function of NE in CF; however, few studies addressed the relationship between IL-1beta and activation of lung epithelial cells in CF lungs. Confluent layers of A549 cells, a type II-like human lung epithelial cell line, were incubated overnight with IL-1beta (0-5 ng/ml) or NE (100 nM), and supernatants were analyzed for IL-8 by enzyme-linked immunosorbent assay (ELISA). Both IL-1beta and NE led to a significant increase in IL-8: 12.8 +/- 2.8 ng/ml and 0.8 +/- 0.3 ng/ml, respectively. Next, bronchoalveolar lavage (BAL) samples were obtained from one healthy adult volunteer and six patients with CF and measured for IL-8 and IL-1beta concentrations by ELISA. Both IL-8 (range 169.00 +/- 56.57 to 1742.04 +/- 338.98 pg/ml) and IL-1beta (range 0-24.26 +/- 0.52 pg/ml) were detected in CF specimens, whereas neither was detected in the volunteer's specimen. Normal and CF BALs then were incubated overnight at a 1:10 dilution with confluent A549 cells. Analysis by ELISA of cell-free supernatants revealed increased IL-8 production from cells stimulated with CF BALs only. Similar experiments were performed with BAL supernatants that had been incubated with soluble IL-1 type II receptor, soluble IL-1 receptor antagonist, or a peptide inhibitor of NE. Addition of IL-1 inhibitors had a marginal effect on the amount of IL-8 release after incubation with CF BAL samples, whereas inhibition of NE had no effect. Our results indicate that other factors present in ELF in CF account for IL-8 release from lung epithelial cells.

Serial changes in surfactant-associated proteins in lung and serum before and after onset of ARDS

The goal of this study was to determine the changes that occur in surfactant-associated proteins in bronchoalveolar lavage fluid (BAL) and serum of patients at risk for ARDS and during the course of ARDS. We found that the concentrations of SP-A and SP-B were low in the BAL of patients at risk for ARDS before the onset of clinically defined lung injury, whereas the concentration of SP-D was normal. In patients with established ARDS, BAL SP-A and SP-B concentrations were low during the entire 14-d observation period, but the median SP-D concentrations remained in the normal range. Immunoreactive SP-A and SP-D were not increased in the serum of patients at risk for ARDS, but both increased after the onset of ARDS to a maximum on Day 3 and remained elevated for as long as 14 d. The BAL SP-A concentrations were significantly lower in at-risk patients who developed ARDS, and no patient with a BAL SP-A concentration greater than 1.2 microg/ml developed ARDS. On Days 1 and 3 of ARDS, the BAL SP-D concentration was significantly lower in patients who died, and the BAL SP-D concentration was significantly related to the PI(O(2))/FI(O(2)) ratio. Thus, surfactant protein abnormalities occur before and after the onset of ARDS, and the responses of SP-A, SP-B, and SP-D differ in important ways. The BAL SP-A and SP-D measurements can be used to classify patients as high or low risk for progression to ARDS and/or death after the onset of ARDS. Strategies to increase these surfactant proteins in the lungs of patients with ARDS could be useful to modify the onset or the course of ARDS.

Bronchopulmonary segmental lavage with Surfaxin (KL(4)-surfactant) for acute respiratory distress syndrome

We performed a trial to assess the safety and tolerability of sequential bronchopulmonary segmental lavage with a dilute synthetic surfactant (Surfaxin) in 12 adults with ARDS. Patients received one of three dosing regimens in which aliquots of Surfaxin were administered via a wedged bronchoscope to each of the 19 bronchopulmonary segments. Suctioning was performed 10-30 s after instillation of individual aliquots. Group 1 patients (n = 3) received one 30-ml aliquot of a 2.5-mg/ml concentration of Surfaxin in each segment, followed by a second 30-ml aliquot with a 10-mg/ml concentration. Group 2 patients (n = 4) received two 30-ml aliquots of the 2.5-mg/ml concentration followed by a third lavage with the 10-mg/ml concentration. Group 3 patients (n = 5) received therapy identical to that received by patients in Group 2 and were eligible for repeat dosing 6 to 24 h later. All patients tolerated the procedure. There were no serious adverse experiences ascribed to either the procedure or the surfactant. In the 96 h after treatment initiation, FI(O(2)) decreased from 0.80 to 0.52 and PEEP decreased from 10.3 to 7.6 cm H(2)O. Bronchoscopic "cleansing" of the lungs with dilute Surfaxin may offer a safe and feasible approach to improving outcomes in patients with ARDS. Wiswell TE, Smith RM, Katz LB, Mastroianni L, Wong DY, Willms D, Heard S, Wilson M, Hite RD, Anzueto A, Revak SD, Cochrane CG. Bronchopulmonary segmental lavage with Surfaxin (KL(4)-surfactant) for acute respiratory distress syndrome.

Effect of enteral feeding with eicosapentaenoic acid, gamma-linolenic acid, and antioxidants in patients with acute respiratory distress syndrome. Enteral Nutrition in ARDS Study Group

OBJECTIVES

Recent studies in animal models of sepsis-induced acute respiratory distress syndrome (ARDS) have shown that a low-carbohydrate, high-fat diet combining the anti-inflammatory and vasodilatory properties of eicosapentaenoic acid (EPA; fish oil), gamma-linolenic acid (GLA; borage oil) (EPA+GLA), and antioxidants improves lung microvascular permeability, oxygenation, and cardiopulmonary function and reduces proinflammatory eicosanoid synthesis and lung inflammation. These findings suggest that enteral nutrition with EPA+GLA and antioxidants may reduce pulmonary inflammation and may improve oxygenation and clinical outcomes in patients with ARDS.

DESIGN

Prospective, multicentered, double-blind, randomized controlled trial.

SETTING

Intensive care units of five academic and teaching hospitals in the United States.

PATIENTS

We enrolled 146 patients with ARDS (as defined by the American-European Consensus Conference) caused by sepsis/pneumonia, trauma, or aspiration injury in the study.

INTERVENTIONS

Patients meeting entry criteria were randomized and continuously tube-fed either EPA+GLA or an isonitrogenous, isocaloric standard diet at a minimum caloric delivery of 75% of basal energy expenditure x 1.3 for at least 4-7 days.

MEASUREMENTS AND MAIN RESULTS

Arterial blood gases were measured, and ventilator settings were recorded at baseline and study days 4 and 7 to enable calculation of PaO2/FIO2, a measure of gas exchange. Pulmonary neutrophil recruitment was assessed by measuring the number of neutrophils and the total cell count in bronchoalveolar lavage fluid at the same time points. Clinical outcomes were recorded. Baseline characteristics of 98 evaluable patients revealed that key demographic, physiologic, and ventilatory variables were similar at entry between both groups. Multiple bronchoalveolar lavages revealed significant decreases (approximately 2.5-fold) in the number of total cells and neutrophils per mL of recovered lavage fluid during the study with EPA+GLA compared with patients fed the control diet. Significant improvements in oxygenation (PaO2/FIO2) from baseline to study days 4 and 7 with lower ventilation variables (FIO2, positive end-expiratory pressure, and minute ventilation) occurred in patients fed EPA+GLA compared with controls. Patients fed EPA+GLA required significantly fewer days of ventilatory support (11 vs. 16.3 days; p = .011), and had a decreased length of stay in the intensive care unit (12.8 vs. 17.5 days; p = .016) compared with controls. Only four of 51 (8%) patients fed EPA+GLA vs. 13 of 47 (28%) control patients developed a new organ failure during the study (p = .015).

CONCLUSIONS

The beneficial effects of the EPA+GLA diet on pulmonary neutrophil recruitment, gas exchange, requirement for mechanical ventilation, length of intensive care unit stay, and the reduction of new organ failures suggest that this enteral nutrition formula would be a useful adjuvant therapy in the clinical management of patients with or at risk of developing ARDS.

Quality assessment through patient self-report of symptoms prefiberoptic and postfiberoptic bronchoscopy

STUDY OBJECTIVE

To apply the principles of quality improvement to measure the frequency and severity of symptoms that result from fiberoptic bronchoscopy (FOB), and to identify opportunities to improve FOB practice by identifying factors about patients and the process of care that predict these symptoms.

DESIGN

Concurrent longitudinal cohort study.

PATIENTS

Four hundred ninety-three adult patients who underwent FOB.

MEASUREMENTS AND RESULTS

Patients completed questionnaires just prior to FOB and again at 48 h postprocedure. Patients were asked to rate the severity of nose pain, throat pain, swallowing pain, and chest pain, and the frequency of coughing, hemoptysis, phlegm, shortness of breath, wheezing, difficulty swallowing, fever, and chills. Symptom severity was reported on a four-point ordinal scale.

FINDINGS

Significant worsening was found for nose pain, throat pain, swallowing pain, and hemoptysis. Shorter patients experienced more throat pain and hemoptysis, and longer procedure time predicted nose pain and hemoptysis.

CONCLUSIONS

Bronchoscopy causes nose pain, throat pain, swallowing pain, and hemoptysis to a larger extent than previously has been recognized. There are opportunities to improve the patient experience with bronchoscopy by using smaller bronchoscopes in shorter patients, shortening the procedure length, and reanesthetizing the nares in longer procedures.

Invasive diagnostic techniques for pneumonia: protected specimen brush, bronchoalveolar lavage, and lung biopsy methods

We suggest the following strategy for managing patients with pneumonia. For nonventilated patients with either CAP or HAP, empiric antibiotic treatment should be started according to approved guidelines, and if the clinical evolution of the patient is not adequate, fiberoptic bronchoscopy including PSB and BAL could be considered, with modification of the antibiotic treatment accordingly. In ventilated patients with either CAP or HAP, respiratory secretion sampling using noninvasive techniques should be conducted upon clinical suspicion of VAP and before starting a new antibiotic treatment. Antibiotic therapy according to approved guidelines should be started as soon as possible and maintained during the first 48 hours if the patient's evolution is satisfactory and condition has stabilized. Then, initial antibiotic treatment should be adjusted according to cultures. If there is a clear diagnostic alternative to VAP and cultures are negative, this is the only case in which antibiotic treatment could be withdrawn. If the patient's clinical evolution is inadequate (persistence of fever, leukocytosis, increasing infiltrates, and respiratory failure), fiberoptic bronchoscopy with PSB and BAL and modification of the initial antibiotic regimen should be sought. Open lung biopsy may be indicated in patients with diffuse pulmonary infiltrates in whom a diagnosis has not been achieved by other methods, including bronchoscopy. Transbronchial lung biopsy should not be viewed as a diagnostic technique for pneumonia except in immunosuppressed patients with diffuse alveolar infiltrates.

Elevated transforming growth factor-alpha levels in bronchoalveolar lavage fluid of patients with acute respiratory distress syndrome

The acute respiratory distress syndrome (ARDS) frequently results in a fibroproliferative response that precludes effective alveolar repair. Transforming growth factor-alpha (TGF-alpha), a potent epithelial and mesenchymal cell mitogen, may modulate the response to lung injury. In this study, we determined whether bronchoalveolar lavage fluid (BALF) concentrations of TGF-alpha are increased during the first 2 wk after the onset of ARDS and, if so, whether increased TGF-alpha levels in lavage fluid are associated with increased levels of procollagen peptide III (PCP III), a biological marker of fibroproliferation, and with increased fatality rates. We enrolled 74 consecutive patients with ARDS prospectively identified on admission to the intensive care unit of a tertiary care hospital, and 11 patients with chronic interstitial lung disease. Thirteen healthy volunteers served as control subjects. TGF-alpha concentrations were measured in BALF recovered on Days 3, 7, and 14 after the onset of ARDS (total of 130 lavage samples). TGF-alpha was detected in the lavage fluid of 90% of patients with ARDS (67 of 74), and in 100% of patients with idiopathic pulmonary fibrosis (IPF) (10 of 10), but in none of 13 normal volunteers. At each day tested, the median lavage TGF-alpha level of patients with ARDS was significantly higher than that of normals. The overall fatality rate was 45% (33 of 74 patients). In a univariate analysis, the median TGF-alpha levels in nonsurvivors were 1.5-fold higher at Day 7 (p = 0.06) and 1.8-fold higher at Day 14 (p = 0.048). The fatality rate was 4 times higher (CI 1.6, 17.5) for patients with both increased lavage TGF-alpha and PCP III concentrations at Day 7 than for patients with low TGF-alpha and PCP III values, indicating a synergistic relationship between TGF-alpha and PCP III. We conclude that increased levels of TGF-alpha in BALF are common in patients with ARDS and that lavage TGF-alpha is associated with a marker of the fibroproliferative response in sustained ARDS.

Neutrophil apoptosis in the acute respiratory distress syndrome

Little is known about neutrophil (PMN) apoptosis in the acute respiratory distress syndrome (ARDS). We uses morphologic criteria to count apoptotic PMN in bronchoalveolar lavage fluid (BAL) of 35 patients on Days 1, 3, 7, 14, and 21 of ARDS and 13 patients on Days 1 and 3 of risk for ARDS. We found that the proportion of apoptotic PMN in BAL was low throughout the course of ARDS. There was no significant difference between the percentage of apoptotic PMN in patients at risk and patients with established ARDS or between patients who lived (2.4%) and patients who died (1.8%). When normal human PMN were incubated in ARDS BAL, a significantly lower proportion became apoptotic (50 +/- 4%), as compared with PMN incubated in lavage fluid from normal volunteers (76 +/- 7%, p < 0.05). This antiapoptotic effect of ARDS BAL was blocked by immunodepleting BAL of G-CSF and GM-CSF. We conclude that the proportion of apoptotic PMN recovered from the lungs of patients with ARDS is low throughout the course of ARD S. Furthermore, BAL from patients with ARDS prolongs survival of normal human PMN in vitro, and this effect is partially mediated by G-CSF and GM-CSF.

Safety and yield of transbronchial biopsy in mechanically ventilated patients

OBJECTIVE

To evaluate the safety and diagnostic yield of transbronchial biopsy performed in mechanically ventilated patients.

DESIGN

Retrospective, cohort analysis.

SETTING

A university-affiliated teaching hospital.

PATIENTS

Seventy-one consecutive, mechanically ventilated patients requiring lung tissue examination.

INTERVENTIONS

Transbronchial lung biopsy.

MEASUREMENTS AND MAIN RESULTS

We evaluated complications associated with transbronchial biopsy, diagnostic yield of the procedure, and changes in patient management based on the results of the transbronchial lung biopsies. Eighty-three transbronchial lung biopsy procedures were performed in this patient cohort. Complications associated with these procedures included the following: ten (14.3%) pneumothoraces in patients without preexisting chest tubes; five (6.0%) episodes of bronchial hemorrhage of > 30 mL; transient oxygen desaturation to < 90% in seven (8.4%) patients; hypotension with a mean arterial pressure of < 60 mm Hg in six (7.2%) patients; and three (3.6%) episodes of tachycardia, with a heart rate of > 140 beats/min. No patient deaths, episodes of pneumonia, or sepsis could be attributed to the transbronchial lung biopsy procedures. Specific histologic diagnoses were made with 29 (34.9%) of the transbronchial biopsies, and patient management was changed as a direct result of the lung tissue examination in 34 (41.0%) instances. Pathologic correlation between the transbronchial biopsy specimens and lung tissue obtained by open-lung biopsy or post mortem examination occurred in 11 (84.6%) of 13 paired samples.

CONCLUSION

Transbronchial lung biopsy can be performed with an acceptable risk and reasonable diagnostic yield in certain types of mechanically ventilated patients, often obviating the need to perform open-lung biopsy.

Complications of mechanical ventilation. A bedside approach

Instead of cataloging complications reported to occur during mechanical ventilation, the authors have discussed the potential causes for several common scenarios in the management of ventilated patients. These include the new development of hypotension, acute respiratory distress (fighting the ventilator), repeated sounding of the ventilator's high-pressure alarm, hypoxemia, blood from the endotracheal tube, and the problem of diagnosing VAP. In the course of considering likely explanations for this group of circumstances for which the clinician is consulted or called to the bedside, virtually all reported ventilator-associated complications must be discussed. This new approach to an important aspect of ICU care may aid in clinical problem-solving and reduce the likelihood that a diagnosis will be missed or inappropriate measures taken in the absence of a systematic, pathophysiology-based approach.

Nuclear factor-kappa B is activated in alveolar macrophages from patients with acute respiratory distress syndrome

OBJECTIVE

The expression of proinflammatory cytokines is rapidly increased in experimental models of the acute respiratory distress syndrome (ARDS), in patients at risk for ARDS, and in patients with established ARDS. Because multiple cytokines are present in bronchoalveolar lavage fluid, a common, proximal activation mechanism may operate in these settings. The proinflammatory cytokines whose expression is increased in the lungs of patients with ARDS have binding sequences in their enhancer/promoter regions for transcriptional regulatory proteins, such as nuclear factor-kappa B (NF-kappa B), nuclear factor-IL6 (NF-IL6), cyclic adenosine monophosphate responsive element binding protein, serum protein-1, and activating protein-1. To test the hypothesis that activation of one or more of these nuclear transcriptional regulatory factors might provide a common mechanism for the simultaneous expression of multiple cytokine genes in the setting of ARDS, we measured activation of these factors in alveolar macrophages from patients with ARDS and from controls.

DESIGN

Prospective, clinical study.

SETTING

Medical and surgical intensive care units at a university hospital and a county hospital.

PATIENTS

Twelve patients, six with established ARDS and six control patients without lung injury.

INTERVENTIONS

Patients with ARDS and controls underwent fiberoptic bronchoscopy and bronchoalveolar lavage. Alveolar macrophages were isolated from lavage fluid and the nuclear proteins were extracted. Activation of transcriptional factors NF-kappa B, NF-IL6, cyclic adenosine monophosphate responsive element binding protein, activating protein-1, and serum protein-1 was determined using an electrophoretic mobility shift assay, followed by densitometry of the autoradiographed gels.

MEASUREMENTS AND MAIN RESULTS

There were no significant differences in gender, age, tobacco smoking, Acute Physiology and Chronic Health Evaluation II score, quantity of lavage fluid, or number of alveolar macrophages in lavage specimens in the patient groups. Acute Lung Injury score and the Pao2/Fio2 ratio differed significantly between controls and ARDS patients: 0.46 +/- 0.17 vs. 2.74 +/- 0.14 (p < .0001) and 310 +/- 45 torr (41.3 +/- 6.0 kPa) vs. 150 +/- 11 torr (21.3 +/- 1.5 kPa) (p < .006), respectively. The mean Fio2 of the control patients was not significantly different from the mean Fio2 of ARDS patients: 0.47 +/- 0.11 vs. 0.55 +/- 0.6 (p = .53). Patients with ARDS had significantly (p < .02) increased activation of NF-kappa B in alveolar macrophages compared with patients without the syndrome. There was no evidence of increased activation of the transcriptional factors activating protein-1, serum protein-1, NF-IL6, or cyclic adenosine monophosphate responsive element binding protein in alveolar macrophages from ARDS vs. control patients.

CONCLUSIONS

These experiments demonstrated increased in vivo activation of the nuclear transcriptional regulatory factor NF-kappa B (but not NF-IL6, cyclic adenosine monophosphate responsive element binding protein, activating protein-1, or serum protein-1) in alveolar macrophages from patients with ARDS. Because binding sequences for NF-kappa B are present in the enhancer/promoter sequences of multiple proinflammatory cytokines, activation of NF-kappa B may contribute to the increased expression of multiple cytokines in the lung in the setting of established ARDS.

Usefulness of airway visualization in the diagnosis of nosocomial pneumonia in ventilated patients

Clinical diagnosis of nosocomial pneumonia in ventilated patients remains a challenge in the ICU as none of the clinical biological and radiologic parameters can predict its diagnosis. To our knowledge, however, the accuracy of direct visualization of the bronchial tree has never been investigated.

PURPOSE

To evaluate the interest of airway visualization and to select independent parameters that predict nosocomial pneumonia in ventilated patients.

SETTING

A ten-bed medical-surgical ICU.

METHODS

All consecutive patients suspected of having nosocomial pneumonia who underwent bronchoscopy with protected specimen brush, culture examination of BAL, and direct examination of BAL were studied. Clinical and biological data and airways findings were recorded prospectively. Patients were classified as having pneumonia or not according to the results of distal bacteriologic samples, follow-up, and histologic study. Respective accuracies of each variable were calculated using univariate analysis and stepwise logistic regression.

RESULTS

Ninety-one patients with suspected nosocomial pneumonia were studied. Patients were randomly assigned to a construction group (n = 46) and a validation group (n = 45). Using multivariate analysis, 3 factors were associated with pneumonia (a decrease in PaO2/fraction of inspired oxygen ratio > or = 50 mm Hg, odds ratio [OR] = 9.97, p = 0.026; the presence of distal purulent secretions, OR = 7.46, p = 0.044; the persistence of distal secretions surging from distal bronchi during exhalation, OR = 12.25, p = 0.013). These three factors remained associated with pneumonia in the validation group. Interobserver repeatability of the bronchoscopic parameters was good. Having 2 or more of these 3 independent factors was able to predict pneumonia with a 94% sensitivity and a 89% specificity in the construction group and with a 78% sensitivity and a 89% specificity in the validation group.

CONCLUSION

We conclude that direct visualization of the bronchial tree can immediately and accurately predict nosocomial pneumonia in ventilated patients before obtaining definite results of protected samples.

Acute respiratory distress syndrome

The acute respiratory distress syndrome (ARDS) is a serious and complex clinical problem that often threatens the lives of patients. Emerging clinical data suggest that the survival of patients with this disorder may have improved during the last two decades, presumably because of advances in supportive medical care. Among the supportive therapies used to treat patients with ARDS, none is more complex than mechanical ventilation. New strategies for administering mechanical ventilation to patients with ARDS may reduce the occurrence of iatrogenic volotrauma and oxygen toxicity, accounting in part for the recently observed improvements in patient survival. Prevention and cure of ARDS have remained elusive goals because of the lack of specific therapies directed against the known pathogenic factors. Ongoing investigations are aimed at identifying specific therapies to interrupt the mechanisms of inflammation and lung injury responsible for this syndrome. Until such therapies become available, clinicians caring for patients with ARDS should attempt to minimize additional morbidity and mortality resulting from nosocomial infections and iatrogenic injuries.

Relationship between pulmonary oxygen consumption, lung inflammation, and calculated venous admixture in patients with acute lung injury

OBJECTIVE

To determine in patients with acute lung injury whether increased pulmonary oxygen consumption (VO2pulm), computed as the difference between oxygen consumption measured by indirect calorimetry (VO2meas) and calculated by the reverse Fick method (VO2Fick), would: (1) correlate with the degree of lung inflammation assessed by bronchoalveolar lavage (BAL); (2) lead to an overestimation of calculated venous admixture (Qva/Qt).

DESIGN

Prospective study.

SETTING

University hospital, medical intensive care unit.

INTERVENTION

None.

MEASUREMENTS AND RESULTS

In nine mechanically ventilated patients with acute lung injury (Apache II 12 +/- 5, lung injury score 2 +/- 0.6, mean +/- SD), whole-body VO2 (VO2wb) was determined simultaneously by indirect calorimetry and the reverse Fick technique, after which BAL was immediately performed. VO2meas was significantly higher than VO2Fick (128 +/- 24 and 102 +/- 18 ml/min per m2, respectively, p < 0.001). Median VO2pulm was 25.3 ml/min per m2 (range 1.98-51.5), thus representing 19 +/- 11% of VO2wb. Total BAL cellularity was increased in all patients (median 47, range 24-200 x 10(4)/ml), as was the total polymorphonuclear (PMN) count (median 78 range 5-93 x 10(4)/ml). Macrophage counts were in the normal range. There were raised BAL levels of interleukin-6 (IL-6) (median 945, range 23-1800 ng/ml) and elastase (median 391, range 5-949 ng/ml). Median protein levels were 270 micrograms/ml (range 50-505). There was no correlation between VO2pulm and BAL cellularity, PMNs, elastase, IL-6, or protein. Qva/Qt was 31.7 +/- 8%. Qva/Qt, corrected for the presence of VO2pulm, (Qva/Qtcorr), was 30.3 +/- 8% (P < 0.01 vs Qva/Qt), a 4.2% overestimation due to VO2plum. There was no correlation between Qva/Qt or Qva/Qtcorr and VO2pulm.

CONCLUSIONS

In mechanically ventilated patients with acute lung injury, VO2pulm was increased and led to a 19% underestimation of VO2wb determined by the reverse Fick method, as well as to a 4.2% overestimation of calculated Qva/Qt. Lung inflammatory activity was increased, as assessed by BAL cellularity, IL-6 and elastase levels. However, there was no correlation between VO2pulm and the intensity of pulmonary inflammation.

Clinical diagnostic criteria of the adult respiratory distress syndrome in the intensive care unit

OBJECTIVES

To determine the use of commonly used diagnostic criteria for adult/acute respiratory distress syndrome (ARDS), evaluate physiologic variables of most value in diagnosing ARDS, and assess the frequency of newly diagnosed ARDS.

DESIGN

Self-administered questionnaire by mail.

SETTING

Hospital intensive care units (ICUs).

SUBJECTS

Intensive care physicians (n = 923) in the United States listed as ICU directors in the Society of Critical Care Medicine Membership Directory.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

A total of 448 (48.5%) physicians responded, with 301 questionnaires completed. Bilateral infiltrates on chest radiograph, the PaO2/FIO2 ratio, and pulmonary artery occlusion pressure were the most commonly used diagnostic criteria. However, the actual values used to diagnose ARDS were highly variable. The most important clinical physiologic variable used in determining the respiratory status of the ARDS patient was the PaO2/FIO2 ratio, followed by shunt fraction, alveolar-arterial oxygen tension gradient, FIO2, PaO2, respiratory system compliance, and minute ventilation. Respondents indicated that 9% of ICU beds at their institutions were occupied by a patient diagnosed with ARDS within the previous 7 days and 18.6% of all mechanically ventilated patients had ARDS by their own criteria. Based on the total number of ICU beds, the predicted incidence of ARDS would be approximately 275,000 patients per year in the United States.

CONCLUSION

A wide range of diagnostic criteria are utilized by clinicians in the diagnosis of ARDS.

Adult and paediatric size bronchoscopes for bronchoalveolar lavage in mechanically ventilated patients: yield and side effects

BACKGROUND

Bronchoalveolar lavage is considered a safe procedure. When performed in the mechanically ventilated patient, however, potentially harmful effects on respiratory and haemodynamic functions have been reported in which the size of the bronchoscope may play a part. Two different size bronchoscopes (adult and paediatric) were therefore investigated with regard to bronchoalveolar lavage yield and side effects.

METHODS

Twenty mechanically ventilated patients underwent bronchoalveolar lavage with both adult and paediatric bronchoscopes in a randomised sequential manner.

RESULTS

In a total of 45 pairs of bronchoalveolar lavage procedures no difference was noted between adult and paediatric bronchoscopes with regard to total cell yield, differential cell count, and microbiological results. Peak intratracheal pressure increased with the adult bronchoscope only. Systemic arterial pressures increased more with the adult than with the paediatric bronchoscope. PaO2 decreased with the adult but not with the paediatric bronchoscope.

CONCLUSIONS

The paediatric bronchoscope offers a comparable bronchoalveolar lavage yield in mechanically ventilated patients to the adult bronchoscope, while the respiratory and haemodynamic side effects are significantly lower than with the adult size instrument.

The acute respiratory distress syndrome

ARDS is a complex response of the lung to direct (inhalational) and indirect (hematogenous) insults. It is easy to be pessimistic about the benefit of the approaches we have described, but there is evidence that overall survival has improved in recent years. To maintain this progress, new therapies for ARDS must be rigorously evaluated, and their routine use should be recommended only after careful scrutiny of the evidence. Such a course will eliminate the unnecessary risks and costs often associated with unproved therapies.

Bronchoscopic diagnosis of pneumonia

Lower respiratory tract infections are characterized by significant morbidity and mortality but also by a relative inability to establish a specific etiologic agent on clinical grounds alone. With the recognized shortcomings of expectorated or aspirated secretions toward establishing an etiologic diagnosis, clinicians have increasingly used bronchoscopy to obtain diagnostic samples. A variety of specimen types may be obtained, including bronchial washes or brushes, protected specimen brushings, bronchoalveolar lavage, and transbronchial biopsies. Bronchoscopy has been applied in three primary clinical settings, including the immunocompromised host, especially human immunodeficiency virus-infected and organ transplant patients; ventilator-associated pneumonia; and severe, nonresolving community- or hospital-acquired pneumonia in nonventilated patients. In each clinical setting, and for each specimen type, specific laboratory protocols are required to provide maximal information. These protocols should provide for the use of a variety of rapid microscopic and quantitative culture techniques and the use of a variety of specific stains and selective culture to detect unusual organism groups.

New approaches in the diagnosis of nosocomial pneumonia

We have presented a review of the present literature on new modalities to diagnose nosocomial pneumonia. Procedures are now available that, when correctly used, can establish a diagnosis of pneumonia with a high degree of reliability. In our institution, reliance on bronchoscopic modalities has simplified management of patients with suspected VAP, by eliminating confusion and rationalizing antibiotic treatment. Invasive procedures, however, should be performed only if the results of cultures are consistently applied to treatment. As this field rapidly evolves, we hope that this review will provide the reader with a foundation to understand new developments.