Comparison of nonbronchoscopic bronchoalveolar lavage to open lung biopsy for the bacteriologic diagnosis of pulmonary infections in mechanically ventilated patients

The role of mini-bronchoalveolar lavage fluid in the diagnosis of pulmonary tuberculosis in critically ill patients

BACKGROUND

The detection of Mycobacterium tuberculosis (MTB) in the intensive care unit (ICU) presents several challenges, mainly associated to the clinical state of the patient. The presence of HIV infection further aggravates this scenario, requiring a reliable collection method, with better performance in the microbiological/molecular techniques to be used. We evaluated the performance of two methods for sample collection, mini bronchoalveolar lavage (Mini-BAL) and endotracheal aspirate (ETA), for diagnosis of pulmonary tuberculosis (PTB) in critically ill patients.

METHODS

This prospective study involved 26 HIV positive ICU internalized patients, with presumptive PTB who required mechanical ventilation. Two samples were obtained prospectively from 26 HIV ICU patients with presumptive PTB by Mini-BAL and ETA. The samples were processed for smear microscopy, Löwenstein-Jensen medium and the BACTEC Mycobacteria Growth Indicator Tube 960 system®. We define as confirmed PTB patients with positive MTB culture. Furthermore, all samples obtained through the Mini-BAL were analyzed by Xpert® MTB/RIF.

RESULTS

Our results demonstrated that the respiratory samples obtained by Mini-BAL were able to increase MTB detection in critically ill patients with presumptive PTB. The Mini-BAL allowed 30% increased recovery and guaranteed enough sample volume for processing in all methods. In addition, the larger volume of the samples obtained with this technique enabled the Xpert® MTB/RIF molecular test for diagnosis of TB.

CONCLUSIONS

The Mini-BAL showed be an acceptable alternative to ETA in this population, since these critically ill and often-immunocompromised patients are more likely to develop complications related to invasive procedures.

Surgical Lung Biopsy for Interstitial Lung Diseases

This review addresses common questions regarding the role of surgical lung biopsy (SLB) in the diagnosis and treatment of interstitial lung disease (ILD). We specifically address when a SLB can be diagnostic as well as when it may be avoided; for example, when the combination of the clinical context and the imaging pattern seen on high-resolution CT (HRCT) chest scans can provide a confident diagnosis. Existing studies on the diagnostic utility as well as the complications associated with SLB are reviewed; also reviewed are the performance characteristics and reliability of HRCT scans of the chest in predicting the underlying histopathologic findings of the lung. The review is formatted in the form of answers to questions that clinicians regularly ask when considering an SLB in a patient with ILD.

The Utility of Open Lung Biopsy in Patients With Diffuse Pulmonary Infiltrates as Related to Respiratory Distress, Its Impact on Decision Making by Urgent Intervention, and the Diagnostic Accuracy Based on the Biopsy Location

Patients with diffuse pulmonary infiltrates (DPI), especially those who present with respiratory distress (RD), may benefit from early open lung biopsy (OLB) to guide management. Benefits of urgent OLB would be expected by saving the time to reach accurate specific diagnoses. The objectives of this study were (1) to evaluate the impact of OLB between patients presenting with and without RD, (2) to focus on the impact of an urgent OLB as compared to an elective OLB, and (3) to compare the different yields of specific diagnoses in the middle lobe or lingula as compared to the other lobes. Thirty-four patients (17 patients presented with RD and 17 patients did not) with an average age of 43 years who presented with DPI were selected to undergo an OLB. An urgent OLB was performed in 11unselected patients. Twelve specimens from the middle lobe or lingula were compared to 25 specimens from the other lobes. The impact of the OLB results on decision making did not differ significantly between patients with and without RD. Patients with RD suffered a higher in-hospital mortality rate, OLB-related complications, and longer mechanical ventilation requirements than the patients without RD. The impact on decision making and complications between urgent OLB and elective OLB was comparable. The diagnostic yield from biopsy sites in the middle lobe or lingula resembled those specimens from the other lobes. The authors conclude that OLB may play a role in decision making for patients with DPI. However, OLB makes no difference in decision making between patients with and without RD. Patients with RD undergoing OLB procedures may suffer a poorer outcome. Urgent OLB may not benefit patients with DPI in decision making. The biopsy site does not appear to affect the accuracy of the diagnostic yield from an OLB procedure.

Diagnosis of ventilator-associated pneumonia in children in resource-limited setting: a comparative study of bronchoscopic and nonbronchoscopic methods

OBJECTIVES

To compare the available methods for the diagnosis of ventilator-associated pneumonia in intubated pediatric patients and to suggest less costly diagnostic method for developing countries.

DESIGN

Prospective study.

SETTING

Pediatric intensive care unit of a tertiary care, multidisciplinary teaching hospital located in northern India.

PATIENTS

All consecutive patients on mechanical ventilation for >48 hrs were evaluated clinically for ventilator-associated pneumonia.

INTERVENTIONS

Four diagnostic procedures (tracheal aspiration, blind bronchial sampling, blind bronchoalveolar lavage, and bronchoscopic bronchoalveolar lavage) were performed in the same sequence within 12 hrs of clinical suspicion of ventilator-associated pneumonia. The bacterial density > or =104 colony-forming units/mL in a bronchoscopic bronchoalveolar lavage sample was taken as reference standard.

MEASUREMENTS AND MAIN RESULTS

Thirty patients with 40 episodes of ventilator-associated pneumonia were included in the study. Tracheal aspirate at the cutoff of > or =105 colony-forming units/mL was found to have sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of 84%, 77%, 87.5%, 73%, and 80%, respectively. For blind bronchial sampling at > or =104 colony-forming units/mL cutoff, the sensitivity, specificity, positive predictive value, negative predictive value, and accuracy were 88%, 82%, 88%, 83%, and 87%, respectively; the most reliable results were obtained with blind bronchoalveolar lavage at the cutoff of > or =103 cfu/mL (sensitivity 96%, specificity 80%, positive predictive value 88%, negative predictive value 92%, and accuracy 90%). The area under the receiver operating characteristic curve of tracheal aspiration, blind bronchial sampling, and blind bronchoalveolar lavage was 0.87 +/- 0.06, 0.89 +/- 0.06, and 0.89 +/- 0.05, respectively. The cost of balloon-tip pressure catheter used for blind bronchoalveolar lavage was INR 1600.00 (US$40) whereas that for blind bronchial sampling was only INR 35.00 (<1 US$).

CONCLUSIONS

Blind bronchoalveolar lavage was the most reliable method followed closely by blind bronchial sampling for the diagnosis of ventilator-associated pneumonia. Considering the difference of the cost in the two procedures, blind bronchial sampling may be the preferred method in the pediatric intensive care unit of a developing country.

Ventilator-associated pneumonia in a paediatric intensive care unit in a developing country with high HIV prevalence

AIM

To obtain preliminary prevalence, aetiological and outcome data on South African paediatric patients with ventilator-associated pneumonia (VAP).

METHODS

Non-bronchoscopic bronchoalveolar lavage (BAL) specimens taken between January 2004 and September 2005 were prospectively recorded and related clinical data were retrospectively reviewed. VAP was defined as a new isolate on BAL and a modified Clinical Pulmonary Infection Score > or =5.

RESULTS

A total of 230 patients aged 3.9 (2.2-9.1) months (median interquartile range (IQR) ) underwent 309 BALs during 244 paediatric intensive care unit (PICU) admissions. Most patients (84%) were admitted with acute infectious diseases, with a 70% incidence of comorbidity. Thirty-three patients (14.3%) were HIV-exposed but uninfected and 58 (25.2%) were HIV-infected. Of 172 BALs taken > or =48 h after intubation, 63 specimens from 55 patients fulfilled VAP criteria. Acinetobacter baumannii was the most common VAP pathogen, followed by Klebsiella pneumoniae, viruses, yeasts and Staphylococcus aureus. Patients who developed VAP had a higher proportion of comorbid conditions (76% vs. 55%, P= 0.01) and reintubations (39% vs. 12%, P < 0.0001) when compared with non-VAP patients. Median (IQR) length of PICU stay was 12.5 (5-21) days versus 8 (5-14) days (P= 0.03); and the risk adjusted PICU mortality was 1.38 versus 0.79 (P= 0.002) in VAP versus non-VAP patients, respectively.

CONCLUSIONS

VAP is associated with significant morbidity and mortality and may relate to the high incidence of comorbid conditions in this population. Primary VAP pathogens differ from developed countries.

Diagnosis of ventilator-associated pneumonia: focus on nonbronchoscopic techniques (nonbronchoscopic bronchoalveolar lavage, including mini-BAL, blinded protected specimen brush, and blinded bronchial sampling) and endotracheal aspirates

The ideal diagnostic approach for ventilator-associated pneumonia currently is based on invasive procedures to obtain respiratory tract cultures. Given the lack of consensus and relatively poor acceptance of full bronchoscopic bronchoalveolar lavage (BAL) and protected specimen brush (PSB), less invasive procedures have been developed. We review the nonbronchoscopic procedures (nonbronchoscopic bronchoalveolar lavage, including mini-BAL, blinded protected specimen, and blinded bronchial sampling) and endotracheal aspiration. We provide a critique of the methods used, the types of catheters inserted, and the sample collection methods. Most studies were flawed in that antibiotic use before initiation of the procedure was not controlled. The variability of both the methods and the criteria for the gold standard in the numerous investigations show that these procedures are neither standardized nor proven to be accurate and often did not improve management. Pending future studies, use of endotracheal aspirates without the use of quantitation seems to be a reasonable approach for clinicians who are not committed to an invasive procedure.

Reproducibility of blind protected bronchoalveolar lavage in mechanically ventilated children

Blind protected bronchoalveolar lavage (BAL) could be an interesting tool in the diagnosis of ventilator-associated pneumonia in intubated children, but its reproducibility has never been evaluated. This study evaluates the reproducibility, feasibility, and safety of blind protected BAL in mechanically ventilated children. Two blind protected BAL were done, at a 2-hour interval, in 30 patients. The reproducibility of microbiologic and cytologic results was studied. A total of 60 BALs was analyzed. Bacterial growth was present in 26 of 60 BAL (43%). Reproducibility for the presence of bacteria on quantitative cultures was excellent (concordance, 93%; kappa [kappa], 0.86). Concordance for the type of bacteria isolated was 86% and for the number of bacteria was 79%. Reproducibility for the presence of neutrophils containing bacteria was perfect (concordance, 100%; kappa, 1) although only a few BALs had a positive result (8/60). Blind protected BAL was feasible in all patients and all samples were considered adequate for analysis. Complications were mostly benign and transitory except in two cases: one pneumothorax and one significant increase in intracranial pressure. Overall, blind protected BAL is a reproducible test in mechanically ventilated children, is easily feasible, and is usually well tolerated.

Ventilator-associated pneumonia

Ventilator-associated pneumonia (VAP) continues to complicate the course of 8 to 28% of patients receiving mechanical ventilation (MV). In contrast to infections of more frequently involved organs (e.g., urinary tract and skin), for which mortality is low, ranging from 1 to 4%, the mortality rate for VAP ranges from 24 to 50% and can reach 76% in some specific settings or when lung infection is caused by high-risk pathogens. The predominant organisms responsible for infection are Staphylococcus aureus, Pseudomonas aeruginosa, and Enterobacteriaceae, but etiologic agents widely differ according to the population of patients in an intensive care unit, duration of hospital stay, and prior antimicrobial therapy. Because appropriate antimicrobial treatment of patients with VAP significantly improves outcome, more rapid identification of infected patients and accurate selection of antimicrobial agents represent important clinical goals. Our personal bias is that using bronchoscopic techniques to obtain protected brush and bronchoalveolar lavage specimens from the affected area in the lung permits physicians to devise a therapeutic strategy that is superior to one based only on clinical evaluation. When fiberoptic bronchoscopy is not available to physicians treating patients clinically suspected of having VAP, we recommend using either a simplified nonbronchoscopic diagnostic procedure or following a strategy in which decisions regarding antibiotic therapy are based on a clinical score constructed from seven variables. Selection of the initial antimicrobial therapy should be based on predominant flora responsible for VAP at each institution, clinical setting, information provided by direct examination of pulmonary secretions, and intrinsic antibacterial activities of antimicrobial agents and their pharmacokinetic characteristics. Further trials will be needed to clarify the optimal duration of treatment and the circumstances in which monotherapy can be safely used.

Non-bronchoscopic bronchoalveolar lavage in the microbiological diagnosis of pneumonia in mechanically ventilated patients

A prospective study comparing standardized non-bronchoscopic bronchoalveolar lavage (sNB-BAL) and non-specific endotracheal aspirate (NsETA) in the microbiological diagnosis of pneumonia in mechanically ventilated patients is described. One hundred episodes in 82 mechanically ventilated patients with or without radiological and clinical diagnostic criteria of pneumonia were studied. NsETA and sNB-BAL was performed on the day of study. Fifty-one patients had pneumonia (21 ventilator-associated, 12 hospital-acquired, 18 community-acquired) and 49 had no pneumonia as defined by widely accepted clinico-radiological criteria. The sNB-BAL was found to be significantly more specific (0. 73) compared to NsETA (0.35) for the microbiological diagnosis of pneumonia. Colonization rates with NsETA were significantly higher compared to sNB-BAL (P value <0.0001). No patient had complications attributable to the sNB-BAL procedure. We conlude that sNB-BAL is a safe, effective, sensitive, specific and inexpensive procedure for the serial evaluation of pneumonia in mechanically ventilated patients.

Microbial investigation in ventilator-associated pneumonia

Ventilator-associated pneumonia (VAP) is a serious infectious condition in intensive care unit (ICU) patients, currently related to a high mortality rate. Therefore, this complication of mechanical ventilation requires a prompt diagnosis and adequate antibiotic treatment. The detection of the causative organism is imperative for guiding an appropriate therapy as there is strong evidence of the adverse effect of inadequate empirical treatment on outcome. The major difficulty of the microbial investigation is to obtain the sample from the lower respiratory tract, mainly because of the potential contamination with upper airways flora, which may result in a misinterpretation of the cultures. Microbial investigation in VAP is based on the culture of samples obtained from lower respiratory tract by noninvasive or invasive methods. The most common techniques of sampling are the endotracheal aspirate (ETA), which is considered a noninvasive method, the protected specimen brush (PSB) and the bronchoalveolar lavage (BAL), both being invasive methods of investigation. The latter were designed as an attempt to avoid the colonizing flora of the upper airways. The best of these diagnostic approaches is still controversial. In terms of outcome, there is strong evidence that the impact of both invasive and noninvasive methods seems to be similar. In terms of cost, however, the endotracheal aspirate is less expensive compared to BAL or PSB. On the other hand, invasive methods could be particularly beneficial in patients who are not responding to the initial empirical antibiotic treatment. The rationale for the quantitative culture of the respiratory samples is to differentiate between infection and colonization of lower airways, because the bacterial colonization is a frequent event in mechanically ventilated patients. The thresholds currently employed for the diagnosis of the pneumonia are the following: ETA samples, > or = 10(5)-10(6) colony forming units (cfu).mL(-1); PSB samples, > or =10(3) cfu.mL(-1); and BAL samples, > or =10(4) cfu.mL(-1). Intending to provide a practical approach to the issue, the present manuscript reviews the available noninvasive (blood culture, endotracheal aspirate) and invasive (protected specimen brush, bronchoalveolar lavage, blinded methods and lung biopsy) techniques used for the diagnosis of ventilator-associated pneumonia.

Ventilator-associated pneumonia or not? Contemporary diagnosis

Ventilator-associated pneumonia (VAP) is pneumonia in patients who have been on mechanical ventilation for > or =48 hours. VAP is most accurately diagnosed by quantitative culture and microscopy examination of lower respiratory tract secretions, which are best obtained by bronchoscopically directed techniques such as the protected specimen brush and bronchoalveolar lavage. These techniques have acceptable repeatability, and interpretation of results is unaffected by antibiotics administered concurrently for infection at extrapulmonary sites as long as antimicrobial therapy has not been changed for <72 hours before bronchoscopy.

Nosocomial pneumonia. Diagnostic and therapeutic considerations

Many patients with presumed nosocomial pneumonia probably have infiltrates on the chest radiograph, fever, and leukocytosis resulting from noninfectious causes. Because of the high mortality and morbidity associated with nosocomial pneumonias, however, most clinicians treat such patients with a 2-week empiric trial of antibiotics. Before therapy is initiated, the clinician should rule out other causes of pulmonary infiltrates, fever, and leukocytosis that mimic a nosocomial pneumonia (e.g., pre-existing interstitial lung disease, primary or metastatic lung carcinomas, pulmonary emboli, pulmonary drug reactions, pulmonary hemorrhage, collagen vascular disease affecting the lungs, or congestive heart failure). If these disorders can be eliminated from diagnostic consideration, a 2-week trial of empiric monotherapy is indicated. The clinician should treat cases of presumed nosocomial pneumonia as if P. aeruginosa were the pathogen. Although P. aeruginosa is not the most common cause of nosocomial pneumonia, it is the most virulent pulmonary pathogen associated with nosocomial pneumonia. Coverage directed against P. aeruginosa is effective against all other aerobic gram-negative bacillary pathogens causing hospital-acquired pneumonia. The clinician should select an antibiotic for empiric monotherapy that is highly effective against P. aeruginosa, has a good side-effect profile, has a low resistance potential, and is relatively inexpensive in terms of its cost to the institution. The preferred agents for empiric monotherapy for nosocomial pneumonia are cefepime, meropenem, and piperacillin. Single organisms are responsible for nosocomial pneumonia, not multiple pathogens. S. aureus rarely, if ever, causes nosocomial pneumonia but is mentioned frequently in studies based on cultures of respiratory tract secretions. S. aureus, unless accompanied by a necrotizing pneumonia with rapid cavitation within 72 hours, in the sputum indicates colonization rather than infection and should not be addressed therapeutically. Antibiotics associated with a high resistance potential should not be used as monotherapy or included in combination therapy regimens (i.e., ceftazidime, ciprofloxacin, imipenem, or gentamicin). Combination therapy is more expensive than monotherapy and is indicated only when P. aeruginosa is extremely likely, based on its characteristic clinical presentation, or is proved by tissue biopsy. Therapy should not be based on respiratory secretion cultures regardless of technique. Optimal combination regimens include cefepime or meropenem plus levofloxacin or piperacillin or aztreonam or amikacin. Nosocomial pneumonias usually are treated for 14 days. Lack of radiographic or clinical response to appropriate empiric nosocomial pneumonia monotherapy after 14 days suggests an alternate diagnosis. In these patients, a tissue biopsy specimen should be obtained to determine the cause of the persistence of pulmonary infiltrates unresponsive to appropriate antimicrobial therapy.

Protected specimen brush or bronchoalveolar lavage to diagnose bacterial nosocomial pneumonia in ventilated adults: a meta-analysis

OBJECTIVE

We conducted a meta-analysis by using summary receiver operating characteristic curves to compare the diagnostic value for bacterial nosocomial pneumonia of the following: a) quantitative culture (colony-forming units per milliliter or CFU/mL) of respiratory secretions collected with a bronchoscopic protected specimen brush (PSB); b) quantitative culture of a bronchoscopic bronchoalveolar lavage (BAL); and c) the percentage of infected cells (IC) in BAL.

DATA SOURCES

All studies published in the English or the French language, through January 1, 1995, on the evaluation of PSB or BAL for the diagnosis of pneumonia were considered for analysis. The relevant literature was identified through computer and reference searching and by experts in the field.

STUDY SELECTION

A study was included if at least two of three independent readers regarded its purpose as the evaluation of CFU-PSB, CFU-BAL, or IC-BAL for the diagnosis in human beings of bacterial nosocomial pneumonia in ventilated adults and if the study was prospective and published in a peer-reviewed journal.

DATA EXTRACTION

Three readers reviewed all published articles and decided whether to include each study; consensus was defined as agreement by at least two readers. The authors of each original article included in the meta-analysis were asked to complete a questionnaire in which they were asked to check and to correct the data extracted by one of the independent readers.

DATA SYNTHESIS

Summary receiver operating characteristic curves were used to compare the efficacy of three diagnostic tests. Eighteen studies on CFU-PSB (795 patients) were included, as well as 11 studies on CFU-BAL (435 patients) and 11 on IC-BAL (766 patients). The accuracy of these tests was not different. However, it seems that administration of previous antibiotics markedly decreased accuracy of CFU-PSB (p = .0002) but not the accuracy of CFU-BAL and that of IC-BAL.

CONCLUSION

Both PSB and BAL are reliable to diagnose bacterial nosocomial pneumonia. Because CFU-BAL and IC-BAL seemed more resistant to the effects of antibiotics, we recommend BAL rather than PSB if the patient is already receiving antibiotics.

Evaluation of pneumonia diagnosis in intensive care patients

The aims of this study were to investigate the frequency of bronchopneumonia diagnosed by histological criteria among autopsied intensive care unit (ICU) patients and to compare these with rates of pneumonia diagnosed by conventional clinical methods. The study material comprised 141 autopsied ICU patients from 7 ICUs in university hospitals in Copenhagen from a 1-y period. A total of 20 lung tissue specimens were sampled from each patient and the histopathological diagnoses were classified as no, mild, moderate or severe bronchopneumonia. Inter-observer variation was calculated using kappa statistics. Demographic data and diagnoses of pneumonia were registered from the patient files. Twenty-six percent of the patients had pneumonia diagnosed whilst in the ICU. Histological evidence of pneumonia, found for every second patient, was regarded as the gold standard. Diagnosis of pneumonia in the ICU had a sensitivity of 29% and if diagnoses of pneumonia during the month before ICU-admission were included, a sensitivity of 60% was found. Specificity for pneumonia diagnosed in the ICU was 77%. The percentage of all ICU-patients with pneumonia was calculated to be between 36% and 56%, depending on the extent of excess mortality attributable to pneumonia. Pulmonary segments with histologically diagnosed pneumonic lesions were distributed diffusely, although the upper segments tended to be affected less. Nearly all patients had other histopathological findings than bronchopneumonia. The reliability coefficient among the 6 pathologists was found to be moderately good (kappa = 0.45).

Respiratory infectious complications in the intensive care unit

Ventilator-associated pneumonia is the most common infectious respiratory complication in intensive care unit patients, particularly those needing mechanical ventilation. Ventilator-associated pneumonia represents a challenging problem in terms of diagnosis, treatment, and prevention. Nosocomial sinusitis is another respiratory infection, not uncommon in mechanically ventilated patients. This type of infection has to be suspected in nasally intubated patients and may be a hidden focus of fever and sepsis.

Diagnosis of ventilator-associated pneumonia

The diagnosis of ventilator-associated pneumonia (VAP) is problematic despite numerous attempts at defining acceptable diagnostic criteria and the optimal technique for routine respiratory sampling. Clinical criteria have imperfect diagnostic reliability in ventilated patients, but remain crucial for defining those patients who may require respiratory sampling. Quantitative clinical scoring systems may improve the accuracy of clinical diagnosis in some ventilated patients. Review of published studies suggest that fibreoptic bronchoscopic techniques have greater diagnostic reliability than qualitative endotracheal aspirates, despite inconsistent results when comparing the same techniques in different centres. However, the cost and invasive nature of bronchoscopic methods precludes their use as first-line techniques in VAP. Non-bronchoscopic, non-directed techniques are cheaper, safer and more widely available alternatives to fibreoptic bronchoscopy techniques and have comparable accuracy. Quantitation of respiratory tract cultures is useful in excluding VAP in patients with equivocal signs of pneumonia. The diagnostic threshold of bacterial load that defines the presence of VAP should vary according to the pre-test probability of pneumonia, length of ventilation, antibiotic administration and immunocompetence of the patient.

Histopathology of ventilator-associated pneumonia (VAP) and its clinical implications

Ventilator-associated pneumonia (VAP) is a diffuse polymicrobial and dynamic process, with heterogeneous distribution of lesions, showing different degrees of histological evolution predominating in the dependent lung zones, in which microbiology and histology can be dissociated. This might explain why blind endobronchial techniques to collect respiratory secretions have similar accuracy compared to visually guided samples, explaining the difficulties in validating any methods for its diagnosis. In the clinical setting the association of acute lung injury (ALI) and pneumonia is controversial. However, it is rare to detect diffuse alveolar damage (DAD) in absence of histological signs of pneumonia, probably evidencing that ALI favors the development of pneumonia. Histopathologically, it is difficult to distinguish initial and resolution phases of DAD from pneumonia and vice versa. On the other hand, there is a clear relationship between antimicrobial treatment and the decreased lung bacterial burden which strengthens the importance of distal airway sampling before starting antibiotic therapy.

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.

Ventilator-associated pneumonia

Mechanically ventilated patients are at a substantially higher risk for developing nosocomial pneumonia. Overall, there is a relatively constant 1&!TN!150;3% risk per day of developing pneumonia while receiving mechanical ventilation. The sensitivity and specificity of clinical criteria alone for diagnosis of ventilator-associated pneumonias (VAP) is low. Several techniques have been developed to sample and quantitate the lower respiratory tract to improve the diagnostic yield. Gram-negative bacillary pneumonias account for the majority of the VAP. Strategies for prevention of VAP such as use of sucralfate for stress ulcer prophylaxis and selective decontamination of the digestive tract have been the focus of many clinical studies. Cost-effective preventive measures are needed to combat the increasing antimicrobial resistance, growing population of immunocompromised patients and increasing number of mechanically ventilated patients.

[Diagnostic characteristics of acquired pneumonia in patients under mechanical respiration]

Ventilator-associated pneumonias (VAP) are the most frequent nosocomial lung infections. Histological diagnosis is the standard for reference. A diagnosis of VAP can be considered in presence of fever or hypothermia, hyperleucocytosis or leucopenia, worsening of blood gases, and new radiological infiltrate. Their diagnostical value is dependent on the number of included manifestations. A clinical pulmonary infection score (CPIS) has been produced and compared with histological data. Bacteriological data are essential for an adapted antibiotherapy. The blind non-protected specimen brush is inexpensive and reliable at levels of 10(4) and 10(6) CFU.mL-1, the sensitivity and specificity reach 60%. The double-protected catheter is a sensitive and specific test at the level of 10(3) CFU.mL-1. At present its accuracy has only been compared with bronchial brushing. The culture of a 20 mL mini-broncho-alveolar lavage (same material) is specific (50%) but not sensitive enough (< 70%) at the level of 10(3) CFU.mL-1. The culture of the protected telescopic brush is the most expensive test. It does not carry a risk of contamination, but does not detect a significant amount of VAP even at a level below 10(3) CFU.mL-1. Due to its high specificity it is used as the reference test in numerous studies. The endoscopic broncho-alveolar lavage provides a rapid diagnosis. Although not protected, it carries a low risk of false positives. It also allows the diagnosis of non-bacterial or atypical bacterial lung infections. The diagnosis can also be obtained with lung biopsy which however carries a risk in case of mechanical ventilation, whatever the technique. Except for the protected double catheter, a direct examination has been advocated, for the differentiation between infection and colonization and the improvement of the performances of the simple culture of the broncho-alveolar lavage (search for intra-cellular bacteria).

Low specificity of the bacterial index for the diagnosis of bacterial pneumonia by bronchoalveolar lavage

The bacterial index (BI) as defined by the sum of log10 colony-forming units (cfu) of microorganisms per milliliter of bronchoalveolar lavage (BAL) fluid, i.e., a multiplication of the single cfu/ml, has been used to distinguish between polymicrobial pneumonia (BI> or =5) and colonization (BI<5). Since many false-positive results are to be expected using this parameter, the diagnostic value of the BI was studied prospectively by obtaining bacteriologic cultures of BAL fluid in 165 consecutive unselected patients. In 27 cases the diagnosis of bacterial pneumonia was established on clinical criteria. In 133 patients pneumonia could be excluded, and in five patients the diagnosis remained unclear. Using a cut-off of > or = 10(5) cfu/ml BAL fluid, sensitivity and specificity for the diagnosis of pneumonia were 33% (9/27) and 99% (132/133), respectively. Sensitivity was mainly influenced by prior treatment with antibiotics, being 70% (7/10) in untreated and 12% (2/17) in treated patients. Applying the BI methodology at a cut-off of > or =5, however, resulted in an unacceptably high rate of 16 additional false-positive results, thus lowering the specificity to 87% (116/133; P<0.0001) while increasing the sensitivity to only 41% (11/27; P = 0.77). In conclusion, given the high rate of false-positive results, the methodology of the BI is of doubtful value for the diagnosis of bacterial pneumonia by BAL in an unselected patient group. By applying the absolute number of cfu/ml BAL fluid, however, positive bacteriologic cultures of BAL fluid are highly specific for the diagnosis of pneumonia. Their sensitivity is limited by previous antibiotic therapy.

The role of bronchoalveolar lavage in the diagnosis of bacterial pneumonia

Bronchoalveolar lavage (BAL) has become an invaluable diagnostic tool with important clinical implications in both opportunistic infections and the pulmonary pathology of immunologic disease. Until recently, the use of BAL was limited primarily to two areas: the study of interstitial lung diseases and the diagnosis of lung infections by opportunistic microorganisms in severely immunocompromised patients with lung infiltrates. Over the past decade, the use of BAL has been expanded to include the conventional diagnosis of bacterial pneumonia in non-immunocompromised patients. In the past, different clinical studies proposed using BAL to quantify cultures in the sample obtained as a means of increasing the tool's effectiveness. Recent developments have led to a number of newer applications of BAL, such as bronchoscopic BAL, non-bronchoscopic BAL and protected BAL. The most important use of BAL in the non-immunocompromised patient is the diagnosis of pneumonia in the mechanically ventilated patient.

Elastin fiber analysis in acute diffuse lung injury caused by smoke inhalation

OBJECTIVE

The evaluation of various techniques to diagnose or exclude ventilator-associated bacterial pneumonia has been a focus of much research. One such technique involves elastin fiber detection. It has been inferred from previous work that 40% potassium hydroxide preparations of respiratory secretions that demonstrate elastin fibers have a 100% specificity in diagnosing bacterial pneumonia in intubated, mechanically ventilated patients without acute diffuse lung injury. The purpose of this investigation was to ascertain if elastin fibers might be detected in respiratory secretions in acute, diffuse lung injury in the absence of pneumonia (i.e., assess specificity).

DESIGN

An animal model using a standardized smoke inhalation protocol to cause acute, diffuse lung injury was used.

MATERIALS AND METHODS

Respiratory secretions collected from the endotracheal tubes from eight sheep that underwent the standardized smoke inhalation protocol and were examined with 40% potassium hydroxide. Histologic data were obtained from autopsy to diagnose or exclude lung injury and pneumonia.

MEASUREMENT AND MAIN RESULTS

We found six (false) positive elastin fiber preparations in the absence of histologic pneumonia. Specificity was 0.25.

CONCLUSIONS

We concluded that seeing these results, given a true specificity of 0.99 inferred from previous work, is highly improbable with a probability of 2.74 x 10(-7). Thus, elastin fiber analysis is likely to be highly nonspecific for diagnosing pneumonia in the setting of acute diffuse lung injury.

Comparison of Ballard catheter bronchoalveolar lavage with bronchoscopic bronchoalveolar lavage

BACKGROUND

Bronchoscopic bronchoalveolar lavage (BAL) in mechanically ventilated patients requires a large endotracheal tube, physician expertise, expensive equipment, and support staff.

METHODS

The Ballard BAL catheter is a disposable coude tip 16F device that can be attached to the endotracheal tube and ventilator circuit without loss of positive end-expiratory pressure (PEEP) and also allows supplemental delivery of oxygen between the 12F inner and outer catheters. The catheter is directed into the selected bronchus. The inner catheter with mushroom tip is then advanced until it wedges by feel. Thirteen patients at a tertiary care, university hospital, had BAL performed through both the bronchoscope and Ballard BAL catheter using five aliquots of 20 mL of normal saline solution each. The return was quantified and submitted for blinded, paired laboratory investigations, including Gram stain and quantitative culture, and special stains and cultures as clinically appropriate.

RESULTS

The procedure was well tolerated in all patients with no difference between devices in oxygen saturations; however, air leaks occurred in patients undergoing bronchoscopy and compromised safety in one. Two patients required reintubation to facilitate passage of the bronchoscope. The bronchoscopic BAL return averaged 49 mL (range, 5 to 85 mL) while BAL catheter averaged 37 mL (range, 18 to 70 mL) both being sufficient for all desired investigations except one patient who had undergone bronchoscopy. All were of excellent quality based on microscopy. The BAL results were concordant in nine patients: two Pneumocystis carinii, one Candida, one Streptococcus agalactiae, one Streptococcus pneumoniae, and no infection in four. Diagnoses of tuberculosis and Enterococcus (confirmed by blood culture) were obtained by the Ballard BAL catheter only. Kaposi's sarcoma and metastatic histiosarcoma were visualized by bronchoscope only. Two patients had compassionate plea use of the Ballard BAL catheter because of a small endotracheal tube. Hemorrhage secondary to lupus was documented in one and nosocomial infection was excluded in the other.

CONCLUSIONS

The Ballard BAL catheter allows easy, safe BAL, without loss of diagnostic yield, when visualization is not required in mechanically ventilated patients. The Ballard BAL catheter allows maintenance of PEEP when used with the supplied adapter and can be used with small endotracheal tubes.

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.

Diagnosing ventilator-associated pneumonia: the role of bronchoscopy

OBJECTIVE

To discuss the two diagnostic procedures used most frequently to obtain uncontaminated lower airway secretions during bronchoscopy.

DESIGN

This article reviews the contributing risk factors of ventilator-associated pneumonia (VAP) and the recent studies that have assessed the usefulness of the protected specimen brush (PSB) and bronchoalveolar lavage (BAL) in the nonimmunocompromised host.

RESULTS

A prompt, accurate diagnosis of VAP, including specific identification of the bacterial pathogen, remains a common challenge in the intensive-care unit. Standard clinical criteria are of suboptimal specificity for making decisions, including selecting antibiotic therapy. Bronchoscopic techniques of lung secretion sampling can be used in the intensive-care unit in an effort to overcome the effects of oropharyngeal contamination. The PSB and BAL, used appropriately, can help intensive-care clinicians formulate specific antimicrobial therapy. Evaluation of intracellular bacteria obtained by BAL has been reported to be useful in guiding empiric antibiotic therapy while the final results of cultures obtained with the PSB are pending. Prior antibiotic therapy, however, may confound the interpretation and clinical utility of results.

CONCLUSION

Currently, for a patient taking antibiotic therapy, no reliable technique nor quantitative culture threshold exists to help in diagnosing suspected VAP or in guiding antibiotic therapy. If the clinical situation allows, antibiotic therapy should be discontinued for 48 hours; then, the PSB, BAL, protected BAL, or endobronchial aspiration should be used. These contemporary modalities, however, necessitate further clinical trials before widespread use is warranted.

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.

A simple method of bronchoalveolar lavage

Twenty-eight ventilated paediatric intensive care patients, mean age 4.1 +/- 4 years, who had had a simple method of nonbronchoscopic bronchoalveolar lavage (NB-BAL) performed were reviewed. The NB-BAL technique involved blindly wedging a 5 or 8F infant feeding catheter endobronchially and lavaging one millilitre per kg saline using a syringe. Adequate samples were collected in 87% of the NB-BAL specimens. In two of the four inadequate specimens, Pneumocystis carinii was still able to be identified. Additional information not obtained from the tracheal aspirate culture was seen in 71% of the NB-BAL samples. One-third of the patients also had a bronchoscopic BAL or a lung biopsy performed and the culture results were all identical to those obtained from NB-BAL. No significant complications were seen. Oxygenation and ventilation were not altered by the technique. We conclude that NB-BAL performed using a syringe and infant feeding catheter is a simple and cheap method that produces good alveolar samples in the majority of cases.

[Nosocomial pneumonia in intensive care. Value of different diagnostic tools]

The authors analyzed in published studies providing histologic data the value of diagnostic means of nosocomial bronchopneumonia (NBP) in critically ill patients. At least 10% of patients whose trachea is intubated and the lungs mechanically ventilated suffer an histologically-confirmed NBP. Histology of NBP consists of non systematized foci of infection, localised in 90% of cases in the posterior segments of the lower pulmonary lobes. In fact, small foci are disseminated in both lungs, usually within large areas of non infectious pulmonary lesions and are often multimicrobial. This may explain why the clinical and radiological diagnosis is inaccurate in more than 40% of cases. On chest X-ray, aeric bronchogram and alveolar infiltrates are suggestive but non-specific for NBP, as are also fever, leukocytosis and purulent sputum. Therefore, to confirm the diagnosis of infection and to isolate the microorganisms responsible for NBP, additional investigations are required whose interpretation is uneasy. In a simplified manner, bacteriological inoculum takes a course parallel to the histological bronchopulmonary lesions: no bacteria in the absence of infection, high bacterial inoculum in case of confluent NBP, intermediary in case of bronchitis, however with exceptions when antibiotherapy has recently been modified. In fact, neither bronchial protected brushing nor broncho-alveolar lavage techniques have a perfect sensitivity and specificity. As an example, a diagnostic procedure in assessed in calculating the probability of an accurate diagnosis of NBP. It is concluded that diagnosis of ventilator-associated pneumonia remains still unreliable with the means available today.

Diagnostic efficiency of endotracheal aspirates with quantitative bacterial cultures in intubated patients with suspected pneumonia. Comparison with the protected specimen brush

The objectives of the study were to determine the agreement between the protected specimen brush technique (PSB) with quantitative cultures and endotracheal aspirates (EA) with quantitative cultures when using increasing interpretative cutoff points and to investigate the respective operating characteristics for the diagnosis of pneumonia of PSB and EA when using quantitative cultures. Consecutive sampling of respiratory secretions using these two techniques was conducted in the respiratory intensive care units in 52 mechanically ventilated patients with clinical and radiologic suspicion of pneumonia. Quantitative bacterial cultures of PSB and EA samples were obtained. The 10(6) cfu/ml cutoff point was the most accurate diagnostic threshold for the EA technique. When using this threshold, there was a high level of agreement (84.6%) between PSB and EA results. Among the few discrepancies, the EA result was always indicative of pneumonia, whereas the PSB result was nonindicative, thus permitting us to classify correctly five patients in whom pneumonia would have been erroneously excluded on the basis of the sole result of PSB. Conversely, there was no case where the PSB result was indicative of pneumonia when the EA result (at the 10(6) cfu/ml level) was not. The operating characteristics of the PSB technique for the diagnosis of pneumonia were in accordance with previously published studies. The operating characteristics of the EA technique (when taking the 10(6) cfu/ml of respiratory secretions as the interpretative cutoff point) compared favorably with those of the PSB technique. Diagnostic accuracy rates were similar. The specificity of EA was somewhat lower (83 versus 96%), but the sensitivity was higher (82 versus 64%).(ABSTRACT TRUNCATED AT 250 WORDS)

Diagnosis of nosocomial pneumonia in mechanically ventilated patients by the blind protected telescoping catheter

OBJECTIVES

To demonstrate that blind insertion of the protected telescoping catheter (PTC-NB) through the orotracheal tube can provide reliable pulmonary samples for the diagnosis of nosocomial pneumonia (NP) in ventilated patients.

DESIGN

We performed a random comparison between the protected telescoping catheter introduced through a bronchofiberscope (PTC-B) and the PTC-NB to diagnose NP.

SETTING

A general intensive care unit of a University Hospital.

PATIENTS

40 consecutive patients on mechanical ventilation and with suspicion of NP. The diagnosis of NP was suspected by clinical and chest X-ray findings.

MEASUREMENTS AND RESULTS

NP was confirmed microbiologically in 26 (65%) patients and maintained in 8 patients by clinical and radiological criteria. PTC-NB confirmed the microbiological diagnosis of PN in 21 (80%) patients. The use of antibiotics prior taking respiratory samples reduced the sensitivity of PTC-NB and PTC-B from 100-74% and from 94-70% (p = 0.001). Both techniques agreed in 24 of 33 (73%) patients but such agreement was better when PN was on the right lung. Two patients developed a self-limiting hemoptysis after the PTC-B procedure.

CONCLUSIONS

PTC-NB is as sensitive as specific as PTC-B for diagnosing PN in mechanically ventilated patients, being a much easier technique to use.

Specificity of endotracheal aspiration, protected specimen brush, and bronchoalveolar lavage in mechanically ventilated patients

The specificity of the different techniques used to diagnose ventilator-associated pneumonia is still a matter of controversy. To investigate the specificity of endotracheal aspiration (EA), protected specimen brush (PSB), and bronchoalveolar lavage (BAL) quantitative cultures, we studied 27 consecutive mechanically ventilated (MV) patients (> 72 h) without clinical or radiographic evidence of pulmonary infection. Comparing different thresholds for quantitative cultures (from 10(3) through 10(6) CFU/ml), the lowest rate of false positive results was obtained using 10(6) for EA, 10(5) for PSB, and 10(6) for BAL. Using 10(6) CFU/ml for EA, 10(4) CFU/ml for PSB, and 10(5) CFU/ml for BAL as cutoff points, we obtained the following specificities: 85, 85, and 78% for the three techniques, respectively. A bacterial index of 8 was the best threshold to get a low percentage of false positive results for all techniques except for EA (0% for PSB and 12% for BAL). There were reasonable qualitative agreements (PSB versus EA = 58%; BAL versus EA = 69%; and PSB versus BAL = 62%) and poor quantitative correlations between concomitantly isolated microorganisms from the three types of samples. Quantitative cultures of EA, PSB, and BAL may show a considerable percentage of false positive results at the respective cutoff points usually accepted. Increasing the thresholds for quantitative cultures, albeit loosing sensitivity, may rule out better the absence of pulmonary infection in MV patients.