Pneumonia is an important cause of respiratory failure in immune-competent and immune-compromised patients.

Pneumonia is an important cause of respiratory failure in immune-competent and immune-compromised patients. In addition, nosocomial pneumonia is commonly observ in patients undergoing mechanical ventilation for noninfectious respiratory failure. Accurate diagnosis and treatment of lower respiratory tract pathogens is crucial to a favorable issue In recent years, transbronchoscopically obtained specimens, including bronchoalveolar lavage (BAL) and protected-specimen-brush samples with routine or quantitative refinements have been found useful in making a specific diagnosis in similar cases.[1-3] Performing these procedures may cause deterioration in gas exchange owed to ventilation-perfusion mismatch caused on introduction of the bronchoscope, as well as to the creation of additional intrapulmonary shunting after BAL. Because increasing numbers of patients are undergoing these invasive conducts it is important to establish the incidence and clinical importance of their complications.

In this issue of Chest, Papazian et al (see page 1548) describe the hemodynamic and gas exchange drifts of obtaining consecutive protected-specimen-brush and BAL samples in 12 patients with respiratory failure. There were minimal imports on hemodynamic measurements, and becoming decreases in oxygenation were observ Previous studies involving larger numbers of critically ill intubated patients undergoing bronchoscopy with or without BAL also indicate that in greatest in number patients oxygenation was adversely affected to a unassuming degree; however, more pronounced reductions in oxygenation occurr in one patients.[4-6] In our series of 99 consecutive BAL transactions for example, widening of the alveolar to arterial oxygen gradient by means of more than 100 mm Hg lasting up to 4 h after the standard was observed in 13 patients. Our data did not allow us to conclusively determine whether these decreases were directly related to the meanings of BAL or were instead to be ascribed to progression of the underlying disease process

Careful prebronchoscopy screening must be performed to not include patients judged to be at high risk for deleterious issues on gas exchange and hemodynamics.[4-6] These include patients with hemodynamic instability despite large doses of inotropic-support agents, patients whose [POsub2] cannot be elevated above 60 to 70 mm Hg at an [FIO.sub.2], of 10 and those with active bronchospasm. In addition to careful patient selection, the systems used to perform bronchoscopy are important to minimize risk. Bronchoscopy and related processs should be completed in les than 5 to 7 min. Patients should be heavily sedated and, when necessary, paralyzed with neuromuscular blocking agents to eliminate agitation and cough during the management Finally, the bronchoscope should be introduced via an airtight connector to sustain positive end-expiratory pressure and minimize leakage of inspired air.

It is important to recognize that despite all precautions a relatively small proportion of critically ill patients undergoing bronchoscopy will experience a lengthened and/or clinically significant reduction in oxygenation. At this point it is not clear whether this is directly suitable to shunting in the area of lavage, to more far off effects of BAL on global lung function owed to release of cytokines and other mediators, or to progression of the underlying pulmonary condition independent of the manner of proceeding Regardless, after bronchoscopy in critically ill mechanically ventilated patients, the [FIO.sub.2] should be decreased slowly while monitoring oxygen saturation to make secure adequate oxygenation.

References

[1] Fagon JY Chastre J Hance AJ, Guiguet M Trouillet JL Domart Y et al. Detection of nosocomial lung infection in ventilated patients: use of a defend ed specimen brush and quantitative improvement techniques in 147 patients. Am Rev Respir Dis 1988; 138:110-16 [2] Guerra LR Baughman RP Use of bronchoalveolar lavage to diagnose bacterial pneumonia in mechanically ventilated patients. Crit Care M 1990; 18:169 [3] Meduri GU Johanson WG ed International consensus conference: clinical investigation of ventilator-associated pneumonia. Chest 1992; 102(5[suppl 1]):551S-88 [4] Hertz MI, Woodward ME Gros CR Swart M Marcy TW Bitterman PB Safety of bronchoalveolar lavage in the critically ill, mechanically ventilated patient. Crit Care M 1991; 19:1526-32 [5] Trouillet JL Guiguet M Gibert C Fagon JY Dreyfuss D Blanchet F et al. Fiberoptic bronchoscopy in ventilated patients: evaluation of cardiopulmonary risk subject to midazolam sedation. Chest 1990; 97:927-33 [6] Meduri GU Chastre J The standardization of bronchoscopic techniques for ventilator-associated pneumonia. Chest 1992; 102(5[suppl 1]):557S-64S

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