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* From Istituto di Anestesiologia e Rianimazione (Drs. Antonelli, Conti, Arcangeli, Cavaliere, and Proietti), Università Cattolica del Sacro Cuore, Rome, Italy; Università La Sapienza (Dr. Rocco), Rome, Italy; and the Department of Medicine (Dr. Meduri), Pulmonary and Critical Care Division, University of Tennessee, Memphis, TN.
Correspondence to: Massimo Antonelli, MD, Istituto di Anestesiologia e Rianimazione, Università Cattolica del Sacro Cuore, Policlinico A. Gemelli, Largo A. Gemelli 8, 00168 Rome, Italy; e-mail: max.antonelli{at}flashnet.it or m.antonelli{at}rm.unicatt.it
| Abstract |
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100) who are undergoing diagnostic fiberoptic bronchoscopy (FOB). The efficacy of this intervention in patients with less severe forms of hypoxemia (ie, PaO2/FIO2 ratio, < 200) is unknown.
Patients and methods: Twenty-six patients with PaO2/FIO2 ratios
200 who required bronchoscopic BAL for suspected nosocomial pneumonia were entered into the study. Thirteen patients were randomized during FOB to receive NPPV, and 13 patients were randomized to receive conventional oxygen supplementation by Venturi mask. The primary end points were changes in the PaO2/FIO2 ratio during FOB and within 60 min of terminating the procedure.
Results and outcome: At study entry, the two groups were similar in terms of age, simplified acute physiologic score II values, and cardiorespiratory parameters. During FOB, the mean (± SD) PaO2/FIO2 ratio increased by 82% in the NPPV group (261 ± 100 vs 139 ± 38; p < 0.001) and decreased by 10% in the conventional oxygen supplementation group (155 ± 24 to 139 ± 38; p = 0.23). Sixty minutes after undergoing FOB, the NPPV group had a higher mean PaO2/FIO2 ratio (176 ± 62 vs 140 ± 38; p = 0.09), a lower mean heart rate (91 ± 18 vs 108 ± 15 beats/min; p = 0.02), and no reduction in mean arterial pressure in comparison to a 15% decrease from the baseline in the control group. One patient in the NPPV group and two patients in the control group required nonemergent intubation. Major bacterial isolates included Staphylococcus aureus (7 of 30 isolates; 23%) and Pseudomonas aeruginosa (12 of 30 isolates; 40%).
Conclusion: In patients with severe hypoxemia, NPPV is superior to conventional oxygen supplementation in preventing gas-exchange deterioration during FOB with better hemodynamic tolerance.
Key Words: acute respiratory failure bronchoscopy hypoxemia noninvasive positive pressure ventilation pneumonia
Early and accurate diagnosis of nosocomial pneumonia simplifies the selection of appropriate antibiotic therapy and may improve outcome.1 2 3 4 Fiberoptic bronchoscopy (FOB) with BAL is an important tool for determining the etiologic diagnosis of pneumonia. Because arterial oxygen tension routinely decreases by 10 to 20 mm Hg in patients after they undergo uncomplicated FOB, hypoxemic patients are at high risk for developing respiratory failure or serious cardiac arrhythmias.5 6 In nonintubated patients, severe hypoxemia (defined as requiring continuous positive airway pressure [CPAP] or an inspired oxygen concentration of > 50% to maintain arterial oxygen tension of at least 75 mm Hg) is an accepted contraindication to bronchoscopy.5 In these high-risk patients, the options are to intubate and to apply mechanical ventilation (MV) to ensure adequate gas exchange during FOB or to avoid FOB and to institute empirical treatment.
Noninvasive positive-pressure ventilation (NPPV) refers to the delivery of assisted MV without the need for an invasive artificial airway.7 In cases of acute respiratory failure when NPPV is effective in avoiding endotracheal intubation, the morbidity and mortality associated with MV are reduced.8 9 10 Three randomized studies8 9 10 have provided supporting evidence for the selected application of NPPV in patients experiencing hypoxemic respiratory failure of varied etiologies, including patients with pneumonia. We originally reported on the use of NPPV to assist spontaneous breathing through a facial mask during FOB with BAL in severely hypoxemic, nonintubated patients.11 The study included eight consecutive immunosuppressed patients with suspected pneumonia and a PaO2/fraction of inspired oxygen (FIO2) ratio of < 100. We found that NPPV during FOB was well-tolerated, significantly improved the PaO2/FIO2 ratio, and successfully avoided the need for endotracheal intubation. The testing of BAL specimens identified a causative agent of pneumonia in all studied patients.
Whether NPPV-assisted bronchoscopy may benefit immunocompetent patients with less severe hypoxemia (ie, PaO2/FIO2 ratio, < 200) is not known. For this reason, patients who required bronchoscopic BAL for the confirmation of suspected nosocomial pneumonia and had a PaO2/FIO2 ratio of
200 were compared in a randomized study by comparing NPPV vs conventional oxygen supplementation during FOB. The primary end points were changes in the PaO2/FIO2 ratio during FOB and within 60 min of terminating the procedure.
| Materials and Methods |
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Before undergoing bronchoscopy, all patients were placed on a Venturi mask with adjustable FIO2 (Baxter; Mirandola, Italy) starting with an FIO2
0.5 and adjusted to achieve a level of arterial oxygen saturation by pulse oximetry (SpO2) of > 92%.
Patients then were randomly assigned to receive standard oxygen supplementation or NPPV through a face mask during bronchoscopy. During the procedure, patients had continuous ECG, arterial BP, and SpO2 monitoring (Biox 3700; Ohmeda; Boulder, CO).
Standard Treatment Group
Patients assigned to the standard treatment received oxygen supplementation via a Venturi mask, and the FIO2 was kept at 0.9 for all the bronchoscopic procedures. In order to obtain a stable and reliable value for the FIO2 in this group, we used a modified high-flow Venturi mask that was equipped with two unidirectional valves and a seal port for the introduction of the bronchoscope (Fig 1
). The FIO2 was confirmed by a portable O2 analyzer (miniOX; Mine Safety Appliances Co; Pittsburgh, PA).
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Bronchoscopic BAL Technique
Topical anesthesia of the nose and pharynx was obtained by spraying a 10% lidocaine solution. Topical anesthesia of the larynx and vocal cords was performed (2% lidocaine hydrochloride, not exceeding 200 mg) before advancing the bronchoscope into the tracheobronchial tree. The tip of the FOB then was wedged into the orifice of the bronchial subsegment that showed increased densities on the chest radiograph. BAL was performed by sequential instillation of five aliquots 25 mL nonbacteriostatic saline solution at room temperature. The retrieved effluent was sent immediately to the microbiology laboratory for microscopic analysis and culturing. The methods and laboratory procedures followed consensus guidelines.14
Bacterial pneumonia was diagnosed when at least 100,000 cfu/mL of bacteria were measured in the BAL fluid.
During the procedure, the FIO2 was kept at 0.9, and serial arterial blood gas values were obtained every 10 min. After the bronchoscopy procedure, the FIO2 was decreased to 0.7, and serial arterial blood gas values were obtained every 20 to 30 min. After 60 min, the applied FIO2 was reduced to the prebronchoscopy requirements if the patient was able to maintain SpO2 at > 92%. The NPPV group had ventilation continued for at least 30 min after termination of bronchoscopy, after which NPPV was discontinued if SpO2 was > 92% and the patient was not experiencing respiratory difficulties.
End Points
The end points were changes occurring in the PaO2/FIO2 ratio during FOB and within 60 min of terminating the procedure, the maintenance of hemodynamic stability, and the avoidance of endotracheal intubation within 24 h of study entry.
Criteria for Endotracheal Intubation
The predetermined criteria for endotracheal intubation included failure to maintain a PaO2 of > 65 mm Hg with an FIO2 that was
0.6, the development of conditions necessitating endotracheal intubation to protect the airways (eg, coma or seizure disorders) or to manage copious tracheal secretions, hemodynamic or ECG instability, the inability to correct dyspnea, or difficulty in tolerating the face mask by those randomized to noninvasive ventilation.
Statistical Analysis
Results are reported as the mean ± SD. Demographic and physiologic characteristics for the two groups were compared using the t test for continuous data (separate estimates of variance were used when variance differed significantly) and with the Mantel-Haenszel extended
2 test for categoric data. Fishers Exact Test (two-tailed) was used when the expected number of cases per cell was below five. A software package (SPSS; SPSS, Inc; Chicago, IL) was used for all analyses.15
| Results |
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During bronchoscopy, the PaO2/FIO2 ratio increased by 82% in the NPPV group (from 143 ± 32 to 261 ± 100; p = 0.002) and decreased by 10% in the conventional oxygen supplementation group (from 155 ± 24 to 139 ± 38; p = 0.23). The PaO2/FIO2 ratio recorded during bronchoscopy was significantly higher in the NPPV group than in the conventional oxygen supplementation group (p < 0.001) [Table 2 ]. One hour following the termination of bronchoscopy, the PaO2/FIO2 ratio was 176 ± 62 in the NPPV group (33% increase from baseline) and 140 ± 38 in the conventional oxygen supplementation group (10% reduction from baseline; p = 0.09). The PaCO2 response was similar for both groups (Table 2) .
During and after bronchoscopy, heart rate varied little from baseline in both groups (Table 2) . During and after bronchoscopy, the mean arterial pressure (MAP) did not change in the NPPV group, and there was a 16% reduction from baseline values in the conventional oxygen supplementation group (81 ± 13 vs 96 ± 13, respectively; p = 0.013). After bronchoscopy, the NPPV group had no reduction in MAP and the conventional oxygen supplementation group had a 15% decrease from baseline (from 96 ± 13 to 78 ± 18, respectively; p = 0.02) In the conventional oxygen supplementation group, the reduction in MAP following bronchoscopy was more pronounced among the five patients with a baseline PaO2/FIO2 ratios of < 160 (baseline, 87 ± 10; during FOB, 75 ± 10; after FOB, 64 ± 9). One patient with cystic fibrosis who was randomized to NPPV had a baseline PaCO2 of 103 mm Hg without alteration in mental status. The combination of noninvasive ventilation and bronchoscopic suctioning of secretions after BAL reduced the PaCO2 to 80 mm Hg. After the patient underwent bronchoscopy, NPPV was applied intermittently as a bridge to successful lung transplantation. The patient was discharged from the hospital 55 days after admission to the study (47 days after transplantation).
A definitive etiologic diagnosis of pneumonia was established in 20 patients. Eighteen patients had significant growth of a pathogen found in BAL fluid, and 2 patients (1 in each group) had bacteremia, with a pathogen recovered in the BAL fluid at a concentration below the diagnostic threshold of 105 cfu/mL. In nine patients (four in the NPPV group and five in the conventional oxygen supplementation group), the testing of BAL fluid showed the presence of more than one microorganism that was growing at a concentration
105 cfu/mL. The microbiological etiology of pneumonia is shown in Table 3
. The most frequently isolated microorganisms were Pseudomonas aeruginosa (40%) and Staphylococcus aureus (23%). Four patients in the NPPV group and seven patients in the conventional oxygen supplementation group died from complications of their underlying disease 5 to 7 days after study entry.
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| Discussion |
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The potential advantages of NPPV during FOB in hypoxemic patients are several. Bronchoscopy is associated with an alteration of the respiratory mechanics and gas exchange causing transient hypoxemia and hypercapnia.16
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In nonintubated patients, the bronchoscope occupies about 10% of the total cross-sectional area of the trachea, thereby decreasing tidal volume and increasing the work of breathing.15
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When suction is applied during FOB, end-expiratory volume and positive end-expiratory pressure are reduced, facilitating alveolar closure and venous admixture,15
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These changes slowly subside following FOB, however, the time to normalization may take several hours in patients with severe parenchymal diseases.18
In one uncontrolled study19
on the cardiopulmonary risk of FOB in 107 patients who were receiving MV, significant hypoxemia (ie, PaO2
60 mm Hg on FIO2 of 0.8) was seen in 13% of patients and was linked to the severity of pulmonary dysfunction and to decreased alveolar ventilation. The mean drop in PaO2 was 26%, which persisted for as long as 2 h. In 1990, the American Thoracic Society guidelines recommended avoiding BAL in spontaneously breathing patients with hypercapnia and/or hypoxemia and in patients whose PaO2 levels cannot be corrected to at least 75 mm Hg or to an SpO2 level of > 90% with supplemental oxygen.6
This randomized study expands on prior reports of applying NPPV11 20 or mask CPAP21 during bronchoscopy in patients either with hypoxemia11 21 or hypercapnia.20 Our group originally described the application of NPPV during bronchoscopy in eight immunocompromised hypoxemic (ie, PaO2/FIO2 ratio, < 100) patients with suspected pneumonia.11 In that study, NPPV was administered in a fashion similar to the one described in this report and was associated with a significant improvement in PaO2/FIO2 ratio during bronchoscopy. The successful application of NPPV during FOB also was reported in patients with COPD. Da Conceicao et al20 investigated 10 consecutive COPD patients with pneumonia who were admitted to the ICU with hypercapnia (ie, PaCO2, 67 ± 11 mm Hg) and hypoxemia (ie, PaO2, 53 ± 13 mm Hg). During FOB with NPPV, the SpO2 increased from 91 ± 4.7% at baseline to 97 ± 1.7%. In both studies, FOB with NPPV was well-tolerated by patients, no complications related to the procedure were observed, and none of the patients required intubation in the postbronchoscopy period.
In the present study, we used pressure support during bronchoscopy. Maitre et al21 recently reported the results of a randomized double-blind study evaluating the application of a new CPAP device during FOB in 30 patients with a mean PaO2/FIO2 ratio of < 300. The open system was based on generating positive airway pressure by four funnel-shaped microchannels that generate microjets, and thus positive pressure, for use with a face mask. The use of CPAP allowed minimal alterations in gas exchange and prevented subsequent respiratory failure. During FOB and 30 min thereafter, SpO2 was significantly higher in the CPAP group. Arterial blood gas measurements 15 min after termination of FOB showed that the PaO2 had increased by 10.5 ± 16.9% in the CPAP group and decreased by 15 ± 16.6% in the oxygen group (p = 0.01).21 Five patients in the oxygen group, but none in the CPAP group, developed respiratory failure and required intubation in the 6 h following the FOB procedure. No study compared CPAP with NPPV support ventilation.
In conclusion, we found that the application of NPPV was superior to oxygen supplementation alone in improving gas exchange during and after diagnostic bronchoscopy, with better hemodynamic tolerance. The findings of this randomized study agree with those of prior uncontrolled studies and provide support for the use of NPPV during bronchoscopy in patients with severe and moderate hypoxemia (ie, PaO2/FIO2 ratio, < 200).
| Acknowledgements |
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| Footnotes |
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Received for publication May 8, 2001. Accepted for publication October 19, 2001.
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