The development of bronchoscopy and bronchoalveolar lavage (BAL) has led to an increase in their use in intensive care units (ICUs), where their applications for differential diagnosis of pulmonary diseases make them indispensable instruments for intensivists [1]. Despite their common use, a few studies have raised concerns about potential impacts on bronchoalveolar lavage fluid (BALF) dilution, which affects mainly the quantitative detection of soluble substances. Urea is a diffusible substance that can easily be detected in capillaries and alveolar spaces. The urea concentration in plasma and that in BALF are approximately equal and their ratio (urea plasma/urea BALF) has previously been applied as an index of BALF dilution. Furthermore, it has been shown that the ratio of high-quality lavage is low in clinical settings [2, 3].
We reviewed all ICU-admitted patients who received BAL from January 2016 to September 2018 in Ren Ji Hospital and analyzed their urea plasma/urea BALF values. Guidelines of the American Thoracic Society were followed during the BAL procedure [3]. (The procedure is described in Additional file 1.) Among 223 patients included, the median level of urea plasma/urea BALF was 4.2 (interquartile range of 3.2–8.6). The patients were categorized into groups A (urea plasma/urea BALF <4.2) and B (urea plasma/urea BALF ≥4.2). The patients in group A were more likely to receive bronchodilators (35.6% versus 15.9%, P <0.001) and a recruitment maneuver (15.5% versus 5.3%, P = 0.013) than those in group B. More invasive pulmonary aspergillosis (IPA) patients with BALF galactomannan of more than 0.5 could be detected in group A than in group B (84.6% versus 33.3%, respectively; P = 0.019) as well as more bacterial pneumonia patients with the quantitative cultures of BALF of more than 104 CFU/mL (90.6% versus 52.7%, respectively; P <0.001). Primary care physicians performed more BAL than residents did (58.3% versus 31.8%, respectively), especially in group A (Table 1).
Pulmonary function was associated with the urea plasma/urea BALF ratio. It was found that there was a correlation between urea plasma/urea BALF and partial pressure of arterial oxygen/fractional concentration of inspired oxygen (PaO2/FiO2) (R2 = 0.196, P <0.001). The less oxygen-deficient the patient was, the lower the urea plasma/urea BALF level was (Fig. 1a,b). Sixty-eight patients with chronic obstructive pulmonary disease (COPD) were enrolled in our study. The forced expiratory volume in the first second (FEV1) was suggested as a measure of bronchial obstruction. FEV1 of less than 50% of the predicted normal value indicated the presence of severe ventilatory impairment, which led to a lower volume of instilled saline flow into the alveoli. In our study, a correlation was also found between FEV1 and urea plasma/urea BALF (R2 = 0.299, P <0.001). A lower value of urea plasma/urea BALF was obtained in a group with FEV1 of at least 50% of the predicted value than in that with FEV1 of less than 50% of the predicted value (P <0.05, Fig. 1c, d).
Providing appropriate training in BAL skills to intensivists while ensuring patient safety is challenging [4]. Inter-operator variability in the recovery of lavage fluid during a BAL procedure may affect the concentration of soluble substances such as galactomannan and the results of quantitative cultures [5]. More attention should be paid to patients with hypoxia and impaired pulmonary function. Bronchodilators and a recruitment maneuver may improve BALF dilution during the procedure, and residents in ICUs need more practice.
Abbreviations
- BAL:
-
Bronchoalveolar lavage
- BALF:
-
Bronchoalveolar lavage fluid
- FEV1 :
-
Forced expiratory volume in the first second
- ICU:
-
Intensive care unit
References
Ergan B, Nava S. The use of bronchoscopy in critically ill patients: considerations and complications. Expert Rev Respir Med. 2018;12:651–63.
Baughman RP. The uncertainties of bronchoalveolar lavage. Eur Respir J. 1997;10:1940–2.
Meyer KC, Raghu G, Baughman RP, Brown KK, Costabel U, du Bois RM, et al. An official American Thoracic Society clinical practice guideline: the clinical utility of bronchoalveolar lavage cellular analysis in interstitial lung disease. Am J Respir Crit Care Med. 2012;185:1004–14.
Roux D, Reignier J, Thiery G, Boyer A, Hayon J, Souweine B, et al. Acquiring procedural skills in ICUs: a prospective multicenter study. Crit Care Med. 2014;42:886–95.
Yu Y, Zhu C, Gao Y. Bronchoalveolar lavage fluid galactomannan as a diagnostic biomarker for IPA: still a long way to go. Crit Care. 2016;20:280.
Acknowledgments
None.
Funding
This work was supported by the National Key Research and Development Program of China (2017YFC0909002) and the Scientific Research Project of Shanghai Municipal Health Bureau (201840006).
Availability of data and materials
Not applicable.
Author information
Authors and Affiliations
Contributions
YY and CL both conceived and designed the experiments. YY, CL, and YL performed the experiments. HS and ZZ analyzed the data. YY and YL contributed reagents, materials, and analysis tools. YY, LL, and YG helped to draft and edit the article. All authors approved the final manuscript.
Corresponding authors
Ethics declarations
Ethics approval and consent to participate
This study was approved by the ethics committee of Shanghai Jiao Tong University (2016-Clinical-Res-083), and written informed consent was obtained from either the patients or the next of kin.
Consent for publication
Not applicable.
Competing interests
The authors declare that they have no competing interests.
Publisher’s Note
Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
Additional file
Additional file 1:
Guidelines of the American Thoracic Society were followed during the bronchoalveolar lavage (BAL) procedure. Selection of the segment for BAL was guided by chest x-ray changes. The right middle lobe or lingual lobe was selected when diffuse infiltrates were present. Five 20-mL aliquots of sterile saline were instilled and aspirated gently in each patient. The total volume of the retrieved liquid should be greater than or equal to 30% of the total volume of the instilled saline. (ZIP 492 kb)
Rights and permissions
Open Access This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated.
About this article
Cite this article
Yu, Y., Liu, C., Zhang, Z. et al. Bronchoalveolar lavage fluid dilution in ICU patients: what we should know and what we should do. Crit Care 23, 23 (2019). https://doi.org/10.1186/s13054-018-2300-x
Received:
Accepted:
Published:
DOI: https://doi.org/10.1186/s13054-018-2300-x