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Critical Care

, 23:23 | Cite as

Bronchoalveolar lavage fluid dilution in ICU patients: what we should know and what we should do

  • Yuetian Yu
  • Chunyan Liu
  • Zhongheng Zhang
  • Hui Shen
  • Yujie Li
  • Liangjing LuEmail author
  • Yuan GaoEmail author
Open Access
Letter

Abbreviations

BAL

Bronchoalveolar lavage

BALF

Bronchoalveolar lavage fluid

FEV1

Forced expiratory volume in the first second

ICU

Intensive care unit

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).
Table 1

Demographics and clinical characteristics of the patients

Characteristics

All patients

Group A

(urea plasma/urea BALF <4.2)

Group B

(urea plasma/urea BALF ≥4.2)

P value

n = 223

n = 110

n = 113

Age, years

54 (43–67)

51 (43–66)

56 (43–67)

0.945

Gender, male

103 (46.2)

53 (48.2)

50 (44.2)

0.556

BMI, kg/m2

21.9 (18.5–23.4)

22.1 (18.4–23.4)

21.8 (18.5–23.4)

0.515

PaO2/FiO2

210.4 (120.4–271.5)

250.9 (206.7–320.5)

137.4 (88.6–210.4)

<0.001

Pulmonary disease

 AECOPD

68 (30.5)

33 (30.0)

35 (30.9)

0.875

 CAP

61 (27.4)

28 (25.5)

35 (30.9)

0.36

 HAP

33 (14.8)

17 (15.5)

14 (12.4)

0.508

 VAP

16 (7.2)

7 (6.4)

9 (7.9)

0.643

 IPA

28 (12.6)

13 (11.8)

15 (13.3)

0.743

 Others

17 (7.5)

12 (9.0)

5 (4.6)

0.068

APACHE II score

17 (13–23)

16 (14–22)

17 (13–23)

0.799

Intubation and mechanical ventilation

47 (21.1)

21 (19.1)

26 (23.0)

0.473

Lesion location

 Upper lobe

56 (25.1)

26 (23.6)

30 (26.5)

0.616

 Middle and lower lobe

93 (41.7)

51 (46.4)

42 (37.2)

0.164

 Diffusive lesions

74 (33.2)

33 (30.3)

41 (36.3)

0.319

Sedative and narcotic drugs

 Midazolam and fentanyl

96 (43.0)

51 (46.4)

45 (39.8)

0.324

 Propofol and fentanyl

89 (39.9)

42 (38.2)

47 (41.6)

0.603

 Dexmedetomidine

38 (17.1)

17 (15.4)

21 (18.6)

0.534

Bronchodilators was given before BAL

57 (25.6)

39 (35.6)

18 (15.9)

<0.001

RM before BAL

23 (10.3)

17 (15.5)

6 (5.3)

0.013

Operator

 Resident

71 (31.8)

5 (4.5)

66 (58.4)

<0.001

 Primary care physician

130 (58.3)

93 (84.5)

37 (32.7)

<0.001

 Others

22 (9.9)

12 (11.0)

10 (8.9)

0.616

Diagnosed with bacterial pneumonia

178 (79.8)

85 (77.3)

93 (82.3)

0.348

BALF GM >0.5 in IPA patients

16 (57.1)

11 (84.6)

5 (33.3)

0.019

Quantitative cultures of BALF >104 CFU/mL in bacterial pneumonia patients

126 (70.8)

77 (90.6)

49 (52.7)

<0.001

Data are expressed as median (Q1–Q3) or number (percentage). P values for comparison between urea plasma/urea BALF ≥4.2 and <4.2 groups.

Abbreviations: AECOPD acute exacerbation of chronic obstructive pulmonary disease, APACHE II Acute Physiology and Chronic Health Evaluation II, BAL bronchoalveolar lavage, BALF bronchoalveolar lavage fluid, BMI body mass index, CAP community-acquired pneumonia, CFU colony-forming units, FiO2 fractional concentration of inspired oxygen, GM galactomannan, HAP hospital acquired pneumonia, IPA invasive pulmonary aspergillosis, PaO2 partial pressure of arterial oxygen, RM recruitment maneuver, VAP ventilator-associated pneumonia.

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).
Fig. 1

a Correlation between PaO2/FiO2 and urea plasma/urea BALF. b Comparison of urea plasma/urea BALF in different PaO2/FiO2 groups. c Correlation between FEV1/FEV1 predicted and urea plasma/urea BALF in patients with COPD. d Comparison of urea plasma/urea BALF in different FEV1/FEV1 predicted groups in patients with COPD. *P <0.05 in each group. Abbreviations: BALF bronchoalveolar lavage fluid, COPD chronic obstructive pulmonary disease, FEV1 forced expiratory volume in the first second, FiO2 fractional concentration of inspired oxygen, PaO2 partial pressure of arterial oxygen.

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.

Notes

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.

Authors’ 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.

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.

Supplementary material

13054_2018_2300_MOESM1_ESM.zip (492 kb)
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)

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Copyright information

© The Author(s). 2019

Open AccessThis 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.

Authors and Affiliations

  1. 1.Department of Critical Care Medicine, Ren Ji Hospital, School of MedicineShanghai Jiao Tong UniversityShanghaiChina
  2. 2.Department of EmergencyMinhang District Central HospitalShanghaiChina
  3. 3.Department of Emergency Medicine, Sir Run Run Shaw HospitalZhejiang University School of MedicineHangzhouChina
  4. 4.Department of Laboratory Medicine, Shanghai East HospitalTongji University School of MedicineShanghaiChina
  5. 5.Department of Rheumatology, Ren Ji Hospital, School of MedicineShanghai Jiao Tong UniversityShanghaiChina

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