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 Table of Contents  
ORIGINAL ARTICLE
Year : 2019  |  Volume : 7  |  Issue : 1  |  Page : 18-22

Intraobserver Variability and Reliability of Diaphragm Thickness Measurement on Ultrasonography by Critical Care Physician Among Patients with Sepsis


1 Department of Pulmonary Medicine and Sleep Disorder, All India Institute of Medical Sciences, New Delhi, India
2 Department of Biostatistics, All India Institute of Medical Sciences, New Delhi, India

Date of Web Publication18-Jan-2019

Correspondence Address:
Vijay Hadda
Department of Pulmonary Medicine and Sleep Disorders, All India Institute of Medical Sciences, New Delhi
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/jacp.jacp_9_18

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  Abstract 

Background: Diaphragm thickness measurement by ultrasonography (USG) has been shown to be a good surrogate of diaphragmatic functions. However, data regarding reliability of diaphragm thickness measurement by critical care physicians among patients with sepsis is limited. Aims and Objective: This study was designed to assess the variability and reliability of diaphragm thickness measurement on USG by critical care physician in patients with sepsis. Materials and Methods: Study included patients with sepsis who were admitted between March 2015 and December 2016 in a tertiary care center. Three readings of diaphragm thickness were recorded separately during inspiration and expiration using B-mode of USG. Mean [standard deviation (SD)] of variation and intraclass correlation coefficient (ICC) in the measurement were calculated for assessment of variability and reliability, respectively. Results: Four hundred twenty measurements on 70 patients were included in the study. Mean (SD) variation for 1st, 2nd, and 3rd measurement during expiration were 0.233 (0.027) mm, 0.231 (0.029) mm, and 0.233 (0.029) mm, respectively. During inspiration mean (SD) variation for 1st, 2nd, and 3rd measurement were 0.285 (0.033) mm, 0.283 (0.031) mm, and 0.283 (0.033) mm, respectively. The ICC [95% confidence interval (CI)] among 1 vs. 2, 1 vs. 3, and 2 vs. 3 readings taken during expiration were 0.930 (0.889–0.956), 0.919 (0.873–0.949), and 0.940 (0.905–0.963), respectively. During inspiration, ICC (95% CI) among 1 vs. 2, 1 vs. 3, and 2 vs. 3 readings were 0.949 (0.919–0.968), 0.940 (0.905–0.962), and 0.945 (0.914–0.966), respectively. Overall ICC for three readings of diaphragmatic thickness during expiration and inspiration were 0.930 (0.898–0.954); P < 0.001 and 0.945 (0.919–0.963); P < 0.001, respectively. Conclusion: The measurement of diaphragm thickness using USG by critical care physicians among patients with sepsis is reliable with minimal variability.

Keywords: Critical care physicians, diaphragm thickness, reliability, sepsis, ultrasonography, variability


How to cite this article:
Hadda V, Kumar R, Madan K, Khan MA, Mohan A, Khilnani GC, Guleria R. Intraobserver Variability and Reliability of Diaphragm Thickness Measurement on Ultrasonography by Critical Care Physician Among Patients with Sepsis. J Assoc Chest Physicians 2019;7:18-22

How to cite this URL:
Hadda V, Kumar R, Madan K, Khan MA, Mohan A, Khilnani GC, Guleria R. Intraobserver Variability and Reliability of Diaphragm Thickness Measurement on Ultrasonography by Critical Care Physician Among Patients with Sepsis. J Assoc Chest Physicians [serial online] 2019 [cited 2019 Apr 20];7:18-22. Available from: http://www.jacpjournal.org/text.asp?2019/7/1/18/250474


  Introduction Top


Diaphragm dysfunction is common occurrence among critically ill patients admitted to intensive care unit (ICU) and has been associated with difficult extubation and prolonged mechanical ventilation.[1],[2] Both these complications may lead to adverse outcome such as occurrence of ventilator associated pneumonia, prolonged hospital and ICU stay, increased cost of care, and mortality.[1],[2],[3] It has also been reported that sepsis is a risk factor for diaphragmatic dysfunction.[4] Accurate and objective assessment of diaphragmatic function is essential for any preventive and therapeutic intervention among patients with sepsis. Assessment of diaphragmatic function among critically ill patients admitted in ICU remains a challenge. The tools available for assessment of diaphragmatic function are either associated with risk of radiation (fluoroscopy or computer tomography) or are too complex (transdiaphragmatic pressure measurement, phrenic nerve stimulation, electrophysiology) to be suitable for patients in ICU.[5],[6]

Ultrasonography (USG) is routinely used in ICU for management of critically ill patients. USG has been used for assessment of diaphragmatic functions.[7] Two important parameters which can be used for assessment of diaphragm functions include thickness and movement.[7] Measurement of diaphragmatic thickness has been a focus of research for last few years and is shown to be a good measure of diaphragmatic function.[8] USG can provide an accurate, safe, and easy to perform bedside assessment of the thickness of diaphragm without any additional risk. In addition, USG may be used for serial assessment and may be used for follow-up.

USG is considered as operator dependent; hence, variability of measurements remains a concern. Therefore, establishing the reliability of measurement of diaphragm thickness on USG by critical care physicians is essential before inclusion of this as a diagnostic tool for assessment of diaphragm dysfunction. We conducted this study with the objective to assess intraobserver variability and reliability of the measurement of diaphragm thickness by USG among patients with sepsis.


  Materials and Methods Top


This study was conducted at a tertiary care teaching institute. The study was done following guidelines for research involving human patients.[9],[10] Institutional review board approved the study protocol.

Study patients

This study included adult patients (age ≥18 years) admitted under pulmonary medicine services with a diagnosis of sepsis between March 2015 and December 2016. The diagnosis of sepsis was based on the criteria suggested by SCCM/ESICM/ACCP/ATS/SIS International Sepsis Definitions Conference.[11] Patients who were already diagnosed with any neuromuscular diseases such as myopathy, neuropathy or stroke, and diaphragm palsy, and who refused to participate in the study were excluded from the study.

Equipment

Diaphragmatic thickness measurements were done using B-mode of USG using 5.0 to 13.0 MHz (megahertz) linear array probe (VF 13-5) on Siemens ACUSON X300 Machine (Siemens Medical Solutions Inc., USA).

Thickness measurements

Thickness of diaphragm was assessed as described initially by Cohn et al. and later by other researchers.[12],[13] In brief, patients were made to lie supine and the probe was positioned at 8th or 9th right intercostal space with vertical orientation in the mid axillary line (zone of apposition) and adjusted until the diaphragm was properly visualized. The diaphragm was identified as less echogenic area between the last set of more echogenic parallel lines, the pleural and peritoneal membranes. Then the point corresponding to the center of the probe was marked with a vertical line. This point was used as the reference point for all subsequent measurements. The measurements were made at the end expiration and inspiration. For each patient, three readings of diaphragm thickness were recorded separately during expiration and inspiration.

Statistical analysis

Data were analyzed using statistical software SPSS version 20 (IBM Corp., Armonk, NY) for windows. Mean [standard deviation (SD)] were calculated for variation among multiple readings. Intraobserver reliability was assessed by the intraclass correlation coefficient (ICC). All values are reported as mean ± SD; P < 0.05 was considered significant.


  Results Top


The study included 70 patients with sepsis who satisfied the inclusion criteria. The baseline characters have been summarized in [Table 1].
Table 1 Baseline characteristics of the study cohort

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Total 420 measurements (210 each during expiration and inspiration) from 70 patients were included in the study. The mean (SD) diaphragmatic thickness during expiration and inspiration were 2.35 (0.27) mm and 2.84 (0.32) mm, respectively.

Intraobserver variation

Mean (SD) variation for 1st, 2nd, and 3rd measurement during expiration were 0.233 (0.027) mm, 0.231 (0.029) mm, and 0.233 (0.029) mm, respectively. During inspiration, mean (SD) variations for 1st, 2nd, and 3rd measurement were 0.285 (0.033) mm, 0.283 (0.031) mm, and 0.283 (0.033), respectively.

Intraobserver reliability

Overall ICC for three readings of diaphragmatic thickness during expiration and inspiration were 0.930 (0.898–0.954); P < 0.001 and 0.945 (0.919–0.963); P < 0.001, respectively. The ICC for readings 1, 2, and 3 both during expiration and inspiration are shown in [Table 2]. The correlation is depicted in [Figure 1]a to c and [Figure 2]a to c.
Table 2 Intraclass correlation coefficient (ICC) for diaphragm thickness measurements

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Figure 1 The intraclass correlation (ICC) of diaphragm thickness among 1st and 2nd (a), 1st and 3rd (b), and 2nd and 3rd (c) measurements during at end expiration

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Figure 2 The intraclass correlation (ICC) of diaphragm thickness among 1st and 2nd (a), 1st and 3rd (b), and 2nd and 3rd (c) measurements during at end inspiration

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  Discussion Top


This study showed that there is negligible variability among three measurements of diaphragm thickness taken by a critical care physician. These results were similar for measurements taken during expiration as well as inspiration. Excellent ICC values signify that each measurement has high level of correlation and critical care physicians can measure thickness of diaphragm during both phases of respiration with high degree of reproducibility.

Patients with sepsis are usually critical requiring admission to the ICU and mechanical ventilation. Early extubation and weaning from mechanical ventilation remain a desired goal in these patients. The process of weaning from mechanical ventilation is not smooth in approximately one-third of patients who fails extubation.[14] One of the common reason behind extubation failure is the inability of diaphragm to tolerate the load imposed on it. Detection of this inability of diaphragm to perform function properly would result in better patient selection for extubation and weaning. However, the measurement of diaphragm functions is not easy. Diaphragm is a complex structure hidden inside the body; its changing anatomy with each breath makes it more difficult for assessment of its functions. Measurement of its pressure generating capacity by esophageal and gastric balloon placement or phrenic stimulation is not feasible in day-to-day practice for an average critical care physician.[15] The thickness of diaphragm is one the parameters which can be measured with of USG. USG can be learned easily with minimal training.[16] There are few factors such as angle, depth, and site of measurement which can lead to variations in the measurements done with USG. Probably because of these reasons, USG is still not being used at many centers for assessment of diaphragm thickness in ICU. However, its ease and risk-free nature make it the best tool in such setting. Our results have highlighted that USG can be used for measurement of diaphragmatic thickness in ICU. There were few other studies which have demonstrated the reliability of diaphragm thickness measurement.[12],[13] First report describing the reliability USG for assessment of diaphragm thickness was by Cohn et al.[12] Baldwin et al.[13] also validated the diaphragm thickness measurement. However, both these studies did not include critically ill patients. While we were enrolling patients for our study, Goligher et al.[17] reported a data of 66 patients regarding the feasibility, reproducibility, and validity of the diaphragm thickness measurement by USG. Their results were comparable to our study. All these data suggest that measurement of diaphragm thickness by USG is highly reproducible, and the variability between measurements may be minimized by following a standardized protocol.

This is one is the largest studies done so far for assessment of reliability of diaphragm thickness measurements among patients with sepsis. The diaphragm thickness was measured in both phases of respiration, and the reliability and variability were calculated for both. We also appreciate the limitations of our study. First, radiologists are the most experienced operators of USG and their inclusion as an observer for comparison could have validated the measurements. However, radiologists are usually not present all the time in most of the ICUs. In day-to-day practice, it is the ICU physician who is managing critically ill patients, not radiologists, thus limiting its overall practical utility. In addition, we don’t have a dedicated a radiologist for our ICU, and because of feasibility, we were unable to include radiologist as an observer. Second, all the measurements were taken by a single observer; therefore, this study cannot address the issue of interobserver variations. Previous studies done in ICU has shown that USG is reliable tool for assessment of muscle thickness, including diaphragm.[8],[12],[13],[18] In our experience with 20 patients in whom diaphragm thickness was measured by two critical care physicians separately as a pilot study, we found excellent correlation between the measurements.[19] This indicates that the results are likely to be reproducible. Third, it is a single-center study, so the reproducibility of results at other centers cannot be commented.


  Conclusion Top


We conclude that diaphragm thickness measured using USG by critical care physicians can be done with excellent reliability and minimal variability. These results indicate that USG can be used as an accurate, objective, and easy tool to assess the diaphragmatic functions among critically ill patients with sepsis.

Presentation at a meeting

None.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

 
  References Top

1.
Petrof BJ, Hussain SN.Ventilator-induced diaphragmatic dysfunction: What have we learned? Curr Opin Crit Care 2016;22:67-72.  Back to cited text no. 1
    
2.
Hermans G, Van den Berghe G. Clinical review: Intensive care unit acquired weakness. Crit Care 2015;19:274.  Back to cited text no. 2
    
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Jolley SE, Bunnell AE, Hough CL. ICU-acquired weakness. Chest 2016;150:1129-40.  Back to cited text no. 3
    
4.
Yang Y, Yu T, Pan C, Longhini F, Liu L, Huang Y et al. Endotoxemia accelerates diaphragm dysfunction in ventilated rabbits. J Surg Res 2016; 206:507-16.  Back to cited text no. 4
    
5.
Doorduin J, van Hees HW, van der Hoeven JG, Heunks LM. Monitoring of the respiratory muscles in the critically ill. Am J Respir Crit Care Med 2013;187:20-7.  Back to cited text no. 5
    
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Heunks LM, Doorduin J, van der Hoeven JG. Monitoring and preventing diaphragm injury. Curr Opin Crit Care 2015;21:34-41.  Back to cited text no. 6
    
7.
Umbrello M, Formenti P. Ultrasonographic assessment of diaphragm function in critically ill subjects. Respir Care 2016;61:542-55.  Back to cited text no. 7
    
8.
Zambon M, Greco M, Bocchino S, Cabrini L, Beccaria PF, Zangrillo A. Assessment of diaphragmatic dysfunction in the critically ill patient with ultrasound: A systematic review. Intensive Care Med 2017;43:29-38.  Back to cited text no. 8
    
9.
World Medical Association Inc. Declaration of Helsinki. Ethical principles for medical research involving human subjects. J Indian Med Assoc 2009;107:403-5.  Back to cited text no. 9
    
10.
World Medical Association. Declaration of Helsinki: Ethical principles for medical research involving human subjects. JAMA 2013;310:2191-4.  Back to cited text no. 10
    
11.
Levy MM, Fink MP, Marshall JC, Abraham E, Angus D, Cook D et al. 2001 SCCM/ESICM/ACCP/ATS/SIS international sepsis definitions conference. Crit Care Med 2003;31:1250-6.  Back to cited text no. 11
    
12.
Cohn D, Benditt JO, Eveloff S, McCool FD. Diaphragm thickening during inspiration. J Appl Physiol 1997;83:291-6.  Back to cited text no. 12
    
13.
Baldwin CE, Paratz JD, Bersten AD. Diaphragm and peripheral muscle thickness on ultrasound: Intra-rater reliability and variability of a methodology using non-standard recumbent positions. Respirology 2011;16:1136-43.  Back to cited text no. 13
    
14.
Dot I, Perez-Teran P, Samper MA, Masclans JR. Diaphragm dysfunction in mechanically ventilated patients. Arch Bronconeumol 2017;53:150-6.  Back to cited text no. 14
    
15.
Jung B, Moury PH, Mahul M, de Jong A, Galia F, Prades A et al. Diaphragmatic dysfunction in patients with ICU-acquired weakness and its impact on extubation failure. Intensive Care Med 2016;42:853-61.  Back to cited text no. 15
    
16.
See KC, Ong V, Ng J, Tan RA, Phua J. Basic critical care echocardiography by pulmonary fellows: Learning trajectory and prognostic impact using a minimally resourced training model. Crit Care Med 2014;42:2169-77.  Back to cited text no. 16
    
17.
Goligher EC, Fan E, Herridge MS, Murray A, Vorona S, Brace D et al. Evolution of diaphragm thickness during mechanical ventilation. Impact of inspiratory effort. Am J Respir Crit Care Med 2015;192:1080-8.  Back to cited text no. 17
    
18.
Hadda V, Kumar R, Dhungana A, Khan MA, Madan K, Khilnani GC. Inter- and intra-observer variability of ultrasonographic arm muscle thickness measurement by critical care physicians. J Postgrad Med 2017;63:157-61.  Back to cited text no. 18
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19.
Dhungana A, Khilnani GC, Hadda V, Guleria R. Reproducibility of diaphragm thickness measurements by ultrasonography in patients on mechanical ventilation. World J Crit Care Med 2017;6:185-9.  Back to cited text no. 19
    


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