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 Table of Contents  
ORIGINAL ARTICLE
Year : 2020  |  Volume : 4  |  Issue : 2  |  Page : 251-255

Assessment of M-mode index of obstruction in patients with chronic obstructive pulmonary disease


Department of Chest Diseases, Faculty of Medicine for Girls, Al-Azhar University, Cairo, Egypt

Date of Submission18-Feb-2020
Date of Decision28-Feb-2020
Date of Acceptance01-Mar-2020
Date of Web Publication29-Jun-2020

Correspondence Address:
MD Eman Sobh
Chest Diseases Department, Faculty of Medicine for Girls, Al-Azhar University, Al-Zahraa University Hospital 11517 Abbaseya, Cairo
Egypt
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/sjamf.sjamf_27_20

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  Abstract 


Background Diaphragm motion during forced expiration can be analyzed using M-mode ultrasound in an anterior subcostal approach. Maximal expiratory diaphragmatic excursion and forced expiratory diaphragmatic excursion in the first second physiologically mimic forced vital capacity (FVC) and forced expiratory volume in the first second (FEV1), respectively, and may be used as a marker of obstruction.
Aim The aim of the work was to assess the role of the M-mode index of obstruction (MIO) as a screening test (tool) for chronic obstructive pulmonary disease (COPD).
Patients and methods This case–control study involved 200 participants (100 patients with COPD and 100 age-matched and sex-matched healthy controls). The authors performed spirometry and the diaphragm ultrasonography, during forced expiration. MIO was calculated as the slope of diaphragmatic excursion in first second/slope of diaphragmatic excursion at end of expiration.
Results Diaphragmatic excursion was significantly lower in COPD group than control group (4.27±1.49 vs 5.36±1.67 for slope in the first second of expiration, 4.82±1.55 vs 5.72±1.57 for maximum slope at the end of expiration, 4.42±1.53 vs 5.44±1.69 for velocity of diaphragm contraction in first second, and 2.40±1.04 vs 3.52±1.26 for velocity of diaphragm contraction at the end of expiration; P=<0.001) with delayed relaxation time (2.34±0.73 vs 2.08±0.65 for COPD and control groups, respectively). MIO was significantly lower in COPD than the control group (88.46±9.92 vs 93.37±11.15 respectively, P=0.001) and showed a significant positive correlation with FEV1/FVC (P=0.007).
Conclusion Diaphragmatic excursion during forced expiration is significantly decreased in COPD in comparison with the control group. MIO is significantly lower in COPD in comparison with control and significantly correlated with FEV1/FVC.

Keywords: diaphragm ultrasound, forced expiratory diaphragmatic excursion in first second, maximal expiratory diaphragmatic excursion, M-mode index of obstruction, spirometry


How to cite this article:
Qutb SF, Elsawy SB, Sobh E, Oraby SS. Assessment of M-mode index of obstruction in patients with chronic obstructive pulmonary disease. Sci J Al-Azhar Med Fac Girls 2020;4:251-5

How to cite this URL:
Qutb SF, Elsawy SB, Sobh E, Oraby SS. Assessment of M-mode index of obstruction in patients with chronic obstructive pulmonary disease. Sci J Al-Azhar Med Fac Girls [serial online] 2020 [cited 2020 Jul 11];4:251-5. Available from: http://www.sjamf.eg.net/text.asp?2020/4/2/251/288272




  Introduction Top


Chronic obstructive pulmonary disease (COPD) is one of the most common chronic diseases associated with morbidity and mortality all over the world [1]. Inspiratory muscle weakness in patients with COPD is important in clinical settings [2]. The diaphragm is the main initiator of tidal breathing, so it is the main focus for assessment of inspiratory muscle function [3]. Respiratory muscle weakness in COPD may be attributed to hyperinflation, systemic inflammation and/or secondary to heart failure, long-term steroid use, muscle deconditioning, malnutrition, and electrolyte disturbances [4]. The airflow limitation and hyperinflation lead to geometric changes in the thorax, so the diaphragm works against an increased workload [5]. The diagnosis of COPD depends on the detection of chronic partially reversible airflow limitation by spirometry (gold standard test). It is a noninvasive, reproducible, available, and objective technique [6].

The ultrasound study of the chest is a fast growing promising field. The diaphragm can be visualized as a thick hyperechoic line with B-mode ultrasonography [7]. Diaphragm movements can be measured by M-mode during inspiration and expiration. So the range of movement can be measured as the diaphragmatic excursion [8]. The M-mode representation of a forced expiratory maneuver (after a maximal inspiration) is characterized by an initial drop off followed by a plateau in maximum expiration. It is similar to the volume/time curve in spirometry technique. The diaphragmatic excursion in M-mode during forced expiration in healthy participants and in patients with COPD revealed that the initial drop off in expiration was steeper in healthy participants than in those with COPD reflecting delayed diaphragm relaxation [9]. The measurement of the forced expiratory diaphragmatic excursion in the first second (FEDE1st) and the maximal expiratory diaphragmatic excursion (EDEMax) was done, which represent the percentage of diaphragmatic excursion in the first second compared with the total excursion and can be analogous to forced expiratory volume in first second (FEV1) and forced vital capacity (FVC), respectively. Then, M-mode index of obstruction (MIO) (FEDE1st/EDEMax ratio) was calculated. This M-mode index is simple and reproducible [10]. Previous studies reported that the values of MIO are lower in airway obstruction than in normal conditions owing to slower relaxation of the diaphragm in expiration as a result of air trapping and increased airway resistance [10].

Ethical consideration

This study was approved by the institutional review board and ethics committee of the Faculty of Medicine for Girls Al-Azhar University (IRB-AFMG), Cairo, Egypt. Informed consent was obtained from each participant. All participants had the right to withdraw from the study at any time during his/her participation. All data were kept confidential.


  Patients and methods Top


Type and place of the study

This observational prospective case–control study was conducted at Chest Diseases Department, Al-Zahraa University Hospital, between September 2018 and September 2019.

Inclusion criteria

The study was conducted on 200 adult participants classified into two groups: group 1 included 100 patients with chronic obstructive pulmonary disease, and group 2 included 100 healthy controls with normal lung function. Diagnosis of patients with COPD was based on criteria established by Global Initiative for Chronic Obstructive Lung Disease (GOLD) and had post-bronchodilator FEV1/FVC% less than 70%, with an increase in FEV1 less than 12% of baseline value or less than 200 ml, 15–20 min after 4 puffs (400 µg) of inhaled salbutamol via metered dose inhaler [6].

Exclusion criteria

Those with a history of neuromuscular disease, stroke, trauma to chest or abdomen or diaphragm injury, recent abdominal surgery, thyroid disorders, radiation therapy, malnutrition, and persons with severe clinical illness were excluded from the study.

All participants were subjected to the following:
  1. History taking and clinical examination.
  2. The BMI was calculated [weight (kg)/height (m2)].
  3. Spirometry was carried out according to European Respiratory Society/American Thoracic Society (ERS/ATS) recommendations [11]. We used office spirometer (Spirosift spirometer 5000; FUKUDA, Nenshi, Japan). The best of the three technically acceptable trials was used for analysis. We recorded first secondFEV1% predicted, FVC% predicted, forced expiratory flow rate at 25–75% of vital capacity (FEF25–75%predicted), and FEV1/FVC ratio. Postbronchodilator data were used for the diagnosis of COPD according to GOLD guidelines [6].


Thoracic ultrasound

All ultrasonographic examinations were done in a semi-recumbent position. We used ultrasound device equipped with a 3.5-MHz curvilinear probe for diaphragm examination (SSI6000 Sonoscape; Nanshan, China). We used Brightness mode (B-mode) to identify diaphragm and to assess position and Motion mode (M-mode) to assess diaphragmatic motion or excursion. We only studied the right hemidiaphragm owing to difficulties in imaging of left hemidiaphragm by ultrasound, in anterior subcostal view or at anterior axillary line with transducer directed cranially, medially, and dorsally to focus the ultrasound beam ([Figure 1]). The diaphragm is seen as white hyperechoic curved line moving with respiration. We activated M-mode and used the cursor to cross diaphragm line. Participants were asked to take a deep breath till the diaphragmatic line goes up and reaches a plateau in maximal inspiration ([Figure 2]). Then, they performed maximal open mouth expiration: the diaphragmatic line has an initial drop off followed by a plateau at the end of expiration. On frozen image, we can measure the FEDE1st and the EDEMax, as seen in [Figure 2]. MIO can be calculated as the ratio FEDE1st/EDEMax [10].
Figure 1 Diaphragm examination.

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Figure 2 Measurement of diaphragmatic excursion in the first second of forced expiration and maximum expiration.

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Statistical analysis

Data were statistically analyzed by the Statistical Package for the Social Sciences (SPSS) program version 17.0 (SPSS Inc., Chicago, Illinois, USA). Descriptive analysis was done for each item, and the results were expressed as mean±SD or number (percentages). We used the χ2-test, the analysis of variance test, and Student t-test for comparisons as appropriate and linear correlation coefficient for the detection of a correlation between two quantitative variables. Statistical significance was considered at a P value less than 0.05 (confidence limit 95%).


  Results Top


This study was conducted in Chest Disease Department, Al-Zahraa University Hospital Cairo, Egypt, between September 2018 and September 2019. The CONSORT of the study is shown in [Figure 3]. Both groups were age and sex matched. Pack/year smoking was significantly higher in the COPD group (P<0.001). Demographic data are presented in [Table 1]; pulmonary function test and arterial blood gases are shown in [Table 2] and [Table 5].
Figure 3 CONSORT of the study.

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Table 1 Demographic data and basic characteristics of studied groups

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Table 2 Pulmonary function tests and arterial blood gases in both groups

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Diaphragm ultrasound examination during forced FVC maneuver showed that the slope of FEDE1st and maximal expiratory diaphragmatic excursion were highly statistically significantly lower in COPD in comparison with control group (P<0.001) ([Table 3]). Diaphragm ultrasound parameters during forced FVC maneuver showed that the velocity of FEDE1stfirst second and the velocity of the maximal expiratory diaphragmatic excursion were significantly lower in COPD in comparison with control group (P<0.001). Calculating the MIO showed statistically significant differences between COPD and the control groups (P=0.001) ([Table 3]). In all studied populations, MIO was significantly correlated to FEV1/FVC (P=0.007) ([Table 4]).
Table 3 Diaphragm ultrasonography during the forced expiratory maneuver in both groups

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Table 4 Correlation between FEV1/FVC and M-mode index of obstruction

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Table 5 Correlation between M-mode index of obstruction and FEV1 in COPD group

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  Discussion Top


The proper diagnosis of COPD depends on the detection of irreversible airflow limitation, and spirometry is the gold standard for diagnosis of airflow obstruction [6]. However, spirometry is effort dependent and needs patient cooperation and proper training to do the test. The aim of this study was to study the ultrasonographic MIO as a new screening tool for the diagnosis of COPD. Previous studies on diaphragm kinetics have assessed the values of excursion in resting and deep breath, finding correlations with lung function [8], but few studies have investigated the difference between normal and obstructive patterns. We studied diaphragm ultrasound parameters during FVC maneuver and found that slope and velocity of diaphragmatic excursion in the first second and maximal diaphragmatic excursion were significantly lower in COPD in comparison with control group (P<0.001) ([Table 3]). Similar results were reported in previous studies. Previous studies examined the diaphragm movement in COPD and reported impaired diaphragm movement in comparison with healthy controls [10].

The results of our study showed a limitation of diaphragm relaxation during forced expiration in patients with COPD in the form of decreased slope and velocity of diaphragmatic excursion in the first second and at maximum expiration ([Table 3]). The possible explanation of these findings could be the presence of airflow limitation in forced expiration. During forced expiration, higher intrathoracic pressure is generated; in the presence of airflow obstruction, the airflow exiting the airway is limited, so that alveolar emptying and intrathoracic pressure reduction are slower than in healthy participants, causing a delay in diaphragm relaxation.

In this study, MIO was significantly lower in COPD in comparison with the control group ([Table 3]). Thus, we can interpret MIO as an index of the speed of diaphragm relaxation that seems to be slower in patients affected by airway obstruction.

The results of this study demonstrated that diaphragm ultrasound may represent a similar curve to that of the FVC technique, and the values are greatly diminished in COPD. There was a statistically significant positive correlation between MIO and FEV1/FVC when all populations were tested ([Table 4]). Zanforlin et al. [10], showed a significant positive correlation between MIO and FEV1/FVC. A study using ultrasound measurement of craniocaudal displacement of the left branch of the portal vein in B-mode during forced inspiration and expiration reported a correlation between reduced diaphragm craniocaudal mobility and air trapping in patients with chronic obstructive pulmonary disease [9].

The study by Zanforlin et al. [10], reported that MIO was less than 77% as a possible cutoff point for suspecting airway obstruction with of 95.5% positive predictive value.

Our study showed that the best cutoff point to detect COPD cases regarding MIO was found less than or equal to 97.66% with a sensitivity of 86.0%, specificity of 42.0%, and area under the curve of 64.4%. Although the sensitivity and specificity are low, this test is simple and reproducible and can be done even in uncooperative patients. To confirm that MIO can be used as a diagnostic tool for COPD, it must be tested on a large cohort. At the same time, ultrasound maneuver was done with open mouth, which is easier than spirometry, which needs a closed mouth and mouthpiece.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
  References Top

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Dos Santos Yamaguti WP, Paulin E, Shibao S, Chammas MC, Salge JM, Ribeiro M et al. Air trapping: The major factor limiting diaphragm mobility in chronic obstructive pulmonary disease patients. Respirology 2008; 13:138–144.  Back to cited text no. 9
    
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Zanforlin A, Smargiassi A, Inchingolo R, Valente S, Ramazzina E. Ultrasound in obstructive lung diseases: the effect of airway obstruction on diaphragm kinetics.A short pictorial essay. J Ultrasound 2015; 18:379–384.  Back to cited text no. 10
    
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    Figures

  [Figure 1], [Figure 2], [Figure 3]
 
 
    Tables

  [Table 1], [Table 2], [Table 3], [Table 4], [Table 5]



 

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