Kimberley Sevasta^*, Tonio.P Agius and Anabel Scirih
^*Correspondence: Kimberley Sevasta, Department of Physiotherapy, University of Malta, Malta, Email:

Received: 01-Mar-2023, Manuscript No. ajrm-23-90569; Editor assigned: 03-Mar-2023, Pre QC No. ajrm-23-90569 (PQ); Reviewed: 17-Mar-2023, QC No. ajrm-23-90569; Revised: 22-Mar-2023, Manuscript No. ajrm-23-90569 (R); Published: 29-Mar-2023, DOI: 10.54931/1747 5597.22.18.80

Keywords

Chronic obstructive pulmonary disease; Physiotherapy, Pulmonary hyperinflation

Introduction

COPD is a progressive and irreversible respiratory condition characterised by expiratory flow limitation which results in air trapping and pulmonary hyperinflation. This leads to musculoskeletal alterations, forcing the diaphragm and intercostal muscles to operate in a mechanically disadvantageous position. For the diaphragm to operate in an optimal manner, its muscle fibers must be able to progressively overlap so as to form cross bridges which increase their contraction force. Following contraction of the diaphragm, cross bridges are broken so that the muscle can return to its dome-shaped position. As a result of the diaphragm being in a shorter and more flattened position, an adequate contractile force is diminished. Following these chronic adaptations, respiratory muscles work at their full capacity to meet the ventilator demands, increasing the work of breathing, resulting in recruitment of the accessory muscles of respiration in compensation. The accessory muscles of respiration adapt to this increased workload by shortening and becoming overactive, resulting in limited upper limb and cervical mobility. This may result in the patient experiencing shortness of breath. Moreover, changes in chest wall rigidity and muscular function may cause postural changes and alterations in rib cage configuration which can result in increased thoracic kyphosis.^1-4

Muscle Energy Techniques (METs) are being considered as adjunctive tools in the management of patients with COPD, but their effectiveness has not been well evaluated.

Background

METs are a type of manual therapy used to improve joint mobility, stretch tight muscles and fascia, improve circulation, and decrease pain. During the application of METs, an isometric contraction targeting the tight muscle is performed, activating the inhibitory Golgi Tendon Organs within the same muscle.^5,6

Studies are investigating the use of METs as an adjunct to other treatments such as self-stretching exercises, chest mobility exercises and/or breathing exercises, aerobic training and pulmonary rehabilitation to help manage the over-activation of accessory muscles of respiration. By increasing muscle length and range of motion of these accessory muscles, a decrease in thoracic wall stiffness was observed by Clarke et al. leading to improvements in Forced Expiratory Volume in 1 second (FEV1), reduction in respiratory rate and increase in oxygen saturation. Unlike any other manual therapies that assists in muscle lengthening such as passive stretching, high velocity manipulation and massage, METs requires the active participation of the patient. Moreover, it is a safe method which avoids minor or major adverse effects, with the most serious potential side effect of high velocity manipulation being neurovascular complications.^1-3,7,8

Therefore, seeing the information above, this review aims at critically analysing literature which investigates the application of METs with another physiotherapy treatment focusing mainly on changes in pulmonary function, chest expansion and exercise tolerance as primary outcome measures.

Aims

This review aims to determine if METs intervention when used as an adjunct to other physiotherapy interventions result in improvements in pulmonary function, chest measurement and functional endurance. The research question therefore states ‘Are METs effective at improving pulmonary function, exercise tolerance and chest expansion in persons living with COPD?’

Search methods

A narrative review design was chosen in this study allowing for a more comprehensive research.

The review used the population (P), intervention (I), comparator (C) and outcome (O) (PICO) framework to guide inclusion criteria and report the study characteristics. Papers retrieved for this review were obtained following a thorough search using Google Scholar, PubMed, Medline, Research Gate and Embase databases.

Table 1 illustrates the key PICO search terms. Data was extracted and critically appraised using a critical appraisal skills programme (CASP tool) to facilitate quality research appraisal. The following information was extracted throughout this process: characteristics of the study (participants and sample size), intervention and control group treatment, and results.

Search strategy

The search strategy yielded 1,092 research articles following a preliminary search through the selected databases. After removal of duplicates (n=614) and of irrelevant studies (n=455), 23 full-text randomized-control trial with pretest and post-test experimental design articles were kept as potentially relevant after title screening. Studies were then screened as per the inclusion and exclusion criteria (Table 2).

Study selection and quality appraisal

A total of 7 articles were then accepted for this narrative review. Tables 3 and 4 provide a summary of 7 articles discussing the effects of METs as adjuncts to self-stretching exercises, chest mobility exercises, breathing exercises, breathing and chest mobility exercises, aerobic training and pulmonary rehabilitation.

Results

Outcome measures used in these interventions

The identified studies focused on 3 outcome measures being pulmonary function, chest measurements and functional endurance capacity. FEV1 was investigated in 4 studies [Dave, Thaker and Gondaliya, 2019 (P=0.001), Sule, Kakade and Palekar, 2017 (P=0.001), Rakesh and Jibi, 2016 (P<0.001), Zanotti et al., 2012 (P>0.5)], Forced vital capacity (FVC) was investigated by 3 studies [Dave, Thaker and Gondaliya, 2019 (P=0.003), Rakesh and Jibi, 2016 (P<0.001), Zanotti et al., 2012 (P>0.5)], FEV1/FVC ratio was measured in only 1 study (Dave, Thaker and Gondaliya, 2019 (P=0.221)) and another study Zanotti et al., 2012 used residual volume (P=0.05) as outcome measures. Three of the 4 studies observed statistically significant improvements when combining METs intervention to other physiotherapy treatments in FEV1 and FVC, with FEV1/FVC ratio and residual volume. Vital capacity was also reported to have more marked statistical improvements for the intervention group when compared to the control group; however results were not statistically significant, with the author not providing p values.^3,9-11

Four studies [Dave, Thaker and Gondaliya, 2019 (P=0.001), Krishna et al., 2018 (P=0.001), Rakesh and Jibi, 2016 (P<0.001) and Anand, Narwal and Sindhwani, 2013 (P=0.001)] looked at changes in chest measurements prior and following METs intervention. Both the control group who received conventional physiotherapy treatment and the intervention group, who received METs intervention together with conventional treatment, resulted in improvements in outcome measurements but the intervention group had statistically significant improvements.^9,10,12

Functional endurance capacity was then investigated in 3 papers [Wada et al., 2016 (P<0.001), Anand, Narwal and Sindhwani, 2013 (P=0.001), Zanotti et al., 2012 (P=0.04)]. All 3 studies performed the 6-minute walk test (6MWT) as an outcome measure. Greater statistically significant improvements were observed for the intervention group in all the 3 studies when compared to the control group.^11-13

Critical evaluation of articles

All studies included had an unclear risk of bias and limitations in reporting quality when assessed using the Cochrane- risk-of-bias 2.0 tool (Cochrane RoB 2) for randomised trials. Four studies reported adequate random sequence generation; another study did not provide detail on patient selection, while the other 2 studies used purposive sampling method. Two studies used an appropriate method of allocation concealment, while the other studies were judged at unclear risk of bias because they omitted details relating to allocation concealment. In six of the included studies, blinding of participants and personnel was not described despite the use of a sham control, making it unclear whether the lack of blinding would influence outcomes. Only one study specified that assessors of outcome measures were blinded. All of the studies had published protocols, therefore, the selective outcome reporting domain was judged at a low risk of bias (Figures 1 and 2).

Discussion

This review provides information on the effects of METs in combination to physiotherapy, results which show favourable improvements in pulmonary function, chest measurements and exercise capacity in patients suffering from COPD. Previous systemic reviews focused on investigating the effect of manual therapy including massage, high velocity manipulation and rib cage mobilisation on pulmonary function and exercise capacity or the effects of METs on lung function and exercise capacity as outcome measures. As a result of the small number of studies, limited sample size, difference in METs treatment and methodology, and unclear risk of bias, potential improvements reported should be considered with caution.^7,14

Improvements in lung function measures following MET interventions have been attributed to lengthening of the accessory muscles. Modifications to the muscle tissue properties were observed through an increase in sarcomere size and muscle viscoelasticity. Therefore, by reducing muscular, ligament and fascial tonicity to the cervical and thoracic musculature, improvements in the passive component of expiration in patients diagnosed with COPD was reported. This is because of a reduction in the inspiratory block sustained following alteration in ribs position. Further information about patient demographics, methods of analysis and comparison of results would have improved the validity and reliability of outcomes from studies by Sule, Kakade and Palekar (2017) and Rakesh and Jibi (2017). Knowing the patient’s age, severity of their condition and smoking history allows for the identification of which patients would benefit most from such techniques and whether there are any influential factors which might possibly impact outcomes. Moreover, such information would help determine if the participants in a study are a representative sample of a particular population leading to generalisation.^1,3,10,15

METs are also reported to lead to an increase in the muscle viscoelasticity and accommodation of the muscle spindle, factors which reduce muscle stiffness, improve muscle performance, and increase thoraco-abdominal mobility. Wada et al. (2016) further reinforce that stretching helps modify thoraco-abdominal mobility better when compared to aerobic training. The METs group showed an increase in lung volume, which is associated with a greater abdominal contribution.^3,14

Apart from improvements in lung function measures, the integration of METs and chest mobility exercises resulted in significant improvements in chest expansion. Dave, Thaker and Gondaliya (2019) reported that these results were due to the attainment of an adequate length in the accessory muscles of respiration obtained with this intervention. These factors led to an increase in thoracic expandability and an improvement in muscle contractile capacity, resulting in better respiratory muscle performance and improved respiratory mechanics. Moreover, muscle stretching is known to stimulate the Golgi tendon organs, causing an inhibitory effect leading to an increase in muscle fibre length, thereby decreasing the overlap between actin and myosin filaments. As a result of all these changes, improvements in muscle viscoelasticity takes place which increases muscle contractile efficiency.^9,16,17

Krishna et al. (2018) also documented improvements in chest expansion which have been attributed to the release of the muscle spasm. In some patients suffering from COPD, intercostal muscle spasm is observed, a factor which is reported to lead to strenuous breathing and decreased chest expansion. METs address these changes by reducing pain as a result of neuro-inhibitory effect which leads to reduction of muscle spasm. The decrease in chest expansion 24 hours post-intervention in both the intervention group and the control group was then associated to exercise induced muscle soreness reported by all participants. Though Krishna et al. (2018) failed to provide a reason behind the improvements observed in the conventional group after treatment, it was reported by Rehman et al. (2020) that following aerobic exercises better oxygenation and distribution of oxygen takes place which leads to improvements in chest expansion.^9,10,16,18

The addition of METs to Pulmonary Rehabilitation also resulted in better improvements in functional exercise endurance and chest expansion when compared with the control group. Improvements in exercise endurance have been attributed to an increase in chest mobility, as well as changes in ventilator capacity through accessory muscles of respiration stretching. The resultant improved ventilation, especially in the lower lobes, led to increased exercise tolerance and endurance. This is important as by reducing respiratory muscle overuse, apical breathing, which requires up to 30% of the body’s energy, is decreased by promoting more diaphragmatic breathing, a breathing pattern which requires less than 5% of the body’s energy. Therefore, through respiratory muscle stretching, mechanical advantage is regained as the muscles work at optimal position and increase ribcage compliance which leads to decreased energy expenditure.^12,18-21

Key Points

1. This review provides evidence that METs techniques show favourable improvement when integrated to self-stretching group.

2. This review provides evidence that METs techniques show favourable improvement when combined with chest-mobility exercises and/or breathing exercises.

3. This review provides evidence that the integration of METs techniques show favourable improvement when combined with pulmonary rehabilitation.

4. There is a gap in research investigating the effects of METs technique as an adjunct to physiotherapy treatments without high risk of bias.

Limitations of Review

Small sample population was used in the majority of the studies reviewed making these results potentially not reflective to the target population and in certain instances, minimal details provided regarding the intervention and levels used for chest expansion measurements. Reproducibility and validity of study would be aspects which need to be questioned and further looked into making the results of this narrative review interpreted with caution. Lack of heterogeneity in the studies reviewed is observed that might influence the outcomes.

Conclusion

From this review insufficient evidence to support the role of METs intervention in patients with COPD was observed. This is because the studies reviewed included small sample sizes and were at an unclear risk of bias. The use of METs as an adjunct to the management of some common COPD symptoms is thought to be promising on outcomes of pulmonary function, chest measurements and functional exercise capacity. However, further research is merited to examine the potential use of MET intervention in the management of COPD.

Funding

This research received no specific grant from any agency in the public, commercial or not-for-profit sectors.

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