The Role of Manual Therapy in Patients with COPD

Chronic obstructive pulmonary disease (COPD) is a respiratory condition associated with altered chest wall mechanics and musculoskeletal changes. In this narrative review, we describe the underlying musculoskeletal abnormalities in COPD, the reasons for applying manual therapy techniques, their method of application and clinical effects. A variety of manual therapy techniques have been applied in individuals with COPD, including soft tissue therapy, spinal and joint manipulation and mobilisation, and diaphragmatic release techniques. These have been prescribed in isolation and in conjunction with other treatments, including exercise therapy. When applied in isolation, transient benefits in respiratory rate, heart rate and symptoms have been reported. Combined with exercise therapy, including within pulmonary rehabilitation, benefits and their corresponding clinical relevance have been mixed, the extent to which may be dependent on the type of technique applied. The current practical considerations of applying these techniques, including intense therapist–patient contact and the unclear effects in the long term, may limit the broad use of manual therapy in the COPD population. Further high quality research, with adequate sample sizes, that identifies the characteristic features of those with COPD who will most benefit, the optimal choice of treatment approach and the longevity of effects of manual therapy is required.


Introduction
Chronic obstructive pulmonary disease (COPD) is characterised by dyspnoea and fatigue, which are linked to reduced exercise tolerance and impaired health-related quality of life (HRQOL) [1,2]. Extrapulmonary manifestations of this condition, including musculoskeletal dysfunction, have been described in COPD [3], originating from respiratory pathophysiology and changes in musculoskeletal structures. Clinically, individuals with COPD may present with postural abnormalities, musculoskeletal pain or other symptoms, which warrant further treatment and lend support to the possible role of manual therapy. This narrative review explores the origins of the musculoskeletal changes that are targeted by these techniques, the types of techniques, their methods of application and effects and the clinical applicability to the COPD population.

Musculoskeletal Changes Associated with COPD
To understand the role of manual therapy in this population, it is important to evaluate the musculoskeletal changes which occur in COPD. This condition is characterised by respiratory muscle non-contractile tissue repair, extensibility or stability, reducing soft tissue swelling, inflammation or restrictions, facilitating movement and improving function.
Manual therapy has been used to address the musculoskeletal anomalies in COPD. Clinical studies using these techniques are shown in Table 1. Techniques have been applied to the cervical and thoracic vertebral and costal joints, as well as the anterior and posterior chest wall/trunk and upper limb muscles. Manipulation and mobilisation involves the graded delivery of low or high velocity low amplitude joint mobilisation to the thoracic intervertebral, costovertebral and costotransverse joints at identified regions of spinal stiffness or observation of abnormalities in the paravertebral tissues [34]. When applied in COPD, the underlying reasoning is that these mobilisation strategies will temporarily improve chest wall compliance, addressing one element contributing to chest wall rigidity. Soft tissue therapy techniques that have been applied in COPD include effleurage, trigger points, cross fibre frictions and myofascial release [35][36][37]. The techniques are believed to encourage vasodilation and smooth muscle relaxation and to increase blood flow, which may assist in improving range of motion, reducing pain and promoting changes at the tissue level [38].

Application of Manual Therapy in COPD
Despite limited publication in this area, current evidence highlights the potential benefit of manual therapy in COPD. Within these studies, from a practical perspective, techniques have been generally applied in combination, and the effects have been observed when administered in a single treatment session, over a series of treatments and in conjunction with other management, such as pulmonary rehabilitation. In the majority of cases, the therapist directly applies the techniques, with the occasional use of instrument-assisted spinal manipulation [39].
One of the earliest studies [40] investigated the immediate effects of a single 20 min treatment session, using seven standardised osteopathic manipulative techniques (e.g., soft tissue therapy to the paraspinal muscles, rib raising, sub-occipital decompression, thoracic inlet myofascial release, and pectoral traction). Thirty minutes following the treatment, respiratory function (inspiratory capacity, residual volume (RV) and RV as a proportion of total lung capacity (TLC)) increased, but forced expiratory flow at 50% and 75% of vital capacity was reduced. This mixed impact on respiratory function makes it difficult to determine the direct benefit or harm of each of the individual techniques. A slightly longer single treatment session (45 min) to people with severe to very severe COPD consisted of manual therapy to the cervical and thoracic spinal joints, scapulo-thoracic mobilisation, rib raising and myofascial release [41]. The full treatment protocol is outlined in Table 1. In contrast to the earlier study [40], improvement in spirometry and respiratory muscle strength were noted immediately post treatment, as a well as a decrease in heart rate and respiratory rate, and lower perceptions of dyspnoea and fatigue [41]. Despite some evidence of benefit, these approaches have not gained clinical acceptance due to the small sample sizes and the limited duration of effect immediately following treatment.   There have been studies which have compared the effects of either soft tissue therapy alone; in combination with spinal manipulation; or soft tissue therapy, spinal manipulation and exercise therapy [34,35]. In each of these studies, a longer duration of treatment (ranging from four to eight weeks) was applied. The specific techniques used in each protocol are outlined in Table 1 and were generally applied over a series of treatment sessions. All three therapies (soft tissue, spinal manipulation and exercise) combined improved FVC beyond the defined minimal important difference that is considered clinically relevant for this measure, and this was perceived to be the result of a synergistic interaction between the interventions [36]. This may account for the reduced dyspnoea and improved exercise tolerance based on a modified form of the 6 min walking test with both soft tissue therapy and spinal manipulation with and without exercise [34]. A slight variation on this combination compared pulmonary rehabilitation, soft tissue therapy and pulmonary rehabilitation, and spinal manipulative therapy and pulmonary rehabilitation [35] with the manual therapy applied during weeks 4 to 12 of the pulmonary rehabilitation program. It has been well established that pulmonary rehabilitation improves symptoms, exercise capacity and quality of life in people with COPD, with no change in respiratory function [44]. However, this study demonstrated that the addition of soft tissue therapy and spinal manipulation to a pulmonary rehabilitation program significantly improved respiratory function (FVC) at 24 weeks, although there was no effect on functional exercise capacity, anxiety, depression or quality of life. The clinical value of improving FVC with these adjunctive treatments from a patient's perspective is largely unclear [45]. Despite this, the reduction in dyspnoea, according to a valid and reliable measurement tool evident in one study, and increase in walking distance lends support to the possible advantages in selected outcomes. Although the evidence of some improvements suggests that these techniques may be helpful across the spectrum of COPD when applied using a uniform, structured approach, the benefits appear to be short term, with no long term follow up in these studies.
An alternative approach was applied by Zanotti et al. [42] and was described as treatment to address any dysfunction observed in the thoracic outlet, spine, ribcage, thoracic and pelvic diaphragm, tentorium cerebelli, and cranio-sacral regions. Like Engel in two previous studies [34,35], this was applied during a pulmonary rehabilitation program. Greater improvements in exercise capacity and reduction in RV were noted compared to those attending pulmonary rehabilitation alone [42]. Compared to the uniform approach to treatment applied in previous studies [34,35], it is possible that by basing a treatment on assessment findings, this may enable a more directed treatment that is appropriate for each individual, and may account for improvement in this patient related outcome of exercise capacity.
In contrast to manual therapies focused on the thoracic spine and rib cage, an alternative focus is muscle release techniques. Diaphragm release techniques in people with clinically stable COPD have been investigated over a series of six sessions [43]. In this technique, manual contact is applied bilaterally to the underside of the 7th to 10th rib costal cartilages by a therapist, who applies a cephalic and lateral pull during inspiration, accompanying rib elevation. This pressure is maintained during expiration, with the therapist deepening contact towards the inner costal margin. Depth of contact is increased in subsequent breaths. It is hypothesised that this contact allows cranial-directed traction of the ribs, along with lengthening of the diaphragm near its insertion around the anterior costal margin, produced by the compression of the diaphragm fibres in this area. The lengthening of the diaphragm, in combination with the therapist-facilitated movement of the ribs, is thought to improve the mobility of the diaphragm. The results found a cumulative increase in diaphragm mobility (measured by ultrasound) by 18 mm, and an improvement in inspiratory capacity. In addition, functional exercise capacity measured by the 6 min walk distance (6MWD) improved by 15 m with diaphragmatic release, compared to a deterioration of 6 m in the control group [43]. As inspiratory capacity is closely linked to the ventilatory demands of exercise [46], and the improvement in 6MWD of 22 m is within close proximity of the clinically relevant minimal important difference of this outcome in people with COPD [47], this suggests a potential clinical benefit. The observation of only cumulative effects highlights the need for repeated treatment.

Clinical Considerations and Limitations of Manual Therapy in COPD
In view of these findings, it is important to consider the practical aspects of these approaches and their clinical relevance. Beyond muscle soreness that resolved within 24-48 h, no adverse events have been noted with therapist-directed manual therapy [34,39]. Patient tolerability of repeated manual therapy intervention is important as it is likely required for clinical improvement.
It is essential to consider the time and therapist-dependent effort involved to deliver the treatments, particularly when the benefits may only be achieved through multiple applications over the course of a number of weeks. Each of these treatments is labour and time intensive. With the broad prevalence of COPD, this is likely to limit their use in clinical practice. The additional element of treatment burden on patients, particularly those already engaged with pulmonary rehabilitation or other therapeutic approaches with known benefit, and financial cost to the patient should also be considered.
The temporary improvements in respiratory function and symptoms following a single treatment session highlights that these techniques are targeting regions of musculoskeletal dysfunction. The diaphragmatic release technique is associated with improvement in diaphragmatic mobility, vital capacity and functional exercise tolerance when applied over a series of sessions [43]. Although only examined in one study, these findings support future examination of this technique, either applied independently or in conjunction with other types of manual therapy. The mixed results for symptoms of dyspnoea, functional exercise capacity, psychological symptoms, quality of life and lung function when manual therapy was applied as an adjunct to exercise therapy or pulmonary rehabilitation highlight important clinical practice points. With benefits in selected measures of lung function achieved using a mix of techniques, it is difficult to identify from the current studies whether there is a superior technique. The lack of consistency in improvement in functional exercise capacity with adopting a uniform approach to treatment [34,35], compared to selecting techniques based on an individual assessment [42], favours a patient-focused intervention. However, with the small number of participants included in each of these studies, further high quality clinical trials with sufficient sample sizes across multi-centre sites, and consistent use of valid and reliable outcome measures with blinded assessors is required to clarify this information. The precise mechanisms of action of each technique or combination of techniques is largely inferred. Establishing the effect on alternative measures of respiratory function, including chest wall expansion [48], may offer further insight into the mechanisms of action of each technique or combination of techniques. Finally, as the longest follow up period was 24 weeks in the current research [35], establishing the longer term effects of manual therapy in this population is necessary.
It may be considered a strength of all studies that individuals were included regardless of disease severity or degree of chest wall rigidity, postural abnormalities or experiences of pain. There was no additional screening of individuals with COPD for underlying musculoskeletal dysfunction, postural evaluation or identification of musculoskeletal pain within the thoracic region in these studies. However, the intensive nature of the treatment suggests that it may be astute to explore the characteristics of those individuals who may achieve the most optimal outcomes. A range of tools to assess postural dysfunction and pain are available, have been validated in the COPD population [49,50], and could be applied to identify those who might benefit most from manual therapy treatments.
In conclusion, musculoskeletal changes of altered chest wall mechanics, postural changes and pain are features of COPD, and it is important to identify treatment options that may address these abnormalities. Manual therapy techniques applied during a single treatment sessions have demonstrated some benefit in physiological parameters and symptoms. When applied in combination with exercise therapy or pulmonary rehabilitation, there has been mixed reports of improvements in selected measures of lung function and functional exercise capacity. However, the acceptance and role of manual therapy within clinical practice is limited by the labour and time intensity of individual treatment sessions, the lack of clarity of the optimal approach to treatment technique selection, the small participant numbers and the absence of long term follow up of clinical effects. Further examination to identify the characteristics of those with COPD who will most benefit from manual therapy, the optimal types of treatment approaches and their cost effectiveness, the ideal prescription and the longevity of effects is required.
Author Contributions: S.C. and A.L.L. drafted the manuscript, approved the submitted version and agree to be personally accountable for its contents. P.E.M. critically reviewed the manuscript, approved the submitted version, and agrees to be personally accountable for its contents.