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Correspondence to: Hsiang-Chu Pai, PhD, RN, Professor, Department of Nursing, Chung-Shan Medical University, Chung-Shan Medical University Hospital, No. 110, Sec.1, Jianguo N.Rd., Taichung City, 40201, Taiwan R.O.C.
Affiliations
Department of Nursing, Chung-Shan Medical University, Chung-Shan Medical University Hospital, Taiwan
Hemiparesis in stroke survivors has been reported to affect respiratory function. The relationship between trunk control and respiratory function, however, is not well understood. We aimed to map the state of the association between the trunk and respiratory function as well as evaluate the effect of a respiratory function training intervention on trunk control for stroke survivors.
Methods
A scoping review and meta-analysis of observational and interventional studies were performed. Cochrane Library, CINAHL with Full Text (EBSCO), Medline (Ovid), and PubMed were searched using the terms stroke, respiratory, and trunk control. The Preferred Reporting Items for Systematic Reviews and Meta-Analyses Extension for Scoping Reviews (PRISMA-ScR) checklist was used to examine the sections of each report.
Results
A total of 102 studies were identified, of which 12, published between 2011 and 2022, were included in the meta-analysis or narrative synthesis. Three studies were included in the meta-analysis of the correlation between trunk control and respiratory function parameters (forced vital capacity [FVC], forced expiratory volume during the first breath [FEV1], maximal inspiratory pressure [MIP], and maximal expiratory pressure [MEP]) with effect sizes (Fisher's z) for all outcomes, which ranged from small to intermediate (between 0.21 and 0.39). Furthermore, five studies were included in the meta-analysis of the effect of respiratory function training intervention on trunk control. An overall effect size (Cohen's d) of 1.47 corresponds to a large effect. We also found significant improvements in MIP and MEP but not in FVC and FEV1 for stroke survivors with the interventions.
Conclusions
Respiratory training, use of diaphragmatic resistance exercise or abdominal breathing, use of a pressure threshold-loading device, and the performance of functional strengthening exercises for the trunk muscles were found to increase patients’ trunk control and improve their respiratory muscle strength.
]. Hemispheric ischemic stroke has been reported to affect respiratory function to some extent due to reduced chest wall and diaphragmatic excursions contralateral to the stroke [
] reported that the mechanical limitation of thoracic excursion caused by weakness, hypotonicity, and incoordination of the trunk musculature creates a restrictive respiratory syndrome. In a systematic review and meta-analysis, Pozuelo-Carrascosa et al. [
Effectiveness of respiratory muscle training for pulmonary function and walking ability in patients with stroke: a systematic review with meta-analysis.
] found that respiratory muscle training improved respiratory function and walking ability in patients with stroke. However, they did not evaluate the relationship between respiratory function and trunk impairment or trunk control.
Another systematic review indicated that although diverse aspects of the clinical progression in stroke ambulation capacity or trunk stability are directly related to respiratory function, respiratory training programs fail to include ambulation and trunk stability [
] noted that inspiratory muscle strength is associated with functional mobility in patients with stroke. These results suggest that attention must be paid to trunk injury and respiratory function in patients with stroke.
From a nursing perspective, because of the inability to balance their bodies, in the ward, patients are often seen to be reclining when lying in bed or sitting up. Furthermore, the imbalance may result in an unsteady gait and falls [
] reported that nurses’ participation in poststroke patient rehabilitation is limited. Clarke further recommended that stroke-specific rehabilitation skills should be integrated into the nursing practice, which will help improve outcomes in stroke survivors. Similarly, Meng et al. [
] suggested that participation of nurses is important for the rehabilitation of patients with stroke. In addition to receiving physical therapy from a rehabilitation therapist, patients with stroke should receive relevant care from the nurses in the ward, to improve trunk control and postural stability. A preliminary understanding of the relationship between trunk damage and respiratory function may help nurses design their nursing tasks to promote trunk stabilization in patients with stroke. Therefore, we conducted a scoping review [
] to clarify the relationship between trunk control and respiratory function. A scoping review helps with the mapping of the body of literature regarding the relationship between trunk control and respiratory function and can also facilitate the presentation of an overview of a potentially large and diverse body of literature pertaining to a broad topic. Therefore, the articles found were not limited to randomized controlled trials (RCTs) or required the best available evidence [
The present study aimed to systematically map the evidence on the relationship between trunk control and respiratory function as well as determine the effect of respiratory muscle training on trunk control for stroke survivors. The specific research questions were as follows: (1) What is the association between trunk control and respiratory function? (2) What is the effect of the respiratory function training on trunk control?'
Study design
This study, which was designed as a scoping review and meta-analysis, was conducted and reported as per the guidelines formulated by the Joanna Briggs Institute (JBI) Manual for Scoping Reviews [
Chapter 10: analysing data and undertaking meta-analyses.
in: Higgins J.P.T. Thomas J. Chandler J. Cumpston M. Li T. Page M.J. Cochrane Handbook for systematic reviews of interventions version 6.3 (updated February 2022). 2022
]. The Preferred Reporting Items for Systematic reviews and Meta-Analyses Extension for Scoping Reviews (PRISMA-ScR) checklist was also used to guide the reporting of each section of this report [
]. The project was preregistered on the Open Science Framework (OSF) (https://osf.io/7nup6) before the data extraction to provide transparency of the process and limit the occurrence of reporting bias [
], was utilized. First, the first researcher (Hsiang-Chu Pai) conducted an initial limited search in Medline (Ovid) and CINAHL databases between April and May 2022 using the following terms: stroke AND respiratory AND trunk. From this initial search, key studies were identified and screened for other relevant search terms by title, abstract, and keywords. We also used an automation tool (Word Frequency Analyzer, https://sr-accelerator.com/#/wordfreq) to identify the relevant research terms [
]. Second, following an iterative process, authors (Hsiang-Chu Pai and Chia-Chi Li) finalized the search, using the following terms: (stroke or cerebrovascular accident or CVA or cerebral vascular event or CVE or transient ischemic attack or TIA) AND (lung function or lung function test or pulmonary function or pulmonary function test or respiratory function or respiratory function test) AND (trunk control or postural control or core stability or trunk stability or Trunk Impairment Scale or trunk balance or trunk). In addition, all observational studies (e.g., correlational, cohort, case control, and cross-sectional studies) or those using experimental study design, related to respiratory function and trunk impairment or trunk control, were included. The search of the index terms were then undertaken across four major databases (Cochrane Library, CINAHL with Full Text (EBSCO), Medline (Ovid), and PubMed) from January 1990 (or inception) to May 2022. Third, we identified additional studies through other resources, including Google Scholar, and checked the reference lists of all identified sources (Appendix 1).
Screening and data extraction
The selection criteria, set to identify the studies with considerable data on the relationship between respiratory function and trunk control in patients with stroke, included the following: (1) adult patients with stroke (hemorrhage or ischemic) and (2) outcome variables were respiration muscle function parameters (including forced expiratory volume during the first breath [FEV1] and forced vital capacity [FVC]), parameters of respiratory muscle strength (including maximal expiratory pressure [MEP] and maximal inspiratory pressure [MIP]), as well as other parameters related to pulmonary function and functional capacity, including trunk impairment, trunk stability, and trunk control. Exclusion criteria were (1) clinical trial protocols that did not include the results and (2) any study topic that did not meet the inclusion criteria.
In a total of 102 record studies, 35 duplicate studies were removed, and the remaining 67 studies were then entered into a two-stage screening process (title/abstract and full-text). All the study selection was performed by authors (OOO and OOO). Finally, we identified 12 studies that met our review objectives and all inclusion criteria (Figure 1).
Figure 1Selection Process for Inclusion of Studies in the Scoping Review and Meta-Analysis.
]. However, we used the 8-item Joanna Briggs Institute (JBI) critical appraisal tool/for analytical cross-sectional studies to assess the quality of four studies [
A meta-analysis was conducted to examine the correlation between trunk control and respiratory function. Data synthesis was also performed when the study reported on the effects of breathing training on trunk control.
All the effect sizes (ES), Fisher's z, and Cohen's d were calculated. Before combining the findings, a fixed or random model was developed, based on the heterogeneity test. The I-squared (I2) statistic and the Cochran chi-squared (Cochran Q) test were used to examine heterogeneity. As a guide, if the I2 value was 75% to 100%, it indicated considerable heterogeneity, calling for the use of random-effects estimation. In addition, a p-value of .10 (rather than .05) was used to determine statistically significant heterogeneity in the Cochran chi-squared test [
Chapter 10: analysing data and undertaking meta-analyses.
in: Higgins J.P.T. Thomas J. Chandler J. Cumpston M. Li T. Page M.J. Cochrane Handbook for systematic reviews of interventions version 6.3 (updated February 2022). 2022
]. All data arrangement for the meta-analysis was performed using the Review Manager (RevMan; The Cochrane Collaboration) software, version 5.4.
Ethical consideration
This scoping review and meta-analysis included only summary data or statistics from previously published studies; therefore, this study did not require a review or an approval by an institutional review board (IRB).
] and the inclusion criteria listed above, a total of 12 studies were identified. Four of the 12 studies were observational (Table 1), and the other eight were interventional (Table 2). All 12 studies were published between 2011 and 2022. The mean age of the participants reported in these studies ranged from 55.20 to 56.30 years. The geographic and ethnic representation of these studies included South Korea (k = 7), Brazil (k = 2), Spain (k = 1), China (k = 1), and Turkey (k = 1). Fewer studies from Western settings were found in this scoping review.
Table 1Summary Characteristics and Findings of the Studies that Assessed the Association Between Respiratory Function and Trunk Control for Stroke Survivors.
Mean time since stroke was 36.60 (SD = 23.90) months 21 stroke patients: 9 women, 12 men; mean age = 58.90 (SD = 13.50) years
Observational
TIS MIP MEP FVC FEV1 PEF TIFF
Trunk control had a significant positive correlation with PEF (r = .489, p = .024) and MEP (r = .517, p = .016). No relation was found between FVC, FEV1, TIFF, MIP, and TIS (r = .38, .34, .39, .43, p > .5).
Mean time since stroke was 14.90 (SD = 26.30) days 44 stroke patients: 25 women, 19 men; mean age = 59.40 (SD = 12.20)
Cross-sectional
TIS MIP MEP FVC FEV1 TIFF FEV1/FVC FIM
Trunk control had a significant positive correlation with MIP, FVC, FEV1, and FIM (r = .26, .28, .29, .77, p < .05) Mean of MEP was 36.1 (SD = 18.6), and TIS was 14.4 (SD = 5.8).
Mean time since stroke was 68.83 (15–167) days 52 stroke patients: 34 men, 18 women; mean age 57.46 (range from 29 to 84) years
Observational
TIS MIP MEP FEV1 FVC PCF
PCF, FVC, and FEV1 were significantly correlated with poststroke trunk balance (r = .65, p < .001, .45: p < .001, 0.32: p = .026). MIP and MEP, however, were not significantly correlated with poststroke trunk balance (r = .01, p = .96, .17; p = .239).
Mean time since stroke was 64.83 (SD = 45.62) days 71 stroke patients: 46 men, 25 women; mean age 58.72 (SD = 13.96)
Observational, longitudinal follow-up study
TIS MIP MEP FEV1 FVC FEV1/FVC VO2max.
MIP, MEP, FVC, FEV1, and FEV1/FVC were not associated with maximum oxygen consumption (VO2max). VO2max was significantly associated with the post-stroke Trunk Impairment Scale (β = 0.31, p = .006).
Table 2Summary Characteristics and Findings of the Studies that Assessed the Efficacy of Respiratory Interventions on Trunk Control for Stroke Survivors.
Mean time (months) since stroke was TG = 4.70 (SD = 1.69); CG = 3.95 (SD = 1.63) 40 stroke patients: TG = 20, mean age 55.50 (SD = 11.43) years; CG = 20 mean age = 58.30 (SD = 11.10) years Randomized-controlled study
Intervention: Chest resistance exercise group (CREG). Control: Chest expansion exercise group (CEEG). Time: 30 min a day, 5 times a week, for 8 weeks.
TIS FVC FEV1
Post-intervention TIS mean score: TG = 14.13 (SD = 0.92); CG = 12.07 (SD = 1.17) Both groups were effective in improving respiratory function and trunk control ability.
Mean time (months) since stroke: N/A 24 stroke patients: TG = 12, mean age 61.7 (SD = 6.20) years; CG = 12, mean age = 59.20 (SD = 4.60) years Randomized-controlled study
Intervention: Neurodevelopmental treatment + respiratory exercise using respiratory exercise equipment Control: Neurodevelopmental treatment Time: 30 min a day, 5 times a week, for 4 weeks.
TIS FVC FEV1
Post-intervention TIS mean score: TG = 16.60 (SD = 1.10); CG = 12.80 (SD = 0.80) The respiratory exercise using respiratory exercise equipment was effective in improving trunk control and pulmonary function.
Mean time (months) since stroke: N/A 16 stroke patients: TG = 8, mean age = 58 (SD = 12.90) years; CG = 8, mean age 56 (SD = 9.20) years Randomized, double-blind, controlled clinical trial
Intervention: IMT program + progressive intensity Control: IMT program Time: 5 days a week, once a day, for 8 weeks
Trunk control test (TCT) FVC FEV1 PEF VMV PImax
Post-intervention TCT mean score: TG = 77.50 (SD = 32.70); CG = 84.20 (SD = 12.60) IMT, although low intensity, is effective in improving inspiratory muscle strength; however, the effects on postural control and balance remain uncertain.
Comparative effect of Liuzijue qigong and conventional respiratory training on trunk control ability and respiratory muscle function in patients at an early recovery stage from stroke: a randomized controlled trial.
Effects of inspiratory muscle training on respiratory muscle strength, trunk control, balance and functional capacity in stroke patients: a single-blinded randomized controlled study.
Mean time (months) since stroke was TG = 14.27 (8.37); CG = 20.20 (15.36) 21 stroke patients: TG = 11, mean age = 61.72 (SD = 10.77) years; CG = 10, mean age = 66.10 (SD = 8.87) years Single-blinded randomized-controlled study
Intervention: Neurodevelopmental BOBATH Treatment (NDT) + IMT Control: Neurodevelopmental BOBATH treatment approach (NDT) Time: 30 min a day, 5 days a week, for 6 weeks
TIS MIP MEP Timed Up and Go Test (TUG) BBS Six-Minute Walk Test (6MWT)
Post-intervention, there was a significant difference in the change in TIS between groups (p = .006). IMT improved inspiratory muscle strength and trunk control.
The mean time (months) since stroke was TG = 11.15 (2.38); CG = 11.00 (2.17) 25 stroke patients: TG = 13, mean age = 58.62 (SD = 12.38) years; CG = 1, mean age = 59.75 (SD = 13.38) years Randomized-controlled trial
Intervention: Respiratory muscle training with trunk stabilization exercise group Control: Trunk stabilization Time: 40 min a day, 3 times a week, for 6 weeks.
Trunk stability was significantly increased in the intervention group. In the intervention group, respiratory muscle thickness was significantly increased.
The effects of dynamic core-postural chain stabilization on respiratory function, fatigue and activities of daily living in subacute stroke patients: a randomized control trial.
The mean time (weeks) since stroke was TG = 7.43 (2.25); CG = 7.00 (2.23) 31 stroke patients: TG = 16, mean age = 62.93 (SD = 12.19) years; CG = 15, mean age = 58.06 (SD = 16.44) years Randomized-controlled trial
Intervention: Dynamic core-postural chain stabilization (DCS) Control: Neurodevelopmental treatment (NDT) Time: 30 min each session, 3 times a week, for 4 weeks.
FVC FEV1 MIP MEP.
DCS is effective in improving core stability, postural control, and respiratory function via increased diaphragm movement.
The effects of the neck stabilization exercise on the muscle activity of trunk respiratory muscles and maximum voluntary ventilation of chronic stroke patients.
The mean time (months) since stroke was TG = 17.33 (7.13); CG = 20.33 (8.52) 30 stroke patients: TG = 15, mean age = 66.20 (SD = 11.07) years; CG = 15, mean age = 69.67 (SD = 9.74) years Randomized-controlled trial
Intervention: Neck stabilization exercise + breathing retraining exercise Control: Breathing retraining exercise Time: 30 min a day, 5 times a week, for 6 weeks.
Maximal voluntary ventilation (MVV)
The intervention group showed significantly larger change in the activity of the trunk's respiratory muscles and MVV.
Note. BBS = Berg Balance Scale, CG = control group, FEV1 = forced expiratory volume in the first second, FVC = forced vital capacity, IMT = inspiratory muscle training, IQR = interquartile range, MEP = maximum expiratory pressure, MIP = maximum inspiratory pressure, PEF = peak expiratory flow, SD = standard deviation, TG = treatment group, TIS = Trunk Impairment Scale.
] did not describe whether there were confounding factors or discuss whether confounding factors affected the results. Their risks of bias scores were 5 and 6, respectively, which indicated a moderate risk of bias [
Comparative effect of Liuzijue qigong and conventional respiratory training on trunk control ability and respiratory muscle function in patients at an early recovery stage from stroke: a randomized controlled trial.
], both those who provided the treatment and the participants were blinded. Although another study stated that it was single-blind, the text only reads “All the evaluations and trainings were performed by separate …, ” and it was impossible to confirm whether the therapist or the evaluator was blinded [
Effects of inspiratory muscle training on respiratory muscle strength, trunk control, balance and functional capacity in stroke patients: a single-blinded randomized controlled study.
The effects of dynamic core-postural chain stabilization on respiratory function, fatigue and activities of daily living in subacute stroke patients: a randomized control trial.
The effects of the neck stabilization exercise on the muscle activity of trunk respiratory muscles and maximum voluntary ventilation of chronic stroke patients.
] did not clearly state whether the participants, assessors, or those providing treatment, were blinded. The results of the quality assessment are presented in a supplementary document (Appendix 3).
Correlations across different respiratory function indices and trunk control
Four studies examined the relationship between trunk control and respiratory function (Table 2). Participants in three studies were in the presubacute stage—the mean time since stroke ranged from 14.90 to 64.83 days [
] to measure the patients’ trunk control ability. In addition, four indices, two each of respiratory muscle function (FVC, FEV1) and respiratory muscle strength (MIP, MEP), were included in the assessments in all four studies. Lee et al. [
], however, did not perform a correlation analysis of TIS with respiratory muscle function (FVC, FEV1) or strength (MIP, MEP) but presented the predictive value of TIS on VO2max. Thus, in the present study, three studies were included in the meta-analysis [
Of the three studies included, the total number of participants included in the meta-analysis was 117. The sample size of studies ranged from 21 to 52. As shown in Figure 2, there was a significant positive correlation between trunk control and FVC and FEV1; the pooled Fisher's z was 0.39 (95% confidence interval [CI] = 0.21, 0.58) and 0.32 (95% CI = 0.13, 0.51), with no significant heterogeneity (I2 = 0%). There was also a significant positive correlation between trunk control andMIP1; the pooled Fisher's z was 0.21 (95% CI = 0.02, 0.40), with no significant heterogeneity (I2 = 49.0%). The pooled Fisher's z between trunk control and MEP was 0.52 (95% CI = 0.17, 0.87) with significant heterogeneity (I2 = 79.0%).
Figure 2Forest Plots of Cohen's Values with 95% CIs for the Correlation between TIS and FVC (A), FEV1 (B), MIP (C), and MEP (D). Notes. FEV1 = forced expiratory volume in one second; FVC = force vital capacity; MEP = maximal expiratory pressure; MIP = maximal inspiratory pressure; TIS = Trunk Impairment Scale.
Comparative effect of Liuzijue qigong and conventional respiratory training on trunk control ability and respiratory muscle function in patients at an early recovery stage from stroke: a randomized controlled trial.
Effects of inspiratory muscle training on respiratory muscle strength, trunk control, balance and functional capacity in stroke patients: a single-blinded randomized controlled study.
The effects of dynamic core-postural chain stabilization on respiratory function, fatigue and activities of daily living in subacute stroke patients: a randomized control trial.
], together with respiratory muscle function (FVC, FEV1) and respiratory muscle strength (MIP, MEP). Therefore, we conducted a meta-analysis for these outcome variables separately. Another interventional study [
The effects of the neck stabilization exercise on the muscle activity of trunk respiratory muscles and maximum voluntary ventilation of chronic stroke patients.
], which also focused on trunk control, was not included in the meta-analysis because it used different respiratory function assessment tools (maximal voluntary ventilation [MVV]), so we additionally performed a narrative synthesis. The length of the interventions ranged from 3 to 8 weeks. Most participants were in the subacute stage of stroke recovery, about 1 week to several months after the stroke.
Four of the 8 studies used TIS as a measurement tool and as a trunk control variable [
Comparative effect of Liuzijue qigong and conventional respiratory training on trunk control ability and respiratory muscle function in patients at an early recovery stage from stroke: a randomized controlled trial.
Effects of inspiratory muscle training on respiratory muscle strength, trunk control, balance and functional capacity in stroke patients: a single-blinded randomized controlled study.
] used the trunk control test (TCT) measure as the trunk control variable. We calculated the results of these five studies as effect size (Cohen's d) and performed the meta-analysis. The total number of participants included in the analysis was 81 in the experimental group and 80 in the control group. The meta-analysis revealed an overall effect size (Cohen's d) of 1.47 (95% CI: 0.46–2.48; I2 = 86.0%, p = .004), corresponding to a large effect, significantly different from 0 (Figure 3a).
Figure 3Forest Plots of Cohen's d Values with 95%CIs for the Effect of Respiratory Function Training on Trunk Control (a), FVC (b), FEV1 (c), MIP (d), and MEP (e). Notes. FEV1 = forced expiratory volume in one second; FVC = force vital capacity; MEP = maximal expiratory pressure; MIP = maximal inspiratory pressure.
We also examined the effect of respiratory function training on pulmonary function (FVC, FEV1) and pulmonary strength (MIP, MEP). As some studies used different units of the parameters (e.g., %, liter, cmH2O), we converted these results to effect size (Cohen's d). The FVC was analyzed in six studies [
Comparative effect of Liuzijue qigong and conventional respiratory training on trunk control ability and respiratory muscle function in patients at an early recovery stage from stroke: a randomized controlled trial.
], and the total number of participants included in the analysis was 97 in the experimental group and 95 in the control group. The pool effect size (Cohen's d) was 0.39 (95% CI: −0.30 to 1.09; I2 = 80.0%, p = .27) (Figure 3b). The analysis did not show significant differences between the ES of the groups in regard to FVC. In addition, FEV1 was analyzed in seven studies [
Comparative effect of Liuzijue qigong and conventional respiratory training on trunk control ability and respiratory muscle function in patients at an early recovery stage from stroke: a randomized controlled trial.
Effects of inspiratory muscle training on respiratory muscle strength, trunk control, balance and functional capacity in stroke patients: a single-blinded randomized controlled study.
The effects of dynamic core-postural chain stabilization on respiratory function, fatigue and activities of daily living in subacute stroke patients: a randomized control trial.
], with a total number of participants of 110 in the experimental group and 107 in the control group. The pooled effect size (Cohen's d) was 0.27 (95% CI: −0.00 to 0.54; I2 = 58.0%, p = .05) (Figure 3c). The analysis again did not show significant differences between the ES of the groups in regard to FEV1.
Other respiratory muscle strength parameters (MIP, MEP) were analyzed in four studies [
Comparative effect of Liuzijue qigong and conventional respiratory training on trunk control ability and respiratory muscle function in patients at an early recovery stage from stroke: a randomized controlled trial.
], and the total number of participants included in the analysis was 70 in the experimental group and 67 in the control group. The pooled estimated ES on MIP was 0.54 (95% CI: 0.20 to 0.88; I2 = 0%, p = .002), and the pooled estimated ES on MEP was 0.63 (95% CI: 0.28 to 0.97; I2 = 0%, p < .001). These findings show statistically significant improvement in the intervention group on MIP and MEP.
Finally, only one study reported on the performing neck stabilization exercises with breathing retraining and evaluation of the MVV [
The effects of the neck stabilization exercise on the muscle activity of trunk respiratory muscles and maximum voluntary ventilation of chronic stroke patients.
]. This study found that the corresponding intervention can increase trunk stability while improving postural control and activity of the trunk's respiratory muscles in stroke patients.
Discussion
We conducted a scoping review to map the body of literature on the relationship between trunk control and respiratory function, and the included studies were observational or RCTs in design. For eligible studies, study appraisal and meta-analysis were performed. However, one study data could not be integrated into the analysis; therefore, it was reported in the discussions as a narrative synthesis. Overall, the results of the present study show a significant positive relationship of trunk control with respiratory muscle function (FVC, FEV1) and respiratory muscle strength (MIP and MEP). We also found significant effects of specific respiratory function training on trunk control, MIP, and MEP but not on FVC and FEV1.
A previously published study summarizes the evidence in regard to respiratory impairments in major neurological diseases and reports that trunk motor control impairment shows an association with pulmonary function in stroke survivors [
] and focused on the search strategies for trunk control and respiratory function. We included three studies with a total of 117 stroke patients, and we performed a meta-analysis based on different lung function indices. Our results show that patients who have better trunk control present better FVC, FEV1, MIP, and MEP. All three indicators, FVC, FEV1, and MEP are related to the expiratory function or expiratory muscle. Our results appear consistent with a previous report, which indicated that trunk paresis can lead to postural dysfunction, which promotes a decrease in the activation of the abdominal muscles and leads to a decrease in the values of the maximum pulmonary pressures related to respiration. Thus, these changes promote a decrease in expiratory pressure and FEV [
] report that MIP is an indicator of inspiratory muscle strength, determined by having the subject expire to a residual volume and then perform a maximum inspiratory maneuver. Clearly, that MIP is indirectly related to the amount of exhalation and explains the correlation between trunk control and MIP. Our findings also confirm those of Lee et al. [
], who indicated that VO2max, which reflects cardiopulmonary function, is significantly associated with poststroke trunk control. These findings suggest that the stability of the trunk in stroke patients is related to their respiratory function and respiratory muscle strength. Therefore, we suggest that nurses should be able to assess the extent of trunk damage in a timely manner to promote the care of stroke patients. They should also pay more attention to the assessment and care of the respiratory function of such patients.
Regarding the effects of specific respiratory function training on trunk control, our results showed the effectiveness of respiratory interventions to improve trunk control in patients with stroke. It is worth noting that we found that the interventions in the studies were diverse and included inspiratory muscle training (IMT) [
Effects of inspiratory muscle training on respiratory muscle strength, trunk control, balance and functional capacity in stroke patients: a single-blinded randomized controlled study.
Comparative effect of Liuzijue qigong and conventional respiratory training on trunk control ability and respiratory muscle function in patients at an early recovery stage from stroke: a randomized controlled trial.
]. These studies, however, use trunk control as the outcome variable. In addition, common to these interventions is that breathing training involves (a) the use of diaphragmatic resistance exercise or abdominal breathing; (b) the use of a pressure threshold-loading device; and (c) the performance of functional strengthening exercises for the trunk muscles. It is important to promote stroke survivors' respiratory function, by stretching the latissimus dorsi muscle and using the functional strengthening exercises for the trunk muscles [
Effects of inspiratory muscle training on respiratory muscle strength, trunk control, balance and functional capacity in stroke patients: a single-blinded randomized controlled study.
]. These results also echo our findings in regard to three other studies that show that respiratory muscle training with trunk stabilization exercises [
The effects of dynamic core-postural chain stabilization on respiratory function, fatigue and activities of daily living in subacute stroke patients: a randomized control trial.
The effects of the neck stabilization exercise on the muscle activity of trunk respiratory muscles and maximum voluntary ventilation of chronic stroke patients.
], while improving postural control and the activity of the trunk's respiratory muscles in stroke patients. These findings are also in keeping with the findings of Hodges and Gandevia [
], indicating that the diaphragm, which is a primary inspiratory muscle, is also among the trunk stabilizer muscles. This also illustrates the importance of abdominal or diaphragmatic breathing in stabilizing the trunk and promoting respiratory function in stroke patients.
We found that these interventions resulted in significant improvements in MIP and MEP. However, the interventions in the experimental groups were not better than those in the control groups in improving FVC and FEV1. This may be related to the duration of the intervention because the intervention period for the eight studies included in this study was between 3 and 8 weeks [
Comparative effect of Liuzijue qigong and conventional respiratory training on trunk control ability and respiratory muscle function in patients at an early recovery stage from stroke: a randomized controlled trial.
Effects of inspiratory muscle training on respiratory muscle strength, trunk control, balance and functional capacity in stroke patients: a single-blinded randomized controlled study.
The effects of dynamic core-postural chain stabilization on respiratory function, fatigue and activities of daily living in subacute stroke patients: a randomized control trial.
The effects of the neck stabilization exercise on the muscle activity of trunk respiratory muscles and maximum voluntary ventilation of chronic stroke patients.
]. This finding shows that the promotion effect of intervention on MIP and MEP can be seen within this short period; however, the effects of FVC and FEV1 may require longer intervention time. This also indicates that the combined effect of improving respiratory function and trunk control in stroke patients requires further research. However, it is worth noting that nurses can provide bedside care in clinical settings to assist the stroke survivors in stabilizing their trunks, including abdominal breathing training, guidance on sitting posture stability, and the correct posture when lying in bed. These will promote the stability of the trunk and improve the respiratory function.
Limitations
Because the number of relevant studies and the number of participants were small, we recommend that more studies focusing on interventional trunk control be analyzed in future. We also suggest that increasing the number of participants can strengthen the findings. In addition, due to the small number of studies, we could not conduct a meta-analysis of subgroups (e.g., age, gender, hemiplegic limbs). Therefore, we also suggest that future research select samples based on patients of different ages or different hemiplegic limbs, which will be able to provide more specific clinical care applications.
Conclusion
Our study was the first to map the positive relationship between trunk control and respiratory function in stroke patients. We also found that respiratory function training combined with abdominal movement of the diaphragm can improve trunk control and further strengthen the patient's MIP and MEP. Our research extends the findings of Pozuelo-Carrascosa et al. [
Effectiveness of respiratory muscle training for pulmonary function and walking ability in patients with stroke: a systematic review with meta-analysis.
], who found that respiratory muscle training can promote stroke survivors' respiratory function. However, their study did not focus on the relationship between respiratory function and trunk impairment or trunk control. Our findings provide further insight into the positive relationship between trunk control and respiratory function.
Conflict of interest
The authors declare no conflicts of interest in this study.
Appendix A. Supplementary data
The following are the supplementary data to this article.
Effectiveness of respiratory muscle training for pulmonary function and walking ability in patients with stroke: a systematic review with meta-analysis.
Chapter 10: analysing data and undertaking meta-analyses.
in: Higgins J.P.T. Thomas J. Chandler J. Cumpston M. Li T. Page M.J. Cochrane Handbook for systematic reviews of interventions version 6.3 (updated February 2022). 2022 (Available from)
Comparative effect of Liuzijue qigong and conventional respiratory training on trunk control ability and respiratory muscle function in patients at an early recovery stage from stroke: a randomized controlled trial.
Effects of inspiratory muscle training on respiratory muscle strength, trunk control, balance and functional capacity in stroke patients: a single-blinded randomized controlled study.
The effects of dynamic core-postural chain stabilization on respiratory function, fatigue and activities of daily living in subacute stroke patients: a randomized control trial.
The effects of the neck stabilization exercise on the muscle activity of trunk respiratory muscles and maximum voluntary ventilation of chronic stroke patients.
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