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Abdominal binder improves lung volumes and voice in people with tetraplegic spinal cord injury.
To investigate the effect of an elasticated abdominal binder on respiratory, voice, and blood pressure outcomes for people with a motor complete acute tetraplegia during the first year after injury.
Randomized crossover study.
Large university-affiliated referral hospital.
Consenting participants (N=14, 13 men and 1 woman) with recent, motor complete, C3-T1 spinal cord injury.
Abdominal binder on/off with participant seated in upright wheelchair, with 3 repeated measures at 6 weeks, 3 months, and 6 months after commencing daily use of an upright wheelchair.
Main Outcome Measures
Forced vital capacity, forced expiratory volume in 1 second, peak expiratory flow, maximal inspiratory pressure, and maximal expiratory pressure were measured. Mean arterial pressure, maximum sustained vowel time, and sound pressure level were also measured.
Overall, an abdominal binder resulted in a statistically significant improvement in forced vital capacity (weighted mean difference .34L [95% confidence interval (CI) .10–.58], P=.005), forced expiratory volume in 1 second (.25L [95% CI −.01 to .51], P=.05), peak expiratory flow (.81L/s [95% CI .13–1.48], P=.02), maximal inspiratory pressure (7.40cmH2O [95% CI 1.64–13.14], P=.01), and maximum sustained vowel time (3.75s [95% CI .90–6.60], P=.01). There was no statistically significant improvement in maximal expiratory pressure (5.37cmH2O [95% CI −1.15 to 11.90], P=.11), mean arterial pressure (4.41mmHg [95% CI −6.15 to 14.97], P=.41), or sound pressure level (1.14dB [95% CI −1.31 to 3.58], P=.36).
An individually fitted abdominal binder significantly improved forced vital capacity, forced expiratory volume in 1 second, peak expiratory flow, maximal inspiratory pressure, and maximum sustained vowel time in people with newly acquired tetraplegia. Further study is needed into the effect of the long-term use of the abdominal binder on breathing mechanics, functional residual capacity, total lung capacity, and respiratory health.
IN 2007 TO 2008, THERE WERE 362 new cases of spinal cord injury (SCI) admitted across the 6 speciality spinal injuries units within Australia. Cervical spine injuries accounted for 53% of all those admitted, with 32% affecting the thoracic spine.
This compromised respiratory function is caused by denervation of intercostal muscles, which limits inspiratory and expiratory ability, and loss of abdominal muscle function, which prevents an effective cough.
by our group concluded that there was some evidence that the use of an abdominal binder (AB) significantly improves vital capacity and significantly decreases functional residual capacity. This review found that an AB resulted in a trend toward an overall decrease in total lung capacity and had no significant effect on maximum inspiratory pressure (MIP), but the review found conflicting results for the effect of an AB on maximum expiratory pressure (MEP). There were methodologic limitations associated with the studies in this review.
The imbalance between sympathetic and parasympathetic neural control after SCI results in hypotension and bradycardia for many patients.
Clinically, most rehabilitation centers recommend the use of an AB when first starting to use a wheelchair for those patients with tetraplegia and high paraplegia with the aim of reducing OH. The impact of an AB on breathing and voice is often a secondary consideration. No previous study has examined the effect of an AB on the main clinical indicators for the use of an AB, and in the same subject group from the acute rehabilitation phase. This randomized crossover trial aimed to determine the short-term effect of an AB on respiratory function, voice, and hemodynamics in people with acute tetraplegia and high paraplegia during the first 6 months of using an upright wheelchair.
This study was conducted in a spinal injuries unit for adults between January 2008 and October 2009. Ethical clearance was provided through the local human research ethics committee. Patients admitted to the spinal injuries unit meeting study inclusion criteria were provided with a study information sheet and approached for consent by the principal investigator. Participants were included if they had an acute traumatic SCI with an American Spinal Injuries Association Impairment Scale of A or B (motor complete) above the T5 level, were aged between 18 and 80 years, and were English speaking. Potential participants were excluded if they had skin breakdown across their sitting surface or across the region of AB application, a traumatic brain injury, and/or active respiratory disease (chronic obstructive airways disease, asthma, lung pathology) at the time of the study. All participants approached for consent were included.
The portable SpiroPro Spirometera was used to measure peak expiratory flow (PEF), forced expiratory volume in 1 second (FEV1), and forced vital capacity (FVC). Respiratory function tests were conducted according to the guidelines of the American Thoracic Society/European Respiratory Society
Participants who satisfied spirometry acceptability but not repeatability criteria had values recorded from their best acceptable curve selected for analysis. Up to 8 attempts were made in an effort to achieve repeatability. Participant ability to meet spirometry criteria was noted. Predictive values for FEV1, FVC, and PEF were calculated using reference values supplied with the SpiroPro.
Respiratory muscle strength was assessed by measuring MIP and MEP using the MicroRPM handheld respiratory pressure metera with a tube-style mouthpiece. Participants were instructed to make maximum inspiratory and expiratory efforts at residual volume and total lung capacity, respectively, according to American Thoracic Society/European Respiratory Society guidelines.
The highest value measured within 10% of 3 previous recordings was taken, ensuring a rest time of 1 minute between tests. Up to 8 repeated measures were recorded. A nose clip was used for all respiratory measurements, and data collection was carried out at the same time of the day for all participants.
Respiratory support for voice was indirectly investigated through measuring maximum sustained vowel (MSV) time and mean sound pressure level (SPL) (acoustic measure of vocal loudness) during sentence recitation. MSV was measured as the maximum length of time a participant could sustain the sound “ah” with even pitch after a large inhalation. SPL was recorded while participants recited the sentence “Combine all the ingredients in a large bowl” at maximal SPL with mean SPL across the sentence measured.
Standard instructions and a demonstration were provided to each participant. MSV and SPL were repeated 3 times each. The longest MSV recorded and the highest SPL samples were used. Recordings were collected using an Edirol sound recorder and a headset microphone.b The midpoint of the microphone of the Edirol was positioned 5 centimeters away and directly in front of each participant's mouth. Voice samples were recorded as digital .wav files at a sampling rate of 44.1 kilohertz with 16-bit quantization. Participants completed the testing with their arms resting comfortably on their laps, and all testing was completed in a quiet office with minimal noise disturbance. Data were analyzed using the TF32 time-frequency analysis software programc for MSV and the CSL program for SPL.d
Blood pressure measurements were taken using the arm cuff automatic blood pressure monitor Omron IA2e as per manufacturer's instructions with and without the AB in place with the participant in the seated wheelchair position and also while supine after quiet rest of 5 minutes. Mean arterial pressure (MAP) was calculated from the blood pressure measures on the basis of the following formula:
after 2 measurements with 2 minutes of rest between each sample were obtained.
Abdominal Binder Design
The elasticated AB was made of polyester and 20% spandex.f This AB was available in several widths and lengths and was fitted to the individual so as to provide firm support around the abdomen from the anterior superior iliac crest to the costal margin of the rib cage (fig 1).
Each participant was assessed at 3 time points with and without the AB applied while sitting in the provided upright wheelchair at 6 weeks, 3 months, and 6 months after commencing daily wheelchair use. The order of the testing condition (with AB on or off) by individual and occasion of assessment (3 assessment time points) was randomized to control for an order effect. The assessor was not blinded to the application of the AB; however, analysis of the data was completed with the data coded such that AB status was unknown.
The AB was initially applied with the participant supine and at the end of expiration to ensure adequate compression of the soft tissue over the abdomen. A 10% reduction in seated girth measurement was the aim.
While the AB did encroach on the lower rib costal margins, it was fitted below rib 9. The participant was assisted into a posturally aligned and upright position in the wheelchair each time. Participants were given 5 minutes of quiet rest in sitting between each condition (AB off or on), with a minimum of 1 minute of rest between each assessment task to ensure less influence of fatigue. The same investigator collected all data across all time points.
Participants were questioned about the frequency of AB use after each testing, and any participant not wearing the AB daily was noted but continued with the study. They were questioned as to the reason the AB had been discarded, and this information was recorded.
A multilevel mixed effects linear regression model was used for analysis of data because there were missing data at all time points. A model effect of AB, assessment time point interaction between AB and assessment, time interaction between AB use and ceasing daily use, and effect of order within session were investigated. The order term was used in our multilevel mixed effects linear regression model to account for whether there was an influence on whether participants performed better on test 1 or test 2 within the same session. The AB was treated as a fixed effect, the participant as a random effect, and assessment time point as a random effect. Model specifications for each analysis were checked using the likelihood ratio test and by visually examining the normality of conditional residuals to determine whether transformation of the dependent variable was warranted. The level considered to be statistically significant was P less than .05. Stata/IC version 10.1g was used for statistical analysis.
All eligible, consecutive patients admitted were approached, and all consented to participate in the study (table 1). Thirteen of the 14 adults who participated were men. Participants had a mean age of 32±16 years, mean height of 179±7 centimeters, and mean weight of 73±11 kilograms. Two subjects were active smokers at the time of their injury. However, both subjects denied smoking during the study period.
Eleven participants completed data collection at all 3 time points (table 2). Not all subjects had MIP and MEP outcomes recorded because of issues gaining access to the MicroRPM and the late inclusion of the hemodynamic outcome. No participants withdrew from the study because of side effects or unwillingness to participate. Three participants were not able to complete the study because 2 participants were discharged home (not to the local area) and 1 elderly participant became unwell and was discharged to a local nursing home.
Table 2Individual Data at All 3 Assessment Time Points
Three participants ceased wearing an AB daily during the study but were still included (see table 1). The reasons given for ceasing to wear the AB were “I think the AB will stop my abdominals from working,” “the AB keeps riding up my ribs when I'm exercising,” and “I think my abs are working and don't want them stopped by the AB.” There was no significant effect for AB×time interaction, indicating that the effect of the AB was relatively consistent across all time points regardless of whether the participants ceased wearing the AB daily during the study (table 3).
Table 3Mean Results Over 3 Assessment Time Points Including Effect of AB, Effect of Assessment Time Point, AB Use Over Time Interaction, and the Order of Testing Effect
Overall, participants increased their values over time for FVC, FEV1, MIP, MEP, MSV, SPL, and MAP, with a near-significant trend for PEF regardless of the use of the AB (see table 3).
The majority of participants could perform acceptable spirometry according to American Thoracic Society/European Respiratory Society or modified-for-SCI criteria. However, 2 participants across all time points satisfied modified-for-SCI criteria for acceptability but not repeatability and therefore had values recorded from their best acceptable curve used in data analysis.
Table 3 indicates there were improvements in all pulmonary function measurements at each time point with the use of the AB compared with no AB. There was a statistically significant increase in mean FVC, FEV1, and PEF across the 3 time points when the AB was in place (Fig 2, Fig 3). Overall, FVC was .34 liters higher, FEV1 was .25 liters higher, and PEF was .81 liters/second higher with the AB, representing a greater than 10% improvement. MIP was significantly higher by 7.40 cmH2O with the AB, while MEP was higher with the AB but not to a significant level (fig 4). Mean results over the 3 time points showed a significant order of testing effect for FVC and MIP only. This means that overall the second FVC test was .10 liters less than the first test and the MIP test was 4 cmH2O less than the first test regardless of the application of the AB. While participants were given a minimum rest of 1 minute between each FVC and MIP effort and also given 5 minutes of rest between the application or removal of the AB, this may not have been long enough for some and therefore this order effect is likely due to fatigue of the respiratory muscles.
Mean MSV and SPL were greater at all time points with the AB. Overall, the AB provided statistically significant (P=.01) improvement in MSV by 3.75 seconds (fig 5). While an AB did improve SPL by 1.14 decibels, this was not significant (P=.36).
Mean MAP was greater with the AB at the first and third time point, while MAP was less with the AB at the second time point. It is unclear why this occurred. Overall, an AB did improve MAP by 4.41mmHg, but this was not statistically significant (P=.41) (fig 6). While measures of supine and seated blood pressure were taken, allowing diagnosis of OH, this was not a key outcome. Although when these data were reviewed, there were 7 occasions of OH found across subjects as indicated by systolic blood pressure changes. Of these, 4 had OH regardless of AB application and 3 had OH without the AB only. The time point that these episodes of OH occurred varied and was not more prevalent at the initial time point.
This study is the first to investigate the effect of an elasticated AB on short-term respiratory, hemodynamic, and voice parameters when used for people with acute tetraplegic SCI. While values improved over time regardless of AB use, improvements were noted with the AB at each time point. Consistent with previous respiratory findings, we found that the use of an AB resulted in significantly increased FVC.
Our study also found significantly increased MIP, which was not found in other studies. The reason for this is unclear because these studies also used an elastic AB but only 20% of combined subjects were within 1 year after injury.
found no significant difference with the AB for MEP, they did demonstrate a decrease in compliance of the abdomen with the AB when the participants were seated.
The decrease in abdominal compliance with the AB is thought to restore pressure transference across the thoracic and abdominal chambers. In the uninjured person, contraction of the abdominal muscles creates not only a forceful expiration but also greater positive pressure within the abdomen, forcing the diaphragm in a cephalad direction. The mechanism of the AB is thought to result from it creating a more stable abdomen to generate pressure through to the thorax and thus enhance inspiratory/expiratory muscle activation on the rib cage.
have been shown to aid in increased FVC and forced expiration, respectively. Whether an AB can provide further support to these interventions or have an effect on respiratory complications is an area for further study.
To the best of our knowledge, this study is the first to investigate the influence of an elasticated AB on respiratory support for voice in SCI. Overall, MSV time was found to be significantly improved by 13% with the use of the AB. With normal MSV values ranging from 15 to 30 seconds
found increased syllables per breath and overall listener preference in 3 participants with SCI, this was achieved using a nonelastic mechanical device with the participant in the seated position to achieve abdominal compression and is not appropriate outside of the research laboratory. In complete cervical SCIs, a decrease in inspiratory pressures and the resultant decrease in vital capacity may lead to short breath groups (fewer words per breath). This means that a person's speech has more frequent breaths and is more interrupted when the person is speaking in sentences. A decrease in expiratory pressure may result in a decrease in SPL.
While MEP and SPL were found to be improved with the AB, this was not to a statistically or clinically significant level. We found that only 3 participants were able to raise their voice to above 70 decibels regardless of AB and hence had quiet voices (normal range for vocal volume is 71–77dB).
Only 1 participant increased loudness by over 5 decibels with the AB, which may be considered clinically significant in this population. The minimum clinically important difference between outcomes was taken to be 10% to 15% improvement with the AB compared with no AB. In the absence of SCI-specific data, this value was taken from studies investigating lung volumes of patients suffering from chronic obstructive pulmonary disease.
Although one of the most commonly cited reasons for wearing an AB is prevention of OH, we did not find a significant effect on MAP in this study. While it is recognized that for a diagnosis of OH, specific criteria must be met, we only sought to investigate hemodynamic change indicated by MAP. While several participants did report increased dizziness without the AB (a symptom of OH) during the collection of respiratory data, their blood pressure was not measured at this time. Because the incidence of OH is highest in more acute SCI,
the incidence may have been lower in this current study with all participants tested after 6 weeks of mobilizing in their wheelchair. An improvement of 4mmHg in MAP in the very acute setting may be deemed clinically significant and may influence the use of inotropic support. Mean MAP of below 80mmHg was found at the first and third time points without the use of the AB. The optimal MAP for the maintenance of spinal cord perfusion is not known. However, acute management guidelines suggest that achieving a MAP of 85mmHg should be the target.
Therefore, the effect of an AB in acute SCI for the management of hemodynamic stability or OH has not yet been properly investigated and poses ethical questions given the clinical incidence of symptoms of OH observed in the first few weeks after suffering an SCI.
Our study is also the first to investigate the effect of an AB on the same participant over the first 6 months after commencing daily wheelchair use. Information related to ongoing use of the AB is important to help direct future use of such medical aids. While the material makeup and fit of ABs vary throughout spinal rehabilitation centers, the AB used in our spinal injuries unit had been chosen to most closely mimic abdominal muscle function, not inhibit movement of the wearer, and with reduced chance of skin irritation. Despite this, 3 subjects chose to cease wearing an AB even though they demonstrated improved measurable outcomes with the AB in place.
The relatively small sample size and the high degree of variability with some measures, as indicated by the SDs, were the primary limitations of this study. This variability may have been influenced by fatigue during the collection of respiratory outcomes. While this study allowed for rest times to reduce fatigue, and participants had initial spirometry completed on admission, not all participants retained this new skill in spirometry performance. The chance of meeting spirometry criteria would likely be improved by training participants in the correct technique the day before each data collection time point. This may decrease fatigue experienced with multiple attempts and multiple outcome measures during 1 session.
This study did not measure AB impact on total lung capacity and functional residual capacity. Whether the increase in lung volumes seen in this current study is more important than the decrease in functional residual capacity and total lung capacity with wearing AB observed in other studies is an area of continued debate and needs further investigation.
Measures of hemodynamic function by way of MAP may not have been the most sensitive outcome to assess OH, and this should be considered for future studies. MAP was not collected at each time point for all participants and hence resulted in missing data. The inclusion of MAP, MEP, and MIP after the study commenced meant that the sample size may have been too small to detect the difference. Lack of blinding of the assessor was also a limitation.
An individually fitted elasticated AB significantly improved FVC, FEV1, PEF, MIP, and MSV in 14 people with newly acquired tetraplegia. However, the continued use of an AB needs to be directed by the clinician taking into account the individual's breathing, voice, and blood pressure response to the AB. AB effect can be measured with simple and quick bedside measures using a spirometer, a stopwatch, and a sphygmomanometer. Further study is needed into the effect of the long-term use of the AB on total lung capacity, functional residual capacity, breathing mechanics, rate of pulmonary complications, and overall respiratory health. Further consideration is needed with regard to whether a person with SCI will continue to use an AB and its impact on comfort, skin integrity, and likely postural changes during the initial years after injury.
Supported by the Queensland Health Allied Health Research Scheme.
No commercial party having a direct financial interest in the results of the research supporting this article has or will confer a benefit on the authors or on any organization with which the authors are associated.