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Abdominal Binder Improves Lung Volumes and Voice in People With Tetraplegic Spinal Cord Injury

      Abstract

      Abdominal binder improves lung volumes and voice in people with tetraplegic spinal cord injury.

      Objective

      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.

      Design

      Randomized crossover study.

      Setting

      Large university-affiliated referral hospital.

      Participants

      Consenting participants (N=14, 13 men and 1 woman) with recent, motor complete, C3-T1 spinal cord injury.

      Interventions

      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.

      Results

      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).

      Conclusions

      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.

      Key Words

      List of Abbreviations:

      AB (abdominal binder), FEV1 (forced expiratory volume in 1 second), FVC (forced vital capacity), MAP (mean arterial pressure), MEP (maximum expiratory pressure), MIP (maximum inspiratory pressure), MSV (maximum sustained vowel), OH (orthostatic hypotension), PEF (peak expiratory flow), SCI (spinal cord injury), SPL (sound pressure level)
      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.

      AIHW: Norton L 2010. Spinal cord injury, Australia 2007–08. Injury research and statistics series no. 52. Cat. no. INJCAT 128. Canberra, Australia: AIHW.

      Complications arising from compromised respiratory function are the major cause of morbidity and mortality in people after cervical SCI.
      • DeVivo M.J.
      • Krause S.
      • Lammertse D.P.
      Recent trends in mortality and causes of death among persons with spinal cord injury.
      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.
      • Brown R.
      • DiMarco A.F.
      • Hoit J.D.
      • Garshick E.
      Respiratory dysfunction and management in spinal cord injury.
      The vital capacity can be reduced to 50% to 80% of predicted
      • Anke A.
      • Aksnes A.K.
      • Stanghelle J.K.
      • Hjeltnes N.
      Lung volumes in tetraplegic patients according to cervical spinal cord injury level.
      value, with a reduction in total lung capacity to 60% to 80% predicted
      • Jain N.B.
      • Brown R.
      • Tun C.G.
      • Gagnon D.
      • Garshick E.
      Determinants of forced expiratory volume in 1 second (FEV1), forced vital capacity (FVC), and FEV1/FVC in chronic spinal cord injury.
      in nonventilated patients with tetraplegia.
      Binding of the paralyzed abdomen has been used with the aim of increasing lung volumes and respiratory muscle strength.
      • Wadsworth B.W.
      • Haines T.P.
      • Cornwell P.L.
      • Paratz J.D.
      Abdominal binder use in people with spinal cord injuries: a systematic review and meta-analysis.
      • Hopman M.T.
      • Dueck C.
      • Monroe M.
      • Philips W.T.
      • Skinner J.S.
      Limits to maximal performance in individuals with spinal cord injury.
      • Boaventura C.D.
      • Gastaldi A.C.
      • Silveira J.M.
      • Santos P.R.
      • Guimaraes R.C.
      • De Lima L.C.
      Effect of an abdominal binder on the efficacy of respiratory muscles in seated and supine tetraplegic patients.
      • Estenne M.
      • Van Muylem A.
      • Gorini M.
      • Kinnear W.
      • Heilporn A.
      • De Troyer A.
      Effects of abdominal strapping on forced expiration in tetraplegic patients.
      • Goldman J.M.
      • Rose L.S.
      • Williams S.J.
      • Silver J.R.
      • Denison D.M.
      Effect of abdominal binders on breathing in tetraplegic patients.
      • Hart N.
      • Laffont I.
      • de La Sota A.P.
      • et al.
      Respiratory effects of combined truncal and abdominal support in patients with spinal cord injury.
      • Kerk J.K.
      • Clifford P.S.
      • Snyder A.C.
      • et al.
      Effect of an abdominal binder during wheelchair exercise.
      A recent systematic review and meta-analysis
      • Wadsworth B.W.
      • Haines T.P.
      • Cornwell P.L.
      • Paratz J.D.
      Abdominal binder use in people with spinal cord injuries: a systematic review and meta-analysis.
      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.
      • Bravo G.
      • Guizar-Sahagun G.
      • Ibarra A.
      • Centurion D.
      • Villalon C.M.
      Cardiovascular alterations after spinal cord injury: an overview.
      While numerous SCI textbooks
      • Sisto S.A.
      • Druin E.
      • Sliwinski M.M.
      Spinal cord injuries: management and rehabilitation.
      • Somers M.F.
      Spinal cord injury: functional rehabilitation.
      • Zejdlik J.
      Management of spinal cord injury.
      • Buchanan L.
      • Nawoczenski D.
      Spinal cord injury: concepts and management approaches.
      recommend the use of an AB for the management of orthostatic hypotension (OH), limited evidence exists for this application.
      • Gilles D.J.
      • Wouda M.
      • Hjeltnes N.
      Non-pharmacological management of orthostatic hypotension after spinal cord injury: a critical review of the literature.
      There is a similar lack of studies into voice impairment after SCI. Voice production is dependent on sufficient respiratory support (volume and pressure) to generate sound.
      • Hoit J.D.
      • Banzett R.B.
      • Brown R.
      • Loring S.H.
      Speech breathing in individuals with cervical spinal cord injury.
      • Hoit J.D.
      • Banzett R.B.
      • Brown R.
      Binding the abdomen can improve speech in men with phrenic nerve pacers.
      People with tetraplegia have impaired vocal ability and use muscle recruitment strategies during speech that are different from those used by the able-bodied person.
      • Tamplin J.
      • Brazzale D.J.
      • Pretto J.J.
      • et al.
      Assessment of breathing patterns and respiratory muscle recruitment during singing and speech in quadriplegia.
      Hence, they may present with inadequate loudness, short breath groups, slow inspirations, breathiness, and decreased utterance duration.
      • MacBean N.
      • Ward E.
      • Murdoch B.
      • Cahill L.
      • Salley M.
      • Geraghty T.
      Characteristics of speech following cervical spinal cord injury.
      • Watson P.J.
      • Hixon T.J.
      Effects of abdominal trussing on breathing and speech in men with cervical spinal cord injury.
      • Hixon T.J.
      • Putnam A.H.B.
      Voice disorders in relation to respiratory kinematics.
      The one study that investigated speech outcomes with the use of a nonelastic abdominal “truss” in 3 participants found increased syllables per breath and overall listener preference when trussed.
      • Watson P.J.
      • Hixon T.J.
      Effects of abdominal trussing on breathing and speech in men with cervical spinal cord injury.
      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.

      Methods

       Participants

      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.

       Respiratory Measures

      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
      • Miller M.R.
      • Hankinson J.L.
      • Brusasco V.
      • et al.
      Standardisation of spirometry.
      and modified to incorporate the limitations associated with SCI.
      • Kelley A.
      • Garshick E.
      • Gross E.R.
      • Lieberman S.L.
      • Tun C.G.
      • Brown R.
      Spirometry testing standards in spinal cord injury.
      • Ashba J.
      • Garshick E.
      • Tun C.G.
      • et al.
      Spirometry: acceptability and repeatability in spinal cord injured subjects.
      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.
      • Quanjer Ph H.
      • Tammeling G.J.
      • Cotes J.E.
      • Pedersen O.F.
      • Peslin R.
      • Yernault J.C.
      Lung volumes and forced ventilatory flows.
      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.
      American Thoracic Society/European Respiratory Society
      ATS/ERS statement on respiratory muscle testing.
      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.

       Voice Measures

      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.
      • Rosen K.M.
      • Kent R.D.
      • Duffy J.R.
      Task-based profile of vocal intensity decline in Parkinsons disease.
      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

       Hemodynamic Measures

      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:
      MAP=diastolicarterialpressure+1/3[systolicarterialpressurediastolicarterialpressure]


      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).
      Figure thumbnail gr1
      Fig 1Participant without and with an elasticated AB.

       Procedure

      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.
      • Kerk J.K.
      • Clifford P.S.
      • Snyder A.C.
      • et al.
      Effect of an abdominal binder during wheelchair exercise.
      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.

       Statistical Methods

      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.

      Results

       Participants

      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.
      Table 1Subject Details
      SubjectAdm AISD/C AISAge (y)Height (cm)Weight (kg)CauseSmokerAx Time Points
      1 denotes 6 weeks, 2 denotes 3 months, and 3 denotes 6 months after commencing daily wheelchair use.
      AB Use
      1C4 AC5 B1918484WakeboardingNo1, 2, 3AB daily
      2T1 AT5 A3017873MBCNo1, 2AB ceased 2wk before test 1
      3C4 AC5 A2718077BodysurfingNo1, 2, 3AB ceased week of test 2
      4C4 BC5 B2117457SandboardingNo1, 2, 3AB daily
      5C6 BC4 C7317890FallNo1, 2AB daily
      6C4 AC4 B1918082DivingNo1, 2, 3AB daily
      7C5 AC7 B2817157DivingNo1, 2, 3AB daily
      8C5 AT1 A2618482GunshotSmoker—pack a day since age 16y1AB daily
      9
      Female participant.
      C5 BC4 D6216065Horse ridingNo1, 2, 3AB daily
      10C5 AC8 C1818554Bike ridingNo1, 2, 3AB daily
      11C4 BC4 B3118382DivingNo1, 2, 3AB daily
      12C3 AC4 A2918079DivingNo1, 2, 3AB daily
      13C4 AC4 A3118467FallSmoker—pack a day since age 17y1, 2, 3AB daily
      14C4 AC4 C3017971SurfingNo1, 2, 3AB ceased 1wk prior to test 3
      Abbreviations: Adm, admission; AIS, American Spinal Injury Association Impairment Scale; Ax, assessment; D/C, discharge; MBC, motorbike collision.
      low asterisk Female participant.
      1 denotes 6 weeks, 2 denotes 3 months, and 3 denotes 6 months after commencing daily wheelchair use.
      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
      SubjectAx Time PointAB
      1 refers to AB in place, 0 no AB in place.
      FVC (L)FVCpred (%)FEV1 (L)FEV1pred (%)PEF (L/s)PEFpred (%)MIP (cmH2O)MEP (cmH2O)MSV (s)SPL (dB)MAP (mmHg)
      1113.56692.44583.8346NTNT3.45272.09NT
      1102.91572.16513.6143NTNT3.69969.87NT
      1213.51682.60614.0549NTNT4.81363.51NT
      1202.34451.76422.8334NTNT3.71063.89NT
      1315.361044.00945.316468409.96669.5071
      1304.44862.92693.644470368.22367.1467
      2102.76532.32544.3444NTNT9.07957.05NT
      2113.17612.64614.7048NTNT13.10763.49NT
      2203.72722.92685.8259NTNT13.28563.59NT
      2213.97773.28766.1963NTNT15.00666.17NT
      230NTNTNTNTNTNTNTNTNTNTNT
      231NTNTNTNTNTNTNTNTNTNTNT
      3112.78522.28514.8148NTNT9.54570.31NT
      3102.25421.44322.1121NTNT7.75668.33NT
      3213.43642.20494.0340NTNT15.34071.00NT
      3202.99561.76392.8729NTNT10.94170.94NT
      3312.98561.76402.7828412914.51863.2472
      3302.53481.56352.8328312011.53064.3968
      4102.29461.96464.5647NTNT4.27365.73NT
      4112.76552.36555.6758NTNT6.95366.82NT
      4212.48492.04483.7538NTNT8.07760.78NT
      4202.13421.96463.6638NTNT7.69062.24NT
      4302.58512.08494.514682448.24165.8071
      4312.54502.16513.51181595.48065.4170
      5102.84691.88603.664542397.58156.30NT
      5113.35821.88603.214039436.50957.86NT
      5213.02741.84593.254069548.99854.9279
      5202.97732.20705.096358498.00956.3981
      531NTNTNTNTNTNTNTNTNTNTNT
      530NTNTNTNTNTNTNTNTNTNTNT
      6112.41481.76433.033758309.40464.17NT
      6102.30461.52372.5431562611.58762.57NT
      6202.55511.68412.6833502611.32751.3281
      6212.88581.92472.8936443710.51552.2280
      6313.20642.36573.7746644511.66667.2583
      6302.21441.52372.5131583610.67365.6882
      7102.25471.88464.3846462710.41358.52NT
      7112.26471.84454.3846502412.29154.88NT
      7202.31481.92475.5458573017.85471.0182
      7212.70562.36574.1544643112.40170.3391
      7313.23672.64645.0653724615.06769.9194
      7302.50522.08513.9842533711.62065.7561
      8112.95532.00432.8628744713.76560.56NT
      8102.47441.92413.3432653710.73058.96NT
      821NTNTNTNTNTNTNTNTNTNTNT
      820NTNTNTNTNTNTNTNTNTNTNT
      830NTNTNTNTNTNTNTNTNTNTNT
      831NTNTNTNTNTNTNTNTNTNTNT
      9102.17831.88853.6162562913.39749.6169
      9112.54972.04934.137070359.79952.8870
      9212.51961.96894.1170755317.41659.1672
      9202.11811.80823.50607247DNU49.7871
      9312.37912.00913.7965865014.79068.5273
      9302.11811.76803.8466784012.64867.6477
      10112.32462.16534.4054753812.99071.9292
      10102.30461.96483.1939564010.16771.4576
      10213.21562.76594.7853927512.82172.6690
      10202.81562.48604.9961745210.26171.5489
      10302.99602.48605.0162836610.679DNU79
      10313.31623.04665.856480637.80767.9390
      11103.93732.76615.9259755113.95264.6196
      11113.98732.84635.8258734616.02562.97110
      11203.41632.64594.8548674314.27270.55102
      11213.74693.24726.2262705715.99674.01100
      11304.05753.36754.7047726215.09069.16104
      11313.46642.64594.5445785816.11178.69109
      12112.27431.20271.771866276.19472.7879
      12101.98371.08241.621660265.28669.2385
      12212.40461.44331.711773586.62860.5485
      12201.97371.12251.331359334.58256.8984
      12312.51481.28291.791876316.82474.3572
      12302.06391.20271.811856336.05672.0373
      13112.13392.08465.63555236NTNTNT
      13101.72311.64364.63463831NTNTNT
      13201.82331.72384.614543175.12456.31NT
      13212.04371.96435.265246224.60258.58NT
      13312.67492.44545.795765316.04771.0580
      13302.13392.04454.954944256.01572.7982
      14102.15411.88433.763847287.21760.3872
      14112.08401.80414.925048256.68156.9970
      14212.27441.92444.324453254.72668.3570
      14202.29441.84424.174244204.45366.5478
      14312.37462.08484.8749552510.04666.2185
      14302.34451.96454.6948482312.74564.380
      Abbreviations: Ax, assessment; DNU, data not useable; NT, not tested; pred, predicted.
      low asterisk 1 refers to AB in place, 0 no AB in place.
      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
      TestMean ± SD, nCoefficient (95% Confidence Interval) P
      First Assessment 6wk After MobilizingSecond Assessment 3mo After MobilizingThird Assessment 6mo After MobilizingEffect of AB
      The difference in mean values for AB and no AB.
      Effect of Assessment Number
      Three assessment time points were used to collect outcomes.
      AB Use×Time Interaction
      This measures whether the time point at which subjects ceased wearing an AB daily had any impact on outcomes.
      Order of Testing Effect
      This measures whether subjects performed differently for the first condition or the second condition over the time points regardless of whether an AB was in place for testing.
      ABNo ABABNo ABABNo AB
      FVC (L)2.75±0.58 n=142.45±0.54 n=142.86±0.58 n=132.57±0.57 n=132.94±0.96 n=112.72±0.80 n=110.34 (0.10–0.58) P=0.0050.27 (0.11–0.42) P=0.001−0.01 (−0.13 to 0.11) P=0.895−0.10 (−0.20 to −0.00) P=0.044
      FEV1 (L)2.09±0.41 n=141.88±0.40 n=142.22±0.55 n=131.98±0.47 n=132.29±0.80 n=112.09±0.63 n=110.25 (−0.01 to 0.51) P=0.050.18 (0.07–0.30) P=0.0010.01 (−0.12 to 0.14) P=0.887−0.04 (−0.14 to 0.63) P=0.446
      PEF (L/s)4.23±1.18 n=143.66±1.11 n=144.15±1.24 n=134.00±1.32 n=134.10±1.43 n=113.86±1.07 n=110.81 (0.13–1.48) P=0.020.25 (−0.01 to 0.51) P=0.056−0.20 (−0.53 to 0.13) P=0.240−0.05 (−0.32 to 0.22) P=0.691
      MIP (cmH2O)−60.5±12.8 n=10−54.1±11.2 n=10−65.1±15.3 n=9−58.2±11.3 n=9−69.6±13.1 n=11−61.4±16.9 n=117.40 (1.64–13.14) P=0.016.20 (3.18–9.21) P<0.001−0.40 (−3.05 to 2.25) P=0.77−4.01 (−6.27 to 1.75) P<0.001
      MEP (cmH2O)35.1±8.5 n=1033.4±8.2 n=1045.8±17.8 n=935.2±13.0 n=943.4±13.3 n=1138.4±14.7 n=115.37 (−1.15 to 11.90) P=0.118.34 (4.93–11.76) P<0.0010.23 (−2.80 to 3.26) P=0.88−0.62 (−3.16 to 1.92) P=0.63
      MSV time (s)9.75±3.70 n=138.86±3.26 n=1310.57±4.60 n=138.58±5.00 n=1310.76±3.92 n=1110.32±2.88 n=113.75 (0.90–6.60) P=0.012.12 (1.18–3.07) P<0.001−1.21 (−2.61 to 1.93) P=0.09−0.28 (−1.37 to 0.81) P=0.62
      SPL (dB)63.7±6.8 n=1362.5±6.4 n=1364.0±6.9 n=1362.4±7.7 n=1369.3±4.3 n=1167.5±3.0 n=101.14 (−1.31 to 3.58) P=0.3628.21 (24.57–31.84) P<0.0010.28 (−0.93 to 1.48) P=0.6520.26 (−0.72 to 1.24) P=0.61
      MAP (mmHg)84.2±17.0 n=579.6±10.9 n=583.38±10.1 n=883.5±9.1 n=881.73±12.2 n=1176.73±11.3 n=114.41 (−6.15 to 14.97) P=0.4126.73 (20.93–32.52) P<0.001−0.13 (−4.67 to 4.41) P=0.961.93 (−1.70 to 5.55) P=0.30
      low asterisk The difference in mean values for AB and no AB.
      Three assessment time points were used to collect outcomes.
      This measures whether the time point at which subjects ceased wearing an AB daily had any impact on outcomes.
      § This measures whether subjects performed differently for the first condition or the second condition over the time points regardless of whether an AB was in place for testing.
      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).

       Respiratory

      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.
      Figure thumbnail gr2
      Fig 2Mean FVC and FEV1 outcome with and without AB.

       Voice

      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).

       Hemodynamics

      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.

      Discussion

      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.
      • Wadsworth B.W.
      • Haines T.P.
      • Cornwell P.L.
      • Paratz J.D.
      Abdominal binder use in people with spinal cord injuries: a systematic review and meta-analysis.
      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.
      • Boaventura C.D.
      • Gastaldi A.C.
      • Silveira J.M.
      • Santos P.R.
      • Guimaraes R.C.
      • De Lima L.C.
      Effect of an abdominal binder on the efficacy of respiratory muscles in seated and supine tetraplegic patients.
      • Goldman J.M.
      • Rose L.S.
      • Williams S.J.
      • Silver J.R.
      • Denison D.M.
      Effect of abdominal binders on breathing in tetraplegic patients.
      • Kerk J.K.
      • Clifford P.S.
      • Snyder A.C.
      • et al.
      Effect of an abdominal binder during wheelchair exercise.
      While 1 other study had found a significant increase in FEV1 and PEF with the AB,
      • Hart N.
      • Laffont I.
      • de La Sota A.P.
      • et al.
      Respiratory effects of combined truncal and abdominal support in patients with spinal cord injury.
      another study found no significant effect of the AB on these outcomes
      • Maloney F.P.
      Pulmonary function in quadriplegia: effects of a corset.
      and a third found no significant effect on PEF.
      • Lin K.H.
      • Lai Y.L.
      • Wu H.D.
      • Wang T.Q.
      • Wang Y.H.
      Effects of an abdominal binder and electrical stimulation on cough in patients with spinal cord injury.
      Our findings of significantly improved FEV1 and PEF with the use of the AB support recent findings of increased mean cough PEF rates with the AB.
      • Julia P.E.
      • Sa'ari M.Y.
      • Hasnan N.
      Benefit of triple-strap abdominal binder on voluntary cough in patients with spinal cord injury.
      Of the 2 prior studies that measured MEP,
      • Boaventura C.D.
      • Gastaldi A.C.
      • Silveira J.M.
      • Santos P.R.
      • Guimaraes R.C.
      • De Lima L.C.
      Effect of an abdominal binder on the efficacy of respiratory muscles in seated and supine tetraplegic patients.
      • Hart N.
      • Laffont I.
      • de La Sota A.P.
      • et al.
      Respiratory effects of combined truncal and abdominal support in patients with spinal cord injury.
      an indicator of expiratory muscle strength and thus cough, only 1 found it to be significantly greater with the AB when the participant was seated.
      • Boaventura C.D.
      • Gastaldi A.C.
      • Silveira J.M.
      • Santos P.R.
      • Guimaraes R.C.
      • De Lima L.C.
      Effect of an abdominal binder on the efficacy of respiratory muscles in seated and supine tetraplegic patients.
      While Hart et al
      • Hart N.
      • Laffont I.
      • de La Sota A.P.
      • et al.
      Respiratory effects of combined truncal and abdominal support in patients with spinal cord 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.
      • De Troyer A.
      Mechanical role of the abdominal muscles in relation to posture.
      Interventions targeting improved inspiratory and expiratory capacity, such as inspiratory threshold training
      • Liaw M.
      • Lin M.
      • Cheng P.
      • Wong M.
      • Tang F.
      Resistive inspiratory muscle training: its effectiveness in patients with acute complete cervical cord injury.
      or strengthening of the pectoral muscles,
      • Estenne M.
      • Knoop C.
      • Van Vaerenbergh J.
      • Heilporn A.
      • De Troyer A.
      The effect of pectoralis muscle training in tetraplegic subjects.
      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
      • Prathanee B.
      • Watthanathon J.
      • Ruangjirachuporn P.
      Phonation time, phonation volume and air flow rate in normal adults.
      and the best mean MSV for this study at 10.76 seconds, any improvement may be considered desirable. While Watson and Hixon
      • Watson P.J.
      • Hixon T.J.
      Effects of abdominal trussing on breathing and speech in men with cervical spinal cord injury.
      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.
      • Watson P.J.
      • Hixon T.J.
      Effects of abdominal trussing on breathing and speech in men with cervical spinal cord injury.
      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).
      • Pearsons K.S.
      • Bennett R.L.
      • Fidell S.
      Speech levels in various noise environments (Report No. EPA-600/1-77-025).
      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.
      • Cazzola M.
      • MacNee W.
      • Martinez F.J.
      • et al.
      Outcomes for COPD pharmacological trials: from lung function to biomarkers.
      Hypotension, being a significant complication after an acute SCI, can considerably delay and impede the participation and rehabilitation of patients.
      • Blackmer J.
      Orthostatic hypotension in spinal cord injured patients.
      • Illman A.
      • Stiller K.
      • Williams M.
      The prevalence of orthostatic hypotension during physiotherapy treatment in patients with an acute spinal cord injury.
      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,
      • Sidorov E.V.
      • Townson A.F.
      • Dvorak M.F.
      • Kwon B.K.
      • Steeves J.
      • Krassioukov A.
      Orthostatic hypotension in the first month following acute spinal cord injury.
      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.
      • Wing P.C.
      Early acute management in adults with spinal cord injury: a clinical practice guideline for health-care providers.
      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.

       Study Limitations

      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.

      Conclusions

      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.
      • a
        CareFusion Switzerland, 317 Sàrl A-One Business Centre Zone D'activités Vers-la-Pièce no 10 CH-1180 Rolle, Suisse.
      • b
        AKG model C420; AKG Acoustics GmbH Lemböckgasse 21-25, A-1230 Vienna, Austria.
      • c
        CSpeech, Madison, Wisconsin. http://userpages.chorus.net/cspeech.
      • d
        KayPENTAX, 3 Paragon Dr, Montvale, NJ 07645.
      • e
        J.A. Davey Pty Ltd ATT, 626 Lorimer St, Port Melbourne, Victoria 3207, Australia.
      • f
        Medical Accessories, 11/43 Lang Parade, Milton, Queensland 4064, Australia.
      • g
        StataCorp LP, 4905 Lakeway Dr, College Station, TX 77845-4512.

      References

      1. AIHW: Norton L 2010. Spinal cord injury, Australia 2007–08. Injury research and statistics series no. 52. Cat. no. INJCAT 128. Canberra, Australia: AIHW.

        • DeVivo M.J.
        • Krause S.
        • Lammertse D.P.
        Recent trends in mortality and causes of death among persons with spinal cord injury.
        Arch Phys Med Rehabil. 1999; 80: 1411-1419
        • Brown R.
        • DiMarco A.F.
        • Hoit J.D.
        • Garshick E.
        Respiratory dysfunction and management in spinal cord injury.
        Respir Care. 2006; 52: 853-868
        • Anke A.
        • Aksnes A.K.
        • Stanghelle J.K.
        • Hjeltnes N.
        Lung volumes in tetraplegic patients according to cervical spinal cord injury level.
        Scand J Rehabil Med. 1993; 25: 73-77
        • Jain N.B.
        • Brown R.
        • Tun C.G.
        • Gagnon D.
        • Garshick E.
        Determinants of forced expiratory volume in 1 second (FEV1), forced vital capacity (FVC), and FEV1/FVC in chronic spinal cord injury.
        Arch Phys Med Rehabil. 2006; 87: 1327-1333
        • Wadsworth B.W.
        • Haines T.P.
        • Cornwell P.L.
        • Paratz J.D.
        Abdominal binder use in people with spinal cord injuries: a systematic review and meta-analysis.
        Spinal Cord. 2009; 47: 274-285
        • Hopman M.T.
        • Dueck C.
        • Monroe M.
        • Philips W.T.
        • Skinner J.S.
        Limits to maximal performance in individuals with spinal cord injury.
        Int J Sports Med. 1998; 19: 98-103
        • Boaventura C.D.
        • Gastaldi A.C.
        • Silveira J.M.
        • Santos P.R.
        • Guimaraes R.C.
        • De Lima L.C.
        Effect of an abdominal binder on the efficacy of respiratory muscles in seated and supine tetraplegic patients.
        Physiotherapy. 2003; 89: 290-295
        • Estenne M.
        • Van Muylem A.
        • Gorini M.
        • Kinnear W.
        • Heilporn A.
        • De Troyer A.
        Effects of abdominal strapping on forced expiration in tetraplegic patients.
        Am J Respir Crit Care Med. 1998; 157: 95-98
        • Goldman J.M.
        • Rose L.S.
        • Williams S.J.
        • Silver J.R.
        • Denison D.M.
        Effect of abdominal binders on breathing in tetraplegic patients.
        Thorax. 1986; 41: 940-945
        • Hart N.
        • Laffont I.
        • de La Sota A.P.
        • et al.
        Respiratory effects of combined truncal and abdominal support in patients with spinal cord injury.
        Arch Phys Med Rehabil. 2005; 86: 1447-1451
        • Kerk J.K.
        • Clifford P.S.
        • Snyder A.C.
        • et al.
        Effect of an abdominal binder during wheelchair exercise.
        Med Sci Sports Exerc. 1995; 27: 913-919
        • Bravo G.
        • Guizar-Sahagun G.
        • Ibarra A.
        • Centurion D.
        • Villalon C.M.
        Cardiovascular alterations after spinal cord injury: an overview.
        Curr Med Chem Cardiovasc Hematol Agents. 2004; 2: 133-148
        • Sisto S.A.
        • Druin E.
        • Sliwinski M.M.
        Spinal cord injuries: management and rehabilitation.
        in: Mosby Elsevier, Columbia2008: 69-71
        • Somers M.F.
        Spinal cord injury: functional rehabilitation.
        in: 2nd ed. Prentice-Hall, Maryland Heights2000: 327
        • Zejdlik J.
        Management of spinal cord injury.
        in: 2nd sub ed. Jones & Bartlett, Toronto, Canada1992 (p 268 and 319)
        • Buchanan L.
        • Nawoczenski D.
        Spinal cord injury: concepts and management approaches.
        in: 1st ed. Williams & Wilkins, Philadelphia1987: 72
        • Gilles D.J.
        • Wouda M.
        • Hjeltnes N.
        Non-pharmacological management of orthostatic hypotension after spinal cord injury: a critical review of the literature.
        Spinal Cord. 2008; 46: 652-659
        • Hoit J.D.
        • Banzett R.B.
        • Brown R.
        • Loring S.H.
        Speech breathing in individuals with cervical spinal cord injury.
        J Speech Lang Hear Res. 1990; 33: 798-807
        • Hoit J.D.
        • Banzett R.B.
        • Brown R.
        Binding the abdomen can improve speech in men with phrenic nerve pacers.
        Am J Speech Lang Pathol. 2002; 11: 71-76
        • Tamplin J.
        • Brazzale D.J.
        • Pretto J.J.
        • et al.
        Assessment of breathing patterns and respiratory muscle recruitment during singing and speech in quadriplegia.
        Arch Phys Med Rehabil. 2011; 92: 250-256
        • MacBean N.
        • Ward E.
        • Murdoch B.
        • Cahill L.
        • Salley M.
        • Geraghty T.
        Characteristics of speech following cervical spinal cord injury.
        J Med Speech Lang Pathol. 2006; 14: 167-184
        • Watson P.J.
        • Hixon T.J.
        Effects of abdominal trussing on breathing and speech in men with cervical spinal cord injury.
        J Speech Lang Hear Res. 2001; 44: 751-762
        • Hixon T.J.
        • Putnam A.H.B.
        Voice disorders in relation to respiratory kinematics.
        Semin Speech Lang. 1983; 4: 217-231
        • Miller M.R.
        • Hankinson J.L.
        • Brusasco V.
        • et al.
        Standardisation of spirometry.
        Eur Respir J. 2005; 26: 319-338
        • Kelley A.
        • Garshick E.
        • Gross E.R.
        • Lieberman S.L.
        • Tun C.G.
        • Brown R.
        Spirometry testing standards in spinal cord injury.
        Chest. 2003; 123: 725-730
        • Ashba J.
        • Garshick E.
        • Tun C.G.
        • et al.
        Spirometry: acceptability and repeatability in spinal cord injured subjects.
        J Am Paraplegia Soc. 1993; 16: 197-203
        • Quanjer Ph H.
        • Tammeling G.J.
        • Cotes J.E.
        • Pedersen O.F.
        • Peslin R.
        • Yernault J.C.
        Lung volumes and forced ventilatory flows.
        Eur Respir J. 1993; 6: 5-40
        • American Thoracic Society/European Respiratory Society
        ATS/ERS statement on respiratory muscle testing.
        Am J Respir Crit Care Med. 2002; 166: 518-624
        • Rosen K.M.
        • Kent R.D.
        • Duffy J.R.
        Task-based profile of vocal intensity decline in Parkinsons disease.
        Folia Phoniatr Logop. 2005; 57: 28-37
        • Maloney F.P.
        Pulmonary function in quadriplegia: effects of a corset.
        Arch Phys Med Rehabil. 1979; 60: 261-265
        • Lin K.H.
        • Lai Y.L.
        • Wu H.D.
        • Wang T.Q.
        • Wang Y.H.
        Effects of an abdominal binder and electrical stimulation on cough in patients with spinal cord injury.
        J Formos Med Assoc. 1998; 97: 292-295
        • Julia P.E.
        • Sa'ari M.Y.
        • Hasnan N.
        Benefit of triple-strap abdominal binder on voluntary cough in patients with spinal cord injury.
        Spinal Cord. 2011; 49: 1138-1142
        • De Troyer A.
        Mechanical role of the abdominal muscles in relation to posture.
        Resp Physiol. 1983; 53: 341-353
        • Liaw M.
        • Lin M.
        • Cheng P.
        • Wong M.
        • Tang F.
        Resistive inspiratory muscle training: its effectiveness in patients with acute complete cervical cord injury.
        Arch Phys Med Rehabil. 2000; 81: 752-756
        • Estenne M.
        • Knoop C.
        • Van Vaerenbergh J.
        • Heilporn A.
        • De Troyer A.
        The effect of pectoralis muscle training in tetraplegic subjects.
        Am Rev Respir Dis. 1989; 139: 1218-1222
        • Prathanee B.
        • Watthanathon J.
        • Ruangjirachuporn P.
        Phonation time, phonation volume and air flow rate in normal adults.
        J Med Assoc Thai. 1994; 77: 639-645
        • Pearsons K.S.
        • Bennett R.L.
        • Fidell S.
        Speech levels in various noise environments (Report No. EPA-600/1-77-025).
        U.S. Environmental Protection Agency, Washington (DC)1977
        • Cazzola M.
        • MacNee W.
        • Martinez F.J.
        • et al.
        Outcomes for COPD pharmacological trials: from lung function to biomarkers.
        Eur Respir J. 2008; 31: 416-468
        • Blackmer J.
        Orthostatic hypotension in spinal cord injured patients.
        J Spinal Cord Med. 1997; 20: 212-217
        • Illman A.
        • Stiller K.
        • Williams M.
        The prevalence of orthostatic hypotension during physiotherapy treatment in patients with an acute spinal cord injury.
        Spinal Cord. 2000; 38: 741-747
        • Sidorov E.V.
        • Townson A.F.
        • Dvorak M.F.
        • Kwon B.K.
        • Steeves J.
        • Krassioukov A.
        Orthostatic hypotension in the first month following acute spinal cord injury.
        Spinal Cord. 2008; 46: 65-69
        • Wing P.C.
        Early acute management in adults with spinal cord injury: a clinical practice guideline for health-care providers.
        J Spinal Cord Med. 2008; 31: 403-479