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Journal of Neurologic Physical Therapy:
doi: 10.1097/NPT.0b013e318282a1f0
Research Articles

Tolerance of a Standing Tilt Table Protocol by Patients an Inpatient Stroke Unit Setting: A Pilot Study

Baltz, Mathew J. PT, DPT; Lietz, Hendrika L. PT, DPT, NCS; Sausser, Ida Trott PT, DPT; Kalpakjian, Claire PhD; Brown, Devin MD

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Author Information

University of Michigan Health System, Ann Arbor.

Correspondence: Mathew J. Baltz, PT, DPT, University of Michigan Health System, 1500 E Medical Center Dr, Ann Arbor, MI 48109 (mathewj@med.umich.edu).

This study was funded by a grant from the University of Michigan Practice-Oriented Research Training (PORT) Program and the Department of Physical Medicine and Rehabilitation. The PORT Program is supported by a grant from the National Institutes of Health Clinical and Translations Sciences Award (UL1RR024986).

A poster presentation of this work was presented at the James Rae Scientific Day for residents of Physical Medicine and Rehabilitation at the University of Michigan Hospital in May 2011.

A poster presentation of this work has been accepted to the APTA Combined Sections Symposium scheduled for February 2012. A poster presentation has been accepted by the American Heart Association International Stroke Conference 2012.

Supplemental digital content is available for this article. Direct URL citations appear in the printed text and are provided in the HTML and PDF versions of this article on the journal's Web site (www.jnpt.org).

The authors declare no conflicts of interest.

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Abstract

Background and Purpose: To describe and examine physiologic and self-reported indices of tolerance to a standing tilt table protocol (STTP) among patients following an acute stroke.

Methods: We undertook a prospective, observational pilot study of patients admitted to a stroke unit of a single academic medical center. A clinical protocol for the use of the tilt table was developed and applied to subjects in the acute phase following a stroke. The protocol involved a stepwise process to gradually raise the subject into a standing position on the tilt table platform, at 10° intervals from 60° to 90°. Tolerance of the STTP was operationally defined as the ability to sustain 60° or greater of tilt table inclination for a minimum of 5 minutes, without signs or symptoms of intolerance. Specific measures recorded were frequencies of the highest angle achieved, the duration of standing time tolerated, and physiologic response.

Results: Thirty-six patients with ischemic or hemorrhagic stroke (22 women and 14 men) aged 24 to 87 (mean age = 62, SD = 16) years participated in a single trial of the STTP. Fifty-three percent of subjects (N = 19) attained 60° or higher on the tilt table, with a mean total standing time of approximately 9 minutes.

Discussion and Conclusions: This pilot study suggests that the use of a tilt table is well tolerated among patients in the acute stroke phase and may be an effective tool for introducing early upright mobilization to a medically fragile patient population.

Video Abstract available (see Video, Supplemental Digital Content 1, available at: http://links.lww.com/JNPT/A35) for more insights from the authors.

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INTRODUCTION

Physical therapists employ multiple methods to limit the negative effects of prolonged bed rest, to address the primary deficits of stroke, and to facilitate functional recovery. Often, an eclectic treatment approach is provided based on individual therapist's strengths and philosophy, as well as patient presentation and tolerance. However, with this approach, it is difficult to identify a best practice that has the greatest impact on patient outcomes.1 The American Stroke Association 2011 stroke statistic update indicates that 795 000 people will have a new or recurrent stroke each year, and 7 million Americans, older than 20 years, have already had a stroke.2 On average, every 40 seconds someone will experience a stroke. Of all strokes, 87% are due to ischemia, 10% are due to intracerebral hemorrhage, and 3% to subarachnoid hemorrhage.3

Following stroke and during hospitalization, patients who are unable to safely stand and perform independent transfers are at an increased risk for multiple medical complications.4 Roth et al5 report that 75% of rehabilitating stroke patients experience at least 1 medical complication during their inpatient hospital stay. The most common complications during the first week following stroke are pain, fever (temperature ≥ 38°C), stroke extension, urinary tract infection, nonserious falls, and myocardial infarction.6 Nonambulatory patients also have an increased risk for deep vein thrombosis or pulmonary embolus7 and complications from immobility account for up to 51% of deaths in the first 30 days after ischemic stroke.8

Despite knowledge of the benefits of mobility for hospitalized patients, multiple barriers exist to early mobilization. Those barriers may include (1) concern for hemodynamic instability due to acute medical condition; (2) impaired level of consciousness affecting participation; (3) hospital personnel time constraints due to increased nonclinical patient care responsibilities4; and (4) concern for increased patient fall risk or physical injury to staff/caregiver during assisted transfers.

Patients hospitalized within a stroke unit often have impairments that prevent them from safely transferring out of bed. In a large, multicentered trial of very early mobilization (VEM) within the first 24 hours of stroke, Bernhardt et al9 demonstrated that VEM, which consisted of “assist[ing] the patient to be upright and out of bed (sitting or standing as able) at least twice per day; in addition to their usual care” appears safe and feasible. In addition, VEM was found to improve overall function, reduced time for return to unassisted walking (3.5 days vs 7 days for controls),10 and increased the likelihood of discharge directly to home from a combined acute inpatient rehabilitation stroke unit.11

While in the acute stroke phase, concern regarding hemodynamic variability and its effect on cerebral blood flow may predispose patients to prolonged bed rest. There are theoretical concerns based on transcranial Doppler studies12,13 that upright positioning could result in infarction extension due to lowering blood pressure within the hypoperfused perilesional region (penumbra), where dysfunctional autoregulation of cerebral blood flow may occur. However, additional studies have been inconclusive,14,15 and it is still unclear whether slowed cerebral blood flow velocity leads to an extension of the infarct core or further injury of the penumbra. The volume of preserved penumbral tissue has been significantly related to spontaneous neurologic recovery following stroke.16 It is the penumbra, the moderately hypoperfused, nonfunctioning but still viable brain tissue surrounding the irreversibly damaged ischemic core,17 that may be susceptible to altered hemodynamics, and therefore any risk of injury to this area should be avoided at all costs.

Clinically, the use of a tilt table is a recognized rehabilitation tool to aid upright standing activity. Empirical evidence suggests that the use of a tilt table is an effective means to address barriers within the intensive care unit.18 Studies have proposed that the benefits of upright mobilization include improved bone density, cardiopulmonary function, gastrointestinal motility, reduced pain, and improved functional recovery following stroke.4 A review of the research shows that repeated head-up tilt table use may be effective in the treatment of orthostatic intolerance19 and spasticity.20 The use of a tilt table can maximize the potential for longitudinal weight bearing through the lower extremities in a position of hip extension with concurrent knee extension and ankle dorsiflexion that is not obtained in the seated position. In addition, this position may serve as the basis for future task-specific standing balance and gait training.

A review of the literature reveals limited research regarding potential risks or benefits of using a tilt table specifically to assist patients into a standing position. Korpelainen et al21 examined the response to a tilt table intervention on patients who were 2 to 10 days poststroke. This group found no significant difference in peripheral blood pressure readings after standing at 90° for 7 minutes. Panayiotou et al15 examined hemodynamic responses to an intervention consisting of 5 minutes of sitting followed by 5 minutes of standing in participants 3 to 10 days poststroke. The incidence of intolerance (defined as a drop of systolic blood pressure [SBP] ≥ 20 mmHg) was 3% to 19% for participants poststroke and 8% to 18% for the control group.

Beyond these 2 studies, information on the use of a tilt table as a means to assist patients into a standing position acutely after stroke is lacking. In addition, bed rest within the first 24 hours following stroke continues to be recommended.14 To address this gap in knowledge, we proposed a study to examine the tolerance of a progressive standing tilt table protocol (STTP) designed to facilitate lower extremity weight bearing early after stroke.

The primary aim of this pilot study was to assess the hospitalized patient's physiologic tolerance to standing while on a tilt table following an acute stroke. Furthermore, to determine a clinically applicable STTP, we assessed the tolerance of maximal angle of tilt achieved and associated duration of standing time.

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METHODS

Sample Characteristics

This study was conducted within an adult acute stroke care unit at the University Hospital in Ann Arbor, Michigan. Participants eligible for this study were (1) adults 18 years or older, (2) admitted to the stroke unit, and (3) currently diagnosed with ischemic or hemorrhagic stroke. There were no restrictions of participation based on location or etiology of lesion or severity of clinical deficits. As this pilot study was designed to assess the safety and physiologic tolerance to an STTP and to generalize the results across varying levels of neurologic insult, stroke severity or functional status was not considered to be an inclusion or exclusion criterion as a parameter for this study. Exclusion criteria included (1) strict bed rest orders, (2) tissue plasminogen activator or thrombolytic administration within the prior 24 hours, (3) medical history of recurrent syncope, (4) current lower extremity fractures, and (5) weight exceeding 750 pounds, due to equipment limitations.

Participants were recruited through screening of consecutive admissions between September 1, 2008, and December 31, 2009. The institutional review board of the University of Michigan Medical School approved this study, and written informed consent was obtained from all participants or their proxies.

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Tolerance Parameters

The STTP clinical indices of tolerance were operationally defined as (1) SBP maintained within 20 mmHg of baseline; (2) diastolic blood pressure (DBP) maintained within 10 mmHg of baseline; (3) heart rate (HR) maintained within 10 beats per minute of baseline; (4) oxygen saturation (SpO2) maintained at 90% or more while on supplemental O2 or room air; and (5) clinical observation of dyspnea or pallor. The Marquette Solar 8000-M Telemetry unit (GE Marquette Medical Systems, Inc, Milwaukee, WI) was available in each participant's room to collect SBP, DBP, HR, and SpO2.

Subjective indices of tolerance were operationally defined as (1) rating of perceived exertion ≤15 as measured by the Borg Rating of Perceived Exertion Scale22; (2) pain ≤5 using a numerical pain rating scale ranging from 0 (no pain) to 10 (extreme pain); (3) absence of angina, dizziness, or nausea; and (4) request to discontinue the STTP. When subjective indices of tolerance could not be verbally communicated by a subject because of cognitive or sensorimotor deficits, other clinical signs of distress such as facial grimace, gesturing, or diaphoresis were used.

Because of the exploratory nature of this study, tolerance or lack thereof was defined by multiple measures of both objective clinical indices and subjective report. No single measure was considered to be of primary importance, and any value falling outside the predetermined parameter was considered indicative of intolerance. Overall, the primary outcome of the STTP was defined as the ability to sustain 60° or greater of tilt table inclination for a minimum of 5 minutes, without signs or symptoms of intolerance.

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Standing Tilt Table Protocol

Each participant underwent 1 session of the STTP. Baseline measurements were taken while participants were at rest for a minimum of 10 minutes in the hospital bed, with 30° of head elevation prior to transfer to the tilt table. A tilt table (Tri W-G Motorized Bariatric Tilt Table, Model #TG2732; TRI W-G, Valley City, ND) was used. The specifications included a 750-pound weight capacity, electric hand controller of tilt range 0° to 90°, and safety belts, foot plate, and angle indicator.

The STTP was implemented in the participant's hospital room. The tilt table was positioned parallel to the participant's bed and the height of the bed was adjusted until the 2 surfaces were level with each other. Clinical and subjective indices were assessed prior to transfer (baseline measurement) and at each subsequent angle of inclination. A safety check was performed by observation and adjustment of all indwelling lines to prevent disruption: (1) prior to draw sheet technique transfer to the tilt table and (2) at each subsequent stepwise angle of inclination (see later).

Participants were secured to the tilt table and elevated to 45° for 5 minutes, and clinical and subjective indices for tolerance were assessed at 3 minutes within the 5-minute interval (please see Video, Supplemental Digital Content 2, which demonstrates stepwise progression of the tilt table protocol, available at: http://links.lww.com/JNPT/A36). If signs and symptoms of intolerance (described as previously) were present, participants were returned to a resting position in the hospital bed, vital signs were again assessed, and the nursing staff was notified. Successful completion of 45° elevation resulted in a stepwise progression to 60, 70°, 80°, and 90° for a maximum duration of 20 minutes at or more than 60°, for those participants who demonstrated tolerance. If signs of intolerance were observed at any angle of inclination, the protocol was terminated and participants were returned to a horizontal position at the rate of 3° per second specific to the mechanical properties of the tilt table. The participant was then returned to a recumbent position in bed and vital signs were reassessed.

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Statistical Methods

Analyses included descriptive statistics (mean, standard deviation [SD], and frequency) for sample characteristics, maximum angle achieved, and clinical and subjective intolerance parameters. Chi-square analyses were used to test differences between categorical observed and expected values.

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RESULTS

Study Participants

One hundred fifty-one patients consecutively admitted to the stroke unit were screened for this study. Of the 84 patients who met inclusion criteria, 51 were enrolled in this study, while 33 eligible subjects declined to give informed consent. Of those enrolled, 38 participants participated in the STTP. Those who were enrolled but did not complete the study were discharged prior to participation (N = 11), withdrew consent (N = 1), or experienced a change in medical status (N = 1) before the initiation of the STTP. Two participants were initially diagnosed as having a stroke and underwent the STTP. Their diagnoses were later revised and therefore these data were excluded; therefore, data from 36 participants with stroke were included.

The average age of study participants was 61.72 (SD = 16, range = 24–81) years. Twenty-two of the participants (61%) were women, and 25 of 36 of the strokes (69%) were ischemic. A retrospective discharge summary review indicated that 18 participants had a stroke in the cerebrum, 2 in the cerebellum, 13 in the brainstem, and 3 were unknown. The average length of stay was 7 (SD = 5) days and 19 participants (53%) were discharged to home. Seventeen participants (47%) were transferred to acute or subacute rehabilitation care.

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Maximum Angle Achieved

Nineteen participants (53%) were able to maintain 60° or more of tilt for at least 5 minutes without signs or symptoms of intolerance as operationally defined by this protocol as illustrated in Table 1. There were no significant differences in maximum angle achieved between those diagnosed with ischemic or hemorrhagic stroke (χ2 = 0.00, P = 0.983). Ten participants were unable to tolerate standing at a 45° angle.

Table 1
Table 1
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Clinical and Subjective Indices of Tolerance

Angina, dyspnea, SpO2, and pallor did not exceed thresholds outside the protocol parameters for participants at any angle as indicated in Table 2. The most frequent reason for terminating a trial was SBP and DBP variation outside the STTP parameters. This was consistent across all angles. At 45° and 60° of inclination, 1 participant and 2 participants, respectively, experienced an HR change outside the parameters of the protocol, while subjective indices of dizziness and nausea were both infrequently and inconsistently reported at 45°, 60°, and 80°.

Table 2
Table 2
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Time from Admission to Implementation of STTP

There was not a significant relationship between tolerance of the STTP greater than 60° and the time between admission to the unit (categorized as < 24 hours, 24–48 hours, 48–72 hours, and >72 hours) and initiating the STTP (χ2 = 5.964, P = 0.113). There appeared to be some advantages in waiting 24 hours after admission before implementing the protocol, as 1 out of 7 of those participants tested prior to this time were intolerant. This result should be interpreted cautiously without replication. It should also be noted that time of admission does not necessarily indicate time of onset of stroke, as there can be large time lapse from symptom onset to hospital admission.

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DISCUSSION

This pilot study shows that the majority of patients with acute stroke in our sample demonstrated physiologic, clinical, and subjective tolerance to an STTP intervention. Fifty-three percent of subjects attained 60° or higher, with a mean total standing time of 8.9 minutes. The most common factor for terminating a trial at any angle was exceeding the allowable DBP parameters.

In comparison to the use of a tilt table to assess physiologic response to upright activity following stroke, Panayiotou et al15 examined hemodynamic responses to an intervention of 5 minutes of sitting followed by 5 minutes of standing in participants 3 to 10 days following admission after stroke. The incidence of intolerance (defined as a drop of SBP ≥20 mmHg) was 3% to 19% for participants poststroke and 8% to 18% for the control group. The discrepancy between the 2 studies may be explained by the inclusion in our study of multiple variables to define tolerance. In this study, if intolerance was defined solely as a drop of SBP greater than or equal to 20 mmHg, and not by the addition of other factors such as DBP or HR, the incidence of intolerance would have been 22.2% rather than 47%.

Korpelainen et al21 examined the response to a tilt table intervention in patients who were 2 to 10 days poststroke. This group found no significant difference in peripheral blood pressure readings after standing at 90° for 7 minutes. These researchers used a “quick passive tilting” method to achieve 90° of tilt within a 2-second period. The current study used a stepwise progression of tilt, which may explain the difference in findings between the 2 studies.

The results of this study differ from the A Very Early Rehabilitation Trial for Stroke (AVERT) clinical trial, where participants were able to tolerate VEM within the first 24 hours following a stroke.9 The Avert trial and the current study differ when comparing modes of mobilization and definition of tolerance. The AVERT trial consider mobility both sitting up in a bed and sitting up in a chair and do not necessarily require upright standing, weight-bearing postures for the definition of mobility to be satisfied. In addition, the AVERT trial used a decrease of 30 mmHg or more in SBP as a cutoff measure to terminate a particular trial. The parameters of this study utilized a decrease of 20 mmHg or more in SBP, as taken from the consensus statement from the American Autonomic Society and the American Academy of Neurology.23

When physiologic tolerances were monitored, DBP falling more than 10 mmHg was the main limiting factor to progression of the STTP. A second limiting factor was SBP falling outside of the 20 mmHg parameter. For all participants, the remaining physiologic indices (RR, SpO2, rating of perceived exertion), subjective report, and observational indices fell within our definition of tolerance. Each clinical index was rated with equal importance; therefore, if any one of the indices was found to be outside the established parameters, the STTP was terminated. It is important to note within standard clinical practice that both subjective and objective measures are coupled with clinical judgment to assess tolerance to progressive or ongoing interventions.

Finally, the researchers expected that initiating the STTP within 24 hours of admission could be tolerated by a majority of the subjects. Of the 7 participants who received the protocol within 24 hours, only one (14%) in this study was able to tolerate standing during the STTP when initiated within 24 hours of admission (see Figure 1). While there appeared to be some advantages to waiting until 24 hours following admission before implementing the protocol, this finding should be interpreted cautiously without further replication of results. As noted previously, time of admission does not necessarily indicate time of onset of stroke, as there can be a large time lapse from symptom onset to hospital admission.

Figure 1
Figure 1
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LIMITATIONS

The limitations of this study include a small sample size and no control for level of function or severity of stroke. Because of this small sample, we did not have sufficient power to test various predictors of tolerance in addition to the type of stroke and age. In addition, a single-session protocol limited the ability to monitor changes in tolerance over time. In this study, the duration of time on the tilt table greater than 60° was not studied as an independent variable, but rather was a function of the maximal angle achieved. That is, tolerance was dependent on achievement of 5 minutes at a specified angle. To develop clinical guidelines for use in a tilt table intervention, maximal time tolerated at each predetermined angle should be studied further.

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CONCLUSIONS

Risks from prolonged bed rest during hospitalization have been documented to adversely affect multiple organ systems, impede functional recovery, and increase the risk of mortality and morbidity. This pilot study was designed to standardize a safe and feasible clinical intervention in an effort to increase the frequency of patient mobilization into a prolonged standing position following acute onset of stroke. The preliminary data suggest that the use of the STTP during physical therapy after stroke is likely to be a safe, feasible, and functionally relevant approach to initiate early mobilization for medically fragile patients.

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ACKNOWLEDGMENTS

We thank Katie Bower; Andrea Junga, PTA; Andrew Deneen; Amber Ward, DPT; and Autumn Neuharth for all their assistance with data collection and video production.

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REFERENCES

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early mobilization; stroke; tilt table

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