Abstract
Objectives
To determine caregiver burden and quality of life of primary family caregivers of participants with cervical SCI before and after use of the cough stimulation system (CSS).
Design
Prospective assessment at four timepoints via questionnaire responses.
Setting
Out-patient hospital, United States.
Participants
15 primary family caregivers of participants with cervical SCI completed questionnaires including a respiratory care burden index (n = 15) and a commonly employed caregiver burden inventory (n = 9), before and at the 6-month, 1-year and 2-year timepoints following use of the CSS.
Results
SCI participants had significant clinical improvements in terms of restoration of an effective cough and ability to manage airway secretions with use of the CSS. Restoration of expiratory muscle function with use of the CSS also resulted in less caregivers (CG) stress, greater control of their participants’ breathing problems, and improvement in quality of life. Results of the caregiver burden inventory demonstrated marked reductions in caregiver burden in development items, physical health and social relationship. Overall caregiver burden fell from 43.4 ± 13.8 pre-implant to 32.4 ± 7.9 (P = 0.06), 31.7 ± 10.5 (P = 0.05), and 26.5 ± 9.3 (P = 0.01) at the 6-month, 1-year and 2-year timepoints.
Conclusion
Use of the CSS by cervical SCI participants results in restoration of an effective cough with significant clinical benefits. While caregiver burden is very high in primary family caregivers, they derive marked improvement in caregiver burden and quality of life with implementation of this device.
Trial registration: ClinicalTrials.gov identifier: NCT00116337.
Trial registration: ClinicalTrials.gov identifier: NCT01659541.
Keywords: Caregiver burden, Spinal cord injury, Spinal cord stimulation, Cough
Introduction
The impact of cervical spinal cord injury (SCI) on the individual affected is usually quite devastating as these individuals suffer from severe motor and sensory deficits resulting in severe mobility impairments. In addition, their plight is compounded by autonomic deficits including bowel, bladder and sexual dysfunction, respiratory and genitourinary infections, chronic pain, skin breakdown and psychological disorders. Also, critically important but given much less emphasis, is the loss of respiratory muscle function, resulting in dyspnea and the inability of these individuals to generate an effective cough.
Following discharge from the acute hospital setting or from a rehabilitation center, individuals with SCI are often cared for at home by family members. These family caregivers (CGs), however, are often untrained and unprepared to undertake the multiple needs of SCI individuals. Despite being the primary interface with the health care system, CGs often receive inadequate support from health care professionals and frequently feel abandoned and unrecognized (1). As they are frequently overlooked by clinicians, the CG becomes the invisible individuals and often has significant health and psychosocial needs that, in turn, affect the quality of caregiving and have the potential to negatively impact the physical and mental health of SCI individuals (1, 2). Consequently, caregiving of SCI individuals often imposes a multi-dimensional toll and significant burden on the CG. In this regard, previous investigators have provided a useful definition, describing caregiver burden (CB) as the extent to which CGs perceive that providing care has negatively impacted their emotional, social, financial, physical and/or spiritual functioning (3).
A number of previous studies have investigated and quantified CB and quality of life of primary family CGs involved in the care of SCI individuals. Unfortunately, interventions aimed at mediating CB have been largely ineffective (4). The potential impact of restoration of a portion of the individual’s physical function on CB however has not been evaluated. In the present study, we hypothesized that restoration of expiratory muscle function and restoration of an effective cough via the cough stimulation system (CSS) which has been shown to improve respiratory secretion management, reduce the incidence of respiratory tract infections and improve participant quality of life (5–7), would also impart a significant improvement in CB and quality of life of the family CG.
Methods
This investigation was approved by the MetroHealth Institutional Review Board, the National Institute of Neurological Disorders and Stroke and the Food and Drug Administration.
Informed consent was obtained from each participant prior to study enrollment. Each of the study participants had suffered from a traumatic cervical SCI (with the exception of one whose injury was secondary to infection) which resulted in significant expiratory muscle weakness and difficulty managing respiratory secretions. Maximum expiratory pressures (MEP) were measured in each participant at total lung capacity (TLC) confirming expiratory muscle weakness (<40% of normal predicted values). None of the study participants had significant lung, cardiac or brain disease as these conditions excluded individuals from participation in this study.
Each participant underwent implantation of the CSS which involved one of two different methods (8). In an initial group (n = 17), participants underwent placement of disc electrodes (5, 6, 9–11). In a second group (n = 12) wire electrodes were utilized (7, 12, 13). Briefly, disc electrodes (4 mm) (Freehand Epimysial Electrode; NeuroControl Corp., Valley View, OH, USA) were placed at the T9, T11 and L1 levels via hemilaminotomy incisions. Use of wire electrodes involved placement of two parallel wire leads (Ardiem Medical, Inc. Indiana, PA, USA) on the dorsal epidural surface of the spinal cord. using minimally invasive techniques. Via a small incision at the L1 and L2 level, the cephalad electrode of each lead was positioned at the T9 spinal level which resulted in a more caudal electrode of each lead positioned in the vicinity of the T11 spinal level. With both the disc and wire electrode methods, the electrode wires were tunneled subcutaneously and connected to a radiofrequency receiver (Finetech Medical LTd., Wewyn Gardden City, Herfordshire, UK) which was positioned in a subcutaneous pocket over the anterior portion of the chest wall. Descriptions of these methods are provided in greater detail in other publications (10, 13).
Each participant was instructed to apply stimulation every 30 s for 5–10 min, 2–3 times per day. Each participant was also instructed to use the device when needed for evacuation of airway secretions or foreign bodies.
Each of the participants was followed at monthly intervals for the first 6 months and subsequently at 3-month intervals for the next 6 months and again at the 2-year timepoint post implantation. In the seated posture, maximal expiratory pressures were monitored under conditions of airway occlusion at FRC and TLC to evaluate the efficacy of the CSS from a physiological standpoint (9). Measurements were made with use of a tight-fitting full-face mask. During the period of stimulation, participants were instructed to relax completely. In instances of participant effort, evidence of glottic closure, or obvious mask leakage, data were discarded (9). Clinical assessments of the CSS in terms of cough efficacy were also obtained throughout the study via a series of questionnaires.
Airway pressure generation was assessed using a BIOPAC Data Acquisition and Analysis System (Biopac System Inc, 42 Aero Camino, CA, USA) with AcquKnowledge software, MP 150 system with TSD 160C pressure transducer. Further details of this measurement can also be found in previous publications (6–10, 12, 13).
The incidence of acute respiratory tract infections, defined by a change in the character, color, or amount of respiratory secretions and requiring antibiotic administration was tracked over the 2-year period prior to implantation of the CSS. The occurrence of respiratory tract infections was determined by participant history and corroborated by review of medical records, when available. After implantation of the cough system, the incidence of acute respiratory tract infections was documented.
Six of the 17 participants who underwent implantation of the disc and, 9 of the 12 participants who had implantation of the wire electrode leads had family members as their primary CG (n = 15). The remaining participants were either nursing home residents or had non-family CG and therefore were excluded from this analysis. The CG were divided to cohort #1 (n = 15) for a family CG of individuals implanted with either disc or wire electrodes and completed the Secretion Management Assessment and the Respiratory Care Burden Index (Questionnaire A) while cohort #2 (n = 9) completed these same forms but also completed the Caregiver Burden Inventory (Questionnaire B) of individuals implanted with wire electrodes. Participants in Cohort #2 were included in Cohort #1.
Since a CB index which specifically addresses respiratory issues, with an emphasis on secretion management in the SCI population, does not exist, a list of ten questions was assembled with a focus on these concerns (Respiratory Care Burden Index, Questionnaire A, Fig. 3) (4, 14–17).
Figure 3.
Questionnaire A, Respiratory Care Burden Index (see text for further explanation).
A commonly used caregiver inventory (CBI) (18), previously employed in individuals with SCI and many other disorders (19–25) was also incorporated into our study protocol involving implantation of the CSS with wire electrodes. This questionnaire (Questionnaire B) was completed by nine participants (cohort #2).
Data analysis
Statistical analyses were carried out using the SigmaPlot for Windows program (version 14.0.0.124) and R, Version 4.1.3, including functions from the nlme and emmeans packages.
Data obtained prior to implantation were compared with data obtained after implantation of the cough system using a nonparametric analog (Dunnett test) to the standard repeated measures analysis of variance. The internal consistency of the CB index was assessed by Cronbach’s α coefficient (15, 26, 27). A value of 0.70 and above was considered satisfactory. The Respiratory Care Burden index was measured repeatedly over time without missingness was analyzed using repeated-measures ANOVA to assess differences in responses over the four assessed times: pre-implant, 6 months, 1 year, and two years. Because there were some missing values in the repeated measures of the CBI, a linear mixed-effects model was estimated to compare responses over time while adjusting for repeated measures within the subject. When an overall effect of time was detected using an F-test from either approach, Tukey-adjusted pairwise post hoc tests were implemented to compare specific timepoints (26). Continuous outcomes were summarized as means ± SD. Statistical significance was assumed at P ≤ 0.05.
Results
Baseline demographic data of the 15 participants who participated in this study are provided in Table 1. The interval between the date of injury and participation in this trial ranged between 1 and 47 years (7 ± 11 years). At the time of enrollment, vital capacity measurements ranged from 7 to 73% predicted value (mean 31 ± 19%). Each participant had marked respiratory muscle weakness as reflected in maximum expiratory pressure measurements, which ranged from 1 to 25% predicted (mean 12 ± 6%). All of the caregivers were female; five were mothers, eight were spouses, one was a girlfriend and one a sister of the participants.
Table 1.
Clinical data of the participants.
| Participant | Sex | Age at implantation (y) | Cause of injury | Level of injury | ASIA | Elapsed time since injury (y) | Spontaneous vital capacity (L) (% predicted) | Maximal expiratory pressure (cmH2O) (% predicted) | Caregiver | ||
|---|---|---|---|---|---|---|---|---|---|---|---|
| Relationship | Sex | Age | |||||||||
| Disc electrode leads study | |||||||||||
| 1 | M | 23 | Diving | C4-C5 | A | 1 | 0.9 (17) | 24 (11) | Mother | F | 54 |
| 2 | M | 61 | Fall | C2 | A | 4 | 0.3 (7) | 3(1) | Wife | F | 58 |
| 3 | M | 34 | Diving | C3 | A | 1 | 1.4 (24) | 45 (15) | Mother | F | 62 |
| 4 | F | 20 | MVA | C3 | A | 3 | 1.3 (34) | 35 (16) | Mother | F | 39 |
| 5 | M | 45 | GSW | C4 | A | 3 | 1.2 (19) | 15 (5) | Sister | F | 48 |
| 6 | M | 64 | MVA | C5-C6 | A | 47 | 1.1 (25) | 36 (18) | Wife | F | 57 |
| Wire leads study | |||||||||||
| 7 | M | 50 | GSW | C4 | A | 2 | 1.2 (28) | 20 (9) | Wife | F | 30 |
| 8 | M | 27 | Fall | C3-C4 | A | 5 | 1.6 (27) | 18 (8) | Mother | F | 56 |
| 9 | M | 28 | Fall | C2 | A | 9 | 1.6 (26) | 41 (18) | Mother | F | 55 |
| 10 | M | 48 | MVA | C1-C4 | A | 9 | 0.4 (7) | 4 (2) | Wife | F | 44 |
| 11 | M | 58 | MVA | C5-C7 | A | 4 | 2.2 (51) | 29 (14) | Girlfriend | F | 47 |
| 12 | M | 50 | Equipment accident | C4-C6 | A | 3 | 3.4 (67) | 59 (25) | Wife | F | 50 |
| 13 | M | 36 | Infection/abscess | C3-C6 | A | 3 | 1.8 (31) | 21 (9) | Wife | F | 43 |
| 14 | M | 35 | Fall | C6 | A | 4 | 3.5 (73) | 21 (9) | Wife | F | 24 |
| 15 | M | 30 | Diving | C3 | A | 2 | 1.5 (35) | 33 (14) | Wife | F | 28 |
| Mean | 41 | 7 | 1.6 (31) | 27 (12) | 46 | ||||||
| SD | 14 | 11 | 0.9 (19) | 15 (7) | 12 | ||||||
ASIA, American Spinal Cord Injury impairment scale; M, Male; MVA – Motor Vehicle Accident; GSW – Gunshot Wound; F – Female.
As shown in Fig. 1A, mean maximum expiratory pressure generation (MEP) during voluntary efforts pre-implantation was 27 ± 15 cmH2O for cohort #1. While using the CSS, MEP values at TLC with participant effort for cohort #1 were 101 ± 43, 106 ± 55 and 110 ± 51 cmH2O at the 6-month, 1- and 2-year follow-up timepoints (P = 0.01, for each when compared to voluntary efforts). There were no significant differences between MEP measurements at the 6-month, 1- and 2-year timepoints (P = 0.80, P = 0.59, P = 0.60, P = 0.99, respectively). There were also no significant differences between cohorts #1 and #2 pre-implant and at each of the follow-up timepoints (P = 0.91, P = 0.47, P = 0.83, P = 0.99 for Pre-Implant, 6-month, 1- and 2-year timepoints, respectively).
Figure 1.
(A) Airway pressure generation at total lung capacity (TLC) before and at 6 months, 1 year and 2 years following use of the Cough System. There were marked improvements in airway pressure generation in cohorts 1 and 2 (black and gray bars, respectively) (P = 0.01 for each compared to pre-implant values). There were no significant differences between cohorts. (B) There was a marked reduction in the incidence of acute respiratory tract infections following use of the cough stimulation system from 1.63 ± 2.05 events/year for cohort #1 (black bar) and 1.89 ± 2.47 events/year for cohort #2 (gray bar) to 0.04 ± 0.13 events/year and 0.11 ± 0.33 events/year, respectively (P = 0.01). This improvement was maintained at the 1- and 2-year year follow-up assessments for both cohorts (P = 0.01 compared with pre-implant values).
The incidence of respiratory tract infections also fell significantly at each of the measured timepoints compared to pre-implant values from 1.63 ± 2.05–0.03 ± 0.13 at the 6-month, and 0.03 ± 0.13 at 1- and 0.07 ± 0.26 events/participant year at 2-year timepoints for cohort #1 (P = 0.007, P = 0.005, P = 0.007 when compared to 6-month, 1-year and 2-year timepoints, respectively). There were no significant differences between cohorts #1 and #2 pre-implant and at each of the follow-up timepoints (P = 0.79, P = 0.72, P = 0.72, P = 0.72 for Pre-Implant, 6-month, 1- and 2-year timepoints, respectively) (Fig. 1B).
The mean results of the measures of secretion management are provided in Fig. 2 (A–D). Significant improvements were observed in each of these parameters which included secretion management frequency, secretion management episodes, difficulty raising sputum and ease in raising sputum at the 6-month timepoint and maintained at the 1- and 2-year timepoints (P = 0.01 for each comparison when compared to pre-implant values). Moreover, most participants reported that they relied on the CSS as their only method of secretion management. There were no significant differences between cohorts #1 and #2 pre-implant and at each of the follow-up timepoints.
Figure 2.
Participant responses to frequency of need for conventional means of secretion clearance, severity of such episodes, difficulty in raising secretions and change in ease in raising secretions using the cough stimulation system compared with previous methods for cohorts #1 and #2 (black and gray bars, respectively). Compared to pre-implant, there were significant improvements in all parameters of secretion management at 6-months, 1-year and 2-year follow-up (P = 0.01 for each compared to pre-implant values). There were no significant differences between cohorts.
Respiratory Care Burden index (Questionnaire A) responses related to CB and quality of life for CGs of cohort #1 are provided in Fig. 3. In terms of CG stress related to managing airway secretions (question #1), there were reductions in stress at each of the measured timepoints but statistically significant only at the 2-year timepoint. compared to pre-implant values. Caregivers also felt more in control of their participant’s breathing problems (question #4) at the 1- and 2-year timepoints (P = 0.03 and P = 0.01, respectively). There were also significant reductions in caregiver sense of fear or panic when providing care (question #5) (P = 0.01 and P = 0.01 at the 6-month and 2-year timepoints, respectively). While there was a trend toward reduction in interference with social activities (question #6), but these differences also did not reach statistical significance. There was also a trend toward reduction in care responsibilities interfering with family life (question #7) but not statistically significant. There was significant improvement in caregiver personal life (question #8) which was statistically significant at the 2-year timepoint (P = 0.01). In terms of experiencing financial difficulties (question #9), there was a trend toward improvement, but these differences were not statistically significant. Finally, there were significant improvements in the perception of overall quality of life (question #10) at the 2-year timepoint (P = 0.03).
The responses to the CBI (Questionnaire B) for cohort #2 are provided in Table 2. The overall level of burden pre-implant of the CSS was 43.4 ± 13.8 with a significant effect of time detected (F-test P-value = 0.004). We observed a significant reduction in overall burden at the 1-year (31.6 ± 10.5, P = 0.05) and 2-year timepoints (26.4 ± 9.3, P = 0.01) relative to pre-implant values. There were no significant differences between any of the follow-up timepoints (P = 0.99, P = 0.52, P = 0.62 for comparison between 6-month and 1-year; 6-month and 2-years; 1-year and 2-year timepoints, respectively). Looking at grouped items within the CBI, we observed significant overall time effects in development at the 1-year and 2-year timepoints, (P = 0.05 and P = 0.01, respectively), physical health at the 6-month (P = 0.02), 1-year (P = 0.02) and 2-year (P = 0.01) timepoints, and social relationship at the 2-year timepoint (P = 0.05) dimensions.
Table 2.
Questionnaire B, responses to the Caregiver Burden Inventory (cohort #2; n = 9).
| Possible score | Pre-implant | 6-month | 1-year | 2-years | ||
|---|---|---|---|---|---|---|
| Time dependency items | ||||||
| Needs my help to perform many daily tasks | 0–20 | Score F-test P = 0.078 |
17.42 ± 1.42 | 16.56 ± 1.01 | 15.6 ± 3.28 | 14.1 ± 4.55 |
| Care receiver is dependent on me | ||||||
| Have to watch my care receiver constantly | ||||||
| Have to help my care receiver with many basic functions | ||||||
| I don’t have a minute’s break from my caregiving chores | ||||||
| Development items | ||||||
| I feel that I am missing out on life | 0–20 | Score F-test P = 0.015 |
10.78 ± 5.09 | 7.56 ± 4.10 P* = 0.15 |
6.78 ± 4.23 P* = 0.05 |
5.89 ± 4.01 P* = 0.01 |
| I wish I could escape from this situation | ||||||
| My social life has suffered | ||||||
| I feel emotionally drained due to caring for my care receiver | ||||||
| I expected that things would be different at this point in my life | ||||||
| Physical health items | ||||||
| I’m not getting enough sleep | 0–20 | Score F-test P = 0.001 |
8.67 ± 3.20 | 5.33 ± 3.12 P* = 0.02 |
5.33 ± 3.16 P* = 0.02 |
4.00 ± 3.32 P* < 0.01 |
| My health has suffered | ||||||
| Caregiving has made me physically sick | ||||||
| I’m physically tired | ||||||
| Social relationship items | ||||||
| I don’t get along with other family members as well as I used to | 0–20 | Score F-test P = 0.047 |
4.44 ± 3.97 | 1.89 ± 1.83 P* = 0.08 |
2.78 ± 2.81 P* = 0.37 |
1.67 ± 1.32 P* = 0.05 |
| My caregiving efforts aren’t appreciated by others in my family | ||||||
| I’ve had problems with my marriage | ||||||
| I don’t get along as well as I used to with others | ||||||
| I feel resentful of other relatives who could but do not help | ||||||
| Emotional health items | ||||||
| I feel embarrassed over my care receiver’s behavior | 0–20 | Score F-test P = 0.202 |
2.00 ± 2.78 | 0.89 ± 1.05 | 1.00 ± 1.32 | 0.67 ± 1.12 |
| I feel ashamed of my care receiver | ||||||
| I resent my care receiver | ||||||
| I feel uncomfortable when I have friends over | ||||||
| I feel angry about my interactions with my care receiver | ||||||
| Total score | ||||||
| 0–96 | Score F-test P = 0.004 |
43.3 ± 12.8 | 32.2 ± 7.9 P* = 0.06 |
31.5 ± 10.5 P* = 0.05 |
26.4 ± 9.3 P* < 0.01 |
|
| Total Crombach's α | ||||||
| α | 0.92 | 0.81 | 0.87 | 0.83 | ||
*Post-hoc pairwise tests performed if significant effect of time detected, Tukey-adjusted P for given time compared to pre-implant presented.
The CBI had a high degree of internal consistency as reflected by Cronbach α scores which ranged between 0.81 and 0.92.
Discussion
While there have been multiple investigations evaluating CB in the care of SCI individuals (15, 16, 28–32), this study is unique in that it evaluates the impact of respiratory issues and use of the CSS on caregiver burden and quality of life. Moreover, this evaluation took place at multiple timepoints over an extended period. Indeed, this is the first study to demonstrate that restoration of expiratory muscle function and development of an effective cough results in less CG stress, greater control of the person with SCI’s breathing problems and less fear or panic when providing care. Use of the CSS was also associated with significantly greater CG satisfaction with their own personal life and overall quality of life. The high pre-implant CBI also improved significantly following use of the CSS at the 1-year and 2-year timepoints. These improvements are not entirely surprising given the fact that CG support for secretion clearance and incidence of respiratory tract infections was dramatically reduced.
While the focus of this study was on the effects of restoration of an effective cough on CB, it is possible that some of the improvements were secondary to other beneficial effects of restoration of expiratory muscle function. For example, in a recent analysis of five participants who underwent CSS implantation, there was a dramatic improvement in bowel management (BM) with BM times reduced from more than 2 h to ∼ 20 min (33, 34). Prior to this analysis, several other participants also reported subjective improvements in BM. The reduction in time required for BM likely increased the time available for social and recreational activities. In other analyses (7), we also demonstrated that there was an improvement in pulmonary function and participants noted less dyspnea associated with use of the CSS which may have reduced CG level of stress, as well.
Caregiver burden was found to be very high initially in this study as reflected in the high CBI score of 43.4 ± 12.8 at the pre-implant timepoint. Interestingly, this finding is consistent with other investigations of CB of CGs for people with SCI, utilizing the same or similar index, which found total scores of 41.05–47.6 (14–16, 27). Moreover, these other studies also found that the time dependent and development dimensions reflected the highest burden whereas, social and emotional dimensions had the lower scores. Also consistent with other studies (15, 27), the CBI Cronbach’s ɑ scores were very high indicating a high degree of internal consistency. In the present study, the Cronbach α score was 0.8 or higher for each of the CBI dimensions, exceeding the typical standard of 0.70 for significant reliability.
In a comprehensive literature review of the impact of SCI on the quality of life of family CGs, Lynch and Cahalan (17) found that SCI had significant effects on CG quality of life, impacting physical, mental and social aspects of their health. Specific negative consequences included physical pain as well as anxiety and depression. Moreover, these effects were corroborated by studies performed not only in the United States but worldwide (17). Recommendations have been made to improve CG health but universally agreed upon approaches have not been established.
While comprehensive, validated instruments of CG quality of life were not administered in this study, the degree of CB has been shown to be highly predictive of CG quality of life. This relationship has been demonstrated in individuals with dementia (35), neurocognitive disorders (36), stroke (37), and recently in CGs of individuals with SCI, as well (38). Based upon these studies, it is reasonable to infer that the high CB observed in this study had a significant negative impact on CG quality of life. It is also likely, in turn, that the reduction in CB with use of the CSS significantly improved CG quality of life. This inference is corroborated by the responses to the questionnaire of cohort #1 in which CGs indicated that their overall quality of life improved following implementation of the CSS.
Based upon the current investigation and previous studies (5–13, 33, 34) therefore, our results suggest that restoration of expiratory muscle function can significantly improve caregiver QOL of individuals with SCI and their CGs, as well. Interestingly, in another study (39), in which inspiratory muscle function was restored via diaphragm pacing (which replaced mechanical ventilation in ventilator dependent tetraplegics), individuals quality of life improved significantly by improving mobility, likelihood of employment, sense of smell, improved sense of normal breathing and lack of connection to a mechanical ventilator. Although not systematically studied, it appears likely that individual improvement in QOL secondary to restoration of inspiratory muscle function, imparted some improvement on the burden of caregiving for these persons with SCI, as well.
The inclusion criteria for participants of CG analyses in this study was limited to family CGs. Therefore, participants who underwent implantation of the CSS were excluded (n = 14). One concern therefore was that study participation may have been skewed to individuals who had differential physiologic and/or clinical benefits of the CSS which would have secondarily impacted CB. The benefits reported herein however were not significantly different than that previously reported for the entire study population (5–13) nor were there any significant differences between cohorts (Figs. 1 and 2). Stated differently, the physiologic and clinical benefits were the same between each of the groups studied. Therefore, the analyses of CB were not likely impacted by any inadvertent selection biases.
While there were marked improvements several dimensions of CB index following restoration of expiratory muscle function, not surprisingly the overall score remained high given the multiple needs of tetraplegic individuals. In particular, the time dependency burden remained quite elevated. Use of modalities such as the CSS, therefore, does not negate the need to address other measures to ease the level of CB in the care of SCI participants. Specific interventions that reduce CB need to be designed and carefully assessed to enhance improvement of CG well-being including computer technology and support groups, educational sessions and particularly problem-solving training which have been reported to have some impact on CB (4, 15, 17, 38, 40, 41).
While the sample size is a limitation of the present study, the results are bolstered by the uniformity of responses of the baseline CB inventory and responses to specific dimensions, across multiple other investigations, even those involving different cultures (4, 15, 16, 27, 38). While the elapsed time from onset of injury ranged between 1 and 47 years, it is not likely that this was a significant issue since CB of SCI participants tends to remain quite stable over time (28). Another potentially important factor, which was not evaluated, is the dependency level of participants with SCI. In this regard, there was some uniformity in that all participants were tetraplegics (AIS A) and likely had similar levels of dependency. The general health of the CGs was also not assessed, which may have significantly impacted CGs perception of CB. In fact, there was a wide variation in CG age, ranging between 24 and 62 years of age and higher age is a risk factor for high CB (27). Our limited sample size and potential confounding factors, therefore, limits the generalizability of our findings across the spectrum of family CGs of participants with SCI.
In summary, use of the CSS imparts significant physiologic and clinical benefits to participants with cervical SCI. Restoration of expiratory muscle function in these participants also results in a significant reduction in the high CB of caregivers of participants with SCI. Consequently, use of the CSS can be looked upon as a means to relieve CB and improve their quality of life. Moreover, since the level of CB influences the quality of care delivered to SCI participants (2), the improvements in CB observed in this study may secondarily improve recipients of care, as well.
Acknowledgements
The authors gratefully acknowledge the surgical assistance of Dr. Kutaiba Tabbaa, MD and statisticians Brigid Wilson, PhD and Charles Thomas, B.A.
Disclaimer statements
Conflicts of interest Dr. DiMarco holds two United States Patents for technology related to the content of this paper: Method and Apparatus for Electrical Activation of the Expiratory Muscles to Restore Cough (5,999,855); Bipolar Spinal Cord Stimulation to Activate the Expiratory Muscles to Restore Cough (8,751,004). This investigation was approved by the Institutional Review Board of MetroHealth Medical Center (IRB98-00091 and RB15-00014).
Funding This work was supported by the National Institute of Neurological Disorders and Stroke (R01 NS049516 and U01 NS083696), Neilson Foundation (278855), NCRR (M01RR000080 and UL1RR024989).
Clinicaltrials.gov identifier NCT00116337, NCT01659541, FDA IDE: G980267.
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