Exploring the Effects of Power Mobility Training on Parents of Exploratory Power Mobility Learners: A Multiple-Baseline Single-Subject Research Design Study

Abstract

Purpose: This study investigated the effects of power mobility training provided to exploratory power mobility learners with cerebral palsy (CP; Gross Motor Function Classification System Level V) on (1) parenting stress, (2) parents’ perceptions of their children, and (3) children’s attainment of power mobility skills. Method: A non-concurrent, multiple-baseline A–B single-subject research design study was conducted with three participants. The target behaviour was changes in the magnitude of parenting stress as measured by the Parenting Stress Index–Short Form. Parents’ perceptions of their children were assessed using the Caregiver Priorities and Child Health Index of Life with Disabilities Questionnaire and a parent interview. Children’s attainment of power mobility skills was assessed using the Canadian Occupational Performance Measure (COPM), the Assessment of Learning Powered mobility use, and the Wheelchair Skills Checklist. Power mobility training was provided twice a week for 8 weeks using an alternative power mobility device. Results: Positive and negative changes in both magnitude of parenting stress and parents’ perceptions were identified post-intervention. All participants gained power mobility skills, assessed with the COPM. Conclusions: Power mobility training provided to exploratory power mobility learners with CP may influence levels of parenting stress.

A systematic review of research with children with mobility limitations who use power mobility devices has shown that power mobility positively influenced children’s development, independence, and participation,¹ thereby increasing their degree of personal control and autonomy and enabling them to engage in meaningful life experiences.² Despite such overwhelming evidence of the possible benefits, however, parents often have mixed emotions or are conflicted about their children’s use of power mobility.^2–4 They frequently have negative reactions to the cost, size, transportation, and storage of power mobility devices, as well as safety concerns, when they initially consider purchasing these devices for their children.^2–4 However, these devices can actually decrease the burden of caring for children who have mobility limitations and can improve parents’ perceptions of their children’s quality of life.^5,6

Parenting stress occurs as a parent attempts to adapt to and cope with the demands of parenting a child.⁷ High levels of parenting stress have been associated with low parenting satisfaction and decreased parental, especially maternal, well-being.^8,9 Although all parents experience parenting stress, parenting children with severe disabilities often creates greater parenting stress than parenting a child who is typically developing.^10–12 Both child-related and parent-related factors influence the degree of parenting stress experienced by a parent of a child with a disability.^13–18 Child-related factors can include the extent of the required care demands,¹⁴ as well as the child’s lack of independence,¹⁵ communication difficulties,^10,13 intellectual impairments,^13,16 and behavioural issues.^14,15 Parent-related factors can include self-perceived incompetence as a parent,¹⁷ poor self-esteem,¹⁸ and the use of passive parenting techniques.¹⁰ The ways in which parents attempt to cope with increased parenting stress can negatively shape their parenting behaviours, ultimately leading to even greater parenting stress.¹⁷

Power mobility use has been associated with decreased parenting stress in parents of young children with mobility limitations. Huang and Chen and Huang and colleagues found that power mobility training (provided using modified battery-operated toy cars in a hospital-based outpatient setting) significantly lowered the level of parenting stress in parents of young children with mobility limitations.^19,20 The authors of these two studies postulated that involving parents in power mobility sessions provided a unique opportunity for them to play and interact with their children and to see them being successful in learning the challenging task of using a power mobility device.^19,20 These opportunities might have positively influenced the quality of parent–child interactions and improved parents’ perceptions of their children’s abilities, thereby positively influencing the parent–child dyad and possibly further decreasing the magnitude of parenting stress.^13,19,20

Other studies have indicated that parents initially have a negative view of power mobility and see a power mobility device as a physical symbol of their children’s inability to walk.^2–5 Parents have also reported that having a child who is learning to use a power mobility device often creates feelings of uncertainty, worry, and loss of control.⁴ Despite these initial concerns, parents often come to view power mobility as a positive influence on their children’s function, independence, and participation.^2–5 Additional research has further supported the notion that power mobility use may positively affect how parents (and others) perceive children with mobility limitations: many parents report changes in their perceptions of their children’s autonomy, independence, and overall abilities.^{2–4,6,21,22}

To date, a majority of the research exploring the influence of children’s power mobility use on their parents has focused on functional power mobility learners who have regular access to a power wheelchair in home and community settings.^1,2,5,6,23 These studies have found that such learners learn power mobility skills quickly and easily, readily begin integrating power mobility use into their daily lives, and rapidly meet the criteria for purchasing an individually prescribed power wheelchair. Few studies,^19,20,22 however, have focused on the influence of power mobility training on the parents of children who are exploratory power mobility learners. These learners are typically either very young children (infants and toddlers) or children with severe disabilities who require longer, more extensive training periods to acquire power mobility skills and who typically do not meet the criteria for an individually prescribed power wheelchair.^19,20,23

Exploratory power mobility learners are not yet ready to use power mobility in their daily lives and therefore typically participate in power mobility training only during limited and specified times. As a result, they often receive training on alternative power mobility devices, such as the Power Wheelchair Trainer (Trainer).^22,24 The Trainer is a motorized platform that temporarily converts a manual wheelchair or adaptive stroller into a power mobility device, thereby allowing children with severe disabilities, who often require extensive customized seating options, to practise using power mobility.^22,24

The purpose of this study was to investigate the effects of power mobility training, provided twice a week to exploratory power mobility learners with cerebral palsy (CP; Gross Motor Function Classification System [GMFCS]²⁵ Level V), on (1) parenting stress, (2) parents’ perceptions of their children, and (3) children’s attainment of power mobility skills. On the basis of prior work with exploratory power mobility learners,^{19,20,22–24} we hypothesized that power mobility training would positively influence both parenting stress and parents’ perceptions of their children and that the children would attain power mobility skills.

Methods

A non-concurrent, multiple-baseline, A–B single-subject research design (MBD SSRD)²⁶ study was conducted with three participants recruited through their previous involvement in university activities. An MBD SSRD provides a higher level of evidence than a simple A–B SSRD or a withdrawal A–B–A SSRD. We chose this design to build on previous work in the area and increase the rigor and level of evidence provided by the SSRD as outlined by Logan and colleagues.²⁶ Figure 1 provides an overview of the study design.

Figure 1 .

Overview of study design.

PM = power mobility; CPCHILD = Caregiver Priorities and Child Health Index of Life with Disabilities Questionnaire; PSI–4–SF = Parenting Stress Index–Short Form; COPM = Canadian Occupational Performance Measure; ALP = Assessment of Learning Powered mobility use; WSC = Wheelchair Skills Checklist.

Each participant was assigned by chance (i.e., without replacement and without randomization) to a baseline (A) phase of a different duration (3 wk, 4 wk, or 5 wk). This phase was immediately followed by an 8-week intervention (B) phase. Twice-weekly sessions were conducted during both phases. On the basis of previous work in this area,²² and to ensure that the retention interval was longer than the baseline phase, a single post-intervention follow-up session was conducted 6 weeks after the end of the intervention phase to assess how well the children had retained their power mobility skills. The inclusion criteria were children aged 3–12 years, a diagnosis of CP (GMFCS Level V), and having a manual wheelchair or adaptive stroller that could be safely used with the Trainer.^22,24 The exclusion criteria were participation in power mobility training within the previous year and inability to tolerate sitting in their own manual wheelchair for 60 minutes.

The Human Research Review Committee at Grand Valley State University approved the study. Parental consent and permission were obtained for all participants, and assent was obtained, if applicable. Step-by-step procedures ensured procedural fidelity in each study phase.

Outcome measures

The target behaviour was a change in the magnitude of parenting stress experienced by the self-identified primary caregiving parent of each participant. This parent was present at each research session in both phases of the study. To assess the target behaviour, we used the Parenting Stress Index–Short Form (PSI–4–SF),²⁷ a 36-item parent questionnaire composed of three subscales (Parental Distress, Parent–Child Dysfunctional Interaction, and Difficult Child) that contribute to a Total Stress score. Each subscale reflects different aspects and sources of parenting stress associated with parenting a child. Parental Distress indicates a parent’s feelings of competency, support, conflict, restriction, and depression in his or her role as parent.²⁷ Parent–Child Dysfunctional Interaction denotes the extent to which a parent feels satisfied with both the child and his or her interactions with the child.²⁷ Difficult Child indicates a parent’s perception of how easy or difficult his or her child is to care for and manage.²⁷ The Total Stress score indicates the overall level of parenting stress that someone feels in his or her role as a parent.²⁷

The PSI–4–SF is a valid and reliable tool that has been used in studies involving parents of children with CP.^11,13 It was administered in paper form twice a week in both phases of the study using the procedures outlined in the manual.²⁷ One parent of each participant consistently completed the form (as well as all the other parent-report measures outlined next) throughout the study and in the same university laboratory setting, with the same researcher providing the same instructions each time. At each administration of any outcome measure in the study, the parents were blinded to any previous responses we had obtained.

The secondary outcome measures used to assess the parents’ perceptions of their children were the Caregiver Priorities and Child Health Index of Life with Disabilities Questionnaire (CPCHILD)²⁸ and a parental interview. The CPCHILD, a reliable and valid measure of a caregiver’s perceptions of the health status, comfort, well-being, and ease of caregiving for a child with severe developmental disabilities, was developed to measure the effectiveness of interventions. It consists of six domains (Personal Care/Activities of Daily Living; Positioning, Transferring, & Mobility; Comfort & Emotions; Communication & Social Interaction; Health; and Overall Quality of Life) and a total score. Standardized scores ranging from 0 (best) to 100 (worst) were calculated for each domain and for the total score.²⁸ The CPCHILD was administered at the beginning and end of the study. The parental interview, also conducted at the beginning and end of the study, consisted of two questions: “Can you describe [child’s name] for me?”^29,30 and “How do you think your child will respond/responded to power mobility training?” The interviews were transcribed verbatim.

Secondary outcomes pertaining to the children’s attainment of power mobility skills were assessed using the Canadian Occupational Performance Measure (COPM),³¹ the Assessment of Learning Powered mobility use (ALP),³² and the Wheelchair Skills Checklist (WSC).³³ The COPM was used to assess parents’ perceptions of both their child’s performance and their satisfaction with any parent-identified, child-specific occupational performance issues related to power mobility use. The COPM, a valid and reliable tool for use with children with CP,³¹ was administered at the end of the baseline phase and re-administered to the same parent at the completion of the intervention phase.

The ALP reflects the process of learning how to use a power mobility device. It consists of eight phases signifying the continuum of learning from novice to expert. The WSC assesses a child’s ability to perform seven basic power mobility skills. Both measures were administered through therapist observation at the completion of the first and last power mobility training sessions in the intervention phase as well as at the single 6-week post-intervention follow-up session. Throughout the study, the ALP and the WSC were scored by researcher consensus.

Intervention

On the basis of previous research involving exploratory power mobility learners and a systematic review focused on power mobility training methods,^19,20,22,34 power mobility training was provided twice a week in a university setting (classrooms, laboratory spaces, hallways, etc.) using the Trainer. Each session consisted of actual practice time of 45 to 60 minutes during the intervention phase.^22,24,34 Decisions about access (joystick or switch/switches) were made according to the researchers’ clinical experience and the concepts outlined in previous research.^22,24,34 These decisions were updated as needed throughout the intervention phase on the basis of each child’s progress.

Power mobility training methods were individualized to the participants following these steps: (1) motivational and reinforcement factors were identified during the standardized interview in the Reinforcement Assessment for Individuals with Severe Disabilities (RAISD);³⁵ (2) participant-specific power mobility goals were created using the Power Mobility Training Tool;³⁶ (3) the information gathered in Steps 1 and 2 was used to promote play and performance of goal-related tasks in a customized, engaging environment designed to encourage the emergence of power mobility skills;³⁴ and (4) participant-specific verbal and physical prompts (identified by the RAISD) were used to encourage each participant.

Data analysis

Raw scores on the PSI–4–SF were standardized according to the manual. Given the potential for serial dependency in repeated measurements, serial dependency within the baseline scores was assessed by calculating autocorrelation coefficients using procedures outlined by Ottenbacher.³⁷ Lag-1 autocorrelations (score pairs formed by adjacent time points during the baseline) were computed across the baseline data with an α level of p < 0.05.^37,38

The significance of changes on the three PSI–4–SF subscales and the summed, standardized Total Stress scores were evaluated visually and using the split-middle celeration lines calculated for both the baseline and the intervention phases.³⁹ Any differences between phases were assessed using trend, level, and variability measures.^37,39 To determine significance, the proportion of intervention data points falling above or below the baseline celeration line extended through the intervention phase was compared with the minimum proportion required for a significant effect at p < 0.05 using the probability table provide by Ottenbacher.³⁷ Following the manual,³¹ the clinical significance of the COPM outcomes was set as an increase of 2 or more points in either performance or satisfaction.

The Linguistic Inquiry and Word Count (LIWC 2015) programme was used to analyze the parental interviews.⁴⁰ LIWC 2015 is a text-analysis programme developed on the premise that the words people use reflect their physical and mental health and can be used to learn about their beliefs, thinking patterns, emotions, social relationships, and personalities. LIWC 2015 examines each word in a transcript against an internal dictionary of more than 6,000 words to place the word into the appropriate linguistic and psychological categories; it can objectively evaluate a transcript on the basis of four summary language variables: Analytical Thinking, Clout, Authenticity, and Emotional Tone.

Higher Analytical Thinking scores are associated with greater use of articles and prepositions, indicating categorical language (i.e., references to objects and concepts organized in a complex way), and lower scores are associated with greater use of auxiliary verbs, pronouns, adverbs, conjunctions, and negations, indicating more dynamic language (i.e., personal narratives). Higher Clout scores indicate the use of fewer first-person singular pronouns and more first-person plural and second-person singular pronouns. Higher Clout scores further indicate an other-focus, whereas lower scores indicate a self-focus that is related to the relative social status or confidence that people display through their speech. Higher Authenticity scores indicate a more modest and vulnerable perspective, with greater cognitive complexity, more references to self and others, and use of fewer negative emotion words. Higher Emotional Tone scores indicate the use of more positive words; conversely, lower scores indicate the use of more negative emotion words.

Algorithmically derived from previous research indicating a pattern of word use across numerous LIWC 2015 categories,⁴⁰ these summary language variables are expressed as percentiles ranging from 0 to 100, as shown in Figure 2. These variables were used to compare each parent’s perceptions of their child, reflected in their use of words at the beginning of the study, with their perceptions (again reflected in their use of words) at the end of the study. In addition, based on our previous work with this population using LIWC 2015 to analyze interview data,^22,41 a custom-created LIWC 2015 language variable, Difficulties and Interventions, was developed to capture words used by parents during the parental interviews to describe their children’s diagnoses and conditions (e.g., cerebral palsy, epilepsy, 24-weeker), inabilities (e.g., nonverbal, multi-impaired), and specialized services and equipment (e.g., center-based school programmes, adapted stroller). This variable was expressed as a percentage of the total number of words in a transcript.⁴⁰

Figure 2 .

Linguistic Inquiry and Word Count programme 2015 summary language variables.

Visual inspection and effect sizes were used to determine the degree of change in each of the summary language variables from the beginning to the end of the study: standardized mean difference (SMD)

$$d=\frac{\mathit{\text{Post\hspace{0.17em}Score}}-\mathit{\text{Pre\hspace{0.17em}Score}}}{\mathit{\text{SD\hspace{0.17em}of\hspace{0.17em}}}3\mathit{\text{\hspace{0.17em}Participants}}’\mathit{\text{\hspace{0.17em}Pre\hspace{0.17em}Scores}}}.$$

⁴² Measuring effect sizes in SSRDs has increasingly been used over the past 20 years to supplement visual evaluations of clinical change and intervention efficacy, despite the violation of assumptions inherent in between-subject designs.⁴² As with the calculation of Cohen’s d (a fundamental effect size measure for independent samples), SMD calculates the difference between the mean at intervention and the mean at baseline and divides it by the SD at baseline.^43,44 Because it corresponds to Cohen’s d, researchers can use SMD to interpret magnitude of change, whereby 0.20 ≤ d < 0.50 is considered a small effect, 0.50 ≤ d < 0.80 a medium effect, and d ≥ 0.80 a large effect.⁴⁵ To decrease the potential for bias, the researchers were blinded to each participant’s power mobility performance during their analyses of the parental interviews.

Results

The characteristics of the three participants are provided in Table 1.^25,46–48 Although all three became ill and required a brief stay in hospital during the intervention phase, they completed 100% of the study-related activities per protocol, and no adverse events occurred. Lag-1 autocorrelations were significant (p < 0.05) for the baseline PSI–4–SF Total Stress scores for the parent of Participant 3, indicating the potential for serial dependency in their baseline scores. None of the other baseline data exhibited statistically significant autocorrelations. According to Ottenbacher,³⁷ if serial dependency is detected in baseline data, autocorrelation coefficients can be re-calculated using increasing lags (pairing scores with subsequent time points). A lag-3 autocorrelation (pairing scores with scores three time points ahead) reduced serial dependency in the baseline data of Participant 3’s Total Stress scores to below significant levels (p < 0.05).

Table 1 .

Participants’ Characteristics

Participant	Age, beginning of study	Diagnosis	GMFCS25 level	MACS46 level	CFCS47 level	EDACS48 level
1	5 y, 5 mo	Spastic quadriplegic CP; microcephaly; CVI	V	V	V	V
2	8 y, 8 mo	Spastic quadriplegic CP; seizures; CVI	V	V	V	V
3	8 y, 4 mo	Spastic quadriplegic CP; seizures; CVI	V	V	V	V

GMFCS = Gross Motor Function Classification System; MACS = Manual Ability Classification System; CFCS = Communication Ability Classification System; EDACS = Eating and Drinking Ability Classification System; CP = cerebral palsy; CVI = cerebral visual impairment.

The PSI–4–SF results are provided in Table 2 and in Figure 3, in which the mean PSI score is 50 (SD 10) and trending is based on median values using the split-half approach. Table 3 provides the results on the CPCHILD and the published means and SDs for CPCHILD scores of children at GMFCS Level V. Table 4 gives the details of each participant’s access method (joystick or switch/switches) and the pre- and post-intervention scores on the measures of power mobility skills. Figure 4 displays the results of the LIWC 2015 analyses for each participant. Because the parents so often referred to difficulties and interventions, we created our own language variable for this study.

Table 2 .

Results of Visual and Statistical Analyses of the Parenting Stress Index–Short Form during Baseline (A) and Intervention (B) Phases

Participant and subscale	Trend (slope)		Level (change, A to B)	Variability (CV)		Celeration line (point proportion)*
	A	B		A	B	A	B
Participant 1
Parental Distress	0.00	0.29	−1.30	0.04	0.03	0.30	0.44
Parent–Child Dysfunctional Interaction	−0.20	0.00	1.40	0.03	0.02	0.60	1.00†
Difficult Child	0.00	0.00	4.00	0.03	0.03	0.10	0.94†
Total Stress	0.00	0.17	0.05	0.03	0.02	0.30	1.00†
Participant 2
Parental Distress	0.25	0.07	−4.50	0.04	0.02	0.50	1.00†
Parent–Child Dysfunctional Interaction	0.25	0.13	−0.20	0.01	0.03	0.38	0.75†
Difficult Child	0.25	0.06	−1.39	0.02	0.01	0.38	1.00†
Total Stress	0.38	0.13	−3.45	0.02	0.01	0.63	1.00†
Participant 3
Parental Distress	0.00	0.00	0.00	0.02	0.00	0.17	0.00
Parent–Child Dysfunctional Interaction	−0.67	−0.13	1.40	0.02	0.01	0.50	1.00†
Difficult Child	0.00	0.00	−2.00	0.04	0.02	0.17	0.81†
Total Stress	−0.33	−0.13	1.37	0.03	0.01	0.50	0.94†

^*Proportion of data points falling above or below median trendline for each phase.

^†Significant difference between baseline (A) and intervention (B) phases at p < 0.05.

CV = coefficient of variation.

Figure 3 .

Results of the Parent Stress Index–Short Form for each participant’s primary caregiver during the baseline and intervention phases: (a) Participant 1, (b) Participant 2, and (c) Participant 3.

PD = Parental Distress; P–CDI = Parent–Child Dysfunction Interaction; DC = Difficult Child; TS = Total Stress.

Table 3 .

CPCHILD: Published Means and SDs for Children at GMFCS Level V and Results for Each Participant

Domain	Mean (SD)	Participant 1		Participant 2		Participant 3
		Start of study	End of study	Start of study	End of study	Start of study	End of study
Personal Care/Activities of Daily Living	31.0 (15.2)	38.27	37.03	37.03	43.21	43.21	38.27
Positioning, Transferring, and Mobility	28.4 (14.2)	41.66	39.89	28.57	40.27	44.44	45.83
Comfort and Emotions	67.9 (22.6)	95.24	74.60	79.36	91.83	85.71	96.82
Communication and Social Interaction	43.4 (23.7)	61.11	69.05	40.48	33.33	59.53	64.29
Health	57.0 (16.9)	100.00	73.33	53.33	33.33	53.33	46.67
Overall Quality of Life	55.4 (24.8)	100.00	100.00	60.00	60.00	60.00	60.00
Total score	44.4 (12.6)	63.93	57.27	48.64	49.92	56.60	60.34

CPCHILD = Caregiver Priorities and Child Health Index of Life with Disabilities; GMFCS = Gross Motor Function Classification System.

Table 4 .

Participants’ Access Methods (Joystick or Switch[es]) and Pre- and Post-intervention Scores on Measures of Power Mobility Skills

Participant	Method and location of power mobility training session		ALP phase		WSC, no. of skills out of 7		No. of occupational performance problems achieving clinically significant change on the COPM*		6-week follow-up†
	Initial	Final	Initial	Final	Initial	Final	Performance	Satisfaction	ALP phase	WSC, no. of skills out of 7
1	1 large (5 in/12.7 cm) switch on tray attached to front of wheelchair, activated using either UE	3 switches – 1 large (5 in/12.7 cm) for forward and 2 small (2.5 in/6.4 cm) for right and left – on tray attached to front of wheelchair, activated using either UE	2	5	0	5†	5/5	4/5	5 (emerging skills at Phase 6)	5†
2	1 large (5 in/12.7 cm) switch on tray attached to front of wheelchair, activated using either UE	2 switches – 1 large (5 in/12.7 cm) for forward and 1 small (2.5 in/6.4 cm) for right OR 2 small (2.5 in/6.4 cm) for spinning right and left – on tray attached to front of wheelchair, activated using either UE	2	5	0	5†	5/5	5/5	5	5†
3	1 large (5 in/12.7 cm) switch on tray attached to front of wheelchair, activated using either UE	3 switches – 1 large (5 in/12.7 cm) for forward and 2 small (2.5 in/6.4 cm) for right and left – on tray attached to front of wheelchair, activated using either UE	3	6	0	5†	5/5	5/5	5	5†

^*An increase of ≥2 points in either performance or satisfaction indicates a clinically significant improvement.

^†Skills required to be performed on command were not demonstrated 100% of the time because of participants’ inability to consistently follow directions.

ALP = Assessment of Learning Powered mobility use; WSC = Wheelchair Skills Checklist; COPM = Canadian Occupational Performance Measure; UE = upper extremity.

Figure 4 .

Results of the Linguistic Inquiry and Word Count 2015 programme analyses: summary language variables for (a) Participant 1, (b) Participant 2, and (c) Participant 3; (d) custom-created language variable Difficulties and Interventions.

The results for each participant are discussed next.

Participant 1

As seen in Table 2 and Figure 3, during the baseline phase, the parent of Participant 1 exhibited extremely low parenting stress scores on each PSI–4–SF subscale (from the 1st percentile or lower for Difficult Child to the 37th percentile for Parent–Child Dysfunctional Interaction). Both Table 2 and Figure 3 also show statistically significant increases in parenting stress between the baseline and intervention phases for both subscales, as well as for the aggregate Total Stress score. Despite these significant increases, parenting stress levels remained at a clinically low level throughout the study. Figure 3 displays slight changes in trend and variability between the phases. Substantial changes in level (degree of difference between the position where the celeration lines for the baseline and intervention phases cross the vertical line separating them) were found for both the Parent–Child Dysfunctional Interaction and Difficult Child subscales. Supporting the statistical analyses, this parent’s level of parenting stress increased on the Difficult Child and Parent–Child Dysfunctional Interaction subscales at the introduction of the intervention phase and remained steady throughout.

LIWC 2015 analysis of the parental interviews revealed small increases in Clout and Authenticity scores and a small decrease in Emotional Tone score between the interviews at the beginning and end of the study. The small increases in Clout and Authenticity scores reveal that at the end of the study, this parent was more confident and more modest or vulnerable when answering questions from the interviewer. At the end of the study, she also used positive words slightly less frequently but remained largely positive in her descriptions overall. The analysis further revealed a large (d ≥ 0.80) decrease in this parent’s references to Difficulties and Interventions between the beginning and end of the study.

On the COPM, Participant 1 achieved clinical significance for performance for five of five identified occupational performance problems (cause-and-effect skills, basic power mobility skills such as making turns and moving forward, using more than one switch, and using power mobility to interact with others during the sessions) and for satisfaction in four of five problems.

Participant 2

As seen in Table 2 and Figure 3, during the baseline phase the parent of Participant 2 exhibited extremely high levels of parenting stress on each PSI–4–SF subscale (from the 67th percentile for Parental Distress to the clinically significant 93rd percentile for Difficult Child). Table 2 and Figure 3 also show that statistically significant changes occurred between the baseline and intervention phases, with the magnitude of parenting stress on each subscale decreasing during the intervention phase. Visual analyses indicate non-existent changes in variability between the phases, as well as slight decreases in the upward trends of the baseline phase for each subscale and the Total Stress score. For each subscale, slight to substantial decreases were also noted. Strengthening these statistical findings, and as shown in Figure 3, this parent’s level of parenting stress in all areas began to decrease at the introduction of the intervention phase and remained steadily lower throughout.

LIWC 2015 analysis of the parental interviews revealed large increases in Clout and Analytical Thinking scores and large decreases in Authenticity and Emotional Tone scores between the interviews at the beginning and end of the study. The large increases in Clout and Analytical Thinking scores reveal that at the end of the study, this parent was highly confident and more likely to think about her child in a logical, categorical way. By the end of the study, she was less frequently using positive emotion words in a controlled manner when answering questions posed by the researcher, but overall remained largely positive in her descriptions. A large decrease in her references to Difficulties and Interventions was also noted between the beginning and end of the study (d ≥ 0.80).

On the COPM, Participant 2 achieved clinical significance for both performance and satisfaction for five of five identified occupational performance problems (basic power mobility skills such as stopping, making turns, and moving forward, using more than one switch, and using power mobility to interact with her sibling during sessions).

Participant 3

As seen in Table 2 and Figure 3, during the baseline phase, the parent of Participant 3 displayed normal levels of parenting stress on each subscale of the PSI-4-SF (from the 46th percentile for Parental Distress to the 78th percentile for Parent–Child Dysfunctional Interaction). Both Table 2 and Figure 3 show that significant increases in parenting stress levels occurred between the baseline and intervention phases for both Parent–Child Dysfunctional Interaction and Total Stress. While these increases occurred at the beginning of the intervention phase as shown in Figure 3, visual inspection revealed downward baseline trends that continued (to a lesser degree) afterwards. In contrast, her parenting stress on the Difficult Child subscale showed a statistically significantly decrease from baseline to intervention. Supporting the statistical analyses, her level of parenting stress decreased at the introduction of the intervention phase and remained steady throughout the remaining intervention sessions. Inspection of variability revealed stability among the phases for all four parenting stress scores.

For this parent, the LIWC 2015 analysis of the qualitative interviews revealed small and moderate increases in Clout and Emotional Tone, respectively between the interviews at the beginning and the end of the study. In addition, the analysis found a small decrease in Analytical Thinking and a large decrease in Authenticity, indicating that she responded to questions more confidently and used more positive emotion words in a manner that was more personal, but with a restrained style of speech, by the end of the study. A large decrease in her references to Difficulties and Intervention was also noted between the beginning and end of the study (d ≥ 0.80).

On the COPM, Participant 3 achieved clinical significance for both performance and satisfaction for five of five identified occupational performance problems (cause-and-effect skills, basic power mobility skills such as stopping and moving forward, using more than one switch, and using power mobility to obtain a desired object in the environment).

Retention of power mobility skills

As shown in Table 4, ALP and WSC scores at the single post-intervention follow-up session suggest that at 6 weeks post-intervention, participants retained the power mobility skills that they had gained during the intervention phase.

Discussion

This study investigated the effects of power mobility training provided to children with severe CP on (1) parenting stress, (2) parents’ perceptions of their children, and (3) children’s attainment of basic power mobility skills. Improved PSI–4–SF scores were noted for two of the three parents.²⁷ The parent of Participant 2 reported exceedingly high levels of parenting stress at the beginning of the study and experienced the most dramatic reduction in parenting stress by the end. After the start of the intervention phase, she reported significantly less parenting stress from personal distress factors such as her own perceived parenting competence, social support, restrictions placed on her other roles beyond parenting, and depression. She also reported less parenting stress stemming from dysfunctional interactions with her child (e.g., her child not meeting her expectations) and difficulties managing her child’s behaviour. The parent of Participant 3 displayed a significant reduction in parenting stress on the Difficult Child subscale, suggesting that she also found her child’s behaviour easier to manage after the beginning of the power mobility training.

Paradoxically, increased parenting stress between the baseline phase and power mobility intervention was also observed. The parents of Participants 1 and 3 reported significantly higher levels of parenting stress caused by their child not meeting their expectations, with less reinforcing parent–child interactions. Participant 1’s parent also reported more parenting stress resulting from difficulties managing her child’s behaviour after the power mobility training began.

One explanation for the variation in results among the three parents could be that the benefits of power mobility training varied according to their initial parenting stress levels and that their perceptions of their children’s abilities and behaviours changed. This suggests that for parents experiencing extreme degrees of parenting stress, there may be a broad reduction in parenting stress related to the power mobility intervention that encompasses the entire parent–child system, as reflected in the lower parenting stress scores on each subscale and in the Total Stress score. For parents who report below-average or average amounts of parenting stress, changes resulting from power mobility training may be more related to their child’s behaviours and what they expect of their child during the power training period itself. A mix of emotions and initial increases in general stress have been reported by parents whose children are using power mobility devices.^3,4 Future research should continue to tease out the complexities of the possible influence of power mobility training on parent and child.

Findings for the CPCHILD were mixed and may have been influenced by the fact that each participant was ill and briefly hospitalized during the intervention phase.⁴⁹ Interpreting these findings is challenging because published use of the CPCHILD primarily reflects caregivers’ perceptions of changes in health-related quality of life and their burden after surgical interventions.^50,51 Only one publication, a case report involving an 18-year-old girl with CP (GMFCS Level V), used the CPCHILD before and after power mobility training.²⁴ Future research that explores the responsiveness of the CPCHILD after non-surgical or assistive technology interventions is needed to more fully evaluate parents’ perceptions of their children’s health status, comfort, and well-being and ease of caregiving after their children have been involved in power mobility interventions.

The LIWC 2015 analyses suggest that each parent’s perceptions of their child may have changed over the course of the study. This change is reflected in the differences in their use of words during the interviews at the beginning and end of the study. To illustrate this change, consider the following excerpts from the first 10 sentences of the responses by the parent of Participant 2 to the interview questions at the beginning and end of the study.

From the interview at the beginning of the study: [Child’s name] is a severely, multiply impaired 8-year-old. She has a complex medical history and a lot of developmental delays. She has spastic quad cerebral palsy. She has epilepsy. She is fed by tube. She is non-verbal and just kind of has a lot going on. Lots of therapies, special education. Total care. She is mostly fecal-continent but urinary is not so much, so she is in diapers full time. And she is just really starting to communicate her needs and wants.

From the interview at the end of the study: [Child’s name] is a sweet-natured child. She is a lot happier than she used to be. [Child’s name] loves people. She loves interacting. She loves meeting kids. She loves playing with people. She is a very social kid. Communication is a struggle, so she can’t always tell us what she wants or needs. But we are working on it. She loves her brother.

During the first interview, this parent’s response largely alternates between “She is” and “She has” statements, with many statements referring to the child’s diagnosis and symptoms. In contrast, at the end of the study, the parent’s response alternates between “She is” and “She loves” statements with a complete absence of diagnoses. Although both interviews mention Participant 2’s difficulty with communication, the second interview puts it in a positive light, perhaps indicating the parent’s awareness of a possibility for improvement.

At the end of the study, moreover, all three parents described their child and their response to power mobility in a more confident manner (e.g., higher Clout scores). The LIWC 2015 analyses also revealed that all the parents tended to be highly positive but guarded when discussing their child both at the beginning and at the end of the study. Finally, the parent of Participant 2, who had high levels of parenting stress during the baseline phase of the study, exhibited a substantial change in scores for the summary language variable of Analytical Thinking. When responding to interview questions about her daughter at the end of the study, she used words reflecting more formal, hierarchical thought than at the beginning of the study.

Consistent with findings in the qualitative literature (see, e.g., Wiart and colleagues),² the results of this study suggest that power mobility training can influence the way parents view their children and their children’s abilities. Analytical thought is vital to the coping process because it provides a means of breaking down difficult challenges into manageable parts.⁵² Thus, the improvements in analytical thought, confidence, and positivity demonstrated by the parents can point to the additional benefits of power mobility for both parent and child. Parental perceptions play a critical role in children’s daily lives, treatment options, and intervention success, so being aware of potential changes in these attitudes can help clinicians and therapists maintain high standards of family-centered care.^2,3,6

At the beginning of the intervention phase, all three participants would have been classified by Field and Livingstone as exploratory power mobility learners.²³ The gains in power mobility skills demonstrated by all three participants (and documented through the COPM) suggest that they made improvements in their basic power mobility skills. Overall, it appears that all participants benefited from the learning experiences provided by the power mobility training even though none of them became a functional power mobility learner (i.e., none of the participants qualified for an individually prescribed power wheelchair).²³

An unexpected finding was that, during the study, each participant not only learned to use switches to operate the Trainer but also demonstrated improved cause-and-effect skills in other activities. For example, during the latter part of the intervention phase and into the 6-week period between the end of the intervention phase and the post-intervention follow-up session, two participants began trialing eye-gaze communication devices, and the third participant began using a multi-switch communication device. Those first two participants “qualified” to purchase their own eye-gaze communication device in the 3 months after the end of the intervention phase.

These unexpected improvements in switch use apart from the Trainer suggest that the children were carrying over cause-and-effect skills. Such findings imply that they progressed along the learning continuum to becoming operational power mobility learners,²³ focused on mastering operational use of the power mobility device. Future studies involving power mobility training for children with severe disabilities should incorporate a formal assessment of cause-and-effect skills across study phases as a way to explore this unexpected finding.

This study had several limitations. First, although an MBD SSRD replicated across three subjects provides a higher level of evidence than a simple A–B SSRD or a withdrawal A–B–A SSRD,²⁶ the results would have been strengthened if the study had been carried out with more participants across multiple sites and if randomization had been used to assign the duration of the baseline phase for each participant.²⁶ Second, administration of the ALP and the WSC inherently involves power mobility use, thereby precluding the ability to mask the study phase. An outcome measure that does not imply power mobility use may help to increase rigor in future studies. Third, the findings pertaining to the reduction in Total Stress scores for the parent of Participant 3 should be interpreted with caution because of the potential for serial dependency on their baseline Total Stress scores.

Although LIWC 2015 is becoming more widely used in clinical investigations,⁵³ the current study is the first to use the summary language variables to quantify changes in response to power mobility interventions. Caution should be used when interpreting these results. Next, the SSRD and a lack of LIWC 2015 comparison groups at this time further restrict the analyses of LIWC 2015 difference to measuring effect size. Moreover, differences between the interviews at the beginning and end of the study might have related to other factors, including the parents’ increased familiarity with the interviewer. Finally, given that reliability and clinically important change values have not yet been established for the ALP and the WSC (or for the CPCHILD related to power mobility training), the findings from these measures must be viewed as only descriptive in nature.

Conclusion

Our findings suggest that power mobility training can affect levels of parenting stress. Future research should examine whether power mobility training can ameliorate normal to high levels of parenting stress stemming from difficulties handling children’s behaviour for parents who report such levels of parenting stress. Further exploration of the ability of LIWC 2015 to capture the parental or caregiver benefits of power mobility training is also needed.

Key Messages

What is already known on this topic

Power mobility use has been associated with decreased parenting stress in parents of young children with mobility limitations.

What this study adds

Power mobility training provided to exploratory power mobility learners with cerebral palsy can influence levels of parenting stress.