Objective To evaluate the success rates of home cardiorespiratory polygraphy in children under investigation for sleep-disordered breathing and parent perspectives on equipment use at home.
Design Prospective observational study.
Setting Sheffield, Evelina London and Southampton Children’s Hospitals.
Patients Data are reported for 194 research participants with Down syndrome, aged 0.5–5.9 years across the three centres and 61 clinical patients aged 0.4–19.5 years from one centre, all of whom had home cardiorespiratory polygraphy including respiratory movements, nasal pressure flow, pulse oximetry, body position and motion.
Main outcome measures Percentage of home cardiorespiratory studies successfully acquiring ≥4 hours of artefact-free data at the first attempt. Parental report of ease of use of equipment and preparedness to repeat home diagnostics in the future.
Results 143/194 (74%; 95% CI 67% to 79%) of research participants and 50/61 (82%; 95% CI 71% to 90%) of clinical patients had successful home cardiorespiratory polygraphy at the first attempt. Some children required multiple attempts to achieve a successful study. Overall, this equated to 1.3 studies per research participant and 1.2 studies per clinical child. The median artefact-free sleep time for successful research studies was 515 min (range 261–673) and for clinical studies 442 min (range 291–583). 84% of research and 87% of clinical parents expressed willingness to repeat home cardiorespiratory polygraphy in the future. 67% of research parents found the equipment ‘easy or okay’ to use, while 64% of clinical parents reported it as ‘easy’ or ‘very easy’.
Conclusions Home cardiorespiratory polygraphy offers an acceptable approach to the assessment of sleep-disordered breathing in children.
- sleep-disordered breathing
- obstructive sleep apnoea
- cardiorespiratory polygraphy
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What is already known on this topic?
Home-based cardiorespiratory polygraphy sleep studies (CRPG) have been proposed as a viable alternative to in-hospital studies but there are limited reports in children.
Hospital is disruptive to the child and family and to the care of other children.
What this study adds?
Parents report that home sleep studies are an acceptable alternative to in-hospital studies in children with diverse comorbidities.
On average, 76% of children had successful home CRPG studies on the first attempt and 87% after one or more repeat studies.
While the standard for a successful study was more than 4 hours of artefact-free data, overall 83% of studies acquired more than 6 hours.
Sleep-disordered breathing, an umbrella term for conditions that result in disturbed ventilation during sleep,1 can broadly be classified as being either obstructive or central in nature. Obstructive sleep apnoea is characterised by intermittent collapse of the upper airway, and central sleep apnoea by repetitive complete cessation of respiratory effort, during sleep.
Obstructive sleep apnoea, the most common cause of sleep-disordered breathing, peaks during the preschool years in association with adenotonsillar hypertrophy and again during adolescence with obesity. Demand on diagnostic services has arisen as a result of increased understanding that a wide range of paediatric conditions predispose to sleep-disordered breathing.2
The international gold standard investigation for sleep-disordered breathing is polysomnography which combines cardiorespiratory and neurophysiological sensors.3 Polysomnography provides the most accurate estimate of hypopnoea (partial reduction in airflow) as these events are only scored when associated with either oxygen desaturation or an electroencephalogram arousal.4 However, polysomnography is not universally available and requires considerable technical expertise to set up and interpret. Cardiorespiratory polygraphy (CRPG), which excludes neurophysiological measures, provides a recognised alternative in adults5–7 and is increasingly reported in children.8–11 Paediatric CRPG has adequate sensitivity (90.9%) and specificity (94.1%) for the diagnosis of clinically significant obstructive sleep apnoea.12 While the European Respiratory Society Task Force identifies polysomnography as the preferred diagnostic method, it recognises CRPG as an alternative where resources are limited.13 As noted by a leader in the field, ‘the times they are a changing.’14
The introduction of miniaturised devices means that CRPG is now feasible in the home environment15 16 and the scope to evaluate more ‘efficient ways of diagnosing sleep-disordered breathing’17 18 is paramount. We report lessons learnt from research and clinical experience of home CRPG in 255 children with diverse comorbidities.
Materials and methods
Research: Participants were recruited at Sheffield, Evelina London and Southampton Children’s Hospitals.
Clinical: Data from a new home CRPG service in Southampton Children’s Hospital.
Research: Children had a diagnosis of Down syndrome, were aged 6 months to 6 years, had not had a CRPG in the last 3 months and were not receiving home oxygen or non-invasive ventilation.
Clinical: Children were referred to the clinical service with suspected sleep-disordered breathing, or for a ventilation titration study. Families chose either inpatient or home CRPG. Exclusions included families not conversant in English or children requiring other hospital-based investigations contemporaneously.
Research: Children were recruited between 2013 and 2015 through community and hospital routes to reduce selection bias.19 Families were actively encouraged to attempt home CRPG as the preferred setting if deemed appropriate by the clinician. However, if parents expressed a preference for an in-hospital study then the CRPG was carried out on identical equipment in the sleep laboratory.
Clinical: Eligible families referred to the clinical service self-selected either inpatient or home CRPG between 2015 and 2016. Only clinical patients who underwent home CRPG are reported here.
Ethics and consent
The research study was approved by the UK National Research Ethics Committee (reference 13/SC/0106). Parents provided written consent on behalf of their child. The clinical patients were offered home CRPG as a new clinical pathway and their anonymous data reported in accordance with UK Department of Health guidance for research ethics20 as part of a service evaluation.
Demographics and medical history
Research: Data were recorded on age, gender and socioeconomic status (parents’ age at leaving full-time education), and age-appropriate sleep questionnaires21 22 reported whether the child had restless sleep.
Clinical: Data on age, gender, underlying comorbidity and past experience of CRPG were recorded.
For all children, sleep-disordered breathing was assessed using the SOMNOtouch device (SOMNOmedics, Germany) comprising: chest and abdominal respiratory inductance plethysmography; pulse oximetry (Bluepoint) yielding saturations (SpO2), plethysmography and pulse rate; nasal pressure flow with integral snore sensor; body position sensor; and actimetry. In addition, for the clinical cohort routine contemporaneous pulse oximetry (Masimo, USA) and transcutaneous carbon dioxide (SenTec, Switzerland) monitoring was undertaken and a subgroup also had video monitoring. For study failures, families were given the opportunity to repeat the CRPG.
CRPG equipment training
Families attended the hospital on a single occasion and were taught how to set up and use the CRPG equipment. Written and photographic instructions were provided. The abdominal and thoracic bands were measured on the child to minimise parental adjustments later. Parents set up their own children that evening at home. Telephone advice was offered until 23:00 hours. The CRPG device was programmed to auto-record at a predetermined start time or was started manually. The equipment was returned by next day courier to the hospital (research) or by the parent (clinical) for data download and analysis.
Parents recorded the time their child settled in bed, fell asleep and woke in the morning alongside timing and duration of night wakings.
Quality standards and analysis
A detailed scoring procedure is published.19 Studies were manually scored by experienced clinical physiologists (RNK, JCG) using Domino Light software (SOMNOmedics). Sleep logs, actimetry, heart rate and breathing pattern were used to classify sleep and wake for each 30 s epoch. Respiratory events were scored per standard paediatric scoring criteria for adapted sensors.4
Success rates of CRPG
Studies with ≥4 hours of interpretable estimated sleep data and artefact-free respiratory parameter data15 16 were deemed successful.
Evaluation of home polygraphy
Research: Parent feedback was sought 3 months after the CRPG by structured telephone interview. Parents were asked to describe their experience of using CRPG equipment at home with response options: ‘Easy’, ‘OK’ or ‘difficult’ and how they would feel about a home study in the future with the response options: ‘happy to repeat’, ‘uncertain’ or ‘unhappy to repeat’.
Clinical: Parents completed a next day service evaluation form reporting ease of use of the equipment on a 5-point Likert scale from ‘very easy’ to ‘very difficult’ and preference for future CRPG study location.
The primary outcome measure was the percentage of children that had a successful first home CRPG. The secondary outcome measure was the acceptability (ease of use and willingness to repeat at home in the future) of home CRPG to the caregivers. Data were analysed in SPSS V.24 (IBM). Descriptive statistics are presented. Demographic differences between children who had a successful study at first attempt and those in whom the first attempt failed were explored with χ2 or Fisher’s exact test for categorical data; age was non-normally distributed among clinical and research children whose studies failed so group differences were explored with the Mann-Whitney U test. 95% CIs around percentages achieving successful home CRPG were calculated using CI analysis.
Research: Of the 202 children with Down syndrome where families consented to participate in the research,19 194 agreed to home CRPG. Median age (range) was 3.0 years (0.5–5.9), 53.1% were male.
Clinical: This group comprised 61 patients typical of referrals to a tertiary respiratory diagnostic service. Median age (range) was 7.8 years (0.4–19.5), 55.7% were male. The majority (77%) had comorbidities (table 1).
Success rates of CRPG
Research: 143/194 (74%; 95% CI 67% to 79%) had successful home CRPG studies on the first attempt. There were no differences between centres: Southampton 58/81 (72%); Sheffield 39/54 (72%); and London 46/59 (78%). Of the 51/194 (26%) failures at first attempt, 31 were willing to have a second attempt at home, of which 25/31 (81%) were successful. Two families were willing to have a third home attempt and one was successful. In total, 143+25+1=169/194 children attempting home studies ultimately achieved a successful home CRPG study (87%; 95% CI 82% to 91%), requiring an average of 1.3 attempts.
Clinical: A total of 50/61 (82%; 95% CI 71% to 90%) children had successful home CRPG studies at the first attempt. There were no differences in success rates between typically developing (78%) and non-typically developing children (84%). Of the 11 unsuccessful studies, five were repeated as inpatient CRPG, in three cases a clinical decision was made based on oximetry data and three were successfully repeated at home. Overall, therefore, 53/61 (87%; 95% CI 76% to 93%) children were successfully investigated in the home setting (requiring an average of 1.2 home attempts needed for each successful study).
Reasons for failed studies
Research: Reasons included equipment failure (15%); sensors not tolerated (30%); sensors removed before 4 hours of artefact-free data were captured (43%); and no reason recorded for (13%). The equipment was new to the market and, with support from the manufacturer, technical problems were resolved early in the study.
Clinical: Reasons included sensors not being tolerated (21%); or sensors removed before 4 hours of artefact-free data were captured (79%).
Characteristics of children where studies succeeded at first attempt
Research: There were no differences in success rates based on age, gender, socioeconomic status or whether the children were usually restless sleepers.
Clinical: Success rates at first attempt did not differ by age, gender or experience of CRPG. Table 2A and table 2B illustrates demographic data for the success and failure of the first attempt at CRPG.
Estimating sleep time
Research: Of the 169 successful home CPRG studies, most achieved well above the minimum 4 hours (240 min) of artefact-free data: median 515 (range 261–673) min; 87% achieved ≥6 hours of artefact-free estimated sleep time; 78% achieved ≥7 hours; 62% achieved ≥8 hours.
Clinical: For the clinical data the median duration of artefact-free data was 442 (range 291–583) min; 83% achieved ≥6 hours of artefact-free estimated sleep time; 60% achieved ≥7 hours; 38% achieved ≥8 hours.
Research: 165 of the 194 families (85%) were successfully contacted. Sixty-seven per cent reported that the CRPG experience was ‘easy’ or ‘okay’ while 33% reported that they found the experience difficult. Nonetheless, a majority (84%) stated they would be happy to repeat home CRPG in the future.
Clinical: Feedback from 45/61 families was provided the morning after CRPG before success of the study was determined. In the case of multiple studies, only the feedback after the first study was evaluated. Twenty-nine of 45 (64%) found the equipment ‘easy’ or ‘very easy’ to use, 31% found it ‘okay’ and 4% difficult. Only 23 families responded to the question about future preferences. Twenty of 23 (87%) stated they would prefer home CRPG in the future.
In this large sample of 255 children, 193 (76%) achieved a successful home multichannel cardiorespiratory study at the first attempt and 222 (87%) were successful when including repeat attempts. Overall, an average of 1.2–1.3 home studies per child was required to achieve adequate data. This is encouraging, particularly as the largest group was young children with Down syndrome who are often restless sleepers23 and can be challenging to study. These data suggest that home CRPG is feasible and offers a realistic option for diagnostic testing in children.
Aside from national drivers to reduce bed occupancy and cost, there is a key central argument for offering home CRPG, namely that home studies may achieve better sleep quality than in hospital.9 24 Knowledge about normal sleep architecture predicts that rapid eye movement sleep (when children are particularly vulnerable to sleep-disordered breathing) occurs predominantly towards the end of the night (figure 1). Thus, a short night’s sleep may underestimate sleep-disordered breathing. Although a minimum criterion of 4 hours of interpretable signals is often quoted for reporting paediatric CRPG studies,15 studies of this duration may miss significant sleep-disordered breathing at the end of the night. Our scoring criteria required this minimum period of sleep time to include only artefact-free data. The median-estimated artefact-free sleep time was 8.6 hours in the Down syndrome research group and 7.4 hours in the clinical group, and thus it is assumed that rapid eye movement sleep would have been captured during multiple sleep cycles.
Studies were unsuccessful for several reasons. Equipment failure was a feature of early studies as the SOMNOtouch device was newly available and staff were inexperienced in its use. Children sometimes did not tolerate sensors and removed them during the night; this was particularly a problem for nasal flow measures. With experience, staff instructed caregivers to check sensors during the night and replace sensors where possible. For clinicians introducing home-based CRPG services, we have provided practical recommendations based on our experience that may improve success rates (see box 1).
Technical tips for successful home studies
Familiarise skilled staff in equipment use in the sleep laboratory setting to anticipate technical difficulties before home use.
Select families who have had inpatient cardiorespiratory polygraphy (CRPG) before or those with night-time carers as first subjects to trial equipment on.
Create pictorial help guides/accessible online videos of set-up procedures.
Measure the child for their respiratory bands.
Trial of flow leads as above.
Plug all the sensors into the equipment so that they are securely in place before issuing to family.
Give families choice of setting the device at a pre-agreed recording start time or pressing record at bedtime.
Encourage parents/carers to do a couple of overnight checks of sensors.
Sensor refusal is more difficult to predict and address. Caregivers were encouraged to attach sensors while the child was awake to allow acclimatisation. In some cases, sensor attachment was only successful once a child was asleep. The future development of sensors that are embedded into clothing would overcome some of the issues that lead to data artefact.
Most families rated home CRPG easy or OK to use, and would choose to perform their next CRPG at home. Parents of research children whose studies failed on the first attempt at home were, unsurprisingly, more likely to report that the equipment was difficult to use (47% vs 28%). However, 76% of this group also responded that they would be happy to repeat CRPG at home in the future, it should be noted that response rates were lower for parents when first attempt at CRPG failed. Further research could usefully clarify how families could be better prepared and supported to achieve successful studies.
In the clinical sample, experience of previous CRPG was not associated with successful acquisition. Most of the Down syndrome research children were CRPG naïve, however, they would have been familiar with hospital settings and their experience may not compare directly with otherwise healthy and typically developing children. Poels et al 25 trained caregivers to set up CRPG at home in 24 children assessed prior to adenotonsillectomy. These were likely to be typically developing children with no comorbidities and study success rate was low at 29%. There were 14 typically developing, otherwise healthy children in our clinical sample and success rate in this group on first attempt was 86%. While our numbers are too low to draw firm conclusions this does suggest that prior experience of CRPG or indeed the hospital environment is not a prerequisite for successful outcomes of home studies.
We worked with the manufacturer to adapt the CRPG equipment for paediatric home usage, specifically, leads from the thoracoabdominal bands and nasal prongs were customised to be shorter to avoid risk of entanglement. This, plus the addition of an integrated video recorder for some clinical studies which aided scoring of studies may, in part, have explained the higher success rates in the clinical group.
Limitations and recommendations for future work
Participating families either self-selected as research participants or chose home CRPG in the single-centre clinical setting and are likely to be more motivated than a non-selective cohort. We do not have reliable comparative clinical data on families who chose inpatient hospital studies to indicate how representative the clinical group was. Selection bias limits the generalisability of our findings. However, in clinical settings family preference is likely to be an important predictor of success and arguably our clinical cohort is representative of typical families who would make this choice. Future studies using a patient preference design could identify clinical and sociodemographic characteristics predictive of successful CRPG studies. In addition, future multicentre studies should routinely test a wider range of important paediatric signals such as carbon dioxide and video in the home setting.
Our data did not attempt to capture costs. Indeed, no prior studies have examined the costs of paediatric home CRPG.17 Cost analysis data from Spanish adult studies have reported considerable cost savings using home CRPG.7 26 If replicated in paediatric settings, home CRPG could offer significant cost efficiencies. Finally, and importantly, future research should capture child and caregiver experiences and views about home CRPG including their preferences for preparation and training on study set-up from skilled staff.
Home-based paediatric services have been a health service aspiration for over half a century27 and offer the advantage of timely, effective care that minimises disruption for the family.28 Home CRPG shows promise as an alternative to routine diagnostic inpatient studies. Better experience for families, convenience and potential cost savings could reduce the burden on families and health services alike. Children with chronic conditions, who need repeated CRPG studies through life, may be particularly suited to this approach. Future studies into both costs and quality aspects of this exponentially growing health service diagnostic test are urgently needed in paediatric sleep centres across the UK.
Research: We thank the UK Down Syndrome Medical Interest group as well as the Down Syndrome Association for their help with recruiting children to the study and to paediatricians across the UK for help with recruitment, in particular to Dr Richard Tomlinson and the team at Exeter for acting as a satellite recruitment site. Most importantly, we thank the children and families for their enthusiasm to take part. We also acknowledge the Southampton NIHR Wellcome Trust Clinical Research Facility for their support. Clinical: We acknowledge the contribution of Michelle Davies, Natasha Liddle and Paula Lowe, sleep physiologists who assisted with data collection from the clinical sample at Southampton Children’s Hospital sleep laboratory.
HJE and CMH contributed equally.
Contributors RNK, HJE, CMH and FG conceptualised and designed the study. CMH originally developed the idea of the Down Syndrome Study and HJE set up the clinical home CRPG service in Southampton. HEE, JR, RNK, CMH, HJE, FG, JM, PG, MF, AJ and JCG acquired the data. RMP, CMH, HJE, RNK and FG analysed and interpreted the data. RNK, FG, CMH and HJE drafted the paper. CMH and HJE are joint last authors.
Funding Research reported in this paper was funded by Action Medical Research and the Garfield Weston Foundation (grant reference 2040).
Competing interests None declared.
Patient consent Not required.
Ethics approval The research study was approved by the UK National Research Ethics Committee (reference 13/SC/0106).
Provenance and peer review Not commissioned; externally peer reviewed.
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