Assessment of sleep-disordered breathing in pediatric neuromuscular diseases

Sleep Disordered Breathing in Children with Neuromuscular Disease

Sleep disordered breathing (SDB) in children with neuromuscular disease (NMD) is more prevalent compared to the general population, and often manifests as sleep-related hypoventilation, sleep-related hypoxemia, obstructive sleep apnea, central sleep apnea, and/or disordered control of breathing. Other sleep problems include, sleep fragmentation, abnormal sleep architecture, and nocturnal seizures in certain neuromuscular diseases. The manifestation of sleep disordered breathing in children depends on the extent, type, and progression of neuromuscular weakness, and in some instances, may be the first sign of a neuromuscular weakness leading to diagnosis of an NMD. In-lab diagnostic polysomnography (PSG) remains the gold standard for the diagnosis of sleep disordered breathing in children, but poses several challenges, including access to many children with neuromuscular disease who are non-ambulatory. If SDB is untreated, it can result in significant morbidity and mortality. Hence, we aimed to perform a comprehensive review of the literature of SDB in children with NMD. This review includes pathophysiological changes during sleep, clinical evaluation, diagnosis, challenges in interpreting PSG data using American Academy of Sleep (AASM) diagnostic criteria, management of SDB, and suggests areas for future research.

Alternatives to Polysomnography for the Diagnosis of Pediatric Obstructive Sleep Apnea

Diagnosis of obstructive sleep apnea (OSA) in children with sleep-disordered breathing (SDB) requires hospital-based, overnight level I polysomnography (PSG). Obtaining a level I PSG can be challenging for children and their caregivers due to the costs, barriers to access, and associated discomfort. Less burdensome methods that approximate pediatric PSG data are needed. The goal of this review is to evaluate and discuss alternatives for evaluating pediatric SDB. To date, wearable devices, single-channel recordings, and home-based PSG have not been validated as suitable replacements for PSG. However, they may play a role in risk stratification or as screening tools for pediatric OSA. Further studies are needed to determine if the combined use of these metrics could predict OSA.

Noninvasive respiratory assistance as aid for respiratory care in neuromuscular disorders

Chronic respiratory failure is a common complication of neuromuscular disease. The use of noninvasive ventilation and mechanically assisted cough can reduce symptoms of hypoventilation, slow lung function decline, improve sleep quality, and in some cases prolong survival in patients with neuromuscular disease. In this article, we review indications for the initiation of noninvasive ventilation and mechanically assisted cough as well as provide recommendations for settings and titration. We discuss the evidence supporting the use of noninvasive ventilation as an adjunct to rehabilitation in patients with neuromuscular disease. Lastly, we review the ethical considerations that are relevant to decisions regarding initiation and cessation of noninvasive ventilation. While noninvasive ventilation and mechanically assisted cough have become standards of care in many forms of neuromuscular disease, most current recommendations are based on expert opinion rather than much-needed data from prospective clinical trials and we emphasize topics requiring future research.

Pulmonological issues

Pediatric leukodystrophies are rare neurodegenerative diseases involving multiple systems. Each form has unique neurologic features but are characterized by encephalopathy with accompanying impairments evidenced in reflexes, muscle tone and movement control. Weakness of expiratory, inspiratory, and upper airway muscles may lead to impaired airway secretion clearance resulting in recurrent respiratory infections, dysphagia, sleep-disordered breathing, restrictive lung disease, and ultimately chronic respiratory insufficiency.

Daytime predictors of nocturnal hypercapnic hypoventilation in children with neuromuscular disorders

OBJECTIVES

To examine objective daytime predictors of nocturnal hypercapnic hypoventilation (NHH) and identify a forced vital capacity (FVC) z-score cut off that predicts NHH using the 2012 Global Lung Function Initiative (GLI) reference equations in pediatric neuromuscular patients.

DESIGN

Single-centre retrospective medical record review.

SETTING

Tertiary pediatric hospital in Australia.

PATIENTS

Children (<18 years old) with a neuromuscular disorder (NMD) who had a diagnostic sleep study over a 5-year period.

RESULTS

Fifty children were included, median age 11.9 years (interquartile range [IQR]: 4.5-14.3). The majority of children had a diagnosis of Duchenne Muscular Dystrophy (32%). NHH was diagnosed in 18 children (36%). Multivariate logistic regression analysis performed for the entire cohort confirmed a statistically significant association between NHH and scoliosis (odds ratio [OR]: 3.3, p = 0.03), but not age (OR: 1.01, p = 0.26), body mass index z-score (OR: 0.86, p = 0.26) or use of a wheelchair for mobility (OR: 1.25, p = 0.72). For the subset of 29 children who had spirometry testing (median age 12.9 years [IQR: 10.2-14.3]), FVC z-score was the only statistically significant predictor of NHH (OR: 0.45, p = 0.02). NHH was predicted by an FVC z-score <-3.24 (sensitivity 78%, specificity 73%), or FVC <60% predicted (sensitivity 78%, specificity 73%). There was a strong positive correlation between FVC and forced expiratory volume in 1 s z-scores (r_p  = 0.98, p = 0.00) and FVC and peak expiratory flow  z-scores (r_p  = 0.72, p = 0.00).

CONCLUSION

Children with a NMD and scoliosis or a lower FVC z-score have increased odds of having NHH.

Assessment of Nocturnal Hypoventilation by Different Methods and Definitions in Children with Neuromuscular Disease: Oxycapnography and Blood Gas Analysis

Objective

To investigate whether partial arterial carbon dioxide pressure (PaCO₂) level in arterial blood gas analysis that was used to predict nocturnal hypoventilation (NH) is concordant with nocturnal end-tidal CO₂ (PetCO₂) measurement obtained by a noninvasive method of oxycapnography in children with neuromuscular disease (NMD).

Methods

Twenty-one patients aged 6-18 years with a confirmed diagnosis of NMD were enrolled. Each patient underwent a nocturnal oxycapnography study using an orinasal probe and a pulse oximetry finger probe to record PetCO₂, oxygen saturation (SpO₂), pulse rate, and respiratory rate. Arterial blood gas analysis was performed to record PaCO₂ levels on three occasions at night (23:00 pm, 03:00 am, 07:00 am).

Results

The mean overnight PaCO₂ level of the three blood gas analyses (mean PaCO₂noct) was 41.78±4.69 mmHg. A significant change was observed between mean PaCO₂ 23:00 and PaCO₂ 07:00 levels (p=0.032). There was no significant difference between PaCO₂, PetCO₂, and SpO₂ levels in the NMD group. The interclass correlation coefficient between PaCO₂ 07:00 and PetCO₂ levels was 0.791 (95% CI: 0.533-0.923); the interclass correlation coefficient between overnight mean PaCO₂ and PetCO₂ levels was 0.811 (95% CI:0.533-0.923).

Conclusion

Our study indicates that nocturnal PetCO₂ and PaCO₂ levels were statistically comparable but the use of PaCO₂ alone is not adequate to make an early diagnosis of NH in NMD. There is a need for making more restrictive definitions for NH, and conducting studies with larger study populations to reach an agreement on the best definition of hypoventilation, and updating consensus guidelines.

Nocturnal oximetry in the diagnosis of obstructive sleep apnea syndrome in potentially hypoxic patients due to neuromuscular diseases

INTRODUCTION

Polysomnography is the recommended method for the diagnosis of obstructive sleep apnea (OSA); however, it is expensive, uncomfortable, and inaccessible. Alternative diagnostic methods are necessary, and Nocturnal Oximetry (NO) has proven to be reliable. Nevertheless, there have been doubts about its accuracy in patients with a history of hypoxia. Hence, the objective of this study was to evaluate the performance of NO in patients with neuromuscular diseases (NMD).

METHOD

This was a cross-sectional study in patients with NMD suspected of having OSA. We performed a statistical analysis using Spearman's correlation coefficients (SCCs). We used the value of the area under the ROC curve (AUCROC), just as we calculated the sensitivities (Sens) and specificities (Spec) for the chosen variables.

RESULTS

The sample comprised 41 patients; 51.2% with muscular dystrophies and 48.8% with motor neuron diseases, with a predominance of men (63.4%). Median age was 42 (19.7-55) years, body mass index (BMI) was 27.9 (23.8-32) kg/m2, forced vital capacity was 67% (54%-76.5%), and maximum inspiratory pressure was-60 cmH2O (-87.5 to -50). The prevalence of OSA was 75.7%. We analyzed and selected the best four oximetric variables with the following performance in identifying the apnea/hypopnea index >5/h, ODI3/2, cutoff>5/h, AUCROC 0.919, Sens 82.3%, Spec 91.7%; ODI3/5, cutoff>11.2/h, AUCROC 0.904, Sens 82.3%, Spec 87.5%; ODI4/5, cutoff>6.02, AUCROC 0.839, Sens 70.6%, Spec 91.6%, and ODI5/5, cutoff>0.87/h, AUCROC 0.870, Sens 94.1%, and Spec 70.8%.

CONCLUSION

NO can be used as a diagnostic tool for OSA, even in patients with neuromuscular diseases and potentially hypoxic diseases.

Sleep disordered breathing: Assessment and therapy in the age of emerging neuromuscular therapies

The term neuromuscular disease (NMD) encompasses a large variety of disorders that result in abnormal muscle function. Although it may be conventional to relate the use of this term to the most common muscular diseases (Duchenne muscular dystrophy [DMD], spinal muscular atrophy [SMA], and amyotrophic lateral sclerosis, etc), it is important to extend the term to pathologies manifested by severe neurologic (brain and spinal cord) malformations and injuries. In many of these scenarios, there are common mechanisms that contribute to sleep disordered breathing (SDB) and respiratory insufficiency although comorbidities may be somewhat different. Advances in the understanding of these diseases and their natural history, and increasing availability of mechanical ventilation to these patients have improved survival. The development of novel genetic and molecular therapies (as in the cases of DMD, SMA, and X-linked myotubular myopathy) provides an opportunity to use SDB as a reasonable outcome measure while also allowing the use of polysomnography as a validation tool in the assessments of effectiveness of therapies. We seek to provide an understanding of SDB in NMDs, and in the same light, would like to begin the conversation of thinking about weaning respiratory support when possible.

Management of respiratory complications and rehabilitation in individuals with muscular dystrophies: 1st Consensus Conference report from UILDM - Italian Muscular Dystrophy Association (Milan, January 25-26, 2019)

Respiratory complications are common in the patient with muscular dystrophy. The periodic clinical and instrumental respiratory evaluation is extremely important. Despite the presence in the literature of updated guidelines, patient associations often report lack of knowledge of these pathologies, particularly in peripheral hospitals. The purpose of this work, inspired by the Italian Muscular Dystrophy Association (UILDM) is to improve management of respiratory problems necessary for the management of these patients complex. To this end, the main items that the specialist can meet in the follow-up of these pathologies have been analyzed and discussed, among which the respiratory basal evaluation, the criteria of adaptation to non-invasive ventilation, management of bronchial secretions, situations of respiratory emergency, indications for tracheostomy and the subject of advance directives of treatment (DAT).

The impact of polysomnograms and family-centred decision making in children with medical complexity

Objectives

To determine whether a change in clinical management (e.g., new tracheostomy or adenotonsillectomy) occurred following a polysomnogram (PSG) in children with medical complexity (CMC) and to explore whether families’ goals of care (regarding results and treatment implications) were discussed prior to the completion of a PSG.

Methods

All CMC enrolled in a complex care program at the Hospital for Sick Children, Canada, who underwent a baseline PSG from 2009 to 2015 were identified. Exclusion criteria included (1) PSGs for ventilation titration and (2) PSGs outside the study time frame. Health records were retrospectively reviewed to determine demographics, medical histories, families’ wishes, PSG results, and their impact on clinical care. Descriptive statistics were used to summarize results.

Results

Of 145 patients identified, 96 patients met inclusion criteria. Fifty (52%) were male. Median age was 3 years. Forty-eight (50%) were diagnosed with clinically significant (i.e., moderate to severe obstructive sleep apnea, central sleep apnea, and/or hypoventilation) sleep-related breathing disorders. Of those diagnosed, 9 (19%) had surgery, 25 (52%) underwent respiratory technology initiation, and 3 (6%) underwent both. In the remaining 11 (23%) patients, treatment was either considered too risky or did not align with the families’ wishes. Only 3 of 96 patients had clear documentation of their families’ wishes prior to PSG completion.

Conclusion

Recognizing the burden of medical tests for both the child and the health care system, a process of shared-decision making that includes clarifying a family’s wishes may be prudent prior to conducting a PSG.

Respiratory Complications of Pediatric Neuromuscular Diseases

Respiration is an event of oxygen consumption and carbon dioxide production. Respiratory failure is common in pediatric neuromuscular diseases and the main cause of morbidity and mortality. It is a consequence of lung failure, ventilatory pump failure, or their combination. Lung failure often is due to chronic aspiration either from above or from below. It may lead to end-stage lung disease. Ventilatory pump failure is caused by increased respiratory load and progressive respiratory muscles weakness. This article reviews the normal function of the respiratory pump, general pathophysiology issues, abnormalities in the more common neuromuscular conditions and noninvasive interventions.

Volume-assured pressure support mode for noninvasive ventilation: can it improve overnight adherence in children with neuromuscular disease?

Purpose

Volume-assured pressure support in noninvasive ventilation (VAPS-NIV) is a newer mode providing automatic pressure support adjustment to ensure a constant alveolar ventilation. Previous studies have shown that NIV effectiveness depends on patient adherence and tolerance. The aim of this study was to determine the adherence and efficacy of VAPS-NIV compared to spontaneous-time (S/T) mode in pediatric patients with neuromuscular disease (NMD).

Methods

This was a prospective observational study. Children with NMD who utilized NIV at home for ≥ 3 months were recruited from the Long-term ventilation clinic at The Hospital for Sick Children, Toronto, Canada, from July 1, 2015, to July 1, 2019. Baseline characteristics, date of initiation of NIV, and pulmonary function tests were recorded. Polysomnogram (PSG) data and adherence were recorded and analyzed comparing VAPS and S/T modes.

Results

Twenty children with NMD (17 male, 85%) were enrolled. The mean (SD) age at initiation of NIV was 11.6 ± 4.6 years. The median (IQR) duration of ventilation was 1.36 (0.80–2.98) years. The mean average daily usage and the median daily usage for VAPS mode and S/T mode were 8.4 ± 1.6 versus 7.2 ± 2.5 h (p = 0.012) and 8.6 ± 1.4 versus 7.8 ± 2.1 h (p = 0.022), respectively. There was no difference in sleep architecture, gas exchange, or parent proxy report of NIV tolerance between S/T and VAPS modes.

Conclusion

VAPS was associated with an improvement in adherence to therapy in children with NMD compared to S/T mode. Longitudinal studies are required to evaluate long-term clinical outcomes using VAPS mode in children with NMD.

Supplementary Information

The online version contains supplementary material available at 10.1007/s11325-021-02288-1.

Assessment and treatment of pediatric obstructive sleep apnea in Canada: history and current state of affairs

AIM

To highlight Canada's contributions to the assessment and treatment of pediatric obstructive sleep apnea as well as outline the current state of pediatric obstructive sleep apnea in Canada.

METHODS

A search was conducted in MEDLINE (Ovid) using Medical Subject Headings (MeSH) and free-text terms for 'child' and 'obstructive sleep apnea' with subsequent 'human' limit. The results were reviewed to identify publications where any author's listed a Canadian institution.

RESULTS

Canadian contributions to the field of pediatric obstructive sleep apnea have grown over the last 30 years with an increase in number of contributors and centres. Much of the early work stemmed from McGill University with important contributions in examining alternatives to polysomnography and post-adenotonsillectomy respiratory compromise. Today, contributors from centres across the country are engaged in the field and come from a greater diversity of disciplines. With continued challenges and opportunities, Canada will continue to help advance the field of pediatric OSA.

CONCLUSION

Canada has a strong community of people invested in continuing to work to improve the lives of Canadian children with pediatric OSA.

The Accuracy of an Ambulatory Level III Sleep Study Compared to a Level I Sleep Study for the Diagnosis of Sleep-Disordered Breathing in Children With Neuromuscular Disease

STUDY OBJECTIVES

Polysomnography (PSG) surveillance recommendations are not being met for children with neuromuscular disease (NMD) because of limited diagnostic facilities. We evaluated the diagnostic accuracy of an ambulatory level III device as compared to a level I PSG.

METHODS

A cross-sectional study was conducted at a tertiary pediatric institution. Eligibility criteria included: (1) children with NMD; (2) age 6 to 18 years; (3) booked for a clinically indicated overnight level I PSG. Participants were randomized to an overnight level I PSG followed by an ambulatory level III study with end tidal carbon dioxide (etCO₂) or vice versa. Sensitivity and specificity of the ambulatory level III device to diagnose sleep-disordered breathing (SDB) at an apnea-hypopnea index (AHI) cutoff of > 1.0 events/h was the primary outcome.

RESULTS

Moderate to severe SDB was found in 46% of participants (13/28). The device's sensitivity and specificity to detect SDB was 61.5% and 86.7%, respectively. The positive predictive value of the level III study was 80.0% and the negative predictive value was 72.0%. Fifty percent of the cohort were either missing or had incomplete or falsely low ambulatory etCO₂ data.

CONCLUSIONS

A level III device with etCO₂ is not yet able to be implemented in clinical practice as a diagnostic tool for SDB in pediatric patients with NMD.

COMMENTARY

A commentary on this article appears in this issue on page 1973.

Identification of sleep hypoventilation in young individuals with Becker muscular dystrophy: A pilot study

AIM

To report on sleep hypercapnia in Becker muscular dystrophy (BMD) at earlier stages than ever recognized.

SUBJECTS AND METHODS

This retrospective study examined nocturnal hypercapnia in six young Becker muscular dystrophy (BMD) patients with deletions of one or more exons of DMD gene. Clinical information, consecutive data on forced vital capacity (FVC%), forced expiratory volume in one second (FEV1%), peak expiratory flow (PEF%), peak cough flow (PCF), average PCO₂ in all-night monitoring, and left ventricular ejection fraction (LVEF) were reviewed.

RESULTS

In five BMD patients, including three who were still ambulant, nocturnal average PCO₂ was elevated to >45 mmHg at 12-31 years of age. Noninvasive positive pressure ventilation was initiated in four patients. Gradual declines in FVC% and PEF% were evident in one BMD patient with exon 3-7 deletion, whereas these functions did not change in the remaining BMD patients. PCF, FEV1%, and LVEF were less informative for the assessment of respiratory function in this patient series.

CONCLUSION

Sleep hypercapnia was present in certain BMD patients, which was unexpected from the routine pulmonary function tests. Individualized assessment of nocturnal PCO₂, partly based on the deletion types, should be further explored in the clinical practice of BMD patients.

Detection of early nocturnal hypoventilation in neuromuscular disorders

Objective Nocturnal hypoventilation (NH) is a complication of respiratory involvement in neuromuscular disorders (NMD) that can evolve into symptomatic daytime hypercapnia if not treated proactively with non-invasive ventilation. This study aimed to assess whether NH can be detected in the absence of other signs of nocturnal altered gas exchange. Methods We performed nocturnal transcutaneous coupled (tc) pCO2/SpO2 monitoring in 46 consecutive cases of paediatric-onset NMD with a restrictive respiratory defect (forced vital capacity < 60%). Nocturnal hypoventilation was defined as tcPCO2 > 50 mmHg for > 25% of recorded time, and hypoxemia as tcSpO2 < 88% for > 5 minutes. Daytime symptoms and bicarbonate were recorded after overnight monitoring. Results Twenty-nine of 46 consecutive patients showed NH. Twenty-three patients did not have nocturnal hypoxemia and 18 were clinically asymptomatic. In 20 patients, PaCO2 in daytime blood samples was normal. Finally, 13/29 patients with NH had isolated nocturnal hypercapnia without nocturnal hypoxia, clinical NH symptoms, or daytime hypercapnia. Conclusions Paediatric patients with NMD can develop NH in the absence of clinical symptoms or significant nocturnal desaturation. Therefore, monitoring of NH should be included among nocturnal respiratory assessments of these patients as an additional tool to determine when to commence non-invasive ventilation.

Adenotonsillectomy for Obstructive Sleep Apnea in Children with Complex Chronic Conditions

Objective To estimate the prevalence of persistent obstructive sleep apnea postadenotonsillectomy in children with complex chronic conditions. Study Design A retrospective cohort study. Setting The Hospital for Sick Children Sleep laboratory. Subjects Children ≤18 years of age who had moderate to severe obstructive sleep apnea and had polysomnography pre- and postadenotonsillectomy. Methods Medical and polysomnographic data were reviewed. The prevalence of persistent obstructive sleep apnea postadenotonsillectomy was determined for the following groups: no complex chronic conditions, single-system complex chronic conditions, and multisystem complex chronic conditions. Results We reviewed data of 133 (84 male) children. Their mean (standard deviation) age was 5.5 (3.8) years. The persistent obstructive sleep apnea rate postadenotonsillectomy was highest in children with multisystem complex chronic conditions (57%), intermediate in children with single-system complex chronic conditions (29%), and lowest in children without complex chronic conditions (15%), P = .0004. The odds (confidence interval) of having persistent obstructive sleep apnea postadenotonsillectomy was 7.42 (2.16-25.51) times higher in children with multisystem complex chronic conditions vs no complex chronic conditions and 3.35 (1.16-9.64) times higher in children with multisystem complex chronic conditions vs single-system complex chronic conditions. Conclusions Although adenotonsillectomy is considered first-line therapy in healthy children older than 2 years for the treatment of obstructive sleep apnea, there is a significantly greater risk of persistent obstructive sleep apnea postadenotonsillectomy in children with complex chronic conditions. Therefore, other surgical procedures or nonsurgical management may need to be considered as first-line treatment for this cohort.

Respiratory Care Considerations for Children with Medical Complexity

Children with medical complexity (CMC) are a growing population of diagnostically heterogeneous children characterized by chronic conditions affecting multiple organ systems, the use of medical technology at home as well as intensive healthcare service utilization. Many of these children will experience either a respiratory-related complication and/or they will become established on respiratory technology at home during their care trajectory. Therefore, healthcare providers need to be familiar with the respiratory related complications commonly experienced by CMC as well as the indications, technical and safety considerations and potential complications that may arise when caring for CMC using respiratory technology at home. This review will outline the most common respiratory disease manifestations experienced by CMC, and discuss various respiratory-related treatment options that can be considered, including tracheostomy, invasive and non-invasive ventilation, as well as airway clearance techniques. The caregiver requirements associated with caring for CMC using respiratory technology at home will also be reviewed.

Establishing a Role for Polysomnography in Hospitalized Children

BACKGROUND

Children with medical complexity have a high prevalence of sleep disorders. However, outpatient polysomnography to evaluate for these conditions may be difficult to perform because of lack of skilled nursing care. The aim of this study was to explore polysomnography indications in hospitalized children and assess its impact on patient care.

METHODS

Data from 85 inpatient polysomnographies of 70 children hospitalized between March and December 2014 were retrospectively collected.

RESULTS

Sixty percent of patients were boys with ages 6.5 ± 6 years. Chronic respiratory failure was present in 33.8%, airway obstruction due to defects of the tracheobronchial tree or craniofacial abnormalities in 54.3%, neurological complications of the perinatal period in 22.9%, genetic syndromes and neurodegenerative disorders in 31.4%, congenital myopathies in 5.7%, metabolic diseases in 4.3% and congenital cyanotic heart defects in 4.3%. Indications for polysomnography included assessment of chronic pulmonary disease (60%), ventilator requirements (41.2%), apnea/desaturation (23.5%), and acute life-threatening events (1.2%). Abnormal results were found in 89.4%. The observed diagnosis was obstructive sleep apnea in 64.7%, signs of chronic lung disease in 34.1%, hypoventilation in 9.4%, periodic breathing in 3.5%, and periodic limb movement of sleep in 4.7%. The following interventions were performed: adjustment of ventilator parameters (45.8%), positive airway pressure initiation (24.7%), otorhinolaryngology referral (30.6%), supraglottoplasty (2.4%), tracheostomy decannulation (2.4%), and tracheostomy placement (3.5%). Nine patients had available follow-up polysomnograms, all showing improvement in sleep variables after adherence to recommended interventions.

CONCLUSIONS

In individuals with complex medical disorders, inpatient polysomnographies give invaluable information to guide immediate medical decision making and should be strongly considered if resources allow this.

Early Life Exposure to Chronic Intermittent Hypoxia Primes Increased Susceptibility to Hypoxia-Induced Weakness in Rat Sternohyoid Muscle during Adulthood

Intermittent hypoxia is a feature of apnea of prematurity (AOP), chronic lung disease, and sleep apnea. Despite the clinical relevance, the long-term effects of hypoxic exposure in early life on respiratory control are not well defined. We recently reported that exposure to chronic intermittent hypoxia (CIH) during postnatal development (pCIH) causes upper airway muscle weakness in both sexes, which persists for several weeks. We sought to examine if there are persistent sex-dependent effects of pCIH on respiratory muscle function into adulthood and/or increased susceptibility to re-exposure to CIH in adulthood in animals previously exposed to CIH during postnatal development. We hypothesized that pCIH would cause long-lasting muscle impairment and increased susceptibility to subsequent hypoxia. Within 24 h of delivery, pups and their respective dams were exposed to CIH: 90 s of hypoxia reaching 5% O2 at nadir; once every 5 min, 8 h per day for 3 weeks. Sham groups were exposed to normoxia in parallel. Three groups were studied: sham; pCIH; and pCIH combined with adult CIH (p+aCIH), where a subset of the pCIH-exposed pups were re-exposed to the same CIH paradigm beginning at 13 weeks. Following gas exposures, sternohyoid and diaphragm muscle isometric contractile and endurance properties were examined ex vivo. There was no apparent lasting effect of pCIH on respiratory muscle function in adults. However, in both males and females, re-exposure to CIH in adulthood in pCIH-exposed animals caused sternohyoid (but not diaphragm) weakness. Exposure to this paradigm of CIH in adulthood alone had no effect on muscle function. Persistent susceptibility in pCIH-exposed airway dilator muscle to subsequent hypoxic insult may have implications for the control of airway patency in adult humans exposed to intermittent hypoxic stress during early life.

Facilitators and Barriers to Noninvasive Ventilation Adherence in Youth with Nocturnal Hypoventilation Secondary to Obesity or Neuromuscular Disease

OBJECTIVE

Many youth struggle with adherence to bilevel noninvasive ventilation (NIV), often shortly after initiation of treatment. Anecdotal evidence suggests youths with comorbid obesity struggle with adherence while youths with comorbid neuromuscular disease demonstrate better adherence rates. The objective of this study was to explore factors relating to bilevel NIV adherence, and to compare these between youths with underlying obesity or neuromuscular disease.

METHODS

An exploratory qualitative approach was used to examine youth and caregivers' experiences with and perceptions of bilevel NIV. Semi-structured interviews (n = 16) of caregivers and youths were conducted. Youths 12 years and older with nocturnal hypoventilation diagnosed on polysomnography and managed with bilevel NIV, with either concurrent obesity or neuromuscular disease were included. Thematic analysis of interview data was conducted using qualitative analysis software.

RESULTS

Factors associated with positive bilevel NIV adherence included previous encouraging experiences with therapy; subjective symptom improvement; familiarity with medical treatments; understanding of nocturnal hypoventilation and its consequences; family and health-care team support; and early adaptation to treatments. Factors associated with poor bilevel NIV adherence included previous negative experiences with therapy, negative attitude towards therapy; difficulty adapting; perceived lack of support from family or health-care team; fear/embarrassment regarding treatment; caregivers not being health-minded; technical issues; side effects; and a lack of subjective symptom improvement.

CONCLUSIONS

The dimensions which most affect adherence to bilevel NIV are those which contribute to youths' conception of feeling "well" or "unwell." Adherence to treatment may hinge largely on the way in which NIV is initially experienced and framed.

COMMENTARY

A commentary on this article appears in this issue on page 1355.

Paediatric sleep resources in Canada: The scope of the problem

BACKGROUND

Sleep-disordered breathing (SDB) is prevalent in children and is associated with significant comorbidity.

OBJECTIVES

To describe paediatric sleep physician and diagnostic testing resources for SDB in Canadian children.

METHODS

A 38-item, Internet-based survey was sent to the 32 members of the Canadian Pediatric Sleep Network (CPSN). A shorter telephone survey was administered to all 182 non-CPSN sleep laboratories across Canada.

RESULTS

Responses were obtained from 29 of 31 (91%) CPSN members and 121 of 182 (66%) non-CPSN sleep facilities. Sixty-seven of 121 (55%) of the responding non-CPSN facilities reported that they see children <18 years of age. Thirty-six of 121 (30%) and 23 of 121 (19%), respectively, see children ≤12 years of age or ≤8 years of age. Marked disparities across provinces/territories were observed, with no practitioners or polysomnography in the Yukon, Northwest Territories, Nunavut, Saskatchewan, New Brunswick, Prince Edward Island, and Newfoundland and Labrador. Alberta has the smallest ratio of children to practitioners (approximately 167,000 to 1) and Ontario has the smallest ratio of children to polysomnograms performed per year (approximately 487,000 to 1). Reported wait times for polysomnography ranged from <1 month, to 1.5 to 2 years. In paediatric tertiary care centres, the number of polysomnograms performed per year ranged from 55 to 700 (median 480) and in other laboratories the range was 400 to 4000 (median 1100).

CONCLUSIONS

The present study demonstrates a significant lack of resources and services for paediatric SDB care across Canada, with pronounced geographical disparities. Even if only affected children were tested with polysomnography, the authors estimate there are 7.5 times more children with SDB than current testing capacity.

Overview of paediatric neuromuscular disorders and related pulmonary issues: diagnostic and therapeutic considerations

Pulmonary compromise is common in neuromuscular disease. Respiratory failure may be a presenting feature of neuromuscular disease and remains a major cause of morbidity and mortality. This article will review the current understanding of the more commonly encountered neuromuscular disorders in childhood and emphasize related pulmonary issues.