Sleep-related Hypoventilation Research Articles

Knockdown of PHOX2B in the retrotrapezoid nucleus reduces the central CO2 chemoreflex in rats

PHOX2B is a transcription factor essential for the development of different classes of neurons in the central and peripheral nervous system. Heterozygous mutations in the PHOX2B coding region are responsible for the occurrence of Congenital Central Hypoventilation Syndrome (CCHS), a rare neurological disorder characterised by inadequate chemosensitivity and life-threatening sleep-related hypoventilation. Animal studies suggest that chemoreflex defects are caused in part by the improper development or function of PHOX2B expressing neurons in the retrotrapezoid nucleus (RTN), a central hub for CO2 chemosensitivity. Although the function of PHOX2B in rodents during development is well established, its role in the adult respiratory network remains unknown. In this study, we investigated whether reduction in PHOX2B expression in chemosensitive neuromedin-B (NMB) expressing neurons in the RTN altered respiratory function. Four weeks following local RTN injection of a lentiviral vector expressing the short hairpin RNA (shRNA) targeting Phox2b mRNA, a reduction of PHOX2B expression was observed in Nmb neurons compared to both naive rats and rats injected with the non-target shRNA. PHOX2B knockdown did not affect breathing in room air or under hypoxia, but ventilation was significantly impaired during hypercapnia. PHOX2B knockdown did not alter Nmb expression but it was associated with reduced expression of both Task2 and Gpr4, two CO2/pH sensors in the RTN. We conclude that PHOX2B in the adult brain has an important role in CO2 chemoreception and reduced PHOX2B expression in CCHS beyond the developmental period may contribute to the impaired central chemoreflex function.

Knockdown of PHOX2B in the retrotrapezoid nucleus reduces the central CO2 chemoreflex in rats.

PHOX2B is a transcription factor essential for the development of different classes of neurons in the central and peripheral nervous system. Heterozygous mutations in the PHOX2B coding region are responsible for the occurrence of Congenital Central Hypoventilation Syndrome (CCHS), a rare neurological disorder characterised by inadequate chemosensitivity and life-threatening sleep-related hypoventilation. Animal studies suggest that chemoreflex defects are caused in part by the improper development or function of PHOX2B expressing neurons in the retrotrapezoid nucleus (RTN), a central hub for CO2 chemosensitivity. Although the function of PHOX2B in rodents during development is well established, its role in the adult respiratory network remains unknown. In this study, we investigated whether reduction in PHOX2B expression in chemosensitive neuromedin-B (NMB) expressing neurons in the RTN altered respiratory function. Four weeks following local RTN injection of a lentiviral vector expressing the short hairpin RNA (shRNA) targeting Phox2b mRNA, a reduction of PHOX2B expression was observed in Nmb neurons compared to both naive rats and rats injected with the non-target shRNA. PHOX2B knockdown did not affect breathing in room air or under hypoxia, but ventilation was significantly impaired during hypercapnia. PHOX2B knockdown did not alter Nmb expression but it was associated with reduced expression of both Task2 and Gpr4, two CO2/pH sensors in the RTN. We conclude that PHOX2B in the adult brain has an important role in CO2 chemoreception and reduced PHOX2B expression in CCHS beyond the developmental period may contribute to the impaired central chemoreflex function.

Prevalences of sleep-related breathing disorders and severity factors in chronic spinal cord injury and abled-bodied individuals undergoing rehabilitation: a comparative study.

The objective of this study is to discern distinguishing characteristics of sleep-related breathing disorders (SRBD) in individuals with chronic spinal cord injury (CSCI) compared to able-bodied participants (non-CSCI). Additionally, the study investigates factors associated with SRBD severity. This is a cross-sectional analysis of 123 able-bodied individuals, 40 tetraplegics, and 48 paraplegics, who underwent attended or partially supervised full polysomnography, for suspected SRBD, in a rehabilitation center. Polysomnographic, transcutaneous capnography, and clinical data were collected and compared between the groups. Among tetraplegics prevailed apnea-hypopnea index ≥ 30 (67.5%, p=0.003), central apnea (17.5%, p=0.007), and higher oxygen-desaturation index (80.0%, p=0.01). Sleep-related hypoventilation was present in 15,4% of tetraplegics and 15,8% of paraplegics, compared to 3,2% in able-bodied participants (p=0.05). In the able-bodied and paraplegic groups, snoring and neck circumference were positively correlated with obstructive sleep apnea (OSA) severity. A positive correlation between waist circumference and OSA severity was identified in all groups, and multivariate logistic regression analysis showed that loud snoring and waist circumference had the greatest impact on OSA severity. Severe OSA and Central Sleep Apnea prevailed in tetraplegic participants. Sleep-related hypoventilation was more common in tetraplegics and paraplegics compared to able-bodied participants. Loud snoring and waist circumference had an impact on OSA severity in all groups. We recommend the routine implementation of transcutaneous capnography in individuals with CSCI. We underscore the significance of conducting a comprehensive sleep assessment in the rehabilitation process of individuals with CSCI.

O070 Prevalence of central sleep apnoea in people with tetraplegic spinal cord injury: a retrospective analysis of research and clinical data

Abstract Study Objectives Over 80% of people with tetraplegia have sleep disordered breathing, but whether this is predominantly obstructive or central is unclear. This study aimed to estimate the prevalence of central sleep apnoea (CSA) in tetraplegia and the contributions of central, obstructive and hypopnoea respiratory events to sleep disordered breathing summary indices in tetraplegia. Methods Research and clinical data from 606 individuals with tetraplegia and full overnight polysomnography were collated. The proportions of different respiratory event types were calculated; overall and for mild, moderate, and severe disease. The prevalence of Predominant CSA (central apnoea index 5 and more central than obstructive apnoeas) and Any CSA (central apnoea index  5) was estimated. Prevalence of sleep-related hypoventilation was estimated in a clinical sub-cohort. Results Respiratory events were primarily hypopnoeas (71%), followed by obstructive (23%), central (4%) and mixed apnoeas (2%). As severity increased, the relative contribution of hypopnoeas and central apnoeas decreased, while that of obstructive apnoeas increased. The prevalence of Predominant CSA and Any CSA were 4.3% (26/606) and 8.4% (51/606) respectively. Being male, on opiates and having a high tetraplegic spinal cord injury were associated with CSA. Sleep-related hypoventilation was identified in 26% (26/113) of the clinical sub-cohort. Conclusions This is the largest study to characterize sleep disordered breathing in tetraplegia. It provides strong evidence that obstructive sleep apnoea is the predominant sleep disordered breathing type; 9-18 times more prevalent than CSA. The prevalence of CSA was estimated to be 4-8%, significantly lower than previously reported.

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.

Occurrence of sleep-disordered breathing in children with pulmonary hypertension.

Obstructive sleep apnea (OSA) has been associated with pulmonary hypertension (PH) through a complex and bidirectional relationship. The prevalence of OSA and other forms of sleep-disordered breathing (SDB) among children with PH is not well understood. A better understanding could help elucidate contributing factors for PH, guide diagnostic testing, and inform therapies. We therefore determined the proportion of SDB codiagnosis and OSA risk factors among a cohort of children with PH. Retrospective chart review was performed for children 0-21 years old with PH who underwent polysomnography (PSG) between 1 January2010 and 31 August2020. The primary outcome was OSA occurrence and risk based on demographics, diagnoses, and PH classification. The secondary outcome was occurrence and risk of other SDB diagnoses based on PH classification. Among 89 children identified, diagnoses included OSA (N = 79, 89%), central sleep apnea (N = 11, 12%), sleep-related hypoventilation (N = 6, 7%), and non-apneic hypoxemia (N = 28, 31%). Trisomy 21 diagnosis (N = 38, 43%) was associated with increased OSA risk (RR: 1.24, 95% CI: [1.09-1.42]) and age >12 months at PSG was associated with decreased OSA risk (N = 52, 58%, RR: 0.60, 95% CI: [0.45-0.81]). There was no difference in SDB risk based on Group 1 (N = 56, 63%) or Group 3 (N = 33, 37%) PH and no difference in OSA severity based on demographics and diagnoses. OSA was diagnosed among a majority of children with PH, and other SDB diagnoses were identified in a significant proportion of children. These findings support routine screening for SDB with PSGin children with PH.

Prevalence of central sleep apnea in people with tetraplegic spinal cord injury: a retrospective analysis of research and clinical data.

Over 80% of people with tetraplegia have sleep-disordered breathing (SDB), but whether this is predominantly obstructive or central is unclear. This study aimed to estimate the prevalence of central sleep apnea (CSA) in tetraplegia and the contributions of central, obstructive, and hypopnea respiratory events to SDB summary indices in tetraplegia. Research and clinical data from 606 individuals with tetraplegia and full overnight polysomnography were collated. The proportions of different respiratory event types were calculated; overall and for mild, moderate, and severe disease. The prevalence of Predominant CSA (Central Apnea Index [CAI] ≥ 5 and more central than obstructive apneas) and Any CSA (CAI ≥ 5) was estimated. Prevalence of sleep-related hypoventilation (SRH) was estimated in a clinical sub-cohort. Respiratory events were primarily hypopneas (71%), followed by obstructive (23%), central (4%), and mixed apneas (2%). As severity increased, the relative contribution of hypopneas and central apneas decreased, while that of obstructive apneas increased. The prevalence of Predominant CSA and Any CSA were 4.3% (26/606) and 8.4% (51/606) respectively. Being male, on opiates and having a high tetraplegic spinal cord injury were associated with CSA. SRH was identified in 26% (26/113) of the clinical sub-cohort. This is the largest study to characterize SDB in tetraplegia. It provides strong evidence that obstructive sleep apnea is the predominant SDB type; 9-18 times more prevalent than CSA. The prevalence of CSA was estimated to be 4%-8%, significantly lower than previously reported.

Insomnia and sleep-disordered breathing in FKRP-related limb-girdle muscular dystrophy R9. The Norwegian LGMDR9 cohort study (2020)

Limb-girdle muscular dystrophy R9 (LGMDR9) is a progressive and disabling genetic muscle disease. Sleep is relevant in the patient care as it impacts on health, functioning, and well-being. LGMDR9 may potentially affect sleep by physical or emotional symptoms, myalgia, or sleep-disordered breathing (SDB) through cardiorespiratory involvement. The objective was to investigate the occurrence of insomnia and unrecognized or untreated SDB in LGMDR9, associated factors, and relationships with fatigue and health-related quality of life (HRQoL). All 90 adults in a Norwegian LGMDR9 cohort received questionnaires on sleep, fatigue, and HRQoL. Forty-nine of them underwent clinical assessments and 26 without mask-based therapy for respiration disorders additionally underwent polysomnography (PSG) and capnometry. Among 77 questionnaire respondents, 31% received mask-based therapy. The prevalence of insomnia was 32% of both those with and without such therapy but was significantly increased in fatigued respondents (54% vs 21%). Insomnia levels correlated inversely with mental HRQoL. Among 26 PSG candidates, an apnea–hypopnea index (AHI) ≥ 5/h was observed in 16/26 subjects (≥ 15/h in 8/26) with median 6.8 obstructive apneas and 0.2 central apneas per hour of sleep. The AHI was related to advancing age and an ejection fraction < 50%. Sleep-related hypoventilation was detected in one subject. Fatigue severity did not correlate with motor function or nocturnal metrics of respiration or sleep but with Maximal Inspiratory Pressure (r = − 0.46). The results indicate that insomnia and SDB are underrecognized comorbidities in LGMDR9 and associated with HRQoL impairment and heart failure, respectively. We propose an increased attention to insomnia and SDB in the interdisciplinary care of LGMDR9. Insomnia and pulmonary function should be examined in fatigued patients.

1046 Severe hypoventilation in a child with rapid onset weight gain

Abstract Introduction Pediatric sleep-related hypoventilation is a clinical pattern in which ventilatory insufficiency occurs in the setting of either severe OSA (obstructive hypoventilation) or obesity hypoventilation (sleep related hypoventilation). We are reporting a case describing the management of overlapping obstructive hypoventilation due to uncontrolled severe OSA and pediatric obesity hypoventilation syndrome. Report of case(s) The patient is a full term African American 5 y/o male with past medical history of obesity and prediabetes who was referred to discuss sleep related problems after rapid onset of weight gain.He gained 76 lbs over 8-month period; during this time his aunt noticed apneic events with the development of loud snoring.Initial workup was negative for abnormal findings,MRI w/w/o was unremarkable and TSH, cortisol, GH, IGF-1 and prolactin were all within normal limits. X-ray bone age study showed skeletal age appropriate for patient's chronologic age.Upper airway exam showed severe tonsillar hypertrophy 3+ with Mallampati class 4.The diagnostic PSG demonstrated the presence of 12 obstructive, 151 central, and 61 mixed apneas.There were 214 hypopneas resulting in an Apnea\Hypopnea Index of 60.5 events per hour.Mean oxygen saturation was 91.3%.The lowest oxygen saturation during sleep was 64.0%.Time spent ≤88% oxygen saturation was 119.7 minutes (26.2%). End tidal CO2 range was between 50-100 mmHg for 30% of study.The titration study revealed that the optimal treatment modality was BiPAP ST. Conclusion This case focuses on a five-year-old male who experienced rapid onset weight gain and presented with snoring, excessive daytime sleepiness and apneic events and was found to have profound hypoventilation with hypopnea predominant severe obstructive sleep apnea.The initial differential diagnosis of pediatric sleep-related hypoventilation includes ROHHAD, congenital central hypoventilation syndrome, primary central sleep apnea and obesity hypoventilation syndrome.The most common cause of hypoventilation during sleep in children remains OSA.The stepwise approach to management in such a case includes tonsillectomy with adenoidectomy,along with use of BiPAP. After the T&amp;A the patient should have repeat PSG with capnography, if hypercarbia persists on post procedure PSG, he will need to continue BiPAP therapy with appropriate weight loss program. Early recognition evaluation, and treatment of obstructive sleep apnea in the pediatric population is imperative to prevent long-term consequences. Support (if any)

1034 A Rare Case of ROHHAD Syndrome

Abstract Introduction Early diagnosis of pediatric syndromes that are rare and involve multiple systems can be challenging. Rapid onset obesity, hypoventilation, hypothalamic dysfunction, and autonomic dysregulation characterizes ROHHAD syndrome which, if undiagnosed, can lead to potentially harmful outcomes including deferring radiological workup for a neural crest tumor (which has an over 50% association) and cardiopulmonary arrest. Report of case(s) A 10-year-old female with a history of obesity, precocious puberty, recurrent hypothermia, recurrent sodium derangements, bilateral ptosis, seizure disorder, and GERD initially presented to sleep clinic as a 4-year-old in 2017 when she recently began snoring with excessive daytime sleepiness as a result of rapid onset of weight gain. BMI at that time was 99th percentile and Epworth was 11. An in-lab polysomnography revealed severe OSA with AHI 26.4 events/hour; nocturnal hypoxemia with TS90 27% and O2 nadir 70%; and sleep related hypoventilation based on elevated pCO2 on end-tidal capnometry. Patient underwent adenotonsillectomy, revision adenoidectomy, and was started on CPAP before transitioning to BiPAP over the span of the next several years with serial polysomnographies ultimately showing significant improvement of sleep apnea with AHI 5.4 events/hour. Sleep-related hypoventilation, however, remained persistent with blood gases showing pCO2 as high as 89. PHOX2B gene testing was negative and secondary causes of hypoventilation were ruled out. During this time, she was also followed by Endocrinology for suspected hypothalamic dysfunction resulting in precocious puberty, deceleration of growth rate, sodium derangements. Autonomic dysfunction was also suspected due to recurrent hypothermia including a recent admission for Temperature &amp;lt; 95F and ophthalmologic abnormalities including bilateral ptosis. At a multidisciplinary care conference, a working diagnosis of ROHHAD syndrome was made based on the rapid onset of obesity, hypoventilation on sleep studies and CBGs, hypothalamic dysfunction, and autonomic degeneration. Workup for neural crest tumor with MRI chest and abdomen unremarkable. Outside academic consultation was sought for management which recommended shared decision-making regarding steroids, immunosuppressive therapy (eg rituximab, cyclophosphamide), and IVIG. Conclusion For ROHHAD syndrome, there are very few documented cases in the United States and there is no known laboratory marker; diagnosis remains clinical and takes multidisciplinary collaboration, education, and a high degree of suspicion. Support (if any)

0995 Sleep-related Hypoventilation in a 62-Year-Old Female with a Rare Genetic Neuromuscular Disorder

Abstract Introduction Central Core Myopathy (CCM) is a rare genetic neuromuscular disorder involving a mutation in the ‘Ryanodine Receptor’ (RyR1) gene, also known as the gatekeeper of calcium within the muscle cells. CCM typically manifests as slowly progressive proximal muscle weakness Currently, there is limited data regarding the management of nocturnal hypoventilation in adults with neuromuscular disorders. Report of case(s) We present a 62-year-old woman with CCM, as identified via RyR1 mutation (c14818G&amp;gt;A) on genetic testing, as well as muscle biopsy. This genotype is associated with &amp;lt; 10% respiratory muscle involvement. She presented to the sleep clinic with complaints of morning headaches, non-restorative sleep, and daytime sleepiness. Her polysomnogram (PSG) showed an overall Apnea-Hypopnea-Index in the normal range. However, there was a progressive increase in transcutaneous carbon dioxide levels (PtcCO2), reaching a peak of 53 mmHg during rapid eye movement (REM) sleep from 38 mmHg during wakefulness, consistent with sleep-related neuromuscular hypoventilation. On further evaluation, this patient had no evidence of neuromuscular restrictive lung physiology or overt diaphragmatic dysfunction, as suggested by &amp;lt; 20% variation in the supine forced vital capacity. Moreover, her negative inspiratory force (NIF) value was not less than negative 40. However, in the setting of her sleep-related symptoms and evidence of nocturnal hypoventilation, our team decided to trial non-invasive positive pressure ventilation (NIPPV). Since we had concerns about respiratory alkalosis in NREM sleep in the setting of normal body mass index, normal pulmonary function tests, and hypoventilation limited to REM sleep, the patient was sent for in-lab titration of pressures with measurement of PtcCO2 to appropriately recommend NIPPV settings. The study demonstrated bi-level positive airway pressure settings of IPAP 7 cmH20, EPAP 5 cmH20, and a backup rate of 12/min resulting in sustained eucarbia and steady PtcCO2 levels during both REM and NREM sleep. Conclusion This case highlights the importance of evaluation for nocturnal hypoventilation in symptomatic patients with rare neuromuscular disorders and the potential for symptomatic improvement with treatment with NIPPV. Moreover, the case demonstrates the importance of in-lab titration of pressure settings for NIPPV when hypoventilation is limited to REM sleep, due to concern for iatrogenic hyperventilation and respiratory alkalosis. Support (if any)

Average Volume-assured Pressure Support as Rescue Therapy after CPAP Failure in Pediatric Obstructive Sleep Apnea: A Retrospective Case Series Study.

Continuous positive airway pressure (CPAP) is frequently prescribed for patients with residual obstructive sleep apnea (OSA) following adenotonsillectomy. The goal was to examine the efficacy of noninvasive ventilation with average volume-assured pressure support (AVAPS) as a potential option for children with failed CPAP titration. In a single-center retrospective study, we included children aged 1-17 years, with polysomnographically confirmed OSA who underwent AVAPS titration following failed CPAP titration. In addition to describing the clinical characteristics of the included patients, we compared polysomnographic parameters before and after AVAPS. Nine patients met the inclusion criteria; out of them, 8 (89%) were males with an age range of 6.7 ± 3.9 years and a body mass index percentile of 81.0 ± 28.9. Reasons for failed CPAP titration were: 3 (33%) patients due to inability to control apnea-hypopnea index (AHI), 3 (33%) patients due to sleep-related hypoventilation, 2 (22%) patients due to treatment-emergent central sleep apnea, and 1 (11%) patient due to intolerance to CPAP. AVAPS resulted in a greater reduction in AHI than CPAP (reduction following CPAP = 24.6 ± 29.3, reduction following AVAPS = 42.5 ± 37.6, p = 0.008). All patients had resolution of the problems which caused CPAP failure. In this case a series of children with OSA and with failed CPAP titration, AVAPS resulted in a greater reduction in AHI compared with CPAP as well as resolution of the problems which caused CPAP failure.

Sleep disorders in patients with neuromuscular diseases

Neuromuscular diseases (NMD) may affect skeletal muscles, peripheral nerves, or motor endplates. Clinical symptoms comprise muscle weakness, which is often progressive, but also sensory disturbances, and primary or secondary pain. Sleep disturbances in NMD may result from insomnia due to immobility, pain, or sleep-related leg muscle cramps, but also restless legs syndrome and sleep-disordered breathing. Many NMD predispose to obstructive sleep apnea or progressive respiratory muscle weakness, which first manifests as sleep-related hypoventilation and eventually leads to chronic hypercapnic respiratory failure. The latter is crucial for overall prognosis in muscular dystrophies and myopathies, but even more so in motor neuron diseases such as amyotrophic lateral sclerosis and spinal muscular atrophy.

Outpatient Utilization of the RAM Cannula for Nasal Noninvasive Ventilation in Children.

The RAM cannula® consists of nasal prongs that can be used to administer oxygen, continuous, and bilevel positive airway pressure therapies. Studies have reported the efficacy and utility of the RAM cannula in inpatients requiring noninvasive ventilation (NIV); however, there is limited literature on the use of the RAM cannula to provide NIV in the outpatient setting. This study aimed to describe the clinical features and outcomes of children who used NIV via RAM cannula in the outpatient setting. Retrospective review. We conducted a retrospective review of children treated with outpatient NIV via RAM cannula at our institution between January 2010 and March 2023. The analyzed data included age, diagnoses, indications for NIV, duration of RAM cannula use, complications, and outcomes at 6 months. We identified 20 patients who used outpatient NIV via RAM cannula during the study period. The median age at initiation of NIV via RAM cannula was 5.8 months (IQR 2.4-9.9 months). Indications for NIV included sleep-related hypoventilation (15%), restrictive lung disease (25%), obstructive sleep apnea (45%), and chronic respiratory failure (50%), with 6 patients having ⩾2 indications for NIV. RAM cannula was utilized for inability to tolerate conventional NIV interfaces (80%), to alleviate dyspnea (60%), and to avoid tracheostomy (55%). Patients used NIV via RAM cannula for a median duration of 7.7 months (IQR 3.7-20.6 months). Patient outcomes included ongoing usage of RAM cannula (55%), changing to conventional NIV interfaces (15%) or oxygen (10%), weaning off respiratory support (5%), and death (15%). There were no complications related to using the RAM cannula. Our study demonstrates the utility of outpatient NIV via RAM cannula in children with a variety of diagnoses until clinical improvement or tolerance of conventional interfaces, and for avoidance of tracheostomy.

Moving toward standardization: physician reporting of sleep studies.

Lastra AC, Ingram D, Park J, etal. Moving toward standardization: physician reporting of sleep studies. J Clin Sleep Med. 2023;19(3):595-603.

Use of Positive Airway Pressure in the Treatment of Hypoventilation.

The treatment of chronic hypoventilation usually requires noninvasive ventilation. However, upper airway obstruction can lead to hypoventilation in conditions such as obesity-hypoventilation syndrome, or chronic obstructive lung diseases (overlap syndrome). In these situations, continuous positive airway pressure can be an effective therapeutic option. This article reviews the pathophysiology of sleep-related hypoventilation, discusses situations where treatment with continuous positive airway pressure is feasible and briefly outlines noninvasive ventilation modes and settings for the treatment of common sleep-related hypoventilation disorders.

Short-term cognitive loading deteriorates breathing pattern and gas exchange in adult patients with congenital central hypoventilation syndrome.

Human PHOX2B mutations result in life-threatening sleep-related hypoventilation (congenital central hypoventilation syndrome, CCHS). Most patients retain ventilatory activity when awake through a respiratory-related cortical network. We hypothesised that this need to mobilise cortical resources to breathe would lead to breathing-cognition interferences during cognitive loading. Seven adult CCHS patients (five women; median age 21) performed standard neuropsychological tests (paced auditory serial addition test - calculation capacity, working memory, sustained and divided attention; trail making test - visuospatial exploration capacity, cognitive processing speed, attentional flexibility; Corsi block-tapping test - visuospatial memory, short-term memory, working memory) during unassisted breathing and under ventilatory support. Ventilatory variables and transcutaneous haemoglobin oxygen saturation were recorded. Cortical connectivity changes between unassisted breathing and ventilatory support were assessed using electroencephalographic recordings (EEG). Baseline performances were lower than expected in individuals of this age. During unassisted breathing, cognitive loading coincided with increased breathing variability, and decreases in oxygen saturation inversely correlated with an increasing number of apnoeic cycles per minute (rho -0.46, 95% CI -0.76 to -0.06, p=0.01). During ventilatory support, cognitive tasks did not disrupt breathing pattern and were not associated with decreased oxygen saturation. Ventilatory support was associated with changes in EEG cortical connectivity but not with improved test performances. Acute cognitive loads induce oxygen desaturation in adult CCHS patients during unassisted breathing, but not under ventilatory support. This justifies considering the use of ventilatory support during mental tasks in CCHS patients to avoid repeated episodes of hypoxia.

P062 Agreement between arterial and capillary CO2 level in patients undergoing sleep study for suspected hypoventilation

Abstract Background Measurement of arterial CO2 (PaCO2) is the gold standard for diagnosis of sleep hypoventilation during polysomnography. However, arterial PaCO2 measurement is a labour-intensive and painful. Previous audit in our unit demonstrated ABGs are often delayed or omitted when requested. Continuous monitoring of transcutaneous carbon dioxide (TcCO2) is often used as a surrogate marker of PaCO2, however caution should be applied in interpreting TcCO2 due to the “sensor drift” phenomenon. Arterialized capillary blood gas (CBG) measurement has been described in various settings and is used in many respiratory units. Concordance with ABG and TcCO2, however, is poorly described in the literature. A retrospective review was performed to assess concordance of arterialized capillary CO2 level (PcCO2) with TcCO2 measured during routine polysomnography. Methods This is a retrospective audit of patients with provisional diagnosis of sleep-related hypoventilation syndrome who attended Sunshine Coast University Hospital Sleep Disorders Centre for overnight sleep studies. Continuous TcCO2 was monitored and arterialized PcCO2 measured at the outset and completion of study. CO2 results will be compared to assess concordance. Where an ABG was performed simultaneously with a CBG the concordance will be reported. Progress to Date Full results to follow. It is anticipated that 30-40 patients will be included. Few ABGs were performed. Anticipated outcome Initial evaluation suggests PcCO2 may be a viable alternative to ABG based on concordance with limited ABG data. PcCO2 may be superior to TcCO2 due to the common phenomenon of TcCO2 “drift”. A prospective study, utilising ABG, CBG and TcCO2 is needed.

Impact of sleep-related hypoventilation in patients with pleuroparenchymal fibroelastosis

BackgroundPleuroparenchymal fibroelastosis (PPFE) is a rare fibrosing lung disease with a predilection for the upper lobe and its progression causes hypoventilation, resulting in hypercapnia. Even though the association between sleep-related hypoventilation (SRH) and chronic obstructive pulmonary disease was well documented, its impact in patients with PPFE was not evaluated. The aim of this study is to clarify the impact of SRH on prognosis in PPFE.MethodsA retrospective review of the medical records of 52 patients with PPFE who underwent transcutaneous carbon dioxide monitoring during sleep was done.Patients were stratified into SRH (n = 28) and non-SRH (n = 24) groups based on American Academy of Sleep Medicine criteria. The impact of SRH on the prognosis of PPFE, as well as the clinical factors and comorbidities of PPFE associated with SRH, were evaluated.ResultsForced expiratory volume in the first second (FEV1), forced vital capacity (FVC), total lung capacity (TLC), and carbon monoxide diffusing capacity (DLco) in the SRH group were significantly lower than the non-SRH group (P < .01). Chronic pulmonary aspergillosis (CPA) was found at a higher rate in the SRH group (P = .02). The median survival time for SRH patients was 330 days, whereas roughly 80% of non-SRH patients were alive during the 3-year observation period (P < .01). Body mass index was a significant prognostic factor in PPFE patients with SRH (HR .78; 95% CI; .64–.94; P < .01). Home oxygen therapy (HOT) during the day and noninvasive positive pressure ventilation (NPPV) at night while sleeping tended to improve prognosis in the SRH group, as indicated by HR of .25 (P = .07).ConclusionsSRH may be a poor prognostic factor for PPFE. Additionally, SRH may modify susceptibility to Aspergillosis in patients with PPFE. HOT plus NPPV may improve the disease outcomes in patients with SRH.

Sleep-related breathing disorder in non-infectious pulmonary complications after pediatric allogeneic stem cell transplantation

BackgroundChronic lung problems are a rare but serious complication of allogeneic hematopoietic stem cell transplantation (HSCT). We studied clinical phenotypes and polysomnography appearance of breathing abnormality in late onset non-infectious pulmonary complications (NIPS).MethodsWe reviewed Finnish national reference database between the years 1999 and 2016. We identified 12 children with most severely decreased pulmonary function and performed polysomnography and 24 aged-matched controls out of 325 performed pediatric allogeneic HSCTs.ResultsAll patients with NIPS had severely decreased pulmonary function already at 6 months post HSCT with median FEV1 value 42% (interquartile range (IQR) 30–52%) of predicted normal values. Seven children had obstructive and five children more restrictive lung function. Children with obstructive lung function showed laborious breathing (7/7), decreased oxygenation and ventilation-to-perfusion mismatch (6/7), or REM-sleep-related hypoventilation (4/7) on polysomnography. Children with restrictive lung function (5/12) did not show sleep-related breathing disorder.ConclusionsChildren going through allogeneic HSCT who develop severe chronic obstructive lung function are more likely to present with sleep-related hypoxia and hypoventilation than children with restrictive lung function.ImpactChildren with severe obstructive lung function and chronic lung graft-versus-host disease following hematopoietic stem cell transplantation are more likely to present with sleep-related mild hypoxia and hypoventilation than children with restrictive lung disease.To our knowledge there are no reports on sleep-related breathing disorders and ventilatory function measured by polysomnography in children with pulmonary complications after allogeneic HSCT.Polysomnography may add to the differential diagnostics between patients with BOS and other non-infectious pulmonary complications.