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\begin{document}

\title{Utility of supine spirometry to predict sleep disordered breathing in
children with neuromuscular disorders}



\author[1]{Chetan Pandit}%
\author[1]{Brendan Kennedy}%
\author[1]{Karen Waters}%
\author[1]{Helen Young}%
\author[1]{Kristi Jones}%
\author[1]{Dominic Fitzgerald}%
\affil[1]{Children's Hospital at Westmead}%


\vspace{-1em}



  
  \date{May 26, 2024}


\begingroup
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\selectlanguage{english}
\begin{abstract}
Aim To explore the relationship between postural changes in lung
function and polysomnography (PSG) in the assessment of early sleep
disordered breathing in children with neuromuscular disorders {[}NMD{]}.
Methods In this prospective cross-sectional study, children with NMD
performed spirometry in sitting (si) and supine (su) positions. A
control group of age and gender matched healthy children also underwent
postural lung function testing. PSG was performed within 6 months of
spirometry. Spirometry was acceptable according to ATS standards and
PSGs scored according to AASM guidelines. Results Forty-one children
with NMD, aged 12.3 \selectlanguage{ngerman}±3 years (21 males) performed sitting spirometry.
Thirty {[}73\%{]} performed acceptable spirometry in the supine
position. Underlying diagnoses were heterogeneous, with the majority
having Duchenne Muscular Dystrophy (n=17). Mean FEV1sit and FVCsit were
78\% (SD ±22) and 75\% (SD±20.4) respectively, with mean\% \selectlanguage{greek}Δ\selectlanguage{english}FVC (sit --
sup) 9\selectlanguage{ngerman}±11\% (range 2\% to 20\%), and was significantly greater than
healthy controls (n=30 SD ±3) (p\textless{}0.001). PSG data on these 30
children showed total AHI 6.9 ±5.9/hr (0.3 to 29), obstructive AHI
5.2±4.0/hr (0.2 to 10), and REM AHI 14.1+/-5.3/hr (0.1 to 34.7). A
moderate correlation was present between supine FVC\% and AHI (r=0.62,
p=0.001) in those not using non-invasive ventilation {[}NIV{]} in sleep
{[}N=22{]} but not with the rise in CO2 from non-REM to REM sleep (6
±1.9 mmHg, range 4 to 11). Conclusion Children with NMD and mild
restrictive lung disease showed greater postural changes in spirometry
than healthy controls, with changes being greatest in children who
required nocturnal NIV.%
\end{abstract}\selectlanguage{ngerman}%



\sloppy


\textbf{Introduction}

Neuromuscular disorders (NMD) are rare in the general population with an
estimated prevalence of approximately 1 in 3000.(1) These conditions
predominantly have a genetic basis and often present during childhood.
Respiratory morbidity leading to respiratory failure is the common
pattern seen in children and adults with neuromuscular weakness.(2) The
degree of respiratory involvement in these disorders is variable and can
present at differing ages in children.(2) This predominantly depends on
the underlying NMD with other factors including lower respiratory
illness, scoliosis and pulmonary aspiration having an effect on the age
of presentation of respiratory failure.(2-4) Appropriate screening for
respiratory failure and subsequent intervention has been shown to reduce
unplanned hospital admissions and improve life expectancy.(2, 5-7)

Involvement of respiratory muscles causes significant clinical sequelae,
with recurrent respiratory illness and consequently routine respiratory
monitoring is recommended in children with NMD.(8) Detailed evaluation
relies on additional testing, which includes both invasive tests and
non-invasive tests. Amongst the invasive tests the most reliable is the
measurement of the oesophageal (P\emph{oes} ) and gastric pressures
(P\emph{gas} ). Amongst the non-invasive tests, vital capacity (VC),
maximal inspiratory/expiratory pressures (MIP/MEP), sniff nasal
inspiratory pressure (SNIP), the peak expiratory flow (PEF) and cough
peak flow (CPF) have been studied extensively and are in clinical use in
a number of centres.(9) These tests are limited by the need for patient
cooperation to achieve the required technical quality standards.(8, 10)
Patients with NMD are typically at risk for sleep disordered breathing
(SDB) and hypoventilation. SDB is often the first signs of progressive
respiratory decline which can manifest as REM- associated
hypoventilation and then into continuous nocturnal hypoventilation.(10)

Spirometry measured in the supine position has been studied in adult
patients with NMD. (11, 12) In the seated position it is estimated that
the diaphragm contributes to nearly 70\% of tidal breathing and the
intercostal muscles approximately 30\%.(1, 13) However, in the supine
position, the diaphragm contributes nearly 90\% of breathing done by a
normally functioning diaphragm when upright.(14, 15) Studies in adults
with amyotrophic lateral sclerosis demonstrated that supine spirometry
has a sensitivity of 79\% and specificity of 90\% to detect
diaphragmatic weakness.(14, 15) Supine spirometry has been suggested as
a screening test to detect diaphragmatic weakness in children with NMD
based on a small number of studies that predominantly involve
adults.(11, 16) This screening test has been included in paediatric
management guidelines despite being based on data extrapolated from
adult studies.(17, 18)\{, 2012 \#449;Wang, 2012 \#489\} There is a
paucity of data on supine spirometry in healthy children, let alone
children with neuromuscular disease. The aims of our study were to (1)
test the feasibility of supine spirometry in normal children and
children with neuromuscular diseases and (2) to correlate the degree of
respiratory dysfunction measured by supine spirometry in children with
neuromuscular disease with polysomnography derived parameters of the
effectiveness of gas exchange.(19-23)

\textbf{Methods}

This was a cross-sectional, prospective study approved by the Human
Research Ethics Committee at the Children's Hospital at Westmead
(LNR/12/SCHN/280). Patients diagnosed with neuromuscular disorders
managed through the Neurogenetics clinic at the Children's Hospital at
Westmead were invited to participate in the study. Controls were
siblings or friends of neuromuscular patients or children of staff
members who had no previous significant respiratory health issues. The
inclusion criteria were a proven underlying neuromuscular disease {[}via
genetics, muscle biopsy or nerve conduction studies{]}, age 8 to 18
years, cognitive capacity to perform seated and supine spirometry and
willingness to have an overnight polysomnogram {[}PSG{]}. Written
informed consent was provided by the parent or primary caregiver and
children gave their verbal consent to perform the test. The recruitment
of patients and healthy controls ran for 24 months,

Data collection was performed during two visits. During the first visit,
demographic data was recorded and pulmonary function testing was
performed. At the second visit overnight polysomnography parameters were
recorded. Demographic information was gathered on the following: (1)
diagnosis (2) age at diagnosis, (3) height, (4) weight, (5) BMI, (6)
gender, (7) use of wheelchair or walking aids and (8) other medical
conditions (e.g. asthma). Testing was offered during their routine
clinic visits, scheduled at six monthly intervals. Forced vital capacity
(FVC) and Forced Expiratory Volume in one second (FEV\textsubscript{1})
were measured with a Lilly type pneumograph (Viasys Healthcare,
California) according to ATS/ERS standards.(24) Children were tested in
a conventional upright seated position followed by a supine position
while wearing a nose clip. As per ATS/ERS guidelines, the best effort,
determined as the measurement with the highest sum of FVC and
FEV\textsubscript{1}, was recorded for the study. (23) Values were
expressed as a percentage of predicted normal values (based on healthy
children of the same age, gender, and height). Reference values were
derived from published data.(24) As there are no published reference
standards for supine FVC, percent predicted supine FVC was calculated
using predicted values for upright FVC. Children who were unable to
produce acceptable and repeatable spirometry in sitting positions
according to standardized ATS/ERS criteria were excluded. Children with
acceptable and repeatable sitting lung function were asked to perform
spirometry in the supine position during the same clinic visit.

Overnight polysomnography was only performed in the children with NMD,
and all were undertaken at the David Read Sleep Unit, in The Children's
Hospital at Westmead, NSW, Australia, within 6 months of performing
pulmonary function tests. Children established on non-invasive
ventilation {[}NIV{]} previously had their most recent PSG parameters of
the diagnostic component of sleep study accessed for this study.
Polysomnography was performed in accordance with the 1997 American
Thoracic Society (ATS) guidelines using the Sandman Elite\selectlanguage{ngerman}® Version 9.2
system (Embla Systems, Broomfield, CO, USA). Data was collected
according to standardized recommendations, commenced between 19:30 and
21:00, and ended at 06:00 the following morning. Data analyses were
performed in accordance with the 2007 American Academy of Sleep Medicine
guidelines.(25) The modified Epworth Sleepiness Scale (mESS)
questionnaire was completed by the child or the parent at the time of
the polysomnography.

Respiratory events were scored if they were at least two respiratory
cycles long, and significant oxygen desaturations were defined as \selectlanguage{english}[?] 3\%
desaturation from baseline. Children were classified as having sleep
disordered breathing {[}SDB{]} if polysomnography results showed an
apnoea-hypopnoea-index {[}AHI{]} \textgreater{}1.0 events/h.(26) The
severity of SDB was further classified: mild SDB was defined as an AHI
of 1.0 to 4.99 events/h, moderate SDB defined as 5 events/h to 9.99
events/h and severe SDB defined as an AHI \textgreater{} 10 events/h.
Nocturnal hypoventilation was defined according to AASM as
\textgreater{} 25 \% of sleep time with a TcCO\textsubscript{2}
\textgreater{}50 mmHg or a PCO\textsubscript{2} rise of
\textgreater{}10mmHg from baseline (25, 27). (25, 28)

Pearson correlations and linear regression models were used to examine
associations between the measures of respiratory function and
polysomnography. Sensitivity and specificity results were calculated.
Logistic regression was used to examine the ability of change in \% FVC
to predict a binary outcome of an AHI \selectlanguage{english}[?] 5 events/hr. All analyses were
conducted in SAS version 9.3 (SAS Institute Inc., Cary, NC, USA). There
was no adjustment made for multiple statistical comparisons. A p-value
of \textless{}0.05 was considered statistically significant.

\textbf{Results}

Thirty of the forty-one (73\%) patients approached were enrolled and
able to perform spirometry in both sitting and supine positions. The
mean age at testing was 11.5 years (SD +-3.0). Thirty controls without
respiratory or sleep pathology were recruited Characteristics of the two
study groups are shown in Table 2.

Specific neuromuscular diagnoses were heterogeneous, with the majority
(17/30; 57\%) having Duchenne Muscular Dystrophy {[}DMD{]} (Table 1).
Children with NMD were further categorized as unsupported in sleep (i.e.
spontaneously breathing: N=22) or established on nocturnal NIV
{[}N=8{]}.

\textbf{Pulmonary function testing}

An average of 15 minutes was taken to perform reliable supine spirometry
after performing sitting spirometry. In the neuromuscular group, the
mean sitting FEV\textsubscript{1}\% and sitting FVC\% were 78\% (SD
+-21.9) and 75\% (SD+-20.5) respectively as shown in Table 3. The
percentage difference in \selectlanguage{greek}Δ\selectlanguage{english}FVC between sitting and supine in these NMD
children was 9\%.

Children breathing spontaneously had an FEV\textsubscript{1}\% of 83\%
(SD\selectlanguage{ngerman}±21.9) and an FVC\% of 78\% (SD±20.5) and a mean drop in FVC\% in the
supine position of 7\% (SD±17.9). Children on nocturnal NIV had baseline
sitting FEV\textsubscript{1}\% and FVC\% values of 72\%(SD±17.9) and
70\%(SD±24.5), respectively, with a mean drop of 12\% in the supine
position to an FVC\% of 58(SD±18.8). Healthy controls had a baseline
sitting lung function of FEV\textsubscript{1} \% and FVC\% of 95\%
(SD±5.2) and 98\% (SD±4.8), respectively, with a mean drop of 4\% in
\selectlanguage{greek}Δ\selectlanguage{english}FVC in the supine position, (p\textless{}0.001 compared to children
with NMD) (Table 3).

Amongst the 11 children who could not do spirometry, 3 children had
cognitive delay and were unable to perform acceptable and reproducible
spirometry in the sitting position. Another three children were excluded
because they did not have acceptable or repeatable spirometry. Five
children had severe restrictive lung disease (FVC\textless{}40\%) and
were able to perform sitting spirometry but were excluded because of
poor spirometry technique in the supine position.

\textbf{Polysomnography (PSG) in children with NMD}

PSG data were available within 6 months of spirometry for the 30
children with NMD. Mean (\selectlanguage{ngerman}±SD) total sleep time was 351±8.8 min. The
total AHI was 6.9 ±5.9/hour, obstructive AHI was 5.2±4.2 /hour and REM
AHI 14.1±5.3 /hour. Only 2 children {[}7\%{]} had a normal total AHI
{[}\textless{}1/hr{]}.(25) The average baseline SpO\textsubscript{2} was
96 SD±5\% and minimum saturation for the entire cohort was 88.4
SD±4.2\%. The mean baseline transcutaneous {[}Tc{]} CO\textsubscript{2}
was 44mmHg (SD±5). The rise in TcCO\textsubscript{2} from NREM to REM
sleep in the entire cohort was 6 mmHg (SD±2.7) (Table 6).

Eight children with NMD were already established on non-invasive
ventilation (NIV) when they were studied. Indications for NIV included
recurrent chest infections requiring paediatric intensive care unit
admissions (n=2) or evidence of sleep disordered breathing (n=6). The
TcCO\textsubscript{2} rise from NREM to REM sleep of 5 vs 9 mmHg, for
children breathing spontaneously compared to those on nocturnal NIV.

There was no significant correlation between postural changes in
spirometry and the rise in CO\textsubscript{\textbf{2}} from NREM to REM
sleep on PSG for the group as a whole (r-=0.04, p=0.8), the group
spontaneously breathing (r=0.02, p=0.9), or for those established on NIV
(r=0.13,p=0.74). The healthy controls did not have polysomnograms.

\textbf{Discussion}

This study demonstrates the feasibility and utility of supine spirometry
in children with NMD. To our knowledge this is the first study in
children where heathy contemporary controls performed supine spirometry
to generate comparative data. The majority of children with NMD (73\%)
who agreed to participate in this study were able to perform supine
spirometry reliably. This study demonstrated a significantly greater
decline in spirometry in the supine position in 30 children with NMD
compared to 30 healthy controls (9\% vs 4\%, p=0.03). Supine spirometry
also showed greater decline in children NMD who required nocturnal
non-invasive ventilation compared to those breathing spontaneously (12\%
vs 7\%, p=0.02). The implications of the postural drop in FVC in
children with NMD therefore suggest that its' sensitivity to the level
of respiratory muscle compromise occurring in the supine position
relates to disease severity.

The falls in supine spirometry for this cohort were relatively mild
compared to previous studies, and we speculate that this reflects
generalised weakness of respiratory muscles rather than being a measure
of early diaphragmatic weakness.(29) Lechtzin et al. showed that in a
heterogeneous group of NMD disorders and using invasive measures of
diaphragmatic function, a 25\% drop in spirometry in the supine position
was suggestive of diaphragmatic weakness(14). Certain NMDs, including
congenital muscular dystrophy and their subtypes LAMA2-RD and COL6-RD,
demonstrate progressive respiratory failure due to disproportionate
diaphragmatic involvement.(29) None of the patients in the current
cohort dropped their lung function {[}FVC{]} by \textgreater{}25\%
{[}Maximum change was 20\%{]}, as described in previous studies
performed on adults with NMD to suggest significant diaphragmatic
weakness.(15) From limited studies, performed predominantly in adult
patients, an increasing difference between seated and supine spirometry
is thought to indicate weakness in a combination of diaphragmatic and
other inspiratory muscles, especially the intercostal muscles, resulting
in inability to expand the chest wall against the abdominal contents in
the supine position. Therefore, we believe the larger postural drop in
spirometry demonstrated in the present study in NMD children established
on nocturnal NIV suggests more severe generalised respiratory muscle
weakness.

This is the first study in children to demonstrate a difference in the
postural changes in FVC with NMD breathing spontaneously compared to
those established on nocturnal NIV. Previously, Chen et al. compared the
relationship of the postural changes in FVC and
FEF\textsubscript{25-75}and the need to initiate NIV in patients with
neuromuscular disorders in an adult cohort with a heterogeneous group of
underlying disorders with the largest subset having ALS.(33) There was a
substantial difference in postural FVC between patients who were
spontaneously breathing and those on nocturnal NIV. This led to the
conclusion that a 14-fold difference in postural change in FVC\% is more
significant than just the reduction of supine FVC\textless{}75\% as an
indication to start nocturnal NIV. Our paediatric study demonstrated an
approximately 2-fold difference in postural change in spirometry between
those breathing spontaneously as compared to those on NIV. The findings
by Chen et al. were greater than previous studies performed by Schmidt
et al. who showed a change of 16\% and Varrato et al. who demonstrated a
drop of 13\%.(30, 31) In the study by Varrato et al. on adults with ALS,
patients who experienced breathlessness, orthopnoea and daytime lethargy
had a postural drop of 25\% as compared to those who did not demonstrate
these symptoms. Their study did not compare ALS subjects with other
adults established on NIV.

Polysomnography results confirmed that 93\% of children in this cohort
had SDB, which was predominantly obstructive in nature. The presence of
obstructive sleep apnoea may be explained by an abnormal increase in
upper airway resistance, muscle weakness, or a combination of the two.
The high prevalence of obstructive sleep apnoea is similar to other
published literature which shows that between 30\% and 60\% of children
with DMD had obstructive findings on polysomnography.(19, 20) Our cohort
was a heterogeneous group of patients with NMD which may have
contributed to the high prevalence of OSA. Other co-morbidities
including obesity {[}related to chronic oral corticosteroid treatment
and immobility{]} may also have played a role in the presence of sleep
disordered breathing.

Considering sleep hypoventilation, while we considered the greater rise
in the NIV group (9 compared to 6 mmHg) to reflect greater muscular
weakness, we found no correlation between this measure and the postural
changes in spirometry. REM hypoventilation may be due to loss of
intercostal muscle activity in this sleep state.(32) However, it cannot
be distinguished from effects of SDB due to upper-airway weakness and
reduced pharyngeal tone in this sleep state, as previously reported in
studies performed on children with DMD as well as congenital myopathies.
(9, 32, 33) Our findings of a poor correlation of supine FVC\% as a
single measure with the severity of SDB are in agreement with another
study performed by Khan et al., on 21 subjects with DMD aged 13 to 23
years.(33)

\textbf{Limitations}

Limitations to our study included involvement of only a single site
where children were recruited from one neuromuscular clinic resulting in
a small sample size even though all children with NMD who fulfilled
inclusion criteria were approached to participate in the study. In
addition, ccorrelations between spirometry and PSG parameters may have
been apparent if PSG data had been obtained in the control group. Whilst
historical cohorts looking at supine spirometry have included similar
numbers of patients, we recognize that larger numbers of patients are
needed. Children with severe restrictive lung disease
(FVC\textless{}40\%) who were already established on NIV were unable to
perform reliable spirometry in both sitting and supine positions. Supine
spirometry is therefore not useful in these children on the more severe
end of the spectrum where it may be uncomfortable, impractical und
unhelpful in predicting SDB. Lastly, the cross-sectional nature of the
study did not allow examination of the relationship between supine
spirometry and evolution of respiratory weakness over time.

\textbf{Conclusion}

In children with NMD, postural change in spirometry in this cohort of
children with neuromuscular disorders was markedly greater than in
healthy controls. These postural changes in spirometry were sensitive to
the degree of nocturnal respiratory support the children required, but
did not correlate with measures of sleep hypoventilation.

\textbf{References}

1. Emery AE. Population frequencies of inherited neuromuscular
diseases--a world survey. Neuromuscular disorders : NMD.
1991;1(1):19-29.

2. Perrin C, Unterborn JN, Ambrosio CD, Hill NS. Pulmonary complications
of chronic neuromuscular diseases and their management. Muscle \& nerve.
2004;29(1):5-27.

3. Benditt JO, Boitano LJ. Pulmonary issues in patients with chronic
neuromuscular disease. American journal of respiratory and critical care
medicine. 2013;187(10):1046-55.

4. Dohna-Schwake C, Ragette R, Teschler H, Voit T, Mellies U. Predictors
of severe chest infections in pediatric neuromuscular disorders.
Neuromuscular disorders : NMD. 2006;16(5):325-8.

5. Howard RS, Wiles CM, Hirsch NP, Spencer GT. Respiratory involvement
in primary muscle disorders: assessment and management. The Quarterly
journal of medicine. 1993;86(3):175-89.

6. Mah JK, Korngut L, Dykeman J, Day L, Pringsheim T, Jette N. A
systematic review and meta-analysis on the epidemiology of Duchenne and
Becker muscular dystrophy. Neuromuscular disorders : NMD.
2014;24(6):482-91.

7. Chatwin M, Toussaint M, Goncalves MR, Sheers N, Mellies U,
Gonzales-Bermejo J, et al. Airway clearance techniques in neuromuscular
disorders: A state of the art review. Respiratory medicine.
2018;136:98-110.

8. Baydur A. Respiratory muscle strength and control of ventilation in
patients with neuromuscular disease. Chest. 1991;99(2):330-8.

9. Mellies U, Ragette R, Schwake C, Boehm H, Voit T, Teschler H. Daytime
predictors of sleep disordered breathing in children and adolescents
with neuromuscular disorders. Neuromuscular disorders : NMD.
2003;13(2):123-8.

10. Fauroux B, Quijano-Roy S, Desguerre I, Khirani S. The value of
respiratory muscle testing in children with neuromuscular disease.
Chest. 2015;147(2):552-9.

11. Allen SM, Hunt B, Green M. Fall in vital capacity with posture.
British journal of diseases of the chest. 1985;79(3):267-71.

12. Rubini A. The Effects of Prone with Respect to Supine Position on
Stress Relaxation, Respiratory Mechanics, and the Work of Breathing
Measured by the End-Inflation Occlusion Method in the Rat. Lung.
2016;194(1):53-9.

13. Davis J, Goldman M, Loh L, Casson M. Diaphragm function and alveolar
hypoventilation. The Quarterly journal of medicine. 1976;45(177):87-100.

14. Lechtzin N, Wiener CM, Shade DM, Clawson L, Diette GB. Spirometry in
the supine position improves the detection of diaphragmatic weakness in
patients with amyotrophic lateral sclerosis. Chest. 2002;121(2):436-42.

15. Fromageot C, Lofaso F, Annane D, Falaize L, Lejaille M, Clair B, et
al. Supine fall in lung volumes in the assessment of diaphragmatic
weakness in neuromuscular disorders. Archives of physical medicine and
rehabilitation. 2001;82(1):123-8.

16. Baydur A, Behrakis PK, Zin WA, Jaeger MJ, Weiner JM, Milic-Emili J.
Effect of posture on ventilation and breathing pattern during room air
breathing at rest. Lung. 1987;165(6):341-51.

17. Hull J, Aniapravan R, Chan E, Chatwin M, Forton J, Gallagher J, et
al. British Thoracic Society guideline for respiratory management of
children with neuromuscular weakness. Thorax. 2012;67 Suppl 1:i1-40.

18. Wang CH, Dowling JJ, North K, Schroth MK, Sejersen T, Shapiro F, et
al. Consensus statement on standard of care for congenital myopathies.
Journal of child neurology. 2012;27(3):363-82.

19. Bushby K, Finkel R, Birnkrant DJ, Case LE, Clemens PR, Cripe L, et
al. Diagnosis and management of Duchenne muscular dystrophy, part 2:
implementation of multidisciplinary care. The Lancet Neurology.
2010;9(2):177-89.

20. Dreher M, Rauter I, Storre JH, Geiseler J, Windisch W. When should
home mechanical ventilation be started in patients with different
neuromuscular disorders? Respirology. 2007;12(5):749-53.

21. Lee ET, Cowan LD, Welty TK, Sievers M, Howard WJ, Oopik A, et al.
All-cause mortality and cardiovascular disease mortality in three
American Indian populations, aged 45-74 years, 1984-1988. The Strong
Heart Study. American journal of epidemiology. 1998;147(11):995-1008.

22. Piper A. Sleep abnormalities associated with neuromuscular disease:
pathophysiology and evaluation. Seminars in respiratory and critical
care medicine. 2002;23(3):211-9.

23. Arens R, Muzumdar H. Sleep, sleep disordered breathing, and
nocturnal hypoventilation in children with neuromuscular diseases.
Paediatric respiratory reviews. 2010;11(1):24-30.

24. Miller MR, Hankinson J, Brusasco V, Burgos F, Casaburi R, Coates A,
et al. Standardisation of spirometry. The European respiratory journal.
2005;26(2):319-38.

25. Berry RB, Budhiraja R, Gottlieb DJ, Gozal D, Iber C, Kapur VK, et
al. Rules for scoring respiratory events in sleep: update of the 2007
AASM Manual for the Scoring of Sleep and Associated Events.
Deliberations of the Sleep Apnea Definitions Task Force of the American
Academy of Sleep Medicine. Journal of clinical sleep medicine : JCSM :
official publication of the American Academy of Sleep Medicine.
2012;8(5):597-619.

26. Beck SE, Marcus CL. PEDIATRIC POLYSOMNOGRAPHY. Sleep medicine
clinics. 2009;4(3):393-406.

27. Pamula Y, Nixon GM, Edwards E, Teng A, Verginis N, Davey MJ, et al.
Australasian Sleep Association clinical practice guidelines for
performing sleep studies in children. Sleep medicine. 2017;36 Suppl
1:S23-s42.

28. Janssen KC, Phillipson S, O'Connor J, Johns MW. Validation of the
Epworth Sleepiness Scale for Children and Adolescents using Rasch
analysis. Sleep medicine. 2017;33:30-5.

29. Meilleur KG, Linton MM, Fontana J, Rutkowski A, Elliott J, Barton M,
et al. Comparison of sitting and supine forced vital capacity in
collagen VI-related dystrophy and laminin alpha2-related dystrophy.
Pediatric pulmonology. 2017;52(4):524-32.

30. Varrato J, Siderowf A, Damiano P, Gregory S, Feinberg D, McCluskey
L. Postural change of forced vital capacity predicts some respiratory
symptoms in ALS. Neurology. 2001;57(2):357-9.

31. Schmidt EP, Drachman DB, Wiener CM, Clawson L, Kimball R, Lechtzin
N. Pulmonary predictors of survival in amyotrophic lateral sclerosis:
use in clinical trial design. Muscle \& nerve. 2006;33(1):127-32.

32. Ragette R, Mellies U, Schwake C, Voit T, Teschler H. Patterns and
predictors of sleep disordered breathing in primary myopathies. Thorax.
2002;57(8):724-8.

33. Khan Y, Heckmatt JZ. Obstructive apnoeas in Duchenne muscular
dystrophy. Thorax. 1994;49(2):157-61.

34. Chen J, Nguyen N,Soong M, Baydur A; J Pulmon Resp Med 2013, 3:2
http://dx.doi.org/10.4172/2161-105X.1000147

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