Sleep-disordered breathing: Screening tools and definition of
key terms
Presently, there are no screening guidelines for sleep-disordered
breathing in pediatric or adult CF patients. Screening questionnaires
and tools exist for obstructive sleep apnea (OSA) in the non-CF
population, but there are no tools for screening for the rest of the
spectrum of sleep-disordered breathing. Objective tests exist to
diagnose nocturnal hypoxia , apneas, and nocturnal hypoventilation.
Nocturnal hypoxemia is defined as oxygen saturation ≤90% in children
and ≤88% in adults for >5 minutes. As per the AASM
definition, hypoventilation during sleep in children is defined as
arterial PCO2 (or surrogate) being greater than 50 mm Hg
for more than 25% of total sleep time. For adults, sleep
hypoventilation is scored when the arterial PCO2 (or
surrogate) is > 55 mm Hg for ≥ 10 minutes or there is an
increase in the arterial PCO2 (or surrogate) ≥ 10 mm Hg (in comparison
to an awake supine value) to a value exceeding 50 mm Hg for ≥ 10
minutes.8
Of all the sleep disordered breathing disorders, OSA has the most
abundant tools and screening questionnaires, both for pediatric and
adult populations. In the pediatric population, modified questionnaires
and/or the presence of snoring are used for further evaluation of
OSA.28 It has been recommended by the American Academy
of Pediatrics that enquiring about snoring at each clinical visit may be
a sensitive screening measure for OSA that is quick and easy to
perform.28 In adults, multiple different tools are
available for OSA screening, such as STOP-BANG, Berlin Criteria, and the
Epworth Sleepiness Scale (ESS).29
In the pediatric population, obstructive apnea has been defined as a
decrease in nasal pressure or oronasal thermal airflow ≥ 90% of
pre-event baseline for ≥ 2 breaths with presence of respiratory
effort.30 Hypopneas in the pediatric population are
identified by a decrease in nasal pressure or oronasal thermal airflow ≥
30% of pre-event baseline for ≥ 2 breaths with ≥ 3% oxygen
desaturation from pre-event baseline or an associated arousal. The
diagnostic criteria for OSA in children is the presence of ≥ 1
obstructive apnea or hypopnea per hour of sleep (apnea-hypopnea index
(AHI) ≥ 1 per hour).8
In adults, obstructive apnea has been defined as a decrease in nasal
pressure or oronasal thermal airflow ≥ 90% of pre-event baseline for ≥
10 seconds with continued or increased inspiratory
effort.30 Hypopneas are defined as decrease in nasal
pressure or oronasal thermal airflow ≥ 30% of pre-event baseline for ≥
10 seconds with ≥ 3% oxygen desaturation from pre-event
baseline.30 The diagnostic criteria for OSA in adults
is the presence of ≥ 5 obstructive apneas or hypopneas per hour of sleep
or per hour of monitoring (AHI ≥ 5 per hour).8
Hypoventilation in sleep, defined by a decrease in minute ventilation,
is normal in healthy controls and is more pronounced in those with lung
disease. In rapid eye movement (REM) sleep, respiratory muscle function
is reduced, during which diaphragm contraction is preserved, and minute
ventilation can decrease more than 15% in this phase of sleep in normal
individuals31. This decrease of respiratory muscle
function in patients with lung disease is more
pronounced7 , and furthermore, patients with
hyperinflation have decreased diaphragm
contraction4,32. A decrease in minute ventilation
while asleep can lead to hypercapnia.