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AASMMembershipSectionsNewsletter
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Issue #5
4.What are themechanisms forPeriodic
Breathing?
Periodicbreathing is aperipheral
chemoreceptor-driven event. Periodic
breathing is rarely seen at 2days of life,
whenperipheral chemoreceptor drive is
inactive. Partial pressureofO2 changes
from25mmHg as a fetus to50Hg in
thefirst fewbreaths of extrauterine
life, rising to70mmHg in thefirst few
hours of life. Consequently, this relative
“excess”of oxygen renders the carotid
bodies insensitive tooxygen changes until
they are reset. “Resetting”of peripheral
chemoreceptors occurs in thefirstweeks
of life, achieving their usual hypoxic
responsiveness. Periodicbreathing is
related topCO2 levels and its relationship
to apneic threshold. Reduction inpCO2
levels below a certainpoint causes apnea
during sleep, and this level is termed the
apneic threshold.Theheightened sensitivity
of peripheral chemoreceptors tohypoxia
leads tounstable ventilation, resulting in
decreasingpCO2 levels below the apneic
threshold. Apneic threshold innewborn
infants is only1-2mmbelow the eupneic
pCO2 level, thusmaking themvulnerable
toperiodicbreathing.Anothermechanism
that contributes toperiodicbreathing
includes low lungvolumes.
5.What is theeffect of sleeponPeriodic
Breathing?
Periodicbreathingoccurs predominantly
in sleep, andperiodicbreathing is present
inbothquiet and active sleep; however,
the variability inbreathingpattern is state
dependent.Thus,whenperiodicbreathing
occurs duringquiet sleep, it is very regular
with lengthof breathing and apneicperiods
remaining relatively constant.When
periodicbreathingoccurs during active
sleep, thepatternof periodicbreathing is
less regular and the apneas canbeof longer
duration.
6.What are the consequencesofPeriodic
Breathing?
Periodicbreathinghas been considered to
be abenignbreathingpattern inpremature
infants.More recent datademonstrates
that significant desaturationsmaybe
associatedwith apneicpauses and in some
premature infants, periodicbreathing
frequentlyprecedes longer apneicpauses.
There is concern that an excessive amount
of periodicbreathingwith associated
intermittent hypoxemiadue to frequent
O2desaturations canhaveneurocognitive
morbidity, probably related tohypo-
perfusion and reperfusionmechanisms
within thebrain.
7.What are the treatment options for
PeriodicBreathing?
Usuallyno treatment isnecessaryand
periodicbreathing resolves spontaneously
withmaturity.However, a subset of infants
developanexcessiveamount of periodic
breathingassociatedwith repetitive
desaturations and slowingofheart rate.
Supplemental oxygenwithconcentrations
as lowasFiO20.25-0.30hasbeen shown to
stabilizebreathingpatternswith resolutionof
periodicbreathingandhypoxemia (Fig. 2).
Further reading:
1. EdwardsBA, Sands SA, BergerPJ.
Postnatalmaturationof breathing
stability and loopgain: the roleof
carotid chemoreceptor development.
RespirPhysiolNeurobiol. 185 (2013)
144-155
2. KhanA,QurashiM, KwiatkowskiK
et al.Measurement of theCo2 apneic
threshold innewborn infants: possible
relevance for periodicbreathing and
apnea. JAppl Physiol 2005;98(4):1171-6
