RESEARCH Open AccessBi-level CPAP does not change central blood
flowin preterm infants with respiratory distresssyndromeGiulia
Aquilano, Silvia Galletti*, Arianna Aceti, Francesca Vitali and
Giacomo FaldellaAbstractBackground: Current literature provides
limited data on the hemodynamic changes that may occur during
bi-levelcontinuous positive airway pressure (CPAP) support in
preterm infants. However, the application of a
positiveend-expiratory pressure may be transmitted to the heart and
the great vessels resulting in changes of centralblood
flow.Objective: To assess changes in central blood flow in infants
with respiratory distress syndrome (RDS) duringbi-level CPAP
support.Design: A prospective study was performed in a cohort of 18
Very-Low-Birth-Weight Infants who were put on nasalCPAP support (45
cmH2O) because they developed RDS within the first 2472 hours of
life. Each subject wasswitched to bi-level CPAP support (Phigh 8
cmH2O, Plow 45 cmH2O, Thigh 0.5-0.6 seconds, 20 breaths/min) for
anhour. An echocardiographic study and a capillary gas analysis
were performed before and after the change ofrespiratory
support.Results: No differences between n-CPAP and bi-level CPAP in
left ventricular output (LVO, 222.17 81.4 vs211.4 75.3 ml/kg/min),
right ventricular output (RVO, 287.8 96 vs 283.4 87.4 ml/kg/min)
and superior venacava flow (SVC, 135.38 47.8 vs 137.48 46.6
ml/kg/min) were observed. The hemodynamic characteristics ofthe
ductus arteriosus were similar. A significant decrease in pCO2
levels after bi-level CPAP ventilation wasobserved; pCO2 variations
did not correlate with modifications of central blood flow (LVO: =
0.11, p = 0,657;RVO: = 0.307, p = 0.216; SVC: = 0.13, p =
0.197).Conclusions: Central blood flow doesnt change during
bi-level CPAP support, which could become a hemodinamicallysafe
tool for the treatment of RDS in preterm
infants.IntroductionBi-levelCPAPisaformofrespiratorysupportroutinelyusedtoassistadultsandchildren.
Itenablesthepatientto breathespontaneouslybetween two different
levels ofcontinuouspositivepressure, theupper(IPAP) andthelower
level (EPAP). The cycle time can be either selectedby the operator
or synchronized with the patientsrespiratoryeffort. Both IPAP and
EPAP are generated byanincreaseinthegasflowthroughthecircuit
withoutclosing the expiratory valve enabling the patient to
exhaleanytime, evenduringtheIPAPphase[1]. Theaimofbi-level
CPAPistoimprovealveolarrecruitment, gasexchange and, by a direct
stimulation of the upper airways,to prevent apneas requiring
intubation.Nasal CPAP (n-CPAP) is currently considered the
treat-ment of choice for neonatal respiratory distress
syndrome(RDS) [2]. By applying a constant distending pressure
totheairways n-CPAPmaintains thefunctional
residualcapacity(FRC)ofthelungsthroughalveolarrecruitmentand
stabilization. This constant pressure prevents alveolarcollapse
duringexpiration, improvesgas exchange andreducestheworkof
breathingfacilitatingthenextin-spiratory phase [3].The theoretical
advantage of bi-level CPAP could be thepreventionof
alveolarcollapsethroughaswingbetween* Correspondence:
[email protected] and Neonatal Intensive Care
Unit, Department of Medical andSurgical Sciences, St.
Orsola-Malpighi Hospital - University of Bologna, ViaMassarenti, 11
40138 Bologna, ItalyITALIAN JOURNALOF PEDIATRICS 2014 Aquilano et
al.; licensee BioMed Central Ltd. This is an Open Access article
distributed under the terms of the CreativeCommons Attribution
License (http://creativecommons.org/licenses/by/4.0), which permits
unrestricted use, distribution, andreproduction in any medium,
provided the original work is properly credited. The Creative
Commons Public DomainDedication waiver
(http://creativecommons.org/publicdomain/zero/1.0/) applies to the
data made available in this article,unless otherwise
stated.Aquilano et al. Italian Journal of Pediatrics 2014,
40:60http://www.ijponline.net/content/40/1/60two different FRC.
Furthermore the change in
pressure(P)createdbythismechanismcouldgenerateatidalvolume
responsible for a decrease in the work ofbreathing [4].However only
few studies were performed on newbornsand they were mainly focused
on term babies with centralhypoventilation syndrome
[5].Todatetherearefewpublisheddataontheeffectsofbi-level
CPAPinpreterminfants andnodata onthehemodynamic changes related to
the use of this respira-tory support. Nevertheless, it has
beendemonstratedthat the application of an end-expiratory positive
pressure(PEEP) caninterfere withvenous returnandcardiacoutput
[6].Thepresentstudyaimstoevaluatethehemodynamiceffectsoncardiacoutputsandvenousreturnof
bi-levelCPAP in a population of Very Low Birth Weight
Infants(VLBWIs) with RDS.MethodsPatientsA prospective study was
conducted in a cohort of VLBWIsadmittedat birthtothe Neonatal
Intensive Care Unit(NICU) of Bologna University Hospital (Italy)
betweenJanuary2012andMay2012. Infantswereeligibleforin-clusion in
the study if they developed signs of RDS requir-ingnCPAPsupport
withinthefirst 2472hoursof life.RDS was defined in presence of
clinical features of respira-tory distress (tachypnea, grunting,
chest retractions, nasalflaring), need of continuous positive
pressure to maintainoxygen saturation > 85%and compatible
radiologicalfindings (e.g. reticulo-granular pattern, ground
glassappearance, air bronchograms, reduced lung volume).Inorder
tobeincludedinthestudy, infants shouldhave been hemodynamically
stable (normal blood pressure,normal urine output and no need for
inotropes).Infantswithcongenitalheartdisease,
congenitalmal-formations or assisted with mechanical ventilation
wereexcluded.Eachpatient was supportedwithn-CPAPfor severalhours,
and switched to bi-level CPAP for a study period ofanhour.
Attheendof thestudyperiodall thesubjectswere put back on n-CPAP.The
Infant Flow SiPAP system(Viasys Healthcare,YorbaLinda, CA, USA),
whichallows theoperator toswitch fromn-CPAP to bi-level CPAP mode
withoutinterruptionof therespiratorysupport or changes ofthe device
circuit, was used for the present study. Shortbi-nasal prongsof
thelargest
sizefittingcomfortablythepatientsnareswereusedinordertominimizeairleaks.
Alternatively, nasal masks of the appropriate sizefor the patients
nose were used.Nasal CPAP was set at 45 cm H20 and bi-level CPAPas
follows: Phigh8cmH2O, Plow4-5cmH2O, Thigh0.5-0.6seconds,
rate20breaths/min. Theminimal frac-tional
inspiredoxygensaturation(FiO2)wassetinorderto maintain oxygen
saturation (SpO2), monitored througha transcutaneous device,
between 85 and 94%. Before andafter the study period, blood
pressure was recorded, a ca-pillary blood gas analysis was
collected to detect the PCO2level,
andanechocardiographicstudywasperformedtoevaluate the hemodynamic
parameters.Blood pressure was measured non-invasively by
theoscillometricmethod. Threevaluesof meanbloodpres-sure were
averaged and compared with normal values forgestational
age.Hemodynamic measurementsThe echocardiographic study was
performed using a PhilipsHD11XE(PhilipsUltrasound, Andover, MA,
USA)ultra-sound systemwitha 12-4 Hz transducer
incorporatingcolourflowandpulsewaveDoppler.
Noanglecorrectionwasused. Leftventricularoutput(LVO),
rightventricularoutput (RVO), superior vena cava (SVC) flow, the
diameterandthecharacteristicsof theductusarteriosus(DA)
andforamenovalewereevaluated. RVO, LVOandSVCflowwere measured
according to previously publishedmethodology [7,8]. For
thecalculation of flow, the fol-lowingformula was used: flow=
(velocity time integral ( (diameter24) heart rate)body weight.
Sixor morecycles were averaged for these measurements.
Cardiacoutputs
