Sources of methodological variability in phase angles from respiratory inductance plethysmography in preterm infants.
BACKGROUND
Better phenotypic descriptions are needed for chronic lung disease among surviving premature infants.


OBJECTIVE
The purpose of this study was to evaluate the potential usefulness of respiratory inductance plethysmography in characterizing respiratory system mechanics in preterm infants at 32 weeks postmenstrual age.


METHODS
Respiratory inductance plethysmography was used to obtain the phase angle, Φ, to describe rib cage and abdominal dyssynchrony in 65 infants born between 23 and 28 weeks gestation, all of whom were studied at 32 weeks postmenstrual age. Up to 60 breaths were evaluated for each subject. Sources of intrasubject variability in Φ arising from our methods were explored using mechanical models and by evaluating interobserver agreement.


RESULTS
The mean Φ from infants ranged from 5.8-162.9°, with intrasubject coefficients of variation ranging from 11-123%. On the basis of the mechanical model studies, respiratory inductance plethysmography recording and analysis software added <2.3% to the intrasubject variability in Φ. Potential inconsistencies in breaths selected could have contributed 8.1%, on average, to the total variability. The recording sessions captured 22.8 ± 9.1 minutes of quiet sleep, and enough breaths were counted to adequately characterize the range of Φ in the session.


CONCLUSIONS
Φ is quite variable during even short recording sessions among preterm infants sleeping quietly. The intrasubject variability described herein arises from the instability of the rib cage and abdominal phase relationship, not from the recording and analytical methods used. Despite the variability, Φ measurements allowed the majority (80%) of infants to be reliably categorized as having relatively synchronous or dyssynchronous breathing. Respiratory inductance plethysmography is easy to use and should prove useful in quantifying respiratory mechanics in multicenter studies of preterm infants.
1 Department of Pediatrics, Division of Newborn Medicine.
Lara N
LN
Ulm
Aaron
A
Hamvas
Thomas W
TW
Ferkol
Oscar M
OM
Rodriguez
Claudia M
CM
Cleveland
Laura A
LA
Linneman
Julie A
JA
Hoffmann
Maria J
MJ
Sicard-Su
James S
JS
Kemp
D005260:Female; D005865:Gestational Age; D006801:Humans; D007231:Infant, Newborn; D007234:Infant, Premature / Q000502:physiology*; D008297:Male; D008991:Monitoring, Physiologic; D010991:Plethysmography / Q000379:methods*; D012372:ROC Curve; D012016:Reference Values; D015203:Reproducibility of Results; D012119:Respiration; D013990:Tidal Volume / Q000502:physiology*
inductance plethysmography; phase angle; premature infant respiration