Results:
A total of 38 infants who had significant HRF were enrolled in the
study. All of them had developed chronic lung disease, defined as
requirement of respiratory support at postmenstrual age of 36 weeks; but
all subsequently survived until discharge. None of the studied infants
had intraventricular hemorrhage >grade II or were diagnosed
with hydrocephalus. No infants had suspected or culture proven sepsis
during the period under study. The assessed infants were at median inter
quartile range (IQR) gestation (GA) and birth weight (BW) of 26 weeks
(25, 27) and 725g (737, 842) respectively. The patterns of response to
CAR assessment were used to separate the studied infants into two
groups: those with normal CAR (group 1) and those with impaired CAR
(group 2). Twenty-seven infants tolerated the CAR assessment test (group
1) with median (IQR) duration of 12 minutes (9, 15 minutes). Eleven
infants did not tolerate CAR assessment (group 2) with desaturation on
SpO2, associated with low crRTO on NIRS after the first few attempts of
FiO2 reduction. Table 1 shows the basic clinical and
hemodynamic parameters including Hb, carbon dioxide
(CO2) and left heart cardiac output (LVO) which are the
main confounders affecting oxygen delivery. There was no statistical
difference between both groups regarding all basic clinical and
hemodynamic parameters, other than infants in group 2 were less mature
in gestational age, 4 infants from group 2 discharged home on oxygen and
non from group 1. Table 2 shows the oxygen indices before and at the end
of CAR assessment test. All infants in group 1 achieved a lower
FiO2 after CAR assessment compared to their baseline;
and all had significantly lower FiO2 (both as percent of
reduction and as an absolute fraction; Mean percent of reduction :34%
and FiO2: 0.5) compared to group 2 (Mean percent of reduction of 5.3%
and FiO2 of 0.63), calculated after CAR test and at 72 hours of
integrated monitoring by pulse oximetry and NIRS. Group 1 had
significantly higher crRTO and lower FOE (Mean of 71 % and FOE of 0.13)
compared to group 2 (Mean of 62% and FOE of 0. 3). There was no
significant difference between both groups in OSI before and after CAR
test, figure 2 shows the comparison between oxygen indices before and
after ORT, group 1 (figure 2A) had significantly lower FiO2 at the end
of ORT, and group 2 (figure 2B) had significantly lower crRTO and higher
FOE at the end of ORT.