Results
Between March and December 2021, 40 patients were enrolled, and DUS
examinations were performed (figure 2). Within 48 hours, 24 (60%) of
patients were successfully extubated, while 16 (40%) required invasive
or non-invasive MV support. Three of the sixteen patients in the FE
group required re-intubation (7.5%), and thirteen received non-invasive
MV (32.5%). Between the SW and FE groups, there were no statistically
significant differences in age, sex, PIM-3, PRISM-4, need for inotrope
infusion, indication for IMV, maximum OSI, and treatments used. The FE
group had a longer duration of inotrope infusion days, a longer duration
of IMV, and a longer length of stay in the PICU than the SW group (table
1).
Diaphragm measurements of the SW and FE groups are also shown in table
1. While DTi and DTe did not differ significantly between the two
groups, DTF was significantly greater in the SW group (55,05 ± 23,75%
vs. 30,9 ± 10,38%) (p<0,001). DE was significantly greater in
the SW group (14 ± 4,4 mm vs 11,05 ± 3,25 mm) (p<0,001), but
there was no significant difference in IS or ES between the two groups.
When DTF and DE were compared in terms of post-extubation intervention
requirements, while DTF was significantly different between those who
required reintubation and those who required NIV (p=0.021), there was no
significant difference in terms of DE (p=0.620) (table 2).
The ROC curves for DTF and DE are shown in figure 3. After performing a
ROC analysis and calculating the AUC, the AUCs (95% CI) for DTF and DE
were 0.962 (0.911-1) and 0.880 (0.762-0.998), respectively. DTF and DE
had optimal cutoff points of 40.5 and 12.15 mm, respectively. Of the 26
patients who were successfully extubated, 22 had a DTF greater than
40.5%. Of the 16 who failed extubation, 14 had a DTF less than 40.5%.
DTF and DE were found to have a sensitivity and specificity of 91.67 %,
87.50 %, and 83.33 %, 81.25 %, respectively. The positive and
negative predictive value of DTF and DE were also shown in table 3.
Discussion
Point of care ultrasound is increasingly used in pediatric critical care
settings. Recently, ultrasound has been used to assess the diaphragm
functions17, identify VIDD20,
pneumonia and bronchiolitis23 and evaluate diaphragm
motions during spontaneous breathing trials21. When
DTF and DE were determined using DUS in the zone of apposition at the
end of the ERT, we found a significant difference between the SW and FE
groups. Although, these findings are similar to previous studies
evaluating the role of DUS on the weaning policy, this is the first
pediatric study evaluating DUS at the end of the ERT. Also, this study
showed that DUS findings were significantly differ between NIV
requirement and reintubated patients who were considered as extubation
failure. Additionally, the FE group had a statistically significantly
longer IMV duration, indicating that prolonged IMV duration was
associated with increased diaphragmatic atrophy.
Extubation failure is reported as high as 33% in some
studies6. The failure rate in our study was 40%,
which was significantly higher than the rate in other studies. This
difference could be explained by the fact that among all the patients
included only three (7.5%) required reintubation and the tendency in
our PICU practice to use NIV following extubation. With such high rate
of extubation failure and NIV requirement, it is obvious that, more
reliable tools are needed to anticipate weaning outcomes and identify
indications for NIV treatment. RSBI has been demonstrated to be accurate
in predicting extubation failure in adults24. However,
this index reflects the contribution of all inspiratory muscles, rather
than the diaphragm. In addition, due to different respiratory rates in
different ages and the tidal volume is weight-related, there is no
constant threshold for RSBI in children. CROP Index found by Thiagarajan
et al9, was a good predictor for successful
extubation, pediatric studies demonstrated that this index did not
reliably predict extubation failure in children25.
Although there are studies showing that volumetric capnography can also
predict the successful extubation in children, it is not widely used in
clinical practice10.
In mechanically ventilated children, inspiratory muscles especially
diaphragm weakens and VIDD occurs rapidly. Within the first week of IMV,
the diaphragm’s thickness decreases by more than 10%, and an increasing
percentage of muscle fat degrades muscle quality17.
After a few hours of ERT, the breathing pattern, which is usually normal
at the start, deteriorates. As such, we sought to determine whether
changes in diaphragm function at the conclusion of the ERT are an
accurate predictor of successful extubation.
Yoo et al, compared the predictive values of DE and DTF in adults, found
that best prediction thresholds for DE and DTF were 10-15 mm and 20-36%
respectively; the sensitivity and specificity for DE and DTF were
0.86-0.79, 0.90-0.80, respectively26. In our study, DE
of children was similar to adults: the optimal cut-off was 12.15 mm, DTF
of children was higher than adults: the optimal cut-off was 40.5%. This
is consistent with the clinical severity difference between FE groups
between two studies. They had more severe disease, and six required
tracheotomies, while five died during their intensive care unit stay.
However, only three of our patients required reintubation, and the
remaining thirteen were followed with NIV without reintubation. Lee et
al, found that DTF was significantly different between the successful
and failed extubation groups in children and a DTF value of
<17% was associated with extubation
failure17. Also, Ijland et al, found that over 90% of
children were successful extubated with a median DTF of
15.2%27. In both studies above, there were only 3
patients in the failed extubation groups, and those 3 patients were also
required reintubation. However, children who required reintubation had a
DTF value of less than 20% in our study.
Our study had some limitations. First, our population was relatively
small, despite the fact that we included a comparable number of patients
as previous studies17,18. Specifically, only three
patients in the FE group were reintubated, which precluded us from
revealing the DUS findings regarding the difference between NIV
requirement and reintubation. It has been demonstrated that the use of
NIV reduces the need for reintubation in children28.
It is necessary to conduct larger, multicenter studies comparing the DUS
findings in terms of NIV requirement, reintubation, and successful
extubation. Second, because no reference for DTF and DE in children has
been established, and in the absence of initial DUS findings prior to
IMV, it is difficult to determine whether the included children’s
initial diaphragmatic function was abnormal or not. Third, the
heterogeneity of the IMV indication limits the generalization of the
study results on general PICU patients.