The main point of criticism of our study [1] by all
these readers is that we assessed only for benefits over the first hour
of admission. This is a valid point. The reason for such protocol was
the ethical issue. Theoretically, it was not logical to use CPAP (that
increases dead space [2]) to treat a condition like bronchiolitis, which
is characterized by air trapping [3]. This is why we decided to study
this modality for the first hour, while we closely monitored the child,
ready to switch to more conventional modalities if the baby’s distress
increased. Most babies did well on CPAP, and this was continued after
the 1-hour study period, but the protocol was to study distress
(improvement or deterioration) in the first hour. From this study over
the first hour, we were able to identify patients who improved with
CPAP. We know from our observation during the period that infants who
improved in the first hour were continued on CPAP and maintained the
benefits. However, we did not collect study data beyond the first hour.
Respiratory rate is variable but a reduction in respiratory rate is
usually a good sign of improvement.
Regarding inter-observer variability in counting the
respiratory rate, the counting of respiratory rate is a simple procedure
and we did not consider inter-observer variability to be significant
although we did not test for this. We do not consider video recording
would have been useful.
PEEP and flow rates are crucial factors in bubble
CPAP. We used flow rates between 6 L/min and 10 L/min, and PEEP of 6 cm
of water to 8 cm of water depending on the baby’s size and flow rates
that were comfortable for the baby.
The median and IQR values (Bubble CPAP vs
Standard care) in our study were as follows: Respiratory rate (8 (3.5,
12) vs 5 (2.3, 7.8); P=0.018), SA Score (1 (0, 1) vs
0 (0, 1); P=0.29) and MPSNZ-SS (2 (1, 3) vs. 1 (0, 2);
P=0.012).
Regarding our use of Silverman-Andersen score and
Modified Pediatric Society of New Zealand Severity Score to assess
respiratory distress in bronchiolitis, they have been widely used to
evaluate distress in infants.
We acknowledge we could have recorded anthropometric
data for comparison between cases and controls in this randomized trial
to demonstrate comparability between the groups, but this was not a part
of the study protocol.
References
1. Lal SN, Kaur J, Anthwal P, Bahl P, Puliyel JM.
Continuous positive airway pressure in bronchiolitis: A randomized
controlled trial. Indian Pediatr. 2018;55:27-30
2. Hishikawa K, Fujinaga H, Ito Y. Increased dead
space in face mask continuous positive airway pressure in neonates.
Pediatr Pulmonol. 2017;52:107-11.
3. Florin TA, Plint AC, Zorc JJ. Viral bronchiolitis. Lancet.
2017;389:211-24.