Groups
We divided the patients in two groups according to their response to
diuretics in terms of decreasing respiratory support (RS). We registered
RS at the time of each LU, and we categorized it as: invasive mechanical
ventilation (IMV), nasal intermittent positive pressure ventilation
(NIV), nasal continuous positive airway pressure (nCPAP), high flow
nasal cannula (HFNC) and none. As the diuretics’ effect in pulmonary
function tests have been described to occur as late as four weeks
afterwards 21, we compared the highest RS two weeks
before LU, with the lowest RS four weeks after LU.
- Responders: the lowest RS four weeks after diuretics is, at least, one
level lower than the higher RS two weeks before diuretics.
- Non-responders: the lowest RS four weeks after diuretics is the same
or worse than the highest RS two weeks before diuretics.
As the time at which infants required diuretics was different, we
centered the date of LU in the day when diuretics were started. We
created these groups of dates: ”32 days or more before diuretics” (B1),
”31-24 days before diuretics” (B2), ”23-16 days before diuretics” (B3),
” 15-8 days before diuretics” (B4), ”7-4 days before diuretics” (B5), ”3
days before to 1 day after diuretics” (T0), ”2 to 5 days after
diuretics” (A1), ”6 to 9 days after diuretics” (A2), ”10 to 17 days
after diuretics” (A3), ”18 to 25 days after diuretics” (A4), ”26 to 33
days after diuretics” (A5), ”34 or more days after diuretics” (A6).
BPD was defined according to Walsh et al. definition24: mild BPD (oxygen requirement for the first 28 days
but in room air at 36 weeks’ PMA), moderate BPD (oxygen requirement for
the first 28 days and oxygen <30% at 36 weeks’ PMA. A
room-air challenge was performed in these infants and only those that
failed the reduction (oxygen saturation 80-87% for 5 minutes, or
<80% for 1 minute) were diagnosed as moderate BPD), and
severe BPD (oxygen requirement for the first 28 days and oxygen
>30% or continuous positive airway pressure or mechanical
ventilation at 36 weeks’ PMA).