Table 1 Characteristics of the whole study population

Number of studied infants

110

Gestational age (weeks)

36

(27-40)

Birth weight (g)

2705

(960-4150)

Gender (male)

62

(56.4)

Preterm

75

(57.7)

Duration of mechanical ventilation (days)

0

(0-59)

Diagnoses on admission

Respiratory distress syndrome (RDS)

37

(33.6)

Transient tachypnea of the newborn (TTN)

17

(15.5)

Meconium aspiration syndrome

5

(4.5)

Infection

16

(14.5)

Congenital pneumonia

6

(5.5)

Prematurity (gestational age ≤ 34 weeks and birthweight < 2 kg without additional problems on admission)

15

(13.7)

Birth depression

6

(5.5)

Intrauterine growth retardation

5

(4.5)

Airleaks

2

(1.8)

Meconium plug

1

(0.9)

At the time of measurement

Postnatal age (days)

9

(1-107)

Postmenstrual age (PMA) (weeks)

37.1

(32.4-46.7)

Preterm (PMA<37 weeks)

57

(43.8)

Weight (g)

2633

(1850-4050)

cACE activity (U/L)

42.5

(16.7-89.0)

Pi_max (cmH₂O)

65.0

(36.9-91.8)

Pi_max/weight (cmH₂O/kg)

24.5

(14.5-47.1)

PTImus

0.062

(0.023-0.149)