Table 6 Characteristics of children lost to follow up

N° of Subjects

56/259

18/99

χ² = 0.3434; p = 0.5579

Male/Female

27/29

8/10

χ² = 0.0766; p = 0.7819

 - Northern Italy

2/54

0/18

0.652; p = 0.4195

 - Central Italy

30/26

11/8

0.106; p = 0.7452

 - Southern Italy

22/34

7/11

0.0009; p = 0.9762

 - Outside Italy

2/54

0/18

0.652; p = 0.4195

Age at start of LTV (years)

4.7 (0.7–10.3)

9.0 (2.0–14.2)

p = 0.058729

 - NMDs

16/40

5/13

χ² = 0.00416; p = 0.9485

 - Upper airway diseases

27/29

0/18

χ² = 13.479; p = 0.0002

 - Lower airway diseases

5/51

4/14

χ² = 2.223; p = 0.1360

 - CNS diseases

1/55

7/11

χ² = 19.185; p < 0.0001

 - Abnormal ventilatory control

1/55

1/17

χ² = 0.726; p = 0.3941

 - Other

6/50

1/17

χ² = 0.418; p = 0.5182

Hours/day spent under mechanical ventilation (< 12/≥12)

50/6

7/11

χ² = 19.287; p < 0.0001

Home health care (yes/no)

3/53

18/0

χ² = 59.219; p < 0.0001