Premature infants (infants born <37 weeks' gestational age) are discharged from the hospital and transported home in car seats designed for term babies. The safe transport of these premature infants is an important concern. Sub-optimal positioning in car seats can lead to breathing problems in premature infants. With the help of electrical impedance tomography, the investigators want to assess the changes in lung volume during the transition from a supine to a semi-upright position in the car seat.

Hypothesis The investigators hypothesise that there is a decrease in the end-expiratory lung volume (EELV) of preterm infants transferred from supine to car seat position. They expect that the curved, semi-upright built of a standard car seat negatively impacts lung aeration and ventilation of preterm infants, which may result in cardiorespiratory events. They also hypothesise that EELV will normalise following the repositioning of the infant back to the supine position.

Primary objective The primary objective of this study is to assess lung volume changes during the transition from a supine to a semi-upright position in a car seat in preterm infants.

Study procedures As soon as all inclusion criteria are met, the study intervention is initiated. For the baseline measurement, the child is placed in supine position on a flat surface. The EIT belt is attached at nipple level around the infant's thorax during the last nursing care before the start of the intervention. Continuous measurement is conducted for 30 minutes.

Subsequently, the child, with the EIT belt securely in place, is repositioned from a supine to a semi-upright position in a car seat, where another 30-minute measurement is taken. A third measurement will be conducted after the infant is returned to the standard supine position in his/her cot. Manipulations during the measurement periods will be kept to a minimum to avoid disruptions or artefacts in the data recordings. EIT data will be obtained for a total of 90 minutes (plus a maximum of 10 minutes for repositioning).

Subgroup analyses will be performed for the primary outcome:

• Preterm infants ≥ 32 versus < 32 weeks at birth
• Infants with a weight ≥ 2 kg versus < 2 kg at the time of the study
• Car seat positioning: nursing staff versus parents

Inclusion Criteria:

• Gestational age up to 36 6/7 weeks at birth and/or birthweight < 2.5 kg
• Preterm born infants fulfilling all criteria for discharge from the NICU
• Discharge home planned within 48 hours
• Written informed consent by one or both parents or legal guardians as documented by signature.

Exclusion Criteria:

• Severe malformation adversely affecting lung aeration or malformations limiting life expectancy.
• Inability of the parents to understand the study procedures due to cognitive or linguistic reasons.

This study will take place at the Department of Neonatology of the University Hospital Zurich. Preterm infants ready for discharge will be screened for eligibility and parents will be approached by the treating physician or a clinician-researcher who is authorized to access the patient's clinical data.