This is a cross-sectional observational study, aiming to validate the accuracy of tidal breathing measurements in infants made by VoluSense Pediatrics, a lung function method based on electromagnetic inductance plethysmography, compared to an ultrasonic flowmeter. VoluSense Pediatrics consists of a flexible vest placed around the torso of the baby, and changes in tidal volume and flow is measured. The study will enable a better understanding of the usefulness of this equipment. The equipment is made by VoluSense Norway AS, and is owned by Haukeland University Hospital.