Table 1

Eligibility criteria and study definitions

Eligibility criteria
Inclusion criteria
  • Corrected age of <28 days

  • Caregivers were willing and able to provide informed consent and were available for follow-up for the duration of the study

Exclusion criteria
  • Receiving continuous positive airway pressure or mechanical ventilation

  • Skin abnormalities in the nasopharynx and/or oropharynx

  • Contraindication to skin sensor application

  • Known arrhythmia

  • Congenital abnormality requiring major surgical intervention

  • Any medical or psychosocial condition or circumstance that would interfere with study conduct or for which study participation could put the neonate’s health at risk

Study definitions
EpochA 60 s period of time
BreathOne cycle of neonate-initiated inhalation and exhalation
Breath startEnd of a waveform trough (low point) where the carbon dioxide level starts to ascend
Respiratory rate (RR) manual counting protocolA breath was counted if the waveform peak reached either 15 mmHg or the average peak of the epoch, AND the waveform trough dipped below the average trough of the epoch plus 10 mmHg
  • Each plot was counted by two independent readers and averaged

  • If the difference in the counts was >5, a third independent reader counted the plot

  • If the third count was within 5 breaths of either previous count, the average of the two closest counts was used

RR epoch exclusion criteriaRR epoch excluded if (i) the difference between the epoch count and median RR was >10, (ii) either value was <15, (iii) the capnogram contained a digital artefact or (iv) if there was lack of inter-reader manual count agreement
RR median calculationFor each breath in an epoch, an instantaneous RR could be calculated by the breath duration, and the median of all these instantaneous RR values in an epoch was then calculated
Heart rate (HR) median calculationHeart beats were identified by the timing of the Masimo Rad-97 reference device plethysmograph quality index (PO-SQI) which occur at the peak of each heart beat. For each heart beat in an epoch, an instantaneous HR could be calculated by the time between the previous heart beat peak and current heart beat peak, and the median of all these instantaneous HR values in an epoch was then calculated
Adequate signal qualityEarlySense device: A signal quality score ≥0.7 for at least 50% of the epoch
Masimo Rad-97 reference device: plethysmograph quality index (PO-SQI) threshold >150 for 100% of the epoch for HR, and capnography quality score (CO2-SQI) threshold ≥2 for at least 90% of the epoch for RR