Methods
This was a single-centre, prospective, within-subject, observational study, reported using the Strengthening the Reporting of Observational Studies in Epidemiology guidelines.14 15 Participants were a subset of infants born <30 weeks' gestation between January 2011 and December 2013, recruited as part of a larger serial neurobehaviour study from the neonatal nurseries at the Royal Women’s Hospital in Melbourne, a tertiary level neonatal intensive and special care unit.16 Infants were excluded if they had congenital abnormalities known to affect neurodevelopment, had non-English-speaking parents, or who were medically unstable. Informed parental consent was obtained for all participants.
The physiological stress imposed by standardised neurobehavioural assessments was compared with that during clustered nursing cares. Three standardised neurobehavioural assessments, the General Movements Assessment (GM),17 the Premie-Neuro Assessment (PN)18 and the Hammersmith Neonatal Neurological Examination (HNNE),19 were administered weekly from birth until 32 weeks’ postmenstrual age.16 The PN and the HNNE were chosen to provide neurological and neurobehavioural data required for the main study. The GMs were chosen to provide further neurological information through observation alone.
Assessments were timed with clustered nursing cares, classified as any task or procedure necessary for the continued ongoing daily care of the infant, performed by a parent, nursing staff or a combination of the two. Neurobehavioural assessments were administered by trained and certified assessors following a standardised procedure,16 commencing with the GMs, which involved only videoing the infant’s spontaneous movement in supine for approximately 5 min, then the PN and the HNNE, as tolerated by the infant. The PN and HNNE both involve handling the infant and share numerous items. To minimise repeated handling and accumulative stress, shared items were administered once during the PN, with only the additional items captured in the HNNE, which was administered last. Clustered nursing cares usually took precedence over the standardised neurobehavioural assessments, as they are an essential component of care. The bedside nurse determined the order based on the infant’s needs and their workload.
All assessments and nursing cares were video recorded using a digital video camera mounted on a portable pole and positioned above the incubator/open cot, avoiding the infant’s direct vision and allowing staff access. A pulse oximeter sensor (LNOP Neo-L, Masimo, Irvine, CA, USA) was placed around the infant’s foot or wrist and connected to an oximeter (Masimo SET, Masimo). The pulse oximeter was set to maximum sensitivity with 2 s averaging to provide rapid detection of changes in oxygen saturation (SpO2), heart rate (HR) and signal quality. The pulse oximeter was positioned inside the incubator/open cot within the camera’s view to monitor HR and SpO2.
Recordings containing both clustered nursing cares and standardised neurobehavioural assessments completed between 29 and 32 weeks’ postmenstrual age were reviewed by the first author (LGA). Videos were excluded if the pulse oximeter was out of camera view, had distorted readings, or was obstructed by anything or anyone (assessors/infants/nursing staff/parents). Video contents were divided into individual nursing cares and individual standardised neurobehavioural assessments by recording start/finish times for each. Videos were analysed by an independent research assistant (ALE), blinded to the infant’s clinical history and knowledge of who was completing the cares or assessments. HR, SpO2, plethysmograph wave, signal identification and quality indicator (signal IQ) and alarm message data were extracted at 5 s intervals during the assessment/care by ALE, and entered into a Microsoft Excel spreadsheet by LGA. During data extraction, motion artefact was determined visually by viewing the pulse amplitude indicator or signal IQ. Only data with good plethysmograph wave and good signal quality with no alarm message (low signal IQ, low perfusion, sensor off or ambient light) were included in the analysis.
The need for nasal continuous positive airway pressure (nCPAP) at the time of clustered nursing cares and neurobehavioural assessments was also recorded as it was considered to be a potential confounding variable that might influence the infant’s tolerance to handling, particularly as it was sometimes removed to allow the infant to move freely during recording of the GMs.
The main outcomes of interest were HR measured as beats per minute (bpm) and SpO2 (%). The occurrence of HR instability, including tachycardia (HR>180 bpm20 21) and bradycardia (HR<100 bpm), was also of interest, as was oxygen desaturation, defined as SpO2<90%.
A sample size of 34 infants was required to find a difference in means between clustered nursing cares and standardised neurobehavioural assessments on a two-sided paired t-test of 0.5 SD and greater, with 81% power and a type-I error of 0.05 assuming one observation for each assessment type per participant.
Statistical analysis
Stata V.13 was used to analyse the data.22 HR and SpO2 were compared between clustered nursing cares and standardised neurobehavioural assessments using linear regression, fitted using generalised estimating equations (GEE) to allow for multiple observations within individual participants. Results are presented as mean differences, 95% CIs and P values. The occurrence of physiological instability for HR and SpO2 was compared between assessment types using logistic regression fitted using GEEs. Results are presented as ORs, 95% CIs and P values. The same outcomes were compared between the standardised neurobehavioural assessments that required handling (PN and HNNE) and the one that did not (GMs), using similar linear and logistic regression models. Analyses were repeated adjusting for the use of nCPAP during clustered nursing cares and standardised neurobehavioural assessments and for the protocol order of cares versus assessments.