Nurse:patient ratio and achievement of oxygen saturation goals in premature infants.

BACKGROUND: Premature newborns often experience oxygen saturations outside policy-specified targets, which may be associated with increased morbidity. Nurse workload may affect oxygen management.

OBJECTIVE: To examine the relationship between number of patients assigned to neonatal intensive care unit (NICU) nurses and achievement of oxygen saturation goals in premature newborns.

DESIGN: The authors linked nurse-patient assignment data with continuous oxygen saturation data for infants <29 weeks' gestation in a single NICU between January and June 2008. The proportion of time oxygen saturation was in policy-specified target range (85-92%) and proportion of time hyperoxaemic (98-100%) were determined for multiple 6 h monitoring periods. Each period was characterised by a single nurse, respiratory support mode and fraction of inspired oxygen (Fio(2)) level (0.22-0.49 or ≥0.5). The nurse:patient ratio for the infant's nurse for each monitoring period was determined. Factors associated with Spo(2) target achievement and hyperoxaemia were identified.

RESULTS: The authors analysed 1019 monitoring periods from 14 infants with a mean (SD) birth weight of 860 (270) g and gestational age of 26.6 (1.6) weeks. The mean (range) postmenstrual age for all monitoring periods was 31.6 (24.1-40.7) weeks. Eighty-seven nurses provided care. In a multivariate cross-classified hierarchical regression, the nurse:patient ratio, postmenstrual age, respiratory support mode and Fio(2) were significantly associated with oxygen saturation outcomes. Fewer patients per nurse was significantly associated with a higher saturation target achievement among patients on high-frequency ventilation, and with reduced hyperoxaemia among patients on nasal cannula.

CONCLUSIONS: Fewer patients per nurse may be associated with improved achievement of oxygen saturation goals and may be an important modifiable factor influencing oxygen-related outcomes in premature newborns. This effect may vary with mode of respiratory support.