The impact of the nursing workforce on patient outcomes in intensive care

Introduction: Evidence from studies conducted mainly in the US and mainland Europe suggests that characteristics of the workforce, such as nurse patient ratios and workload (measured in a number of different ways) may be linked to variations in patient outcomes across health care settings (Carmel and Rowan 2001). Few studies have tested this relationship in the UK thus questions remain about whether we are justified in extrapolating evidence from studies conducted in very different health care systems. Objectives: To investigate whether characteristics of the nursing workforce affect patient mortality UK Intensive Care Units. Data: Patient data came from the case mix programme, Intensive Care National Audit and Research Centre (ICNARC), while information about the units came from a survey of all ICUs in England (Audit Comission 1998). The merged data set contained information on 43,859 patients in 69 units across England. ICNARC also supplied a risk adjustment variable to control for patient characteristics that are often the most important determinants of survival. Methods: Multivariate multilevel logistic regression. Findings: Higher numbers of direct care nurses and lower scores on measures of workload(proportion of occupied beds at the time the patient was admitted and mean daily transfers into the unit) were associated with lower mortality rates. Furthermore, the effect of the number of direct care nurses was greatest on the life chances of the patients who were most at risk of dying. Implications: This study has wide implications for workforce policy and planning because it shows that the size of the nursing workforce is associated with mortality (West et al 2006). Few studies have demonstrated this relationship in the UK. This study has a number of strengths and weaknesses and further research is required to determine whether this relationship between the nursing workforce and patient outcomes is causal.

Call admission control algorithms in OFDM-based wireless multiservice networks

Orthogonal frequency division multiplexing(OFDM) is becoming a fundamental technology in future generation wireless communications. Call admission control is an effective mechanism to guarantee resilient, efficient, and quality-of-service (QoS) services in wireless mobile networks. In this paper, we present several call admission control algorithms for OFDM-based wireless multiservice networks. Call connection requests are differentiated into narrow-band calls and wide-band calls. For either class of calls, the traffic process is characterized as batch arrival since each call may request multiple subcarriers to satisfy its QoS requirement. The batch size is a random variable following a probability mass function (PMF) with realistically maximum value. In addition, the service times for wide-band and narrow-band calls are different. Following this, we perform a tele-traffic queueing analysis for OFDM-based wireless multiservice networks. The formulae for the significant performance metrics call blocking probability and bandwidth utilization are developed. Numerical investigations are presented to demonstrate the interaction between key parameters and performance metrics. The performance tradeoff among different call admission control algorithms is discussed. Moreover, the analytical model has been validated by simulation. The methodology as well as the result provides an efficient tool for planning next-generation OFDM-based broadband wireless access systems.