The Impact of Nurse to Patient Ratio on Healthcare Quality
The Impact of Nurse to Patient Ratio on Healthcare Quality
It would be hard to understate the importance of a high nurse to patient ratio (NPR) for patient and staff safety, as well as quality of care. While there are a number of different nursing factors that can influence these outcomes, including nursing education, experience, skills mix, contact time, frequency of interactions, and type of inpatient unit, the NPR has been the focus of considerable interest in part because it can be easily quantified (reviewed by Sidani, Manojlovich, and Covel, 2010). This review will examine the empirical evidence for the importance of NPR in determining patient and staff safety, as well as quality of care. Towards this goal, research articles obtained from the Library of Medicine will be reviewed in detail and compared to the findings of more recent research studies. This approach is intended to establish a historical foundation for this topic and then use it for elaborating on the different variables that influence the predictive value of the NPR.
When the Institute of Medicine (2000) published their report on patient safety, To Err is Human, the American public woke up to the hidden reality that hospitals can be bad for patient health. The authors of this report estimated that between 44,000 and 98,000 people died each year as a result of medical errors. To put these numbers into perspective, this is more deaths than those caused by vehicle accidents, breast cancer, or AIDS.
In the aftermath of the Institute of Medicine report, Aiken and colleagues (2002) published a large study in the Journal of the American Medical Association revealing NPR to be a significant contributor to medical errors. Included in the study were 168 Pennsylvania general hospitals encompassing 232,342 patients and 10,184 nurses. The NPRs were broken down into less than or equal to 1:4 (11.9%), 1:5 (38.1%), 1:6 (24.4%), 1:7 (17.3%), and 1:8 or greater (8.3%). Based on the discharge abstracts for the patients included in the study, 23.2% experienced a major complication that emerged after being admitted to the hospital and another 2.0% died within a month. All patients were admitted for surgery: orthopedic (51.2%), gastrointenstinal (36.4%), and other (12.4%).
The main factors investigated in the study by Aiken and colleagues (2002) were the relationship between NPR and nurse burnout and patient adverse events. Their data reveal that for every patient increase in the NPR, nurses were 23% and 15% more likely to report feeling burned out and dissatisfied with their job experience, respectively. Every increase in NPR by one patient also increased the risk that a patient would die by 7%. To put this last estimate in perspective, increasing the NPR from 4:1 to 8:1 would result in 18.2 and 5.0 excess deaths per 1000 patients with and without complications, respectively. While there are some limitations to this study, including a hospital selection bias and the inclusion of only a few confounding factors, the large representative sample the authors were able to obtain created a high degree of confidence in their findings.
In support of Aiken and colleague's (2002) findings, a number of studies have investigated the same issue during the years since the Pennsylvania hospital study was published. However, none have conducted a controlled study of an intentional change in staffing levels. To get around these limitations, researchers have taken advantage of below target staffing levels to see if this tended to increase adverse outcomes for patients within the same hospital. By taking this approach, such variables as differences in organizational attitudes, the quality of nursing staff, and other variables would be minimized or eliminated.
This approach was taken by Needleman and colleagues (2011) at a major medical center when they examined almost 200,000 records for adult patient admissions to see whether there was an association between units operating with below target staffing levels and increased patient mortality. They also controlled for a number of other confounding factors, such as day vs. night shift and type of unit, and purposely selected a well-respected, high quality tertiary care hospital with a low NPR. Taking this approach allowed them to ascertain whether subtle changes in nurse staffing levels had a negative impact on patient safety. They also controlled for the impact that patient turnover would have on nursing load and patient mortality.
Staffing levels were generally found to be near target levels for most units, but 16% were more than 8 hours below target, including over 19% of ICUs (Needleman et al., 2011). Differences between daytime and nighttime staffing were limited to step-down and general care units, with higher staffing levels in the daytime. After adjusting for selected confounding factors, the authors found that the risk of death increased significantly [Hazard Ratio (HR) = 1.02, 95% CI, 1.01-1.03, p < 0.001] if staffing levels dropped more than 8 hours below target levels or a shift experienced high patient turnover (HR = 1.04, 95% CI, 1.03-1.10, p < 0.001). Both results are consistent with the theory that any factors that increase nursing workloads will tend to have a negative impact on patient safety, including NPR.
The study by Needleman and colleagues (2011) revealed how patient safety can be degraded when the NPR does not meet target goals in a high-quality hospital, but it also revealed that more subtle changes in nurse workload can still have a significant negative impact on patient mortality rates. What this implies is that NPR functions as a healthcare quality indicator because it has a dramatic impact on nurse workload.
One of these aspects is the ratio of nursing training and expertise, such that an increased percentage of well-trained and experienced nurses would tend to decrease negative patient outcomes. This implies that more nursing assistants will not make up for a lack of RNs and LPNs. A longitudinal and cross-sectional study in Australia examined the effect of an equivalent RN:LPN:NA ratio in randomly selected medical, surgical, ICU, and emergency units in 19 hospitals (Duffield et al., 2011). The percent RNs ranged from a low of 45% to a high of 100%. The nursing workload and demand was calculated, such that a score of 100 indicated a balance. Among all units, about 25% had scores of 100 or less, which implies that nursing workload was above recommended levels for 75% of all units, with the highest score reaching 250. NPRs varied from 1:6 to 1:10, but the RN to patient ratio averaged around 1:8.
The longitudinal arm of the study revealed that over the 5-year study period, units that experienced a higher percentage of RNs (including clinical nursing specialists) had lower rates of patient adverse events (Duffield et al., 2011). The three patient outcomes significantly associated with a low RN to patient ratio was bedsores, pneumonia, and sepsis (p ? 0.01). Other factors that significantly influenced patient outcomes in a negative manner were patient turnover rates, temporary vs. permanent nursing staff, threats of physical violence, and patient acuity. All these factors tend to reduce the effective nurse staffing level for a unit because they increase the workload on nursing staff. These findings reveal that the importance of NPR to patient safety depends on more than simply having a nurse attending to a patient's needs, but also the skills level of the nurse.
A similar study was conducted by Patrician and colleagues (2011a) in 13 U.S. military hospitals. They discovered that the percentage of RNs made a difference on patient safety when measured in terms of falls, falls with injury, and medical errors, but in a more nuanced way. The analysis was broken down into three types of medical units: medical-surgical, step-down, and critical care. Each 10% increase in RN percentage reduced falls in medical-surgical and critical care units by 30% and 36%, respectively. The training and experience of the RN also mattered, since each 10% decrease in the presence of a civilian RN increased the chance of a fall by 33-48% and medical errors by up to 67%. The other RNs on staff were military, contractor, and reservist. The reason civilian nurses provided a significant advantage to patient safety was because their average experience level was 14 years, compared to 5 years for military nurses. A higher NPR reduced both falls and falls with injury. In addition, most falls occurred during night shifts. Reduced medical errors were associated with more RNs and civilian RNs per shift, higher NPR, and night shift.
Patrician and colleagues (2011a) admit that there are several weaknesses to their study, including a reliance on the more controversial incident reports. Such reports are viewed by many researchers as an invalid measure because incidents tend to be underreported for fear of reprisal and litigation. The other weaknesses mentioned were not adjusting for differences in the risk of falling and medical errors for patients, but the authors argue that dividing up the data by unit type tended to provide an equivalent…