Do clinicians know how to use pulse oximetry? A literature review and clinical implications

Pulse oximerry has become one of the most commonly used tools in the clinical environment for assessing patients' oxygenation status. It is employed almost continuously in critical care areas and frequently in the general ward environment. Although it is a much better tool for determining hypoxia than the human eye, its use is limited if clinicians do not understand relevant physiological principles, such as the oxyhaemoglobin dissociation curve and the inherent limitations of the device. Furthermore, the risk for compromised patient safety is significant if clinicians fail to recognise the potential for false or erroneous readings. This paper explores the research which has examined clinicians' comprehension of pulse oximetry. Fourteen studies examining clinicians' knowledge of pulse oximerry were reviewed. These studies revealed significant knowledge deficits about pulse oximerry amongst nurses, doctors and allied health professionals, all of whom used this technology frequently. Alarmingly, those lacking an adequate understanding of pulse oximerry included senior, experienced clinicians. The studies were limited by their use of convenience sampling and small sample sizes. Further research is needed to better understand the significance of this problem and to examine how principles of pulse oximerry are taught to nurses and other health professionals at the undergraduate and postgraduate levels. Educators and clinicians alike must ensure that a safe level of knowledge for the use of pulse oximerry is maintained in order to ensure that patient outcomes are not compromised.

Maternal and neonatal influences on, and reproducibility of, neonatal aortic pulse wave velocity

Aortic pulse wave velocity (aPWV), a noninvasive measure of vascular stiffness, is an independent predictor of cardiovascular disease both before and in overt vascular disease. Its characteristics in early life and its relationship to maternal factors have hardly been studied. To test the hypothesis that infant aPWV was positively related to maternal anthropometry and blood pressure (BP) at 28 weeks gestation, after adjusting for neonatal anthropometry and BP, 148 babies born in Manchester were measured 1 to 3 days after birth. A high reproducibility of aPWV, assessed in 30 babies within 3 days of birth, was found with a mean difference between occasions of –0.04 m/s (95% CI: –0.08 to 0.16 m/s). Contrary to our hypothesis, a significant inverse relation was found between neonatal aPWV (mean: 4.6 m/s) and maternal systolic BP (mean: 108.9 mm Hg; r=–0.57; 95% CI: –0.67 to –0.45) but not maternal height nor weight. Neonatal aPWV was positively correlated with birth length, birth weight, and systolic BP. In multiple regression, neonatal aPWV remained significantly inversely associated with maternal systolic BP (adjusted ß coefficient: –0.032; 95% CI: –0.040 to –0.024; P<0.001), after adjustment for maternal age, birth weight, length, and neonatal BP (all independently and positively related to aPWV) and for gestational age, maternal weight, and height (unrelated). These results suggest that infant aPWV may be a useful index of infant vascular status, is less disturbing to measure than infant BP, and is sensitive to the gestational environment marked by maternal BP.

Low actuation-voltage shift in MEMS switch using ramp dual-pulse

This paper proposes a ramp dual-pulse actuation-voltage waveform that reduces actuation-voltage shift in capacitive microelectromechanical system (MEMS) switches. The proposed waveform as well as two reported waveforms (dual pulse, and novel dual-pulse) are analyzed using equivalent-circuit and equation models. Based on the analysis outcome, the paper provides a clear understanding of trapped charge density in the dielectric. The results show that the proposed actuation-voltage waveform successfully reduces trapped charge and increases lifetime due to lowering of actuation-voltage shift. Using the proposed actuation-voltage waveform, the membrane reaches a steady state on the electrode faster.