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BackgroundHeart surgery patients are more at risk of poor peripheral perfusion, and peripheral capillary oxygen saturation (SpO2) measurement is regular care for continuous analysis of blood oxygen saturation in these patients. With regard to controversial studies on accuracy of the current pulse oximetry probes and lack of data related to patients undergoing heart surgery, the present study was conducted to determine accuracy of pulse oximetry probes of finger, toe, forehead and earlobe in detection of oxygen saturation in patients admitted to intensive care units for coronary artery bypass surgery.MethodsIn this clinical trial, 67 patients were recruited based on convenience sampling method among those admitted to intensive care units for coronary artery bypass surgery. The SpO2 value was measured using finger, toe, forehead and earlobe probes and then compared with the standard value of arterial oxygen saturation (SaO2). Data were entered into STATA-11 software and analyzed using descriptive, inferential and Bland-Altman statistical analyses.ResultsHighest and lowest correlational mean values of SpO2 and SaO2 were related to finger and earlobe probes, respectively. The highest and lowest agreement of SpO2 and SaO2 were related to forehead and earlobe probes.ConclusionThe SpO2 of earlobe probes due to lesser mean difference, more limited confidence level and higher agreement ration with SaO2 resulted by arterial blood gas (ABG) analysis had higher accuracy. Thus, it is suggested to use earlobe probes in patients admitted to the intensive care unit for coronary artery bypass surgery.Trial registrationRegistration of this trial protocol has been approved in Iranian Registry of Clinical Trials at 2018–03-19 with reference IRCT20100913004736N22. “Retrospectively registered.”

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In the present study, the interpenetrated polymer networks (IPN) foams of polyurethane (PU) and poly(methyl methacrylate) (PMMA) with different ratio of PU/PMMA (i.e. 85/15, 75/25 and 65/35) were prepared using the polymerisation process. The acoustical, damping and thermal properties of synthesised IPN foams with regard to different compositions were studied. As indicators of effective damping capability, viscoelastic parameters including loss factor (tan δ), glass transition temperature (T g ) and effective damping interval (tan δ > 0.3) were also determined. The results show that the T g shifted to higher temperature ranges, and the damping temperature range (tan δ > 0.3) increased when the IPN was formed. The sound absorption coefficient results show that because of the formation of IPN, the soundabsorbing capacity of prepared samples increased at a certain frequency, and the resonance frequency shifted to lower frequencies by increasing the PMMA content in IPN foams.