EDITOR: Pulse oximetry has become a monitoring standard for anaesthesia and intensive care [1,2]. Knowledge of the basic principles, clinical and technical considerations, as well as an understanding of the oxyhaemoglobin dissociation curve is important [3-5]. We decided to evaluate how well medical and nursing personnel - who use pulse oximetry - understood it and their ability to interpret the information. A 17-item multiple choice questionnaire was prepared. The questions consisted of seven demographic items related to: place of work, years of experience in the use of pulse oximetry, and adequacy of training in pulse oximetry. The remaining 10 questions tested the knowledge of pulse oximetry. The topics and results are given in Table 1. Participation was voluntary and anonymous. Having agreed, the subjects were interviewed on the same day precluding any preparation.Table 1: Percentage of correct answers to the different questions Twelve residents and 44 nurses (comprising the total complement of staff in the ICU) completed the questionnaire and their responses were scored against answers obtained from standard reference texts. The response rate was 100%. The participants' experience is shown in Table 2. All residents had some degree of anaesthesiology training. Thirty-five of the nurses came from various surgical intensive care units (anaesthetic, neurosurgical, cardiovascular, general surgical intensive care units) and nine nurses were from a medical (neurological) intensive care unit. Although most (98%) used pulse oximetry regularly in their daily work, only 14% believed that they had had adequate training yet 70% felt sufficiently confident in using pulse oximetry. Half of them had 1-3 years of experience at work.Table 2: Duration of employment of residents and nurses The residents and nurses who believed they had received adequate education about pulse oximetry had worked for more than 3 years in their present job. We think that residents received instruction by the attending staff anaesthesiologists when pulse oximeters were originally introduced into routine clinical practice in this hospital. Subsequently, residents must have learned to interpret the findings of pulse oximetry by themselves or from their more senior colleagues. None of the nurses had received any formal education on this topic. Elsewhere first year residents also scored fewer points in a survey [6]. Although most of the participants (75%) knew what a pulse oximeter measures, only 14% understood its technological principles. Five of the 12 residents and four of the 44 nurses answered correctly. In a study by Kruger and Longden, six of 33 residents and one of 164 nurses answered correctly [7]. The questions concerning the relationship between PaO2 and SpO2 proved rather difficult; only two residents (4%) answered correctly. In the above mentioned study, 15 of the 33 residents and three of the 164 nurses knew the correct answer [7]. This suggests that the oxyhaemoglobin dissociation curve needs to be taught and explained in more detail. It should be stressed that when the value of SpO2 is 90%, PaO2 is approximately 60 mmHg. However, 43% of participants identified normal values for SpO2 and 54% of the participants recognized those for PaO2. Seventy-one per cent of the participants could explain why no reading is obtained if the patient had a cardiac arrest and how decreasing oxygen saturation would be observed after a respiratory arrest. Eighty per cent of the participants knew where the sensor (light probe) should be attached and 63% knew that there are different probes for adults and children. The normal saturation ranges for adults were identified by 19% and by 32% for children. Possibly more attention is paid to children or the participants perceive that there is a wider spectrum of normal values in adults [6]. The lower limit of reliability was incorrectly given as less than 70% SpO2 by 59% of the respondents (we took 85% as the correct answer). However, 14% of the participants could only name one factor, which may affect the accuracy of a pulse oximeter, whereas 86% were able to name two or more factors. The choice of factors included: hypothermia, poor peripheral perfusion (vasoconstriction or hypotension), problems with the light probe, nail polish, arrhythmia, shivering, or bright extraneous illumination, as taken from the responses in another study [8]. Hypothermia was most commonly indicated; peripheral vasoconstriction, hypotension, and disconnection of the probe were the other answers given in this study. The high proportion of incorrect answers indicating low knowledge levels could in some circumstances lead to more careful follow-up of patients due to misinterpreted alarms but would cause unnecessary alerts of anaesthetists or perhaps lead to inappropriate procedures. Other studies also show insufficient knowledge in less experienced staff [6]. More emphasis should be placed on teaching the principles of pulse oximetry with regular updates for the new recruits. H. BILGIN O. KUTLAY D. CEVHEROGLU G. KORFALI Department of Anesthesiology and Intensive Care Unit, Uludag University School of Medicine, Bursa, Turkey