The Dewey Monitor: Pulse Oximetry can Warn of Hypoxia in an Immersed Rebreather Diver in Multiple Scenarios.

Divers who wish to prolong their time underwater while carrying less equipment often use devices called rebreathers, which recycle the gas expired after each breath instead of discarding it as bubbles. However, rebreathers' need to replace oxygen used by breathing creates a failure mechanism that can and frequently does lead to hypoxia, loss of consciousness, and death. The purpose of this study was to determine whether a pulse oximeter could provide a useful amount of warning time to a diver with a rebreather after failure of the oxygen addition mechanism. Twenty-eight volunteer human subjects breathed on a mixed-gas rebreather in which the oxygen addition system had been disabled. The subjects were immersed in water in four separate environmental scenarios, including cold and warm water, and monitored using pulse oximeters placed at multiple locations. Pulse oximeters placed on the forehead and clipped on the nasal ala provided a mean of 32 s (±10 s SD) of warning time to divers with falling oxygen levels, prior to risk of loss of consciousness. These devices, if configured for underwater use, could provide a practical and inexpensive alarm system to warn of impending loss of consciousness in a manner that is redundant to the rebreather.

Non-invasive monitoring of carboxyhemoglobin during hyperbaric oxygen therapy.

Introduction: This study aimed to assess the capability of a pulse CO-oximeter to continuously monitor carboxyhemoglobin (COHb) during hyperbaric oxygen (HBO2) therapy. We estimated limits of agreement (LOA) between blood gas analysis and pulse CO-oximeter for COHb during HBO2 therapy in patients suffering from acute CO poisoning. Furthermore, we did a medicotechnical evaluation of the pulse CO-oximeter in hyperbaric conditions. Methods: We conducted a prospective, non-clinical, observational study in which we included n=10 patients with acute CO poisoning referred for HBO2 therapy. We did five repeated measurements of COHb for each patient during the HBO2 therapy. Bland-Altman analysis for multiple observations per individual was used to assess the agreement. The a priori LOA was ±6% for COHb. For the medicotechnical evaluation continuous measurements were obtained throughout each complete HBO2 therapy. The measurements were visually inspected and evaluated. Results: The Bland-Altman analysis showed that the pulse CO-oximeter overestimated COHb by 2.9 % [±1.0%] and the LOA was ±7.3% [±1.8%]. The continuous measurements by pulse CO-oximetry showed fluctuating levels of COHb and summarized saturations reached levels above 100%. Measurements were not affected by changes in pressure. Conclusion: To our knowledge, this study is the first to assess LOA and demonstrate use of a non-invasive method to measure COHb during HBO2 therapy. The pulse CO-oximeter performed within the manufactures reported LOA (±6%) despite hyperbaric conditions and was unaffected by changes in pressure. However, summarized saturations reached levels above 100%.

Evaluation of an enhanced pulse oximeter auditory display: a simulaion study.

BACKGROUND: We compared anaesthetists' ability to identify haemoglobin oxygen saturation (SpO2) levels using two auditory displays: one based on a standard pulse oximeter display (varying pitch plus alarm) and the other enhanced with additional sound properties (varying pitch plus tremolo and acoustic brightness) to differentiate SpO2 ranges. METHODS: In a counter-balanced crossover study in a simulator, 20 experienced anaesthetists supervised a junior colleague (an actor) managing two airway surgery scenarios: once while using the enhanced auditory display and once while using a standard auditory display. Participants were distracted with other tasks such as paperwork and workplace interruptions, but were required to identify when SpO2 transitioned between pre-set ranges (target, low, critical) and when other vital signs transitioned out of a target range. They also identified the range once a transition had occurred. Visual displays were available for all monitored vital signs, but the numerical value for SpO2 was excluded. RESULTS: Participants were more accurate and faster at detecting transitions to and from the target SpO2 range when using the enhanced display (100.0%, 3.3 s) than when using the standard display plus alarm (73.2%, 27.4 s) (P<0.001 and P=0.004, respectively). They were also more accurate at identifying the SpO2 range once a transition had occurred when using the enhanced display (100.0%) than when using the standard display plus alarm (57.1%; P<0.001). CONCLUSIONS: The enhanced auditory display helps anaesthetists judge SpO2 levels more effectively than current auditory displays and may facilitate 'eyes-free' monitoring.

Comparison of Standard and Enhanced Pulse Oximeter Auditory Displays of Oxygen Saturation: A Laboratory Study With Clinician and Nonclinician Participants.

BACKGROUND: When engaged in visually demanding tasks, anesthesiologists depend on the auditory display of the pulse oximeter (PO) to provide information about patients' oxygen saturation (SpO2). Current auditory displays are not always effective at providing SpO2 information. In this laboratory study, clinician and nonclinician participants identified SpO2 parameters using either a standard auditory display or an auditory display enhanced with additional acoustic properties while performing distractor tasks and in the presence of background noise. METHODS: In a counterbalanced crossover design, specialist or trainee anesthesiologists (n = 25) and nonclinician participants (n = 28) identified SpO2 parameters using standard and enhanced PO auditory displays. Participants performed 2 distractor tasks: (1) arithmetic verification and (2) keyword detection. Simulated background operating room noise played throughout the experiment. Primary outcomes were accuracies to (1) detect transitions to and from an SpO2 target range and (2) identify SpO2 range (target, low, or critical). Secondary outcomes included participants' latency to detect target transitions, accuracy to identify absolute SpO2 values, accuracy and latency of distractor tasks, and subjective judgments about tasks. RESULTS: Participants were more accurate at detecting target transitions using the enhanced display (87%) than the standard display (57%; odds ratio, 7.3 [95% confidence interval {CI}, 4.4-12.3]; P < .001). Participants were also more accurate at identifying SpO2 range using the enhanced display (86%) than the standard display (76%; odds ratio, 2.7 [95% CI, 1.6-4.6]; P < .001). Secondary outcome analyses indicated that there were no differences in performance between clinicians and nonclinicians for target transition detection accuracy and latency, SpO2 range identification accuracy, or absolute SpO2 value identification. CONCLUSIONS: The enhanced auditory display supports more accurate detection of target transitions and identification of SpO2 range for both clinicians and nonclinicians. Despite their previous experience using PO auditory displays, clinicians in this laboratory study were no more accurate in any SpO2 outcomes than nonclinician participants.

The Effect of Swaddling on Pain, Vital Signs, and Crying Duration during Heel Lance in Newborns.

To determine the effect of swaddling on pain, vital signs, and crying duration during heel lance in the newborn. This was a randomized controlled study of 74 (control: 37, experiment: 37) newborns born between December 2013 and February 2014 at the Ministry of Health Bagcilar Training and Research Hospital. An information form, observation form, and Neonatal Infant Pain Scale were used as data collection tools. Data from the pain scores, peak heart rates, oxygen saturation, total crying time, and duration of the procedure were collected using a video camera. Newborns in the control group underwent routine heel lance, whereas newborns in the experimental group underwent routine heel lance while being swaddled by the researcher. The newborns' pain scores, peak heart rates, oxygen saturation values, and crying durations were evaluated using video recordings made before, during, and 1, 2, and 3 minutes after the procedure. Pain was assessed by a nurse and the researcher. No statistically significant difference was found in the characteristics of the two groups (p > .05). The mean pain scores of swaddled newborns during and after the procedure were lower than the nonswaddled newborns (p < .05). In addition, crying duration of swaddled newborns was found to be shorter than the nonswaddled newborns (p < .05). The average preprocedure peak heart rates of swaddled newborns were higher (p < .05); however, the difference was not significant during and after the procedure (p > .05). Although there was no significant difference in oxygen saturation values before and during the procedure (p > .05), oxygen saturation values of swaddled newborns were higher afterward (p < .05). For this study sample, swaddling was an effective nonpharmacologic method to help reduce pain and crying in an effort to soothe newborns. Although pharmacologic pain management is the gold standard, swaddling can be recommended as a complementary therapy for newborns during painful procedures. Swaddling is a quick and simple nonpharmacologic method that can be used by nurses to help reduce heel stick pain in newborns.

Use of near-infrared spectroscopy (NIRS) in cerebral tissue oxygenation monitoring in neonates.

Near-infrared spectroscopy (NIRS) is a technology capable of non-invasive, continuous measuring of regional tissue oxygen saturation (StO2). StO2 represents a state of hemodynamic stability, which is influenced by many factors. Extensive research has been done in the field of measuring StO2 of various organs. The current clinical availability of several NIRS-based devices reflects an important development in prevention, detection and correction of discrepancy in oxygen delivery to the brain and vital organs. Managing cerebral ischemia remains a significant issue in the neonatal intensive care units (NICU). Cerebral tissue oxygenation (cStO2) and cerebral fractional tissue extraction (cFTOE) are reported in a large number of clinical studies. This review provides a summary of the concept of function, current variability of NIRS-based devices used in neonatology, clinical applications in continuous cStO2 monitoring, limitations, disadvantages, and the potential of current technology.

Combined spiroergometry and 31 P-MRS of human calf muscle during high-intensity exercise.

Simultaneous measurements of pulmonary oxygen consumption (VO2 ), carbon dioxide exhalation (VCO2 ) and phosphorus magnetic resonance spectroscopy (31 P-MRS) are valuable in physiological studies to evaluate muscle metabolism during specific loads. Therefore, the aim of this study was to adapt a commercially available spirometric device to enable measurements of VO2 and VCO2 whilst simultaneously performing 31 P-MRS at 3 T. Volunteers performed intense plantar flexion of their right calf muscle inside the MR scanner against a pneumatic MR-compatible pedal ergometer. The use of a non-magnetic pneumotachograph and extension of the sampling line from 3 m to 5 m to place the spirometric device outside the MR scanner room did not affect adversely the measurements of VO2 and VCO2 . Response and delay times increased, on average, by at most 0.05 s and 0.79 s, respectively. Overall, we were able to demonstrate a feasible ventilation response (VO2 = 1.05 ± 0.31 L/min; VCO2 = 1.11 ± 0.33 L/min) during the exercise of a single calf muscle, as well as a good correlation between local energy metabolism and muscular acidification (τPCr fast and pH; R2 = 0.73, p < 0.005) and global respiration (τPCr fast and VO2 ; R2  = 0.55, p = 0.01). This provides improved insights into aerobic and anaerobic energy supply during strong muscular performances.

Advanced Uses of Pulse Oximetry for Monitoring Mechanically Ventilated Patients.

Pulse oximetry is an undisputable standard of care in clinical monitoring. It combines a spectrometer to detect hypoxemia with a plethysmograph for the diagnosis, monitoring, and follow-up of cardiovascular diseases. These pulse oximetry capabilities are extremely useful for assessing the respiratory and circulatory status and for monitoring of mechanically ventilated patients. On the one hand, the key spectrography-derived function of pulse oximetry is to evaluate a patient's gas exchange that results from a particular ventilatory treatment by continuously and noninvasively measuring arterial hemoglobin saturation (SpO2). This information helps to maintain patients above the hypoxemic levels, leading to appropriate ventilator settings and inspired oxygen fractions. However, whenever higher than normal oxygen fractions are used, SpO2 can mask existing oxygenation defects in ventilated patients. This limitation, resulting from the S shape of the oxyhemoglobin saturation curve, can be overcome by reducing the oxygen fraction delivered to the patient in a controlled and stepwise manner. This results in a SpO2/FIO2 diagram, which allows a rough characterization of a patient's gas exchange, shunt, and the amount of lung area with a low ventilation/perfusion ratio without the need of blood sampling. On the other hand, the photoplethysmography-derived oximeter function has barely been exploited for the purpose of monitoring hemodynamics in mechanically ventilated patients. The analysis of the photoplethysmography contour provides useful real-time and noninvasive information about the interaction of heart and lungs during positive pressure ventilation. These hemodynamic monitoring capabilities are related to both the assessment of preload dependency-mainly by analyzing the breath-by-breath variation of the photoplethysmographic signals-and the analysis of arterial impedance, which examines the changes in the plethysmographic amplitude, contour, and derived indexes. In this article, we present and describe these extended monitoring capabilities and propose a more holistic monitoring concept that takes advantage of these advanced uses of pulse oximetry in the monitoring of ventilated patients. Today's monitors need to be improved if such novel functionalities were to be offered for clinical use. Future developments and clinical evaluations are needed to establish the true potential of these advanced monitoring uses of pulse oximetry.

Battery-free, stretchable optoelectronic systems for wireless optical characterization of the skin.

Recent advances in materials, mechanics, and electronic device design are rapidly establishing the foundations for health monitoring technologies that have "skin-like" properties, with options in chronic (weeks) integration with the epidermis. The resulting capabilities in physiological sensing greatly exceed those possible with conventional hard electronic systems, such as those found in wrist-mounted wearables, because of the intimate skin interface. However, most examples of such emerging classes of devices require batteries and/or hard-wired connections to enable operation. The work reported here introduces active optoelectronic systems that function without batteries and in an entirely wireless mode, with examples in thin, stretchable platforms designed for multiwavelength optical characterization of the skin. Magnetic inductive coupling and near-field communication (NFC) schemes deliver power to multicolored light-emitting diodes and extract digital data from integrated photodetectors in ways that are compatible with standard NFC-enabled platforms, such as smartphones and tablet computers. Examples in the monitoring of heart rate and temporal dynamics of arterial blood flow, in quantifying tissue oxygenation and ultraviolet dosimetry, and in performing four-color spectroscopic evaluation of the skin demonstrate the versatility of these concepts. The results have potential relevance in both hospital care and at-home diagnostics.

Pulse oximeters to self monitor oxygen saturation levels as part of a personalised asthma action plan for people with asthma.

BACKGROUND: We became aware through talking with people with asthma that some are using pulse oximeters to monitor their own blood oxygen levels during an asthma attack. Pulse oximeters are marketed by some suppliers as essential equipment for the home medicine cabinet. We wanted to find out if reliable evidence is available on use of pulse oximeters to self monitor asthma exacerbations at home. We decided to include only trials that used pulse oximeters as part of a personalised asthma action plan because it is important that decisions are made on the basis of symptoms as well as oxygen saturation, and that patients have a clear protocol to follow when their asthma worsens. OBJECTIVES: To determine whether pulse oximeters used as part of a personalised asthma action plan for people with asthma are safer and more effective than a personalised asthma action plan alone. SEARCH METHODS: We searched the Cochrane Airways Group Specialised Register (CAGR), which includes reports identified through systematic searches of bibliographic databases including the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, EMBASE, the Cumulative Index to Nursing and Allied Health Literature (CINAHL), the Allied and Complementary Medicine Database (AMED) and PsycINFO, and by handsearching. We also searched ClinicalTrials.gov and the World Health Organization (WHO) trials portal. SELECTION CRITERIA: We planned to include randomised controlled trials (RCTs). Participants would have included adults, children or both with a diagnosis of asthma. We planned to include trials in which investigators compared participants who used pulse oximeters to monitor oxygen levels at home during an asthma exacerbation as part of a personalised asthma action plan (PAAP) versus those who used a PAAP without a pulse oximeter. We planned to include studies involving people receiving any treatment regimen provided that no medicine was included as part of the randomisation schedule. DATA COLLECTION AND ANALYSIS: We planned to use standard methods as recommended by The Cochrane Collaboration. MAIN RESULTS: We found no studies and no evidence to support or refute the use of home pulse oximetry in self management of asthma; therefore, we can make no recommendations about use of a pulse oximeter as part of a PAAP. AUTHORS' CONCLUSIONS: We found no reliable data to support or refute patient use of pulse oximeters to monitor oxygen saturation levels when experiencing an asthma attack. People should not use a pulse oximeter without seeking advice from a qualified healthcare professional.We identified no compelling rationale for home monitoring of oxygen levels in isolation for most people with asthma. Some people have a reduced perception of the severity of their own breathlessness when exposed to hypoxia. If trials on self monitoring of oxygen levels in the blood by pulse oximeter at home by people with asthma are conducted, the pulse oximeter must be given as part of a personalised asthma action plan.

Comparative efficacy of a self-report scale and physiological measures in dental anxiety of children.

AIM: To determine and correlate dental anxiety in children, using psychometric and physiological measures. METHODS: On hundred children (51 boys and 49 girls) were selected and anxiety was assessed using psychometric (Modified Child Dental Anxiety Scale) and physiological measures (pulse rate and oxygen saturation levels), for local anesthetic administration. Statistical analysis was carried out with SPSS software version 11.0. Metric continuous data are presented as mean ± standard deviation. Analysis between groups was carried out by using one way anova. Categorical variables were analyzed with "Fisher's exact test". For statistical significance, the probability value of < 0.05 was considered. The correlation among psychometric and physiological measures was assessed using the Spearman rank correlation. RESULTS: A very weak negative correlation between pulse rate and MCDAS(f) values was observed. The oxygen saturation level did not show significant variations and was not a reliable indicator of anxiety. CONCLUSION: Both psychometric and physiological measures have their own merits and are important clinically. Even behavioral measures, although having observer bias, can be used as an adjuvant along with these measures. It is essential to take two or more measures into consideration rather than just one to assess dental anxiety.

Chronic performance of a subcutaneous hemodynamic sensor.

BACKGROUND: A subcutaneous photoplethysmography (PPG) sensor uses light to detect changes in vascular volume from a location outside the bloodstream. Incorporation into a chronically implanted device, such as a pacemaker or an implantable cardioverter defibrillator, may facilitate therapy optimization and disease monitoring by providing continuous assessment of hemodynamic function and arterial oxygen saturation. However, performance of a chronically placed subcutaneous sensor has not been established. METHODS: Six dogs were implanted with 2-4 PPG sensors subcutaneously in the neck or posterior thorax. Half of the sensors were directed toward deep tissue and half toward overlying cutaneous tissue. Each sensor contained a red and an infrared light emitting diode, a photodetector, and supporting electronics, which were encapsulated in epoxy and attached to a transcutaneous connector. Data were collected at implant and every 3 ± 1 days for 4-9 months starting 3 weeks postimplant. At explant, the fibrous encapsulation was histologically analyzed. RESULTS: A minimally to moderately neovascularized encapsulation formed over all sensors, consisting of fibrous and granulation tissue. Higher cardiac pulse amplitudes and direct current (DC) components were recorded in sensors oriented toward deep tissue, but no significant difference between orientations was found in respiratory wave amplitude. Cardiac pulse amplitude, respiratory wave amplitude, and DC component amplitude, as recorded by the sensor, did not significantly change over time. CONCLUSIONS: Despite fibrous encapsulation of PPG sensors, cardiac pulses and respiratory waves could easily be measured throughout the study and remained constant over time. These results suggest suitability of subcutaneous PPG technology for chronic applications.

A macroporous TiO2 oxygen sensor fabricated using anodic aluminium oxide as an etching mask.

An innovative fabrication method to produce a macroporous Si surface by employing an anodic aluminium oxide (AAO) nanopore array layer as an etching template is presented. Combining AAO with a reactive ion etching (RIE) processes, a homogeneous and macroporous silicon surface can be effectively configured by modulating AAO process parameters and alumina film thickness, thus hopefully replacing conventional photolithography and electrochemical etch methods. The hybrid process integration is considered fully CMOS compatible thanks to the low-temperature AAO and CMOS processes. The gas-sensing characteristics of 50 nm TiO(2) nanofilms deposited on the macroporous surface are compared with those of conventional plain (or non-porous) nanofilms to verify reduced response noise and improved sensitivity as a result of their macroporosity. Our experimental results reveal that macroporous geometry of the TiO(2) chemoresistive gas sensor demonstrates 2-fold higher (∼33%) improved sensitivity than a non-porous sensor at different levels of oxygen exposure. In addition, the macroporous device exhibits excellent discrimination capability and significantly lessened response noise at 500 °C. Experimental results indicate that the hybrid process of such miniature and macroporous devices are compatible as well as applicable to integrated next generation bio-chemical sensors.

Clinicians' evaluations of fetal oximetry sensor placement in a multicentre randomised trial (the FOREMOST trial).

BACKGROUND: Fetal pulse oximetry (FPO) may improve the assessment of the fetal well-being in labour. Reports of health-care provider's evaluations of new technology are important in the overall evaluation of that technology. AIMS: To determine doctors' and midwives' perceptions of their experience placing FPO sensors. METHODS: We surveyed clinicians (midwives and doctors) following placement of a FPO sensor during the FOREMOST trial (multicentre randomised trial of fetal pulse oximetry). Clinicians rated ease of sensor placement (poor, fair, good and excellent). Potential influences on ease of sensor placement (staff category, prior experience in Birth Suite, prior experience in placing sensors, epidural analgesia, cervical dilatation and fetal station) were examined by ordinal regression. RESULTS: There were 281 surveys returned for the 294 sensor placement attempts (response rate 96%). Sensors were placed by midwives (29%), research midwives (48%), registrars (22%) and obstetricians (1%). The majority of clinicians had 1 or more years' Birth Suite experience, had placed six or more sensors previously, and rated ease of sensor placement as good. Advancing fetal station (P < 0.001) and the presence of epidural analgesia prior to sensor placement (P = 0.029) predicted improved ease of sensor placement. Having a clinician placing a sensor for the first time predicted a lower rating for ease of sensor placement (P = 0.001), compared to having placed one or more sensors previously. CONCLUSIONS: Clinicians with varying levels of Birth Suite experience successfully placed fetal oxygen saturation sensors, with the majority rating ease of sensor placement as good.

Detection of hypoventilation during thoracoscopy: combined cutaneous carbon dioxide tension and oximetry monitoring with a new digital sensor.

BACKGROUND: Changes in Paco(2) have not been described during thoracoscopy under sedation-assisted local anesthesia. We hypothesized that hypoventilation might occur secondary to administration of sedatives and decreased ventilation in one lung. AIM: Prospectively measure cutaneous carbon dioxide tension (Pcco(2)) in addition to pulse oximetric saturation (Spo(2)) using a new combined digital sensor to examine the occurrence of hypoventilation during thoracoscopy under sedation-assisted local anesthesia. SETTING: University hospital. METHODS: Following validation studies, Pcco(2) was prospectively measured in 16 consecutive patients undergoing thoracoscopy under sedation-assisted local anesthesia using a combined digital earlobe sensor measuring Spo(2) (percentage) and Pcco(2) (millimeters of mercury). All patients received supplemental oxygen. Routine BP monitoring and Spo(2) was continued. Patients received IV hydrocodone, 5 mg, and intermittent boluses or IV midazolam and pethidine. RESULTS: Mean baseline Pcco(2) measurement was 39.1 +/- 7.2 mm Hg (+/- SD) [range, 27.5 to 50.5 mm Hg], and peak measurement during the procedure was 52.3 +/- 10.3 mm Hg (range, 37.2 to 77 mm Hg) [p < 0.001]. Median and mean changes in Pcco(2) measurement from baseline were 13.0 mm Hg and 13.2 +/- 5.3 mm Hg (range, 5.5 to 27.8 mm Hg), respectively. Mean fall in Spo(2) during the procedure was 4.6 +/- 3.2% (range, 1 to 14%). CONCLUSIONS: Thoracoscopy performed under sedation-assisted local anesthesia is associated with significant hypoventilation. Combined measurement of Spo(2) and Pcco(2) during thoracoscopy is a novel approach in the monitoring of ventilation, enhancing patient safety, and might allow to guide the administration of sedation in a better way.

Continuous auditory monitoring--how much information do we register?

We have studied response times of 30 anaesthetists to a standardized episode of arterial oxygen desaturation in a simulated patient, randomized to the use of either a fixed or variable pitch pulse oximeter. We wished to determine if a variable auditory signal was important in detecting adverse events. A variable pitch pulse signal had a shorter time to recognition of desaturation (P < 0.0001), with a mean response time of 32 s, compared with 129 s for the fixed pitch signal.

Transcranial cerebral oximetry in the hyperbaric environment.

Continuous monitoring of dynamic changes of transcranial regional cerebral oxygenation (rSO2) was performed in 7 healthy volunteers (mean age 40.9 +/- 12.6 years; range 25-62 years) during normo- and hyperbaric oxygenation (HBO at 2.5 and at 1.95 ATA) using an INVOS 3100 cerebral oximeter. A significant change between HBO and control phase could be found in rSO2, alterations (p < 0.05; ANOVA, Tukey test). The results suggest that the calculation of rSO2 may be a useful method to monitor changes of oxygen saturation under hyperbaric conditions. However, the absolute quantification of rSO2 is useless at the moment and needs further investigation.

[Evaluating pulse oximetry in the fetus. Case control study for detection of undesirable complications]. / Evaluierung der Pulsoximetrie am Feten. Fallkontrollstudie zur Erfassung unerwünschter Komplikationen.

OBJECTIVES: Fetal pulse oximetry (PO) requires basically continuous contact of a transcervically positioned oxisensor with fetal skin. To improve signal quality adjustments of the oxisensor may be necessary. Against this background it was our intention to find out if this intrauterine device causes an increase in fetal or maternal infectious morbidity. STUDY DESIGN: We enrolled into this prospective trial 63 deliveries monitored by a blinded fetal pulse oximeter (N 400, Nellcor Inc. Pleasanton, CA) and a fetal oxisensor (FS 10; lambda = 660 + 890 nm). The control group of similar gestational age was formed by 63 chronologically following deliveries under responsibility of the same physician to reduce personal bias of obstetrical management. RESULTS: While the obstetrical risk factors (non-reassuring FHR i.e.) were significantly higher in the group with PO, gestational age, number of operative deliveries, pH of umbilical cord and Apgar score ratings did not show any significant difference. The number of post partum anaemias and local or systemic infections were identical (3 in each group). Seven neonates of the PO group had to be transferred to NICU versus 12 in the control group. The duration of antibiotic treatment, mechanical ventilation or phototherapy did not differ significantly; neither did the number of neonatal infections. CONCLUSION: In the group of fetuses monitored by fetal pulse oximetry there was no increase in fetal or maternal infectious morbidity. There was no evidence of adverse side effects which might limit the advantage of continuous oxygen saturation monitoring.

Can people hear the pitch change on a variable-pitch pulse oximeter?

The introduction of the variable-pitch feature on pulse oximeters in 1983 by the Nellcor Corporation (Hayward, CA) allowed users to rapidly detect changes in oxygen saturation by listening for changes in the pitch of the tones emitted by the pulse oximeter. A few individuals have reported that they have been unable to detect a change in pitch when oxygen saturation changes. To these individuals, the variable-pitch feature of these pulse oximeters has not been beneficial. Using the pitches from one manufacturer of oximeters, we created a computer program to simulate the pitches that accompanied various oxygen saturations. The pitches were recorded onto a tape player and played for 75 volunteer subjects unfamiliar with the pitches of a variable-pitch pulse oximeter. Of our sample, 67% were able to detect a single change in pitch corresponding to a 1% fall in oxygen saturation, and 11% of the population could not detect a change in pitch until there was a change in pitch with every beat. We suggested four alternative designs that may prove beneficial to this group of individuals.

[Pulse oximetry during fiberoptic bronchoscopy under local anesthesia]. / Pulsoximetri under fiberbronkoskopi i lokalanaestesi.

Pulse oximetry during fiberoptic bronchoscopy in local anaesthesia was performed in 81 patients (52 male, 29 female), median age 60 years (range 25-80); 18 had impaired lung function with FEV1 less than 50%. Premedication consisted of atropine, diazepam and midazolam. The arterial haemoglobin oxygenation (SaO2) was registered continuously. Supplementary oxygen in doses of 2 1/min was administered to 41 patients (group 1), while 40 patients were examined without oxygen (group 2). The two groups were comparable as regards sex, age and lung function. Mean values of SaO2 during bronchoscopy were higher in group 1 (median 96%) than in group 2 (92%) (p less than 0.001). Minimum values of SaO2 were similarly higher in group 1 (median 93%) than in group 2 (87%) (p less than 0.001). The percentage numbers of patients experiencing hypoxaemic episodes with SaO2 less than or equal to 90% and SaO2 less than or equal to 85% were 34% and 5% in group 1 compared to 80% and 35% in group 2, respectively (p less than 0.01). The decrease in SaO2 and the frequency of hypoxaemic episodes were highest in patients with impaired lung function. Supplementary oxygen in doses of 2-3 1/min and pulse oximetry are recommended as routine procedures during fiberoptic bronchoscopy in local anaesthesia.