Oximetry Tracings Research Articles

Visual Evaluation of Plethysmographic Waveforms: Introducing the Simple Systolic Ratio as an Indicator of Fluid Responsiveness.

For patient safety, maintaining hemodynamic stability during surgical procedures is critical. Dynamic indices [such as systolic pressure variation (SPV) and pulse pressure variation (PPV)], have recently seen an increase in use. Given the risks associated with such invasive techniques, there is growing interest in non-invasive monitoring methods-and plethysmographic waveform analysis. However, many such non-invasive methods involve intricate calculations or brand-specific monitors. This study introduces the simple systolic ratio (SSR), derived from pulse oximetry tracings, as a non-invasive method to assess fluid responsiveness. This prospective observational study included 25 adult patients whose SPV, PPV, and SSR values were collected at 30-min intervals during open abdominal surgery. The SSR was defined as the ratio of the tallest waveform to the shortest waveform within pulse tracings. The correlations among SSR, SPV, and PPV were analyzed. Additionally, anaesthesia specialists visually assessed pulse oximetry tracings to determine fluid responsiveness using the SSR method. Strong correlations were observed between SSR and both SPV (r = 0.715, P < 0.001) and PPV (r = 0.702, P < 0.001). Receiver operator curve analysis identified optimal SSR thresholds for predicting fluid responsiveness at 1.47 for SPV and 1.50 for PPV. A survey of anaesthesia specialists using the SSR method to visually assess fluid responsiveness produced an accuracy rate of 83%. Based on the strong correlations it exhibits with traditional markers, SSR has great potential as a clinical tool, especially in resource-limited settings. However, further research is needed to establish its role, especially as it pertains to its universal applicability across monitoring devices.

Depicting and defining sleep disturbed breathing associated with vagal nerve stimulation

BackgroundVagal nerve stimulators (VNS), which have been approved for management of refractory epilepsy and depression, induce unique disturbances of breathing during sleep (SDBVNS) that are not captured well using standard criteria. The primary purpose of this retrospective study was to compare AASM definitions with alternative criteria to more accurately measure SDBVNS We also sought to assess outcome variables that may be clinically relevant and response to positive airway pressure therapy. MethodsWe analyzed the electronic medical records and comprehensive polysomnography results of all adult subjects with active VNS for epilepsy who were referred to the sleep center for suspected sleep apnea (2015–2020). We compared standard AASM criteria for defining apneas/hypopnea index (AHIAASM) with three novel scoring criteria for hypopnea according to degree of oxygen desaturation associated with VNS events: AHIVNS0 (none required); AHIVNS2 (2% required); and AHIVNS3 (3% required). ResultsTwenty-six subjects were included in the final analysis with 35 PSGs (14 females/12 males). The mean age was 33.6 years and mean body mass index (BMI) of 32.2 kg/m2. AHIAASM measured ≥ 15/hour in 7 (26.9%) subjects versus 21 (80.8%) by AHIVNS0; 15 (70.0%) by AHIVNS2; and 5 (19.2%) by AHIVNS3. Clinically significant hypoxemia was not present. The mean time SpO2<89% was 7 (20.8) minutes. Oximetry tracings often showed a desaturation pattern that resembled a sawfish rather than sawtooth. Arousals specifically linked to VNS activation were not elevated (2.9/hour). The baseline AHIVNS0 was 27.7/hour with a lowest AHIVNS0 on PAP of 27.9/hr. ConclusionsAASM scoring criteria significantly underestimated the degree of VNS induced respiratory disturbances. VNS events were not associated with increased arousals or significant hypoxemia. PAP therapy was an ineffective treatment in this population. This study adds to the increasing body of evidence of sleep disordered breathing related to VNS and questions the clinical significance of this finding.

Sleep-disordered breathing in severe mental illness: clinical evaluation of oximetry diagnosis and management limitations.

To describe the diagnosis and management pathway of sleep-disordered breathing (SDB) in a sample of patients with severe mental illness (SMI), and to assess the feasibility and patient acceptability of overnight oximetry as a first-step screening method for detecting severe SDB in this population. The study was a retrospective audit of patients with SMI seen at a Collaborative Centre for Cardiometabolic Health in Psychosis service who were invited for overnight oximetry between November 2015 and May 2018. The adjusted oxygen desaturation index (ODI) was calculated using 4% desaturation criteria. Results were discussed with a sleep specialist and categorized into a 4-level risk probability toolfor SDB. Of 91adults consenting for overnight oximetry, 90 collected some oximetry data, though 11 of these 90 patients collected technically unsatisfactory oximetry. Thus 79/90 patients (88%) collected adequate oximetry data for at least one night. The oximetry traces suggested likely minimal obstructive sleep apnea(OSA) in 41 cases, moderate to severe OSA in 25 patients, severe OSA in 9 patients and possible obesity hypoventilation syndrome (OHS) in 4 cases. Full polysomnography was recommended for 39 patients but only one-third underwent testing. Nineteen patients were reviewed by a sleep specialist. Of the 10 patients who initiated CPAP, four were considered adherent to treatment. Home oximetry may be a pragmatic option for SDB screening in patients with SMI but reliable full diagnostic and management pathways need to be developed.

Respiratory polygraphy data of children investigated for sleep-disordered breathing with different congenital or respiratory diseases.

This short report describes respiratory indices of polygraphies (PG) performed to investigate several sleep-related disorders of breathing in children. It refers to the work of Michelet et al., Successful home respiratory polygraphy to investigate sleep-disordered breathing in children, Sleep Medicine [1]. Indications for PGs were grouped according to 6 categories: craniofacial malformation, neuromuscular disease, obesity, suspected obstructive sleep apnea (OSA), prematurity, and other. The reported data concern the initial interpretable PGs (N = 289); initial was defined as performed for the first time in any subject. Non-interpretability was defined as absent or unreliable oxygen saturation by pulse oximetry (SpO2), and/or airflow and respiratory inductance plethysmography (RIP) flow trace signals during time analyzed. Analyzed time is reported. In a subset of patients, transcutaneous carbon dioxide partial pressure (ptcCO2) was also measured. Data may be re-used for comparison in future validating research for PGs in children [2].

N95 Filtering Facepiece Respirator Use during Pregnancy: A Systematic Review.

Objective This study was aimed to systematically review the use of filtering facepiece respirators, such asN95 masks, during pregnancy. Study Design A comprehensive search for primary literature using Medline, Embase, Scopus, Web of Science, and ClinicalTrials.gov was conducted from inception until April 2020 to find articles reporting outcomes of pregnant women using filtering facepiece respirator (FFR). Studies were selected if they included the use of FFR in pregnant women and reported an outcome of interest including physiologic changes (heart rate, respiratory rate, pulse oximetry, and fetal heart rate tracing) or subjective measures (thermal or exertional discomfort or fit). The Newcastle-Ottawa Quality Assessment scale was used to assess the risk of bias. The main outcome was to describe the physiologic changes in pregnant women compared with nonpregnant women. Due to the small number of studies and heterogeneity of reported outcomes a meta-analysis was not conducted. Results of the studies were synthesized into a summary of evidence table. Results We identified four studies, three cohort studies and one crossover study, comprising 42 women using FFR during pregnancy. Risk of bias was judged to be low. Studies were consistent in showing no significant increase in maternal heart rate, respiratory rate, oxygen saturation, and fetal heart rate between pregnant and nonpregnant women using N95 FFRs for short durations. Repeat fit testing was not supported for women gaining the recommended amount of weight during pregnancy. No evidence was found to reach conclusions about prolonged N95 FFR use in pregnancy. Conclusion Limited duration N95 FFR use during pregnancy is unlikely to impart risk to the pregnant women or her fetus. Key Points Limited N95 use unlikely to impart risk to pregnant woman/fetus.Prolonged N95 use in pregnancy is unstudied.Repeat fit testing in pregnancy likely unnecessary.

Reliability of Home Nocturnal Oximetry in the Diagnosis of Overlap Syndrome in COPD

Background: Chronic obstructive pulmonary disease (COPD) and sleep apnea are common conditions and often coexist. The proper diagnosis of sleep apnea may affect the management and outcome of patients with COPD. Objective: To determine the accuracy of home nocturnal oximetry to distinguish between nocturnal oxygen desaturation related to COPD alone or to sleep apnea in patients with moderate-to-severe COPD who have significant nocturnal hypoxemia with cyclical changes in saturation. Methods: This study involved a comparison of home nocturnal oximetry and laboratory-based polysomnography (PSG) in patients with moderate-to-severe COPD considered for inclusion in a trial of nocturnal oxygen therapy. All of the patients had significant nocturnal oxygen desaturation (defined as ≥30% of the recording time with a transcutaneous arterial oxygen saturation <90%) with cyclical changes in saturation suggestive of sleep apnea. Results: PSG was obtained in 90 patients; 45 patients (mean age = 68 years, SD = 8; 71% men; mean forced expiratory volume in 1 s [FEV₁] = 50.6% predicted value, SD = 18.6%; data from 41 patients) fulfilled the criteria for sleep apnea (mean apnea-hypopnea index = 32.6 events/h, SD = 19.9) and 45 patients (mean age = 69 years, SD = 8; 87% men; mean FEV₁ predicted value 44.6%, SD = 15%) did not (mean apnea-hypopnea index = 5.5 events/h, SD = 3.8). None of the patients’ characteristics (including demographic, anthropometric, and physiologic measures) predicted the diagnosis of sleep apnea according to PSG results. Conclusion: The diagnosis of sleep apnea in patients with moderate to severe COPD cannot rely on nocturnal oximetry alone, even when typical cyclical changes in saturation are seen on oximetry tracing. When suspecting an overlap syndrome, a full-night, in-laboratory PSG should be obtained.

The McGill score as a screening test for obstructive sleep disordered breathing in children with co-morbidities

BackgroundThe McGill score is used to stratify severity of oximetry in children referred for investigation of obstructive sleep apnoea (OSA) to identify those with more severe disease and prioritize treatment. We hypothesized that its positive predictive value (PPV) and negative predictive value (NPV) in detecting OSA differs significantly between children with medical conditions and otherwise healthy children. MethodsWe performed a two-year retrospective analysis of children referred for investigation of OSA who underwent a cardiorespiratory (CR) polygraphy study. McGill score was calculated from the oximetry trace blinded to polygraphy results. We looked at two definitions of OSA: Obstructive Apnoea Hypopnoea Index (oAHI) ≥1 and ≥ 5. McGill sensitivity, specificity, PPV and NPV were calculated. McGill score = 1 was considered normal or inconclusive, >1 abnormal. ResultsWe studied 312 children, 190 males (61%), median age 4.5 (2.4–7.9) years. 129 were otherwise healthy and 183 had associated medical conditions. The PPV of the McGill score was significantly lower in children with medical conditions than otherwise healthy children. The NPV was similar in both groups of children. ConclusionsThe higher number of false positives in children with medical conditions may be due to non-obstructive causes such as central apnoeas. Children with underlying lung disease are also more likely to desaturate following a brief apnoea or hypopnoea. Children with co-morbidities who have an abnormal McGill score should not be assumed to have OSA and need more detailed sleep studies to determine the reason for the oxygen desaturations.

Successful home respiratory polygraphy to investigate sleep-disordered breathing in children

ObjectiveSleep-disordered breathing (SDB) in children is common. Interest in sleep tests, such as polygraphy (PG), which can be performed in a non-attended setting, are gaining is increasing. PG has, however, been little studied in children with co-morbidities other than obstructive sleep apnea (OSA), and in particular, if performed in a non-attended setting. We report on the feasibility and interpretability of implementing PGs at home versus in hospital. MethodsPGs were analyzed according to the setting (hospital or home) and sequence (initial or subsequent) in which they were performed. Non-interpretability was defined as absent or unreliable oxygen saturation by pulse oximetry (SpO2), or airflow and respiratory inductance plethysmography flow trace signals during the time analyzed. ResultsWe retrospectively analyzed 400 PGs; 332/400 were initial PGs. Indications were: suspected OSA (65%), obesity (13%), craniofacial malformations (5%), neuromuscular disease (4%), and other (13%) which included prematurity. 16% were recorded in hospitals and 84% at home. The mean age was 5.7 ± 5.8 years and 7.3 ± 4.5 years for the hospital and home groups, respectively. Interpretability was similar in both settings (87%). In the 68 subsequent PGs, interpretability was 84% when performed for follow-up and 96% when repeated for non-interpretability. Non-interpretability was predominantly due to a failure of the SpO2 channel. ConclusionsPG performed at home is both feasible and interpretable for a variety of indications. Non-interpretability was not predictable in association with the setting, anthropometric data, or indication, independently of the sequence (initial or subsequent PG) in which the parameters were analyzed.

Obstructive Sleep Apnea in Patients With Fibrotic Interstitial Lung Disease and COPD.

Despite the clinical and prognostic significance of obstructive sleep apnea (OSA) in chronic respiratory diseases (CRDs), there have been few studies about the possible predictors of OSA and the effect of OSA on quality of life in patients with CRDs. The objectives were to identify physiological and clinical parameters that predict the occurrence and severity of OSA and to investigate the effect of OSA on quality of life in patients with CRDs. Seventy-three patients with chronic obstructive pulmonary disease (COPD) and 77 patients with fibrotic interstitial lung disease (ILD) underwent overnight polysomnography (PSG) and pulmonary function testing and completed clinical questionnaires. The oximetry tracing was interpreted blindly with respect to the PSG results. The prevalence of OSA was 44% and 62% in COPD and ILD, respectively. The COPD assessment test item scores related to sleep quality and daily vitality were worse among patients with OSA than among patients without OSA. The STOP-BANG questionnaire (cutoff point ≥ 3) and oxygen desaturation index from the oximetry recording (oxygen desaturation index (ODI) were associated with OSA in CRDs. The STOP-BANG questionnaire with a cutoff point ≥ 3 or 6 had the highest sensitivity and specificity, respectively, in detecting OSA in CRDs. ODI had the best accuracy in identifying OSA and was independently associated with the apnea-hypopnea index in CRDs. We found OSA to be common and associated with worse sleep quality and less daily vitality in patients with advanced CRDs. The STOP-BANG questionnaire with different cutoff points may help rule in or rule out OSA. Overnight oximetry can be used as a screening tool for OSA and can assist the clinical evaluation of OSA in patients with CRDs.

A review of approaches for analysing obstructive sleep apnoea-related patterns in pulse oximetry data.

Overnight pulse oximetry allows the relatively non-invasive estimation of peripheral blood haemoglobin oxygen saturations (SpO2 ), and forms part of the typical polysomnogram (PSG) for investigation of obstructive sleep apnoea (OSA). While the raw SpO2 signal can provide detailed information about OSA-related pathophysiology, this information is typically summarized with simple statistics such as the oxygen desaturation index (ODI, number of desaturations per hour). As such, this study reviews the technical methods for quantifying OSA-related patterns in oximetry data. The technical methods described in literature can be broadly grouped into four categories: (i) Describing the detailed characteristics of desaturations events; (ii) Time series statistics; (iii) Analysis of power spectral distribution (i.e. frequency domain analysis); and (d) Non-linear analysis. These are described and illustrated with examples of oximetry traces. The utilization of these techniques is then described in two applications. First, the application of detailed oximetry analysis allows the accurate automated classification of PSG-defined OSA. Second, quantifications which better characterize the severity of desaturation events are better predictors of OSA-related epidemiological outcomes than standard clinical metrics. Finally, methodological considerations and further applications and opportunities are considered.

Use of Oximetry to Determine Need for Adenotonsillectomy for Sleep-Disordered Breathing.

Children with snoring and tonsillar hypertrophy (4-10 years old) who were candidates for T/A were randomly assigned to 2 oximetry sequences (baseline and 3-month follow-up): (1) oximetry immediately before T/A and at the 3-month follow-up, which occurred postoperatively (T/A group); or (2) oximetry at the initial visit and at the end of the usual 3-month waiting period for surgery (control group). Outcomes were (1) proportion of subjects with McGill oximetry score (MOS) >1 at baseline acquiring MOS of 1 at follow-up and (2) proportion of subjects achieving oxygen desaturation (≥3%) of hemoglobin index (ODI3) <2 episodes per hour at follow-up if they had ODI3 ≥3.5 episodes per hour at baseline. One hundred and forty children had quality oximetry tracings. Twelve of 17 (70.6%) children with MOS >1 in the T/A group and 10 of 21 (47.6%) children with MOS >1 in the control group had MOS of 1 at follow-up (P = .14). More subjects in the T/A than in the control group achieved ODI3 <2 episodes per hour at follow-up (14 of 32 [43.8%] vs 2 of 38 [5.3%]; P < .001). Three children with elevated ODI3 were treated to prevent persistently abnormal ODI3 in 1 child at follow-up. An ODI3 ≥3.5 episodes per hour in nocturnal oximetry is related to increased resolution rate of nocturnal hypoxemia after T/A for SDB compared with no intervention.

Overnight Pulse Oximetry Unwoven.

Overnight Pulse Oximetry Unwoven.

Extracting clinically relevant information from pulse oximetry traces

Cardiovascular assessment is necessary, yet unafordable for large population groups worlwide. Here we illustrate how signals obtained from standard oximeters can provide reliable estimates for transit time, a measure associated to vascular stiffness, as well as complexity measures derived from Recursive plot analysis. The salient features of our research were: 1) The possibility to use of photoplethysmographic (PPG) signals as a surrogate for transit time estimation; 2)The use of PPG signals for HRV analysis; 3)The possibility to use 2-min PPG recordings for cardiovascular estimation; 4)The proposal of a new vascular age estimator. An automated algorithm for estimating transit time from the PPG waveform yielded a strong association with age (r=0.80). All indices obtained from Recurrent Plot analysis of tachograms with PPG signals exhibited a high correlation with subject´s age. On the basis of the estimated indices a new estimator for cardiovascular age has been introduced, which exhibited a high correlation with age (r=0.97). Thus we concluded that PPG signals do retain information about cardiovascular age. This is evidenced from changes with age of different indices obtained from 2-min duration PPG traces. These result might be relevant for boosting cardiovascular diagnosis in settings with limited resources. Keywords: Pulse Oximetry, Heart Rate Variability, Transit Time Estimation, Recurrent Plot Analysis, Cardio Vascular Age.

Night-to-night variation of pulse oximetry in children with sleep-disordered breathing

BackgroundSleep-disordered breathing is a common and serious feature of many paediatric conditions and is particularly a problem in children with Down syndrome. Overnight pulse oximetry is recommended as an initial...

Safety of Yoga in Pregnancy [37

BACKGROUND: Yoga is recognized for its potential to balance an individual's mental, physical, emotional, and spiritual state. Pregnant patients often ask physicians for permission to participate in yoga. The American Congress of Obstetricians and Gynecologists has no specific recommendations for yoga. The purpose of this study was to examine the safety of yoga in pregnancy. METHODS: Institutional review board approval was obtained. Pregnant women 18–42 years old with uncomplicated pregnancies were recruited. Patients were between 35 and 37 weeks of gestation. No yoga experience was required. A nonstress test (NST) was measured at the beginning and end of the yoga session. The participants assumed 26 yoga poses. In each posture, continuous fetal monitoring, tocometry, pulse oximetry, and vital signs were obtained. All sessions were attended by a certified yoga instructor and experienced obstetrician–gynecologist. RESULTS: A total of 30 women were enrolled; five were excluded for contractions at the initial NST. Twenty-five women completed the study. All participants completed the 26 poses. There were no significant changes in vital signs during the poses. All participants had reactive NSTs before and after the session. All fetal heart tracings demonstrated accelerations and variability, and no decelerations of the fetal heart tracing were seen. No patients had regular contractions during the session. There were no falls or injuries. CONCLUSION: No safety issues were identified. Vital signs, pulse oximetry, uterine tocometry, and fetal heart tracing remained reassuring in all patients in all postures. Yoga is a safe form of physical activity that physicians can recommend to their patients with uncomplicated pregnancies.

Preoxygenation Reduces Desaturation Events and Improves Intubation Success

ObjectiveOxygen desaturation occurs frequently in the course of prehospital rapid sequence intubation (RSI) and is associated with increased morbidity and mortality. Preoxygenation with positive pressure ventilation by bag valve mask may delay the onset of desaturation. The purpose of this study was to evaluate implementation of a targeted preoxygenation protocol including the use of positive pressure ventilation on desaturation events and intubation success during air medical RSI. MethodsThe RSI air medical program airway training model was modified to target an oxygen saturation as measured by pulse oximetry value of ≥ 93% before initial laryngoscopy. A review of oxygen saturation as measured by pulse oximetry tracings was performed for 2 years before and 2 years after implementation of this protocol. The incidence of desaturation events and overall intubation success rates were compared before and after the intervention. ResultsOne hundred fifty-five RSI procedures were evaluated over the study period. Desaturation events decreased from 58% in the 2 years before algorithm changes to 28% in the first year and 14% in the second year after implementation (P < .01). Intubation success rates increased from 89% to 98% (P < .01). There were no self-reports of aspiration events during the study period. ConclusionA preoxygenation protocol dramatically reduced the incidence of desaturation events and increased intubation success without an increase in the number of reported aspiration events.

Examination of Pulse Oximetry Tracings to Detect Obstructive Sleep Apnea in Patients with Advanced Chronic Obstructive Pulmonary Disease

Nocturnal hypoxemia and obstructive sleep apnea (OSA) are common comorbidities in patients with chronic obstructive pulmonary disease (COPD). The authors sought to develop a strategy to interpret nocturnal pulse oximetry and assess its capacity for detection of OSA in patients with stage 3 to stage 4 COPD. A review of consecutive patients with COPD who were clinically prescribed oximetry and polysomnography was conducted. OSA was diagnosed if the polysomnographic apnea-hypopnea index was >15 events⁄h. Comprehensive criteria were developed for interpretation of pulse oximetry tracings through iterative validation and interscorer concordance of ≥80%. Criteria consisted of visually identified desaturation 'events' (sustained desaturation ≥4%, 1 h time scale), 'patterns' (≥3 similar desaturation⁄saturation cycles, 15 min time scale) and the automated oxygen desaturation index. The area under the curve (AUC), sensitivity, specificity and accuracy were calculated. Of 59 patients (27 male), 31 had OSA (53%). The mean forced expiratory volume in 1 s was 46% of predicted (range 21% to 74% of predicted) and 52% of patients were on long-term oxygen therapy. Among 59 patients, 35 were correctly identified as having OSA or not having OSA, corresponding to an accuracy of 59%, with a sensitivity and specificity of 59% and 60%, respectively. The AUC was 0.57 (95% CI 0.55 to 0.59). Using software-computed desaturation events (hypoxemia ≥4% for ≥10 s) indexed at ≥15 events⁄h of sleep as diagnostic criteria, sensitivity was 60%, specificity was 63% and the AUC was 0.64 (95%CI 0.62 to 0.66). No single criterion demonstrated important diagnostic utility. Pulse oximetry tracing interpretation had a modest diagnostic value in identifying OSA in patients with moderate to severe COPD.

Survey of the Clinical Assessment and Utility of Near-Infrared Cerebral Oximetry in Cardiac Surgery

Near-infrared cerebral oximetry increasingly is used for monitoring during cardiac surgery. Nonetheless, the scientific basis for incorporating this technology into clinical practice, the indications for when to do so, and standard diagnostic and treatment algorithms for defining abnormal values are yet to be rigorously defined. The authors hypothesized that there would be (1) variation in clinical use and practices for near-infrared spectroscopy (NIRS), and (2) variation in management of patients when clinicians are provided with NIRS information. In order to test this hypothesis, they sought to assess the nature and strength of response heterogeneity among anesthesiologists and cardiac perfusionists when provided with cardiac surgery patient scenarios and cerebral oximetry data. A prospectively collected survey. A hospital-based, multi-institutional, multinational study. By e-mail, the authors surveyed the membership of the Society of Cardiovascular Anesthesiologists and the online Cardiovascular Perfusion Forum. This survey was focused on ascertaining what actions clinicians would take in each scenario, given case information and cerebral oximetry tracings. Questions were based on 11 patient scenarios selected to represent small, large, symmetric, or asymmetric decreases in measured regional cerebral oxygen saturation (rScO2) encountered during cardiac surgery. Information on the respondents' (n = 796; 73% anesthesiologists) clinical practice, demography, and cerebral oximetry utilization was collected. An index of dispersion was used to assess response heterogeneity overall and within demographic subgroups. The majority of respondents indicated that cerebral oximetry monitoring was either useful or an essential monitor, especially perfusionists and clinicians who used cerebral oximetry most frequently. There were marked differences in responses between perfusionists and anesthesiologists for 4 of the 6 scenarios (p<0.005 for each of these 4 scenarios) occurring during cardiopulmonary bypass. Scenarios having greatest rScO2 reduction or asymmetry in rScO2 were associated with the highest dispersion, indicating least agreement in management. Scenarios with mild or moderate rScO2 reduction were associated with the lowest dispersion, indicating greater agreement in management. Although experimental data gradually are accumulating to support the role for cerebral oximetry monitoring during cardiac surgery, the results of the present survey support the view that its role remains poorly defined, and consensus for its appropriate use is lacking. Importantly, the authors observed marked variation in the use, perceived utility, and management of patients for 4 of the 6 CPB scenarios between perfusionists and anesthesiologists who share the management of CPB. These findings support the need for well-designed, adequately-powered clinical trials examining the value of this technology.

CPAP for Obstructive Sleep Apnea in the Post-Operative Setting: An Oximetry Evaluation Study

Objective: To study the prevalence and associations of nocturnal hypoxia following surgery in PAP-treated (CPAP or bilevel pressure support) OSA patients. Patients and Methods: PAP-treated OSA patients presenting for elective surgery (n=38) between August 2007 and October 2008 underwent overnight oximetry monitoring on their prescribed PAP therapy on postoperative night one. The lowest oxygen (O2) saturation (SpO2), time spent with SpO2 <89% and the presence of sleep disordered breathing (saw-tooth oscillations) were determined from the oximetry tracings. Need for supplemental O2, nursing/ respiratory interventions, and complications were recorded. Records were reviewed for the type and duration of surgery and anesthesia, net fluid balance, narcotic / sedative use, demographics and co-morbidities. Results: Seven of 38 subjects (18.4%) spent at least 30 minutes with SpO2 <90% during the night (hypoxic group=HG) on their prescribed PAP therapy. The severity of baseline OSA (total and supine apnea-hypopnea index), pre-CPAP SpO2 (asleep on diagnostic PSG and awake evening after surgery), net fluid balance, and total IV narcotic dose were associated with the HG. Nursing interventions and addition of O2 were more common in the HG, though other adverse events were not. Review of the oximetry tracings suggested 71% of the HG, and 42% of the non-hypoxic group, had findings of uncontrolled sleep apnea. Conclusions: Despite the use of prescribed PAP therapy the night following surgery, some OSA patients become hypoxic. Postoperative oximetry monitoring may be indicated in PAP-treated OSA patients undergoing surgery

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Introduction: Electronic surveillance in the intensive care unit have improved processes of care including early weaning, limiting ventilator induced injury etc. However, it has not been used for oxygen (FiO2) titration in adults, where exposure to high FiO2 levels can be seen due to varied titration practices. Hypothesis: An electronic surveillance system with a decision support tool for respiratory therapists can be implemented to detect hyperoxia and is safe for FiO2 titration. Methods: Electronic alerts were generated by a “Sniffer”, a real-time in-house developed smart automation alert system for Mayo ICUs (MN), which continually sniffs and executes hyperoxia criteria against patients’ records on an electronic database. A hyperoxic event was determined arbitrarily as Fio2>50% when the corresponding saturation (SpO2) was = >95% for at least 30 minutes after 60 minutes from intubation. Any alerts outside the above parameters were invalid. A decision support tool was created for FiO2 titration. Review of electronic medical records for hyperoxic events by an independent observer were considered as gold standard. Monitoring was done for a-24 hour period at a time, until extubation. FiO2 was noted before each alert and after each titration to monitor for desaturation. Results: 151 alerts were received for 38 patients over median mechanical ventilation time of 2 days (IQR, 0.61-6.2). Among them,106 were considered appropriate, while 45 were considered invalid (PPV 0.70). 55 events of hyperoxia were missed (sensitivity 0.66, specificity 0.98). Therapists responded to the alerts by FiO2 titration 73 times (69% of alerts). Desaturation (SpO2 < 88%) within an hour of titration without adverse events occurred two times(0.02%). Reasons for not responding to alerts were, procedural (5); poor oximetry tracing (1); physician discretion (2); low arterial oxygen (2); immediate extubation (1); concern for hypoxia (3) and unknown (19). Most common reasons for invalid alerts were change in frequency of electronic data and representation of non-invasive as invasive mechanical ventilation. Conclusions: An electronic alert system with a decision support tool to detect hyperoxia is feasible, safe and has good positive predictive value.