Long-Term Oxygen Therapy for 24 or 15 Hours per Day in Severe Hypoxemia.

BACKGROUND: Long-term oxygen supplementation for at least 15 hours per day prolongs survival among patients with severe hypoxemia. On the basis of a nonrandomized comparison, long-term oxygen therapy has been recommended to be used for 24 hours per day, a more burdensome regimen. METHODS: To test the hypothesis that long-term oxygen therapy used for 24 hours per day does not result in a lower risk of hospitalization or death at 1 year than therapy for 15 hours per day, we conducted a multicenter, registry-based, randomized, controlled trial involving patients who were starting oxygen therapy for chronic, severe hypoxemia at rest. The patients were randomly assigned to receive long-term oxygen therapy for 24 or 15 hours per day. The primary outcome, assessed in a time-to-event analysis, was a composite of hospitalization or death from any cause within 1 year. Secondary outcomes included the individual components of the primary outcome assessed at 3 and 12 months. RESULTS: Between May 18, 2018, and April 4, 2022, a total of 241 patients were randomly assigned to receive long-term oxygen therapy for 24 hours per day (117 patients) or 15 hours per day (124 patients). No patient was lost to follow-up. At 12 months, the median patient-reported daily duration of oxygen therapy was 24.0 hours (interquartile range, 21.0 to 24.0) in the 24-hour group and 15.0 hours (interquartile range, 15.0 to 16.0) in the 15-hour group. The risk of hospitalization or death within 1 year in the 24-hour group was not lower than that in the 15-hour group (mean rate, 124.7 and 124.5 events per 100 person-years, respectively; hazard ratio, 0.99; 95% confidence interval [CI], 0.72 to 1.36; 90% CI, 0.76 to 1.29; P = 0.007 for nonsuperiority). The groups did not differ substantially in the incidence of hospitalization for any cause, death from any cause, or adverse events. CONCLUSIONS: Among patients with severe hypoxemia, long-term oxygen therapy used for 24 hours per day did not result in a lower risk of hospitalization or death within 1 year than therapy for 15 hours per day. (Funded by the Crafoord Foundation and others; REDOX ClinicalTrials.gov number, NCT03441204.).

Hemoglobin J-Auckland: a clinically silent low oxygen affinity variant presenting with persistent asymptomatic hypoxemia at high altitude.

BACKGROUND: Inherited hemoglobin disorders are common in clinical practice. While qualitative (i.e. sickle cell disease) and quantitative (thalassemia) hemoglobinopathies are usually diagnosed clinically and confirmed through simple laboratory assessments, hemoglobin variants with altered oxygen affinity often go undetected due to their typically silent clinical presentation. Hemoglobin (Hb) J-Auckland, a low oxygen affinity hemoglobin variant first described in 1987 in Auckland, New Zealand, is one such silent disorder. CASE PRESENTATION: We report for the first time a clinically evident case of previously undiagnosed Hb J-Auckland in an 8-year-old girl who presented with unexplained hypoxemia at high altitude. Her oxygen level was corrected with supplemental oxygen and when assessed at low altitude. A brief discussion of the diagnostic approach and clinical implications is provided. CONCLUSION: Standard hemoglobin analysis is essential for the evaluation of suspected altered affinity hemoglobinopathy, and genetic testing is often required for definitive diagnosis. Early recognition and diagnosis of these variants can prevent mismanagement and improve patient outcomes.

The impact of hindsight bias on the diagnosis of perioperative events by anesthesia providers: A multicenter randomized crossover study.

STUDY OBJECTIVE: Hindsight bias is the tendency to overestimate the predictability of an event after it has already occurred. We aimed to evaluate whether hindsight bias influences the retrospective interpretation of clinical scenarios in the field of anesthesiology, which relies on clinicians making rapid decisions in the setting of perioperative adverse events. DESIGN: Two clinical scenarios were developed (intraoperative hypotension and intraoperative hypoxia) with 3 potential diagnoses for each. Participants completed a crossover study reviewing one case without being informed of the supposed ultimate diagnosis (i.e., no 'anchor' diagnosis), referred to as their foresight case, and the other as a hindsight case wherein they were informed in the leading sentence of the scenario that 1 of the 3 conditions provided was the ultimate diagnosis (i.e., the diagnosis the participant might 'anchor' to if given this information at the start). Participants were randomly assigned to (1) which scenario (hypotension or hypoxia) was presented as the initial foresight case and (2) which of the 3 potential diagnoses for the second case (the hindsight case, which defaulted to whichever case the participant was not assigned for the first case) was presented as the ultimate diagnosis in the leading sentence in a 2 (scenario order) x 3 (hindsight case anchor) between-subjects factorial design (6 possible randomization assignments). SETTING: Two academic medical centers. PARTICIPANTS: Faculty, fellow, and resident anesthesiologists and certified nurse anesthetists (CRNAs). INTERVENTIONS: None. MEASUREMENTS: After reading each clinical scenario, participants were asked to rate the probability (%) of each of three potential diagnoses to have caused the hypotension or hypoxia. Compositional data analysis (CoDA) was used to compare whether diagnosis probabilities differ between the hindsight and the foresight case. MAIN RESULTS: 113 participants completed the study. 59 participants (52%) were resident anesthesiologists. Participants randomized to the hypotension scenario as a hindsight case were 2.82 times more likely to assign higher probability to the pulmonary embolus diagnosis if provided as an anchor (95% CI, 1.35-5.90; P = 0.006) and twice as likely to assign higher probability to the myocardial infarction diagnosis if provided as an anchor (95% CI, 1.12-3.58; P = 0.020). Participants randomized to the hypoxia scenario as a hindsight case were 1.78 times more likely to assign higher probability to the mainstem bronchus intubation diagnosis if provided in the anchor statement (95% CI, 1.00-3.14; P = 0.048) and 3.72 times more likely to assign higher probability to the pulmonary edema diagnosis if provided as an anchor (95% CI, 1.88-7.35; P < 0.001). CONCLUSIONS: Hindsight bias influences the clinical diagnosis probabilities assigned by anesthesia providers. Clinicians should be educated on hindsight bias in perioperative medicine and be cognizant of the effect of hindsight bias when interpreting clinical outcomes.

Pulse oximetry in patients with pigmented skin: What I should know.

Pulse oximetry is widely used to non-invasively estimate the oxygen saturation of haemoglobin in arterial blood (SpO2). It is used widely throughout healthcare and was used extensively during the Covid-19 pandemic to detect and treat hypoxic patients. Research has suggested that pulse oximetry is less accurate in patients with darker skin. This led the US Food and Drug Administration agency (FDA) to issue a safety statement warning that pulse oximeters may be inaccurate when patients have pigmented skin. Evidence suggests that the oxygen saturation of arterial blood (SaO2) may be being overestimated by measuring SpO2 in those with pigmented skin. The degree of overestimation increases as SaO2 decreases especially when SpO2 reads below 80%. We review how pulse oximetry works and consider the implications for a patient's health when interpreting SpO2 in individuals with pigmented skin.

Effect of noninvasive ventilation on mortality and clinical outcomes among patients with severe hypoxemic COVID-19 pneumonia after high-flow nasal oxygen failure: a multicenter retrospective French cohort with propensity score analysis.

BACKGROUND: We assessed the effect of noninvasive ventilation (NIV) on mortality and length of stay after high flow nasal oxygenation (HFNO) failure among patients with severe hypoxemic COVID-19 pneumonia. METHODS: In this multicenter, retrospective study, we enrolled COVID-19 patients admitted in intensive care unit (ICU) for severe COVID-19 pneumonia with a HFNO failure from December 2020 to January 2022. The primary outcome was to compare the 90-day mortality between patients who required a straight intubation after HFNO failure and patients who received NIV after HFNO failure. Secondary outcomes included ICU and hospital length of stay. A propensity score analysis was performed to control for confounding factors between groups. Exploratory outcomes included a subgroup analysis for 90-day mortality. RESULTS: We included 461 patients with HFNO failure in the analysis, 233 patients in the straight intubation group and 228 in the NIV group. The 90-day mortality did not significantly differ between groups, 58/228 (25.4%) int the NIV group compared with 59/233 (25.3%) in the straight intubation group, with an adjusted hazard ratio (HR) after propensity score weighting of 0.82 [95%CI, 0.50-1.35] (p = 0.434). ICU length of stay was significantly shorter in the NIV group compared to the straight intubation group, 10.0 days [IQR, 7.0-19.8] versus 18.0 days [IQR,11.0-31.0] with a propensity score weighted HR of 1.77 [95%CI, 1.29-2.43] (p < 0.001). A subgroup analysis showed a significant increase in mortality rate for intubated patients in the NIV group with 56/122 (45.9%), compared to 59/233 (25.3%) for patients in the straight intubation group (p < 0.001). CONCLUSIONS: In severely hypoxemic COVID-19 patients, no significant differences were observed on 90-day mortality between patients receiving straight intubation and those receiving NIV after HFNO failure. NIV strategy was associated with a significant reduction in ICU length of stay, despite an increase in mortality in the subgroup of patients finally intubated.

Arterial blood gas analysis or venous blood gas analysis for adult hospitalised patients with respiratory presentations: a systematic review.

BACKGROUND: Identification of hypoxaemia and hypercapnia is essential for the diagnosis and treatment of acute respiratory failure. While arterial blood gas (ABG) analysis is standard for PO2 and PCO2 measurement, venous blood gas (VBG) analysis is increasingly used as an alternative. Previous systematic reviews established that VBG reporting of PO2 and PCO2 is less accurate, but the impacts on clinical management and patient outcomes are unknown. AIMS: This study aimed to systematically review available evidence of the clinical impacts of using ABGs or VBGs and examine the arteriovenous difference in blood gas parameters. METHODS: A comprehensive search of the MEDLINE, Embase and Cochrane Library databases since inception was conducted. Included studies were prospective or cross-sectional studies comparing peripheral ABG to peripheral VBG in adult non-critical care inpatients presenting with respiratory symptoms. RESULTS: Of 15 119 articles screened, 15 were included. No studies were found that examined clinical impacts resulting from using VBG compared to ABG. Included studies focused on the agreement between ABG and VBG measurements of pH, PO2, PCO2 and HCO3 -. Due to the heterogeneity of the included studies, qualitative evidence synthesis was performed. While the arteriovenous difference in pH and HCO3 - was generally predictable, the difference in PO2 and PCO2 was more significant and less predictable. CONCLUSIONS: Our study reinforces the notion that VBG is not comparable to ABG for physiological measurements. However, a key revelation from our research is the significant lack of data regarding the clinical implications of using VBG instead of ABG, a common scenario in clinical practice. This highlights a critical knowledge gap.

Hypoxaemia and risk of death among children: rethinking oxygen saturation, risk-stratification, and the role of pulse oximetry in primary care.

Pulse oximeters are essential for assessing blood oxygen levels in emergency departments, operating theatres, and hospital wards. However, although the role of pulse oximeters in detecting hypoxaemia and guiding oxygen therapy is widely recognised, their role in primary care settings is less clear. In this Viewpoint, we argue that pulse oximeters have a crucial role in risk-stratification in both hospital and primary care or outpatient settings. Our reanalysis of hospital and primary care data from diverse low-income and middle-income settings shows elevated risk of death for children with moderate hypoxaemia (ie, peripheral oxygen saturations [SpO2] 90-93%) and severe hypoxaemia (ie, SpO2 <90%). We suggest that moderate hypoxaemia in the primary care setting should prompt careful clinical re-assessment, consideration of referral, and close follow-up. We provide practical guidance to better support front-line health-care workers to use pulse oximetry, including rethinking traditional binary SpO2 thresholds and promoting a more nuanced approach to identification and emergency treatment of the severely ill child.

Extended Pulse Oximetry Screening in Healthy Neonates.

Predischarge pulse oximetry screening (POS) is recommended to pick up critical congenital heart diseases in apparently well neonates. However, it is possible that cases may be missed during the early POS in the presence of delayed closure of the ductus arteriosus. Repeat POS in the second week of life was found to be helpful and feasible for early detection of pathological states causing hypoxemia in seemingly well neonates. Studies with larger sample size are recommended to establish the role of an additional POS in the second week for enhanced CCHD detection.

Nocturnal hypoxemic burden and micro- and macrovascular disease in patients with type 2 diabetes.

BACKGROUND: Micro- and macrovascular diseases are common in patients with type 2 diabetes mellitus (T2D) and may be partly caused by nocturnal hypoxemia. The study aimed to characterize the composition of nocturnal hypoxemic burden and to assess its association with micro- and macrovascular disease in patients with T2D. METHODS: This cross-sectional analysis includes overnight oximetry from 1247 patients with T2D enrolled in the DIACORE (DIAbetes COhoRtE) study. Night-time spent below a peripheral oxygen saturation of 90% (T90) as well as T90 associated with non-specific drifts in oxygen saturation (T90non - specific), T90 associated with acute oxygen desaturation (T90desaturation) and desaturation depths were assessed. Binary logistic regression analyses adjusted for known risk factors (age, sex, smoking status, waist-hip ratio, duration of T2D, HbA1c, pulse pressure, low-density lipoprotein, use of statins, and use of renin-angiotensin-aldosterone system inhibitors) were used to assess the associations of such parameters of hypoxemic burden with chronic kidney disease (CKD) as a manifestation of microvascular disease and a composite of cardiovascular diseases (CVD) reflecting macrovascular disease. RESULTS: Patients with long T90 were significantly more often affected by CKD and CVD than patients with a lower hypoxemic burden (CKD 38% vs. 28%, p < 0.001; CVD 30% vs. 21%, p < 0.001). Continuous T90desaturation and desaturation depth were associated with CKD (adjusted OR 1.01 per unit, 95% CI [1.00; 1.01], p = 0.008 and OR 1.30, 95% CI [1.06; 1.61], p = 0.013, respectively) independently of other known risk factors for CKD. For CVD there was a thresholdeffect, and only severly and very severly increased T90non-specific was associated with CVD ([Q3;Q4] versus [Q1;Q2], adjusted OR 1.51, 95% CI [1.12; 2.05], p = 0.008) independently of other known risk factors for CVD. CONCLUSION: While hypoxemic burden due to oxygen desaturations and the magnitude of desaturation depth were significantly associated with CKD, only severe hypoxemic burden due to non-specific drifts was associated with CVD. Specific types of hypoxemic burden may be related to micro- and macrovascular disease.

Pulse Oximetry: 2023 Year in Review.

Pulse oximetry is arguably the most impactful monitor ever introduced into respiratory care practice. Recently there has been increased attention to the problem of occult hypoxemia in which patients are hypoxemic despite an acceptable SpO2 Although occult hypoxemia might be greater in Black patients than white patients, it is not insignificant in whites. In a given population of patients, the bias between SpO2 and arterial oxygen saturation (SaO2 ) might be close to zero. However, the limits of agreement can be wide, meaning that SpO2 might overestimate SaO2 in many individual patients, which can result in occult hypoxemia in some. Manufactures report accuracy of SpO2 derived from normal individuals, which might differ from that in the clinical setting. That SpO2 overestimates SaO2 in an important number of individuals has caused some to recommend higher SpO2 targets to avoid occult hypoxemia. There is also evidence that suggests that SpO2 might not accurately trend SaO2 Additional research is needed to investigate strategies to mitigate the bias between SpO2 and SaO2 Clinicians must be cognizant of the limitations of pulse oximetry when clinically using SpO2 The aim of this paper is to provide an update on pulse oximetry.

Value of integrated pulmonary index monitoring for the detection of adverse respiratory events in patients undergoing sedation for gastrointestinal system endoscopy.

Objectives: To determine if the integrated pulmonary index detects changes in ventilation status early in patients undergoing gastrointestinal endoscopy under sedation, and to determine the risk factors affecting hypoxia. METHODS: The retrospective study was conducted at the endoscopy unit of a tertiary university hospital in Turkey and comprised data between October 2018 and December 2019 related to patients of either gender aged >18 years who were assessed as American Society of Anaesthesiologists grade I-III and underwent elective lower and upper gastrointestinal endoscopy. Monitoring was done with capnography in addition to standard procedures. Data was analysed using SPSS 23. RESULTS: Of the 154 patients, 94(%) were females and 60(%) were males. The overall mean age was 50.88±11.8 years (range: 20-70 years). Mean time under anaesthesia was 23.58±4.91 minutes and mean endoscopy time was 21.73±5.06 minutes. During the procedure, hypoxia was observed in 42(27.3%) patients, severe hypoxia in 23(14.9%) and apnoea in 70(45.5%). Mean time between apnoea and hypoxia was 12.59±7.99 seconds, between apnoea and serious hypoxia 21.07±17.64 seconds, between integrated pulmonary index score 1 and hypoxia 12.91±8.17 sec, between integrated pulmonary index score 1 and serious hypoxia 21.59±14.13 seconds, between integrated pulmonary index score <7 and hypoxia 19.63±8.89 seconds, between integrated pulmonary index score <7 and serious hypoxia 28.39±12.66 seconds, between end-tidal carbon dioxide and hypoxia 12.95±8.33 seconds, and between end-tidal carbon dioxide and serious hypoxia 21.29±7.55 seconds. With integrated pulmonary index score 1, sensitivity value for predicting hypoxia and severe hypoxia was 88.1% and 95.7%, respectively, and specificity was 67% and 60.3%, respectively. With integrated pulmonary index score <7, the corresponding values were 100%, 100%, 42% and 64.1%, respectively. CONCLUSIONS: Capnographic monitoring, especially the follow-up integrated pulmonary index score, was found to be valuable and reliable in terms of finding both time and accuracy of the risk factor in the diagnosis of respiratory events.

Assessing hypoxic respiratory failure in mechanically ventilated neonates: A comparative study of oxygen saturation index and oxygenation index.

OBJECTIVE: To investigate the correlation between oxygen saturation index (OSI) and oxygenation index (OI) for evaluating the blood oxygenation status in neonates with respiratory failure requiring mechanical ventilation support and to assess the predictive capability of OSI in determining clinically relevant OI cutoffs. METHODS: A prospective study was conducted on neonates who received invasive mechanical ventilation at the neonatal intensive care unit of tertiary hospital in Vietnam. Bland-Altman analysis was utilized to evaluate the agreement between OSI and OI. RESULTS: A total of 123 neonates, including both term and preterm infants, were included in the study. A high agreement rate of 94.3% within the 95% limits of agreement (between OI and OSI), with a narrow similarity value of 3.3 (95% CI: -5.1 to 11.8) and high correlation coefficient (r = 0.791, p<0.001) was observed. The OSI cut-off value for predicting an OI of >15 was determined to be 7.45, with a sensitivity of 100% and a specificity of 87.4% (AUC 0.955; 95% CI: 0.922-0.989, p < 0.05). Similarly, an OSI cutoff value of 9.9 corresponded to an OI of 25, displaying a sensitivity of 100% and specificity of 87.4% (AUC 0.92). The receiver operating characteristic (ROC) curves for OSI exhibited statistically significant results (p < 0.05). CONCLUSION: The findings demonstrate a strong correlation between OSI and OI in neonates with respiratory failure. Furthermore, OSI, as a non-invasive method, can serve as a substitute for OI to evaluate the severity of hypoxic respiratory failure and lung injury in neonates.

Pulse oximetry signal loss during hypoxic episodes in preterm infants receiving automated oxygen control.

The aim of this study was to analyze signal loss (SL) resulting from low signal quality of pulse oximetry-derived hemoglobin oxygen saturation (SpO2) measurements during prolonged hypoxemic episodes (pHE) in very preterm infants receiving automatic oxygen control (AOC). We did a post hoc analysis of a randomized crossover study of AOC, programmed to set FiO2 to "back-up FiO2" during SL. In 24 preterm infants (median (interquartile range)) gestational age 25.3 (24.6 to 25.6) weeks, recording time 12.7 h (12.2 to 13.6 h) per infant, we identified 76 pHEs (median duration 119 s (86 to 180 s)). In 50 (66%) pHEs, SL occurred for a median duration of 51 s (33 to 85 s) and at a median frequency of 2 (1 to 2) SL-periods per pHE. SpO2 before and after SL was similar (82% (76 to 88%) vs 82% (76 to 87%), p = 0.3)).  Conclusion: SL is common during pHE and must hence be considered in AOC-algorithm designs. Administering a "backup FiO2" (which reflects FiO2-requirements during normoxemia) during SL may prolong pHE with SL.  Trial registration: The study was registered at www. CLINICALTRIALS: gov under the registration no. NCT03785899. WHAT IS KNOWN: • Previous studies examined SpO2 signal loss (SL) during routine manual oxygen control being rare, but pronounced in lower SpO2 states. • Oxygen titration during SL is unlikely to be beneficial as SpO2 may recover to a normoxic range. WHAT IS NEW: • Periods of low signal quality of SpO2 are common during pHEs and while supported with automated oxygen control (SPOC), FiO2 is set to a back-up value reflecting FiO2 requirements during normoxemia in response to SL, although SpO2 remained below target until signal recovery. • FiO2 overshoots following pHEs were rare during AOC and occurred with a delayed onset; therefore, increased FiO2 during SL does not necessarily lead to overshoots.

Predicting Extubation Readiness in Preterm Infants Utilizing Machine Learning: A Diagnostic Utility Study.

OBJECTIVE: The objective of this study was to predict extubation readiness in preterm infants using machine learning analysis of bedside pulse oximeter and ventilator data. STUDY DESIGN: This is an observational study with prospective recordings of oxygen saturation (SpO2) and ventilator data from infants <30 weeks of gestation age. Research pulse oximeters collected SpO2 (1 Hz sampling rate) to quantify intermittent hypoxemia (IH). Continuous ventilator metrics were collected (4-5-minute sampling) from bedside ventilators. Data modeling was completed using unbiased machine learning algorithms. Three model sets were created using the following data source combinations: (1) IH and ventilator (IH + SIMV), (2) IH, and (3) ventilator (SIMV). Infants were also analyzed separated by postnatal age (infants <2 or ≥2 weeks of age). Models were compared by area under the receiver operating characteristic curve (AUC). RESULTS: A total of 110 extubation events from 110 preterm infants were analyzed. Infants had a median gestation age and birth weight of 26 weeks and 825 g, respectively. Of the 3 models presented, the IH + SIMV model achieved the highest AUC of 0.77 for all infants. Separating infants by postnatal age increased accuracy further achieving AUC of 0.94 for <2 weeks of age group and AUC of 0.83 for ≥2 weeks group. CONCLUSIONS: Machine learning analysis has the potential to enhance prediction accuracy of extubation readiness in preterm infants while utilizing readily available data streams from bedside pulse oximeters and ventilators.

Does nurse use of a standardized flowsheet to document communication with advanced providers provide a mechanism to detect pulse oximetry failures? A retrospective study of electronic health record data.

BACKGROUND: Pulse oximetry guides clinical decisions, yet does not uniformly identify hypoxemia. We hypothesized that nursing documentation of notifying providers, facilitated by a standardized flowsheet for documenting communication to providers (physicians, nurse practitioners, and physician assistants), may increase when hypoxemia is present, but undetected by the pulse oximeter, in events termed "occult hypoxemia." OBJECTIVE: To compare nurse documentation of provider notification in the 4 h preceding cases of occult hypoxemia, normal oxygenation, and evident hypoxemia confirmed by an arterial blood gas reading. METHODS: We conducted a retrospective study using electronic health record data from patients with COVID-19 at five hospitals in a healthcare system with paired SpO2 and SaO2 readings (measurements within 10 min of oxygen saturation levels in arterial blood, SaO2, and by pulse oximetry, SpO2). We applied multivariate logistic regression to assess if having any nursing documentation of provider notification in the 4 h prior to a paired reading confirming occult hypoxemia was more likely compared to a paired reading confirming normal oxygen status, adjusting for characteristics significantly associated with nursing documentation. We applied conditional logistic regression to assess if having any nursing documentation of provider notification was more likely in the 4-hour window preceding a paired reading compared to the 4-hour window 24 h earlier separately for occult hypoxemia, visible hypoxemia, and normal oxygenation. RESULTS: There were data from 1910 patients hospitalized with COVID-19 who had 44,972 paired readings and an average of 26.5 (34.5) nursing documentation of provider notification events. The mean age was 63.4 (16.2). Almost half (866/1910, 45.3 %) were White, 701 (36.7 %) were Black, and 239 (12.5 %) were Hispanic. Having any nursing documentation of provider notification was 46 % more common in the 4 h before an occult hypoxemia paired reading compared to a normal oxygen status paired reading (OR 1.46, 95 % CI: 1.28-1.67). Comparing the 4 h immediately before the reading to the 4 h one day preceding the paired reading, there was a higher likelihood of having any nursing documentation of provider notification for both evident (OR 1.45, 95 % CI 1.24-1.68) and occult paired readings (OR 1.26, 95 % CI 1.04-1.53). CONCLUSION: This study finds that nursing documentation of provider notification significantly increases prior to confirmed occult hypoxemia, which has potential in proactively identifying occult hypoxemia and other clinical issues. There is potential value to encouraging standardized documentation of nurse concern, including communication to providers, to facilitate its inclusion in clinical decision-making.

The paradox of platypnoea-orthodeoxia syndrome.

Platypnoea-orthodeoxia is a rare clinical syndrome characterised by dyspnoea and oxygen desaturation in the upright position which improves when supine. It requires two components: a sufficiently sized anatomical vascular defect (typically intra-cardiac or intra-pulmonary) combined with a functional component that promotes positional right-to-left shunting. We describe the rare occurrence of a patient with platypnoea-orthodeoxia syndrome (POS) because of a paradoxical shunt through a patent foramen ovale caused by a large right atrial line-associated thrombus in a male with metastatic oesophageal cancer undergoing chemotherapy. This case is a timely reminder to consider POS amongst differentials for hypoxia as it is often treatable if recognised.