Pressure Control Surrogate Formula for Estimating Mechanical Power in ARDS is Associated with Mortality.

BACKGROUND: Mechanical power applied to the respiratory system (MPRS) is associated with ventilator-induced lung injury (VILI) and ARDS mortality. Absent automated ventilator MPRS measurements, the alternative is clinically unwieldy equations. However, simplified surrogate formulas are now available and accurately reflect values produced by airway pressure-volume curves. This retrospective, observational study examined whether the surrogate pressure-control equation alone could accurately assess mortality risk in ARDS subjects managed almost exclusively with volume-control ventilation.METHODS: 948 subjects were studied in whom invasive mechanical ventilation and implementation of ARDSNet ventilator protocols commenced ≤ 24hr after ARDS onset, and who survived > 24hr. MPRS was calculated as 0.098 x respiratory frequency x VT x (PEEP + driving pressure [PDR]). MPRS was assessed as a risk factor for hospital mortality, and compared between non-survivors and survivors across Berlin Definition classifications. In addition, mortality was compared across 4 MPRS thresholds associated with VILI or mortality (ie. 15, 20, 25 and 30 J/m).RESULTS: MPRS was associated with increased mortality risk: Odds Ratio (95% CI) of 1.06 (1.04-1.07) per J/m, P<0.001). Median MPRS differentiated non-survivors from survivors in Mild (24.7 vs. 18.5 J/m, respectively, P==0.034); Moderate (25.7 vs. 21.3 J/m, P<0.001); and Severe ARDS (28.7 vs. 23.5 J/m, P<0.001). Across 4 MPRS thresholds mortality increased from 23-29% when MPRS was < threshold vs. 38-51% when MPRS was > threshold (P<0.001). In the > cohort the Odds Ratio (95%CI) increased from 2.03 (1.34-3.12) to 2.51 (1.87-3.33).CONCLUSION: The pressure control surrogate formula is sufficiently accurate to assess mortality in ARDS, even when using volume control ventilation. In our subjects when MPRS exceeds established cut-off values for VILI or mortality risk, we found mortality risk consistently increased by a factor of > 2.0.

Open Access Data Repository and Common Data Model for Pulse Oximeter Performance Data.

The OpenOximetry Repository is a structured database storing clinical and lab pulse oximetry data, serving as a centralized repository and data model for pulse oximetry initiatives. It supports measurements of arterial oxygen saturation (SaO2) by arterial blood gas co-oximetry and pulse oximetry (SpO2), alongside processed and unprocessed photoplethysmography (PPG) data and other metadata. This includes skin color measurements, finger diameter, vital signs (e.g., arterial blood pressure, end-tidal carbon dioxide), and arterial blood gas parameters (e.g., acid-base balance, hemoglobin concentration). Data contributions are encouraged. All data, from desaturation studies to clinical trials, are collected prospectively to ensure accuracy. A common data model and standardized protocols for consistent archival and interpretation ensure consistent data archival and interpretation. The dataset aims to facilitate research on pulse oximeter performance across diverse human characteristics, addressing performance issues and promoting accurate pulse oximeters. The initial release includes controlled lab desaturation studies (CLDS), with ongoing updates planned as further data from clinical trials and CLDS become available.

Evidence Against Use of Nitrogen for the Death Penalty.

This Viewpoint discusses the recent use of forced nitrogen inhalation as capital punishment in Alabama and describes the body of evidence indicating that forced nitrogen inhalation is an inhumane practice.

The performance of 11 fingertip pulse oximeters during hypoxemia in healthy human participants with varied, quantified skin pigment.

BACKGROUND: Fingertip pulse oximeters are widely available, inexpensive, and commonly used to make clinical decisions in many settings. Device performance is largely unregulated and poorly characterised, especially in people with dark skin pigmentation. METHODS: Eleven popular fingertip pulse oximeters were evaluated using the US Food and Drug Administration (FDA) Guidance (2013) and International Organization for Standardization Standards (ISO, 2017) in 34 healthy humans with diverse skin pigmentation utilising a controlled desaturation study with arterial oxygen saturation (SaO 2) plateaus between 70% and 100%. Skin pigmentation was assessed subjectively using a perceived Fitzpatrick Scale (pFP) and objectively using the individual typology angle (ITA) via spectrophotometry at nine anatomical sites. FINDINGS: Five of 11 devices had a root mean square error (ARMS) > 3%, falling outside the acceptable FDA performance range. Nine devices demonstrated worse performance in participants in the darkest skin pigmentation category compared with those in the lightest category. A commonly used subjective skin colour scale frequently miscategorised participants as being darkly pigmented when compared to objective quantification of skin pigment by ITA. INTERPRETATION: Fingertip pulse oximeters have variable performance, frequently not meeting regulatory requirements for clinical use, and occasionally contradicting claims made by manufacturers. Most devices showed a trend toward worse performance in participants with darker skin pigment. Regulatory standards do not adequately account for the impact of skin pigmentation on device performance. We recommend that the pFP and other non-standardised subjective skin colour scales should no longer be used for defining diversity of skin pigmentation. Reliable methods for characterising skin pigmentation to improve diversity and equitable performance of pulse oximeters are needed. FUNDING: This study was conducted as part of the Open Oximetry Project funded by the Gordon and Betty Moore Foundation, Patrick J McGovern Foundation, and Robert Wood Johnson Foundation. The UCSF Hypoxia Research Laboratory receives funding from multiple industry sponsors to test the sponsors' devices for the purposes of product development and regulatory performance testing. Data in this paper do not include sponsor's study devices. All data were collected from devices procured by the Hypoxia Research Laboratory for the purposes of independent research. No company provided any direct funding for this study, participated in study design or analysis, or was involved in analysing data or writing the manuscript. None of the authors own stock or equity interests in any pulse oximeter companies. Dr Ellis Monk's time utilised for data analysis, reviewing and editing was funded by grant number: DP2MH132941.

The Global Anesthesia Workforce Survey: Updates and Trends in the Anesthesia Workforce.

BACKGROUND: There is a large global deficit of anesthesia providers. In 2016, the World Federation of Societies of Anaesthesiologists (WFSA) conducted a survey to count the number of anesthesia providers worldwide. Much work has taken place since then to strengthen the anesthesia health workforce. This study updates the global count of anesthesia providers. METHODS: Between 2021 and 2023, an electronic survey was sent to national professional societies of physician anesthesia providers (PAPs), nurse anesthetists, and other nonphysician anesthesia providers (NPAPs). Data included number of providers and trainees, proportion of females, and limited intensive care unit (ICU) capacity data. Descriptive statistics were calculated by country, World Bank income group, and World Health Organization (WHO) region. Provider density is reported as the number of providers per 100,000 population. RESULTS: Responses were obtained for 172 of 193 United Nations (UN) member countries. The global provider density was 8.8 (PAP 6.6 NPAP 2.3). Seventy-six countries had a PAP density <5, whereas 66 countries had a total provider density <5. PAP density increased everywhere except for high- and low-income countries and the African region. CONCLUSIONS: The overall size of the global anesthesia workforce has increased over time, although some countries have experienced a decrease. Population growth and differences in which provider types that are counted can have an important impact on provider density. More work is needed to define appropriate metrics for measuring changes in density, to describe anesthesia cadres, and to improve workforce data collection processes. Effort to scale up anesthesia provider training must urgently continue.

Low Perfusion and Missed Diagnosis of Hypoxemia by Pulse Oximetry in Darkly Pigmented Skin: A Prospective Study.

BACKGROUND: Retrospective clinical trials of pulse oximeter accuracy report more frequent missed diagnoses of hypoxemia in hospitalized Black patients than White patients, differences that may contribute to racial disparities in health and health care. Retrospective studies have limitations including mistiming of blood samples and oximeter readings, inconsistent use of functional versus fractional saturation, and self-reported race used as a surrogate for skin color. Our objective was to prospectively measure the contributions of skin pigmentation, perfusion index (PI), sex, and age on pulse oximeter errors in a laboratory setting. METHODS: We enrolled 146 healthy subjects, including 25 with light skin (Fitzpatrick class I and II), 78 with medium (class III and IV), and 43 with dark (class V and VI) skin. We studied 2 pulse oximeters (Nellcor N-595 and Masimo Radical 7) in prevalent clinical use. We analyzed 9763 matched pulse oximeter readings (pulse oximeter measured functional saturation [Sp o2 ]) and arterial oxygen saturation (hemoximetry arterial functional oxygen saturation [Sa o2 ]) during stable hypoxemia (Sa o2 68%-100%). PI was measured as percent infrared light modulation by the pulse detected by the pulse oximeter probe, with low perfusion categorized as PI < 1%. The primary analysis was to assess the relationship between pulse oximeter bias (difference between Sa o2 and Sp o2 ) by skin pigment category in a multivariable mixed-effects model incorporating repeated-measures and different levels of Sa o2 and perfusion. RESULTS: Skin pigment, PI, and degree of hypoxemia significantly contributed to errors (bias) in both pulse oximeters. For PI values of 1.0% to 1.5%, 0.5% to 1.0%, and <0.5%, the P value of the relationship to mean bias or median absolute bias was <.00001. In lightly pigmented subjects, only PI was associated with positive bias, whereas in medium and dark subjects bias increased with both low perfusion and degree of hypoxemia. Sex and age was not related to pulse oximeter bias. The combined frequency of missed diagnosis of hypoxemia (pulse oximeter readings 92%-96% when arterial oxygen saturation was <88%) in low perfusion conditions was 1.1% for light, 8.2% for medium, and 21.1% for dark skin. CONCLUSIONS: Low peripheral perfusion combined with darker skin pigmentation leads to clinically significant high-reading pulse oximeter errors and missed diagnoses of hypoxemia. Darkly pigmented skin and low perfusion states are likely the cause of racial differences in pulse oximeter performance in retrospective studies.

Capnography-An Essential Monitor, Everywhere: A Narrative Review.

Capnography is now recognized as an indispensable patient safety monitor. Evidence suggests that its use improves outcomes in operating rooms, intensive care units, and emergency departments, as well as in sedation suites, in postanesthesia recovery units, and on general postsurgical wards. Capnography can accurately and rapidly detect respiratory, circulatory, and metabolic derangements. In addition to being useful for diagnosing and managing esophageal intubation, capnography provides crucial information when used for monitoring airway patency and hypoventilation in patients without instrumented airways. Despite its ubiquitous use in high-income-country operating rooms, deaths from esophageal intubations continue to occur in these contexts due to incorrect use or interpretation of capnography. National and international society guidelines on airway management mandate capnography's use during intubations across all hospital areas, and recommend it when ventilation may be impaired, such as during procedural sedation. Nevertheless, capnography's use across high-income-country intensive care units, emergency departments, and postanesthesia recovery units remains inconsistent. While capnography is universally used in high-income-country operating rooms, it remains largely unavailable to anesthesia providers in low- and middle-income countries. This lack of access to capnography likely contributes to more frequent and serious airway events and higher rates of perioperative mortality in low- and middle-income countries. New capnography equipment, which overcomes cost and context barriers, has recently been developed. Increasing access to capnography in low- and middle-income countries must occur to improve patient outcomes and expand universal health care. It is time to extend capnography's safety benefits to all patients, everywhere.

Quantifying pulse oximeter accuracy during hypoxemia and severe anemia using an in vitro circulation system.

Anemia and hypoxemia are common clinical conditions that are difficult to study and may impact pulse oximeter performance. Utilizing an in vitro circulation system, we studied performance of three pulse oximeters during hypoxemia and severe anemia. Three oximeters including one benchtop, one handheld, and one fingertip device were selected to reflect a range of cost and device types. Human blood was diluted to generate four hematocrit levels (40%, 30%, 20%, and 10%). Oxygen and nitrogen were bubbled through the blood to generate a range of oxygen saturations (O2Hb) and the blood was cycled through the in vitro circulation system. Pulse oximeter saturations (SpO2) were paired with simultaneously-measured O2Hb readings from a reference CO-oximeter. Data for each hematocrit level and each device were least-squares fit to a 2nd-order equation with quality of each curve fit evaluated using standard error of the estimate. Bias and average root mean square error were calculated after correcting for the calibration difference between human and in vitro circulation system calibration. The benchtop oximeter maintained good accuracy at all but the most extreme level of anemia. The handheld device was not as accurate as the benchtop, and inaccuracies increased at lower hematocrit levels. The fingertip device was the least accurate of the three oximeters. Pulse oximeter performance is impacted by severe anemia in vitro. The use of in vitro calibration systems may play an important role in augmenting in vivo performance studies evaluating pulse oximeter performance in challenging conditions.

Availability of information needed to evaluate algorithmic fairness - A systematic review of publicly accessible critical care databases.

BACKGROUND: Machine learning (ML) may improve clinical decision-making in critical care settings, but intrinsic biases in datasets can introduce bias into predictive models. This study aims to determine if publicly available critical care datasets provide relevant information to identify historically marginalized populations. METHOD: We conducted a review to identify the manuscripts that report the training/validation of ML algorithms using publicly accessible critical care electronic medical record (EMR) datasets. The datasets were reviewed to determine if the following 12 variables were available: age, sex, gender identity, race and/or ethnicity, self-identification as an indigenous person, payor, primary language, religion, place of residence, education, occupation, and income. RESULTS: 7 publicly available databases were identified. Medical Information Mart for Intensive Care (MIMIC) reports information on 7 of the 12 variables of interest, Sistema de Informação de Vigilância Epidemiológica da Gripe (SIVEP-Gripe) on 7, COVID-19 Mexican Open Repository on 4, and eICU on 4. Other datasets report information on 2 or fewer variables. All 7 databases included information about sex and age. Four databases (57%) included information about whether a patient identified as native or indigenous. Only 3 (43%) included data about race and/or ethnicity. Two databases (29%) included information about residence, and one (14%) included information about payor, language, and religion. One database (14%) included information about education and patient occupation. No databases included information on gender identity and income. CONCLUSION: This review demonstrates that critical care publicly available data used to train AI algorithms do not include enough information to properly look for intrinsic bias and fairness issues towards historically marginalized populations.

Oxygen saturation targets for adults with acute hypoxemia in low and lower-middle income countries: a scoping review with analysis of contextual factors.

Knowing the target oxygen saturation (SpO2) range that results in the best outcomes for acutely hypoxemic adults is important for clinical care, training, and research in low-income and lower-middle income countries (collectively LMICs). The evidence we have for SpO2 targets emanates from high-income countries (HICs), and therefore may miss important contextual factors for LMIC settings. Furthermore, the evidence from HICs is mixed, amplifying the importance of specific circumstances. For this literature review and analysis, we considered SpO2 targets used in previous trials, international and national society guidelines, and direct trial evidence comparing outcomes using different SpO2 ranges (all from HICs). We also considered contextual factors, including emerging data on pulse oximetry performance in different skin pigmentation ranges, the risk of depleting oxygen resources in LMIC settings, the lack of access to arterial blood gases that necessitates consideration of the subpopulation of hypoxemic patients who are also hypercapnic, and the impact of altitude on median SpO2 values. This process of integrating prior study protocols, society guidelines, available evidence, and contextual factors is potentially useful for the development of other clinical guidelines for LMIC settings. We suggest that a goal SpO2 range of 90-94% is reasonable, using high-performing pulse oximeters. Answering context-specific research questions, such as an optimal SpO2 target range in LMIC contexts, is critical for advancing equity in clinical outcomes globally.

A Cross-Sectional Survey of Anesthetic Airway Equipment and Airway Management Practices in Uganda.

BACKGROUND: Anesthesia-related causes contribute to a significant proportion of perioperative deaths, especially in low and middle-income countries (LMICs). There is evidence that complications related to failed airway management are a significant contributor to perioperative morbidity and mortality. While existing data have highlighted the magnitude of airway management complications in LMICs, there are inadequate data to understand their root causes. This study aimed to pilot an airway management capacity tool that evaluates airway management resources, provider practices, and experiences with difficult airways in an attempt to better understand potential contributing factors to airway management challenges. METHODS: We developed a novel airway management capacity assessment tool through a nonsystematic review of existing literature on anesthesia and airway management in LMICs, internationally recognized difficult airway algorithms, minimum standards for equipment, the safe practice of anesthesia, and the essential medicines and health supplies list of Uganda. We distributed the survey tool during conferences and workshops, to anesthesia care providers from across the spectrum of surgical care facilities in Uganda. The data were analyzed using descriptive methods. RESULTS: Between May 2017 and May 2018, 89 of 93 surveys were returned (17% of anesthesia providers in the country) from all levels of health facilities that provide surgical services in Uganda. Equipment for routine airway management was available to all anesthesia providers surveyed, but with a limited range of sizes. Pediatric airway equipment was always available 54% of the time. There was limited availability of capnography (15%), video laryngoscopes (4%), cricothyroidotomy kits (6%), and fiber-optic bronchoscopes (7%). Twenty-one percent (18/87) of respondents reported experiencing a "can't intubate, can't ventilate" (CICV) scenario in the 12 months preceding the survey, while 63% (54/86) reported experiencing at least 1 CICV during their career. Eighty-five percent (74/87) of respondents reported witnessing a severe airway management complication during their career, with 21% (19/89) witnessing a death as a result of a CICV scenario. CONCLUSIONS: We have developed and implemented an airway management capacity tool that describes airway management practices in Uganda. Using this tool, we have identified significant gaps in access to airway management resources. Gaps identified by the survey, along with advocacy by the Association of Anesthesiologists of Uganda, in partnership with the Ugandan Ministry of Health, have led to some progress in closing these gaps. Expanding the availability of airway management resources further, providing more airway management training, and identifying opportunities to support skilled workforce expansion have the potential to improve perioperative safety in Uganda.

Utilization of a Risk Stratification Tool and Volume-Based Cuff Leak Test to Assess Postextubation Stridor.

BACKGROUND: Postextubation stridor (PES) is an imminently life-threatening event. Maximizing patient safety requires a systematic approach to screen patients for PES risk factors and a standardized test to evaluate that risk. This retrospective study of adult subjects was based on quality assurance data including standardized surveillance screening criteria and a volume-based cuff leak test (CLT) to evaluate PES risk among predominantly surgical-trauma and neurotrauma subjects. Data characterizing PES subjects also were collected. METHODS: Data were collected between May 2010-December 2017 for all intubated subjects in our surgical-trauma, neurotrauma, and medical ICUs. Respiratory therapists were trained in performing both PES risk assessment surveillance and a volume-based CLT. A pre hoc cutoff leak volume of < 110 mL defined a true positive test result when associated with PES, and a leak ≥ 110 mL defined a true negative test if PES was absent. Multiple comparisons were analyzed by Kruskal-Wallis tests and dichotomous variables assessed by Fisher exact tests. Alpha was set at 0.05. RESULTS: In 681 pre-extubation CLTs ∼85% produced true-negative results and 15% consisted of true-positive (∼4%), false-negative (∼5%), and false-positive (∼6%) results. Positive and negative predictive values were 0.42 (0.32-0.54) and 0.94 (0.92-0.96), respectively. The PES likelihood ratio was 7.0, and correct classification was 89%. Of the 115 PES incidences occurring in 112 PES cases, 67% were female and 48% had suffered acute brain injury. CONCLUSIONS: Among predominantly surgical-trauma and neurotrauma subjects with a CLT, leak volume of ≥ 110 mL was associated with a PES risk of ∼6%, whereas the risk of PES was 7 times greater when the leak volume was < 110 mL.

Respiratory Drive, Dyspnea, and Silent Hypoxemia: A Physiological Review in the Context of COVID-19.

Infection with SARS-CoV-2 in select individuals results in viral sepsis, pneumonia, and hypoxemic respiratory failure, collectively known as COVID-19. In the early months of the pandemic, the combination of novel disease presentation, enormous surges of critically ill patients, and severity of illness lent to early observations and pronouncements regarding COVID-19 that could not be scientifically validated owing to crisis circumstances. One of these was a phenomenon referred to as "happy hypoxia." Widely discussed in the lay press, it was thought to represent a novel and perplexing phenomenon: severe hypoxemia coupled with the absence of respiratory distress and dyspnea. Silent hypoxemia is the preferred term describing an apparent lack of distress in the presence of hypoxemia. However, the phenomenon is well known among respiratory physiologists as hypoxic ventilatory decline. Silent hypoxemia can be explained by physiologic mechanisms governing the control of breathing, breathing perception, and cardiovascular compensation. This narrative review examines silent hypoxemia during COVID-19 as well as hypotheses that viral infection of the central and peripheral nervous system may be implicated. Moreover, the credulous embrace of happy hypoxia and the novel hypotheses proposed to explain it has exposed significant misunderstandings among clinicians regarding the physiologic mechanisms governing both the control of breathing and the modulation of breathing sensations. Therefore, a substantial focus of this paper is to provide an in-depth review of these topics.

Treating COVID-19: Evolving approaches to evidence in a pandemic.

The rapid pace of the COVID-19 pandemic precluded traditional approaches to evaluating clinical research and guidelines. We highlight notable successes and pitfalls of clinicians' new approaches to managing evidence amidst an unprecedented crisis. In "Era 1" (early 2020), clinicians relied on anecdote and social media, which democratized conversations on guidelines, but also led clinicians astray. "Era 2" (approximately late 2020 to early 2021) saw preprints that accelerated new interventions but suffered from a surfeit of poor-quality data. In the current era, clinicians consolidate the evidentiary gains of Era 2 with living, online clinical guidelines, but the public suffers from misinformation. The COVID-19 pandemic is a laboratory on how clinicians adapt to an absence of clinical guidance amidst an informational and healthcare crisis. Challenges remain as we integrate new approaches to innovations made in the traditional guideline process to confront both the long tail of COVID-19 and future pandemics.

Pulse Oximeter Performance, Racial Inequity, and the Work Ahead.

It has long been known that many pulse oximeters function less accurately in patients with darker skin. Reasons for this observation are incompletely characterized and potentially enabled by limitations in existing regulatory oversight. Based on decades of experience and unpublished data, we believe it is feasible to fully characterize, in the public domain, the factors that contribute to missing clinically important hypoxemia in patients with darkly pigmented skin. Here we propose 5 priority areas of inquiry for the research community and actionable changes to current regulations that will help improve oximeter accuracy. We propose that leading regulatory agencies should immediately modify standards for measuring accuracy and precision of oximeter performance, analyzing and reporting performance outliers, diversifying study subject pools, thoughtfully defining skin pigmentation, reporting data transparently, and accounting for performance during low-perfusion states. These changes will help reduce bias in pulse oximeter performance and improve access to safe oximeters.

Academic Global Surgery Curricula: Current Status and a Call for a More Equitable Approach.

INTRODUCTION: We aimed to search the literature for global surgical curricula, assess if published resources align with existing competency frameworks in global health and surgical education, and determine if there is consensus around a fundamental set of competencies for the developing field of academic global surgery. METHODS: We reviewed SciVerse SCOPUS, PubMed, African Medicus Index, African Journals Online (AJOL), SciELO, Latin American and Caribbean Health Sciences Literature (LILACS) and Bioline for manuscripts on global surgery curricula and evaluated the results using existing competency frameworks in global health and surgical education from Consortium of the Universities for Global Health (CUGH) and Accreditation Council for Graduate Medical Education (ACGME) professional competencies. RESULTS: Our search generated 250 publications, of which 18 were eligible: (1) a total of 10 reported existing competency-based curricula that were concurrent with international experiences, (2) two reported existing pre-departure competency-based curricula, (3) six proposed theoretical competency-based curricula for future global surgery education. All, but one, were based in high-income countries (HICs) and focused on the needs of HIC trainees. None met all 17 competencies, none cited the CUGH competency on "Health Equity and Social Justice" and only one mentioned "Social and Environmental Determinants of Health." Only 22% (n = 4) were available as open-access. CONCLUSION: Currently, there is no universally accepted set of competencies on the fundamentals of academic global surgery. Existing literature are predominantly by and for HIC institutions and trainees. Current frameworks are inadequate for this emerging academic field. The field needs competencies with explicit input from LMIC experts to ensure creation of educational resources that are accessible and relevant to trainees from around the world.