Imaging the pulmonary vasculature in acute respiratory distress syndrome.

Acute respiratory distress syndrome (ARDS) is characterized by a redistribution of regional lung perfusion that impairs gas exchange. While speculative, experimental evidence suggests that perfusion redistribution may contribute to regional inflammation and modify disease progression. Unfortunately, tools to visualize and quantify lung perfusion in patients with ARDS are lacking. This review explores recent advances in perfusion imaging techniques that aim to understand the pulmonary circulation in ARDS. Dynamic contrast-enhanced computed tomography captures first-pass kinetics of intravenously injected dye during continuous scan acquisitions. Different contrast characteristics and kinetic modeling have improved its topographic measurement of pulmonary perfusion with high spatial and temporal resolution. Dual-energy computed tomography can map the pulmonary blood volume of the whole lung with limited radiation exposure, enabling its application in clinical research. Electrical impedance tomography can obtain serial topographic assessments of perfusion at the bedside in response to treatments such as inhaled nitric oxide and prone position. Ongoing technological improvements and emerging techniques will enhance lung perfusion imaging and aid its incorporation into the care of patients with ARDS.

Electrical Impedance Tomography Identifies Evolution of Regional Perfusion in a Porcine Model of Acute Respiratory Distress Syndrome.

BACKGROUND: Bedside electrical impedance tomography could be useful to visualize evolving pulmonary perfusion distributions when acute respiratory distress syndrome worsens or in response to ventilatory and positional therapies. In experimental acute respiratory distress syndrome, this study evaluated the agreement of electrical impedance tomography and dynamic contrast-enhanced computed tomography perfusion distributions at two injury time points and in response to increased positive end-expiratory pressure (PEEP) and prone position. METHODS: Eleven mechanically ventilated (VT 8 ml · kg-1) Yorkshire pigs (five male, six female) received bronchial hydrochloric acid (3.5 ml · kg-1) to invoke lung injury. Electrical impedance tomography and computed tomography perfusion images were obtained at 2 h (early injury) and 24 h (late injury) after injury in supine position with PEEP 5 and 10 cm H2O. In eight animals, electrical impedance tomography and computed tomography perfusion imaging were also conducted in the prone position. Electrical impedance tomography perfusion (QEIT) and computed tomography perfusion (QCT) values (as percentages of image total) were compared in eight vertical regions across injury stages, levels of PEEP, and body positions using mixed-effects linear regression. The primary outcome was agreement between QEIT and QCT, defined using limits of agreement and Pearson correlation coefficient. RESULTS: Pao2/Fio2 decreased over the course of the experiment (healthy to early injury, -253 [95% CI, -317 to -189]; early to late injury, -88 [95% CI, -151 to -24]). The limits of agreement between QEIT and QCT were -4.66% and 4.73% for the middle 50% quantile of average regional perfusion, and the correlation coefficient was 0.88 (95% CI, 0.86 to 0.90]; P < 0.001). Electrical impedance tomography and computed tomography showed similar perfusion redistributions over injury stages and in response to increased PEEP. QEIT redistributions after positional therapy underestimated QCT in ventral regions and overestimated QCT in dorsal regions. CONCLUSIONS: Electrical impedance tomography closely approximated computed tomography perfusion measures in experimental acute respiratory distress syndrome, in the supine position, over injury progression and with increased PEEP. Further validation is needed to determine the accuracy of electrical impedance tomography in measuring perfusion redistributions after positional changes.

Regional lung perfusion using different indicators in electrical impedance tomography.

Management of acute respiratory distress syndrome (ARDS) is classically guided by protecting the injured lung and mitigating damage from mechanical ventilation. Yet the natural history of ARDS is also dictated by disruption in lung perfusion. Unfortunately, diagnosis and treatment are hampered by the lack of bedside perfusion monitoring. Electrical impedance tomography is a portable imaging technique that can estimate regional lung perfusion in experimental settings from the kinetic analysis of a bolus of an indicator with high conductivity. Hypertonic sodium chloride has been the standard indicator. However, hypertonic sodium chloride is often inaccessible in the hospital, limiting practical adoption. We investigated whether regional lung perfusion measured using electrical impedance tomography is comparable between indicators. Using a swine lung injury model, we determined regional lung perfusion (% of total perfusion) in five pigs, comparing 12% sodium chloride to 8.4% sodium bicarbonate across stages of lung injury and experimental conditions (body position, positive end-expiratory pressure). Regional lung perfusion for four lung regions was determined from maximum slope analysis of the indicator-based impedance signal. Estimates of regional lung perfusion between indicators were compared in the lung overall and within four lung regions. Regional lung perfusion estimated with a sodium bicarbonate indicator agreed with a hypertonic sodium chloride indicator overall (mean bias 0%, limits of agreement -8.43%, 8.43%) and within lung quadrants. The difference in regional lung perfusion between indicators did not change across experimental conditions. Sodium bicarbonate may be a comparable indicator to estimate regional lung perfusion using electrical impedance tomography.NEW & NOTEWORTHY Electrical impedance tomography is an emerging tool to measure regional lung perfusion using kinetic analysis of a conductive indicator. Hypertonic sodium chloride is the standard agent used. We measured regional lung perfusion using another indicator, comparing hypertonic sodium chloride to sodium bicarbonate in an experimental swine lung injury model. We found strong agreement between the two indicators. Sodium bicarbonate may be a comparable indicator to measure regional lung perfusion with electrical impedance tomography.

Improving pulmonary perfusion assessment by dynamic contrast-enhanced computed tomography in an experimental lung injury model.

Pulmonary perfusion has been poorly characterized in acute respiratory distress syndrome (ARDS). Optimizing protocols to measure pulmonary blood flow (PBF) via dynamic contrast-enhanced (DCE) computed tomography (CT) could improve understanding of how ARDS alters pulmonary perfusion. In this study, comparative evaluations of injection protocols and tracer-kinetic analysis models were performed based on DCE-CT data measured in ventilated pigs with and without lung injury. Ten Yorkshire pigs (five with lung injury, five healthy) were anesthetized, intubated, and mechanically ventilated; lung injury was induced by bronchial hydrochloric acid instillation. Each DCE-CT scan was obtained during a 30-s end-expiratory breath-hold. Reproducibility of PBF measurements was evaluated in three pigs. In eight pigs, undiluted and diluted Isovue-370 were separately injected to evaluate the effect of contrast viscosity on estimated PBF values. PBF was estimated with the peak-enhancement and the steepest-slope approach. Total-lung PBF was estimated in two healthy pigs to compare with cardiac output measured invasively by thermodilution in the pulmonary artery. Repeated measurements in the same animals yielded a good reproducibility of computed PBF maps. Injecting diluted isovue-370 resulted in smaller contrast-time curves in the pulmonary artery (P < 0.01) and vein (P < 0.01) without substantially diminishing peak signal intensity (P = 0.46 in the pulmonary artery) compared with the pure contrast agent since its viscosity is closer to that of blood. As compared with the peak-enhancement model, PBF values estimated by the steepest-slope model with diluted contrast were much closer to the cardiac output (R2 = 0.82) as compared with the peak-enhancement model. DCE-CT using the steepest-slope model and diluted contrast agent provided reliable quantitative estimates of PBF.NEW & NOTEWORTHY Dynamic contrast-enhanced CT using a lower-viscosity contrast agent in combination with tracer-kinetic analysis by the steepest-slope model improves pulmonary blood flow measurements and assessment of regional distributions of lung perfusion.

Does Masked Interviewing Encourage Holistic Review in Residency Selection? A Mixed-Methods Study.

Problem: Medical educators increasingly champion holistic review. However, in U.S. residency selection, holistic review has been difficult to implement, hindered by a reliance on standardized academic criteria such as board scores. Masking faculty interviewers to applicants' academic files is a potential means of promoting holistic residency selection by increasing the interview's ability to make a discrete contribution to evaluation. However, little research has directly analyzed the effects of masking on how residency selection committees evaluate applicants. This mixed-methods study examined how masking interviews altered residency selection in an anesthesiology program at a large U.S. academic medical center. Intervention: During the 2019-2020 residency selection season in the University of Pennsylvania's Department of Anesthesiology & Critical Care, we masked interviewers to the major academic components of candidates' application files (board scores, transcripts, letters) on approximately half of interview days. The intent of the masking intervention was to mitigate the tendency of interviewers to form predispositions about candidates based on standardized academic criteria and thereby allow the interview to make a more independent contribution to candidate evaluation. Context: Our examination of the masking intervention used a concurrent, partially mixed, equal-status mixed-methods design guided by a pragmatist approach. We audio-recorded selection committee meetings and qualitatively analyzed them to explore how masking affected the process of candidate evaluation. We also collected independent candidate ratings from interviewers and consensus committee ratings and statistically compared ratings of candidates interviewed on masked days to ratings from conventional days. Impact: In conventional committee meetings, interviewers focused on how to reconcile academic metrics and interviews, and their evaluations of interviews were framed according to predispositions about candidates formed through perusal of application files. In masked meetings, members instead spent considerable effort evaluating candidates' "fit" and whether they came off as tactful. Masked interviewers gave halting opinions of candidates and sometimes pushed for committee leaders to reveal academic information, leading to masking breaches. Higher USMLE Step 1 score and higher medical school ranking were statistically associated with more favorable consensus rating. We found no significant differences in rating outcomes between masked and conventional interview days. Lessons learned: Elimination of academic metrics during the residency interview phase does not straightforwardly promote holistic review. While critical reflection among medical educators about the fairness and utility of such metrics has been productive, research and intervention should focus on the more proximate topic of how programs apply academic and other criteria to evaluate applicants.

Motor Vehicle Crash Risk among Adults Undergoing General Surgery: A Retrospective Case-crossover Study.

BACKGROUND: Surgery causes transient impairment in cognition and function, which may impact driving safety. The authors hypothesized that the risk of a motor vehicle crash would increase after compared to before surgery. METHODS: The authors performed a nested case-crossover study within population-based observational data from the New Jersey Safety Health Outcomes Data Warehouse. The study included adults 18 yr or older with a valid driver's license who underwent general surgery in an acute care hospital in New Jersey between January 1, 2016, and November 30, 2017, and were discharged home. Individuals served as their own controls within a presurgery interval (56 days to 28 days before surgery) and postsurgery interval (discharge through 28 days after surgery). General surgery was defined by Common Procedural Terminology Codes. The primary outcome was a police-reported motor vehicle crash. RESULTS: In a cohort of 70,722 drivers, the number of crashes after surgery was 263 (0.37%) compared to 279 (0.39%) before surgery. Surgery was not associated with a change in crash incidence greater than 28 days using a case-crossover design (adjusted incidence rate ratio, 0.92; 95% CI, 0.78 to 1.09; P = 0.340). Statistical interaction was present for sex and hospital length of stay. Younger versus older adults (adjusted risk ratio, 1.87; 95% CI, 1.10 to 3.18; P = 0.021) and non-Hispanic Black individuals (adjusted risk ratio, 1.96; 95% CI, 1.33 to 2.88; P = 0.001) and Hispanic individuals (adjusted risk ratio, 1.38; 95% CI, 1.00 to 1.91; P = 0.047) versus non-Hispanic White individuals had a greater risk of a crash after surgery. CONCLUSIONS: Using population-based crash and hospital discharge data, the incidence of motor vehicle crashes over a 28-day period did not change on average before compared to after surgery. The authors provide data on crash risk after surgery and highlight specific populations at risk.

A Prospective Observational Study on Short and Long-Term Outcomes of COVID-19 Patients with Acute Hypoxic Respiratory Failure Treated with High-Flow Nasal Cannula.

(1) The use of high-flow nasal cannula (HFNC) combined with frequent respiratory monitoring in patients with acute hypoxic respiratory failure due to COVID-19 has been shown to reduce intubation and mechanical ventilation. (2) This prospective, single-center, observational study included consecutive adult patients with COVID-19 pneumonia treated with a high-flow nasal cannula. Hemodynamic parameters, respiratory rate, inspiratory fraction of oxygen (FiO2), saturation of oxygen (SpO2), and the ratio of oxygen saturation to respiratory rate (ROX) were recorded prior to treatment initiation and every 2 h for 24 h. A 6-month follow-up questionnaire was also conducted. (3) Over the study period, 153 of 187 patients were eligible for HFNC. Of these patients, 80% required intubation and 37% of the intubated patients died in hospital. Male sex (OR = 4.65; 95% CI [1.28; 20.6], p = 0.03) and higher BMI (OR = 2.63; 95% CI [1.14; 6.76], p = 0.03) were associated with an increased risk for new limitations at 6-months after hospital discharge. (4) 20% of patients who received HFNC did not require intubation and were discharged alive from the hospital. Male sex and higher BMI were associated with poor long-term functional outcomes.

Respiratory mechanics and mortality in coronavirus disease 2019 acute respiratory distress syndrome: A retrospective cohort study.

BACKGROUND: The association between commonly monitored respiratory parameters, including compliance and oxygenation and clinical outcomes in acute respiratory distress syndrome (ARDS) from coronavirus disease 2019 (COVID-19) remains unclear, limiting prognostication and the delivery of targeted treatments. Our project aim was to identify if any such associations exist between clinical outcomes and respiratory parameters. METHODS: We performed a retrospective observational cohort study of confirmed COVID-19 positive patients admitted to a single dedicated intensive care unit at a university hospital from March 27 to April 26, 2020. We collected information on baseline clinical and demographic characteristics and initial respiratory parameters. Our primary outcome was in-hospital mortality. RESULTS: A total of 22 patients met criteria for ARDS and were included in our study. Nine of the 22 (40.9%) patients with ARDS died during hospitalization. The initial static respiratory system compliance of survivors was 39 (interquartile range [IQR] 34, 55) and nonsurvivors was 27 (IQR 24, 33, P < 0.01). A lower respiratory system compliance was associated with an increased adjusted odd of in-hospital mortality (odds ratio 1.2, 95% confidence interval 1.01, 1.45 P = 0.04). CONCLUSION: In our cohort of 22 patients mechanically ventilated with ARDS from COVID-19, having lower respiratory system compliance after intubation was associated with an increased risk of in-hospital mortality, consistent with ARDS from non-COVID etiologies.

Association of hospitalization with driving reduction and cessation in older adults.

BACKGROUND: Driving has not been considered as part of the social cost of acute illness and may go unnoticed in the post-hospital care of older adults. Decreases in driving after hospitalization and at-risk populations have not been investigated. OBJECTIVE: To determine the association between driving reduction and cessation and hospitalization in older adults by using nationally representative data. DESIGN: Retrospective cohort analysis. SETTING: Health and Retirement Study survey from 2004 to 2014. PARTICIPANTS: Adults aged 65 years and older who were able to drive and had an available car (n = 12,110; 40,364 interviews). MEASUREMENTS: Self-report of a hospitalization requiring an overnight stay, changes in driving patterns including driving cessation or limitations over a 2-year period, comorbid conditions, health utilization, and behaviors. RESULTS: Of hospitalizations in adults aged 65 years and older, 22% were associated with a decrease in driving patterns within 2 years. The relative risk of a reduction or cessation in driving was 1.62 (95% CI: 1.54, 1.70, p < 0.001) when there was a hospitalization compared with when a hospitalization did not occur. Baseline functional, cognitive, and visual impairment, fair or poor self-rated health, and diabetes were identified as independent risk factors for decreased driving patterns after hospitalization. CONCLUSIONS: Changes in driving patterns are common after a hospitalization in older adults. The findings suggest that driving, although not a current goal of post-hospital care, is important to the continued autonomy and community mobility of older adults and needs to be addressed as part of discharge planning and their recovery.

Preoperative Sedative-hypnotic Medication Use and Adverse Postoperative Outcomes.

OBJECTIVE: To determine the association between preoperative benzodiazepine and nonbenzodiazepine receptor agonist ("Z-drugs") use and adverse outcomes after surgery. BACKGROUND: Prescriptions for benzodiazepines and Z-drugs have increased over the past decade. Despite this, the association of preoperative benzodiazepines and Z-drug receipt with adverse outcomes after surgery is unknown. METHODS: Using the Optum Clinformatics Datamart, we performed a retrospective cohort study of adults 18 years or older who underwent any of 10 common surgical procedures between 2010 and 2015. The principal exposure was one or more filled prescriptions for a benzodiazepine or Z-drug in the 90 days before surgery. The primary outcome was any emergency department visit or hospital admission for either (1) a drug related adverse medical event or overdose or (2) a traumatic injury in the 30 days after surgery. RESULTS: Of 785,346 patients meeting inclusion criteria, 94,887 (12.1%) filled a preoperative prescription for a benzodiazepine or Z-drug. From multivariable logistic regression, benzodiazepine or Z-drug use was associated with an increased odds of an adverse postoperative event [odds ratio 1.13; 95% confidence interval: 1.08-1.18). In a separate regression, coprescription of benzodiazepines or Z-drugs with opioids was associated with a 1.45 odds of an adverse postoperative event (95% confidence interval: 1.37-1.53). CONCLUSIONS: Preoperative benzodiazepines and Z-drug use is common and associated with increased odds of adverse outcomes after surgery, particularly when coprescribed with opioids. Counseling on appropriate benzodiazepine and Z-drug use in advance of elective surgery may potentially increase the safety of surgical care.

Using Medicare claims in identifying Alzheimer's disease and related dementias.

INTRODUCTION: This study develops a measure of Alzheimer's disease and related dementias (ADRD) using Medicare claims. METHODS: Validation resembles the approach of the American Psychological Association, including (1) content validity, (2) construct validity, and (3) predictive validity. RESULTS: We found that four items-a Medicare claim recording ADRD 1 year ago, 2 years ago, 3 years ago, and a total stay of 6 months in a nursing home-exhibit a pattern of association consistent with a single underlying ADRD construct, and presence of any two of these four items predict a direct measure of cognitive function and also future claims for ADRD. DISCUSSION: Our four items are internally consistent with the measurement of a single quantity. The presence of any two items do a better job than a single claim when predicting both a direct measure of cognitive function and future ADRD claims.

The role of the interview in residency selection: A mixed-methods study.

CONTEXT: Residency programmes invest considerable time and resources in candidate interviews as a result of their perceived ability to reveal important social traits. However, studies examining the ability of interviews to predict resident performance have shown mixed findings, and the role of the interview in candidate evaluation remains unclear. This mixed-methods study, conducted in an anaesthesiology residency programme at a large academic medical centre, examined how interviews contributed to candidate assessment and whether the addition of behavioural questions to interviews altered their role in the evaluation process. METHODS: During the 2018-2019 residency selection season in the Department of Anesthesiology and Critical Care at the University of Pennsylvania, independent ratings for each interviewee were collected from faculty interviewers. Consensus ratings subsequently established by committee were also collected. Committee meetings were audiorecorded and transcribed for qualitative analysis. Behavioural questions were integrated into half of interview days. Ratings of candidates interviewed on behavioural question days were compared statistically with those of candidates interviewed on non-behavioural question days. RESULTS: Qualitative analysis showed that interviewers heavily emphasised candidates' application files in evaluating the interviews. Interviewers focused on candidates' academic records and favoured candidates whose interview behaviours were consistent with their applications and whose applications demonstrated similarities to interviewers' traits. The addition of behavioural questions demonstrated little ability to alter these dynamics. Quantitatively, there were no significant differences in candidate rating outcomes between behavioural and non-behavioural interviewing days, whereas a higher medical school rating and higher score on the United States Medical Licensing Examination Step 1 were associated with a more favourable consensus rating. CONCLUSIONS: Residency candidates' application files predisposed interviewers' experience and evaluation of interviews, preventing the interviews from providing discrete assessments of interpersonal qualities, even when behavioural questions were included. In the continued effort to perform well-rounded assessments of residency candidates, further research and reflection on the role of interviewing in evaluation are necessary.

Observational Study of the Associations of Participation in High School Football With Self-Rated Health, Obesity, and Pain in Adulthood.

American football is the most popular high school sport in the United States, yet its association with health in adulthood has not been widely studied. We investigated the association between high school football and self-rated health, obesity, and pain in adulthood in a retrospective cohort study of data from the Wisconsin Longitudinal Study (1957-2004). We matched 925 males who played varsity football in high school with 1,521 males who did not play football. After matching, playing football was not associated with poor or fair self-rated health (odds ratio (OR) = 0.88, 95% confidence interval (CI): 0.63, 1.24; P = 0.48) or pain that limited activities (OR = 0.86, 95% CI: 0.59, 1.25; P = 0.42) at age 65 years. Football was associated with obesity (body mass index (weight (kg)height (m)2) ≥30) in adulthood (OR = 1.32, 95% CI: 1.06, 1.64; P = 0.01). The findings suggest that playing football in high school was not significantly associated with poor or fair self-related health at age 65 years, but it was associated with the risk of being obese as an adult in comparison with not playing football in high school. Our findings provide needed information about the risk of playing football with regard to a broader set of health outcomes.

Prevalence and Multivariable Factors Associated With Preoperative Cognitive Impairment in Outpatient Surgery in the United States.

Preoperative cognitive impairment increases the risk of adverse events after surgery but its prevalence in outpatient surgery has not been defined. We aimed to determine the prevalence and multivariable factors associated with cognitive impairment in individuals who present for outpatient surgery. We used data from the Health and Retirement Study, a longitudinal panel survey of older Americans. Of 1836 participants who reported having outpatient surgery, we found that 16.1% had evidence of cognitive impairment. Significant multivariable factors associated with preoperative cognitive impairment included non-Hispanic African American race, prior stroke, preoperative functional dependence, and lower socioeconomic status and education level.

The older adult with preexisting neurocognitive disorder.

PURPOSE OF REVIEW: With the ageing population, there is an increasing number of patients with a neurocognitive disorder (NCD) who undergo surgical procedures. The aim of this review is to highlight the epidemiology of preoperative NCD. RECENT FINDINGS: New guidelines have defined NCD into mild NCD and major NCD consistent with terminology from the wider clinical community. Several assessment tools have been used in the preoperative setting to identify patients with evidence of cognitive decline. NCD prior to surgery remains a major risk factor postoperative delirium. SUMMARY: Cognitive dysfunction is common prior to surgery. Awareness of dysfunction, especially when taking care of older adults, is critical given the high risk of complications in this population.