Racial Differences in Blood Pressure and Autonomic Recovery Following Acute Supramaximal Exercise in Women.

Despite the growing popularity of high-intensity anaerobic exercise, little is known about the acute effects of this form of exercise on cardiovascular hemodynamics or autonomic modulation, which might provide insight into the individual assessment of responses to training load. The purpose of this study was to compare blood pressure and autonomic recovery following repeated bouts of acute supramaximal exercise in Black and White women. A convenience sample of twelve White and eight Black young, healthy women were recruited for this study and completed two consecutive bouts of supramaximal exercise on the cycle ergometer with 30 min of recovery in between. Brachial and central aortic blood pressures were assessed by tonometry (SphygmoCor Xcel) at rest and 15-min and 30-min following each exercise bout. Central aortic blood pressure was estimated using brachial pressure waveforms and customized software. Autonomic modulation was measured in a subset of ten participants by heart-rate variability and baroreflex sensitivity. Brachial mean arterial pressure and diastolic blood pressure were significantly higher in Blacks compared to Whites across time (race effect, p = 0.043 and p = 0.049, respectively). Very-low-frequency and low-frequency bands of heart rate variability, which are associated with sympathovagal balance and vasomotor tone, were 22.5% and 24.9% lower, respectively, in Blacks compared to Whites (race effect, p = 0.045 and p = 0.006, respectively). In conclusion, the preliminary findings of racial differences in blood pressure and autonomic recovery following supramaximal exercise warrant further investigations of tailored exercise prescriptions for Blacks and Whites.

Evaluation of pre-induction dynamic arterial elastance as an adjustable predictor of post-induction hypotension: A prospective observational study.

STUDY OBJECTIVE: Dynamic arterial elastance (Eadyn) has been suggested as a functional measure of arterial load. We aimed to evaluate whether pre-induction Eadyn can predict post-induction hypotension. DESIGN: Prospective observational study. PATIENTS: Adult patients undergoing general anesthesia with invasive and non-invasive arterial pressure monitoring systems. MEASUREMENTS: We collected invasive and non-invasive Eadyns (n = 38 in each), respectively. In both invasive and non-invasive Eadyns, pre-induction Eadyns were obtained during one-minute tidal and deep breathing in each patient before anesthetic induction. Post-induction hypotension was defined as a decrease of >30% in mean blood pressure from the baseline value or any absolute mean blood pressure value of <65 mmHg for 10 min after anesthetic induction. The predictabilities of Eadyns for the development of post-induction hypotension were tested using receiver-operating characteristic curve analysis. MAIN RESULTS: Invasive Eadyn during deep breathing showed significant predictability with an area under the curve (AUC) of 0.78 (95% Confidence interval [CI], 0.61-0.90, P = 0.001). But non-invasive Eadyn during tidal breathing (AUC = 0.66, 95% CI, 0.49-0.81, P = 0.096) and deep breathing (AUC = 0.53, 95% CI, 0.36-0.70, P = 0.75), and invasive Eadyn during tidal breathing (AUC = 0.66, 95% CI, 0.41-0.74, P = 0.095) failed to predict post-induction hypotension. CONCLUSION: In our study, invasive pre-induction Eadyn during deep breathing -could predict post-induction hypotension. Despite its invasiveness, future studies will be needed to evaluate the usefulness of Eadyn as a predictor of post-induction hypotension because it is an adjustable parameter.

Agreement between cardiac output measurements by pulse wave analysis using the Pressure Recording Analytical Method and transthoracic echocardiography in patients with veno-venous extracorporeal membrane oxygenation therapy: An observational method comparison.

BACKGROUND: Measuring cardiac output (CO) is important in patients treated with veno-venous extracorporeal membrane oxygenation (vvECMO) because vvECMO flow and CO need to be balanced. Uncalibrated pulse wave analysis with the Pressure Recording Analytical Method (PRAM) may be suitable to measure CO in patients with vvECMO therapy. OBJECTIVE: To assess the agreement between CO measured by PRAM (PRAM-CO; test method) and CO measured by transthoracic echocardiography (TTE-CO; reference method). DESIGN: A prospective observational method comparison study. SETTING: The ICU of a German university hospital between March and December 2021. PATIENTS: Thirty one adult patients with respiratory failure requiring vvECMO therapy: 29 of the 31 patients (94%) were treated for COVID-19 related respiratory failure. MAIN OUTCOME MEASURES: PRAM-CO and TTE-CO were measured simultaneously at two time points in each patient with at least 20 min between measurements. A radial or femoral arterial catheter-derived blood pressure waveform was used for PRAM-CO measurements. TTE-CO measurements were conducted using the pulsed wave Doppler-derived velocity time integral of the left ventricular outflow tract (LVOT) and the corresponding LVOT diameter. PRAM-CO and TTE-CO were compared using Bland-Altman analysis and the percentage error (PE). We defined a PE of <30% as clinically acceptable. RESULTS: Mean ±â€ŠSD PRAM-CO was 6.86 ±â€Š1.49 l min -1 and mean TTE-CO was 6.94 ±â€Š1.58 l min -1 . The mean of the differences between PRAM-CO and TTE-CO was 0.09 ±â€Š0.73 l min -1 with a lower 95% limit of agreement of -1.34 l min -1 and an upper 95% limit of agreement of 1.51 l min -1 . The PE was 21%. CONCLUSIONS: The agreement between PRAM-CO and TTE-CO is clinically acceptable in adult patients with vvECMO therapy.

Initial mean arterial blood pressure (MABP) measurement is a risk factor for mortality in hypertensive COVID-19 positive hospitalized patients.

BACKGROUND: Hypertension (HTN) is associated with severe COVID-19 infection; however, it remains unknown if the level of blood pressure (BP) predicts mortality. We tested whether the initial BP in the emergency department of hospitalized patients portends mortality in COVID-19 positive(+) patients. METHODS: Data from COVID-19(+) and negative (-) hospitalized patients at Stony Brook University Hospital from March to July 2020 were included. The initial mean arterial BPs (MABPs) were categorized into tertiles (T) of MABP (65-85 [T1], 86-97 [T2] and ≥98 [T3] mmHg). Differences were evaluated using univariable (t-tests, chi-squared) tests. Multivariable (MV) logistic regression analyses were computed to assess links between MABP and mortality in hypertensive COVID-19 patients. RESULTS: 1549 adults were diagnosed with COVID-19 (+) and 2577 tested negative (-). Mortality of COVID-19(+) was 4.4-fold greater than COVID-19(-) patients. Though HTN prevalance did not differ between COVID-19 groups, the presenting systolic BP, diastolic BP, and MABP were lower in the COVID-19(+) vs (-) cohort. When subjects were categorized into tertiles of MABP, T2 tertile of MABP had the lowest mortality and the T1 tertile of MABP had greatest mortality compared to T2; however, no difference in mortality was noted across tertiles of MABP in COVID-19 (-). MV analysis of COVID-19 (+) subjects exposed death as a risk factor for T1 MABP. Next, the mortality of those with a historic diagnosis of hypertension or normotension were studied. On MV analysis, T1 MABP, gender, age, and first respiratory rate correlated with mortality while lymphocyte count inversely correlated with death in hypertensive COVID-19 (+) patients while neither T1 nor T3 categories of MABP predicted death in non-hypertensives. CONCLUSIONS: Low-normal admitting MABP in COVID-19 (+) subjects with a historical diagnosis of HTN is associated with mortality and may assist in identifying those at greatest mortality risk.

Increased Physical Activity at School Benefits Arterial Blood Pressure in Children-A Prospective Follow-Up Cohort Study.

(1) Background: A sedentary lifestyle and low physical activity (PA) increase the risk of hypertension in children. The aim of this study was to assess the impact of increased PA at school by elevation of the number of compulsory physical education (PE) lessons on arterial blood pressure in children during a two-year follow-up. (2) Methods: Children (n = 245) born in 2007 attending a standard or elevated number of PE lessons in the school timetable (4 and 10 h a week, respectively) took part in the study. Blood pressure was measured starting from age approx. 10 to 12. (3) Results: Starting from a similar level, after 2 years, the percentage of children with normal blood pressure decreased in the standard-PE children from 83.25% to 78.03% but increased in the elevated-PE ones from 83.15% to 86.13%. The prevalence of both prehypertension and hypertension increased by one-third in the standard-PE children from 16.74% to 21.97% but decreased by one-sixth in the elevated-PE ones from 16.85% to 13.87%. The prevalence of hypertension itself increased by one-third in the standard-PE children from 9.82% to 13.12% but decreased in the elevated-PE ones by one-fifth from 9.60% to 7.75% (4) Conclusions: An increase in PA at school by the elevation of the number of PE lessons benefits children's arterial blood pressure. Early prevention of hypertension in children can be supported by an adequate number of PE lessons in the school timetable.

Implantable devices for heart failure monitoring.

Heart failure (HF) is associated with considerable morbidity and mortality. The increasing prevalence of HF and inpatient HF hospitalization has a considerable burden on healthcare cost and utilization. The recognition that hemodynamic changes in pulmonary artery pressure (PAP) and left atrial pressure precede the signs and symptoms of HF has led to interest in hemodynamic guided HF therapy as an approach to allow earlier intervention during a heart failure decompensation. Remote patient monitoring (RPM) utilizing telecommunication, cardiac implantable electronic device parameters and implantable hemodynamic monitors (IHM) have largely failed to demonstrate favorable outcomes in multicenter trials. However, one positive randomized clinical trial testing the CardioMEMS device (followed by Food and Drug Administration approval) has generated renewed interest in PAP monitoring in the HF population to decrease hospitalization and improve quality of life. The COVID-19 pandemic has also stirred a resurgence in the utilization of telehealth to which RPM using IHM may be complementary. The cost effectiveness of these monitors continues to be a matter of debate. Future iterations of devices aim to be smaller, less burdensome for the patient, less dependent on patient compliance, and less cumbersome for health care providers with the integration of artificial intelligence coupled with sophisticated data management and interpretation tools. Currently, use of IHM may be considered in advanced heart failure patients with the support of structured programs.

Intubated COVID-19 predictive (ICOP) score for early mortality after intubation in patients with COVID-19.

Patients with coronavirus disease 2019 (COVID-19) can have increased risk of mortality shortly after intubation. The aim of this study is to develop a model using predictors of early mortality after intubation from COVID-19. A retrospective study of 1945 intubated patients with COVID-19 admitted to 12 Northwell hospitals in the greater New York City area was performed. Logistic regression model using backward selection was applied. This study evaluated predictors of 14-day mortality after intubation for COVID-19 patients. The predictors of mortality within 14 days after intubation included older age, history of chronic kidney disease, lower mean arterial pressure or increased dose of required vasopressors, higher urea nitrogen level, higher ferritin, higher oxygen index, and abnormal pH levels. We developed and externally validated an intubated COVID-19 predictive score (ICOP). The area under the receiver operating characteristic curve was 0.75 (95% CI 0.73-0.78) in the derivation cohort and 0.71 (95% CI 0.67-0.75) in the validation cohort; both were significantly greater than corresponding values for sequential organ failure assessment (SOFA) or CURB-65 scores. The externally validated predictive score may help clinicians estimate early mortality risk after intubation and provide guidance for deciding the most effective patient therapies.

Intra-aneurysmal pressure changes during stent-assisted coiling.

We aimed to examine aneurysm hemodynamics with intra-saccular pressure measurement, and compare the effects of coiling, stenting and stent-assisted coiling in proximal segments of intracranial circulation. A cohort of 45 patients underwent elective endovascular coil embolization (with or without stent) for intracranial aneurysm at our department. Arterial pressure transducer was used for all measurements. It was attached to proximal end of the microcatheter. Measurements were taken in the parent artery before and after embolization, at the aneurysm dome before embolization, after stent implantation, and after embolization. Stent-assisted coiling was performed with 4 different stents: LVIS and LVIS Jr (Microvention, Tustin, CA, USA), Leo (Balt, Montmorency, France), Barrel VRD (Medtronic/ Covidien, Irvine, CA, USA). Presence of the stent showed significant reverse correlation with intra-aneurysmal pressure-both systolic and diastolic-after its implantation (r = -0.70 and r = -0.75, respectively), which was further supported by correlations with stent cell size-r = 0.72 and r = 0.71, respectively (P<0.05). Stent implantation resulted in significant decrease in diastolic intra-aneurysmal pressure (p = 0.046). Systolic or mean intra-aneurysmal pressure did not differ significantly. Embolization did not significantly change the intra-aneurysmal pressure in matched pairs, regardless of the use of stent (p>0.05). In conclusion, low-profile braided stents show a potential to divert blood flow, there was significant decrease in diastolic pressure after stent placement. Flow-diverting properties were related to stent porosity. Coiling does not significantly change the intra-aneurysmal pressure, regardless of packing density.

Lower blood pH as a strong prognostic factor for fatal outcomes in critically ill COVID-19 patients at an intensive care unit: A multivariable analysis.

BACKGROUND: Data of critically ill COVID-19 patients are being evaluated worldwide, not only to understand the various aspects of the disease and to refine treatment strategies but also to improve clinical decision-making. For clinical decision-making in particular, prognostic factors of a lethal course of the disease would be highly relevant. METHODS: In this retrospective cohort study, we analyzed the first 59 adult critically ill Covid-19 patients treated in one of the intensive care units of the University Medical Center Regensburg, Germany. Using uni- and multivariable regression models, we extracted a set of parameters that allowed for prognosing in-hospital mortality. RESULTS: Within the cohort, 19 patients died (mortality 32.2%). Blood pH value, mean arterial pressure, base excess, troponin, and procalcitonin were identified as highly significant prognostic factors of in-hospital mortality. However, no significant differences were found for other parameters expected to be relevant prognostic factors, like low arterial partial pressure of oxygen or high lactate levels. In the multivariable logistic regression analysis, the pH value and the mean arterial pressure turned out to be the most influential prognostic factors for a lethal course.

Angiotensin II Administration in Patients With COVID-19 Shock.

PURPOSE: To understand the hemodynamic effect of angiotensin II as a vasopressor in patients with shock secondary to COVID-19 infection. METHODS: A retrospective analysis was performed on all patients at a single center with COVID-19 infection and shock who were treated with angiotensin II. The hemodynamic response to angiotensin II was estimated by recording the mean arterial pressure, norepinephrine equivalent dose (NED) and urine output. RESULTS: Ten patients with COVID-19 related shock were treated with angiotensin II. Over the initial 6 hours, the average the NED decreased by 30.4% (from 64.6 to 44 µg/min) without a significant change in the mean arterial pressure (0.7% decrease). Six patients experienced at least a 25% reduction in NED by 6 hours, and 2 experienced at least a 50% reduction. CONCLUSIONS: On average, the hemodynamic response to angiotensin II in COVID-19 related shock was favorable. Two patients had a marked rapid improvement. Given the relationship of SARS-CoV-2 with the renin-angiotensin-aldosterone system, further evaluation of angiotensin II for the treatment of COVID-19 related shock is warranted.

Automatic real-time analysis and interpretation of arterial blood gas sample for Point-of-care testing: Clinical validation.

BACKGROUND: Point-of-care arterial blood gas (ABG) is a blood measurement test and a useful diagnostic tool that assists with treatment and therefore improves clinical outcomes. However, numerically reported test results make rapid interpretation difficult or open to interpretation. The arterial blood gas algorithm (ABG-a) is a new digital diagnostics solution that can provide clinicians with real-time interpretation of preliminary data on safety features, oxygenation, acid-base disturbances and renal profile. The main aim of this study was to clinically validate the algorithm against senior experienced clinicians, for acid-base interpretation, in a clinical context. METHODS: We conducted a prospective international multicentre observational cross-sectional study. 346 sample sets and 64 inpatients eligible for ABG met strict sampling criteria. Agreement was evaluated using Cohen's kappa index, diagnostic accuracy was evaluated with sensitivity, specificity, efficiency or global accuracy and positive predictive values (PPV) and negative predictive values (NPV) for the prevalence in the study population. RESULTS: The concordance rates between the interpretations of the clinicians and the ABG-a for acid-base disorders were an observed global agreement of 84,3% with a Cohen's kappa coefficient 0.81; 95% CI 0.77 to 0.86; p < 0.001. For detecting accuracy normal acid-base status the algorithm has a sensitivity of 90.0% (95% CI 79.9 to 95.3), a specificity 97.2% (95% CI 94.5 to 98.6) and a global accuracy of 95.9% (95% CI 93.3 to 97.6). For the four simple acid-base disorders, respiratory alkalosis: sensitivity of 91.2 (77.0 to 97.0), a specificity 100.0 (98.8 to 100.0) and global accuracy of 99.1 (97.5 to 99.7); respiratory acidosis: sensitivity of 61.1 (38.6 to 79.7), a specificity of 100.0 (98.8 to 100.0) and global accuracy of 98.0 (95.9 to 99.0); metabolic acidosis: sensitivity of 75.8 (59.0 to 87.2), a specificity of 99.7 (98.2 to 99.9) and a global accuracy of 97.4 (95.1 to 98.6); metabolic alkalosis sensitivity of 72.2 (56.0 to 84.2), a specificity of 95.5 (92.5 to 97.3) and a global accuracy of 93.0 (88.8 to 95.3); the four complex acid-base disorders, respiratory and metabolic alkalosis, respiratory and metabolic acidosis, respiratory alkalosis and metabolic acidosis, respiratory acidosis and metabolic alkalosis, the sensitivity, specificity and global accuracy was also high. For normal acid-base status the algorithm has PPV 87.1 (95% CI 76.6 to 93.3) %, and NPV 97.9 (95% CI 95.4 to 99.0) for a prevalence of 17.4 (95% CI 13.8 to 21.8). For the four-simple acid-base disorders and the four complex acid-base disorders the PPV and NPV were also statistically significant. CONCLUSIONS: The ABG-a showed very high agreement and diagnostic accuracy with experienced senior clinicians in the acid-base disorders in a clinical context. The method also provides refinement and deep complex analysis at the point-of-care that a clinician could have at the bedside on a day-to-day basis. The ABG-a method could also have the potential to reduce human errors by checking for imminent life-threatening situations, analysing the internal consistency of the results, the oxygenation and renal status of the patient.

Clinical Characteristics and Outcomes of Patients with COVID-19 Infection: The Results of the SARS-RAS Study of the Italian Society of Hypertension.

The COVID-19 infection has rapidly spread around the world and a second wave is sweeping in many countries. Different clinical and epidemiological aspects characterize the disease and their understanding is necessary to better face the management of the pandemic in progress. The Italian society of arterial hypertension with the SARS-RAS study has contributed significantly to the knowledge of the interaction between inhibition of the renin-angiotensin system and COVID-19 infection. Furthermore, the study results help to understand some of the main aspects related to mortality and morbidity deriving from the infection through a multicentre analysis throughout the national territory.

High lipasemia is frequent in Covid-19 associated acute respiratory distress syndrome.

BACKGROUND: Covid-19 is a rapidly spreading viral disease that can cause severe acute respiratory distress syndrome (ARDS). Besides the lungs it can also affect other organs like the heart or the liver. Whether there is a pancreatic manifestation as well is currently unclear. METHODS: and aims: We prospectively collected patient information of patients with Covid-19 associated ARDS in a registry (COvid Registry REChts der Isar intensive care Trial - CORRECT) and analyzed this patient cohort for signs of acute pancreatitis (e.g. lipase activity >3 times the upper limit). RESULTS: 12/38 (31.6%) patients with Covid-19 associated ARDS had a serum lipase activity >180 U/l. Median lipase activity was 422 U/l (186-1127). No patient showed typical findings of acute pancreatitis on imaging studies. On hemodynamic monitoring no patient had signs of intravascular fluid demand regarding MAP, GEDVI and therapy with vasopressors. To avoid worsening respiratory function no treatment with crystalloids was initiated. Lipasemia was not explained by gastroenteritis or renal insufficiency, occurred before as well as after viral clearance and 16.1 ± 6.0 days after the first symptoms. No patient developed severe acute pancreatitis during the follow up period of 35.8 ± 8.3 days. CONCLUSION: High lipasemia without typical signs of acute pancreatitis is a frequent finding in severe Covid-19 associated ARDS. Considering the markedly high levels of serum lipase activity, we think impaired microcirculation in severely ill patients can explain this finding rather than extra-pancreatic co-morbidities (UTN: DRKS00021612).

A novel severity score to predict inpatient mortality in COVID-19 patients.

COVID-19 is commonly mild and self-limiting, but in a considerable portion of patients the disease is severe and fatal. Determining which patients are at high risk of severe illness or mortality is essential for appropriate clinical decision making. We propose a novel severity score specifically for COVID-19 to help predict disease severity and mortality. 4711 patients with confirmed SARS-CoV-2 infection were included. We derived a risk model using the first half of the cohort (n = 2355 patients) by logistic regression and bootstrapping methods. The discriminative power of the risk model was assessed by calculating the area under the receiver operating characteristic curves (AUC). The severity score was validated in a second half of 2356 patients. Mortality incidence was 26.4% in the derivation cohort and 22.4% in the validation cohort. A COVID-19 severity score ranging from 0 to 10, consisting of age, oxygen saturation, mean arterial pressure, blood urea nitrogen, C-Reactive protein, and the international normalized ratio was developed. A ROC curve analysis was performed in the derivation cohort achieved an AUC of 0.824 (95% CI 0.814-0.851) and an AUC of 0.798 (95% CI 0.789-0.818) in the validation cohort. Furthermore, based on the risk categorization the probability of mortality was 11.8%, 39% and 78% for patient with low (0-3), moderate (4-6) and high (7-10) COVID-19 severity score. This developed and validated novel COVID-19 severity score will aid physicians in predicting mortality during surge periods.

Persistent severe acute respiratory distress syndrome for the prognostic enrichment of trials.

BACKGROUND: Acute respiratory distress syndrome (ARDS) is heterogeneous. As an indication of the heterogeneity of ARDS, there are patients whose syndrome improves rapidly (i.e., within 24 hours), others whose hypoxemia improves gradually and still others whose severe hypoxemia persists for several days. The latter group of patients with persistent severe ARDS poses challenges to clinicians. We attempted to assess the baseline characteristics and outcomes of persistent severe ARDS and to identify which variables are useful to predict it. METHODS: A secondary analysis of patient-level data from the ALTA, EDEN and SAILS ARDSNet clinical trials was conducted. We defined persistent severe ARDS as a partial pressure of arterial oxygen to fraction of inspired oxygen ratio (PaO2:FiO2) of equal to or less than 100 mmHg on the second study day following enrollment. Regularized logistic regression with an L1 penalty [Least Absolute Shrinkage and Selection Operator (LASSO)] techniques were used to identify predictive variables of persistent severe ARDS. RESULTS: Of the 1531 individuals with ARDS alive on the second study day after enrollment, 232 (15%) had persistent severe ARDS. Of the latter, 100 (43%) individuals had mild or moderate hypoxemia at baseline. Usage of vasopressors was greater [144/232 (62%) versus 623/1299 (48%); p<0.001] and baseline severity of illness was higher in patients with versus without persistent severe ARDS. Mortality at 60 days [95/232 (41%) versus 233/1299 (18%); p<0.001] was higher, and ventilator-free (p<0.001), intensive care unit-free [0 (0-14) versus 19 (7-23); p<0.001] and non-pulmonary organ failure-free [3 (0-21) versus 20 (1-26); p<0.001] days were fewer in patients with versus without persistent severe ARDS. PaO2:FiO2, FiO2, hepatic failure and positive end-expiratory pressure at enrollment were useful predictive variables. CONCLUSIONS: Patients with persistent severe ARDS have distinct baseline characteristics and poor prognosis. Identifying such patients at enrollment may be useful for the prognostic enrichment of trials.

End-Tidal-to-Arterial PCO2 Ratio as Signifier for Physiologic Dead-Space Ratio and Oxygenation Dysfunction in Acute Respiratory Distress Syndrome.

BACKGROUND: The ratio of end-tidal CO2 pressure to arterial partial pressure of CO2 ([Formula: see text]) was recently suggested for monitoring pulmonary gas exchange in patients with ARDS associated with COVID-19, yet no evidence was offered supporting that claim. Therefore, we evaluated whether [Formula: see text] might be relevant in assessing ARDS not associated with COVID-19. METHODS: We evaluated the correspondence between [Formula: see text] and the ratio of dead space to tidal volume (VD/VT) measured in 561 subjects with ARDS from a previous study in whom [Formula: see text] data were also available. Subjects also were analyzed according to 4 ranges of [Formula: see text] representing increasing illness severity (≥ 0.80, 0.6-0.79, 0.50-0.59, and < 0.50). Correlation was assessed by either Pearson or Spearman tests, grouped comparisons were assessed using either ANOVA or Kruskal-Wallis tests and dichotomous variables assessed by Fisher Exact tests. Normally distributed data are presented as mean and standard deviation(SD) and non-normal data are presented as median and inter-quartile range (IQR). Overall mortality risk was assessed with multivariate logistic regression. Alpha was set at 0.05. RESULTS: [Formula: see text] correlated strongly with VD/VT (r = -0.87 [95% CI -0.89 to -0.85], P < .001). Decreasing [Formula: see text] was associated with increased VD/VT and hospital mortality between all groups. In the univariate analysis, for every 0.01 decrease in [Formula: see text], mortality risk increased by ∼1% (odds ratio 0.009, 95% CI 0.003-0.029, P < .001) and maintained a strong independent association with mortality risk when adjusted for other variables (odds ratio 0.19, 95% CI 0.04-0.91, P = .039). [Formula: see text] < 0.50 was characterized by very high mean ± SD value for VD/VT (0.82 ± 0.05, P < .001) and high hospital mortality (70%). CONCLUSIONS: Using [Formula: see text] as a surrogate for VD/VT may be a useful and practical measurement for both management and ongoing research into the nature of ARDS.