Lung Ultrasound Prediction Model for Acute Respiratory Distress Syndrome: A Multicenter Prospective Observational Study.

Rationale: Lung ultrasound (LUS) is a promising tool for diagnosis of acute respiratory distress syndrome (ARDS), but adequately sized studies with external validation are lacking. Objectives: To develop and validate a data-driven LUS score for diagnosis of ARDS and compare its performance with that of chest radiography (CXR). Methods: This multicenter prospective observational study included invasively ventilated ICU patients who were divided into a derivation cohort and a validation cohort. Three raters scored ARDS according to the Berlin criteria, resulting in a classification of "certain no ARDS," or "certain ARDS" when experts agreed or "uncertain ARDS" when evaluations conflicted. Uncertain cases were classified in a consensus meeting. Results of a 12-region LUS exam were used in a logistic regression model to develop the LUS-ARDS score. Measurements and Main Results: Three hundred twenty-four (16% certain ARDS) and 129 (34% certain ARDS) patients were included in the derivation cohort and the validation cohort, respectively. With an ARDS diagnosis by the expert panel as the reference test, the LUS-ARDS score, including the left and right LUS aeration scores and anterolateral pleural line abnormalities, had an area under the receiver operating characteristic (ROC) curve of 0.90 (95% confidence interval [CI], 0.85-0.95) in certain patients of the derivation cohort and 0.80 (95% CI, 0.72-0.87) in all patients of the validation cohort. Within patients who had imaging-gold standard chest computed tomography available, diagnostic accuracy of eight independent CXR readers followed the ROC curve of the LUS-ARDS score. Conclusions: The LUS-ARDS score can be used to accurately diagnose ARDS also after external validation. The LUS-ARDS score may be a useful adjunct to a diagnosis of ARDS after further validation, as it showed performance comparable with that of the current practice with experienced CXR readers but more objectifiable diagnostic accuracy at each cutoff.

Hyperoxia does not affect oxygen delivery in healthy volunteers while causing a decrease in sublingual perfusion.

OBJECTIVE: To determine the human dose-response relationship between a stepwise increase in arterial oxygen tension and its associated changes in DO2 and sublingual microcirculatory perfusion. METHODS: Fifteen healthy volunteers breathed increasing oxygen fractions for 10 minutes to reach arterial oxygen tensions of baseline (breathing air), 20, 40, 60 kPa, and max kPa (breathing oxygen). Systemic hemodynamics were measured continuously by the volume-clamp method. At the end of each period, the sublingual microcirculation was assessed by SDF. RESULTS: Systemic DO2 was unchanged throughout the study (Pslope  = .8). PVD decreased in a sigmoidal fashion (max -15% while breathing oxygen, SD18, Pslope  = .001). CI decreased linearly (max -10%, SD10, Pslope  < .001) due to a reduction in HR (max -10%, SD7, Pslope  = .009). There were no changes in stroke volume or MAP. Most changes became apparent above an arterial oxygen tension of 20 kPa. CONCLUSIONS: In healthy volunteers, supraphysiological arterial oxygen tensions have no effect on systemic DO2 . Sublingual microcirculatory PVD decreased in a dose-dependent fashion. All hemodynamic changes appear negligible up to an arterial oxygen tension of 20 kPa.

Focus on focus: lack of coherence between systemic and microvascular indices of oedema formation.

BACKGROUND: Fluid therapy remains a cornerstone of therapy in shock states. However, fluid overloading ultimately results in oedema formation which is related to excess morbidity and mortality. Handheld microscopes are now frequently used to study the sublingual microcirculation. As a corollary, these devices measure focal distance, or surface to capillary distance. Physiologically, this could represent a microvascular index of oedema formation and could have the potential to guide fluid therapy. This potential tool should be investigated, especially given the frequently reported lack of coherence between systemic and microvascular parameters in the critically ill. Therefore, we set out to assess the correlation between microvascular focal distance and systemic indices of oedema formation, specifically fluid balance and weight gain. METHODS: Following ex vivo testing of focal distance measurement reliability, we conducted a prospective observational cohort study in patients admitted to the intensive care unit of our university teaching hospital. We determined surface to capillary distance using sidestream dark field (SDF) and incident dark field (IDF) imaging by assessing the focal distance point or object distance range at which a sharp recording could be made. Measurements were performed in post-cardiac surgery patients and in patients following emergency admission at two time points separated by at least several hours. Data on fluid balance, weight and weight gain were collected simultaneously. RESULTS: Sixty patients were included. The focal setting, focus point for SDF and the object distance range for IDF did not differ significantly between time points. Focus was not correlated with difference in fluid balance or weight gain. CONCLUSIONS: There is a lack of coherence between surface to capillary distance as determined by SDF or IDF imaging and fluid balance or weight gain. Thus, focal distance as a microvascular index of oedema formation cannot currently be used as a proxy for systemic indices of oedema formation. However, given the lack of coherence, further research should determine whether focal distance may provide better guidance for fluid therapy than traditional markers of overzealous fluid administration. RESULTS: Sixty patients were included. Focal setting, focus point for SDF and an object distance range for IDF did not differ significantly between time points. Focus was not correlated with difference in fluid balance or weight gain. CONCLUSIONS: There is a lack of coherence between surface to capillary distance as determined by SDF or IDF imaging and fluid balance or weight gain. Thus, focal distance as a microvascular index of edema formation cannot currently be used as a proxy for systemic indices of edema formation. However, given the lack of coherence, further research should determine whether focal distance may provide better guidance for fluid therapy than traditional markers of overzealous fluid administration.

Moderate hyperoxic versus near-physiological oxygen targets during and after coronary artery bypass surgery: a randomised controlled trial.

BACKGROUND: The safety of perioperative hyperoxia is currently unclear. Previous studies in patients undergoing coronary artery bypass surgery suggest reduced myocardial damage when avoiding extreme perioperative hyperoxia (>400 mmHg). In this study we investigated whether an oxygenation strategy from moderate hyperoxia to a near-physiological oxygen tension reduces myocardial damage and improves haemodynamics, organ dysfunction and oxidative stress. METHODS: This was a single-blind, single-centre, open-label, randomised controlled trial in patients undergoing elective coronary artery bypass surgery. Fifty patients were randomised to a partial pressure of oxygen in arterial blood (PaO2) target of 200-220 mmHg during cardiopulmonary bypass and 130-150 mmHg during intensive care unit (ICU) admission (control group) versus lower targets of 130-150 mmHg during cardiopulmonary bypass and 80-100 mmHg at the ICU (conservative group). Primary outcome was myocardial injury (CK-MB and Troponin-T) at ICU admission and 2, 6 and 12 hours thereafter. RESULTS: Weighted PaO2 during cardiopulmonary bypass was 220 mmHg (interquartile range (IQR) 211-233) vs. 157 (151-162) in the control and conservative group, respectively (P < 0.0001). During ICU admission, weighted PaO2 was 107 mmHg (86-141) vs. 90 (84-98) (P = 0.03), respectively. Area under the curve of CK-MB was median 23.5 µg/L/h (IQR 18.4-28.1) vs. 21.5 (15.8-26.6) (P = 0.35) and 0.30 µg/L/h (0.25-0.44) vs. 0.39 (0.24-0.43) (P = 0.81) for Troponin-T. Cardiac index, systemic vascular resistance index, creatinine, lactate and F2-isoprostane levels were not different between groups. CONCLUSIONS: Compared to moderate hyperoxia, a near-physiological oxygen strategy does not reduce myocardial damage in patients undergoing coronary artery bypass surgery. Conservative oxygen administration was not associated with increased lactate levels or hypoxic events. TRIAL REGISTRATION: Netherlands Trial Registry NTR4375, registered on 30 January 2014.

Ventilator-derived carbon dioxide production to assess energy expenditure in critically ill patients: proof of concept.

INTRODUCTION: Measurement of energy expenditure (EE) is recommended to guide nutrition in critically ill patients. Availability of a gold standard indirect calorimetry is limited, and continuous measurement is unfeasible. Equations used to predict EE are inaccurate. The purpose of this study was to provide proof of concept that EE can be accurately assessed on the basis of ventilator-derived carbon dioxide production (VCO2) and to determine whether this method is more accurate than frequently used predictive equations. METHODS: In 84 mechanically ventilated critically ill patients, we performed 24-h indirect calorimetry to obtain a gold standard EE. Simultaneously, we collected 24-h ventilator-derived VCO2, extracted the respiratory quotient of the administered nutrition, and calculated EE with a rewritten Weir formula. Bias, precision, and accuracy and inaccuracy rates were determined and compared with four predictive equations: the Harris-Benedict, Faisy, and Penn State University equations and the European Society for Clinical Nutrition and Metabolism (ESPEN) guideline equation of 25 kcal/kg/day. RESULTS: Mean 24-h indirect calorimetry EE was 1823 ± 408 kcal. EE from ventilator-derived VCO2 was accurate (bias +141 ± 153 kcal/24 h; 7.7 % of gold standard) and more precise than the predictive equations (limits of agreement -166 to +447 kcal/24 h). The 10 % and 15 % accuracy rates were 61 % and 76 %, respectively, which were significantly higher than those of the Harris-Benedict, Faisy, and ESPEN guideline equations. Large errors of more than 30 % inaccuracy did not occur with EE derived from ventilator-derived VCO2. This 30 % inaccuracy rate was significantly lower than that of the predictive equations. CONCLUSIONS: In critically ill mechanically ventilated patients, assessment of EE based on ventilator-derived VCO2 is accurate and more precise than frequently used predictive equations. It allows for continuous monitoring and is the best alternative to indirect calorimetry.

Using Nursing Activities Score to Assess Nursing Workload on a Medium Care Unit.

BACKGROUND: The medium care unit (MCU) or "stepdown" unit is an increasingly important, but understudied care environment. With an aging population and more patients with complex multiple diseases, many patients often require a higher level of inpatient care even when full intensive care is not indicated. However, the nurse-to-patient ratio required on a MCU is neither well defined nor clear whether this ratio should be adjusted per shift. The Nursing Activities Score (NAS) is an effective instrument for measuring nursing workload in the intensive care unit (ICU) but has not been used in an MCU. The aim of this study was to measure the nursing workload per 8-hour shift on an MCU using the NAS and compare it with the NAS from an ICU in the same hospital. We also compared the NAS between groups of patients with different admission sources. METHODS: The NAS was prospectively measured per patient per shift for 2 months in a 9-bed tertiary referral university hospital MCU and during a similar period in an ICU in the same hospital. RESULTS: The mean NAS per patient did not differ between day (7:30 AM to 4:00 PM) and evening (3:00 PM to 11:30 PM) shifts, but the NAS was significantly lower during the night shift (11:00 PM to 8:00 AM) than during the day (P < 0.0001) and evening (P < 0.0001) shifts. The mean NASs in the ICU for day and night shifts were significantly lower than the scores in the MCU (P = 0.0056 and P < 0.0001, respectively), but NAS during the evening shift did not differ between the ICU and the MCU. The mean NAS for patients admitted to the MCU from the accident and emergency department was significantly higher than for those admitted from the ICU (P = 0.002), recovery (P = 0.002), and general ward (P < 0.0001). Patients on the MCU had a NAS comparable with that of ICU patients. CONCLUSIONS: In our university hospital, NAS was higher during the day and evening hours and lower at night. We also found that patients from accident and emergency had a higher NAS than those admitted to the MCU from other locations. NAS in the MCU was not lower than the NAS in the ICU. Because of its ability to discriminate between day and evening workloads and between patients from different sources, the NAS may assist MCU managers in assessing staffing needs.