Validation of a novel system to assess end-expiratory lung volume and alveolar recruitment in an ARDS model

Abstract Background Personalizing mechanical ventilation requires the development of reliable bedside monitoring techniques. The multiple-breaths nitrogen washin–washout (MBNW) technique is currently available to measure end-expiratory lung volume (EELVMBNW), but the precision of the technique may be poor, with percentage errors ranging from 28 to 57%. The primary aim of the study was to evaluate the reliability of a novel MBNW bedside system using fast mainstream sensors to assess EELV in an experimental acute respiratory distress syndrome (ARDS) model, using computed tomography (CT) as the gold standard. The secondary aims of the study were: (1) to evaluate trending ability of the novel system to assess EELV; (2) to evaluate the reliability of estimated alveolar recruitment induced by positive end-expiratory pressure (PEEP) changes computed from EELVMBNW, using CT as the gold standard. Results Seven pigs were studied in 6 experimental conditions: at baseline, after experimental ARDS and during a decremental PEEP trial at PEEP 16, 12, 6 and 2 cmH2O. EELV was computed at each PEEP step by both the MBNW technique (EELVMBNW) and CT (EELVCT). Repeatability was assessed by performing replicate measurements. Alveolar recruitment between two consecutive PEEP levels after lung injury was measured with CT (VrecCT), and computed from EELV measurements (VrecMBNW) as ΔEELV minus the product of ΔPEEP by static compliance. EELVMBNW and EELVCT were significantly correlated (R2 = 0.97). An acceptable non-constant bias between methods was identified, slightly decreasing toward more negative values as EELV increased. The conversion equation between EELVMBNW and EELVCT was: EELVMBNW = 0.92 × EELVCT + 36. The 95% prediction interval of the bias amounted to ± 86 mL and the percentage error between both methods amounted to 13.7%. The median least significant change between repeated measurements amounted to 8% [CI95%: 4–10%]. EELVMBNW adequately tracked EELVCT changes over time (concordance rate amounting to 100% [CI95%: 87%–100%] and angular bias amounting to − 2° ± 10°). VrecMBNW and VrecCT were significantly correlated (R2 = 0.92). A non-constant bias between methods was identified, slightly increasing toward more positive values as Vrec increased. Conclusions We report a new bedside MBNW technique that reliably assesses EELV in an experimental ARDS model with high precision and excellent trending ability.

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Assessment of the Adequacy of Gauge Repeatability and Reproducibility Study Using a Monte Carlo Simulation

Mathematical Problems in Engineering ◽

10.1155/2017/7237486 ◽

2017 ◽

Vol 2017 ◽

pp. 1-15 ◽

Cited By ~ 1

Author(s):

Chunghun Ha ◽

David S. Kim ◽

SeJoon Park

Keyword(s):

Monte Carlo Simulation ◽

Monte Carlo ◽

System Analysis ◽

Performance Metrics ◽

Repeated Measurements ◽

Percentage Error ◽

Nested Design ◽

Reproducibility Study ◽

Measurement System Analysis ◽

Repeatability And Reproducibility

ANOVA gauge repeatability and reproducibility study is the most popular tool for measurement system analysis. Two experimental designs can be applied depending on the durability of the objects. If repeated measurements are possible or sufficient homogeneous nonrepeatable samples are available, crossed design is appropriate; otherwise, nested design should be used. In this paper, we investigated the adequacy of ANOVA gauge repeatability and reproducibility study from the perspective of practitioners. We proposed a Monte Carlo simulation that is close to the realistic procedure to evaluate the adequacy of both structures. During the evaluation, we considered the average performance metrics, percentage of correct decision, histogram shape, and symmetric mean absolute percentage error for the four popular performance metrics, namely, % Study Variation, % Contribution, % Tolerance, and the number of distinct categories. The experimental results show that the nested design fails to judge the precision of the gauge while the crossed design succeeds.

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Alveolar pressure and lung volume as determinants of net transvascular fluid filtration

Journal of Applied Physiology ◽

10.1152/jappl.1977.42.4.476 ◽

1977 ◽

Vol 42 (4) ◽

pp. 476-482 ◽

Cited By ~ 35

Author(s):

G. Bo ◽

A. Hauge ◽

G. Nicolaysen

Keyword(s):

Lung Volume ◽

Continuous Monitoring ◽

Interstitial Fluid ◽

Positive Airway Pressure ◽

Fluid Pressure ◽

Alveolar Pressure ◽

Experimental Conditions ◽

Fluid Filtration ◽

Pulmonary Arterial ◽

Relative Change

We have investigated the influence of changes in alveolar pressure (PAlv) and in lung volume on the net transvascular fluid filtration rate (FFR). The preparation was isolated, perfused zone III rabbit lungs. In observation periods the outflow pressure was kept constant at a level generally causing net filtration. All pressures were measured relative to atmospheric. FFR was measured by continuous monitoring of preparation weight. Elevation of Palv at constant lung volume caused reversible reductions in FFR, also at constant capillary hydrostatic pressure (Pa-V less than 2 Torr). Increases in lung volume at constant PAlv caused reversible increases in FFR. When both PAlv and Ptp were increased a reduction in FFR was seen in the majority of cases. We conclude that at constant pulmonary arterial pressure, the size and the direction of the influence of positive airway pressure on FFR depend on the relative change in lung volume and in alveolar pressure per se. Under the present experimental conditions a rise in PAlv will be transmitted to interstitial fluid pressure and affect the transvascular fluid balance.

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Reproducibility and Validity of the 10-Meter Shuttle Ride Test in Wheelchair-Using Children and Adolescents With Cerebral Palsy

Physical Therapy ◽

10.2522/ptj.20120513 ◽

2013 ◽

Vol 93 (7) ◽

pp. 967-974 ◽

Cited By ~ 29

Author(s):

Olaf Verschuren ◽

Maremka Zwinkels ◽

Marjolijn Ketelaar ◽

Femke Reijnders-van Son ◽

Tim Takken

Keyword(s):

Cerebral Palsy ◽

Cardiorespiratory Fitness ◽

Gold Standard ◽

Pearson Correlation ◽

Intraclass Correlation ◽

Correlation Coefficients ◽

Peak Oxygen Uptake ◽

Repeated Measurements ◽

Manual Wheelchair ◽

Intraclass Correlation Coefficients

BackgroundFor children with cerebral palsy (CP) who are able to walk or run, the 10-m shuttle run test is currently the test of choice to assess cardiorespiratory fitness. This test, however, has not yet been examined in wheelchair-using youth with CP.ObjectiveThe purpose of this study was to investigate the test-retest reproducibility and validity of the 10-m shuttle ride test (SRiT) in youth with CP.DesignRepeated measurements of the SRiT were obtained.MethodsTwenty-three individuals with spastic CP (18 boys, 5 girls; mean age=13.3 years, SD=3.6 years) using a manual wheelchair for at least part of the day participated in this study. During the study, all participants performed one graded arm exercise test (GAET) and 2 identical SRiTs within 2 weeks. Peak oxygen uptake (V̇o2peak), peak heart rate (HRpeak), and respiratory exchange ratio (RER) were recorded. Intraclass correlation coefficients (2,1), the smallest detectable difference, and the limits of agreement (LOA) were calculated. The association between the results of the SRiT and GAET was tested using Pearson correlation coefficients.ResultsIntraclass correlation coefficients (.99, 95% confidence interval=.98–1.00) for all variables indicated highly acceptable reproducibility. The LOA analysis revealed satisfactory levels of agreement. The SRiT variables demonstrated strong, significant positive correlations for V̇o2peak values obtained during the SRiT and the GAET (r=.84, P<.01).LimitationsAlthough the GAET is considered the gold standard, the cardiorespiratory demand during the GAET was significantly lower compared with during the SRiT. Future studies should determine whether the GAET can still be accepted as the gold standard for upper-extremity exercise.ConclusionsThe SRiT is a reproducible and valid test for measuring cardiorespiratory fitness in youth with spastic CP who self-propel a manual wheelchair.

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Preemptive Alveolar Recruitment Maneuver Followed by PEEP in Obese Patients Undergoing Laparoscopic Gastric Banding. Does it make a Difference? A Randomized Controlled Clinical Study

The Open Anesthesia Journal ◽

10.2174/2589645801913010031 ◽

2019 ◽

Vol 13 (1) ◽

pp. 31-39

Author(s):

Sherif A. Elokda ◽

Hanan M. Farag

Keyword(s):

Gastric Banding ◽

Lung Volume ◽

Respiratory Mechanics ◽

Recruitment Maneuver ◽

Laparoscopic Gastric Banding ◽

Alveolar Recruitment ◽

Controlled Study ◽

Obese Patients ◽

Alveolar Recruitment Maneuver ◽

Standard Ventilation

Background: Impaired respiratory functions during general anesthesia are commonly caused by lung atelectasis more in morbidly obese patients. This occurs more frequently with laparoscopic surgery due to trendelenburg position and pneumoperitoneum. Preemptive recruitment maneuver + PEEP results in the prevention of these changes. Aim: To quantitate the effects of RM and PEEP on intraoperative hypoxemia and respiratory mechanics during laparoscopic gastric banding in obese patients. Study Design: A randomized, double-blinded, controlled study. Method and Materials: Fifty adults ASA I-II, BMI (40-50 kg/m2) for elective laparoscopic gastric banding were randomized into, groups C, and RM, 25 patients each. Group C patients received standard ventilation, VT 6 ml/kg, I: E ratio 1: 2 PEEP 5 cm H2O, and respiratory rate 10-12 breaths/ min. RM patients received standard ventilation with one alveolar recruitment maneuver after mechanical ventilation with PEEP of 15 cm H2O till the end of the surgery. Heart rate, mean blood pressure, respiratory mechanical parameters: peak airway pressure, plateau pressure and end-expiratory lung volume, PaO2, PaO2/FiO2 and (SpO2) were assessed. Results: PaO2 and PaO2/FiO2 ratio increased significantly in the RM group after RM from T2 (before pneumoperitoneum) to T6 (end of surgery) compared with group C (P < 0.001). Peak and plateau airway pressures increased significantly in group C from T2 till T5 (60 min after pneumoperitoneum) compared with the RM group (P < 0.001). End-expiratory lung volume increased significantly in the RM group after RM compared with group C (P<0.001). Conclusion: Preemptive RM with PEEP of 15 cm H2O was effective in preventing pneumoperitoneum-induced intraoperative hypoxemia and respiratory mechanics changes.

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Methodological issues in the design and analysis of cluster randomized trials

10.1093/med/9780198816805.003.0032 ◽

2021 ◽

pp. 113-128

Author(s):

Kathy J. Baisley ◽

Richard J. Hayes ◽

Lawrence H. Moulton

Keyword(s):

Gold Standard ◽

Randomized Trials ◽

Controlled Trials ◽

Cluster Randomized Trials ◽

Methodological Issues ◽

Eligibility Criteria ◽

Experimental Conditions ◽

Cluster Randomized ◽

And Control ◽

The Impact

Randomized controlled trials are the accepted gold standard for evaluating the effects of interventions to improve health. In the majority of such trials, individuals are randomly allocated to the experimental conditions under study, for example, to treatment and control arms. However, in some situations it is more appropriate to randomly allocate groups of individuals to the treatment arms. These groups are referred to as clusters, and trials of this kind are known as cluster randomized trials (CRTs). Examples of clusters include schools, villages, workplaces, or health facilities, but there are many other possible choices. In some CRTs, all individuals within the selected clusters are automatically included. In others, there may be additional eligibility criteria. Similarly, the impact of the intervention may be measured in all individuals in the cluster, or in a random subsample. This chapter aims to discuss methodological issues that arise in the design and analysis of CRTs

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Ventilatory Protective Strategies during Thoracic Surgery

Anesthesiology ◽

10.1097/aln.0b013e3182164356 ◽

2011 ◽

Vol 114 (5) ◽

pp. 1025-1035 ◽

Cited By ~ 47

Author(s):

Alf Kozian ◽

Thomas Schilling ◽

Hartmut Schütze ◽

Mert Senturk ◽

Thomas Hachenberg ◽

...

Keyword(s):

Mechanical Stress ◽

Lung Volume ◽

Lung Ventilation ◽

Alveolar Recruitment ◽

Distribution Data ◽

Dependent Lung ◽

One Lung Ventilation ◽

Lung Density ◽

Computed Tomographic ◽

Tidal Recruitment

Background The increased tidal volume (V(T)) applied to the ventilated lung during one-lung ventilation (OLV) enhances cyclic alveolar recruitment and mechanical stress. It is unknown whether alveolar recruitment maneuvers (ARMs) and reduced V(T) may influence tidal recruitment and lung density. Therefore, the effects of ARM and OLV with different V(T) on pulmonary gas/tissue distribution are examined. Methods Eight anesthetized piglets were mechanically ventilated (V(T) = 10 ml/kg). A defined ARM was applied to the whole lung (40 cm H(2)O for 10 s). Spiral computed tomographic lung scans were acquired before and after ARM. Thereafter, the lungs were separated with an endobronchial blocker. The pigs were randomized to receive OLV in the dependent lung with a V(T) of either 5 or 10 ml/kg. Computed tomography was repeated during and after OLV. The voxels were categorized by density intervals (i.e., atelectasis, poorly aerated, normally aerated, or overaerated). Tidal recruitment was defined as the addition of gas to collapsed lung regions. Results The dependent lung contained atelectatic (56 ± 10 ml), poorly aerated (183 ± 10 ml), and normally aerated (187 ± 29 ml) regions before ARM. After ARM, lung volume and aeration increased (426 ± 35 vs. 526 ± 69 ml). Respiratory compliance enhanced, and tidal recruitment decreased (95% vs. 79% of the whole end-expiratory lung volume). OLV with 10 ml/kg further increased aeration (atelectasis, 15 ± 2 ml; poorly aerated, 94 ± 24 ml; normally aerated, 580 ± 98 ml) and tidal recruitment (81% of the dependent lung). OLV with 5 ml/kg did not affect tidal recruitment or lung density distribution. (Data are given as mean ± SD.) Conclusions The ARM improves aeration and respiratory mechanics. In contrast to OLV with high V(T), OLV with reduced V(T) does not reinforce tidal recruitment, indicating decreased mechanical stress.

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Incorporating real-world evidence into the development of patient blood glucose prediction algorithms for the ICU

Journal of the American Medical Informatics Association ◽

10.1093/jamia/ocab060 ◽

2021 ◽

Author(s):

Oisin Fitzgerald ◽

Oscar Perez-Concha ◽

Blanca Gallego ◽

Manoj K Saxena ◽

Lachlan Rudd ◽

...

Keyword(s):

Critical Care ◽

Blood Glucose ◽

Glycemic Control ◽

Time Series Data ◽

Prediction Interval ◽

Data Sources ◽

Blood Glucose Monitoring ◽

Series Data ◽

Percentage Error ◽

Future Research

Abstract Objective Glycemic control is an important component of critical care. We present a data-driven method for predicting intensive care unit (ICU) patient response to glycemic control protocols while accounting for patient heterogeneity and variations in care. Materials and Methods Using electronic medical records (EMRs) of 18 961 ICU admissions from the MIMIC-III dataset, including 318 574 blood glucose measurements, we train and validate a gradient boosted tree machine learning (ML) algorithm to forecast patient blood glucose and a 95% prediction interval at 2-hour intervals. The model uses as inputs irregular multivariate time series data relating to recent in-patient medical history and glycemic control, including previous blood glucose, nutrition, and insulin dosing. Results Our forecasting model using routinely collected EMRs achieves performance comparable to previous models developed in planned research studies using continuous blood glucose monitoring. Model error, expressed as mean absolute percentage error is 16.5%–16.8%, with Clarke error grid analysis demonstrating that 97% of predictions would be clinically acceptable. The 95% prediction intervals achieve near intended coverage at 93%–94%. Discussion ML algorithms built on observational data sources, such as EMRs, present a promising approach for personalization and automation of glycemic control in critical care. Future research may benefit from applying a combination of methodologies and data sources to develop robust methodologies that account for the variations seen in ICU patients and difficultly in detecting the extremes of observed blood glucose values. Conclusion We demonstrate that EMRs can be used to train ML algorithms that may be suitable for incorporation into ICU decision support systems.

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Reflex compensation of voluntary inspiration when immersion changes diaphragm length

Journal of Applied Physiology ◽

10.1152/jappl.1985.59.2.611 ◽

1985 ◽

Vol 59 (2) ◽

pp. 611-618 ◽

Cited By ~ 6

Author(s):

R. B. Banzett ◽

R. W. Lansing ◽

M. B. Reid

Keyword(s):

Tidal Volume ◽

Water Level ◽

Lung Volume ◽

Present Experiment ◽

Muscle Activation ◽

Repeated Measurements ◽

Inspiratory Muscle ◽

Reflex Compensation ◽

Spontaneously Breathing ◽

Surface Electromyograms

When immersion alters inspiratory muscle operating lengths, spontaneously breathing humans maintain a constant tidal volume by reflex adjustment of inspiratory muscle activation (Reid et al. J. Appl. Physiol. 58: 1136–1142, 1985). We term this the operational length compensation reflex. The present experiment demonstrates that similar adjustments occur during voluntary respiratory maneuvers. Each of seven naive subjects sat in a tank with water at hip level. We trained them to reproduce an inspired volume (+/- 10%) at constant inspiratory duration. They received verbal feedback during training but not during the experiment. We measured surface electromyograms (EMGs) of diaphragm and intercostal muscles and tidal volume. After the subjects were trained, we made repeated measurements of 10 trained breaths with water at the hip and then again after raising water level to the xiphoid (which decreases lung volume and increases operating length of the diaphragm). In 30 of 42 trials there was a substantial fall in peak diaphragm EMG. In 10 trials this was sufficient to prevent any change in tidal volume. Inspiratory flow was more closely regulated than tidal volume. Subjects were not aware of making adjustments in drive.

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Empirical likelihood tests for nonparametric detection of differential expression from RNA-seq data

Statistical Applications in Genetics and Molecular Biology ◽

10.1515/sagmb-2015-0095 ◽

2015 ◽

Vol 14 (6) ◽

Author(s):

Thomas Thorne

Keyword(s):

Empirical Likelihood ◽

Gold Standard ◽

R Package ◽

Parametric Model ◽

Rna Seq ◽

Experimental Conditions ◽

Transcriptomic Data ◽

Nonparametric Approach ◽

Nonparametric Detection ◽

Computational Resources

AbstractThe availability of large quantities of transcriptomic data in the form of RNA-seq count data has necessitated the development of methods to identify genes differentially expressed between experimental conditions. Many existing approaches apply a parametric model of gene expression and so place strong assumptions on the distribution of the data. Here we explore an alternate nonparametric approach that applies an empirical likelihood framework, allowing us to define likelihoods without specifying a parametric model of the data. We demonstrate the performance of our method when applied to gold standard datasets, and to existing experimental data. Our approach outperforms or closely matches performance of existing methods in the literature, and requires modest computational resources. An R package, EmpDiff implementing the methods described in the paper is available from:

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