Dataset Information

Evaluation of end-tidal carbon dioxide gradient as a predictor of volume responsiveness in spontaneously breathing healthy adults.

ABSTRACT:

Background

Methods to guide fluid therapy in spontaneously breathing patients are scarce. No studies have reported the accuracy of end-tidal CO₂ (ET-CO₂) to predict volume responsiveness in these patients. We sought to evaluate the ET-CO₂ gradient (?ET-CO₂) after a passive leg rise (PLR) maneuver to predict volume responsiveness in spontaneously breathing healthy adults.

Methods

We conducted a prospective study in healthy adult human volunteers. A PLR maneuver was performed and cardiac output (CO) was measured by transthoracic echocardiography. ET-CO2 was measured with non-invasive capnographs. Volume responsiveness was defined as an increase in cardiac output (CO) >?12% at 90 s after PLR.

Results

Of the 50 volunteers, 32% were classified as volume responders. In this group, the left ventricle outflow tract velocity time integral (VTI_LVOT) increased from 17.9?±?3.0 to 20.4?±?3.4 (p?=?0.0004), CO increased from 4.4?±?1.5 to 5.5?±?1.6 (p?=?0.0), and ET-CO₂ rose from 32 ±?4.84 to 33 ±?5.07 (p?=?0.135). Within the entire population, PLR-induced percentage ?CO was not correlated with percentage ?ET-CO₂ (R²?=?0.13; p?=?0.36). The area under the receiver operating curve for the ability of ET-CO₂ to discriminate responders from non-responders was of 0.67?±?0.09 (95% CI 0.498-0.853). A ?ET-CO₂???2 mmHg had a sensitivity of 50%, specificity of 97.06%, positive likelihood ratio of 17.00, negative likelihood ratio of 0.51, positive predictive value of 88.9%, and negative predictive value of 80.5% for the prediction of fluid responsiveness.

Conclusions

?ET-CO₂ after a PLR has limited utility to discriminate responders from non-responders among healthy spontaneously breathing adults.

SUBMITTER: Arango-Granados MC

PROVIDER: S-EPMC6066588 | biostudies-literature | 2018 Jul

REPOSITORIES: biostudies-literature

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Evaluation of end-tidal carbon dioxide gradient as a predictor of volume responsiveness in spontaneously breathing healthy adults.

Arango-Granados María C MC Zarama Córdoba Virginia V Castro Llanos Andrés M AM Bustamante Cristancho Luis A LA

Intensive care medicine experimental 20180730 1

<h4>Background</h4>Methods to guide fluid therapy in spontaneously breathing patients are scarce. No studies have reported the accuracy of end-tidal CO<sub>2</sub> (ET-CO<sub>2</sub>) to predict volume responsiveness in these patients. We sought to evaluate the ET-CO<sub>2</sub> gradient (ΔET-CO<sub>2</sub>) after a passive leg rise (PLR) maneuver to predict volume responsiveness in spontaneously breathing healthy adults.<h4>Methods</h4>We conducted a prospective study in healthy adult human vol ...[more]

PMID: 30062599

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Project description:BackgroundIncreasing functional residual capacity (FRC) or tidal volume (VT) reduces airway resistance and attenuates the response to bronchoconstrictor stimuli in animals and humans. What is unknown is which one of the above mechanisms is more effective in modulating airway caliber and whether their combination yields additive or synergistic effects. To address this question, we investigated the effects of increased FRC and increased VT in attenuating the bronchoconstriction induced by inhaled methacholine (MCh) in healthy humans.MethodsNineteen healthy volunteers were challenged with a single-dose of MCh and forced oscillation was used to measure inspiratory resistance at 5 and 19 Hz (R5 and R19), their difference (R5-19), and reactance at 5 Hz (X5) during spontaneous breathing and during imposed breathing patterns with increased FRC, or VT, or both. Importantly, in our experimental design we held the product of VT and breathing frequency (BF), i.e, minute ventilation (VE) fixed so as to better isolate the effects of changes in VT alone.ResultsTripling VT from baseline FRC significantly attenuated the effects of MCh on R5, R19, R5-19 and X5. Doubling VT while halving BF had insignificant effects. Increasing FRC by either one or two VT significantly attenuated the effects of MCh on R5, R19, R5-19 and X5. Increasing both VT and FRC had additive effects on R5, R19, R5-19 and X5, but the effect of increasing FRC was more consistent than increasing VT thus suggesting larger bronchodilation. When compared at iso-volume, there were no differences among breathing patterns with the exception of when VT was three times larger than during spontaneous breathing.ConclusionsThese data show that increasing FRC and VT can attenuate induced bronchoconstriction in healthy humans by additive effects that are mainly related to an increase of mean operational lung volume. We suggest that static stretching as with increasing FRC is more effective than tidal stretching at constant VE, possibly through a combination of effects on airway geometry and airway smooth muscle dynamics.

Project description:Patients who increase stoke volume or cardiac index more than 10 or 15% after a fluid challenge are usually considered fluid responders. Assessment of fluid responsiveness prior to volume expansion is critical to avoid fluid overload, which has been associated with poor outcomes. Maneuvers to assess fluid responsiveness are well established in mechanically ventilated patients; however, few studies evaluated maneuvers to predict fluid responsiveness in spontaneously breathing patients. Our objective was to perform a systematic review of literature addressing the available methods to assess fluid responsiveness in spontaneously breathing patients. Studies were identified through electronic literature search of PubMed from 01/08/2009 to 01/08/2016 by two independent authors. No restrictions on language were adopted. Quality of included studies was evaluated with Quality Assessment of Diagnostic Accuracy Studies tool. Our search strategy identified 537 studies, and 9 studies were added through manual search. Of those, 15 studies (12 intensive care unit patients; 1 emergency department patients; 1 intensive care unit and emergency department patients; 1 operating room) were included in this analysis. In total, 649 spontaneously breathing patients were assessed for fluid responsiveness. Of those, 340 (52%) were deemed fluid responsive. Pulse pressure variation during the Valsalva maneuver (?PPV) of 52% (AUC ± SD: 0.98 ± 0.03) and passive leg raising-induced change in stroke volume (?SV-PLR) > 13% (AUC ± SD: 0.96 ± 0.03) showed the highest accuracy to predict fluid responsiveness in spontaneously breathing patients. Our systematic review indicates that regardless of the limitations of each maneuver, fluid responsiveness can be assessed in spontaneously breathing patients. Further well-designed studies, with adequate simple size and power, are necessary to confirm the real accuracy of the different methods used to assess fluid responsiveness in this population of patients.

Project description:BACKGROUND:In an increasingly comorbid population, there are significant challenges to diagnosing the cause of breathlessness, and once diagnosed, considerable difficulty in detecting deterioration early enough to provide effective intervention. The burden of the breathless patient on the health care economy is substantial, with asthma, chronic heart failure, and pneumonia affecting over 6 million people in the United Kingdom alone. Furthermore, these patients often have more than one contributory factor to their breathlessness symptoms, with conditions such as dysfunctional breathing pattern disorders-an under-recognized component. Current methods of diagnosing and monitoring breathless conditions can be extensive and difficult to perform. As a consequence, home monitoring is poorly complied with. In contrast, capnography (the measurement of tidal breath carbon dioxide) is performed during normal breathing. There is a need for a simple, easy-to-use, personal device that can aid in the diagnosis and monitoring of respiratory and cardiac causes of breathlessness. OBJECTIVE:The aim of this study was to explore the use of a new, handheld capnometer (called the N-Tidal C) in different conditions that cause breathlessness. We will study whether the tidal breath carbon dioxide (TBCO2) waveform, as measured by the N-Tidal C, has different characteristics in a range of respiratory and cardiac conditions. METHODS:We will perform a longitudinal, observational study of the TBCO2 waveform (capnogram) as measured by the N-Tidal C capnometer. Participants with a confirmed diagnosis of asthma, breathing pattern disorders, chronic heart failure, motor neurone disease, pneumonia, as well as volunteers with no history of lung disease will be asked to provide twice daily, 75-second TBCO2 collection via the N-Tidal C device for 6 months duration. The collated capnograms will be correlated with the underlying diagnosis and disease state (stable or exacerbation) to determine if there are different TBCO2 characteristics that can distinguish different respiratory and cardiac causes of breathlessness. RESULTS:This study's recruitment is ongoing. It is anticipated that the results will be available in late 2018. CONCLUSIONS:The General Breathing Record Study will provide an evaluation of the use of capnography as a diagnostic and home-monitoring tool for various diseases. REGISTERED REPORT IDENTIFIER:RR1-10.2196/9767.

Dataset Information

Evaluation of end-tidal carbon dioxide gradient as a predictor of volume responsiveness in spontaneously breathing healthy adults.

Background

Methods

Results

Conclusions

Publications

Evaluation of end-tidal carbon dioxide gradient as a predictor of volume responsiveness in spontaneously breathing healthy adults.

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