Capnogram and Fluid Responsiveness

Performance of CO2 Changes to Predict Fluid Responsiveness in Spontaneously Breathing Volunteers

Predicting fluid responsiveness in critically ill patients is of paramount importance. It can help define an adequate fluid balance. Overzealous fluid administration is poorly tolerated and has been associated with poor outcomes but so has insufficient administration. Currently available predictors of fluid responsiveness rely on invasive monitors and require patients to be on mechanical ventilation. It is thus important to develop non invasive novel methods to assess fluid responsiveness to provide an accurate management for a favorable outcome. We propose a readily available non-invasive method that relies on improvement of the ventilation perfusion mismatch as recorded by end tidal CO2.

Ventilation of physiologic dead space is part of a spectrum of mismatch between ventilation and perfusion of the lungs. The extent of pulmonary dead space varies depending on factors affecting pulmonary perfusion (e.g. pulmonary capillary hydrostatic pressure) and alveolar pressure (e.g. positive pressure ventilation). Compromised pulmonary capillary perfusion can lead to ventilation-perfusion mismatch in a patient with clear conductive airway and adequate alveolar oxygen pressure. Alveolar dead space results in decreased CO2 exchange that translates into lower levels of expired CO2.

Stroke volume of the right ventricle is a major determinant of the pulmonary capillary perfusion. Right ventricular cardiac output can be increased by passive lower limb elevation maneuver, which ultimately results in improvement of the ventilation to perfusion ratio. This effect leads to a higher participation of perfused (and ventilated) alveolar units in gas exchange and narrowing of the gradient between arterial and expired CO2 concentration. Performing a passive leg raising (PLR) maneuver leads to stroke volume enhancement in both healthy patients and in those experiencing hemodynamic instability. Responsiveness to PLR can be assessed by different methods including echocardiography and pulse pressure variation. Left ventricular cardiac output (LVCO) can be easily measured by transthoracic echo and be used as a surrogate of right ventricular preload changes. LVCO can thus be used to assess the fluid responsiveness of PLR and the effects of on end tidal CO2 that ensue.

We propose this study to test the hypothesis that expired CO2 is a reliable predictor of fluid responsiveness after performance of the PLR maneuver, based on the assumption that increasing right ventricular output causes a reduction of the ventilation to perfusion ratio, leading to increased levels of expired CO2. T

Study Overview

• Status: Withdrawn
• Conditions: Healthy; Blood Pressure
• Intervention / Treatment: Other: Passive leg raising

• Study Type: Interventional
• Phase: Not Applicable

Contacts and Locations

Study Locations

• United States
  • Georgia
    • Augusta, Georgia, United States, 30912
      • Augusta University

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: 18 years and older (ADULT, OLDER_ADULT)
• Accepts Healthy Volunteers: Yes
• Genders Eligible for Study: All

Description

Inclusion Criteria:

• Age older than 18 years

Exclusion Criteria:

• Cardiovascular and respiratory disease reported by the participant

Study Plan

How is the study designed?

Design Details

• Primary Purpose: DIAGNOSTIC
• Allocation: NA
• Interventional Model: SINGLE_GROUP
• Masking: NONE

Number of Arms

1

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
EXPERIMENTAL: Passive leg raising; Passive leg raising for 3 minutes after 20 seconds of lying flat	Other: Passive leg raising; After 30 seconds of lying flat, volunteers will have passive leg raising to 45 degrees. Expired CO2 will be measured via a face mask before and after leg raising.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Expired CO2	Area under the curve of a capnogram tracing will be measured in milimiters	10 minutes

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Mean arterial pressure	Mean arterial pressure in mmHg measured by non invasive oscillometer	10 minutes
Heart rate	beats per minute measured by non invasive plethysmography	10 minutes

Collaborators and Investigators

• Sponsor: Augusta University

Study record dates

Study Major Dates

• Study Start (ACTUAL): May 1, 2019
• Primary Completion (ANTICIPATED): December 1, 2021
• Study Completion (ANTICIPATED): December 1, 2021

Study Registration Dates

• First Submitted: December 26, 2018
• First Submitted That Met QC Criteria: December 26, 2018
• First Posted (ACTUAL): December 28, 2018

Study Record Updates

• Last Update Posted (ACTUAL): July 28, 2021
• Last Update Submitted That Met QC Criteria: July 21, 2021
• Last Verified: July 1, 2021

More Information

Terms related to this study

• Other Study ID Numbers: 1368341

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: UNDECIDED

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No