Changes of Pulse Pressure Variation Duing Tidal Volume Challenge in Patients With Spontaneous Breathing

Study Overview
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Brief Summary
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Background: Predicting preload responsiveness by using dynamic indicators before administering fluids to critically ill patients is nowadays routinely performed at the bedside. Unlike other dynamic indicators of preload responsiveness that require cardiac output monitoring, pulse pressure variation (PPV) can be simply obtained via an arterial catheter . However, PPV is not reliable in mechanically ventilated patients with spontaneous breathing activity. We hypothesized that an increase in PPV after a tidal volume (TV) challenge (TVC) or a decrease in PPV during passive leg raising (PLR) will predict preload responsiveness in such cases. Objective: to examine if the change in PPV during PLR and after a TVC can predict preload responsiveness in patients with mechanical ventilation and persistent spontaneous breathing

Detailed Description
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Prospective non interventional study conducted in two intensive care units. Patients under mechanical ventilation with spontaneous cycles, for whom the physician in charge decided to test preload responsiveness were included. We collected demographic and clinical information, the use of mechanical ventilation and its parameters, the use of vasopressors and their dosage and blood lactate. Firstly, transthoracic echocardiography (TTE) was performed to measure the velocity time integral (VTI) of the left ventricular outflow tract . A PLR maneuvre is performed with TTE probe in place and a new assessement of VTI is measured, in addition to the PPV and other hemodynamic parmeters (Diastolic, mean and systolic arterial pressure, heart rate, CVP). Delta VTI is the difference between VTI during PLR and VTI at baseline divided by VTI at baseline. Patients were considered as preload responsive when delta VTI was ≥10%. Secondly, a TVC was performed by increasing the TV by 2mL/kg predicted body weight from its baseline value . PPV was recorded before and after the TVC in addition to the other hemodynamic parmeters listed above. Further more, respiratory parameters are collected: ventilator setting, plateau pressure, upper airway pressure, before and during the TVC.

Official Title
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Can Dynamic Changes of Pulse Pressure Variation During Passive Leg Raising or a Tidal Volume Challenge Help Predicting Preload Responsiveness in Mechanically Ventilated Patients With Spontaneous Breathing Activity

Conditions
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Hemodynamic Monitoring

Intervention / Treatment
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* Diagnostic Test: passive leg raising


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: adult critically ill patients if the clinicians in charge decided to test preload responsiveness because of mean arterial pressure (MAP) < 65 mmHg (measured by an arterial catheter) or other symptoms of acute circulatory failure (e.g. oliguria, skin mottling, tachycardia, hyperlactatemia) Exclusion Criteria: Arrythmia no spontaneous breathing difficult condition for tansthoracic echocardiography

Ages Eligible for Study
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Minimum Age: 18 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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No

Study Plan
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How is the study designed?
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Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| preload responders<br>patients who increase their delta VTI by more than 10% during PLR | Diagnostic Test: passive leg raising<br>* passive leg raising: to raise the legs of the patients by adjusting the angle of the patient's bed during one minute. Tidal volume challenge: an increas by 2ml/Kg of the tidal volume during one minute<br>* Other names: tidal volume challenge;|
| preload unresponders<br>patients who do not increase their delta VTI by more than 10% during PLR | |

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| predictive capacity of the changes of PPV during tidal volume challenge | A roc curve analysis will be performed in order to determine the specificity and the sensitivity of this test to predict preload responsiveness | duration of the tests: 15 minutes | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| predictive capacity of changes of PPV during ppassive leg raising test | A roc curve analysis will be erformed in order to determine the specificity and the sensitivity of this test to predict preload responsiveness | duration of the tests: 15 minutes |