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Haemodynamic changes induced by two I:E ratios: a transoesophageal echocardiographic study
J M Vedrinne1, S Duperret, F Decaillot
1Department of Anaesthesia and Intensive Care, Edouard Herriot University Hospital, Lyon, France.
Summary
Adjusting the inspiratory-expiratory (I:E) ratio during mechanical ventilation can rapidly assess a patient's fluid status. Increased I:E ratios, like 1:1, effectively change systolic blood pressure variation (SBPV) and end-diastolic area (EDA) to indicate preload.
Area of Science:
- Critical Care Medicine
- Cardiovascular Physiology
- Respiratory Mechanics
Background:
- Mechanical ventilation is crucial for patients with moderate to severe respiratory disease.
- Optimizing ventilator settings, including the inspiratory-expiratory (I:E) ratio, is essential for managing hemodynamics and cardiac function.
- Assessing left ventricular preload and intravascular volume status can be challenging in ventilated patients.
Purpose of the Study:
- To evaluate the impact of different I:E ratios (1:3 vs. 1:1) on hemodynamic and left ventricular function.
- To utilize arterial pressure waveform fluctuations and transesophageal echocardiography (TEE) for assessing these effects.
- To determine if changes in these parameters can reliably indicate intravascular volume status.
Main Methods:
- Nine patients with moderate to severe respiratory disease underwent volume-controlled ventilation.
- Two I:E ratios (1:3 and 1:1) were applied, with respiratory rate adjusted for six cardiac beats per cycle.
- Systolic blood pressure variation (SBPV), left ventricular area variations via TEE, and pulmonary artery catheter data were compared.
Main Results:
- An I:E ratio of 1:1 decreased end-diastolic area (EDA) by 3-8% and increased SBPV from 6 to 11 mmHg compared to 1:3.
- SBPV exceeded 12 mmHg with a 1:1 I:E ratio in four patients, while it remained below 10 mmHg with a 1:3 ratio.
- EDA decreased by up to 7% during expiration with a 1:1 I:E ratio; ejection fraction area remained stable.
Conclusions:
- End-diastolic area (EDA) and systolic blood pressure variation (SBPV) provide beat-to-beat assessment of left ventricular preload during I:E ratio changes.
- Switching from an I:E ratio of 1:3 to 1:1 serves as a rapid, safe, and reversible method to estimate intravascular volume status.
- This method, using SBPV or EDA changes, offers a practical approach to volume assessment in mechanically ventilated patients.