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The value of dynamic preload variables during spontaneous ventilation

Perel, Azriel

Current Opinion in Critical Care: August 2017 - Volume 23 - Issue 4 - p 310–317
doi: 10.1097/MCC.0000000000000430
CARDIOVASCULAR SYSTEM: Edited by Thomas W.L. Scheeren

Purpose of review To discuss the physiological significance and clinical value of dynamic preload variables in spontaneously breathing patients.

Recent findings Dynamic preload variables reflect the response of the cardiac output to a modification of preload and can therefore be used to assess fluid responsiveness. Continuous dynamic parameters that are calculated from the variations in the arterial and plethysmographic waveforms following a mechanical breath have been shown to predict fluid responsiveness much better than static preload parameters. These parameters are displayed on many patient monitors though their use is limited to mechanically ventilated patients. However, spontaneous breathing may also induce significant hemodynamic changes because of the repetitive negative swings in the pleural pressure. By better understanding the physiological basis of these changes, the same ‘dynamic parameters’ can be used to gain unique physiological insights during spontaneous breathing. These include the ability to identify and/or monitor respiratory rate, respiratory effort (e.g., patient–ventilator asynchrony), fluid responsiveness (to some degree), pulsus paradoxus (e.g. asthma, cardiac tamponade), and, importantly, upper airway obstruction.

Summary Although originally intended to be used only during mechanical ventilation, ‘dynamic parameters’ may offer valuable clinical information in spontaneously breathing patients.

Department of Anesthesiology and Intensive Care, Sheba Medical Center, Tel Aviv University, Tel Aviv, Israel

Correspondence to Prof. Azriel Perel, Department of Anesthesiology and Intensive Care, Sheba Medical Center, Tel Aviv 52621, Israel. Tel: +97235302754; fax: +97235303689; e-mail:

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