Dynamic variations of bio-impedance measured cardiac output using non pharmacologic intervention (sitting position, passive leg rising and valsalva maneuver) could be used to detect acute heart failure in patients admitted to the ED for dyspnea.

Acute heart failure (AHF) is a frequent condition in emergency basis and is responsible of a big number of admissions, complications, and deaths.

despite advances in diagnostic techniques, AHF diagnosis still difficult and cost not effective.

Measurement of cardiac output (CO) is used as a way to evaluate global cardiac function and changes in CO may be used to identify a change in the hemodynamic status of a patient.

the gold standard of measuring CO is thermodilution catheterization, however this is an invasive technique that poses a risk to the patient.

Impedance cardiography (ICG) is a noninvasive method for measuring CO. it is performed by applying small electrical current to the chest, and through electrodes placed on the neck and sides.

the pulsatile flow of blood causes fluctuations in the current, and the device calculates CO from the impedance waveform.

In practice, the investigators connect the device "BIOPAC" by using four electrodes which the investigators place on the base of the neck (posterior face) and on the base of the thorax (posterior face).

The ECG recording is taken simultaneously with two other electrodes placed at the right upper limb and left lower limb.

In addition to detecting the electric current and the ECG, heart sounds are recorded using a sensor that is placed at the mitral site.

The various curves are displayed simultaneously and stored for analysis. Subjects were first placed in the semi sitting position 30°, and after 5 minutes had cardiac output measurements performed. (CO1)

A second cardiac output measurement was performed after 5 min of seated position. (C02)

Patients were then placed in the initial position, and after an additional 5 minutes had cardiac output measurements performed. (CO1')

A third set of measurement was obtained during 45° passive leg raising at 1 to 2 minutes.(CO3)

Patients were then placed in the initial position, and after an additional 5 minutes had cardiac output measurements performed. (CO1'')

During a Valsalva maneuver the investigators took the fourth cardiac output measurement. (CO4)

Patients were then placed in the initial position, and after an additional 5 minutes had cardiac output measurements performed. (CO1''')

Dynamic variations on bio-impedance measured CO using non pharmacologic intervention (sitting position, passive leg rising and Valsalva maneuver) could be used to detect AHF in patients admitted to the ED for dyspnea.

Inclusion Criteria:

• 18 year old or above
• non traumatic acute dyspnea

Exclusion Criteria:

• age <18 years,
• cardio respiratory arrest,
• coma,
• shock,
• need for inotropic or vasoactive drugs,
• mechanical ventilation,
• severe and sustained rhythm disorders,
• severe mitral valve disease,
• severe pulmonary arterial hypertension
• renal insufficiency with creatinine>150 μmol/l.