Patients had invasive mechanical ventilation; vasoactive agent wasn’t used or had been evacuate

是/Yes

sinus rhythm

是/Yes

existing fluid infusion test contraindication (acute coronary syndrome, cardiogenic shock and evidence showing overload fluid)

否/No

being obvious right ventricular dysfunction, right heart failure and tricuspid regurgitation

否/No

being younger than 18 years old

否/No

being gestation

否/No

being intra-abdominal hypertension, bladder pressure measured by catheter ＞16cmH2O

否/No

existing pneumothorax or pulmonary bulla Without drainage.

否/No