Use of Heart-lung Interaction to Predict Haemodynamic Tolerance to the Open Lung Approach With Individualised PEEP

Inclusion Criteria: * Patients over 18 years of age; undergoing scheduled non-cardiothoracic surgery; under controlled invasive mechanical ventilation and invasive arterial monitoring; supine position; positive air test Exclusion Criteria: * Chronic pulmonary disease (defined as chronic obstructive pulmonary disease grade 3 or higher or any disease requiring long-term oxygen therapy); congenital cardiac malformations; severe valvular heart disease; heart failure NYHA (New York Heart Association) Grade III/IV; arrhythmias; history of reduced ventricular systolic function (FEVI \<40% or TAPSE \<17 cm/s); history of pulmonary hypertension; BMI \>35 (due to altered lung compliance and rib cage); heart rate/respiratory rate ratio \< 3.6; presence of inspiratory effort; open chest; increased intra-abdominal pressure (due to pathology or pneumoperitoneum); altered pulmonary or rib cage compliance due to surgery (trendelemburg or antitrendelemburg position); uncorrected optimal arterial waveform (resonant or damped) and presence of any contraindication to lung recruitment manoeuvres. The latter are: pulmonary emphysema, pulmonary bullae, uncontrolled haemodynamic instability, right heart failure, elevated intracranial pressure (decreased return flow through jugular veins) or lack of monitoring if necessary, bronchospasm, undrained pneumothorax.