The haemodynamic effects of pneumoperitoneum on pulse pressure variation – a prospective, observational study

Fig. 1. Description of patient eligibility, inclusion and exclusion. PPVGAM: Pulse pressure variation derived with the generalised additive model

Fig. 2. Example of how general additive model (GAM)-modelling was performed in one patient. Panel A: The arterial blood pressure curve over time. Panel B: The pulse pressures derived from panel A. Each cyclic swing in pulse pressure represents one respiratory cycle. Green and blue segments are the sections undergoing GAM-modelling to derive PPV before and at the end of insufflation. Panel C: The intra-abdominal pressure time stamps (0 mmHg corresponds to baseline, initiation of insufflation). Panel D: The timing of the heartbeat in the respiratory cycle (left) and the effect of time passed (right) and their effect on pulse pressure before induction of pneumoperitoneum. Panel E: Represent the same calculations as panel D, but for measurements at the end of pneumoperitoneum induction at an intra-abdominal pressure of 12 mmHg ART: Arterial blood pressure, PP: pulse pressure

Fig. 3. Spaghetti plot of generalised additive model (GAM)-derived pulse pressure variation (PPV) and its change on the logarithmic scale with different intra-abdominal pressures. Black line: median GAM-derived PPV

Fig. 4. Illustrations of Frank Starling curves and immediate effects of intra-abdominal pressure on the left ventricle. (A) Left and right-wards shifts in operating position, slope and their influence on SVV. ① baseline ② increased preload ③ decreased preload. (B) Downward and upward shifts of the Frank Starling curve with increased afterload, reduced contractility or vice versa. SVV1: baseline, SVV2: increased afterload, SVV3: decreased afterload. ΔPreload: Preload variation during positive pressure ventilation, SVV: Stroke voume variation