Evaluation of the esCCO Non-invasive Cardiac Output Measurement Device in Pregnancy

Cardiac output (CO) is the volume of blood ejected from the heart and is a product of stroke volume (SV) vs heart rate (HR). It is closely related to Blood Pressure (BP) by the formula CO = Mean Arterial Pressure (MAP) / Systemic Vascular Resistance (SVR). Cardiac output monitoring is well established and validated for guiding fluid administration and resuscitation in intensive care and perioperatively in the non-pregnant population. Available CO monitoring methods may risk maternal health or fetal wellbeing or are unvalidated in the pregnant population. Invasive and semi-invasive methods of measuring CO such as the pulmonary artery catheter, the 'gold standard' require invasive arterial or central access negating their use in all but a select group of labouring women and have potentially serious risks attached to their usage. Echocardiography is a well-established and validated technique requiring no invasive access but the requirement for an experienced operator limits routine usage. It uses an external ultrasound probe to scan the heart.

Several novel non-invasive cardiac output monitors have recently come to the market including the estimated cardiac output esCCO monitor (Nihon Kohden) which uses Pulse Wave Transit Time (PWTT) to estimate cardiac output. It requires 3-lead Electrocardiography and pulse oximetry alone which is part of the routine monitoring for high risk patients on the labour ward.

The investigators research aims to evaluate the accuracy and precision of the esCCO in pregnant women and subsequently assess its utility during medical interventions such as epidural analgesia or caesarean section. The initial validation will take place in an antenatal clinic where women are assessed using Doppler echocardiography. The investigators will then compare the echocardiography results vs the esCCO results.