The technology

The Acumen IQ Sensor with Acumen hypotension prediction index (HPI) software (Edwards Lifesciences Ltd) is designed to predict the chance of an individual having a hypotensive event in surgical and non-surgical settings. A hypotensive event is defined as mean arterial pressure (MAP) of less than 65 mmHg, that exceeds a cumulative length of 15 minutes. The sensor attaches to any existing radial arterial line and is used to automatically calculate key parameters every 20 seconds. The parameters include HPI, contractility (systolic slope; dP/dt), afterload (dynamic arterial elastance), cardiac output, pulse rate, stroke volume, stroke volume variation, MAP, cardiac index, pulse pressure variation and systemic vascular resistance.

The Acumen IQ sensor uses Acumen HPI software on the HemoSphere advanced monitoring system. The Acumen HPI software uses a machine-learning based algorithm to detect the instability that causes potential hypotensive events, using predictive features from the arterial pressure waveform. The algorithm defines hypotension as MAP below 65 mmHg for at least 1 minute. The algorithm output is an index value called the HPI parameter, which ranges from 0 to 100. The higher the HPI parameter value, the higher the chance of an individual trending towards a hypotensive event. If the HPI parameter value exceeds 85 for 2 consecutive 20-second updates, or reaches 100 at any time, the HPI high alert popup will appear on the monitor. The Acumen HPI software (through its secondary screen) gives information on additional advanced haemodynamic pressure and flow parameters so clinicians can investigate the potential root cause of the hypotensive event. These include measures of stroke volume variation, left ventricular contractility and dynamic arterial elastance.

The HemoSphere monitor can be used with other non-invasive sensors to measure additional parameters, including haemodynamic status and peripheral or cerebral saturation. The monitor has a touch screen and can switch between different parameter measurement screens.


The company states that the Acumen HPI software is the first technology of its kind in this area. It is unique because it is based on waveform analysis to give information on the chance of a hypotensive event. The company claims that this algorithm, developed by machine learning using data from over 59,000 hypotensive events and over 144,000 non-hypotensive events, predicts hypotension up to 15 minutes before an event. The company states that earlier detection of hypotension may reduce the risk of complications after hypotensive events, such as cardiac injury or acute kidney injury. This could reduce hospital length of stay and unplanned readmissions.

Current care pathway

Blood pressure is routinely monitored using a non-invasive blood pressure monitor which would alert the clinician when an individual becomes hypotensive. Arterial lines, normally situated in the radial artery, can also allow the continuous monitoring of the systemic arterial pressure (providing readings around every 5 to 15 minutes) and are generally used for the those who are critically ill.

Population, setting and intended user

The technology would be used for surgical cases (both cardiac and non-cardiac) in which an arterial line is recommended. It would be used in tertiary or secondary care by healthcare practitioners who are trained in monitoring physiological measurements. In an operating theatre, this would be an anaesthetist.


Technology costs

Acumen IQ sensor costs £400 per sensor (excluding VAT). The sensors are single use. The price per sensor decreases if more are purchased.

A HemoSphere monitor costs £27,470 per device (excluding VAT). The price per device decreases if more are purchased. Maintenance costs are part of the HemoSphere capital contract. This capital contract is in addition to the cost of the monitor. The useful lifespan of the monitor is 5 to 7 years. The monitor can be activated for HPI capability when a minimum of 10 Acumen IQ sensors are purchased.

Costs of standard care

An invasive blood pressure transducer costs around £13 to £24 (excluding VAT) and the cost of the monitor is around £10,000 to £23,000 per unit (excluding VAT).

Resource consequences

Acumen IQ sensor is currently used in clinical trials at 2 NHS trusts and routinely used in 1 NHS hospital. The company claims that using the Acumen IQ sensor with Acumen HPI software could be cost saving because of fewer hypotensive events and improved fluid management, leading to a reduction in adverse outcomes such as acute kidney injury and cardiac injury. This may lead to cost savings from reduced intensive care length of stay. It also could reduce overall length of stay, the need for further treatment or unplanned admissions. There is no published evidence to support these claims. The HemoSphere monitor can also be used for monitoring additional parameters that could prevent the use of multiple monitors in the operating room. However, experts state that additional monitors would still be needed in addition to the HemoSphere monitor. Training is provided by the company and is included with the price of the monitoring platform and sensors. Training includes proctoring, in-person training, virtual training and on-site procedural support.