Comparison of Continuous Non-invasive Pressure Device Versus Invasive Pressure Measurement During Prehospital Emergency

The aim of the study is to evaluate the accuracy of continuous non-invasive AP monitoring (CNAP) compared to simultaneous IBP measurement in intensive care patients undergoing a transport in the ambulance car.

Since CNAP finger blood pressure is calibrated to NBP level, a systematic bias between IBP and CNAP as described by a recent FDA meta analysis [ ] is expected. The most important factor of CNAP system performance is its ability to accurately track blood pressure changes. Thus, the purpose of this investigation is to show that the bias between CNAP and IBP falls within the expected range and that blood pressure alterations are detected instantaneously.

The endpoints of the study are:

• The agreement of systolic, diastolic and mean CNAP and IBP readings determined on a beat-to-beat basis during:
• Takeover of the patient on the intensive care unit,
• Transport of the patient from the intensive care unit to the ambulance car
• Transport of the patient in the ambulance car
• The agreement of systolic, diastolic and mean CNAP and IBP blood pres-sure changes determined on a beat-to-beat basis during:
• Takeover of the patient on the intensive care unit,
• Transport of the patient from the intensive care unit to the ambulance car
• Transport of the patient in the ambulance car

The beat-to-beat readings of CNAP and IBP will be automatically recorded electronically on a memory card in the transport monitor. CNAP data will additionally be recorded directly on the CNAP Monitor with a memory stick. Safety will be assessed by clinical observations as well as adverse events (AE) recording.

Arterial pressure (AP) is one of the most important physiological variables. Particularly in emergency medicine, AP needs to be monitored repeatedly or even better, continuously. This is usually done using an oscillometric pressure device (NIBP). A number of studies emphasise the importance of continuous AP monitoring as more than 20% of all hypotensive episodes may be missed by NIBP and another 20% are detected with delay. Prolonged hypotension precedes 56% of perioperative cardiac arrests and is associated with a significant increase of the 1-year mortality rate, indicating that NBP monitoring especially in patients with cardiovascular diseases might be insufficient independent from the clinical setting. Recently, a monitor for continuous non-invasive AP monitoring (CNAP™ Monitor 500) was introduced. It was shown that during procedures with high risk of hypotension NIBP missed significant more hypotensive episodes than CNAP. At the moment we have no evidence of the performance of CNAP in the preclinical emergency medicine. The evaluation against the gold standard of invasive pressure measurement in this study will help us to evaluate the performance of CNAP in the preclinical setting.

ICU Patients with established arterial pressure measurement

Inclusion Criteria:

• Patients willing and capable of giving informed consent or with legal agents willing of giving informed consent
• Patients undergoing a transport from the intensive care unit to another institution with the ambulance car
• Patients where the IBP cannula was already placed on the intensive care unit
• Patients where IBP cannula, and CNAP upper arm cuff can be placed on the same arm, and CNAP finger cuff can be placed on the contra-lateral arm
• Intact perfusion of both arm evidenced by a negative Allen's test
• Age 18 years and above
• ASA I-IV
• Weight >= 40 and <= 180 kg, BMI < 35

Exclusion Criteria:

• Patients with history of neurological, neuromuscular seizure
• Patients where IBP cannula cannot be placed in the radial artery
• Patients with vascular implants at the sites of non-invasive blood pressure measurement (fingers and upper arm)
• Patients with history of arrhythmias
• Edematous patients