Towards continuous non-invasive blood pressure measurements-interpretation of the vasculature response to cuff inflation.

Blood pressure (BP) surrogates, such as pulse transit time (PTT) or pulse arrival time (PAT), have been intensively explored with the goal of achieving cuffless, continuous, and accurate BP inference. In order to estimate BP, a one-point calibration strategy between PAT and BP is typically used. Recent research focuses on advanced calibration procedures exploiting the cuff inflation process to improve calibration robustness by active and controlled modulation of peripheral PAT, as measured via plethysmograph (PPG) and electrocardiogram (ECG) combination.

Modulation of pulse travel and blood flow during cuff inflation- An experimental case study.

The blood pressure (BP) cuff can be used to modulate blood flow and propagation of pressure pulse along the artery. In our previous work, we researched methods to adapt cuff modulation techniques for pulse transit time vs. BP calibration and for measurement of other hemodynamic indices of potential interest to critical care, such as arterial compliance.

Modulation of Pulse Propagation and Blood Flow via Cuff Inflation-New Distal Insights.

In standard critical care practice, cuff sphygmomanometry is widely used for intermittent blood pressure (BP) measurements. However, cuff devices offer ample possibility of modulating blood flow and pulse propagation along the artery. We explore underutilized arrangements of sensors involving cuff devices which could be of use in critical care to reveal additional information on compensatory mechanisms.

Perioperative measurement of core body temperature using an unobtrusive passive heat flow sensor.

Clinicians strive to maintain normothermia, which requires measurement of core-body temperature and may necessitate active warming of patients. Monitoring temperature currently requires invasive probes. This work investigates a novel foam-based flexible sensor worn behind the ear for the measurement of core body temperature.

Finger and forehead photoplethysmography-derived pulse-pressure variation and the benefits of baseline correction.

To non-invasively predict fluid responsiveness, respiration-induced pulse amplitude variation (PAV) in the photoplethysmographic (PPG) signal has been proposed as an alternative to pulse pressure variation (PPV) in the arterial blood pressure (ABP) signal. However, it is still unclear how the performance of the PPG-derived PAV is site-dependent during surgery. The aim of this study is to compare finger- and forehead-PPG derived PAV in their ability to approach the value and trend of ABP-derived PPV.

Detection of a spontaneous pulse in photoplethysmograms during automated cardiopulmonary resuscitation in a porcine model.

Introduction: Reliable, non-invasive detection of return of spontaneous circulation (ROSC) with minimal interruptions to chest compressions would be valuable for high-quality cardiopulmonary resuscitation (CPR). We investigated the potential of photoplethysmography (PPG) to detect the presence of a spontaneous pulse during automated CPR in an animal study.

Methods: Twelve anesthetized pigs were instrumented to monitor circulatory and respiratory parameters.

The influence of nonlinear intra-thoracic vascular behaviour and compression characteristics on cardiac output during CPR.

Clinical observations suggest that the assumption of a linear relationship between chest compression pressure and cardiac output may be oversimplified. More complex behaviour may occur when the transmural pressure is large, changing the compliances and resistances in the intra-thoracic vasculature. A fundamental understanding of these compression induced phenomena is required for improving CPR.

The impact of compliant surfaces on in-hospital chest compressions: effects of common mattresses and a backboard.

Purpose: To evaluate, in a hospital setting, the influence of different, common mattresses, with and without a backboard, on chest movement during CPR.

Design And Setting: Sixty CPR sessions (140s each, 30:2, C:R ratio 1:1) were performed using a manikin on standard hospital mattresses, with or without a backboard in combination with variable weights. Sternum-to-spine compression distance was controlled (range 30-60mm) allowing evaluation of the underlying compliant surface on total hand travel.