Photoplethysmography, Fear Conditioning and Arthroplasty—New Citations

In Technology: Photoplethysmography with a Smart Phone

Pulse transit time (PTT) recordings are widely used to make inferences about dynamics of vascular walls and blood pressure variations, parameters useful to the diagnosis of several respiratory conditions.  Chinese researchers have developed a method for noninvasive photoplethysmograhic imaging (PPGi) using the dual cameras of a common smartphone, to estimate PTT. The system works by measuring color input fluctuations from the cameras on two skin regions, the temple and the fingertip, to estimate pulse transit between the regions. The researchers developed an algorithm for detecting PPGi maxima and minima, and compared their data with data recorded using a BIOPAC PPG transducer, fast-response surface temperature transducer, and multi-lead ECG to assess accuracy. The methods and procedures are detailed in the study, which you can read here.

In Psychology: Fear Conditioning in Neurotic Subjects

Psychologists have long been interested in the relationship among emotion, attention and memory. Researchers Hur et al. recently performed a study that detailed interactions of attentional focus, contingency awareness and the effects of neuroticism when exposed to fear conditioning. The study included a questionnaire to assess the subjects’ personality, a classical fear conditioning test, in which participants were subject to mild electric shocks after being exposed to fear-relevant pictures, and physiological data acquisition. A BIOPAC electrical stimulator was used to administer shocks, and skin conductance data was collected with an MP150 and analyzed with AcqKnowledge. The results showed an increased fear-conditioning response in highly neurotic individuals, among other findings. The paper also details physiological occurrences in response to the test. You can read the paper here.

In Surgery: Evaluating Minimally Invasive Knee Replacement

Minimally invasive surgery was previously thought to improve outcomes for total knee arthroplasty (TKA) patients due to reduced trauma to the quadriceps. It is known that the minimally invasive method leads to faster recovery, but the surgery has more inherent risk due to limited vision, and little is known about the long-term benefits. Researchers in Colorado have recently performed clinical trials to assess the outcomes of recipients of both minimally invasive and traditional TKA surgeries via a series of neuromuscular tests, including isometric quadriceps strength, activation, active knee range of motion, and 6-minute walk among others. Muscle torque dynamometry data was collected with a BIOPAC MP150 Data Acquisition system. At both 26 and 52 weeks post-operative, they found no differences in the long term outcomes between groups, suggesting that the benefits may not be worth the added risk of minimally invasive TKA. Read the full article here.