Respiratory inductance plethysmography (RIP) is a method for evaluating breathing characteristics by measuring the movement of the thorax and abdominal wall. RIP acquires respiratory data via two elastic bands placed around the rib cage (RC) and abdomen (AB), and thus, must be calibrated to provide accurate volume metrics.

There are several methods for RIP calibration, including least square regression and qualitative diagnostic calibration method (QDC), both of which are integrated in our VivoSense® solution for clinical trials and academic research. In VivoSense®, a QDC on a 5-minute resting breathing pattern followed by a volume calibration can provide accurate tidal volume measures. The algorithm calculates the relative contribution of the rib cage and abdomen, from the RIP data, to the overall tidal volume, with tidal volume measured by a flowmeter, pneumotachograph or fixed volume bag. A least squares regression can also be done directly using the flowmeter.

The need for a mask or breathing tube to measure ventilatory flow is an obstacle in studies with athletic training conditions, where movements often cause face masks to move out of place and alter the regular breathing pattern. Our friends at IEEE used VivoSense® and the LifeShirt wearable physiological shirt to develop an adjustment method that does not require flow as a reference for more feasible RIP data collection during exercise.

They concluded that algorithms using a restful breathing phase were more accurate than those without, and the most accurate results were obtained using both RIP bands, rather than with only one band. The researchers found that their reference free adjustment algorithm produced volume differences of up to 0.25 liters when compared to the least squared regression method that requires simultaneous measuring of RIP and flow. Their reference-free calibration algorithm can provide near accurate ventilation measurements outside the laboratory environment, particularly in ambulatory studies.

However, simultaneous calibration of RIP and flow, which would be necessary for pharmaceutical clinical trials, is proven to be the most accurate calibration method for ventilation metrics.

VivoSense provides a world leading solution, integrating RIP and flow data from a spirometer, pneumotachograph or other flowmeter, and then calibrating RIP to provide accurate, repeatable volume measures.

We use this solution to provide pharmaceutical researchers with high quality data solutions that can describe a patient’s longitudinal pulmonary status in clinical, ambulatory, exercise or home settings. VivoSense has supported research and clinical trials at over 500 leading pharmaceutical, research and academic institutions across a wide range of disease and activity states, including sleep disordered breathing, congestive heart failure, chronic obstructive pulmonary disease, Rett Syndrome, Spinal Muscular Atrophy, cystic fibrosis, high altitude climbing and exercise.