New Respiratory Inductive Plethysmography (RIP) Method for Evaluating Ventilatory Adaptation during Mild Physical Activities.

The pneumotachometer is currently the most accepted device to measure tidal breathing, however, it requires the use of a mouthpiece and thus alteration of spontaneous ventilation is implied. Respiratory inductive plethysmography (RIP), which includes two belts, one thoracic and one abdominal, is able to determine spontaneous tidal breathing without the use of a facemask or mouthpiece, however, there are a number of as yet unresolved issues. In this study we aimed to describe and validate a new RIP method, relying on a combination of thoracic RIP and nasal pressure signals taking into account that exercise-induced body movements can easily contaminate RIP thoracic signals by generating tissue motion artifacts. A custom-made time domain algorithm that relies on the elimination of low amplitude artifacts was applied to the raw thoracic RIP signal. Determining this tidal ventilation allowed comparisons between the RIP signal and simultaneously-recorded airflow signals from a calibrated pneumotachometer (PT). We assessed 206 comparisons from 30 volunteers who were asked to breathe spontaneously at rest and during walking on the spot. Comparisons between RIP signals processed by our algorithm and PT showed highly significant correlations for tidal volume (Vt), inspiratory (Ti) and expiratory times (Te). Moreover, bias calculated using the Bland and Altman method were reasonably low for Vt and Ti (0.04 L and 0.02 s, respectively), and acceptable for Te (<0.1 s) and the intercept from regression relationships (0.01 L, 0.06 s, 0.17 s respectively). The Ti/Ttot and Vt/Ti ratios obtained with the two methods were also statistically correlated. We conclude that our methodology (filtering by our algorithm and calibrating with our calibration procedure) for thoracic RIP renders this technique sufficiently accurate to evaluate tidal ventilation variation at rest and during mild to moderate physical activity

Validity of thoracic respiratory inductive plethysmography in high body mass index subjects

International audienceWe aim to evaluate thoracic Respiratory Inductive Plethysmography (RIP) in high body mass index (BMI) subjects with a pneumotachometer (PT) as a reference. We simultaneously evaluated spontaneous breathing by RIP and PT in 10 low and 10 high BMI subjects at rest and in moderate exercise. We then recorded RIP amplitude with different excursions mimicking respiratory thoracic deformation, with different sizes of RIP belts surrounding cylinders of different perimeters with or without deformable foam simulating adipose tissue. RIP responses correlated with PT values in low and high BMI groups for inspiratory time (r=0.86 and r=0.91, respectively), expiratory time (r=0.96 and r=0.91, respectively) and amplitude (r=0.82 for both) but with a bias (-0.23 +/-0.25L) for high BMI subjects. ANOVA revealed the effects of perimeter and simulated adiposity (p<0.001 for both). We concluded that thoracic perimeter and deformity of adipose tissue are responsible for biases in RIP response in high BMI subjects

Evaluation of Vt, Ti and Te by RIP signals processed by the custom made algorithm.

<p>The linear relationship between Vt determined by PT, and Vt determined by RIP plus the algorithm is shown in the upper left panel. Bland and Altman’s analysis of Vt determined by PT, and Vt determined by RIP plus the algorithm is shown in the upper right panel with bias (long dotted line) and limit of agreements (short dotted line). The linear relationship between Ti determined by PT, and Ti determined by RIP plus the algorithm is shown in the middle left panel. Bland and Altman’s analysis of Ti by PT and by RIP plus the algorithm is shown in the middle right panel with bias (long dotted line) and limit of agreements (short dotted line). The linear relationship between Te determined by PT, and Te determined by RIP plus the algorithm (lower left panel). Bland and Altman’s analysis of Te by PT and Te by RIP signal plus the algorithm (lower right panel) with bias (long dotted line) and limit of agreements (short dotted line).</p

Evaluation of slopes from linear relationships between RIP and PT before and after activity.

<p>Variations in slopes (left panel) ns: not significant. Relationship between slopes before and after activity (right panel) r: Spearman correlation coefficient; p: p-value.</p

Illustration of the experimental setup including RIP thoracic belt, nasal cannula and a polygraph for acquisition of data.

<p>Illustration of the experimental setup including RIP thoracic belt, nasal cannula and a polygraph for acquisition of data.</p

Evaluation of Ti/Ttot and Vt/Ti ratios determined by RIP signals processed by the custom made algorithm.

<p>The linear relationship between Ti/Ttot ratio by PT and the Ti/Ttot ratio by RIP signal treated by the algorithm (upper left panel). Bland and Altman’s analysis of Ti/Ttot ratio determined by PT and Ti/Ttot ratio determined by RIP signal treated by the algorithm (upper right panel) with bias (long dotted line) and limit of agreements (short dotted line). Linear relationship between Vt/Ti ratio determined by PT and the Vt/Ti ratio determined by RIP signal treated by the algorithm (lower left panel). Bland and Altman’s analysis of Vt/Ti ratio determined by PT and Vt/Ti ratio determined by RIP signal treated by the algorithm (lower right panel) with bias (long dotted line) and limit of agreements (short dotted line).</p

Description of the custom made algorithm in 3 steps.

<p>Step 1: recognition of the onset of the respiratory cycle by nasal signal (<b>vertical bars</b>). Step 2: searching for local RIP signal maximums (<b>dark squares</b>). Step 3: searching for local RIP signal minimums (<b>light squares</b>). Illustration of the results after treatment by the algorithm 1(<b>bottom panel</b>): treated signal (<b>dotted line</b>) superimposed on the raw signal (<b>continuous line</b>).</p

Summary of statistical analysis comparing the RIP signal processed by the custom made algorithm with PT.

<p>r: Spearman coefficient of correlation, p: p-value from Spearman coefficient determination, CI: Confidence intervals, SD: Standard deviation.</p