Respiratory measurement utilizing a novel laser displacement technique: normal tidal breathing

A novel technique for achieving plethysmography measurements utilizing noncontact laser displacement sensors is described. This method may have utility in measuring respiratory and pulmonary function similar to that of respiratory inductive plethysmography. The authors describe the apparatus and method and provide results of a validation study comparing respiratory excursion data obtained by (1) the laser sensor technique, (2) standard respiratory inductive plethysmography (RIP), and (3) lung volume measurements determined by pressure variations in a control volume. Six healthy volunteers (five female, one male, ages ranging from 19 to 23 years) were measured for tidal breathing excursions simultaneously via all three measurement techniques.

Excellent correlation between the techniques was shown. Pairwise comparisons among all three measurement techniques across all subjects showed intraclass correlation coefficients of 0.995 in each case. These results indicate the laser plethysmograph (LP) system provides results that are, at a minimum, equivalent to those of the RIP at the two sites commonly measured by RIP. Use of the LP system has the potential to provide much more extensive and precise measurements of chest wall function and the respiratory musculature.