The severity of bronchospasm is assessed by forced breathing maneuver that depends on coordination and motivation and is difficult to obtain during severe asthma. The PALIScope may provide an alternative, free of these limitations.
The PALIScope records tidal breath sounds from the chest surface, by a set of 42 microphones that are attached to the patient back. Signals at each sensor are converted to energy at intervals of 0.17 seconds, and presented as a dynamic, single breath image of the lungs. The acoustic energy throughout the breath (that correlates with ventilation) can be calculated for any lung region by integrating the energy over the matching sensor(s). 8 asthmatics (3 males) 32 years of age (range, 19-54) with baseline FEV1 of 60± 24% of predicted. Testing: Auscultation, spirometry and PALIscopic examination, before and 30 min following nebulized 0.5 ml 0.5% salbutamol, and 2 ml ipratropium bromide, 0.25 mg/ml.
FEV1 improved after bronchodilatation by 13±12% (P<0.01) and the corresponding total acoustic energy during tidal breath increased by 29±30% (p=0.02). The individual ratios, FEV1after/FEV1before bronchodilatation tended to correlate with the corresponding ratios of the total acoustic energy, after/before, R=0.68, but this correlation did not reached significance. Interestingly, the acoustic energy wasn’t distributed symmetrically between the lungs and between lung regions. In one patient the left lung shared only 11% of the total energy at baseline and this increased to 21% following bronchodilatation. Images 1-2.
Summation of the acoustic energy of tidal breath during asthma could reflect improvement following bronchodilatation, as could standard forced maneuvers. Furthermore, sounds were markedly asymmetrically distributed during the bronchospastic state and it approached normality after bronchodilation.
By integrating and imaging the acoustic signals and their distribution, the PALIScope provides a simple method to assess the course of asthma. This image does not require maximal maneuver. The PALIScope is a bedside tool that may facilitate monitoring and treatment of asthma in a cost effective manner. Images are shown at: http://www.sheba.co.il/lung-image.
I. Ben-Dov, Deep Breeze Ltd.