Sentence:  In the lower center rack an 8 - channel recorder indicates the percentage of carbon dioxide and nitrogen from the upper and lower lobes of one lung , the total volume of inhalation per breath , the flow of air from both lobes , and the <WSD>pressure</WSD> of the two lobes with respect to each other . 
Meaning of the word marked with <WSD> tags:  the force applied to a unit area of surface; measured in pascals (SI unit) or in dynes (cgs unit)