Method and apparatus for determining work of breathing

Claim 2

Apparatus for use in determining the total work of breathing of the human respiratory system, comprising, in combination: Dynamic pressure flow measuring means providing for conduction of gas in and out of such a respiratory system during at least one complete breathing cycle and responding to the pressure of said gas to provide an electrical output signal proportional to flow squared of said gas; adjustable means connected to the output of said dynamic pressure flow measuring means for simulating the total respiratory resistance of said respiratory system to provide a second electrical signal which is a function of said electrical output signal and said total respiratory resistance, integrating means for integrating said second electrical signal with respect to time to provide an electrical value proportional to work of breathing during at least one complete breathing cycle and means for indicating the work of breathing.

Claim 3

The apparatus of claim 1 wherein said dynamic flow measuring means includes a flow element through which said air is conducted, and a pressure differential transducer connected with said flow element, said pressure transducer providing said electrical output signal proportional to said flow squared.

Claim 4

The apparatus of claim 1 wherein said integrating means includes means for scaling the time constant of integration in proportion to the density of the gas breathed.

Claim 5

The apparatus of claim 1 further including means for starting and stopping said integration to provide said integration over at least one complete breathing cycle.

Claim 8

The method of claim 5 wherein said modifying step includes the step of setting a resistance scaling means to scale for predetermined respiratory resistance of said respiratory system; and further including the step of setting a density scaling means to scale for the density of the gas; and wherein said step of determining the value of flow squared includes the steps of conducting gas during one or more breathing cycles through a relatively low resistance dynamic pressure flow element and thereby creating a pressure differential proportional to flow squared and air density, utilizing a pressure transducer to measure said pressure differential and obtain a First electrical signal proportional to gas density and gas flow squared, scaling said signal by utilizing said respiratory resistance and density scaling means to obtain a second electrical signal proportional to respiratory resistance and flow squared; and wherein said integrating step includes the step of integrating said second signal over one or more breathing cycles to obtain a third signal proportional to the work of breathing expended during said one or more breathing cycles.