Patent ID: 9581539
Date: 2017-02-28
CPC Classifications: A61B,G01N

Claim:
1. A device for measuring the consumption of oxygen and the elimination of carbon dioxide by a subject, comprising: an air collecting member for collecting a flow of air, which can be worn by the subject and has passages for air inhaled and exhaled by the subject; a flowmeter that can be associated to the collecting member for emitting signals indicative of the flow rate of air exhaled by the subject; a sampling line connected to the collecting member or to the flowmeter, for sampling a portion of the flow of air exhaled by the subject; a suction pump, with substantially constant capacity, arranged downstream of the sampling line, for drawing the aforesaid portion of flow of air into the sampling line; a mixing chamber interposed in the sampling line, upstream of the suction pump, for collecting and mixing together flows of air exhaled by the subject in a number of breathing cycles; means for sensing the concentration of oxygen, and means for sensing the concentration of carbon dioxide, arranged in the sampling line between the mixing chamber and the suction pump, for measuring the concentration of oxygen and of carbon dioxide in the flow of air that traverses the sampling line downstream of the mixing chamber; a switching valve for switching the intake of the pump between a condition of connection to the sampling line and a condition in which said connection is interrupted and the intake of the pump communicates with a line for intake of air from the environment; an electronic control unit for receiving and processing the signals emitted by said flowmeter, by said means for sensing the concentration of oxygen, and by said means for sensing the concentration of carbon dioxide in order to obtain an average measurement of the consumption of oxygen by the subject in the course of a number of breathing cycles; said electronic control unit being moreover provided for controlling said switching valve in a PWM mode in order to simulate a capacity of the suction pump that varies in proportion to the variation of the flow during the breathing cycle so as to render measurement of the consumption of oxygen reliable, even though the mixing chamber does not receive the entire flow exhaled by the subject, wherein said device further comprises: a bypass line parallel to the mixing chamber, through which the flow of air can pass without passing through the mixing chamber, said bypass line merging again into the sampling line upstream of the aforesaid sensor means; a valve for selecting a measuring mode, which can be displaced selectively into two different positions, to cause the flow of air that traverses the sampling line to converge either through the mixing chamber, when an average measurement is to be made of the consumption of oxygen by the subject in the course of a number of breathing cycles, or through said bypass line, when an instantaneous measurement is to be made of the consumption of oxygen by the subject in each breathing cycle, wherein said electronic control unit is configured to control said switching valve so that said pump is kept constantly connected to the sampling line when the aforesaid instantaneous measuring mode is selected, and wherein said sampling line includes a tube having a wall permeable to humidity to keep the humidity within the sampling line substantially equal to ambient humidity, said device further comprising: first humidity-sensing means for sensing the humidity of the flow of air within the sampling line; and second humidity-sensing means, adapted to detect the humidity of the ambient air, said electronic control unit being provided for comparing the values of humidity measured by said first and second humidity-sensing means and for activating an alarm signal when the difference between said values exceeds a pre-set threshold indicating the need to replace said tube with permeable wall defining said sampling line.