IONTOPHORESIS AND CONDUCTIVITY ANALYSIS CIRCUIT

• US 3,794,910 A
• Filed: 07/26/1971
• Issued: 02/26/1974
• Est. Priority Date: 07/26/1971
• Status: Expired due to Term

• Current Assignee: Sherwood Medical Company (Medtronic Plc)
• Original Assignee: Donald A. Ninke, James F. Lahay
• Inventors: Ninke, Donald A., LaHay, James F.
• Primary Examiner(s): Smith, Alfred E.
• Assistant Examiner(s): Hille, Rolf
• Application Number:
  US05/166,284
• Time in Patent Office: 946 Days
• Field of Search: 324/3R,3B,29,62,57PI,131,132 128/2.1R
• US Class Current: 324/442
• CPC Class Codes: A61B 5/4266 sweat secretion
• CPC Class Codes: A61N 1/30 Apparatus for iontophoresis, i.e. transfer of media in ionic state by an electromotoric force into the body, or cataphoresis
• CPC Class Codes: Y10S 128/908 Patient protection from electric shock

Abstract

An iontophoresis inducing circuit includes means to limit to a safe value and to control a generated direct current for connection to iontophoresis electrides on a patient in order to produce sweat. A sweat sample is collected and analyzed to detect for cystic fibrosis. A sweat analysis circuit includes solid state switching for passing current of continuously alternating polarity through the sweat sample, and nonlinear means for converting the current into a direct reading of milliequivalents of sodium chloride per liter.

Claims

1. A circuit for analyzing the concentration of sodium chloride in a sample of sweat from a patient for detecting cystic fibrosis comprising:

means for generating a current proportional to the conductivity of the sample;

indicator means having a scale with indicia directly readable in milliequivalents of sodium chloride per unit measure of volume of sweat; and

circuit means coupled between said generating means and said indicator means for supplying current to said indicator means in response to said proportional current, said circuit means including non-linear means connected to said indicator means to reduce the nonlinearity of said current supplied to said indicator means with respect to the concentration of sodium chloride in the sample over a current range corresponding to the most clinically significant range for detecting cystic fibrosis, said scale indicia being correlated with said current supplied to said indicator means to provide readings in said clinically significant range.

2. The circuit of claim 1 wherein said nonlinear means comprise at least one unidirectional conduction device having a semiconductor junction.

3. The circuit of claim 1 wherein said generating means includes a source of AC, solid state means coupled to said AC source causing a current which continuously alternates in polarity to flow in a first circuit path which includes said sample at a substantially constant voltage value, said circuit means including solid state means coupled between said first circuit path and said indicator means for converting the current of continuously alternating polarity into a direct current, and said indicator means being responsive to direct current.

4. The circuit of claim 3 wherein said solid state converting means includes full wave rectifying means for producing full wave rectified direct current from the current flowing in said first circuit path.

5. The circuit of claim 1 wherein said scale indicia are substantially equally spaced over said range of milliequivalents, and said scale includes numbers directly reading in milliequivalents of sodium chloride per unit measure of volume of sweat.

6. The circuit of claim 5 wherein said current generating means include a source of alternating current and a full-wave rectifier connected to pass alternating current through said sample of sweat and full-wave rectified current through said non-linear means and said indicator means.

7. A circuit for analyzing the concentration of sodium chloride in a sample of sweat from a patient for detecting cystic fibrosis comprising circuit means including voltage supply means, a pair of spaced electrodes coupled to said supply means for passing current through a sample of sweat, and voltage dropping means coupled to said electrodes and said supply means for providing a voltage drop across the voltage dropping means proportional to the conductivity of the sample of sweat, a meter indicator having a scale with indicia thereon for directly reading sodium chloride milliequivalents per unit volume of sweat, and means coupling said voltage dropping means to said meter indicator including non-linear means to supply current to said meter indicator which is non-linear with respect to said voltage drop to thereby reduce the non-linearity of said meter indicator current with respect to the concentration of sodium chloride in the sample over a range of current values corresponding to the most clinically significant range for detecting cystic fibrosis, said indicia being correlated with said meter indicator current and substantially equally spaced over said clinically significant range.

8. The circuit of claim 7 wherein said voltage supply means includes a source of alternating current for passing alternating current through the sample of sweat, said voltage dropping means comprises resistance means connected in series circuit relation with said electrodes and said supply means, and said non-linear means is connected in series with said meter in parallel circuit relation with said resistance means.

9. The circuit of claim 8 wherein said circuit means further includes solid state rectifier means coupled between said meter and said electrodes whereby said meter current is rectified.

10. The circuit of claim 9 wherein said rectifier means is a full-wave rectifier connected in series circuit relation with said electrodes to pass alternating current from said supply means to said electrodes and pass full-wave rectified current through said meter.