Method of maintaining constant arterial PCO2 and measurement of anatomic and alveolar dead space

• US 6,799,570 B2
• Filed: 04/30/2002
• Issued: 10/05/2004
• Est. Priority Date: 05/04/2001
• Status: Expired due to Fees

• Current Assignee: Alex Vesely, Hiroshi Sasano, Joseph Fisher, Ronald Somogyi, Steve Iscoe
• Original Assignee: Alex Vesely, Hiroshi Sasano, Joseph Fisher, Ronald Somogyi, Steve Iscoe
• Inventors: Vesely, Alex, Fisher, Joseph, Somogyi, Ronald, Sasano, Hiroshi, Iscoe, Steve
• Primary Examiner(s): Bennett, Henry
• Assistant Examiner(s): PATEL, MITAL B
• Application Number:
  US10/135,655
• Publication Number:
  US 20020185129A1
• Time in Patent Office: 889 Days
• Field of Search: 128/204.18, 128/204.21, 128/204.22, 128/204.23, 128/204.26, 128/204.28, 128/204.29, 128/205.13, 128/205.17, 128/205.24, 128/205.11, 128/200.22, 128/200.24, 128/203.12, 128/203.13, 128/203.28, 128/205.18, 128/910, 128/911, 128/203.25, 128/914
• US Class Current: 128/200.24
• CPC Class Codes: A61B 5/0836 Measuring rate of CO2 production
• CPC Class Codes: A61B 5/087 Measuring breath flow
• CPC Class Codes: A61B 5/4821 Determining level or depth of anaesthesia A61B5/1106 takes precedence
• CPC Class Codes: A61M 16/12 by mixing different gases
• CPC Class Codes: A61M 16/208 Non-controlled one-way valves, e.g. exhalation, check, pop-off non-rebreathing valves
• CPC Class Codes: A61M 2202/0007 introduced into the body
• CPC Class Codes: A61M 2202/0225 Carbon oxides, e.g. Carbon dioxide
• CPC Class Codes: Y10S 128/914 Rebreathing apparatus for increasing carbon dioxide content in inhaled gas

Abstract

A method to maintain isocapnia for a subject. A fresh gas is provided to the subject when the subject breathes at a rate less than or equal to the fresh gas flowing to the subject. The fresh gas flow equal to a baseline minute ventilation minus a dead space gas ventilation of the subject contains a physiological insignificant amount of CO₂. An additional reserve gas is provided to the subject when the subject breathes at a rate more than the fresh gas flowing to the subject. The reserve gas has a partial pressure of carbon dioxide equal to an arterial partial pressure of carbon dioxide of the subject. A breathing circuit is applied to the method to maintain isocapnia for a subject. The breathing circuit has an exit port, a non-rebreathing valve, a source of fresh gas, a fresh gas reservoir and a reserve gas supply.

Claims

1. A method of setting up a fresh gas flow equal to baseline minute ventilation minus anatomical dead space ventilation, comprising:

having a subject breathing on a breathing circuit;

providing a fresh gas flow equal to a baseline minute ventilation of the subject;

gradually decreasing the fresh gas flow provided to the breathing circuit with a decrement small enough to avoid affecting an arterial PCO₂ of the subject; and

obtaining an inflection point at which the arterial PCO₂ suddenly rises exponentially, and the inflection point reflecting the fresh gas flow equal to baseline minute ventilation minus anatomical dead space.

2. The method of claim 1, further comprising a step of having the subject breathing on a rebreathing circuit.

3. The method of claim 1, further comprising a step of having the subject breathing on a non-rebreathing circuit.

4. The method of claim 1, further comprising a step of having the subject breathing on a portable breathing circuit.

5. The method of claim 1, further comprising a step of gradually increasing the fresh gas flow with a decrement of about 200 mL/minute.

6. The method of claim 1, further comprising a step of obtaining the baseline minute ventilation with the fresh gas flow at the inflection point.