Apparatus and method for non-invasively measuring cardiac output

Apparatus for non-invasive determination of cardiac output comprising:

• an airway conduit adapted for communication with a patient's respiratory system;
• an inspiratory conduit interconnected to said airway conduit;
• an expiratory conduit interconnected to said airway conduit, at least one of said expiratory conduit and said inspiratory conduit including at least one volume-expandable section
• a volume-adjustable deadspace comprising at least one shunt line positioned in fluid communication between said expiratory conduit and said inspiratory conduit, said at least one volume-expandable section being positioned to selectively expand said volume-adjustable deadspace;
• and
• detection apparatus positioned in proximity to said airway conduit for detecting a change in concentration of at least one gas and in gas flow relating to said patient's respiratory system.

Apparatus for non-invasive determination of cardiac output, comprising:

• an airway conduit adapted for communication with a patient's respiratory system;
• an inspiratory conduit interconnected to said airway conduit;
• an expiratory conduit interconnected to said airway conduit;
• a volume-adjustable deadspace comprising a length of conduit in communication with at least said airway conduit, said length of conduit comprising a volume-expandable section;
• and
• detection apparatus positioned in proximity to said airway conduit for detecting a change in concentration of at least one gas and in gas flow relating to said patient's respiratory system.

Apparatus for non-invasive determination of cardiac output, comprising:

• an airway conduit adapted for communication with a patient's respiratory system;
• an inspiratory conduit interconnected to said airway conduit;
• an expiratory conduit interconnected to said airway conduit;
• a volume-adjustable deadspace comprising a selectively length-expandable section in communication between said airway conduit and said expiratory conduit and a selectively length-expandable section in communication between said airway conduit and said inspiratory conduit;
• and
• detection apparatus positioned in proximity to said airway conduit for detecting a change in concentration of at least one gas and in gas flow relating to said patient's respiratory system.

Apparatus for non-invasive determination of cardiac output comprising:

• an airway conduit adapted for communication with a patient's respiratory system;
• an inspiratory conduit interconnected to said airway conduit;
• an expiratory conduit interconnected to said airway conduit:
• a volume-adjustable deadspace comprises an expandable section of conduit in communication between said airway conduit and a source of ventilation gas;
• and
• detection apparatus positioned in proximity to said airway conduit for detecting a chance in concentration of at least one gas and in gas flow relating to said patient's respiratory system.

Apparatus for non-invasive determination of cardiac output, comprising:

• an airway conduit adapted for communication with a patient's respiratory system;
• an inspiratory conduit interconnected to said airway conduit;
• an expiratory conduit interconnected to said airway conduit;
• a volume-adjustable deadspace including an evacuation line connected to said expiratory conduit and a gas releasing structure for evacuating gas from said evacuation line to reduce the volume of said deadspace;
• and
• detection apparatus positioned in proximity to said airway conduit for detecting a change in concentration of at least one gas and in gas flow relating to said patient's respiratory system.

Apparatus for non-invasive determination of cardiac outputs comprising;

• an airway conduit adapted for communication with a patient's respiratory system;
• an inspiratory conduit interconnected to said airway conduit;
• an expiratory conduit interconnected to said airway conduit;
• a volume-adjustable deadspace provided by a tracheal gas insufflation device;
• and
• detection apparatus positioned in proximity to said airway conduit for detecting a change in concentration of at least one gas and in gas flow relating to said patient's respiratory system.

A method for non-invasively measuring cardiac output comprising:

• providing ventilation apparatus for measuring pulmonary gas output of a patient, said apparatus including an airway conduit for contact with a patient's trachea, an inspiratory tube connected to said airway conduit, an expiratory tube connected to said airway conduit and a deadspace connected to said airway conduit;
• placing said airway conduit in fluid communication with a patient's trachea to provide ingress and egress of air therethrough;
• initiating normal breathing in the patient;
• measuring the volume of gas and end-tidal gas concentration for a selected period of ventilation to establish a baseline gas concentration and gas volume output;
• calculating the end-tidal concentration of gas and calculating the concentration of gas over the period of one inhalation and one exhalation;
• calculating the concentration of gas during exhalation and calculating anatomic deadspace;
• determining a correction value for alveolar deadspace from said calculated concentration of gas over the period of one inhalation and one exhalation;
• determining a correction value for parallel deadspace from said calculated end-tidal gas concentration;
• introducing a change in ventilation by directing exhaled gas from the patient into said deadspace of said ventilation apparatus for re-breathing by the patient;
• measuring the change in gas volume and gas concentration during an episode of re-breathing;
• repeating said normal breathing and measuring of said volume of gas and end-tidal gas concentration, and recalculating end-tidal gas concentration, gas concentration over inhalation and exhalation and gas concentration during inspiration;
• redetermining said correction value for parallel deadspace;
• and
• calculating the difference between said baseline gas concentrations and volume of gas output with the detected change in gas concentration and gas volume output following re-breathing.