Partial body plethysmograph for measuring human respiratory system impedance

A method of evaluating a respiratory system of a subject, having a body, a neck, legs, and a respiratory system impedance and being supplied with a flow of aft, comprising the steps of:

• enclosing a portion of the subject's body within a container, whereby an air pressure is applied to the portion of the subject enclosed in the chamber and wherein the portion comprises the subject's body below the subject's neck;
• applying pressure signals to the subject within the container, wherein the pressure signals vary the air pressure applied to the portion of the subject enclosed in the chamber;
• measuring the flow of air supplied to the subject;
• measuring the air pressure within the container;
• determining respiratory system impedance data for the subject using the measured air flow and air pressure;
• and
• inversely modeling the respiratory system impedance data into an eight element model using data for input frequencies from about 0.1 Hz to about 9.6 Hz.

A method of evaluating a subject, having a body, a neck, legs, and a respiratory system impedance and being supplied with a flow of air, comprising the steps of:

• enclosing a portion of the subject's body within a container, said container comprising a chamber portion and a neck opening for the subject's neck whereby an air pressure is applied to the portion of the subject enclosed in the chamber and wherein the portion comprises the subject's body below the subject's neck;
• applying pressure signals to the subject within the container, using at least two speakers wherein the pressure signals vary the pressure applied to the portion of the subject enclosed in the chamber;
• measuring the flow of air supplied to the subject;
• measuring the air pressure within the container;
• determining respiratory system impedance data for the subject using the measured air flow and air pressure;
• and
• inversely modeling the respiratory system impedance data into an eight element model.

A method of evaluating a respiratory system of a subject, having a body, a neck, legs, and a respiratory system impedance and being supplied with a flow of air, comprising the steps of:

• enclosing a portion of the subject's body within a container, said container comprising a chamber portion and a neck opening for the subject's neck whereby an air pressure is applied to the portion of the subject enclosed in the chamber and wherein the portion comprises the subject's body below the subject's neck;
• applying pressure signals to the subject within the container wherein the pressure signals vary the air pressure applied to the portion of the subject enclosed in the chamber and wherein the pressure signals comprise pseudo random noise signals having frequency components from about 0.1 Hz to about 128 Hz in about 2 Hz increments;
• measuring the flow of air supplied to the subject;
• measuring the air pressure within the container;
• determining respirator system impedance data for the subject using the measured air flow and air pressure;
• and
• inversely modeling the respiratory system impedance data into an eight element model.

An apparatus for analyzing a respiratory system of a subject, having a body, a neck, legs, and a respiratory system impedance and being supplied with a flow of air, comprising:

• a container for enclosing a portion of the subject's body, said container comprising a chamber portion and a neck opening for the subject's neck, whereby a pressure is applied to the portion of the subject's body enclosed in the chamber;
• a pressure source comprising at least two speakers for generating pressure signals within the container over a predetermined frequency range, wherein the pressure signals vary the pressure applied to the portion of the subject enclosed in the chamber;
• an air flow sensor for measuring the flow of air supplied to the subject and providing a measured air flow value;
• a pressure sensor for measuring the pressure applied to the portion of the subject's body enclosed within said container and providing a measured pressure value and
• a processor connected to said air flow sensor, said pressure sensor and said pressure source, said processor operative to control said pressure source, store the measured air flow value and the measured pressure value, determine the respiratory system impedance of the subject using the measured air flow value and the measured pressure value and generate an eight element model of the subject's respiratory system by inversely modeling the respiratory system impedance.