Method for assessing pulmonary stress and breathing apparatus employing the method
First Claim
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1. A method for assessing pulmonary stress, comprising the steps of:
- connecting a respirating subject to an inspiration/expiration gas flow path;
supplying respiratory gas to said subject'"'"'s respiratory system via said flow path;
measuring pressure in relation to time in one of said respiratory system and said gas flow path; and
assessing pulmonary stress of said subject by determining a profile of said pressure-time relationship of gas in said gas flow path.
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Abstract
In a method for assessing pulmonary stress, a flow of respiratory gas is supplied to the lungs of a subject, an ensuing pressure is measured in relation to time and the pressure-time relationship is analyzed. In this analysis, the profile of the pressure-time relationship is determined. In summary, the profile is straight when no stress is present, is convex when there is a risk for over-distension, and is concave when alveolar units are opened up. Implemented in a breathing apparatus the method can be used to assist an operator in diagnostic and therapeutic considerations in relation to a patient.
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Citations
18 Claims
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1. A method for assessing pulmonary stress, comprising the steps of:
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connecting a respirating subject to an inspiration/expiration gas flow path;
supplying respiratory gas to said subject'"'"'s respiratory system via said flow path;
measuring pressure in relation to time in one of said respiratory system and said gas flow path; and
assessing pulmonary stress of said subject by determining a profile of said pressure-time relationship of gas in said gas flow path. - View Dependent Claims (2, 3, 4, 5, 6)
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7. A breathing apparatus comprising:
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an inspiration/expiration gas flow path adapted for connection to a respirating subject'"'"'s respiratory system;
a gas regulator connected in said gas flow path for regulating respiratory gas flow in said gas flow path;
a pressure gauge for measuring pressure in one of said respiratory system and said gas flow path; and
a control unit connected to said pressure gauge and to said gas regulator for determining a profile of a pressure-time relationship of gas in said gas flow path from said pressure measured by said pressure gauge, and for assessing pulmonary stress and operating said gas regulator dependent on said profile. - View Dependent Claims (8, 9, 10, 11, 12, 13, 14)
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15. A breathing apparatus comprising:
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an inspiration/expiration gas flow path adapted for connection to a respirating subject'"'"'s respiratory system;
a first gas regulator connected in said gas flow path and a second gas regulator connected in said gas flow path for, in combination, regulating respiratory gas flow in said gas flow path;
a pressure gauge connected in one said respiratory system and said gas flow path for measuring pressure of said respiratory gas in said one of said respiratory system and said gas flow path;
a control unit connected to said first gas regulator, said second gas regulator and said pressure gauge for identifying a pressure-time relationship of said respiratory gas in said gas flow path from said pressure measured by said pressure gauge and for analyzing pulmonary stress by determining a profile of said pressure time relationship;
said control unit, in a first phase, operating said first gas regulator and said second gas regulator to provide respiration cycles having an initial tidal volume, an initial respiratory rate, an initial inspiratory time relative to a total respiration cycle time, a constant inspiratory gas flow, an initial oxygen fraction of said respiratory gas, and an initial PEEP value;
said control unit in a second phase operating said first gas regulator and said second gas regulator to progressively increase said PEEP value from said initial PEEP value, and wherein said control unit determines said profile by adapting said pressure-time relationship to a power equation Pao=a*tb+c, wherein Pao is pressure, t is time, and a, b and c are constants, and determining at least the constant b as a determinant for said profile, and wherein said control unit compares the determined constant b to a predefined interval and if b is within said interval, said control unit proceeds to a third phase;
in said third phase, said control unit operating said first gas regulator and said second gas regulator to execute a recruiting maneuver having a specific lung inflation pressure and a specific lung inflation time and wherein said control unit compares the determined constant b to said interval and if b is below said interval, said control unit operates said first gas regulator and said second gas regulator to further progressively increase said PEEP value and repeatedly executes said recruiting maneuver until b is within said interval; and
in a fourth phase, said control unit compares the determined constant b to said interval and operates said first gas regulator and said second gas regulator to progressively decrease said PEEP value until b is within said interval. - View Dependent Claims (16)
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17. A breathing apparatus comprising:
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an inspiration/expiration gas flow path adapted for connection to a respirating subject'"'"'s respiratory system;
a first gas regulator connected in said gas flow path and a second gas regulator connected in said gas flow path for, in combination, regulating respiratory gas flow in said gas flow path;
a pressure gauge connected in one of said respiratory system and said gas flow path for measuring pressure of said respiratory gas in said one of said respiratory system and, said gas flow path;
a control unit connected to said first gas regulator, said second gas regulator and said pressure gauge for identifying a pressure-time relationship of said respiratory gas in said gas flow path from said pressure measured by said pressure gauge and for analyzing pulmonary stress by determining a profile of said pressure time relationship;
said control unit, in a first phase, operating said first gas regulator and said second gas regulator to provide respiration cycles having an initial tidal volume, an initial respiratory rate, an initial inspiratory time relative to a total respiration cycle time, a constant inspiratory gas flow, an initial oxygen fraction of said respiratory gas, and an initial PEEP value;
said control unit in a second phase operating said first gas regulator and said second gas regulator to progressively increase said PEEP value from said initial PEEP value, and wherein said control unit determines said profile by adapting said pressure-time relationship to a polynomial equation Pao=α
+β
*t+γ
*t2, wherein Pao is pressure, t is time, and α
, β and
γ
are constants, and determining at least the constant γ
as a determinant for said profile, and wherein said control unit compares the determined constant γ
to a predefined interval and if γ
is within said interval, said control unit proceeds to a third phase;
in said third phase, said control unit operating said first gas regulator and said second gas regulator to execute a recruiting maneuver having a specific lung inflation pressure and a specific lung inflation time and wherein said control unit compares the determined constant b to said interval and if γ
is below said interval, said control unit operates said first gas regulator and said second gas regulator to further progressively increase said PEEP value and repeatedly executes said recruiting maneuver until γ
is within said interval; and
in a fourth phase, said control unit compares the determined constant b to said interval and operates said first gas regulator and said second gas regulator to progressively decrease said PEEP value until γ
is within said interval.- View Dependent Claims (18)
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Specification