Lung classification scheme, a method of lung class identification and inspiratory waveform shapes

• US 6,135,105 A
• Filed: 10/20/1995
• Issued: 10/24/2000
• Est. Priority Date: 10/20/1995
• Status: Expired due to Fees

• Current Assignee: Hyloft
• Original Assignee: University of Florida (State University System of Florida)
• Inventors: Lampotang, Samsun, van Oostrom, Johannes Hugo Maria
• Primary Examiner(s): Lewis, Aaron J.
• Application Number:
  US08/546,301
• Time in Patent Office: 1,831 Days
• Field of Search: 128/204.18, 128/204.21-204.23, 128/204.26
• US Class Current: 128/204.21
• CPC Class Codes: A61M 16/024 including calculation means, e.g. using a processor
• CPC Class Codes: A61M 16/204 used for inhalation control
• CPC Class Codes: A61M 2016/0039 in the inspiratory circuit
• CPC Class Codes: A61M 2016/0413 with detectors of CO2 in exhaled gases
• CPC Class Codes: A61M 2230/432 partial CO2 pressure (P-CO2)

Abstract

A method of ventilating a patient comprises initially determining the class of the lungs of a given patient, selecting a pressure or flowrate inspiratory waveform and other ventilatory parameters like inspiratory pause and inspiratory time, among others, appropriate for that lung class, and then ventilating the patient with the selected inspiratory waveform and other ventilatory parameters. New ventilation inspiratory waveforms are provided which have been found to be advantageous for certain lung classes.

Claims

1. A method of artificially ventilating a patient, comprising:

determining the class of lungs of the patient, the determining of the class of lungs comprising determining whether the patient has lungs with equal individual time constants, lungs of unequal compliance with no restriction on resistance, or lungs with equal compliance and unequal resistance;

selecting an appropriate inspiratory waveform for the particular lung class of such patient; and

ventilating such patient with the selected inspiratory waveform.

2. A method of artificially ventilating a patient, comprising:

determining the class of lungs of the patient, the determining of the class of lungs comprising ventilating the patient with an inspiratory waveform having a first inspiratory time, thereafter ventilating the patient with said inspiratory waveform for a second inspiratory time which is greater than said first inspiratory time throughout a selected period or number of breaths while maintaining tidal volume constant, sensing the end-tidal carbon dioxide concentration of the gas exhaled by the patient following each of said inspiratory waveforms, and comparing said sensed concentration of end-title carbon dioxide;

selecting an appropriate inspiratory waveform for the particular lung class of such patient; and

ventilating such patient with the selected inspiratory waveform.

3. The method of claim 2 in which said step of thereafter ventilating the patient includes thereafter ventilating the patient with said inspiratory waveform for a second inspiratory time which is greater than said first inspiratory time for at least ten breaths or about one minute while maintaining tidal volume constant.

4. A method of artificially ventilating a patient, comprising:

determining the class of lungs of the patient, the determining of the class of lungs comprising ventilating the patient with an inspiratory waveform without inspiratory pause, thereafter ventilating the patient with said inspiratory waveform containing an inspiratory pause while maintaining tidal volume constant for a selected period, sensing the end-tidal carbon dioxide concentration of the gas exhaled by the patient following each of said inspiratory waveforms, and comparing said sensed concentration of end-title carbon dioxide;

selecting an appropriate inspiratory waveform for the particular lung class of such patient; and

ventilating such patient with the selected inspiratory waveform.

5. The method of claim 4 in which said steps of ventilating the patient comprises ventilating the patient with a rising exponential flowrate inspiratory waveform.

6. A method of artificially ventilating a patient, comprising:

determining the class of lungs of the patient, the determining of the class of lungs comprising ventilating the patient with a constant pressure inspiratory waveform having a selected tidal volume and inspiratory time, thereafter ventilating the patient with a rising exponential flowrate waveform having the same tidal volume and inspiratory time as said constant pressure waveform for a selected time period, sensing the end-tidal carbon dioxide concentration of the gas exhaled by the patient following each of said inspiratory waveforms, and comparing said sensed concentration of end-title carbon dioxide;

selecting an appropriate inspiratory waveform for the particular lung class of such patient; and

ventilating such patient with the selected inspiratory waveform.

7. A method of artificially ventilating a patient, comprising:

determining the class of lungs of the patient;

selecting an appropriate inspiratory waveform for the particular lung class of such patient, the selecting of the appropriate inspiratory waveform comprising selecting a quarter-sine (π

/2-π

) flowrate waveform defined as follows;

##EQU6## where;

Q_ett (t)=total flowrate at the trachea or endotracheal tube, over time

VT=tidal volume

T_i =inspiratory volume

t=time; and

ventilating such patient with the selected inspiratory waveform.

8. A method of artificially ventilating a patient, comprising:

determining the class of lungs of the patient;

selecting an appropriate inspiratory waveform for the particular lung class of such patient, the selecting of an appropriate inspiratory waveform comprising selecting a quarter-sine (π

-3 π

/2) flowrate waveform defined as follows;

##EQU7## where;

Q_ett (t)=total flowrate at the trachea or endotracheal tube, over time

VT=tidal volume

T_i =inspiratory volume

t=time; and

ventilating such patient with the selected inspiratory waveform.

9. A method of artificially ventilating a patient, comprising:

determining the class of lungs of the patient;

selecting an appropriate inspiratory waveform for the particular lung class of such patient, the selecting of an appropriate inspiratory waveform comprising selecting a trapezoid flowrate waveform defined as follows;

##EQU8## where;

Q_ett (t)=total flowrate at the trachea or endotracheal tube, over time

VT=tidal volume

T_i =inspiratory volume

t=time; and

ventilating such patient with the selected inspiratory waveform.

10. A method of artificially ventilating a patient, comprising:

determining the class of lungs of the patient;

selecting an appropriate inspiratory waveform for the particular lung class of such patient, the selecting of an appropriate inspiratory waveform comprising selecting a decaying exponential (π

=T_i /n) flowrate waveform defined as follows;

##EQU9## where;

Q_ett (t)=total flowrate at the trachea or endotracheal tube, over time

VT=tidal volume

T_i =inspiratory volume

τ

=time constant of flowrate decay

n=any number

t=time; and

ventilating such patient with the selected inspiratory waveform.

11. A method of artificially ventilating a patient, comprising:

determining the class of lungs of the patient;

selecting an appropriate inspiratory waveform for the particular lung class of such patient, the selecting of an appropriate inspiratory waveform comprising selecting a decaying exponential (τ

=T_i /5) flowrate waveform defined as follows;

##EQU10## where;

Q_ett (t)=total flowrate at the trachea or endotracheal tube, over time

VT=tidal volume

T_i =inspiratory volume

τ

=time constant of flowrate decay

t=time; and

ventilating such patient with the selected inspiratory waveform.

12. A method of artificially ventilating a patient, comprising:

determining the class of lungs of the patient;

selecting an appropriate inspiratory waveform for the particular lung class of such patient, the selecting of an appropriate inspiratory waveform comprising selecting a rising exponential (τ

=T_i /n) flowrate waveform defined as follows;

##EQU11## where;

Q_ett (t)=total flowrate at the trachea or endotracheal tube, over time

VT=tidal volume

T_i =inspiratory volume

τ

=time constant of flowrate decay

n=any number

t=time; and

ventilating such patient with the selected inspiratory waveform.

13. A method of artificially ventilating a patient, comprising:

determining the class of lungs of the patient;

selecting an appropriate inspiratory waveform for the particular lung class of such patient, the selecting of an appropriate inspiratory waveform comprising selecting a rising exponential (τ

=T_i /5) flowrate waveform defined as follows;

##EQU12## where;

Q_ett (t)=total flowrate at the trachea or endotracheal tube, over time

VT=tidal volume

T_i =inspiratory volume

τ

=time constant of flowrate decay

t=time; and

ventilating such patient with the selected inspiratory waveform.

14. A method of artificially ventilating a patient, comprising:

determining the class of lungs of the patient;

selecting an appropriate inspiratory waveform for the particular lung class of such patient, the selecting of an appropriate inspiratory waveform comprising selecting a flowrate waveform defined as follows;

##EQU13## where;

Q_ett (t)=total flowrate at the trachea or endotracheal tube, over time

VT=tidal volume

T_i =inspiratory volume

t=time; and

ventilating such patient with the selected inspiratory waveform.

15. A method of artificially ventilating a patient, comprising:

determining the class of lungs of the patient;

selecting an appropriate inspiratory waveform for the particular lung class of such patient, the selecting of an appropriate inspiratory waveform comprising selecting a flowrate waveform defined as follows;

##EQU14## where;

Q_ett (t)=total flowrate at the trachea or endotracheal tube, over time

VT=tidal volume

T_i =inspiratory volume

t=time; and

ventilating such patient with the selected inspiratory waveform.

16. A method of artificially ventilating a patient, comprising:

determining the class of lungs of the patient;

selecting an appropriate inspiratory waveform for the particular lung class of such patient, the selecting of an appropriate inspiratory waveform comprising selecting a flowrate waveform defined as follows;

##EQU15## where;

Q_ett (t)=total flowrate at the trachea or endotracheal tube, over time

VT=tidal volume

T_i =inspiratory volume

t=time

n=any number; and

ventilating such patient with the selected inspiratory waveform.

17. A method of artificially ventilating a patient, comprising:

determining the class of lungs of the patient;

selecting an appropriate inspiratory waveform for the particular lung class of such patient, the selecting of an appropriate inspiratory waveform comprising selecting a flowrate waveform defined as follows;

space="preserve" listing-type="equation">Q.sub.ett (t)=Ae.sup.at

where;

##EQU16## C_r =right lung compliance C_l =left lung compliance

R_r =right lung resistance

R_l =left lung resistance

VT=tidal volume

Q_ett (t)=total flowrate at the trachea or endotracheal tube, over time

T_i =inspiratory volume

t=time; and

ventilating such patient with the selected inspiratory waveform.

18. A method of artificially ventilating a patient, comprising:

determining the class of lungs of the patient;

selecting an appropriate inspiratory waveform for the particular lung class of such patient, the selecting of an appropriate inspiratory waveform comprising selecting a constant pressure waveform defined as follows;

space="preserve" listing-type="equation">P.sub.c (t)=P.sub.c

where;

P_c is constant during inspiration and is the pressure at the carina which is iteratively adjusted while the constant pressure waveform is maintained until the desired tidal column is obtained

t=time; and

ventilating such patient with the selected inspiratory waveform.

19. A method of artificially ventilating a patient, comprising:

determining the class of lungs of the patient;

selecting an appropriate inspiratory waveform for the particular lung class of such patient, the selecting of an appropriate inspiratory waveform comprising selecting a rising exponential pressure waveform defined as follows;

##EQU17## where;

T_i =inspiratory time

P_o =an arbitrarily set starting point for the pressure waveform which is iteratively adjusted as the pressure waveform is maintained, and as the actually delivered tidal volume is measured, until the desired tidal volume is obtained

P_c =pressure at carina

n=any number

t=time; and

ventilating such patient with the selected inspiratory waveform.

20. A method of artificially ventilating a patient, comprising:

determining the class of lungs of the patient;

selecting an appropriate inspiratory waveform for the particular lung class of such patient, the selecting of an appropriate inspiratory waveform comprising selecting a pressure waveform, t², defined as follows;

##EQU18## where;

T_i =inspiratory time

P_o =an arbitrarily set starting point for the pressure waveform which is iteratively adjusted as the pressure waveform is maintained, and as the actually delivered tidal volume is measured, until the desired tidal volume is obtained

P_c =pressure at carina

t=time; and

ventilating such patient with the selected inspiratory waveform.

21. A method of artificially ventilating a patient, comprising:

determining the class of lungs of the patient;

selecting an appropriate inspiratory waveform for the particular lung class of such patient, the selecting of an appropriate inspiratory waveform comprising selecting a pressure waveform, t³, defined as follows;

##EQU19## where;

T_i =inspiratory time

P_o =an arbitrarily set starting point for the pressure waveform which is iteratively adjusted as the pressure waveform is maintained, and as the actually delivered tidal volume is measured, until the desired tidal volume is obtained

P_c =pressure at carina

t=time; and

ventilating such patient with the selected inspiratory waveform.

22. A method of artificially ventilating a patient, comprising:

determining the class of lungs of the patient;

selecting an appropriate inspiratory waveform for the particular lung class of such patient, the selecting of an appropriate inspiratory waveform comprising selecting a pressure waveform, tⁿ, defined as follows;

##EQU20## where;

T_i =inspiratory time

P_o =an arbitrarily set starting point for the pressure waveform which is iteratively adjusted as the pressure waveform is maintained, and as the actually delivered tidal volume is measured, until the desired tidal volume is obtained

P_c =pressure at carina

n=any number greater than 1

t=time; and

ventilating such patient with the selected inspiratory waveform.

23. A method of artificially ventilating a patient, comprising:

determining the class of lungs of the patient, the determining the class of lungs comprising determining whether the patient has lungs with equal individual time constraints, lungs of unequal compliance with no restriction on resistance, or lungs with equal compliance and unequal resistance;

selecting an inspiratory waveform having an appropriate shape inspiratory time and inspiratory pause for the lung class of such patient; and

ventilating such patient with the selected inspiratory waveform.

24. A method of artificially ventilating a patient, comprising:

determining the class of lungs of the patient;

selecting an inspiratory waveform having an appropriate shape inspiratory time and inspiratory pause for the lung class of such patient, the selecting of an appropriate appropriate inspiratory waveform comprising selecting an inspiratory waveform with zero inspiratory pause for lungs with equal individual time constraints; and

ventilating such patient with the selected inspiratory waveform.

25. A method of artificially ventilating a patient, comprising:

determining the class of lungs of the patient;

selecting an inspiratory waveform having an appropriate shape inspiratory time and inspiratory pause for the lung class of such patient, the selecting of an appropriate appropriate inspiratory waveform comprising selecting an inspiratory waveform with a comparatively short inspiratory time for lungs of unequal compliance with no restriction on resistance; and

ventilating such patient with the selected inspiratory waveform.

26. A method of artificially ventilating a patient, comprising:

determining the class of lungs of the patient;

selecting an inspiratory waveform having an appropriate shape inspiratory time and inspiratory pause for the lung class of such patient, the selecting of an appropriate inspiratory waveform comprising selecting an inspiratory waveform with zero inspiratory pause for lungs of unequal compliance with no restriction on resistance; and

ventilating such patient with the selected inspiratory waveform.

27. A method of artificially ventilating a patient, comprising:

determining the class of lungs of the patient;

selecting an inspiratory waveform having an appropriate shape inspiratory time and inspiratory pause for the lung class of such patient, the selecting of an appropriate inspiratory waveform comprising selecting an inspiratory waveform having an inspiratory pause on the order of about 25% of the inspiratory time for lungs with equal compliance with unequal resistance; and

ventilating such patient with the selected inspiratory waveform.

28. A method of artificially ventilating a patient, comprising:

determining the class of lungs of the patient;

selecting an inspiratory waveform having an appropriate shape inspiratory time and inspiratory pause for the lung class of such patient, the selecting of an appropriate inspiratory waveform comprising selecting an inspiratory waveform with a comparatively long inspiratory time for lungs of equal compliance with unequal resistance; and

ventilating such patient with the selected inspiratory waveform.

29. A method of artificially ventilating a patient, comprising:

determining the class of lungs of the patient;

selecting an inspiratory waveform having an appropriate shape inspiratory time and inspiratory pause for the lung class of such patient, the selecting of an appropriate inspiratory waveform comprising selecting at least one of the flowrate waveforms defined as follows;

##EQU21## Q_ett (t)=total flowrate at the trachea or endotracheal tube, over time

VT=tidal volume

T_i =inspiratory volume

τ

=time constant of flowrate decay

n=any number

f[VT, T_i ]=a constant which is a fraction of VT and T_i

T=time

C_r =right lung compliance

C_l =left lung compliance

R_r =right lung resistance

R_l =left lung resistance; and

ventilating such patient with the selected inspiratory waveform.

30. A method of artificially ventilating a patient, comprising:

determining the class of lungs of the patient;

selecting an inspiratory waveform having an appropriate shape, inspiratory time and inspiratory pause for the lung class of such patient, the selecting of the inspiratory waveform comprising selecting an inspiratory time based at least in part on the effective time constant of the entire respiratory system comprising applying a constant pressure waveform at the carina of the patient through an endotracheal tube with which the patient is intubated and determining the point at which the flowrate at the endotracheal tube, Q_ett (t), is equal to exp (-1)·

Q_max (0.368 Q_max),where Q_max is the maximum inspiratory flowrate, which point is the effective time constant of the entire respiratory system; and

ventilating such patient with the selected inspiratory waveform.

31. A method of artificially ventilating a patient, comprising:

determining the class of lungs of the patient;

selecting an inspiratory waveform having an appropriate shape inspiratory time and inspiratory pause for the lung class of such patient, the selecting of the inspiratory waveform comprising selecting an inspiratory time based at least in part on the effective time constant of the entire respiratory system comprising applying an increasing ramp pressure waveform at the carina of the patient through an endotracheal tube with which the patient is intubated and determining the point at which the flowrate at the endotracheal tube, Q_ett (t), is equal to (1-exp (-1)) Q_max =(1-0.368)Q_max =0.632 Q_max, where Q_max is equal to Q_ett (T_i) and T_i is the inspiratory time, which point is the effective time constant of the entire respiratory system; and

ventilating such patient with the selected inspiratory waveform.