Arrangement for the determination of the effective pulmonary blood flow

• US 6,394,962 B1
• Filed: 08/14/2000
• Issued: 05/28/2002
• Est. Priority Date: 09/28/1996
• Status: Expired due to Fees

• Current Assignee: Technische Universitat Munchen
• Original Assignee: Technische Universitat Munchen
• Inventors: Albrecht, Detlev Michael, Gama De Abreu, Marcelo
• Primary Examiner(s): Shaver, Kevin
• Assistant Examiner(s): Natnithithadha, Navin
• Application Number:
  US09/638,996
• Time in Patent Office: 652 Days
• Field of Search: 600/529,532
• US Class Current: 600/529
• CPC Class Codes: A61B 5/029 Measuring or recording blood output from the heart, e.g. minute volume A61B8/065 takes precedence

Abstract

The invention relates to a device to determine effective pulmonary blood flow (PBF) by means of partial CO₂ rebreathing. The device is characterized in that it comprises an endotracheal tube whose conduit leading from the patient to the respirator is divided up into two lanes between a controllable three-way valve (4) and a Y-piece; one lane builds a larger dead area (6) for CO₂ rebreathing whereby, in order to measure CO₂ elimination and end expiratory partial CO₂ pressure a CO₂ sensor (3) and a respiration flow sensor (1) are provided on the endotracheal tube of the patient. The calculation of effective pulmonary blood flow is provided by a microprocessor/controller (7) which also controls the three-way valve (4) which provides the switching between both lanes.

Claims

1. Arrangement for the determination of the effective pulmonary blood flow by means of partial CO₂ rebreathing characterized in that

the line from the endotracheal tube of the patient (tube) to the respirator between a controllable 3-way valve (4) and a Y-fitting (5) is split into two branches,

one branch forms a bigger dead space (6) for the CO₂ rebreathing whereby for measurement of the CO₂ elimination and expiration termination CO₂ partial pressure a CO₂ sensor (3) and a respiratory flow sensor (1) at the endotracheal tube of the patient and for calculation of the effective pulmonary blood flow a microprocessor/controller (7) is provided,

the switching between the two branches is carried out by the 3-way valve (4) that can be controlled through the microprocessor/controller (7),

the calculation of the effective pulmonary blood flow is performed using the equation $\mathrm{PBF}=\frac{({V}_{}}{}$

CO2

(NR)-V

CO2

(R))f

(Pet

CO2

(R),Pet

CO2

(NR),Hb)×

Fs,

whereby

VCO₂(NR) is the CO₂ elimination (ml/min) during the nonrebreathing period measured as the mean value of the CO₂ elimination of complete respirations within 60 s until immediately before the beginning of the rebreathing period,

PetCO₂(NR) is the expiration termination CO₂ partial pressure (mmHg) in the respiratory air during the rebreathing period measured as the mean value of the expiration termination CO₂ partial pressures of complete respirations within 60 s until immediately before the beginning of the rebreathing period,

VCO₂(R) is the CO₂ elimination (ml/min) during the rebreathing period measured as the mean value of the CO₂ elimination of complete respirations within 15 to 30 s after the patient has begun to be respired through the big dead space (6) (after switching the 3-way valve (4) into the rebreathing position),

PetCO₂(R) is the expiration termination CO₂ partial pressure (mmHg) in the respiratory air during the rebreathing period measured as the mean value of the expiration termination CO₂ partial pressures of complete respirations within 15 to 30 s after the patient has begun to be respired through the big dead space (6) (after switching the 3-way value (4) into the rebreathing position),

Fs is a scale factor for the representation of the effective pulmonary blood flow in l/min with Fs=10,

PBF is the effective pulmonary blood flow (l/min) whereby

f(PetCO₂(R), PetCO₂(NR), Hb) is the standardised CO₂ dissociation curve in blood and is calculated by inserting the measured values into the equation

2. Arrangement to claim 1 characterized in that the volume of the dead space (6) is 100, 200, 300, 400 or 500 ml.

3. Arrangement to claim 1 or 2 characterized in that the respiratory flow sensor (1) is inserted into the line at the endotracheal tube of the patient (tube).

4. Arrangement to claim 1 or 2 characterized in that the CO₂ sensor (3) is an infrared sensor.

5. Arrangement to claim 4 characterized in that the infrared sensor is positioned in a CO₂(2) cuvet.

6. Arrangement to any of claims 1 or 2 characterized in that the dead space (6) is an exchangeable tube or cylinder.