SPIROMETRY-BASED METHOD FOR CONTINUOUS MONITORING OF WORK OF BREATHING AND MONITORING DEVICE THEREOF

• US 20090062674A1
• Filed: 09/05/2008
• Published: 03/05/2009
• Est. Priority Date: 09/05/2007
• Status: Active Grant

• Current Assignee: Shenzhen Mindray Bio-Medical Electronics Co., Ltd. (Excelsior Union Ltd.)
• Original Assignee: Shenzhen Mindray Bio-Medical Electronics Co., Ltd. (Excelsior Union Ltd.)
• Inventors: JIN, Wei, YE, Jilun
• Granted Patent: US 8,353,844 B2
• Time in Patent Office: Days
• US Class Current: 600/529
• CPC Class Codes: A61B 5/087 Measuring breath flow
• CPC Class Codes: A61B 5/091 Measuring volume of inspired or expired gases, e.g. to determine lung capacity

Abstract

A spirometry-based device for continuous monitoring of work of breathing (WOB) includes a flow sensor and a respiratory mechanics module connected with the flow sensor. The flow sensor may sample an airway gas flow and an airway pressure when a patient is in a state of inspiration. The respiratory mechanics module may calculate an incremental amount of a gas volume that flows to the patient side in a sampling period, calculate a product of the airway pressure and the incremental amount of the gas volume in the sampling period, and accumulate the product into the WOB.

Claims

1. A spirometry-based method for continuous monitoring of work of breathing in a system having a respiratory mechanics module, the method comprising:

sampling an airway gas flow and an airway pressure by the respiratory mechanics module when a patient side of the system is in a state of inspiration such that the system determines an incremental amount of a gas volume that flows into the patient during a sampling period;

calculating a product of the airway pressure and the gas volume within a current sampling period; and

accumulating the product in each sampling period into a work of breathing (WOB) of the current inspiration.

5. The method according to claim 1, further comprising a step of calculating elastic work in which a tidal volume (VT) and peak inspiratory pressure (PIP) are measured by the respiratory mechanics module under a condition of mechanical ventilation, whereby the elastic work (WOB_elastic) is given by:

$W<br><br><br><br>O<br><br><br><br>B_{\mathrm{elastic}}=\frac{1}{2}<br><br>V<br><br><br><br>T·<br><br>P<br><br><br><br>I<br><br><br><br>P.$

2. The method according to claim 2, further comprising:

repeating the sampling, calculating, and accumulating steps until the current inspiration is finished; and

adopting the last WOB obtained at the end of current inspiration as the total work of breathing (WOB_tot) of the current inspiration.

3. The method according to claim 2, wherein sampling comprises:

obtaining the airway gas flow through a flow sensor at each sampling by the respiratory mechanics module; and

multiplying the gas flow by the sampling period to give the increment of the gas volume within the sampling period.

4. The method according to claim 2, wherein sampling comprises:

allocating a current value of the gas volume to a static variable past_volume; and

adding the incremental amount of the gas volume to the current value of the gas volume to update a value of the gas volume with a sum thereof.

6. A spirometry-based device for continuous monitoring of work of breathing (WOB), comprising:

a flow sensor; and

a respiratory mechanics module connected with the flow sensor;

wherein the flow sensor samples an airway gas flow and an airway pressure when a patient is in a state of inspiration; and

wherein the respiratory mechanics module calculates an incremental amount of a gas volume that flows to the patient side in a sampling period, calculates a product of the airway pressure and the incremental amount of the gas volume in the sampling period, and accumulates the product into the WOB.

7. The device according to claim 6, wherein the respiratory mechanics module and the flow sensor perform the following steps circularly until the end of an inspiratory phase:

sampling a gas flow and airway pressure in a sampling period by the flow sensor when the patient is in a state of inspiration;

calculating an incremental amount of a gas volume that flows to the patient side in the sampling period;

calculating a product of the airway pressure and the incremental amount of the gas volume in the sampling period; and

accumulating the product into the WOB;

wherein the WOB obtained at the end of inspiration is adopted as a present total work of breathing (WOB_tot).

8. The device according to claim 7, wherein the respiratory mechanics module obtains a gas flow through the flow sensor upon the arrival of a next sampling period;

and the respiratory mechanics module multiplies the gas flow by the sampling period to obtain the incremental amount of the gas volume.

9. The device according to claim 7, wherein the respiratory mechanics module loads a current value of the gas volume into a static variable past-volume, and adds the incremental amount of the gas volume to the current value to update the value of the gas volume with the sum thereof.

10. The device according to claim 6, wherein a tidal volume (VT) and peak inspiratory pressure (PIP) are measured by the respiratory mechanics module under a condition of mechanical respiration, and whereby elastic work (WOB_elastic) is calculated as:

$W<br><br><br><br>O<br><br><br><br>B_{\mathrm{elastic}}=\frac{1}{2}<br><br>V<br><br><br><br>T·<br><br>P<br><br><br><br>I<br><br><br><br>P.$

11. A computer-readable medium comprising program code for causing a computer to perform a spirometry-based method for continuous monitoring of work of breathing in a system having a respiratory mechanics module, the method comprising:

sampling an airway gas flow and an airway pressure by the respiratory mechanics module when a patient side of the system is in a state of inspiration such that the system determines an incremental amount of a gas volume that flows into the patient during a sampling period;

calculating a product of the airway pressure and the gas volume within a current sampling period; and

accumulating the product in each sampling period into a work of breathing (WOB) of the current inspiration.

12. An apparatus for continuous monitoring of work of breathing in a system having a respiratory mechanics module, the apparatus comprising:

means for sampling an airway gas flow and an airway pressure by the respiratory mechanics module when a patient side of the system is in a state of inspiration such that the system determines an incremental amount of a gas volume that flows into the patient during a sampling period;

means for calculating a product of the airway pressure and the gas volume within a current sampling period; and

means for accumulating the product in each sampling period into a work of breathing (WOB) of the current inspiration.