Method and apparatus for performing a forced expiratory maneuver in an infant
View Patent ↗Disclosed is a method and device for performing forced expiratory maneuver in an infant to assess the infant's pulmonary function. Under this method, the infant's lungs are synchronously inflated to super-atmospheric levels synchronous with the infant's natural tidal inspiration for a plurality of consecutive respiratory cycles. The end-expiratory CO 2 levels in the infant's respiration are measured during the test. When the end-expiratory CO 2 concentration decreases from the baseline by a pre-defined amount, the infant lungs are rapidly inflated to substantially total lung volume and rapidly deflated to produce a maximum forced expiration. The pre-defined amount of change in CO 2 concentration is usually determined by the testing clinician. Typical concentration drop in CO 2 levels, for example, ranges between 4 and 8 mmHg. But the decrease may also be as little as 2 mmHg or as much as 15 mmHg, depending on the testing clinician. The decrease in the end-expiratory CO 2 level of the infant indicates that the infant's respiratory center is sufficiently modified to allow for the measurement.
1. A method of performing a forced expiratory maneuver in an infant comprising the steps of:
a) inflating the lungs of the infant with air synchronously with natural tidal inspiration to a lung volume greater than that reached at the end tidal inspiration for a plurality of consecutive respiratory cycles;
b) monitoring end-tidal CO 2 concentration of the infant's respiration during each respiratory cycle;
c) determining whether the end-tidal CO 2 concentration decreases from a baseline concentration by a pre-defined amount;
d) inflating the infant's lungs to substantially total lung volume after a determination that the end-tidal CO 2 concentration decreases from the baseline concentration by the pre-defined amount; and
e) immediately deflating the infant's lungs to produce a maximum forced expiration.
2. The method of claim 1 wherein the pre-defined amount ranges between 2 mmHg to 15 mmHg.
3. The method of claim 2 wherein the pre-defined amount ranges between 4 mmHg to 8 mmHg.
4. The method of claim 1 wherein the step of determining whether the end-tidal CO 2 concentration decreases from the baseline concentration is performed by a computer.
5. The method of claim 1 wherein the inflation of the infant's lungs to substantially total lung volume comprises the step of inflating the infant's lungs to a pressure of about 30 cm H 2 O.
6. The method of claim 1 wherein said deflating step (e) is performed by compressing the infant's chest and abdomen with an inflatable vest.
7. The method of claim 1 wherein the deflating step (e) is performed by sucking the air out of the infant's lungs using a negative pressure reservoir.
8. A method of performing a forced expiratory maneuver in an infant comprising the steps of:
a) inflating the lungs of the infant with air synchronously with natural tidal inspiration to a lung volume greater than that reached at the end tidal inspiration for a plurality of consecutive respiratory cycles;
b) monitoring end-tidal CO 2 concentration of the infant's respiration during each respiratory cycle;
c) determining whether the end-tidal CO 2 concentration decreases from a baseline concentration by a pre-defined amount;
d) inflating the infant's lungs to substantially total lung volume after a determination that the end-tidal CO 2 concentration decreases from the baseline concentration by the pre-defined amount;
e) immediately deflating the infant's lungs to produce a maximum forced expiration; and wherein steps (a)–(e) are performed by an apparatus in an automated manner.
9. An apparatus for performing a maximum forced expiration maneuver in an infant comprising:
a mask connected to a source of breathable air that delivers the breathable air at super-atmospheric pressure;
a flow sensor in fluid communication with the mask;
a CO 2 sensor in fluid communication with the mask,
an inflatable vest for compressing the infant's thoracic-abdominal region;
a controller configured to receive a first signal from the flow sensor and a second signal from the CO 2 sensor and capable of commanding inflation of the infant's lungs and followed by inflation of the inflatable vest when the CO 2 sensor detects a CO 2 concentration equal to a target concentration of CO 2 ; and
wherein the mask is connected to the source of breathable air via an air conduit comprising
a control valve that is controlled by the controller and wherein super-atmospheric pressure is achieved when the control valve is closed.
10. An apparatus for performing a maximum forced expiration maneuver in an infant comprising:
a mask connected to a source of breathable air that delivers the breathable air at super-atmospheric pressure;
a flow sensor in fluid communication with the mask;
a CO 2 sensor in fluid communication with the mask,
an inflatable vest for compressing the infant's thoracic-abdominal region;
a controller configured to receive a first signal from the flow sensor and a second signal from the CO 2 sensor and capable of commanding inflation of the infant's lungs and followed by inflation of the inflatable vest when the CO 2 sensor detects a CO 2 concentration equal to a target concentration of CO 2 ; and
wherein the controller is an analog switching device.
11. An apparatus for performing a maximum forced expiration maneuver in an infant comprising:
a mask connected to a source of breathable air that delivers the breathable air at super-atmospheric pressure;
a flow sensor in fluid communication with the mask;
a CO 2 sensor in fluid communication with the mask,
an inflatable vest for compressing the infant's thoracic-abdominal region;
a controller configured to receive a first signal from the flow sensor and a second signal from the CO 2 sensor and capable of commanding inflation of the infant's lungs and followed by inflation of the inflatable vest when the CO 2 sensor detects a CO 2 concentration equal to a target concentration of CO 2 ; and
wherein the target concentration of CO 2 is a function of a baseline CO 2 concentration measured during the infant's natural tidal breathing derived by subtracting a pre-defined value from the baseline CO 2 concentration.
12. An apparatus for performing a maximum forced expiration maneuver in an infant comprising:
a mask connected to a source of breathable air that delivers the breathable air at super-atmospheric pressure;
a flow sensor in fluid communication with the mask;
a CO 2 sensor in fluid communication with the mask,
an inflatable vest for compressing the infant's thoracic-abdominal region;
a controller configured to receive a first signal from the flow sensor and a second signal from the CO 2 sensor and cap able of commanding inflation of the infant's lungs and followed by inflation of the inflatable vest when the CO 2 sensor detects a CO 2 concentration equal to a target concentration of CO 2 ;
wherein the target concentration of CO 2 is a function of a baseline CO 2 concentration measured during the infant's natural tidal breathing;
wherein the target concentration of CO 2 is derived by subtracting a pre-defined value from the baseline CO 2 concentration; and
the pre-defined value ranges between 2 mmHg to 15 mmHg.