1. Measuring Functional Residual Capacity of Ventilated Neonates
Advisor: Dr. Bill Walsh
Doug Anderson
David Lammlein
Janine McKinnon

2. Background
The Division of Neonatology at Vanderbilt Children’s Hospital has an interest in determining the Functional Residual Capacity (FRC) in neonates who are mechanically ventilated
Methods must be simple, non-invasive, and allow free access to neonates
Method must be employed in the Neonatal Intensive Care Unit (NICU) which includes 60 intensive and intermediate beds, a 3 bed ECMO unit, and 10 bed intensive care nursery

3. Functional Residual Capacity (FRC)
Functional Residual Capacity (FRC) of the human lung is the volume remaining in the lungs at resting expiratory level
Equivalent to the alveolar volume (Va) which contains 60-70% of the total lung volume
Normal FRC in adults is 1.8 to 3.4 L
Estimated FRC in healthy neonates 5 to 12 mL

4. Mechanical Ventilation in Neonates
The most common admitting diagnosis to the NICU is respiratory distress
Indications for Mechanical Ventilation
Hypoxemia/cyanosis from lung disease (inadequately treated with supplemental O2 alone or with CPAP—continuous positive airway pressure)
Hypoventilation or frank apnea
Increased work of breathing
Severe systemic disease especially with circulatory failure, requiring airway control
Determination of Ventilator Settings
X-rays can be used to help determine PEEP and O2 saturation levels
Have I optimized the lung volumes?
Is the lung volume the cause for low O2?
Trial and error from years of experience is used to make adjustments to get sufficient oxygenation

5. Extracorporeal Membrane Oxygenation (ECMO)
ECMO is used when a ventilator does not provide sufficient oxygen or remove enough carbon dioxide.
ECMO is a form of long-term heart-lung bypass used in infants, children, and adults in cardiac and/or respiratory failure despite maximal medical treatment
Similar to heart-lung bypass used in the operating room
Essentially all the blood is pumped out of the body and run through
artificial heart-lung machine to oxygenate and then it is returned
to the body
Babies are at a greater risk for death because the process
constitutes 20% mortality
Respiratory failures for infants include:
Acute Respiratory Distress Syndrome (ARDS)
Pneumonia
Sepsis
Congenital Diaphragmatic Hernia (CDH)
Pulmonary Hypertension
Inborn Errors of Metabolism
ECMO takes over the work for the lungs so they can rest and heal

6. Problem Description Problems Solution Medical/Research Benefits
Too small a FRC can result in the inability to oxygenate blood and possibly death if blood entering the lung actually exits the lung without coming into contact with an exchangeable gas surface—shunting
Current trial and error methods used to adjust ventilator settings can cause too much PEEP or CPAP which in turn can cause barotraumas, preventing the blood from going into the lung
Solution
Design a device that measures FRC in neonates
Medical/Research Benefits
Can allow doctors and researchers to optimize ventilator settings so as to prevent this sort of shunting or to prevent over oxygenation of neonates coming in at 100% O2 with air in lungs
Can also allow physicians to utilize appropriate methods to facilitate breathing in neonates suffering from lung pathologies, and specifically allows physicians to assess the need for ECMO

7. Measuring FRC Helium Dilution Method Nitrogen Washout Method
Inspiration of known [He]
Gas in lungs dilutes He and [He] drops
Gases equilibrate
Measure difference in [He] to determine initial lung volume
Nitrogen Washout Method
Unknown FRC contains about 78% N2 and an unknown amount of O2 and CO2
Washout N2 by breathing 100% O2
Exhale so that expired [N2] falls between 1 and 1.5%

8. Our Model
A Method for Measuring Functional Residual Capacity in Neonates with Endotracheal Tubes
Schwartz JG, Fox WW, Shaffer TH. A Method for Measuring Functional Residual Capacity in Neonates with Endotracheal Tubes. IEEE Trans. On Biomed. Engineering. 25(3): May.
FRC measured by dilution in the first equation…second equation provides an estimator of final concentration to use in the first equation

9. The Device

10. Reported Results In Vitro In Vivo
Confirmed expected exponential relationship
Real vs. Calculated: r = 0.995, p<0.001
In Vivo
Used in infants as small as 600 g
CPAP (cm H2O) 3
FRC
22.0  1.9
25.8  1.4 N 15 30

11. Evita 4 Ventilator

12. Collins Helium Analyzer
Thank Dr. Lindstrom

13. Millipore Peristaltic Pump
Thank Dave Kwartowitz / Dr. Paschal

14. Advantages Easy to set up Uses common equipment
Can be used for a large range of infants
Useable with both CPAP and ventilator support
Relatively inexpensive

15. Limitation Breathing rate and tidal volume assumed constant
No calculation if minute ventilation (respiratory rate X tidal volume) changed by more than 25% over measurement period
This should not be an issue in our use since the ventilator will control the minute ventilation.
Obstructive diseases may delay equilibration

16. Assembling Prototype Completed: Current and Future Work
Compiled list of necessary supplies and equipment
Either procured or obtained access to almost all necessary items, contacts: Chris Lynn, Dan Lindstrom
Current and Future Work
Assemble and test prototype
Refine and upgrade prototype

17. Supplies and Equipment
Inexpensive Purchaseables
Medical grade tubing
Valves and stopcocks
Anesthesia bag
Solenoid Valve
VUMC Equipment
Heliox gas
Air Pumps
Helium Meter

18. Design Goals Use primarily existing equipment
Avoid complicated, dangerous, or invasive procedures
Allow for uncooperative nature of infants
Mobility of device
Continued free access to neonate

19. Market Potential Clients: Neonatal Intensive Care Units
Because the device can assess the need for ECMO, it has the potential to save hospitals thousands of dollars
Standard Ventilation  $2000/day (Vanderbilt University Hospital)
ECMO  $5000/day (Vanderbilt University Hospital)
Can also save cost because optimal ventilator settings lead to maximum oxygenation which should help curing of lung pathologies
Competitors: No current patents exist on this exact device; however, other more costly methods (i.e. tomography, ultrasonic flow meter) exist.
Production: Creating simple modification to existing equipment will result in lower production costs and overhead.

20. Social Impact
Profound: Families and friends of critically ill neonates
Minimal: Environment, helium is an inert gas

21. References
Schwartz JG, Fox WW, Shaffer TH. A Method for Measuring Functional Residual Capacity in Neonates with Endotracheal Tubes. IEEE Trans. On Biomed. Engineering. 25(3): May.
Journal of Applied Physiology. 73(1): July.
Pediatric Pulmonology. 23(6): June.

22. Questions