2006 OPEN FORUM Abstracts
Variable Resistance Modeling in a High Flow Nasal Cannula (HFNC) Delivery System with Pressure Limitation
Mitchell
R Goldstein, MD1,2,3,
Martin Sandoval1, Linda L Yang, MD1,2,3, Kristen
Hougland, MD1,2,3, Perpetua Lawas-Alejo, MD1,2,3, Bruce D
Sindel, MD1,2,3, Mita Shah, MD1,2,3, Gilbert I Furman, MD1,2,3,
Clark G Ochikubo, MD1,2,3 and Gilbert I Martin, MD1,2,3. 1Neonatal
Medicine, Pomona Valley Hospital Medical Center, Pomona, CA; 2Neonatal
Medicine, Citrus Valley Medical Center, West Covina, CA and 3Western
University Health Sciences, Pomona, CA.
Background: The use of HFNC
simulating Nasal Continuous Positive Airway Pressure (NCPAP) is widely used in
neonatal practice. NCPAP can be altered by varying flow states. This
relationship can be affected by patient leak, size of the cannula, and patient
minute ventilation. Resistance is an important consideration in the actual
propagation of the pressure effect and in excess may precipitate ventilation
failure. We asked if the flows generated
under HFNC with pressure limitation could be quantified for idealized flow
rates producing minimal resistance.
Methods: Using a wall flow meter,
flows from 1-8 lpm QWall were entrained through a T-connector to a
water column at 10 cm H2O and to a distal nasal cannula (AirlifeTM Nasal Oxygen Cannula # 001312) that was submerged to depths from 1-10 cm H2O
∆P = 10-PCannula). Flows QS to the distal cannula
were measured and used to calculate Resistance (R) (cmH2O/L/s)
according to the relationship R = ∆P/QS.
Results: As
shown in the diagram, HFNC flows delivered with pressure limitation produced
variable resistance. A relationship exists between resistance, pressure
delivered at the cannula, and wall flow as derived in the equation.
Conclusion:. HFNC can be optimized by
recognizing catheter characteristics that produce the lowest possible
resistance values at with ideal flow propagation. Using different catheters with
varied resistance profiles may enhance the possibility of success with this
modality.
