• Define HFT and how it is accomplished with a nasal cannula

• Explain how the dynamics of flow through the nasopharynx improve respiratory efficiency and support work of breathing

2

• Explain the properties of Heliox gas mixture and how heliox can be beneficial in the respiratory system

• Understand how the characteristics of HFT facilitate the breathing of heliox via a nasal cannula

• Understand the patient population that can benefit from heliox HFT

A Review of the HFT and Mechanisms of Action

3

Heliox andHeliox via HFT

4

High Flow Nasal Cannula

Generic term for flow rates that exceed conventional nasal cannula flow rates

High Flow Therapy

•Exceed a patients inspiratory flow demand •Flushes out the anatomical dead space, thus creating

an internal reservoir

HFT is between 25 – 35 L/min in adults, or 4-8 L/min in infants

5

Nasopharynx

Prior to reaching alveoli, gas must be:

• Warmed

• Humidified

• Cleaned

6

Nasopharyngeal Structure

• Non-respiratory anatomical dead space

• Impacts breathing efficiency

• Provides challenges to conventional non-invasive respiratory support

7

Fresh atmospheric gas mixes with

end-expiratory gas

End-expiratory gas is

low in oxygen and high in carbon

dioxide

Alveolar gases are different

from atmospheric

8

Nasopharynx•Cleaning•Warming •HumidificationConducting

Airways

9

Reduced anatomical dead space

compensates for increased

physiological dead space

Flushing reduces anatomical dead space

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• Importance in conditioning of breathing gases to body temperature and saturated with water vapor.

• An effective tool to support spontaneous breathing that goes beyond conventional nasal cannula.

• Works with your body’s respiratory anatomy and physiology to improve breathing efficiency through basic mechanisms.

• A non-invasive means of respiratory support that is simple to apply and improves patient comfort.

Key supporting literature includes:•Dysart et al. Respir Med 2009;103: 1400-1405 •Frizzola et al, Pediatr Pulmonol 2011;46:67-74 12

Further education and information surrounding the Mechanisms of Action of High Flow Therapycan be found at:Vapotherm website (http://www.vtherm.com)Highflow website (http://www.highflow.org)

Helium was discovered in the late 19th century.

It is a biologically inert, noble gas that has many useful applications due to its physical properties such as low molecular weight and low density.

When mixed with oxygen for breathing applications to replace nitrogen as the balance or carrier gas, we have what’s know as heliox.

Dr. Barach began studying and advocating the use of Heliox for medical purposes in the 1930’s.

The low density of Helium is the physical property which makes Heliox ideal for certain medical applications.

1.293

0.179

1.429

0.429

1.251

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6D

ensi

ty (g

/L)

* 79% helium and 21% oxygen, commonly known as 80 /20 heliox

Air Helium Oxygen Heliox*Nitrogen

Heliox decreases RAW in areas of turbulent flow

How and where does a lower density gas reduce RAW?

Re= Reynolds Numberρ = densityν = velocityr= radius

η = viscosity

Laminar Flow occurs at Re < 2000Turbulent Flow occurs at Re > 2000

vr

Re

Area of greatest effectArea of obstruction

Net offset in RAW and WOB

Inhalation: Better tidal volume + distribution =

Oxygenation

Key Applications Benefits

Asthma (severe) Reduced airway resistance (improved laminar flow, lower density) Reduced work of breathing

Acute upper airway obstruction Improved tidal volumes

Croup Reduced insp/expiratory ratios

COPD exacerbations Increased C02 clearance

Vent weaning Improved homogeneity of gas distribution

Pulmonary Rehabilitation Improved exercise tolerance

Aerosol drug delivery Better deposition

Mechanics and energetics of breathing helium in infants with bronchopulmonary

dysplasia

Wolfson et al. J Pediatr 1984, 104(5): 752-7

Mechanics study showing:

•Decrease pulmonary resistance and work of breathing•Reduced risk of respiratory muscle fatigue

Growth and development in a heliox incubator environment: a long-term safety

study

Singhaus et al. Neonatology 2007, 91(1):28-35

•rabbits pups raised in heliox environment compared to controls. •No difference in growth parameters or developmental milestones

Heliox attenuates lung inflammation and structural alterations in acute lung injury

Nawab et al. Pediatr Pulmonol 2005;40:524-32 42

•Lung morphology showed improved distribution of heliox gas through the lung

•Pro-inflammatory mediators and matrix remodeling proteins levels were significantly lower with heliox versus nitrogen-oxygen mix

Blinded, RCTs in Acute AsthmaHeliox versus air-oxygen

Author / Data # Patients

Key Findings

Rose 2002 36 Less dyspnea

Kress 2002 45 Improved FEV1

Kudukis 2002 18 PP, PEFR and DI improved

Carter 1996 11 FEF25-75 and PEFR%

Henderson 1999

205 PEFR% improved

All in favor of Heliox

Prospective Randomized crossover trial with heliox in COPD (n = 19)

Jolliet et al. Crit Care Med. 1999 Nov;27(11):2422-9

Heliox compared to air-oxygen

•↓ Inspiratory / total time ratio (p < 0.05)•↑ PIFR (p < 0.01)•↓ PaCO2 (p < 0.01) and Dyspnea (p < 0.05)

• Cannula gas flow should exceeds a patient’s spontaneous inspiratory flow rate to inhale the precise gas mixture

• The nasopharynx becomes an internal reservoir of heliox.

• The effects of helium is not hampered by the entrainment of room air.

• The therapeutic affect can be achieved using the minimally invasive interface.