Vapotherm: High Flow Therapy
High Flow Therapy:
Mechanisms of Action
Heather Knez MHA, RRT-NPS
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Vapotherm: High Flow Therapy
Learning Objectives
• Understand the reason for limiting conventional nasal cannula therapy
to low flows
• Define HFT and how it can be accomplished with a nasal cannula
• Explain why inspiratory gas reaching the lungs is different from
ambient gas
• Understand how the structure of the nasal pharynx and the mucosa
tissue makes this region so efficient at conditioning inspiratory gas
• Understand why oxygen is more harmful to mucosal tissues than room
air
• Explain how the dynamics of flow through the nasopharynx improve
respiratory efficiency and support work of breathing
• Explain how gas delivered at BTPS promotes better respiratory
mechanics and decreases energy cost of gas conditioning
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Vapotherm: High Flow Therapy
Introduction
capillary
O2
CO2
alveoli
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Vapotherm: High Flow Therapy
Introduction
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Vapotherm: High Flow Therapy
Introduction
Prior to reaching
alveoli, gas must be:
Nasopharynx
• Warmed
• Humidified
• Cleaned
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Vapotherm: High Flow Therapy
Introduction
Nasopharyngeal Structure
• Non-respiratory anatomical
dead space
• Impacts breathing efficiency
• Provides challenges to
conventional non-invasive
respiratory support
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Vapotherm: High Flow Therapy
Introduction
Fundamental physiologic
mechanisms enhance
respiratory efficiency
independent of disease
Feasible only because of
advances in gas
conditioning technology
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Vapotherm: High Flow Therapy
High Flow Therapy: Definitions
Nasopharyngeal
dead-space continually
flushed
Proper gas conditioned
a must for optimal
outcomes
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Vapotherm: High Flow Therapy
High Flow Therapy: Definitions
Conventional Therapy is limited:
• 6 L/min in Adults
•2 L/min in Infants
Results in mucosal damage
HFT allows higher flows :
• 40 L/min in Adults
•8 L/min in Infants
Improves efficiency of breathing
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Vapotherm: High Flow Therapy
High Flow Therapy: Definitions
Flows that exceed patient demands at various minute volumes.
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Vapotherm: High Flow Therapy
Pulmonary Physiology
Review of Normal
Respiratory Physiology
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Vapotherm: High Flow Therapy
Pulmonary Physiology
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
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Vapotherm: High Flow Therapy
Pulmonary Physiology and Dead Space
Nasopharynx
• Cleaning
Conducting
• Warming
Airways
• Humidification
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Vapotherm: High Flow Therapy
Pulmonary Pathophysiology
Pathophysiology
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Vapotherm: High Flow Therapy
Pulmonary Pathophysiology
Physiologic dead space
in lungs should be small
However DS increases
with progressing lung
pathology making
patients with disease
work harder
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Vapotherm: High Flow Therapy
Pulmonary Pathophysiology
Flushing reduces
anatomical dead space
Reduced anatomical
dead space
compensates for
increased physiological
dead space
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Vapotherm: High Flow Therapy
Inspiratory Gas Conditioning
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Vapotherm: High Flow Therapy
Conditioning Prevents Injury
Inadequate warming and humidification causes:
• Thickened secretions
• Decreased mucocilliary action
• Thermal Challenge
• Bloody secretions
• Lung atelectasis
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Vapotherm: High Flow Therapy
High Flow Therapy Mechanisms
During exhalation, the
dead space is purged so
that the next breath
contains more fresh gas
and less end-expiratory gas
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Vapotherm: High Flow Therapy
Gas Conditioning and Airway Function
Bronchoconstriction
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Vapotherm: High Flow Therapy
Gas Conditioning and Airway Function
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Vapotherm: High Flow Therapy
Summary
HFT comes with proper conditioning of breathing gases to…
•Support spontaneous breathing beyond conventional nasal cannula
•Improve breathing efficiency through basic mechanisms
•Improves patient comfort with the simplest interface
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Vapotherm: High Flow Therapy
Thank You
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