HFNC therapy provides high flow oxygen through a nasal cannula. It has several benefits over traditional oxygen delivery methods, including more accurate oxygen delivery, washout of dead space, and generation of positive end-expiratory pressure. HFNC is a well-tolerated therapy that can be used for hypoxemic respiratory failure, pre-intubation, and post-extubation. While promising, further research is still needed to establish clear guidelines for its use.

1. HFNC Therapy In
Adults
Waheed Shouman
Professor of Chest Medicine
Zagazig, Egypt

2. Types of Oxygen delivery masks
Low flow
 Simple face mask
 Partial rebreathing face mask
 Non-rebreathing face mask
 Nasal prong
High Flow
 Venturi
 HFNC

3. Drawbacks of oxygen delivery
devices
 Patient discomfort
 Dryness of airways
 Failure to achieve patient demand
 Inaccurate oxygen delivery
 Treatment failure necessitating escalation

4. The beginnings

5.  Using conventional devices, oxygen flow is limited
to no more than 15 L/min. Meanwhile, the required
inspiratory flow for patients with respiratory failure
varies widely in a range from 30 to >120 L/min
 FiO2 is inconstant and generally lower than
expected
 HFNC neither pushes nor pulls gas; consequently, it
does not facilitate VT and minute ventilation
Nishimura, 2016

6.  Due to poor mask tolerance, NIV is inapplicable to
some patients
 The major difference between NIV and HFNC is
the interface
 Whereas NIV interfaces increase anatomical dead
space, HFNC decreases dead space
 HFNC is the only noninvasive respiratory support
that does not increase dead space.
 The simplicity and excellent tolerance of the
system is attractive
Nishimura, 2016

11. • Precision Flow ® (Vapotherm, Exeter, UK), the first
system approved for use in patients by the US Food
and Drug Administration in 2004
• Optifl ow system ® (Fisher & Paykel, Auckland,
New Zealand)
• Comfort-fl o ® (Telefl ex Medical, Durham, NC,
USA).

13. HFNC
Up to 60L/min
Heated to 37⁰ C
Humidified to 44 mg H2O/L (99-100%)

14. Humidification in HFNC Devices:
 It is electrical system applying constant vapor
 It is apply full saturation in well-fitted nasal cannula at
rates up to 40 L/min
 HFNC devices usually incorporate a heated circuit to
avoid losing vapor in condensation, although some
condensation is inevitable.
 The amount of condensation depends on atmospheric
temperature.
 At higher flows, full saturation is questionable
 If the patient inspiratory flow is higher than that of
HFNC, the FiO2 and humidity is less expected

15. Adverse Effects of Lack of Humidification:
 Decreased nasal and respiratory mucociliary clearance
(up to complete cessation)
 This leads to acute damage and inflammatory response
of airway epithelium
 Cilia loss , sloughing of epithelium
 Sub epithelial vascular congestion
 Increased airway resistance and bronchospasm and
increased WOB
 Excessive water loss

16. HFNC
Deliver accurate O2 near or exceed patient peak
inspiratory flow rate

17.  Adult patients show less skin damage with HFNC
than with bi-level positive airway pressure
treatment
 HFNC offers a better balance between
oxygenation and comfort than NIV
 Thoraco-abdominal synchrony was better with
HFNC than with face mask delivery. Mostly
attributed to decreased WOB

18. HFNC
Washout of nasopharyngeal dead space :
 Decrease dead space
 Improve alveolar ventilation
 Higher resting O2 saturation
 Improved CO2 clearance
Paliouras et al 2016

20. Generation of PEEP effect
 PEEP effect is a main difference between conventional O2
therapy and HFNC
 At flows 35-50 L/min , PEEP ranging from 2.5-7.5 H2O
 high flow from the nasal cannula meets resistance from
patient expiration, and pressure in the pharynx increases
The degree of pressure generated is dependent on:
• Flow rate (important)
• Geometry of upper airways
• Oral or nasal breathing
• Sex (higher in females)
• Lung mechanics (compliance more important than
resistance)
• Leaks around nares
Paliouras et al 2016

21. HFNC
 Increase in End-Expiratory Lung Volumes
and tidal volume (Paliouras et al 2016)
 Leading to decreased WOB (Delorme et al
2017)
 Prevent small airway closure
 Decreased shunting and better oxygenation

22. Enhanced Patient Comfort and
Compliance
Due to:
 Optimal heat
 Optimal humidity
 No mouth or nasal drying
 Less mask removal
 Better communication
Paliouras et al 2016

23. Papazian et al 2016

24. Goligher and Slutsky 2017

25. Intiation
 Explain
 Start with lower flow (20-35L/min)
 Ensure tubing support not to pull on nasal cannula
 FiO2 as needed from 21-100%
 Encourage nasal breathing with closed mouth
 Flow increased in increments of 5L/min according to
patient needs
 On weaning off : decrease FiO2 first then flow

29. Hypoxemic Respiratory Failure (1):
 HFNC help in maintaining stable FiO2 and positive
pharyngeal pressure
 Actual Fi02 values are close to delivered FIO2
 Compared to conventional flow of up to 15L/min,
HFNC reduced breathing frequency, heart rate,
dyspnea score, and supraclavicular retraction and
improved thoraco-abdominal synchrony and Spo2.
 HFNC up to 7 days was not interrupted due to
intolerance
 HFNC can be regarded as a first-line treatment for
patients with mild to moderate hypoxemic ARF

30. Hypoxemic respiratory failure (2)
 As HFNC does not ensure positive pharyngeal
pressure, it has not been recommended for severe
hypoxemic ARF
 Subjects with bacterial pneumonia failed HFNC
more frequently than others
 When HFNC was applied as the first-line
treatment, in ARDS, 40% of the subjects were
subsequently intubated (higher SAPS II)
 Compared to standard oxygen therapy, HFNC
provides significant less NIV, and intubation rate
with more ventilator-free days
Nishimura, 2016, Mauri et al 2017

31. Hypoxemic respiratory failure (3)
 In post cardiothoracic surgery patients, the failure
rate of HFNC and BiPAP was equal (21%)
 HFNC showed a trend toward reduction in the
intubation rate, which did not meet statistical
significance compared with COT or NIV, and no
improvement in mortality (Lin et al 2017)
 HFNC is promising as a primary step in early ARF
(Nishimura, 2016)
 treatment with HFNC improved the survival rate
among patients with acute hypoxemic RF, even
though no difference in intubation rate compared
with COT or NIV (Frat et al 2015)

32. Hypercapnic Respiratory Failure:
 NIV is the primary modality for their respiratory
support
 Due to intolerability, HFNC can be applied
successfully
 HFNC is highly promising in acute hypercapnic RF
 In stable COPD patients, HFNC results varied
hence it is not advised for now

33. Papazian et al 2016

34. Predictors of HFNC Failure in ARF
 Persistent high RR
 Ongoing hypoxemia
 Thoraco-abdominal asynchrony
 Presence of non-pulmonary organ failure
 Persistent hemodynamic instability
 Declined mental status
Drake 2017

35. Preintubation Oxygenation
 HFNC doesn't not interfere with laryngoscopy, and could
be used to deliver oxygen during the apneic period of
tracheal intubation.
 comparing the effects of use of non-rebreathing bag and
HFNC on pre- and peri-procedure oxygenation during
tracheal intubation, Miguel-Montanes et al found that
with the non-rebreathing bag, the median lowest Sp02,
during intubation was 94%, whereas, with HFNC, it was
100%. With significantly less severe hypoxemia
Nishimura, 2016

36. Postextubation
 No effect in post-operative atelectasis
 It is the same , compared to conventional O2 therapy
although of better tolerance
 Systematic review and meta-analysis of RCTs in adult
patients after extubation suggests that COT may still
be the first-line postextubation management in
postoperative patients without ARF. The HFNC is not
inferior to NIV in patients with risks of extubation
failure (Huang et al 2017)
 HFNC oxygen therapy after extubation in
mechanically ventilated ARF patients can achieve a
higher success rate of oxygen therapy, improved
oxygenation, and a lower occurrence of discomfort
than an air entrainment mask (Song et al 2017)

37. Papazian et al 2016

38. Reintubation
In patients at high risk for reintubation, HFNC
delivered at 50 L/min after extubation had
similar efficacy to NIV

39. HFNC during Bronchoscopy
 HFNC permits oral passage of the bronchoscope
 In non RF patients, under midazolam sedation, HFNC
with 60 L/min flow produced marginally higher
oxygen saturations at the end of the procedure
compared to HFNC at 40 L/min or Venturi mask (98%
compared to 94% and 92%, respectively)
 Subjects reported similar levels of comfort for all
modes
 In RF patients, HFNC under propofol sedation, HFNC
and NIV produced same nadirs of SpO2, with more
intubation in 24 hours in NIV than HFNC (3 vs 1)
Simon et al 2016 and Drake 2017

40. Drawbacks
Most of studies are non-randomized,
(except FLORALI for 90 days with
better survival in HFNC)
Observational
No guidelines
Short term studies

41. Drawbacks
 Failure rate up to 30% (need for intubation)
 Sophisticated controlled trials are needed to
identify criteria for timing intubation during HFNC
 Rare: pneumothorax, pneumomediastinum
(newborn)
 Unnecessary delay on HFNC without intubation
increase mortality

42. Take home message
 HFNC is a promising well-tolerated option in
management of ARF
 HFNC is effective in early and mild to moderate
ARF
 HFNC combines benefits of COT and NIV
 HFNC is effective in intubation, post intubation
and FOB
 HFNC needs further RCT to implant guidelines for
its use