The Impact of High-Flow Nasal Cannula on Swallow Function

High-flow nasal cannula (HFNC) is a non-invasive heated and humidified oxygen delivery device
that is capable of delivering up to 60 L/min of flow. It is a relatively new modality that
has been introduced as an alternative to conventional oxygen therapy in patients with chronic
obstructive pulmonary disease (COPD) respiratory failure, obstructive sleep apnea (OSA)6,
post-extubation, and status asthmaticus The humidified gas preserves mucociliary function
that prevents secretion retention and enhances patient's comfort. This feature allows
prolonged use of HFNC in clinical sittings of up to 30 days

In addition to its ability to provide adequate humidification levels, HFNC has various
respiratory physiological effects. These physiological effects include: alveolar recruitment,
dead space washout, and decreased airway resistance. The clinical value of the use of HFNC is
not limited to its ventilation and oxygenation effects, it enables the patient to talk and is
purported to permit oral feeding during oxygen therapy.

Currently, despite the fact that patients are often permitted to eat while receiving HFNC
therapy, there is insufficient evidence regarding the impact of HFNC on swallow function. The
uncertainty of the effect of this oxygen delivery device on swallow function arises not only
from the limited number of studies, but also the contradictory results. For example, Sanuki
et al. reported that increasing the flow rates of the HFNC resulted in enhanced swallow
function by reducing reflex latency. Based on their findings, the researchers suggested that
the use of HFNC should not affect the decision to start or resume feeding. Similarly, Lader
et al. proposed that the use of high-flow nasal cannula should not delay oral alimentation.
On the contrary, Ferrara et al. conducted a study in neonates and concluded that providing
feeding while using Nasal Continuous Positive Airway Pressure (nCPAP) increased the risk of
aspiration. These opposing outcomes support the need for further studies to obtain more
definitive evidence.

Methods:

Spontaneous Swallowing Frequency:

Spontaneous swallowing is an airway protection reflex and the measurement of its frequency is
considered to be a sensitive indicator of swallow function. This index can sensitively
identify dysphagia and other swallowing-related disorders. Furthermore, the reduction in this
index is associated with increased level of secretions and chest infections. One modality
used to measure swallowing frequency is surface electromyography (sEMG), which records
electric activity during swallow via an electrode placed on the skin under the chin. This
non-invasive technology has been used for more than 20 years to record various aspects of
swallowing physiology. In this study, sEMG will be used because of its feasibility, accuracy,
and ability to detect a swallow.

Swallowing Effort and Timing:

Swallowing effort via submental sEMG provides an objective measurement of lingual and
sub-mental muscle activity during the act of swallowing. Measurements include muscle
contraction amplitude and contraction timing/speed. Clinically, swallowing effort parameters
have been used to document normative values in healthy individuals, as well as to document
the effects of a disease on swallowing. Prior research has shown that both amplitude and
timing are influenced by multiple factors including the volume and viscosity of the item (or
bolus) being swallowed, and the age and gender of the person swallowing. However no study has
investigated the effects of HFNC on either swallowing effort parameter.

The primary aim of this research is to determine the impact of different flow rates of a
high-flow nasal cannula on spontaneous swallowing frequency at rest and swallowing effort and
timing while swallowing.

This is a prospective study designed to measure swallowing frequency and swallowing effort in
fifty healthy adult volunteers (25 participants will be between 21 and 49 years old; and the
other 25 above 50 years old). To recruit volunteer participants, an email will be sent via
university internal email system to the faculty, students and employees in the departments of
Respiratory Care and Speech Language Pathology. Snowball sampling (non-probability sampling)
will also be utilized to recruit individuals outside of those departments. No compensation is
offered to the participants. Enrolled participants are sub-categorized into two different age
groups to determine if there are any swallowing differences between the different age groups.
Inclusion criteria include individuals who are older than 21 years of age and have no
cognitive impairment. Exclusion criteria include individuals who are less than 21 years of
age, have a history of dysphagia or disease/condition that may cause dysphagia, current use
of medications that alter swallowing function, nasal obstruction, and the presence of a
tracheostomy tube.

Upon meeting inclusion criteria, informed consent explaining the procedure and potential harm
will be obtained and a copy will be given to the subject. Then, a unique identification code
number will be assigned to protect the subject's identity.

HFNC:

The AIRVO 2 high-flow nasal cannula system (Fisher and Paykel Healthcare Limited, Panmure,
Auckland, New Zealand) will be used. Nasal prongs sizes are chosen as per manufacturer
recommendations. Participants will receive three levels of HFNC flow rates (30, 45, and 60
L/min) through nasal prongs. If a small-size nasal prong is used, the participant will
receive 30, 45, and 50 L/min flow rates instead of 30, 45, and 60 L/min, as manufacturer
recommendations state the maximum liter flow for a small-size nasal prong is 50 L/min. Oxygen
concentration will be set at 21% and a temperature of 37 °C. First, individuals will be
placed on the sEMG monitor. Following the application of the sEMG, each participant will sit
quietly for 10 minutes, before being attached to the HFNC, so a baseline swallow frequency
can be established. After the baseline swallow frequency is established, each participant
will be asked to swallow 8 boluses: 2 trials of water at 2 volumes (5 and 10 mL) and 2 trials
of applesauce at 2 volumes (5 and 10 mL). Participants will rest for 15 seconds after
completing each swallow. This procedure will establish the participant's baseline swallowing
effort measurements. Once these swallows have been completed, the participant will be placed
on the HFNC. Each participant will be placed on three different flow rates (30, 45, and 60
L/min or 30, 45, and 50 L/min) in random order. The random order will be generated by an
online random number tool (https://www.randomizer.org). The study participant will be
subjected to each flow rate for 15 minutes. During the first 10 minutes, swallow frequency
will be recorded. After 10 minutes at the given flow, the participant will complete the 8
aforementioned swallows. After completing all of the swallowing trials, the participant will
be removed from the HFNC for a period of 10 minutes. This process will be repeated for all
three flowrates for a total of 32 boluses swallowed.

Swallowing Frequency:

Swallowing frequency is analyzed by sEMG signals recorded on the KayPentax Digital Swallow
Workstation™ with integrated digital swallowing signals lab (DSW™, Model 7120, New Jersey). A
three-sensor sEMG electrode (Uni-Patch™, Disk #7500, Covidien Corporation, Tyco Healthcare,
Wabasha, MN) will be placed on the anterior neck skin under the chin, over the submental
muscles above the hyoid bone. Each patch will include two recording electrodes and a third
ground electrode. Spontaneous swallowing frequency is calculated as the number of swallows
per minute (SPM) for 10 minutes on room air and then for each HFNC intervention. Swallows
will be counted from the visual myographic waveform produced by the DSW.

Swallowing Effort:

Both swallowing amplitude and timing parameters will be obtained by analyzing the individual
graphic waveforms produced by the DSW algorithm. Measures will be obtained for each of the 8
swallows, at each of the HFNC flow rates.

Procedures Done for Research Purpose

The use of HFNC with three levels of flow (30, 45, and 60 L/min or 30, 45, and 50 L/min [for
small-size nasal prongs]).

Swallow frequency measurement through sEMG.

Swallowing effort measurement through sEMG - participants will swallow measured amounts of
water and applesauce. Presentation of the different volumes and viscosities will be done in
pre-determined random order.

Inclusion Criteria:

- 21 years of age or older

- No cognitive impairments

Exclusion Criteria:

- Less than 21 years old

- History of swallow dysphagia

- History of disease/condition that may cause dysphagia

- Use of medications that may alter swallow function

- Nasal obstruction

- Presence of tracheostomy tube