AASM Membership Sections Newsletter Issue #2
18
American Academy
of Sleep Medicine
resulted in improvement in airflow, similar or better
than just from GG (protrusor) stimulation (Eisele
1997,
Oliven 2007). In animals, HGN trunk stimula-
tion also resulted in volumetric airway expansion but
with denervation of the intrinsic (non-genioglossus)
muscles, the response was greatly attenuated (Bai-
ley 2006). Thus an electrode with six contacts that
could be independently stimulated was designed, in
order to be able to selectively activate various muscle
groups for airway patency. The architecture of the
HGN facilitates selective co-activation of muscles in
that the human HGN trunk in the submandibular
triangle was discovered to be
non-fasciculated
(
Zaidi
2012).
By cyclically activating different electrode
contacts, fatigue may be avoided and a sensing lead
is not needed. Mapping and programming of the
contact combinations leading to effective airway
dilation is required.
Clinical Trials
Inspire Medical’s device initial trial recruited CPAP-
intolerant adult patients with BMI < 35, AHI ≥
25
and excluded patients with prior upper airway
surgery, COPD and congestive heart failure (van de
heyning 2012). Electrode implantation was at the
HGN trunk. There were twenty patients with a mean
BMI of 29.8±2.7 and mean age of 55.7±8.1. The
baseline AHI was 43.6±18.4 and ODI was 30.1±24.0.
The mean AHI was reported as unchanged for the
whole group after 6 months from the trial start. Six of
the twenty patients were classified as responders with
≥50% AHI reduction and for this subgroup the AHI
declined from 26.1±4.5 to 7.7±4.1 (P<.01) and the
ODI from 14.5±7.2 to 6.7±4.3 (P<.05). Given the low
response rate, the patients enrolled in part 2 of the
trial were selected further in terms of exclusion crite-
ria. Their BMI limit was 32, AHI limit was 50 and on
drug-induced sleep endoscopy they could not have
complete concentric collapse at the level of the soft
palate. Electrode implantation site was changed to the
medial branch of the HGN. There were eight patients
in part 2 of the trial, with BMI 28.9±2.1. At 6 months
the group’s AHI declined from 38.9±9.8 to 10.0±11.0
and the ODI declined from 32.1±15.1 to 9.5±10.2
(
P<.01 for both). Micro-arousal rate was much lower
in responders vs non-responders, assessed in seven
patients. Epworth sleepiness scale (ESS) score de-
clined from 11.0±5.0 to 7.6±4.3 (P<.01). One serious
adverse event was device explanted for infection and
in addition one patient exited part 2 due to inability
to activate the tongue with sufficient amplitude.
Apnex Medical’s device initial trial recruited CPAP-
intolerant adult patients with BMI <40 (<37 in US),
AHI of 20-100 and with hypopneas being ≥80% of
the total AHI (Eastwood 2011). The trial protocol
excluded patients with large tonsils, severe retrogna-
thia, history of upper airway and jaw surgery, nasal
obstruction >5% central apneas and other criteria
such as severe medical illnesses (Eastwood Sleep
2011).
Electrode implantation was at the HGN medial
branch. There were 32 patients at baseline a mean BMI
of 32.4±3.9 and mean age of 52.8±9.6. The baseline
AHI was 44.7±17.7 and ODI was 20.4±17.2. After 1
year, with n=26, the mean AHI declined to 20.8±16.3
(
P<.001) and the ODI to 12.0±14.3 (P=.006). The
investigators remarked that patients with a BMI < 35
had a much greater decline in the mean AHI than the
entire group. The arousal rate declined from 43.8±17.7
to 25.4±11.1 (P<.001). ESS score declined from
12.0
±4.5 to 7.4±3.6 (P<.001) and improvements were
also noted on multiple other quality of life outcome
questionnaires. Serious adverse events reported were
one infection/hematoma with device explant, two elec-
tive explants and two cuff dislodgements that required
replacement for continued treatment.
ImThera Medical’s device initial trial recruited
CPAP-intolerant adult patients with BMI <40 and
AHI ≥20. The trial protocol excluded patients with
large tonsils, severe macroglossia (tongue position
4),
nasal polyps, syndromic craniofacial anomalies,
central sleep apnea, but did not exclude patients with
Continued >>
Neurostimulation for OSA continued