Theme : Dreams
Cervical Positional Effects on Snoring and Apneas
Clete A. Kushida, Sripad Rao, Christian Guilleminault, Sylvie Giraudo,
Janie Hsieh, Pamela Hyde and William C. Dement
Stanford University Sleep Disorders Clinic and Research Center, Stanford,
California, 94305, USA
Abstract
We examined the effects of cervical position on the Obstructive Sleep
Apnea Syndrome (OSAS) through the use of a custom-designed cervical pillow
which promoted neck extension. Twelve subjects with OSAS were recruited
from a tertiary sleep disorder clinic population. Of the twelve subjects,
three had mild cases of OSAS, four had moderate cases, and the remaining
five had severe cases. The subjects used their usual pillows during two
consecutive recorded baseline nights in our laboratory. The subjects then
used the cervical pillow for five days at home, and returned for two consecutive
recorded nights at our laboratory while using the cervical pillow. During
the nights in our laboratory, the subjects completed questionnaires, were
videotaped to record head and body position, and had their breathing parameters
recorded during sleep. Subjects with mild OSAS cases had a non-significant
improvement in the severity of their snoring and a significant improvement
in their respiratory disturbance index with the cervical pillow, while
subjects with moderate OSAS cases showed no improvement in these parameters.
Subjects with severe OSAS cases showed slight improvement in some measures
of their abnormal respiratory events during the experimental period.
Current Claim: Subjects with mild cases of the Obstructive Sleep Apnea
Syndrome showed improvement in the severity of their snoring and sleep-disordered
breathing using a custom-designed pillow which promoted neck extension.
Activate the ShortNotes by clicking on this link. Your notes will be stored
in this area and automatically retrieved upon your next visit.
The cervical pillow was designed to reduce the severity of snoring and
sleep-disordered breathing in individuals with the Obstructive Sleep Apnea
Syndrome (OSAS). Snoring, sleep-related breathing pauses, and excessive
daytime sleepiness characterize this sleep disorder. The OSAS diagnosis
is confirmed by a respiratory disturbance index (RDI, apnea-hypopnea index)>5
events/hr during polysomnography (sleep study) which includes monitoring
of respiratory parameters. This disorder carries significant morbidity,
including an increased risk for hypertension, cardiac dysrhythmias and
failure, myocardial infarction, stroke, and sleepiness-related industrial
and motor vehicle accidents.
The cervical pillow was designed to extend the head in a posture similar
to that used in cardiopulmonary resuscitation (CPR) to create an open
airway in an unconscious victim. Similarly, studies have documented better
visualization and patency of the upper airway for intubation of children
and adults with the head extended (Westhorpe, 1987; Shorten et al., 1995a;
1995b). Prior investigators have observed that head position modifies
upper airway resistance, with less resistance noted when the subjects'
heads were extended (Liistro et al., 1988; Jan et al., 1994). A 20-degree
head extension resulted in a significant increase in the cross-sectional
dimension of the pharyngeal airway as shown by lateral skull radiographs
(Hellsing, 1989). Although these studies evaluated conscious subjects,
similar changes in upper airway resistance or cross-sectional area would
be expected with head position in sleeping subjects. However, asleep subjects,
particularly those with OSAS, would be expected to have overall higher
upper airway resistances due to relaxation of the upper airway musculature
during sleep. Interestingly, similar findings were observed in dogs (Odeh
et al., 1995), where head extension resulted in a more negative pressure
at which upper airway collapse occurred and increased maximal flow compared
to head flexion.
The cervical pillow used in the present study (Figure 1) consists of
a urethane foam foundation, an overlying NASA "memory foam"
supporting the head and neck, a stretch terry-cloth cover, and a cotton
pillowcase. The pillow was custom-fitted to each subject by three simple
measurements of the head and neck. The objective of the present study
was to test whether the neck posture enforced by this pillow would be
adequate to reduce the severity of the snoring and sleep-disordered breathing
in OSAS subjects.
Activate the ShortNotes by clicking on this link. Your notes will be stored
in this area and automatically retrieved upon your next visit.
Fifteen subjects with OSAS who were otherwise healthy were recruited.
Since the subjects were recruited from the clinic population at our tertiary
sleep disorders clinic, each subject had a physical examination and evaluation
by a board-certified sleep specialist and had confirmation of a diagnosis
of OSAS by polysomnography prior to enrollment in the study. The subjects
were recruited consecutively into the study following their OSAS diagnosis.
The inclusion criteria for the study were as follows: (1) men and women
between the ages of 18 and 80 years; (2) characteristic symptoms of OSAS
(e.g., snoring, witnessed breathing pauses, excessive daytime sleepiness);
(3) an Epworth Sleepiness Scale Score>10; and (4) polysomnographic
confirmation of OSAS, with an RDI>5. Exclusion criteria were complex
or serious medical or psychiatric conditions; co-existing sleep disorders;
mental or sensory impairment which prevented the subjects from understanding
or completing the requirements of the study; alcoholism or substance abuse;
use of benzodiazepines, barbiturates, protriptyline, or other respiratory
stimulants or depressants; and use of medications known to affect sleep
(e.g., antitussives, antihistamines, analgesics, sedatives, tranquilizers,
hypnotics, or amphetamines).
The subjects were studied using the following protocol: (1) Two consecutive
baseline nights in our laboratory, during which the subjects used their
own low, regular pillow and respiratory data were recorded. (2) Five adaptation
nights in which the subjects adapted to the cervical pillow at home. (3)
Two consecutive experimental nights in our laboratory, during which the
subjects used the cervical pillow and their respiratory data were once
again recorded. The subjects completed medical and sleep disorder screening
questionnaires, and bedtime and morning questionnaires. The body weight
of each subject was measured upon recruitment, and self-reported body
weights were obtained on each recording night at the laboratory. An Edentrace
II® System was used to provide data on the subject's oronasal airflow,
chest wall movement, heart rate, body position, snoring and oxygen saturation
during sleep. The recorded data were printed out, and each record was
evaluated for abnormal respiratory events independently by two investigators.
A computer simultaneously analyzed these data, and any discrepancies between
the computerized and handscored data were rectified. The subjects were
also recorded during each laboratory night by videotape. Every change
in head and body position for each subject was documented, and the number
of abnormal respiratory events with every possible head and body position
during sleep were calculated. All data were statistically analyzed using
SYSTAT® 7.0 for Windows®. Paired t-tests were used to compare
baseline and experimental conditions for each parameter studied. Statistical
significance was defined as alpha<0.05.
Activate the ShortNotes by clicking on this link. Your notes will be stored
in this area and automatically retrieved upon your next visit.
Figure 1
Figure 2
A total of 15 subjects were eventually studied. One subject had improvement
in OSAS after her initial sleep study at the clinic, but prior to her
baseline nights, so that the severity of her sleep-disordered breathing
was below the OSAS respiratory disturbance index of 5. A second subject
did not return for her second baseline night. A third subject did not
sleep well during her baseline period, obtaining less than 5 hours on
her second baseline night, and withdrew from the study.
Twelve subjects remained in the study: there were nine men and three women,
between the ages of 24 and 67 years. No significant self-reported body
weight fluctuations were reported for any of the subjects. Of these 12
subjects, their baseline OSAS was as follows: three (all men) of the subjects
had mild cases (RDI=5-20), four (2 men, 2 women) had moderate cases (RDI=20.1-40),
and the remaining five (4 men, 1 woman) had severe cases (RDI>40.1).
The results are summarized in Table 1.
For the three mild OSAS cases, the mean number of apneas showed a non-significant
decrease between baseline and experimental conditions, while the mean
number of hypopneas significantly decreased. The mean RDI showed a significant
decrease between baseline and experimental conditions. The mean duration
of the apneas and hypopneas showed a non-significant decrease between
baseline and experimental conditions. The mean oxygen saturation and the
minimum oxygen saturation were higher during the experimental compared
to the baseline condition. Although non-significant, mean percentage of
snoring during the study and mean snoring duration were both reduced in
the experimental compared to the baseline condition. Interestingly, although
the subjects spent an average of more time in the body supine, head supine
position in the experimental compared to the baseline condition, there
was a non-significant decrease in the number of abnormal respiratory events
in the former condition (Figure 2) for mild versus moderate and severe
OSAS subjects.
For the four moderate OSAS cases, the minimum oxygen saturations were
significantly lower during the experimental compared to the baseline condition.
The subjects showed either no change or non-significant worsening of their
snoring or obstructive sleep apnea parameters during the experimental
versus the baseline condition.
For the five severe OSAS cases, there was a non-significant reduction
in the mean number of apneas and hypopneas in the experimental compared
to the baseline condition, as well as a non-significant reduction in the
mean duration of the abnormal respiratory events in the experimental compared
to the baseline condition. However, the mean RDI and minimum and average
oxygen saturations did not show parallel changes. There were no additional
improvements in any of the other snoring or obstructive sleep apnea parameters
studied.
For all OSAS cases, the subjects reported non-significant improvement
in their sleep, in terms of the depth and restfulness of their sleep,
in the experimental compared to the baseline condition.
Activate the ShortNotes by clicking on this link. Your notes will be stored
in this area and automatically retrieved upon your next visit.
The mild OSAS cases showed improvement in their snoring and abnormal respiratory
events while using the cervical pillow compared to their baseline nights
when they used their usual pillow. However, there was no improvement in
either snoring or abnormal respiratory events for the moderate cases in
their experimental versus baseline nights. Paradoxically, for the severe
OSAS cases, there was non-significant improvement in the mean number of
apneas and hypopneas as well as in the mean duration of the abnormal respiratory
events in the experimental compared to the baseline condition. The mild,
moderate, and severe cases all reported a non-significant subjective improvement
in the depth and restfulness of their sleep. This study is limited in
several respects: (1) Since the sample sizes are very small, the terms
"significance" and "non-significance" should be taken
with caution; the limited sample sizes may also explain the discrepancies
in findings between the mild, moderate, and severe cases. (2) Total sleep
times for our subjects were not obtained since our sleep studies measured
respiratory parameters without EEG data; this could be a source of error
in calculation of the RDI. (3) The subjective improvement in depth and
restfulness of the subjects' sleep may reflect an order effect or laboratory
adaptation bias.
In conclusion, based on our very limited study, subjects with mild cases
of OSAS may show improvement in the severity of their snoring and sleep-disordered
breathing using the cervical pillow evaluated in this study. The mechanism
by which the cervical pillow improves snoring and sleep-disordered breathing
in subjects with mild cases of OSAS is unknown, but is probably due to
the increased cross-sectional area associated with head extension. Moderate
and severe cases of OSAS are less likely to benefit from this pillow;
however, larger sample sizes in all three OSAS categories would be desirable.
1. Hellsing E. Changes in the pharyngeal airway in relation to extension
of the head. Eur J Orthod 1989; 11(4): 359-65.
2. Jan MA, Marshall I, Douglas NJ. Effect of posture on upper airway dimensions
in normal human. Am J Respir Crit Care Med 1994; 149(1): 145-8.
3. Liistro G, Stanescu D, Dooms G, Rodenstein D, Veriter C. Head position
modifies upper airway resistance in men. J Appl Physiol 1988; 64(3): 1285-8.
4. Odeh M, Schnall R, Gavriely N, Oliven A. Dependency of upper airway
patency on head position: the effect of muscle contraction. Respir Physiol
1995; 100(3): 239-44.
5. Shorten GD, Ali HH, Roberts JT. Assessment of patient position for
fiberoptic intubation using videolaryngoscopy. J Clin Anesth 1995a; 7(1):
31-4.
6. Shorten GD, Armstrong DC, Roy WI, Brown L. Assessment of the effect
of head and neck position on upper airway anatomy in sedated pediatric
patients using magnetic resonance imaging. Pediatric Anaesth 1995b; 5(4):
243-8.
7. Westhorpe RN. The position of the larynx in children and its relationship
to the ease of intubation. Anaesth Intensive Care 1987; 15(4): 384-8.
We would like to thank Jennifer Yeh for her assistance in the data collection
for this study.
Original address of this text :
http://www.sro.org/bin/article.dll?Paper&1491&0&0
Please copy this address to the address bar of your
internet browser and press the "enter" key.
(We prefer not to put actual links because
often page locations change and then our log files get cluttered with
error messages
- if the address does not work try to find it from the homepage of the
website in question).
|
