Effect of airway
control by glottal structures on postural stability.
Massery M, Hagins M, Stafford R.
Moerchen V. and Hodges PW.
J Appl Physiol. 2013;115:483-490.
If the title of this research article doesn’t
grab your attention, how about the authors Massery?
Hodges? Yes, please! After taking Mary Massery’s PT, DPT, DSc 3-day course,
“IF YOU CAN’T BREATHE, YOU CAN’T FUNCTION” I was inspired to read one of her
original papers.
Breathing, well it is exquisite. It is
simple, yet so complex. It is life. It is the first thing we do and the last
thing we do. As a former long-distance runner, I enjoyed the rhythmic pace and
sound of my breath. These days, I enjoy walking as a moving meditation. Both of
these activities promote a focus on the breath and with that, encourage us to
be in the moment.
Through my studies of the Dynamic
Neuromuscular Stabilization (DNS) approach with the Prague School of
Rehabilitation, I have learned that intra-abdominal pressure (IAP) is an
important contributor to our “integrated spinal stabilizing system” (ISSS).1 The coordination of the diaphragm and trunk
muscles is essential for the simultaneous functions of breathing and postural
support. The function of breathing takes precedence
over postural support when the system is challenged or compromised,2
perhaps contributing to one of the many reasons why we lose this ability to
perform both functions simultaneously. I have had great success with many
patients, re-training this neuromuscular unit that can be conceptualized as a
cylinder. In the abdominal cavity, this cylinder includes the diaphragm, the
multifidi, and the abdominal and pelvic floor muscles all of which have been
shown to have a role in creating and controlling appropriate IAP for spinal stabilization.3,4,5
In addition, the important element of the rib cage position, correcting for an
inspiratory position if needed, is essential to establish better function of
the diaphragm and thus the ISSS.6
When assessing a patient’s breathing pattern,
I look for qualitative elements described by Kolar “the lower chest and abdomen
expand evenly, the sternum moves ventrally, intercostal spaces widen, the lower
thorax expands in width and A-P dimension, and accessory muscles are relaxed.”1
I have found that re-establishing this pattern along with a corrected
inspiratory position of the rib cage if needed, is the key to improving the
coordination of the diaphragm and thus the function of this complex
neuromuscular unit of stabilization.
Previous research
has shown decreased postural control of the lumbar spine and longer trunk
muscle response times in patients with chronic low back pain,7 thus
providing a good rationale to retrain the muscles that control IAP for improved
function and postural support. In this recent work by Massery et al. 2013, the
authors support the importance of IAP as well as intra-thoracic pressure (ITP)
to maintain upright posture. Because the glottis contributes to the control
ITP, this concept is further developed through this study and presents evidence
to support the evaluation of glottal function when considering postural
instability issues. 8
With
that view, let’s move superiorly in the body from the abdomen to the thorax to
investigate the findings of Massery et al. 2013.
A brief review of anatomy and function:
·
The
glottis or glottic opening include the vocal folds and the space between the
folds. The laryngeal muscles adjust the size of the opening depending on the
need; abducts and opens for breathing (inhalation and exhalation) and adducts
for voicing.9
Below is a summary of my understanding of the
key points of this article (with the benefit of attending Mary Massery’s PT,
DPT, DSc course) 8,13,14 and through the lens of an orthopedic
physical therapist. To guide my thought process, I selected questions from
“Critiquing Research Articles”, published by Flinders University in Adelaide,
Australia.10,11,12
What
is the aim of the study?
·
“This
study aimed to investigate the effect of modulation of airway control on
upright postural stability during postural perturbations”.8
What
background information is provided that is relevant for this study?
·
Traditionally,
we have looked at abdominal and erector spinae muscles when considering
postural trunk control, it is also important to consider the contribution of
IAP and ITP
·
Current
research supports the following muscles in regulation of IAP/ITP: the diaphragm,
intercostals, abdominals, pelvic floor muscles and glottal structures
·
The
link between breathing and center of pressure (CoP) has been shown to be
impaired in patients with low back pain (LBP)
·
Trunk
muscles and the glottis have a primary role in regulation of ITP and therefore,
should be considered when evaluating postural stability
·
This
article identifies a gap in the literature regarding glottal function and its
possible contribution to postural control
What methods were used?
· Gentle trunk perturbations were
applied to subjects in standing for the following seven conditions, and
thoracic and CoP displacements were measured.
Table
1. Definitions and instructions for
breathing/voicing conditions
J Appl Physiol. 2013;115:485.
Breathing
Conditions
|
Airway flow at
time of perturbation
|
Glottis
position during perturbation
|
Instructions to
patient
|
1.
Max. inhalation + breath-hold
|
No
|
Closed
|
“Take the biggest breath you can then hold your breath
until the weight drops.”
|
2.
Ah/voicing
|
Yes
|
Partially
open
|
“In a
normal, full speaking voice, say “ah” for as long as you can until the weight
drops.”
|
3.
Natural breathing
|
Yes
|
Open
|
“Breathe normally. Do not take deep breaths. Do not
take shallow breaths. Don’t hold your breath. Just breathe normally until the
weight drops.”
|
4.
Counting out loud
|
Yes
|
Partially
open
|
“Count
out loud to seven in a normal, full speaking voice until the weight drops. Do
not talk softly. Do not shout. Just use your normal full voice.”
|
5.
Normal exhalation + breath-hold
|
No
|
Closed
|
“Take an easy breath in. Exhale normally. Then hold
your breath until the weight drops.”
|
6.
Normal exhalation + airway open (no breath-hold)
|
No
|
Open
|
“Take
an easy breath in. Exhale normally. Pause. Keep your airway open until the
weight drops by thinking that you could exhale for a few seconds more if you
needed to.”
|
7.
Sigh H sound
|
Yes
|
Open
|
“Take a deeper breath than normal then say “ha” like a
sigh. Do not push the air out. Let the air fall out like a normal sigh until
the weight drops.”
|
What
were the main findings?
·
Thorax
o Displacement was greatest when the glottis
was completely open (sigh) and thus more stable when the glottis was completely
closed
·
CoP
o Displacement was greatest (with backward
perturbation) when the glottis was completely open or closed and thus more
stable when the glottis was at mid-range (voicing)
What
is the significance of this research?
In response to minimal trunk perturbations,
thoracic and CoP strategies differed. It is well known that breath holding,
theoretically creating a stiff trunk is used as a strategy for heavy lifting.
However, either extreme of glottal conditions (maximum opening/closing) appears
to decrease the more subtle and dynamic postural control related to CoP.
·
Therefore,
o Maximum closure as with a breath holding
strategy may be beneficial for short term tasks requiring heavy lifting
(maximally stabilizing the thorax).
o Mid-range control as with talking may be more
beneficial for tasks requiring dynamic postural control (minimizing CoP
displacements).
What
conclusions were reached?
·
Modulation
of the airway by the glottis affects balance and so may be an important concept
to incorporate when working with patients with balance and/or breathing
impairments.
My
thoughts on integrating this information into my practice
How do I view trunk and postural stability
now? In addition to muscles that regulate IAP, it now includes the upper trunk,
ITP and the lid to the cylinder – the glottis. I feel that my cylinder is now
complete! In my practice, I have collaborated often with several women’s health
physical therapists and now, I think I need to spend some time with our speech
therapy colleagues!
·
A few more thoughts:
o I now have more strategies for my patients
with balance impairments and will consider counting or voicing to promote
control of the CoP as they work on postural stability.
o I will be more aware of the connection
between LBP, poor spinal stabilization, and possible balance impairments.
o When I work with patients to improve spinal
stabilization, often times they cannot coordinate both breathing and abdominal
bracing at the same time. This requires more skill and coordination. A strategy
to help improve this coordination by monitoring a continuous breath, is to have
patients count out loud. I am now aware that with this counting strategy, the
glottis is activated in mid-ranges contributing to the control of ITP/IAP and
ultimately to their postural stability when I progress the challenge to more
dynamic and functional positions.
o Re-training a patient’s spinal stabilization
abilities can improve pain and many functions. In addition to the patient
interview and direct assessment of breathing and stabilization strategies,
additional cues that guide me to address this impairment are: an inspiratory
rib cage position, patients who run out of breath while talking, complaints of
incontinence, abdominal and trunk skin creases, asymmetrical trunk muscle bulk,
trembling muscles with supine to sit, over developed superficial muscles and
now complaints of balance are all possible indicators that the spinal
stabilizing system may be impaired.
I want
to thank Mary Massery, PT, DPT, DSc and her team for their exploration of the
mechanics of breathing and postural stability, for contributing to my practice,
and for linking multiple systems in the body enabling us to look at our
patients as a whole.
That’s
all for now, in the meantime I’m keeping my glottis tuned for the next Mary
Massery course and research article!
Tracey
Wagner PT, DPT, OCS, FAAOMPT
Movement
Links Instructor
Assistant
Professor, Samuel Merritt University
Tracey Wagner is an Assistant
Professor and Samuel Merritt University teaching musculoskeletal courses and is
working on developing a part time clinical practice and her line of scholarship
in the area of movement science. She is a DNS Certified Practitioner, as well
as a Movement Links Certified Clinician and Instructor. She moved to the
beautiful Bay Area after a 17-year career working for Kaiser Permanente
Woodland Hills, serving there as a clinical specialist, mentor, and
educator. Tracey has been published in the Journal of Orthopaedic
and Sports Physical Therapy (JOSPT) for a case report on muscle imbalances of a
professional triathlete and received the California Physical Therapy
Association’s 2010 Clinician Research Publication Award.
-----
References
1.
Kolar P et al. Clinical Rehabilitation. 1st
ed. Prague, Czech Republic: Alena Kobesvoa, Rehabilitation Prague
School;2013:56-58, 275-279.
2.
Hodges PW,
Heijnen I, Gandevia SC. Postural activity of the diaphragm is reduced in humans
when respiratory demand increases. J
Physiol. 2001;537:999-1008.
3.
Hodges PW, Eriksson AE, Shirley D, Gandevia SC.
Intra-abdominal pressure increases stiffness of the lumbar spine. J Biomech.
2005;38(9):1873-1880.
4.
Hodges PW, Sapsford R, Pengel LHM. Postural and respiratory
functions of the pelvic floor muscles. Neurourol Urodyn. 2007;26:362-371.
5.
Finta R, Nagy E, Bender T. The effect of diaphragm training
on lumbar stabilizer muscles: a new concept for improving segmental stability I
the case of low back pain. J Pain Res. 2018;(11):3031-3045.
6.
Kolar P, Sulc J, Kyncl M, et al. Postural Function of the
Diaphragm in Persons With and Without Chronic Low Back Pain. J Orthop Sport
Phys Ther. 2012;42(4):352-362.
7.
Radebold, Andrea, MD; Cholewicki, Jacek, PhD;
Polzhofer, Gert K., BA; Greene, Hunter S., MD. Impaired postural control of the lumbar spine
is associated with delayed muscle response rimes in patients with chronic
idiopathic low back pain. Spine.
2001;26(7):724-730.
8.
Massery M, Hagins M, Stafford R. Moerchen V. and Hodges PW.
Effect of airway control by glottal structures on postural stability. J Appl Physiol. 2013;115:483-490.
10. Student Learning Center, Flinders University, Adelaide,
Australia. http://www.flinders.edu.au/slc_files/Documents/Blue%20Guides/Critiquing%20Research%20Articles.pdf
11.
Ryan, F,
Coughlan, M & Cronin, P 2007, ‘Step-by-step guide to critiquing research.
Part 2: qualitative research’, British Journal of Nursing,, vol. 16, no.
12, pp. 738-743.
12.
Stockhausen
L & Conrick, M 2002, ‘Making sense of research: a guide for critiquing a
paper’, Contemporary Nurse, vol. 14, no. 1, pp. 38-45.
13.
Massery, M. Class notes for continuing education course: “If
you can’t breathe, you can’t function”. Samuel Merritt University. August 3-5th,
2018
