OHS
What is Obesity Hypoventilation
Syndrome (OHS)?
OHS is a breathing disorder seen in some people
who are obese that leads to low oxygen levels
and too much carbon dioxide in your blood. Low
oxygen and high carbon dioxide levels may develop
because of a condition called hypoventilation.
Hypoventilation means you are not moving enough
air in and out of your lungs. With OHS, you may also
have problems sleeping because of obstructive sleep
apnea. The three main features of OHS are:
■ obesity
■ daytime hypoventilation
■ sleep disordered breathing (such as obstructive
sleep apnea)
OHS has also been called Pickwickian Syndrome
because a character described by the famous author
Charles Dickens in his novel, The Posthumous Papers
of the Pickwick Club,has similar OHS symptoms.
What are the symptoms of OHS?
The symptoms of OHS are usually caused by a lack
of sleep and a lower than normal oxygen level in
your blood. Symptoms can include:
■ Daytime—sleepiness, lack of energy,
breathlessness, headache, depression
■ Nighttime—loud and frequent snoring during
sleep and/or breathing pauses when you stop
breathing for short periods of time
These may be concerning to your bed partner. Your
bed partner may be the only one who sees or hears
your nighttime symptoms.
Why is it important to know if I have Obesity
Hypoventilation Syndrome?
It is important to know if you have OHS because
OHS can be treated. If left untreated, OHS can be
life threatening or result
in the need to be in
the hospital for serious
complications. If left
untreated, the lack of
oxygen can put a strain
on your heart. When
treated, your symptoms
may be reduced or relieved entirely. Treatment
could improve your quality of life and decrease your
chances of further complications
due to untreated OHS.
Do we know what causes OHS besides
obesity?
The cause (or causes) of OHS are not fully
understood. OHS may be a combination of your
brain being unable to correctly manage your
breathing, excess fat producing hormones that
cause you to breathe ineffectively, and the extra
weight placed on your chest that makes it much
more difficult for you to breathe normally.
How is OHS diagnosed?
Your healthcare provider diagnoses your OHS by
first taking a complete history of your symptoms,
including your sleeping habits, checking your body
mass index (BMI), measuring your oxygen and
carbon dioxide levels. Your height and weight are
used to calculate your BMI. A BMI of 30 or over is
considered obese.
An online calculator for BMI is
available at http://www.nhlbi.nih.gov/guidelines/
obesity/BMI/bmicalc.htm.
Your oxygen and carbon dioxide levels are measured
by taking a blood sample from your artery, usually
your wrist. A pulse oximeter (a sensor lightly
attached to the finger) can be used to get an
estimate of the amount of oxygen (but not carbon dioxide) in the blood. Pulse oximetry however is not
as accurate as a blood sample from your artery.
A chest x-ray and pulmonary function tests may be
done to rule out any other causes of your breathing
difficulty. Although not necessary to diagnose
OHS, a sleep study is usually ordered (this is called
polysomnography). If you are suspected to have OHS,
you need to see if you have sleep apnea and how
severe it is. In addition, the sleep study may be used
to test levels of positive airway pressure (PAP) therapy
to treat OSA and hypoventilation during sleep.
How is OHS treated?
Treatment for OHS will include weight loss and
treating your sleep-related breathing disorder.
Sometimes, weight loss alone corrects many of the
symptoms and problems such as obstructive sleep
apnea. Therefore, the first approach to treating your
OHS is weight loss. Diet, exercise, and good sleep
patterns are important to help with weight loss.
Because OHS can cause serious health problems,
sometimes surgery is needed (e.g. gastric bypass
surgery) to help with your weight loss.
To treat your sleep-related breathing disorder,
you will probably need positive-airway pressure
(PAP) support. The types of PAP support include
Continuous PAP (CPAP) or noninvasive ventilation,
most commonly in the form of Bi-level PAP (BPAP).
Both are devices that deliver air to you through a
mask that you wear anytime you are sleeping or
napping. CPAP delivers air at a constant pressure
both when you breathe in and when you breathe
out. BPAP delivers higher pressures when you are
breathing in, than when you are breathing out.
Rarely, when OSA is severe, and not controlled with
PAP, a tracheostomy (surgical hole in the neck) may
be needed to ensure that your OSA is adequately
treated.
Research is being done to find medications to treat
OHS. So far, no medications are recommended for
the treatment of OHS.
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