Re: hypoventilation--articles

November 8, 2004

Bless your heart, Laurie, this is great help! I don't have either

but will look up the Quest issue online. I would like a copy of the

first one if possible. Do you have it in electronic form?

Thank you thank you!

Barbara

> Barbara

>

> I found the Quest article and another one I have on

hypoventilation. It is

> called " Oxygen is NOT for Hypoventilation in Neuromuscular

Disease " . The

> Quest one is called " A Breath of Fresh Air " . If you don't have

both of them,

> let me know if you need the first one. If you need the Quest

article, it is

> in the Vo. 5, Number 6, 1998

>

> laurie

November 8, 2004

-

Oxygen is NOT for Hypoventilation in Neuromuscular Disease

Spring 2000, Volume 14, No. 1

E.A. Oppenheimer, MD, FCCP

Editor's Note: The IVUN office continually hears from people with post-polio

or other neuromuscular diseases and conditions being inappropriately

prescribed O2 therapy. This anecdotal evidence (confirmed by the Mayo Clinic

case series) supports the need for accurate information from the physicians

most expert in the pulmonary aspects of neuromuscular disease to be

disseminated more widely to alert people to the reasons why they should be

wary of O2 therapy. If progressive respiratory failure occurs in people with

neuromuscular disease, an abnormal nocturnal oximetry study is often an

early indication that hypoventilation is occurring. There are significant

periods of decreased oxygen levels in the blood or hypoxemia during sleep

when lying flat, in addition to decreases in vital capacity (VC), maximum

inspiratory force (MIF), and maximum expiratory force (MEF). Decreased

oxygen saturation (SaO2) combined with increasing carbon dioxide (CO2)

retention or hypercapnia are the hallmarks of hypoventilation. This is

sometimes called ventilatory pump failure, due to the weakened respiratory

muscles.

Patients with neuromuscular diseases who are developing progressive

respiratory failure due to respiratory muscle weakness will die unless

mechanical ventilation is used. The rate of progression is often hard to

predict. Some patients seem suddenly to experience life-threatening

hypercapnic respiratory failure. They may not have been aware of gradually

increasing symptoms and signs, particularly since they are often not

physically active and are often not being regularly monitored with simple

pulmonary function tests.

Administering oxygen does not provide assistance to the weakening

respiratory muscles, but gives both the patient and the doctor the false

impression that appropriate treatment is being provided. While in fact,

hypoventilation is mistaken for an oxygen transfer problem. Indeed,

administering oxygen can mask the problem. Also there is a danger of causing

respiratory depression by giving oxygen. Oxygen is NOT the treatment for

hypoventilation. It will improve the SaO2, but not the hypoventilation and

may increase the danger of dying of sudden respiratory failure.

In hypercapnic respiratory failure due to hypoventilation, the SaO2 falls

due to the rise of the CO2. The alveoli in the lungs (tiny gas exchange

units) should clear most of the CO2 out with each breath. Instead, with

hypoventilation, CO2 accumulates and thus there is decreased room in the

alveoli for oxygen. When mechanical ventilation using room air is provided,

it lowers the CO2 in the alveoli, corrects the SaO2, and rests the

respiratory muscles. The ventilator should be adjusted to achieve a normal

SaO2, on room air. If oxygen is being administered, one cannot use

noninvasive oximetry to tell whether enough assisted ventilation is being

provided; repeated arterial blood gas specimens (ABGs) would be needed. When

there is respiratory failure in neuromuscular patients (ALS, post-polio,

SMA, muscular dystrophy, etc.) who have no additional pulmonary disease that

impairs oxygen transfer, the ventilator set-up is adjusted to:

be comfortable for the patient; achieve SaO2 of 95% or higher on room air

(this can bemeasured with a finger-sensor oximeter); assist the patient to

effectively cough and clear secretions; provide improved oral communication

(if vocal communicationis possible). It has been common for people using

noninvasive nasal ventilation (NPPV) with a bi-level positive pressure unit

to use inadequate settings; frequently, they are not monitored with clinical

evaluation and oximetry. The EPAP is often set too high usually it should

not be higher than 3-4 cm H2O; the IPAP is set too low usually it needs

to be 12-16 cm H2O and adjusted to achieve an oxygen saturation of 95% or

higher. Some situations may require administering oxygen, such as pneumonia

due to infection or aspiration. If this occurs in patients with respiratory

muscle weakness and hypoventilation, then it is important to provide both

assisted ventilation and supple-mental oxygen, and use ABGs to monitor them.

Address: E.A. Oppenheimer, MD, FCCP, Pulmonary Medicine

(eaopp@...).

>

> Reply-To:

> Date: Mon, 08 Nov 2004 17:58:03 -0000

> To:

> Subject: Re: hypoventilation--articles

>

> Bless your heart, Laurie, this is great help! I don't have either

> but will look up the Quest issue online. I would like a copy of the

> first one if possible. Do you have it in electronic form?

>

> Thank you thank you!

> Barbara

>

November 8, 2004