"I was reading a discussion about CPAP pressure on an online CPAP forum the other day and was surprised to read a post from a person claming to be a clinical CPAP expert who suggested CPAP therapy can be very dangerous, and that the wrong pressure setting can lead to a condition known as pneumothorax. This fairly strong assertion wasn't backed up by any data or even by any anecdotal experience, and the poster - who chose to remain anonymous - became somewhat of a victim of the responses of the more level-headed message posters. Of course, the people using common sense along with their own experience pointed out that CPAP therapy is very safe, and asked what all the nonsense was about CPAP-induced pneumothorax.

After reading the messages I decided to look into a couple of issues. First, I wanted to know more about pneumothorax and what causes it. Second, I wanted to know how much pressure - in more commonly understood terms - a CPAP machine really delivers.

A pneumothorax is a pocket of air inside the pleura which causes a collapse of the lung. The pleura is a thin protective covering made up of two layers of tissue filled by fluid. When air enters the pleural cavity, the pressure becomes greater than the pressure inside the lungs, thus causing a partial or full collapse of the lungs. Several things can cause a pneumothorax, and there are three different categories of pneumothorax.

Spontaneous Pneumothorax
A spontaneous pneumothorax is categorized when the cause of the collapsed lung is not trauma. Spontaneous pneumothorax can occur when a weak part of the lung ruptures for whatever reason - including reasons related to lung disorders like chronic obstructive pulmonary disease (COPD) - or when significant pressure changes occur in the lungs.

Traumatic Pneumothorax
A traumatic pneumothorax may be caused by a traumatic injury to the chest and lungs, or by an invasive medical treatment that introduces air into the pleural cavity.

Tension Pneumothorax
Tension pneumothorax is the most serious and dangerous pneumothorax condition, and it describes a pneumothorax in which the tissue through which the air is entering the pleura acts as a valve which prevents air from escaping. Tension pneumothorax can cause an extremely high pressure to occur in the pleura causing the lungs to collapse completely.

So the real question at hand is can CPAP therapy cause a pneumothorax? The aforementioned message poster which claimed this was a potentially very serious consequence of patients adjusting their own pressure settings, believed firmly that unsupervised CPAP therapy can cause a pneumothorax. After the little bit of research I've conducted on the topic it seems to me that just about anything can cause a pneumothorax, including genetic defects, deep sea diving, high altitude flying, getting hit in the chest with a baseball bat, and just sitting idly in a chair (the latter especially if you have some sort of lung disease). In fact, from what I've read, most cases of spontaneous pneumothorax don't occur during physical exertion.

My fairly uneducated hypothesis, then, is that CPAP therapy could potentially (I'm using the word ""potentially"" very liberally here) induce a pneumothorax, but it would be very unlikely to be the root cause of the pneumothorax. If your lung is going to rupture from CPAP therapy, I'd guess it would probably rupture all by itself, even without CPAP therapy.

The unit of pressure used for CPAP machines is generally centimeters of water or cm H2O. Most people don't really relate too well to that unit of measurement since very few other things we encounter in daily life are described using those units. So I decided to show you all how to convert cm H2O to PSI, or pounds per square inch. Many people in the United States are familiar with the PSI unit of measurement, and as you'll soon see, a CPAP machine delivers a very, very low pressure. All you have to do to see your CPAP pressure setting in terms of PSI is to enter your pressure setting in the text box below, and you'll see the corresponding pressure in PSI. For example, a CPAP machine pressure setting of 8 cm H2O is 0.11 PSI - a low pressure indeed.

cm water (4°C):
psi [psi]:
© unitconversion.org

According to the Encyclopedia Britannica, ""pressures within the lungs can be raised to 130 centimetres of water"". The human lungs can normally withstand the relatively low and safe pressure settings commonly used in CPAP therapy.

I'd encourage you to talk more with your physician if you're concerned about pneumothorax. In the meantime, you should feel pretty comfortable knowing that CPAP machines don't produce what would be considered to be dangerously high levels of pressure for most CPAP users. And don't forget about the very well-known benefits of CPAP therapy - benefits that far outweigh the dangers of using it. As a matter of fact sleep apnea is a condition that has been shown[1] to be a factor in car crashes, diabetes, pregnancy complications, high blood pressure, and heart disease.

The bottom line for most is that CPAP therapy is not only extremely effective, but it's also very safe.

Andrew Senske

[1] The list of risks associated with sleep apnea was partially developed after reading the following article, published at WebMD.com: Sleep Apnea Death Risks, by Salynn Boyles, WebMD Medical News, May 22, 2007

CPAP-Supply.com is a leading online retailer of CPAP equipment. Located in Spokane, WA CPAP-Supply.com has been serving thousands of customers around the world since 2001. Founded on a belief that patients are their own best primary care providers, CPAP-Supply.com understands the importance of educating patients and customers on both the effects of and treatment for obstructive sleep apnea. For more information visit CPAP-Supply.com or call toll free 1-888-955-2727."

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