Peter,

Good question so I'll start by saying I'm not a doctor and this is the kind of question you should ask your primary care physician or neurologist.

Having said that, I'm a retired Naval aviator and fighter pilot with over 3000 hours in Navy fighters flying on and off aircraft carriers for nearly 15 years.  All of that flight time was spent breathing 100% oxygen from takeoff to landing on missions lasting over two hours.  It was common to fly two missions a day and if you were lucky, three.  I can also attest to the fact that the flow rates we used were frequently well over 40 liters/minute at several points during each flight depending on the mission.  High G-Force air combat maneuvering created the greatest work and highest demand for oxygen and increased lung ventilation to remove carbon dioxide.

I've also used a method of oxygen therapy with flow rates that support hyperventilation for over 5 years to abort my cluster headaches and during high cycles, that can be an average of 3 to 4 attacks a day/24 hours. 

If this method of oxygen inhalation therapy is used properly, the average time to abort for pain levels 3 through 9 is 7 minutes.  I'm 65 years old, doing fine, and I still pass my annual physicals.

I'm not an isolated case.  Over 125,000 Navy and Marine Corps pilots flying tactical fighter and attack aircraft have been breathing 100% oxygen for over 70 years. 

All of us must pass an annual flight physical each year to remain on active flight status.  That physical involves a very thorough exam by a Navy Flight Surgeon, blood tests, hearing tests, and chest X-Rays.  If there was any lung damage, these X-Rays would have found it. 

On top of that there are annual requirements for aviation physiology training courses that include altitude chamber runs up to a reduced pressure equal to an altitude of more than 25,000 feet where we would take off our oxygen masks to experience hypoxia, ejection seat training, and water survival including runs in the Dilbert Dunker...

I've checked with the senior Flight Surgeons and Aviation Physiologists at the Naval Aerospace Medical Institute (NAMI) at Pensacola, FL and asked if there were any documented cases of Naval Aviators experiencing problems associated with breathing 100% oxygen.

The answer was no.  There were no instances of lung problems associated with 100% oxygen as long as procedures were followed and the total exposure time for continuous use did not exceed 12 hours.

The US Navy also mandates that all pilots and aircrew flying ejection seat equipped tactical aircraft such as the F/A-18 Hornet use 100% oxygen from takeoff to landing.

These aircraft cost from $40 to $60 Million dollars so the US Navy thinks breathing 100% oxygen is safe.

It's normal to experience a short period of coughing when using oxygen therapy.  I experience coughing nearly every time I start using this method of oxygen therapy to abort a cluster headache that woke me from sleep, but it always clears in 5 to 10 seconds.

Coughing during oxygen therapy can be due to two reasons.  These are the dryness of the oxygen where coughing occurs as soon as the dry oxygen reaches the lungs as you start to inhale, and a condition called atelectasis - where small areas of alveolar collapse have occured usually during sleep.  Aviators encounter a slightly different version of atelectasis during high G-Force maneuvers where several seconds of high G-Force squeezes the lung and some of the alveoli collaps.  As soon as the pilot relaxes the G-Force the first reaction is an uncontrollable urge to cough and the act of coughing re-inflates the collapsed alveoli. 

Nearly the same thing happens when using oxygen therapy immediately after rising from sleep only the coughing occurs as the lungs reach the point of being fully inflated.  This causes the collapsed alveoli to re-inflate and that sensation creates an uncontrollable urge to cough, further inflating any collapsed alveoli.

Again, coughing from either cause usually clears in 10 to 15 seconds and it occurs in both smokers and non-smokers.

I've also checked the results of the cluster headache survey taken by 1134 folks diagnosed with cluster headaches.  25% of the participants were currently using oxygen therapy and there were no adverse effects noted with its use

If coughing continues after a minute, call the primary care physician or neurologist who prescribed your oxygen therapy.

A feeling of tightness in the chest area is not a normal reaction to the use of oxygen therapy. 

A feeling of tightness in the chest area is very common when using triptans like imitrex or zomig...  That is the primary reasion I stopped using triptans to abort my cluster headaches and switched to oxygen.  With the exception of an occasional snort of imitrex nasal spray during airline travel, I use only oxygen inhalation therapy for my cluster headaches.  I take no other cluster headache medications.

Hope this helps.

Take care,

V/R, Batch   

Peter,

Coughing can be due to a number of reasons...  That it occurs most during a cluster headache bout might be a good clue.  Seeing your MD is always a good idea when things are not "normal." 

In the mean time look for other causes.  Check the filter in your air handler is also a good idea.

Take care,

V/R, Batch