Clinical
Practice Guideline
for
SPONTANEOUS PNEUMOTHORAX
Developed
for the
Aerospace
Medical Association
by their
constituent organization
American Society of Aerospace Medicine Specialists
Overview: Spontaneous pneumothorax is best defined
as “air in the pleural space of nontraumatic cause.” Secondary spontaneous pneumothorax is one
that occurs in the presence of underlying parenchymal or airway disease, and
for aviation purposes will not be considered further. Primary spontaneous pneumothorax, by default,
is one that occurs in the absence of such underlying disease. However, it would be incorrect in such cases
to define the lung as normal, since the vast majority proves to have visceral
subpleural blebs at thoracoscopy.
Primary spontaneous pneumothorax typically peaks in the 16 to 24 year
age group, affecting males about 5 to 10 times more frequently than
females. Although the incidence in the
general population is usually quoted as 9 per 100,000, the real incidence is
probably higher. In most large series, 1
to 2% are incidentally found on chest film; since
small pneumothoraces resolve themselves within a few days, the odds of
identifying an asymptomatic pneumothorax in this way are slim, arguing that the
disease is probably more common than thought.
A specific
subcategory that deserves mention is catamenial pneumothorax. This is a spontaneous pneumothorax occurring
in a female within 48 to 72 hours of the onset of menses. Although these are often ascribed to
endometriosis, pleural endometrial implants have been identified in only a
third of patients. It is important to
question any female with a spontaneous pneumothorax about the timing in
relationship to menses, since the initial treatment of catamenial pneumothorax
is hormonal. Should the patient fail a
trial of contraceptive steroids, this disorder responds well to the same
prophylactic surgical treatments described below.
Depending
on the size of the pneumothorax, acute treatment may consist of observation,
usually combined with oxygen, which hastens resolution; simple aspiration of
the air, which is successful about 65% of the time; or catheter or tube
thoracostomy. (Since these are usually
“air only” pneumothoraces, a small catheter with a Heimlich valve is usually
successful, and much more comfortable than a standard chest tube.)
The major
issue is recurrence. After an initial
pneumothorax, the chance of recurrence is 20 to 50%, a risk that rises after
subsequent episodes. (After two
pneumothoraces, the risk of a third is 62%; of those who have had three
episodes, 83% will have a fourth.) The
clinical standard of care for a number of years has been to perform a
definitive surgical procedure after the second pneumothorax, but with the
availability of thoracoscopic pleurodesis, there are many who feel that surgery
is indicated after the first episode, particularly in those who are at high
risk because of their occupation or because of travel to remote areas.
Aeromedical Concerns: The most likely symptoms are chest
pain and dyspnea, either of which could be incapacitating. In a review by Voge and Anthracite of 112
aviators with spontaneous pneumothorax, 37% admitted they could have been
incapacitated had the episode occurred during flight. Overall, seventeen percent of the episodes
occurred under operational conditions.
Eleven percent actually occurred during flight, although it was unclear
how many of these resulted in mission aborts.
Of note, another 6% occurred in the altitude chamber, and all but one of
those occurred after rapid decompression.
Treatment and Aeromedical
Disposition: After
complete resolution of a first episode of pneumothorax, the aviator may be
returned to flying status without waiver, if a high resolution CT scan
demonstrates no pathology, such as blebs or underlying parenchymal disease,
which might predispose to recurrence.
After a second pneumothorax, or if CT demonstrates residual blebs,
waiver may be considered only after definitive surgery to prevent
recurrence.
This is
pretty much the protocol in the FAA. The
civil airman must demonstrate that they have had some definitive treatment
after a second pneumothorax.
Experience: The US Air Force Aeromedical
Consultation Service has recently reviewed the available literature regarding
definitive treatment of spontaneous pneumothorax. Thoracoscopic abrasive pleurodesis appears to
be the procedure of choice, with minimal morbidity and a recurrence rate under
5%. Open pleurodesis showed a similar
recurrence rate, but is accompanied by greater morbidity. Pleurectomy, whether through thoracotomy or
thoracoscopy, offered no additional benefit, at the cost of additional
morbidity. Talc poudrage showed variable
results, but the only sizable series demonstrated a recurrence rate of
12%. Furthermore, talc administration
has some inherent disadvantages, such as the long term risk of pleural
fibrosis, which renders its use questionable in the relatively young aviator
population. Chemical pleurodesis with
tetracycline or similar compounds results in an unacceptable rate of
recurrence.
In summary,
any form of definitive surgical pleurodesis is acceptable for waiver, but
thoracoscopy abrasive pleurodesis appears to offer the best combination of
efficacy and minimal morbidity. Chemical
pleurodesis with tetracycline compounds is not acceptable for waiver. Talc pleurodesis is not recommended, due to
borderline efficacy and the risk of long-term complications.
As of
November 2005 the FAA has 303 first-, 198 second-class, and 361 third-class
airmen currently issued with a diagnosis of pneumothorax either one or
multiple.
References:
Baumann MH,
Strange C. Treatment
of spontaneous pneumothorax—A more aggressive approach? Chest 1997;112:789-804.
Melton LJ, Hepper NGG, Offord KP.
Incidence of spontaneous pneumothorax in
Paape K,
Fry WA. Spontaneous
pneumothorax. Chest
Voge VM,
Anthracite R. Spontaneous pneumothorax
in the USAF aircrew population: a
retrospective study. Aviat
Space Environ Med 1986;57:939-49.
August 1,
2006