Pneumothorax is frequently difficult to diagnose in the resuscitation room. Sometimes it is obvious, with a hypoxic patient and absent breath sounds. But not usually. Most of the time we rely on a chest xray to help make the diagnosis.
Unfortunately, the good old chest xray only shows a pneumothorax about 30-50% of the time. A big part of the problem is that our patients are usually supine to protect their spine. A small pneumothorax make float anteriorly in the supine position, and if it is not big enough to wrap around the lateral edge of the lung, it may remain invisible. So you need to look for gross and subtle signs on the image that will help make the diagnosis. The deep sulcus sign is one of the more subtle signs.
Simply stated, the deep sulcus sign is a radiolucent (dark) lateral sulcus where the chest wall meets the diaphragm. The amount of lung in this area is less, so a small amount of air will tend to darken the area making it more prominent. Look at patient left in the left photo, and compare to their right side. It is much darker and appears to extend lower than usual. In more extreme cases, the amount of air just above the diaphragm may make it appear inverted (right photo).
Bottom line: If you see a deep sulcus sign on the chest xray image, strongly consider pneumothorax. If the patient begins to have hemodynamic problems, needle the chest and chase with a chest tube. If they remain stable, the patient will still require a chest tube. Chest xray always underestimates the true size of the pneumothorax. Place the usual size chest tube and manage per your usual protocol. And, as always, use your best sterile technique and definitively identify the proper side before placing the tube.
Patients who have sustained a traumatic pneumothorax occasionally ask how soon they can fly in an airplane after they are discharged. What’s the right answer?
The basic problem has to do with Boyle’s Law (remember that from high school?). The volume of a gas varies inversely with the barometric pressure. So the lower the pressure, the larger a volume of gas becomes. Most of us hang out pretty close to sea level, so this is not an issue.
However, flying in a commercial airliner is different. Even though the aircraft may cruise at 30,000+ feet, the inside of the cabin remains considerably lower though not at sea level. Typically, the cabin altitude goes up to about 8,000 to 9,000 feet. Using Boyle’s law, any volume of gas (say, a pneumothorax in your chest), will increase by about a third on a commercial flight.
The physiologic effect of this increase depends upon the patient. If they are young and fit, they may never know anything is happening. But if they are elderly and/or have a limited pulmonary reserve, it may compromise enough lung function to make them symptomatic.
Commercial guidelines for travel after pneumothorax range from 2-6 weeks. The Aerospace Medical Association published guidelines that state that 2-3 weeks is acceptable. The Orlando Regional Medical Center reviewed the literature and devised a practice guideline that has a single Level 2 recommendation that commercial air travel is safe 2 weeks after resolution of the pneumothorax, and that a chest xray should be obtained immediately prior to travel to confirm resolution.
Bottom line: Patients can safely travel on commercial aircraft 2 weeks after resolution of pneumothorax. Ideally, a chest xray should be obtained shortly before travel to confirm that it is gone. Helicopter travel is okay at any time, since they typically fly at 1,500 feet or less.
Practice Guideline, Orlando Regional Medical Center. Air travel following traumatic pneumothorax. October 2009.
Medical Guidelines for Airline Travel, 2nd edition. Aerospace Medical Association. Aviation, Space, and Environmental Medicine 74(5) Section II Supplement, May 2003.
Okay, this is the last time I’m going to write about this. Hopefully I can provide the final nail in the coffin for this idea. Previously, the oldest paper I could find that was cited as a reason to use high inspired oxygen to treat pneumothorax was from 1983. I found what I think is the earliest (and the last that I will discuss) from 1971!
Twelve patients were retrospectively reviewed who recovered without intervention from a spontaneous pneumothorax. Another 10 were monitored prospectively with the same condition, but were given “high concentration oxygen” (??) by mask from 9 to 38 hours at a time. During intervening periods, the patients breathed room air. Daily chest xrays were obtained, and here is the cool part:
The inner edge of the chest wall and the outer edge of the lung were traced on transparent paper. This was then superimposed on graduated graph paper and the area corresponding to the pneumothorax cavity was measured. The rate of absorption was expressed in cm2/24 hrs.
Need I say more? The authors did show graphically that the apparent rate of absorption tripled in the treated patients, from about 5cm2/day to about 15cm2/day, and was higher in patients with a larger pneumothorax. The problem here is the same as before: chest xray does not allow volumetric estimates, so any results relying on them are suspect. At least it’s not a rabbit study.
Bottom line: There’s just no convincing data to support this practice, so let’s stop using it. Simple physics suggests that this should work, but the effect is just not clinically significant enough to offset the possibility of mishaps from an inpatient admission for oxygen therapy (see yesterday’s post). As I mentioned yesterday, look at the clinical status of your patient. If they have any detectable blood in their chest, they’ll probably need drainage. If not, and if they feel normal, discharge and follow up with a repeat xray in a week. The pneumo will probably be gone. If they do have some compromise, then insert the smallest tube you can. If done properly and a one-way valve can be used, the patient may still be managed as an outpatient.
One of my readers has pointed out that, yes, the evidence for using O2 to treat pneumothorax is poor, but practice and standard of care are not always driven by evidence. He also pointed out that it’s not really fair to condemn the use of this modality if there isn’t specific evidence showing that it’s bad. In other words, doing something that seems benign is okay if we can’t show that it’s harmful or at least prove that it’s actually benign. I don’t agree.
My point is that no intervention is truly benign. There are always potential complications for the things we do as physicians, sometimes physical, sometimes psychological. Putting a patient on O2 seems safe. But if used as a treatment for pneumothorax, it means hospitalization (which costs a lot of money), an IV (which could get infected), exposure to a lot of sick people (read MRSA and other fun bugs), lying in bed a lot more than at home (DVT), and on and on.
If the pneumothorax does not interfere with function and the patient has decent pulmonary health, why not send them home with reassurance and get a followup chest xray at some point to confirm resolution? If it does cause physiologic problems, or they have pulmonary disease and are likely to develop complications such as pneumonia, then admit for the least invasive treatment to quickly get it out (pigtail type catheter).
Since this topic just won’t seem to die, I’m going to try to kill the last papers I’m aware of on this topic today and tomorrow. Today’s was published in a pediatric surgical journal (!), and it’s another rabbit study. This one adds a wrinkle to the one I discussed yesterday. Not only did they inject air to create a pneumothorax (20cc this time), they punctured the pleura with a needle to create an air leak to simulate a real clinical problem.
They saw the same trend as posted yesterday, although the times were longer. Once again, resolution was measured with chest xray (performed every 12 hours this time). Unfortunately, 7 of the 27 rabbits used in each group died, leaving only 6 or 7 in each of 3 groups for analysis (room air, 40%, 60% O2). Even with wide standard deviations, the authors claimed significant differences in recovery.
Same problems as yesterday, particularly with how resolution of pneumothorax is determined. And don’t use rabbits! A bigger issue is that this is not really a clinically relevant model. First, creating an air leak would defeat the overall purpose of giving high O2 concentrations. If 60% O2 leaked into the pleural space, there would be less nitrogen to wash out so one would think that resolution would take longer. And no one would consider treating a patient with an air leak without some type of drainage device for fear of a tension pneumothorax.
Bottom line: Still not enough evidence to support this seemingly benign treatment. Tomorrow I’ll look at the (hopefully) last paper on the topic since the beginning of time, published in 1971.