Iii songs from the 1960s and '70s. One is nearly the wonders of nature in the imperial Rocky Mountains, another an instrumental rock tune, and the third a ballad about going off to the Vietnam War. What do these songs take to practise with gas bubbles in the middle?

As a retina surgeon in Denver, I innovate the classic gas chimera to the Rocky Mountains on a regular basis. This situation is not unique to Colorado; it occurs in every state that has mountains. Although other mountain ranges may not be quite equally towering as the Rockies, they are certainly high enough to pose a danger to gas-filled optics.

AT A GLANCE

• It is of import to consider patient travel plans and situations before inserting a gas bubble later on vitrectomy.

• Silicone oil is an option for patients who cannot avoid air travel earlier a gas bubble would have time to misemploy.

• Know your local geography so that you tin warn patients of potential trouble spots.

ADDRESSING Distance Bug

How do nosotros address these distance issues? The mount issue may not be relevant to retina surgeons in much of the country, but air travel is ubiquitous and an outcome for patients everywhere who are leaving for somewhere on a jet plane.

In this article, I share thoughts, tips, and tricks on this topic with the retina community at large because these issues are not unique to Colorado.

For those who have forgotten their high school and higher chemistry, allow me to refresh your memories. Recollect Boyle'southward law? In simple terms, pressure and volume are inversely proportional in relation to gas. As the pressure on a gas bubble decreases, its volume increases. Higher distance ways lower atmospheric pressure and a bigger gas bubble.

Without delving too securely into the weeds of physics and chemical science, hither are a few simple numbers. A gas or air bubble at sea level will expand by 1.25 times at v,000 feet, one.5 times at ten,000 anxiety, and ii times at 18,000 feet.one

Only mount climbers need business organisation themselves with elevations of 18,000 anxiety or more. The highest paved road in the United states of america is the i leading to the top of Mountain Evans in Colorado, at 14,130 feet. The highest The states interstate highway pass is the Eisenhower Tunnel along I-lxx in Colorado, at 11,158 feet. From Denver, the Mile-High Urban center at 5,280 feet, there is a 6,000-foot acme alter that tin happen in less than an 60 minutes driving west on I-70, with a resulting 25% to 30% increase in bubble size in a patient with intraocular gas.

A number of other states besides take mountain passes over v,000 feet.2 Hence the concern. With good outflow, an eye tin can tolerate these changes in distance without a trouble. But in other eyes, specially the eyes nosotros operate on, this may not be the case.

Researchers in Mexico City, using a rabbit model of intraocular gas and mount travel, estimated an increase of 1.v to two.0 mm Hg in force per unit area in man eyes for every 100 m of altitude increase.3 That is about a 5 mm Hg increase per 1,000 feet.

Later on takeoff, commercial airplanes accomplish cabin pressure level at cruising altitude equivalent to the pressure at 6,000 to eight,000 feet summit within x to 15 minutes.4 At this rate, a gas chimera in an eye taking off from sea level would exist 30% to forty% larger within minutes.

RECOMMENDATIONS

Let'south exit the science behind and become down to practicalities. What should we recommend for patients who need an air or gas bubble and also need to travel into areas of high distance or by air?

For patients visiting Colorado, or anywhere else for that affair, there is always the option of returning abode for their surgery rather than having it where they are visiting, avoiding the result birthday. Obviously, this depends on surgical urgency, the logistics of returning home, and where home is. Information technology's much easier to get a flight from Denver to Chicago than from Bangkok to New York.

Another selection is to employ silicone oil instead of gas or air. Patients are gratis to wing with silicone in situ, just this involves the tradeoff of requiring a 2nd surgery in the future to remove the oil. For someone who has simply begun a family unit ski holiday in Colorado and who presents with a retinal disengagement, oil is a good option. The patient tin can stay with his family unit while on vacation and render home with them, rather than staying in Denver while the family is off skiing and and so having to drive abode to avoid air travel.

For a patient with a gas bubble in his or her eye, how soon can she fly or travel through the mountains? This is a more challenging question.

For complete condom, one should not change distance with any gas in the eye. Then again, for consummate safety, one should neither fly nor drive in the mountains. But that'south not practical.

Elective travel can be delayed until the bubble is completely gone, merely what about those who can't delay travel?

For aeroplane travel, the answer is piece of cake. No flying until the bubble is gone, without exception. Fifty-fifty a small bubble may expand plenty for a dangerous IOP elevation, particularly in an eye with impaired outflow. One can turn around on the interstate and get to a lower elevation, just it'southward not and then easy on a aeroplane, particularly over the ocean. Why risk information technology?

A patient with a small-scale bubble flying out of Denver may get away with information technology because cabin pressure is inside a couple of thousand feet of the airport's superlative. But what if the unforeseen happens? A plane may be diverted to an airdrome at sea level, causing temporary bubble expansion, then take off again shortly thereafter and get from body of water level to 8,000 anxiety motel pressure in a few minutes. In such a case, the bubble becomes a large trouble.

Airlines by and large respond favorably to a annotation from the medico explaining why the passenger tin't fly and needs the fare refunded or the trip rescheduled.

DRIVING TO HIGHER ALTITUDES

What about driving? Non only from Denver, merely from Phoenix, Los Angeles, Common salt Lake Metropolis, and other cities well-nigh mountain passes.

Climbing slowly enough, any elevation alter is tolerable because the eye will equilibrate. But past slowly I hateful walking, not driving. Again, not practical.

I prefer to wait until the bubble is 50% volume or less earlier assuasive patients to drive to higher altitudes. I give the patient 500 mg oral acetazolamide (Diamox, Teva Pharmaceuticals), assuming no contraindications, to take about an 60 minutes earlier travel, to lower IOP and provide a absorber of safe. I also propose patients to use either their automobile's navigation organisation or a smartphone app to determine elevation. At that place is a free app called My Distance, and I'm certain there are others.

I instruct patients to pull over for 10 to 15 minutes later on each 500-pes elevation gain, giving time to equilibrate to an expected 2 to 4 mm Hg IOP rising. Going downhill, they can literally fly, watching for police traps rather than their altitude, because the chimera will shrink during descent.

Information technology'due south likewise important to educate patients virtually the symptoms of elevated IOP, such as pain, pressure, and decreased vision. Tell patients that, in the event of such symptoms occurring, they should turn around, go downhill until the symptoms subside, await for one-half an hour, and endeavour the ascent again, but more than slowly.

WAIT FOR 50%

The waiting menstruum for a 50% bubble is the hard office for many patients. I utilize SFsix routinely—never CiiiFeight—and then the wait is only almost i week. The await would exist much longer with CiiiFviii. Air, if it will provide acceptable tamponade, is another choice with a shorter waiting period.

Playing with the percent of chimera fill at the end of surgery or adjusting the gas concentration are other ways to get to a fifty% bubble sooner. However, fixing the eye is the priority. Do not shortchange the tamponade and end upward needing another surgery.

Pneumatic retinopexy is some other shortcut in appropriate patients. A pocket-size amount of pure gas combined with oral acetazolamide, as noted above, will ordinarily be safe for mount travel, but information technology is not prophylactic for air travel.

KNOW YOUR GEOGRAPHY

Finally, know your geography and potential trouble spots. State departments of transportation publish pass elevations,5 and knowing local quirks tin can be helpful. For example, in Denver, I-25 runs northward to southward. In that location is a big colina on the trip south to Colorado Springs and another heading north, entering Wyoming. Both could cause problems in an eye with a complete gas make full. Know your local take a chance spots.

I hope this article has provided some insights into dealing with the "Classical Gas" bubble meeting the "Rocky Mountain High" or "Leaving on a Jet Plane."

ane. Johnson-Joseph L, Kelso L, Marshall L. Alaska Air Medical Escort Training Transmission. 4th ed. Juneau, AK: Dept. of Health and Social Services, Division of Public Health, Section of Injury Prevention and EMS; 2006:57-70. dhss.alaska.gov/dph/Emergency/Documents/ems/assets/AirMedCourse/EMS-E_Chapter3.pdf. Accessed July 19, 2018.

ii. Highest Paved Roads of the U.s.a.. Dangerous Roads website. dangerousroads.org/north-america/united states/1610-highest-paved-road-list-in-u.s..html. Accessed July xix, 2018.

3. Fromow-Guerra J, Meza-de Regil A, Solís-Vivanco A, et al. The effect of altitude on intraocular pressure in vitrectomized eyes with sulfur hexafluoride tamponade by the Friedenwald Method: rabbit animal model. BioMed Res Int. 2016:7326160.

4. International Travel and Wellness. WHO website. who.int/ith/mode_of_travel/cab/en/. Accessed July nineteen, 2018.

v. Maximum Grades on Colorado Mount Passes. Colorado Department of Transportation website. codot.gov/travel/maximum-grades-on-colorado-mount-passes.html. Accessed July 19, 2018.

Brian C. Joondeph, Dr., MPS
• Partner, Colorado Retina Associates, Denver, Colorado
• bjoondeph@retinacolorado.com; Twitter: @retinaldoctor
• Fiscal disclosure: None