Monday, February 1, 2016

Everything I Know (and Don’t Know) About Compression Garments - Part II

by Larry Creswell, M.D.

In part I of this article on compression garments I discussed some of the research on compression and performance/recovery. Here, I’ll cover compression, travel and your heart.

Compression Garments and Travel
I’m often asked about the benefits of compression garments (CG) to prevent DVT during long airline flights. In truth, the risk of DVT or pulmonary embolism (PE: having a clot dislodge from a vein and travel to the lungs) is actually quite small -- even for long flights. DVT probably occurs in less than 1 per 200 travelers for flights lasting more than eight hours and the rate of severe, symptomatic PE for flights greater than 12 hours has been reported at about 5 per 1,000,000 travelers.

Research indicates that these incidents occur more often in individuals who have an inherent increased risk (such as those with recent major surgery, active cancer, previous episodes of either DVT or PE, obesity, varicose veins). Conversely, travel-related DVT or PE is less likely to occur in the absence of these risk factors.

What to do? There is some evidence to suggest that maintaining mobility might decrease the risk of DVT or PE on long flights, so it is reasonable to recommend getting up and walking about the airplane cabin during long flights. Although there is no evidence that relates relative dehydration to travel-related DVT or PE, there’s probably little harm in heeding the often-mentioned advice of ample hydration. The routine use of CG is probably not warranted for most passengers, but their use might be encouraged for those at higher-than-usual risk of DVT or PE in combination with some form of pharmacologic therapy (such as anticoagulant or anti-platelet drug). That said, I realize that some people swear that wearing compression stockings during long flights leaves them feeling better on arrival… and there’s probably little downside to wearing them, even if there’s little benefit in terms of preventing DVT or PE.

Compression Garments and the Heart
Aside from the general observation that compression garments might enhance venous blood return to the heart in various populations with venous disease (an often stationary group of individuals), there are almost no data about the cardiovascular effects of compression garments. Two studies published this year are the first to examine the cardiovascular effects of CG during exercise.

In the first study, Sperlich and colleagues at the Institute of Training Science and Sports Informatics at the German Sports Academy in Cologne looked at the effects of calf-length lower extremity compression socks (in an assortment of degrees of compression) in runners during a period of running at approximately 70% of VO2max. The investigators found that the CG produced no cardiovascular effects (in terms of cardiac output, stroke volume, blood oxygen saturation, or blood lactate levels).

In a second recent study at the University of Otago, New Zealand, Braid MacRae and colleagues studied the effect of full body compression garments on cardiovascular function, thermoregulatory function, and performance in a group of recreationally trained cyclists. Each cyclist performed three separate 6km time trial cycling sessions on an ergometer with controlled atmospheric conditions:

  1. Wearing shorts
  2. Wearing properly-fitted compression whole body compression garments
  3. Wearing loose-fitting whole body compression garments.

The investigators found that during exercise, the properly-fitted compression garments produced an approximately 5% increase in cardiac output that was due to increased heart rate. There was a small increase in skin surface temperature in this group, but no change in the core body temperature (measured in the esophagus). There was no significant difference in the mean power output or time duration for the time trial among the groups. The authors concluded that the CG produced very little cardiovascular effect.

Because of the increasing popularity of CG, I suspect that we will see more studies in the near future about the cardiovascular effects of CG during exercise, in a variety of sports.

Summary
This really is everything I know (and don’t know) about CG. To summarize:

  1. The evidence suggests that CG probably produce little or no performance benefit
  2. CG may produce a recovery benefit
  3. CG may be useful for preventing travel-related DVT or PE in some higher risk individuals
  4. In the limited available studies, the cardiovascular effects of CG have been shown to be small

Larry Creswell, M.D., is a cardiac surgeon and Associate Professor of Surgery at the University of Mississippi Medical Center in Jackson, Mississippi. In addition to his regular column on Endurance Corner, he maintains The Athlete's Heart blog to offer information about athletes and heart disease in an informal way and to encourage exchange and discussion that will help athletes build a heart-healthier lifestyle. You can contact him at lcreswell@umc.edu.
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