Flying After Diving

At Shearwater, we place a high value in the work being done by the scientific community relating to diving and decompression theory.  We do our best to keep on top of what is going on in diving research.  A recent article in Divers Alert Network brings some new data to the discussion of flying after diving.

We are often asked why our computers do not display a “Time to Fly.”  It’s a good question.  Many people think it’s a simple calculation based on the theoretical tissue loading that we have to store to calculate decompression status.

When we looked to Divers Alert Network for advice, here is what we found:

DAN logo

 

Revised Flying After Diving Guidelines for Recreational Diving - May 2002

The following guidelines are the consensus of attendees at the 2002 Flying After Diving Workshop. They apply to air dives followed by flights at cabin altitudes of 2,000 to 8,000 feet (610 to 2,438 meters) for divers who do not have symptoms of decompression sickness (DCS). The recommended preflight surface intervals do not guarantee avoidance of DCS. Longer surface intervals will reduce DCS risk further.

* For a single no-decompression dive
, a minimum preflight surface interval of 12 hours is suggested.

* For multiple dives per day or multiple days of diving, a minimum preflight surface interval of 18 hours is suggested.

* For dives requiring decompression stops, there is little evidence on which to base a recommendation and a preflight surface interval substantially longer than 18 hours appears prudent.

These recommendations aren’t calculations based on the theoretical tissue load.  They are based on the type and duration of the diving activity, and a key factor that the computer can’t know – does the diver have symptoms of DCS.   We have chosen not to reduce these recommendations to a calculation and we ask our customers to evaluate their situation and use an appropriate preflight surface interval.

Massimo Pieri observes while Danilo Cialoni uses ultrasound to look for bubbles in a research subject’s heart during flight. (Photo from Alert Diver Online)

Massimo Pieri observes while Danilo Cialoni uses ultrasound to look for bubbles in a research subject’s heart during flight.
(Photo from Alert Diver Online)

In the Spring 2015 issue of Alert Diver, Dr. Petar Denoble reviewed some current research and asks whether the recommendations should be reviewed.  This research appears to be the first in-flight study of real-life dive exposures.

In the article, there were two insights that I found interesting.  The first was that in some of the subjects, bubbles were consistently detected on fairly typical recreational dives.  The second was that bubbles were detected on some of these same divers during a flight even after waiting 24 hours before flying after multiple days of no-decompression diving.

Dr. Denoble concludes, “Current guidelines recommend minimum preflight surface intervals before flying on commercial aircraft.  To be on the safe side, it is always better to wait longer.  This study has shown that a 24-hour interval is probably safe, but the 18-hour interval may deserve another look.  We hope this group will continue their research and provide more data to increase our confidence in answering these important questions.”

Read the whole article here:  DAN Flying After Diving Review

9 Responses

  1. Thanks Shearwater. I read the DAN paper and it looks like good research. What does your deco model predict regarding overpressure relative to the M value (I guess I’m asking for the gradient factor) after approximating the dive and fly profile? I know you’ll have to make quite a few guesses on dive as well as flight profiles but it’d be good to see if the model and the data are trending together.

    Thanks,

    Adam

    Reply
    • Bruce Partridge

      We recommend that divers follow the DAN guidelines. We don’t do any time-to-fly calculations on our products.

      Reply
  2. It is very simple feature to implement and it good thing for diver that he can just check if he can fly or not. On the front screen can be just an icon to show it. This would be really awesome. I know the DAN procedure but still would be nice to have 😉 i like my perdix 😉

    Reply
  3. Shearwater Research

    Ho Bojan,

    There are several calculations that would be fairly easy to implement. The problem is that the evidence for their accuracy is limited or non-existent. There isn’t a time-to-fly calculation that has stronger evidence than the DAN recommendation, so that is what we use. Below are the current recommendations on the DAN website:

    Revised Flying After Diving Guidelines for Recreational Diving – May 2002

    The following guidelines are the consensus of attendees at the 2002 Flying After Diving Workshop. They apply to air dives followed by flights at cabin altitudes of 2,000 to 8,000 feet (610 to 2,438 meters) for divers who do not have symptoms of decompression sickness (DCS). The recommended preflight surface intervals do not guarantee avoidance of DCS. Longer surface intervals will reduce DCS risk further.

    For a single no-decompression dive, a minimum preflight surface interval of 12 hours is suggested.

    For multiple dives per day or multiple days of diving, a minimum preflight surface interval of 18 hours is suggested.

    For dives requiring decompression stops, there is little evidence on which to base a recommendation and a preflight surface interval substantially longer than 18 hours appears prudent.

    Reply
  4. Actually you could implement this DAN recommendation just as is.
    Just identify the type of diving done recently and show the appropriate (possibly conservative, explain it in user manual) recommendation like printing, say, “> 24 hours” in case of deco dive.
    Though I appreciate your position.

    Reply
  5. Bruce Partridge

    Hi Bojan,

    The problem is that you are asking us to display a number when we don’t know what that number is. There is recent research that suggests that for “bubblers”, the time to fly may need to be longer. I have included a PubMed abstract from recent research than may be of interest to you.

    Diving Hyperb Med. 2015 Mar;45(1):10-5.
    Flying after diving: should recommendations be reviewed? In-flight echocardiographic study in bubble-prone and bubble-resistant divers.
    Cialoni D1, Pieri M2, Balestra C3, Marroni A2.
    Author information
    Abstract
    INTRODUCTION:
    Inert gas accumulated after multiple recreational dives can generate tissue supersaturation and bubble formation when ambient pressure decreases. We hypothesized that this could happen even if divers respected the currently recommended 24-hour pre-flight surface interval (PFSI).
    METHODS:
    We performed transthoracic echocardiography (TTE) on a group of 56 healthy scuba divers (39 male, 17 female) as follows: first echo–during the outgoing flight, no recent dives; second echo–before boarding the return flight, after a multiday diving week in the tropics and a 24-hour PFSI; third echo–during the return flight at 30, 60 and 90 minutes after take-off. TTE was also done after every dive during the week’s diving. Divers were divided into three groups according to their ‘bubble-proneness’: non-bubblers, occasional bubblers and consistent bubblers.
    RESULTS:
    During the diving, 23 subjects never developed bubbles, 17 only occasionally and 16 subjects produced bubbles every day and after every dive. Bubbles on the return flight were observed in eight of the 56 divers (all from the ‘bubblers’ group). Two subjects who had the highest bubble scores during the diving were advised not to make the last dive (increasing their PFSI to approximately 36 hours), and did not demonstrate bubbles on the return flight.
    CONCLUSIONS:
    Even though a 24-hour PFSI is recommended on the basis of clinical trials showing a low risk of decompression sickness (DCS), the presence of venous gas bubbles in-flight in eight of 56 divers leads us to suspect that in real-life situations DCS risk after such a PFSI is not zero.

    Reply
  6. I respect your point also, although I also think you can use DAN recommendation…eg.you can make airplane icon and next to it write “DAN 24h” – where time is changed depending on type of the actual dive(s)…this approach I believe would satisfy both parties – us, the consumers and Shearwater in its liability…

    Also, I would like to see some real time data showing calculation to which altitude would be safe to travel after the dive…I believe this would be easy to implement…

    Reply
  7. Nicolas Galmiche

    I would interested to hear your thoughts about this particular circumstance: I live in Switzerland at 1200m altitude and intend to do technical diving (40/50m range, OC on air + 1 deco gas) in lake Geneva sitting at 400m altitude, 30 minutes from my home town. How would you deal with “going back home” at a 800m altitude differential with regards to DCS risks?
    I use a petrel computer and have logged over 200 happy technical dives on it on 30/70 settings.
    Nicolas

    Reply
    • Shearwater Research Shearwater Research

      Hi, Nicolas.
      The altitude change you describe falls within the applicability limits for Guidelines proposed by DAN – cabins pressurized to an altitude equivalent to 610 m to 2438 m. Therefore the guidelines would apply to your case.

      Reply

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