Question New to Peregrine...is the only ascent rate display the colored chevrons [each 3m/min]?

[inquis]

since my dives are both at SL and high altitude I am very focused on my ascent rates and accurate safety stop depths

Have you considered that ascent at a constant rate yields an INCREASING rate of volume expansion. For example, at a 33 fpm ascent rate, any microbubbles expand by 0.4% per second at 100 fsw and 0.9% per second at 30 fsw -- more than double the expansion rate. Altitude makes it even worse.

There are numerous anecdotal reports that people feel better after ascending more slowly as they near the surface. I highly doubt that is a coincidence.

 

[Wallowa]

So using that chevron bar display to monitor "going slow" means keeping a maximum 1 bar showing on ascent. Is that not an unreasonable strategy?

As always it will be your call....but one chevron =10ft/min ascent....up "shallow" that might be 'reasonable' but at depth that rate may allow more on-gassing than the algorithm can't adjust to or reflect in the display....I see it as either you follow the design of the computer or you don't....if I don't then I am making the determination that my judgement supersedes the algorithm designed profile.

No free lunch or way to assure that by not following the dictates of the computer you are safer. Even if we devise a way to avoid crossing the M value threshold of any tissue ascending or at the surface we still can suffer DCI; trust with verification is damn near impossible as asymptomatic DCI may well be the rule rather than the exception.

If Peregrine dictates that the nominal ascent rate is 33ft/min then for me that is the rule, not the exception.

After receiving the welcomed information on this thread that the ascent rate can be displayed, I poured through my PDF Peregrine manual and found this: Page 13 lists the displays available for "Configurable Info Row" and it does state that there is a "Rate" display [image shows a descent rate]. Pages 15 & 16 listed the "Info Screen Descriptions" and list all those on page 13 EXCEPT "rate". I should have picked up on this information or played with my Peregrine enough to find the "rate" option; my error. So I have a metric display for ascent and descent rates now centered in the bottom display row. Thanks I learned from that.

Oh, forgot, on page 22 of manual there is listed a "Primary Notification" warning for "Fast Ascent"; for "ascent sustained as faster than 10m/min {33ft/min}". The warnings are "listed" with "highest priority notifications first" and of the 11 warnings listed "Fast Ascent" is 4th if I am interpreting that correctly.

 

[inquis]

Have you considered that a constant ascent rate yields an INCREASING volume expansion rate? A 33 fpm rate, any microbubbles present expand at 0.4% per second (100 fsw), 0.9% per second (30 fsw), and 1.3% per second (10 fsw). Ascending from the safety stop at 33 fpm is unnecessarily risky, in my view. Numerous anecdotal reports of less fatigue agree with this stance. Google subclinical DCS some time.

 

[Wallowa]

Have you considered that a constant ascent rate yields an INCREASING volume expansion rate? A 33 fpm rate, any microbubbles present expand at 0.4% per second (100 fsw), 0.9% per second (30 fsw), and 1.3% per second (10 fsw). Ascending from the safety stop at 33 fpm is unnecessarily risky, in my view. Numerous anecdotal reports of less fatigue agree with this stance. Google subclinical DCS some time.

Ok, I would never step in front of anyone's decisions on an assumption of risk and how they choose to conduct their dives. I am a big believer in individuals making their own decisions.

Yes, of course the relative pressure change and hence volume gradient of expanding material [bubbles] increase as you rise in the water column and reaches maximum expansion values nearest the surface.....I was not referring to expansion or absorption of micro or macro bubbles but rather the on and off gassing of tissues, which may or may not promote or increase actual bubble or nuclei growth.

The issue with all this guessing about what constitutes an optimal ascent rate is that nobody actually has test data that nails down exactly what transpires in the tissues including blood with differing ascent rates at differing depths, only suppositions based assumptions. Sure gases expand when ambient pressure decreases but idea is to limit growth of bubbles or even bubble formation in concert with micro nuclei presence not just how rapidly they form. Tons of variables contribute to DCI and bubble formation is just one.

The rate of on gassing and off gassing is a balancing act. At any depth and at any rate of descent or ascent tissues are simultaneously on gassing and off gassing, it is not an either/or. The empirical unknown at any time during a dive is what tissue is the critical or controlling tissue that could produce DCI; algorithms in the end are only assumptions of 'best case' based on mathematical models trying to coincide with currently known theories of physiological and physical parameters affecting a diver under hyperbaric and hypobaric conditions while breathing an array of gases.

So, we divers hopefully will digest what is published and balance that against our common sense to arrive at how much risk we will assume. In '55 we were told the best ascent rate was 25ft/min or just follow your smallest bubbles; even when we were diving at Tahoe 6,000 ft ABSL and diving to 200ft. What saved us was diving with at most 67cf in steel 72s; rocketing down, pull J valve when breathing got hard and slowly ascending, with no idea of our ascent rate. Where is the definitive information concerning ascent rates vs not generating DCI? It does not exist and may never. Super imposed is the widely different individual physiological, psychological, fitness and health status of each one of us that change over time and are unpredictable causative factors. Anecdotal information may indeed point to "the answer" but verification of assumptions is the safe way to proceed. Or not. Individual choice.

Will all divers suffer some degree of physiological deficit over time? Sure, but for me it has been well worth it.