Basic Principles of Denitrification

Article: George Petrou Photo: Greek Diver Archive

What is Decompression and Denitrification? I will give the answer, an explanation of the difference between these two concepts in a new article. Now let's look at our topic a little more simply.

Είναι η διαδικασία (Αποσυμπίεση) την οποία ενσυνείδητα ο αυτοδύτης εφαρμόζει με σκοπό την αρμονικότερη δυνατή αποβολή δια της εκπνοής του, του πλεονάζοντος Αζώτου (Απαζώτωση), και όχι μόνο, το οποίο διαλύθηκε / αποθηκεύτηκε μέσα στους ιστούς του κατά την διάρκεια της κατάδυσης / παραμονής και το οποίο σε περίπτωση κατά την οποία δεν αποβληθεί, πριν την ανάδυσή μας στην επιφάνεια, ο αυτοδύτης έχει πολλές πιθανότητες να εμφανίσει ένα σύνολο (ή μέρους) σημαδιών & συμπτωμάτων τα οποία ονομάζουμε Νόσο των Δυτών ή καλύτερα Νόσο εξ Ελλείψεως Αποσυμπίεσης. Σε αυτό το άρθρο συζητάμε για μερικές από τις Βασικές Αρχές Απαζώτοσης στις καταδύσεις με Μικτά αέρια.

     

Speaking with many scuba divers & instructors, I notice that there is a confusion or a paraphilology around the much-suffered topic of Denitrification. Because there are so many "unsafe opinions" circulating and because it is now established that many take the initiative (without possessing the necessary knowledge infrastructure, in principle) to apply or transmit some information or techniques, I consider it my responsibility to remind, recording by name once again clearly in this article, the Basic Principles of Denitrification (B.A.A).

Αυτές βασίζονται στις τελευταίες εξελίξεις που έχουν πιστοποιηθεί πρακτικά, και όχι μόνο θεωρητικά , από επιστήμονες, ιατρούς υπερβαρικής και εκπαιδευτές με εμπειρία τόσο στις ερασιτεχνικές αλλά κυρίως τεχνικές καταδύσεις (Για το ιατρικό θέμα οι ιατροί υπερβαρικής είναι οι μόνοι αρμόδιοι να έχουν άποψη). Αρχές που είναι γνωστές τα τελευταία 10 χρόνια. Τα τελευταία χρόνια μάλιστα επιβεβαιώνονται σε υψηλό ποσοστό. 

Εδώ προσθέτω και την μεγάλη προσωπική μου στατιστική παρατήρηση και εμπειρία, ιδιαίτερα στην εκπαίδευση αυτοδυτών αλλά και εκπαιδευτών τεχνικής κατάδυσης / μικτών αερίων σε βαθιές καταδύσεις.

Πάρα πολλά άρθρα με πολύ επιστημονικό υλικό (το οποίο ελάχιστοι καταλαβαίνουν) κυκλοφορεί στο διαδίκτυο ή στα περιοδικά. Υλικό το οποίο οι υπογράφοντες αυτού οφείλουν να προσδιορίσουν ότι είναι προσωπική τους άποψη και σε πειραματικό επίπεδο καθώς η πρακτική τους εφαρμογή είναι είτε ανύπαρκτη είτε περιορισμένης εφαρμοσμένης αποδεδειγμένης αξίας πολλές φορές.

Ας το πάω λίγο ανάποδα. ΤΟ ΤΙ ΝΑ ΜΗΝ ΧΡΗΣΙΜΟΠΟΙΟΥΜΕ.

So we had cases of Decompression Sickness due to using RGBM in an incorrect and incomplete manner (Ascent method with deep stops, or with many deep stops).

We had and unfortunately still have a disease with the use of any OC & CCR algorithm or system.

(Ανοιχτού η Κλειστού κυκλώματος).

Είχαμε και έχουμε Νόσο των Δυτών είτε με χρήση 100% Ο2 είτε ΕΑΝ80 στις ρηχές στάσεις.

We have extensive use of Helium (e.g. Trimix is not correct to take it as quickly as possible and leave it as slowly as possible, this is wrong. If it is possible, however, it should be done, it should only be done if there is complete, correct and certified knowledge) in deep dives with TRIMIX. But again, whatever method has been used, illness has not been avoided in some cases.

So nothing is completely safe, so no matter how dogmatic we are, it's good to understand this.

For this reason, it is useful to look at them as briefly as possible once again. And let us remember: why we are "loaded" with N2 (and other gases of course) and according to what law this happens.

ΔΠ = Διαφορά Πίεσης

I remember in our federation our late trainer and very good friend Nikos Anastasiadis.

telling us that everything is DP.

Πάντα τονίζουμε το θέμα της Δ.Π....δηλαδή πολύ απλά την Διαφορά Πίεσης  που υπάρχει κατά την κατάδυση,  παραμονή, ανάδυση και στη οποία και οφείλεται η διάλυση του αερίου (Ν2) στους ιστούς μας. 
«Προσοχή: για ευκολία κατανόησης του άρθρου δεν θα εμπλακούμε με έννοιες και διαφοροποιήσεις εννοιών όπως ταχύτητες, διαπερατότητες κυτταρικής μεμβράνης, εισόδου και εξόδου αερίων στα κύτταρα, διάχυση, διαλυτότητα, άρδευση, diffusion, perfusion κλπ»

During the descent, we therefore have the Environmental DP > (greater) than the tissue DP.

The result is that the tissues become charged, storing excess N2 in their attempt to equalize. Given the effect of Henry's law on gas solubility (the dissolution of nitrogen, helium or any other gas) we shoulder a series of obligations, during the ascent which are none other than those we call Decompression or Denitrification Procedures.

Στάση / Χρόνος/ Μείγμα / Συνθήκες περιβάλλοντος και Φυσιολογίας.

We remind you that in diving and deep mixed gas diving, we are not only concerned with Nitrogen with the well-known problems such as Diver's Illness, Nitrogen Narcosis, Dysbaric Osteonecrosis, O2 poisoning, but also with other gases and how they affect us.

Στην περίπτωση των εμπλουτισμένων μιγμάτων (EANitrox) μας απασχολεί η Τοξικότητα Ο2 του ΚΝΣ (Κεντρικού Νευρικού Συστήματος), η Πνευμονική Τοξικότητα (λιγότερο), και στη περίπτωση της χρήσης Ηλίου μας απασχολεί το θέμα το πόσο γρήγορα μπαίνει και βγαίνει στο κύτταρο (λιποδιαλυτούς ιστούς) Ποιά είναι η διαλυτότητά και η διάχυσή του σε αυτό. Κατά την ανάδυση το Ήλιο όμως βγαίνει από τα κύτταρα πολύ γρηγορότερα από ότι το άζωτο με τα θετικές και τις αρνητικές επιπτώσεις και κινδύνους. Μην ξεχνάμε την "προτίμηση" που έχει το Ήλιο στις αρθρώσεις, έσω αυτί (κοχλίας), λιπώδεις ιστούς κλπ.
Κατά την Ταχεία κατάδυση σε συνδυασμό με μεγάλες μερικές πιέσεις υπάρχει το πρόβλημα του HPNS από τα εισπνεόμενα αέρια. Όχι μόνο από το Ήλιο αλλά και από το Ο2 και Ν2. (επειδή αυτό μπορεί να προκαλέσει εντύπωση σε πολλούς αυτοδύτες τεχνικής κατάδυσης είμαι στην διάθεσή τους για επεξήγηση). Αλλά κυρίως είναι το Ήλιο.

Henry's Law (solubility)

Let us recall what Henry's law tells us in simple words. The amount of a gas (N2) that will dissolve in a liquid (blood) depends on the sum & and partial partial pressures of the gases that constitute it. On the pressure (partial pressure PPgas) of the gas (it is related to the percentage ratio of gas / depth). The summation - charging - storage of a gas depends on the type of tissue, and the residence time. We know that there are fast, medium and slow tissues with different half-saturation / saturation times.

The phases of our Nitrification are 2. (we put - we store)

1. The dive (pressure - depth - time) The decompression of a dive is only valid if we adhere to the descent plan. (If instead of diving to the pre-planned depth in e.g. 4 minutes I dive in 2 or 6, it is of great importance and makes a difference in the charge).
2. The stay (pressure - depth - time) Any temporal (and not only) variation of the above means a disturbance in the loading of our tissues with the consequence:

- Αύξηση χρόνου διαδικασίας Απαζώτοσης
- Ανάγκης Άμεσου Υπολογισμού νέου πλάνου ή Χρήση πλάνων εκτάκτου ανάγκης

Denitrification Phases

The phases of our Denitrification are:

1. Ανάδυση
   Σε αυτή την φάση απαιτείται ακρίβεια ως προς το ρυθμό ανόδου. 
2. Decompression Stops Stops must be characterized by 3 elements: - the completion of the required Decompression time - Deco - the correct depth - the quality of physiological conditions (e.g. hypothermia, dehydration, work production) - the correct mix during this time.
3. Surface Too often this phase is tragically omitted as everyone is concerned exclusively with what concerns the water. Wrong our denitrification continues especially after our emergence to the surface where the DP is at its peak. The DP of the environment is at its maximum > than the DP of the tissues. Therefore the size of the bubbles in a superlative degree.

So let's get to our topic.

Deep Decompression Stops or Reduced Gradient Bubble Model (RGBM)

...η αλλιώς θα λέγαμε ΠΟΛΥ σταδιακή μείωση / απομάκρυνση του Ν2, Ηλίου κλπ... σε μορφή φυσαλίδων. 

Το να μη δημιουργηθούν φυσαλίδες είναι αδύνατον.

Άρα η διατήρησή τους στο μικρότερο δυνατόν μέγεθος είναι μείζονος σημασίας. Για αυτό λοιπόν επιστήμονες / ιατροί /  ερευνητές σαν τον Wienke, τον Baker, τον Pyle, τον Hamilton, και άλλοι πολλοί άλλοι προτείνουνε την χρήση της μεθόδου των βαθιών στάσεων αποσυμπίεσης. Όχι των πολλών βαθιών στάσεων αποσυμπίεσης.

For example, we are doing a dive at X meters (always with an ideal mixture that ensures clarity and minimal risk of toxicity). Which ascent / denitrification method / procedure should I choose?

With the classic method where our electronic dive computers or our dive tables, depending on our time spent, give us stops at 6, 9 or 12 meters. Of course, it is a very incomplete method when we go really deep. And if I had to put a number, I would say after 50 meters, which has been proven to have immediate and long-term unpleasant results. It is not suitable for deep and mixed gas diving. Personally, I believe that it is not suitable for any amateur diving.

NOT RECOMMENDED: Deep stop method (The most "Advanced RGBM"), with a first stop at 80% of maximum depth (be careful, 80% is approximate, it varies depending on the time spent), and then stops every 3 meters of depth!!! For example, a dive, the first 100 stops at 80 meters and then 77, 74 meters and so on.

The above method is not recommended because:

a) staying so deep for a long time does not effectively contribute to more correct denitrification b) gas consumption is high c) the risk of cold (hypothermia) always exists d) difficulty in implementing (accuracy) a plan e) a long time of exposure of the scuba diver to great depth with all that this entails ... and other problems.

Ο πιο "Εξελιγμένος RGBM"...

a) What method of stops does it plan? It creates decompression stops at approximately 80% of maximum depth and then stops every 3 meters!!! NOT RECOMMENDED

b) how tested is it? Slightly tested, and of course its use is not recommended. And during its use we had many cases of divers' disease, and very serious ones at that.

c) what limitations does it have?

• The dive profile should be square without any form of “diamond.” The application of “diamond” has proven disastrous for many who either intentionally or unintentionally applied it.

•       Δεν επιτρέπεται πολύ επίπεδη κατάδυση

• No repetitive diving is allowed.

• The bottom mixture must be either Trimix or Heliox. Air or Nitrox are excluded.

• Ascent rates should be slow, 10 meters/minute and later... (don't overdo it)

• Remain in the decompression gas by surfacing for a period of time

• Avoid any form of fatigue/work production etc. for at least 24 hours!!

  Μέθοδος 60/50/40/30 και μετά ανά 3 μέτρα. Προτείνεται με δική σας ευθύνη.

It is a method that I have used a lot and I have always surfaced relaxed and NEVER with any signs or symptoms of illness or fatigue. It is clearly the safest and most effective method of decompression of any I have followed. Proven in practice with great statistical success. I have personally used it with absolute success and I recommend it. It is required to be a relaxed dive and not to miss any stops or decompression time.

If a Denitrification method with many deep stops is proven effective, what factors are sufficient reason not to implement it?

The difficulty of applying the ascent time from stop (depth) to stop and the time of the stop itself in terms of buoyancy accuracy. The lack of a comprehensive surface support infrastructure as well as decompression bars. Environmental factors Physiological factors Gas adequacy factors

Tables, Electronic dive computer or software?

It clearly has to do with the type of dive we will be doing. Attention: The fact that the Dive Computer has been decommissioned, or the time of the board or software does not necessarily mean that the diver has Decompression sickness. It is a minimal indication of mathematical proficiency.

In the case of deep diving with mixed gases, I personally use software to plan the dive, which plan I print out (of course with emergency plans / bail out if I exceed depth or time) and take a laminated copy with me underwater. A very good knowledge of mixed gas diving data & a very good knowledge of the software is required. Of course, the use of our dive computer is always essential, e.g. for my Trimix dives I use a Shearwater. I always have my beloved old Uwater Pro with me.

   

1. Is using air as a decompression gas advisable? Of course not. Not an ideal mixture..
2. Is the use of O2-enriched air recommended for decompression?

The use of enriched mixtures for the Denitrification process is a given. Many people believe that this is something new. In general, we recall that since 1959, when Nitrox was introduced, it has been an essential equipment, a safety tool for every scuba diver and is used in every form of diving, either as a diving gas or as a decompression gas. It goes without saying that air as a decompression gas should be eliminated and Nitrox should be used in its place. Air has the highest % N2 of any mixture, which makes it aggravating.

• Does the use of enriched mixtures (Nitrox) contribute to CO2 production? Of course not, but only in severe cases with a lot of O2.. In fact, we are in a better situation compared to the use of air in this regard.
• Rich decompression gas 100% O2 or EAN 80? The answer is absolute and one, that it works for everyone, Each mixture or gas has its own advantages or disadvantages.
• Factors such as CO2, hypothermia, dehydration, G6PD, PFO, Free radicals.CO... can dramatically affect my denitrification?
• Το CO2 προκαλεί αγγειοδιαστολή στα αγγεία του εγκεφάλου και αγγειοσύσπαση στα αγγεία του πνεύμονα διαταράσσοντας αρνητικά τόσο την φόρτιση όσο και την αποφόρτιση των ιστών. Όχι παραγωγή έργου.
• Hypothermia negatively disrupts both tissue loading and unloading.
• Η Αφυδάτωση επηρεάζει αρνητικά την απαζώτοση καθώς προκαλείται αιμοσυμπύκνωση. Η σωστή ενυδάτωση απαραίτητη.
• G6PD (Αφυδρογονάση της 6-φωσφωρικής γλυκόζης)
  Η έλλειψη του ενζύμου αυτού δεν είναι μόνο αντένδειξη για κατάδυση με χρήση μεικτών αερίων αλλά ευρύτερα και για απλή κατάδυση. Το ένζυμο G6PD βρίσκεται στα ερυθρά αιμοσφαίρια. Σε άτομα με ανεπάρκεια του ενζύμου μπορεί να προκληθεί οξεία αιμόλυση, ειδικά όταν πάρουν φάρμακα. Αρκετοί από αυτούς παθαίνοντας αιμόλυση παρουσιάζουν ίκτερο, αναιμία και αποβάλουν αιμοσφαιρίνη  από τα ούρα. Στην Ελλάδα η συχνότητα της πάθησης παρουσιάζεται περίπου στο 5,5% στα αγόρια και 1,8% στα κορίτσια. Τα άτομα που πάσχουν από αυτό θα πρέπει επιπροσθέτως να αποφεύγουν τροφές όπως τα κουκιά, και να μην έρχονται σε επαφή με ναφθαλίνη. Είναι επίσης ευαίσθητοι στο Σαλικυλικό οξύ.
• PFO (Atrial Fibrillation) In the case of a patent foramen ovale, it is not recommended to perform dives that require decompression (at the limits and beyond zero hour). We remind you that this communication is between the right atrium and the left atrium (Atrial Fibrillation) and not between the ventricles of the heart.
• Free radicals Although the issue of free radicals divides scientists, the destabilization of the charge of the O2 molecule should be addressed with antioxidants such as vitamin E, C and many fruits.
• CO
  Το μονοξείδιο του άνθρακος μειώνει δραματικά τη μεταφορά οξυγόνου στους ιστούς δεσμεύοντας την αιμοσφαιρίνη 200-300 φορές ισχυρότερα από το οξυγόνο.

Of course, there are many other factors that negatively affect our Denitrification process.

• What does Quality Decompression mean and how important is it?

Many scuba divers make the mistake of thinking that decompression is simply about completing time. Big mistake. Equally and perhaps more important are the environmental, physiological and psychological conditions during decompression.

• From what depth should I take the decompression mixtures during ascent?

A competent diver in buoyancy can use them from the depth that they have MP 1.6 atm. (Partial Pressure) so that they constantly have the greatest possible pressure when surfacing. Attention, buoyancy accuracy is required, it is not recommended for beginners. 1.4 is now safe for changing the mixture and surfacing. We have mentioned the limits of CNS (Central Nervous System) Toxicity as well as Pulmonary Toxicity in previous articles.

• Is it beneficial to use multiple Decompression mixes?

Changing many mixtures during the ascent to decompression can have beneficial effects but also very negative ones. It affects positively or negatively the proper functioning of the cell membrane. Absolutely correct knowledge is required.

• Is it true that the cells of the Nervous "tissue" die from violations and excessive exposures to Partial Gas Pressure and do not regenerate? From what doctors say, unfortunately yes. Although in recent years theories have emerged that confirm us about nerve cell regeneration and the fusion of nerve synapses. Great discussion....all of this.

• Does this information apply only to specialized mixed gas diving or even to simple recreational diving such as at depths of 18-30 meters?

Of course, these procedures should also be applied to recreational diving. For example, instead of surfacing after a timed dive at 30 meters for a stop at 6 meters or 3 meters for a while, it is preferable to surface by making stops at the following depths: 18 meters, 12 meters, 9, 6, 3 meters. A proven and highly effective method.

Χρήσιμες διευκρινήσεις

Compression Phase = Dive (Dissolution of N2 in tissues) Equalization / Absorption Phase = Bottom Time (Dissolution / storage of N2 in tissues) Denitrification Phase = Ascent (Tissue Unloading) Denitrification Phase = Decompression Stops (Tissue Unloading) Surface Denitrification Phase = Final and maximum tissue unloading - Denitrification PiN2 Inspired nitrogen pressure = Pressure of the N2 we breathe and which is applied as a force to the tissue / environmental PtN2 Tissue nitrogen tension = Internal tissue N2 pressure tension The pressure difference between PiN2 and PtN2 is the nitrogen exchange ratio in the tissues. Tissue Supersaturation PtN2 exceeds PiN2. Critical Supersaturation When PtN2 exceeds a critical value of PiN2, dissolved N2 may cause illness (DCI / Diver's Illness).

Attention:

Use what is proven to work and not what you hear. Do not become guinea pigs with unpleasant results that, if not immediately, will appear / accumulate in the long term. The use of all or part of the information and practices in this article requires either that the diver be certified for the level to which the information is addressed or that they be done under the supervision of a certified instructor. In no case is the information sufficient to carry out deep dives using mixed gases. The signatory of the article has no responsibility for the incomplete or improper use of all or part of these services.