Autorespiratore a riciclo (ARR): aspetti medici
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Intervento del Dr. Pasquale Longobardi al XIX Congresso Nazionale Società Italiana Medicina Subacquea e Iperbarica (SIMSI), Verona 18-21 novembre 2010
![AutoRespiratore a Riciclo (ARR): aspetti medici Pasquale Longobardi Centro Iperbarico Ravenna Master Med. Sub. Iperb. Scuola Sup. S. Anna (PI) Accademia Scienze e Tecniche Subacquee di Ustica E-mail: [email_address]](https://image.slidesharecdn.com/immersionetecnica11-10-101203031411-phpapp01/85/Autorespiratore-a-riciclo-ARR-aspetti-medici-1-320.jpg)
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Autorespiratore a riciclo (ARR): aspetti medici
- 1. AutoRespiratore a Riciclo (ARR): aspetti medici Pasquale Longobardi Centro Iperbarico Ravenna Master Med. Sub. Iperb. Scuola Sup. S. Anna (PI) Accademia Scienze e Tecniche Subacquee di Ustica E-mail: [email_address]
- 2. autorespiratore a riciclo (ARR) “macchina” + uomo
- 3. pain
- 5. N. Donda gain CO 2 O 2
- 6. N. Donda autorespiratore a riciclo semichiuso OEA (max 40 mt); trimix CO 2 sacco polmone FILTRO OEA /Trimix
- 7. autorespiratore a riciclo chiuso N. Donda CO 2 sacco polmone FILTRO DILUENTE OSSIGENO CONTROLLO
- 8. Mk5P Ouroboros
- 11. COMPOSIZIONE DELL'ARIA e DEL SANGUE valori approssimativi di un soggetto maschio sano al livello del mare GAS aria atmosferica (secca) aria umidificata aria alveolare mm/Hg % mm/Hg % mm/Hg % N 2 597 78,62 563,4 74,09 569 74.9 O 2 159 20,84 149,3 19,67 104 13,6 CO 2 0,3 0,04 0,3 0,04 40 5,3 H 2 O 3,7 0,5 47 6,2 47 6,2 Totale 760 100 760 100 760 100
- 12. frazione ossigeno pressione parziale ossigeno .205
- 14. autonomia *ARR-SC impostato con OEA 50, flusso 6 l/min Il gas “sprecato” da ARR-SC dipende da: consumo metabolico di ossigeno (p.es. 1 litro/min), frazione di ossigeno nella bombola (p.es. 50%), flusso impostato (p. es. 6 l/min) GAS SPRECATO (%) profondit à (metri) circuito aperto ARR-SC* ARR-C 0 96 9 0 10 98 9 0 20 98,67 9 0 30 99 9 0 40 99,2 9 0 50 99,34 9 0
- 16. tabella U.S. NAVY rev. 1999 ppO 2 = 1,2 atm
- 20. David affetto da DCI durante record di Nuno Gomes, 282 metri con circuito aperto – 14 ore di decompressione (2001) fatalità formazionebuon senso
- 28. simulatore ARR
Notas del editor
- The first breath in will be good old air, 21% oxygen . You will then breathe out about 16% oxygen and 4% carbon dioxide . Your second breath in will therefore be enough to keep you alive - this is how mouth-to-mouth resuscitation works - but your second breath out will dwindle to maybe 12% oxygen and 8% carbon dioxide . CLICK It is easy to see that although our plastic bag will allow us a few breaths the carbon dioxide level quickly rises CLICK and the oxygen level drops until unconsciousness is achieved! CLICK
- CLICK The nitrox mix is chosen such that the mix’s maximum operating depth is the same or greater than the target dive depth in order to avoid oxygen toxicity problems. The rate of gas addition must also be raised since the 1-2 litres per minute needed by the diver is now diluted with nitrogen; for EAN50 for example the gas rate would have to be around 2-4 litres per minute minimum. CLICK With all that extra inert nitrogen being added to the loop and not being consumed, it will also be necessary to vent off the extra every now and again. The nitrox rebreather will therefore give off small amounts of bubbles and is known CLICK as a semi-closed circuit rebreather , or SCR for short. CLICK
- In this sort of rebreather, electronics CLICK measure the actual level of oxygen in the bag, or counter-lung as it is known, CLICK and a controller opens a valve to add in just the right amount of oxygen. CLICK This has the advantage of effectively continuously mixing the optimum blend of nitrox for whatever depth the diver is at. Because only oxygen is added, there is no excess gas to vent and therefore no bubbles at all during the dive. This sort of rebreather is therefore known as a closed circuit rebreather or CCR for short. The disadvantage of the CCR is its complexity and greater initial cost compared with the SCR. As a general rule electronics and seawater are poor bedfellows and making the required controllers waterproof doesn’t come cheap. CLICK
- To begin to answer this we must remember back to Dalton’s Law which describes the relationship between absolute pressure, gas fraction and gas partial pressure . CLICK This relationship is described by this equation . CLICK We can re-arrange this equation to look like this CLICK