[Mikhail]

Очень интересно было бы узнать подробнее теорию поглощению кислорода организмом и потестироваться на это. Для затравки есть достаточно популярная статья про K-фактор Аргуриса вот здесь - http://www.rebreathe...own-factor.html

Ke Definintion:

The ventilatory equivalent for Oxygen (K) is a constant that rpresents the fact that the harder one works (metabolic consumption of oxygen, Vo2), the faster one breathes (respiratory minute volume, VE).


It the ratio of the volume of air ventilating the lungs to the volume of oxygen consumed. It represents the amount of ventilation required for the consumption of each litre of oxygen and reflects ventilatory efficiency. It is measured as the ratio of the volume of gas expired per minute to the volume of oxygen consumed per minute (i.e. VE/VO2). At rest the ventilatory equivalent for oxygen ranges from about 23 to 28 l air l oxygen consumed. It usually remains relatively constant during sub-maximal exercises, but the value may increase above 30 l air l oxygen consumed during maximal exercise.

So, the equation can described as: Ke = VE/VO2

VO2 – Oxygen Consumption
Oxygen consumption is the amount of oxygen taken up and utilized by the body. The oxygen taken into the body at the level of the lungs is ultimately used for the production of ATP in the mitochondria of our cells. Because most of the energy in the body is produced aerobically, VO2 can be used to determine how much energy a subject is expending. VO2 can be reported in absolute terms (L/min) or relative to body mass (ml/kg*min). Oxygen consumption is dependent on the ability of the heart to pump out blood, the ability of the tissues to extract oxygen from the blood, the ability to ventilate and the ability of the alveoli to extract oxygen from the air.
VO2 = HR x SV x A-vO2difference
Where: HR = heart rate in beats per minute
SV = stroke volume (amount of blood pumped out of the heart per beat)
A-vO2difference = the amount of O2 extracted from the blood by the tissues
VO2 = VE x (.2093 – FEO2)
Where: VE = amount of air moved in and out of the lungs/minute
(.2093 – FEO2) = the amount of O2 extracted from the air by the lungs
Resting absolute values tend to be around .2-.5L/min in men and .15-.4L/min in women. The approximate resting relative VO2 for all individuals is 3.5ml/kg*min. Oxygen consumption is most frequently determined using open-circuit spirometry. Open circuit spirometry can be used not only for the determination of oxygen consumption, but also for the determination of metabolic rate (indirect calorimetry).

The typical values for Ke is between 14-28.
In PSCR we use between 20-25. But how we come to this ratio figures?

The typical values for Ke is between 14-28. With 14 for a fit diver (consuming less oxygen) and 28 for an unfit diver (with greater RMV consumption).

Since the operation of a PSCR rebreather is based on the respiratory minute volume (RMV), if you breathe the rebreather provides gas. In that case the higher RMV the higher the Ke resulting in a more stable fiO2 due to more frequent gas addition.


In PSCR we use between 20-25. But how we come to this ratio figures?

In The beginning the original Halcyon system (the fridge) used the physiological ratio between breathing frequency and metabolic usage to establish the necessary flow for semi closed functioning. Linearity exists between the higher gas consumption at labor, increased breathing volume and the metabolic usage.

We that from every breath at the surface, 3.85% is metabolically consumed. The volumetric proportion number is 1:26. So when someone have a Ke of 20 it means that he/she metabolically consume 5% in the surface.


Ke Fi02 drop
14 7,1%
15 6,7%
16 6,3%
17 5,9%
18 5,6%
19 5,3%
20 5,0%
21 4,8%
22 4,5%
23 4,3%
24 4,2%
25 4,0%
26 3,8%
27 3,7%

Because the metabolic usage of a diver is not influenced by increased depth it remains constant. So only the volumetric need directly proportional with depth is changed. This is the principle at which the technique is based on. The old Halcyon and other regulated SCR rebreathers used a variable flow rate, related to the breathing volume.

As soon as the diver exhales in the counter long both the inner and outer counter long are filled. At the inhalation, a part of the loop is dumped. The volumes of the inner and the outer counter lung define the amount of gas injected; their proportion is 1:26. The old Halcyon (PVR-BASC) was a depth compensated system. The new RB80 it is not. So this difference between between depth and non-depth compensated systems created in the past many misconceptions regarding FiO2 drop.

It is there for very crucial for every PSCR user to determine its personal Ke for effective and safe usage of its system. For an average person a Ke figure of 20 is applied but still there are exceptions due to equipment, fitness, etc, as later studies revealed.

I hope this info will help all the friends that send me a personal email asking me to explain the Ke concept.

Argyris

[Mikhail]

По хорошему получается, что знать свой К-фактор нужно даже не в статике (одна глубина, один режим работы), а в динамике. Так, к примеру, при всплытии он будет больше просто за счет того, что нужно больше вентилировать контур (выдыхать в маску каждые три метра или 4 вдоха), чтобы в контур добавлялся свежий газ. При погружении он наоборот будет падать. Ну и на постоянной глубине он тоже как-то будет отличатся от двух предыдущих величин.

То есть для правильного расчета нужно делать измерение своего потребления кислорода:
- на поверхности
- при погружении
- при всплытии
- на средней глубине (как минимум на трех разных глубинах).

Делать это на нескольких погружениях и усреднять.