Let's say that I'm on a charter, very far away from shore and EMS, what is the "safe" duration of O2 administration for an injured (ie. DCS) diver? Let's say I have a flow rate of 15lpm using a Non Rebreather Mask and I have 2 jumbo D tanks so enough near-100% O2 for about 1h30 administration.
O2 administration: time vs toxicity?
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The short answer is that the tolerable limit at 1 ATM is 24 hours. You'd be hard pressed to hurt someone with an hour & a half of oxygen on a boat no matter what the circumstances.
Rick
mwilding
Contributor
unless the boat is on the bottom...
Bob3
Contributor
By "non rebreather" do you mean that it isn't a closed loop w/CO2 scrubber can?
A demand mask/reg is considered optimum for O2 administration, so you wouldn't be measuring any flow.
A demand mask/reg is considered optimum for O2 administration, so you wouldn't be measuring any flow.
Rick is right on the money!
In guinea pigs exposed to 100-percent oxygen at ambient air pressure for 48 hours, fluid accumulated in the lungs (pulmonary edema) and the epithelial cells lining the alveolus and pulmonary capillaries were damaged.
Here are some effects In humans breathing 100-percent oxygen at the surface:
--Pulmonary edema (intensive-care patients on breathing machines at 30 hours or more exposure)
--Decreases in the rate of gas exchange across the alveoli (intensive-care patients on breathing machines at 30 hours of exposure)
--Chest pains that were worse during deep breathing (volunteers with 24 hours of exposure)
--Decrease in the total volume of exchangeable air in the lung (vital capacity) by 17 percent (volunteers with 24 hours of exposure)
--Local areas of collapsed alveoli when plugged by mucus, a condition called atelectasis (patients, volunteers). The oxygen entrapped in the plugged alveolus gets absorbed into the blood, no gas is left to keep the plugged alveolus inflated and it collapses. Mucus plugs happen normally but are cleared by coughing. Also, if alveoli become plugged during air breathing, the nitrogen entrapped in the alveoli keeps them inflated.
--blindness caused by inadequate development of the capillaries in the lens and retina of the eye (premature infants). Reducing the oxygen to 40 percent can prevent this blindness.
Astronauts breathe 100 % longer but areat reduced pressures.
In guinea pigs exposed to 100-percent oxygen at ambient air pressure for 48 hours, fluid accumulated in the lungs (pulmonary edema) and the epithelial cells lining the alveolus and pulmonary capillaries were damaged.
Here are some effects In humans breathing 100-percent oxygen at the surface:
--Pulmonary edema (intensive-care patients on breathing machines at 30 hours or more exposure)
--Decreases in the rate of gas exchange across the alveoli (intensive-care patients on breathing machines at 30 hours of exposure)
--Chest pains that were worse during deep breathing (volunteers with 24 hours of exposure)
--Decrease in the total volume of exchangeable air in the lung (vital capacity) by 17 percent (volunteers with 24 hours of exposure)
--Local areas of collapsed alveoli when plugged by mucus, a condition called atelectasis (patients, volunteers). The oxygen entrapped in the plugged alveolus gets absorbed into the blood, no gas is left to keep the plugged alveolus inflated and it collapses. Mucus plugs happen normally but are cleared by coughing. Also, if alveoli become plugged during air breathing, the nitrogen entrapped in the alveoli keeps them inflated.
--blindness caused by inadequate development of the capillaries in the lens and retina of the eye (premature infants). Reducing the oxygen to 40 percent can prevent this blindness.
Astronauts breathe 100 % longer but areat reduced pressures.
One of the key word in most of the studies is 100% oxygen in a ventilator setting. While non rebreather mask suppose to deliver 100% O2, in reality, because of deadspace in the airway, slight leak around the mask etc, you will not achieve 100% oxygen delivery to the alveoli so I am not even sure if 100% non rebreather mask, even with longer duration of administration, will ever get to the same toxic level as ventilator can.
Hello
an interesting topic and one that has been on the minds of me and my team for some time now, This year i have seen three 02 hits whilst in the chamber tending,
quite often due to bad weather we have to stablise and provide 02 by demand for up to 6 to 10 hours prior to treatment and during evacuation, This window in good weather is 1 hr 50 mins, In the cases that had 02 hits in the chamber there had been multi day repetitve dives and they have all been proffesionals with approx 600 dives behind them, all three had massive improvements on 02 at 1 ata almost asymptomatic within the hour then relapsing off 02,
two of the three had also been feeling generally unwell prior to getting dcs (fevers or the like) and shouldnt have been diving in the first place.Could this be what pre disposed them.
One thing id always look out for is the individual character of the person its a sad fact of life that some people will take drugs prescriptive or otherwise and not inform you at the scene,
This will have an effect on the o2 tolerance for the individual and should be considered.
I hope you get some answears on this forum that can be put into use in the field at scene not just medical explinations that sound informative but cannot be put into practice where and when it counts.
One thing is for sure you do not want to refuse o2 to a diver or advise caution against it the legal implications are scary.
Kind regards Gary
Dive medic tech
an interesting topic and one that has been on the minds of me and my team for some time now, This year i have seen three 02 hits whilst in the chamber tending,
quite often due to bad weather we have to stablise and provide 02 by demand for up to 6 to 10 hours prior to treatment and during evacuation, This window in good weather is 1 hr 50 mins, In the cases that had 02 hits in the chamber there had been multi day repetitve dives and they have all been proffesionals with approx 600 dives behind them, all three had massive improvements on 02 at 1 ata almost asymptomatic within the hour then relapsing off 02,
two of the three had also been feeling generally unwell prior to getting dcs (fevers or the like) and shouldnt have been diving in the first place.Could this be what pre disposed them.
One thing id always look out for is the individual character of the person its a sad fact of life that some people will take drugs prescriptive or otherwise and not inform you at the scene,
This will have an effect on the o2 tolerance for the individual and should be considered.
I hope you get some answears on this forum that can be put into use in the field at scene not just medical explinations that sound informative but cannot be put into practice where and when it counts.
One thing is for sure you do not want to refuse o2 to a diver or advise caution against it the legal implications are scary.
Kind regards Gary
Dive medic tech
Yes, ventilator also has dead space but it would be less than that of a mask. I think also because of the ventilator setting such as PEEP and pressure support and being an active O2 delivery unit rather than passive (such as mask), it is much more efficient at delivering more O2 to a person. If you compare blood gas of somebody (with normal lung) on 100% O2 by mask and by ventilator, partial pressure of O2 on a blood gas will be significantly higher in a person on ventilator.
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