Hmmm… I was wondering what kind of reaction the reliability statement would fetch…
Before I respond to some of the comments, let me start by saying I’ve spent the majority of 24 years Naval service flying fighter aircraft on and off aircraft carriers for over 3000 hours flight time. All of that flight time was spent breathing 100% oxygen from takeoff to touch down on every flight with most missions over 2 hours in duration. During that time, I also attended annual training in aviation physiology and oxygen breathing systems.
I’m still here at 65 breathing 100% oxygen for my cluster headaches at flow rates that support hyperventilation. I've done this for the last 4 years and I still pass my annual physicals…
I’ve also spent the last three years studying respiratory physiology texts and hundreds of studies involving hyperoxia, respiratory alkalosis, and pH as they relate to cluster headache abortive mechanisms and the pathophysiology of the cluster headache.
What I’ve learned so far is there’s so much more I don’t know about this topic. Accordingly, I’ll be the first to tell you I don’t have all the answers. I do know that the practice of treating the acute cluster headache by hyperventilating with 100% oxygen is gaining support with cluster headache sufferers and a growing number of neurologists experienced in treating our disorder.
Now for some answers to comments on my original post… This post covers a lot about oxygen therapy and gets a bit long so get comfortable...
Absolutes??? Hardly...
After more than 14 years with cluster headaches and the last four as a chronic, I know better than that.
Bob, at your age I thought you'd at least remember the ‘60s era Western Airlines TV ad that had a bird sitting on top of a Boeing 707 resting against the tail saying, "Western Airlines… The only way to fly."
I guess this comes from me being old as dirt and using colloquialisms from days long past...
Most of the youngsters today probably never experienced having more folks on a telephone "party line" than "Carter's Little Liver Pills" where you had to count the number of rings to know if the call was for you... or treating a headache with Speedy's little Alkaseltzer song, "Plop Plop Fizz Fizz, Oh what a relief it is..."
Today it's likely the pothole saying to the car, "Your tire's all flat and junk... Did I do that?"
For the rest of you... If you've caught my drift... There are a lot of ways to fly... (different flow rates to abort your CH attacks)... IMHO and based on the results from the informal pilot study, if you want the most effective flow rates that give you the greatest efficacy and aborts in the shortest amount of time... ask for a regulator that's capable of at least 25 liters/minute and higher or spend the extra money and buy a demand valve... both support hyperventilation.
Ultimately, the best and most compelling information on effective oxygen flow rates comes from those cluster headache sufferers experienced in the use of this method of oxygen therapy who post here on CH.com. They report that when used correctly and early, the efficacy, in terms of success rate is very high and they abort their cluster headache attacks in much less time than the 7 minute figure I use…
As I indicated in the earlier post, “we’re all wired differently” with respect to the efficacy of medications for our disorder… I think I’m fairly safe with that statement…
I also felt safe in saying there are some who can achieve aborts at oxygen flow rates below 25 liters/minute. A flow rate of 15 liters/minute is reasonable for some folks in this category and I’m sure there are others who can achieve aborts at even lower flow rates, but I’ll caveat that by saying “only for attacks at the lower pain levels.”
Too many of us have unfortunately discovered that aborts with these lower flow rates were not possible at the higher pain levels ≥ Kip-7, or the time it took to achieve the abort was painfully long, > 25 minutes or much longer.
My question was why? I also wanted answers to questions, “Why are flow rates that support hyperventilation more effective?” and “Why are some folks are able to abort their attacks effectively at lower flow rates than 25 or 15 liters/minute?”
So let’s talk about hyperventilation for some possible answers… In simple terms, hyperventilation means ventilating the lungs with more air or 100% oxygen than normal…
That begs the questions, “What’s Normal?” and “How Much More?” The answer to the first question is… “That depends.” It basically depends on your weight and the level of physical activity (metabolic rate)…
The second question, “How Much More?” can best be answered by saying as little as 10% to as much as a 100% more lung ventilation than normal depending metabolic rates and how fast you want to abort the pain of your cluster headache attack.
If we’re in a vegetative state, flaked out on the sofa watching TV or asleep, respiratory physiologists will tell us the human body needs roughly 7.5 cc of air per kilogram of weight per minute. If you’re in my shape, (round is a perfectly good geometrical shape), and weigh in at 200 lbs (90 kg), that works out to a respiration minute-volume of lung ventilation equal to 6.75 minute liters inhaled every minute just to supply our bodies with the needed oxygen to sustain life and remove the CO2 produced at that level of metabolism.
If you weigh 150 lbs (68 kg) you need a respiration minute-volume of 5.1 liters
If you weigh 120 lbs (54.5 kg) you need a respiration minute-volume of 4.1 liters
If you weigh more than, less than, or in between these weights… interpolate.
That means under the above conditions and weight we need a minute-volume of lung ventilation somewhere between 5 and 14 liters minutes in order to hyperventilate during oxygen therapy, (an oxygen flow rate of 5 to 14 liters/minute…) and that’s if we’re in a vegetative state, asleep, or sitting motionless... So there’s one possible set of answers why lower oxygen flow rates can be effective in aborting cluster headaches for some folks.
How many of you are able to sit motionless while trying to abort a cluster headache attack with oxygen therapy?
Now here’s the eye-opener… The folks at the S.E.A. Group, an organization that determines breathing requirements for self contained breathing systems used by first responders like fire fighters and rescue workers wearing chemical, biological, and nuclear protection have come up with some answers. They published a report titled “Peak Inhalation Air Flow & Minute Volume during a Controlled Test Performed on an Ergometer.” (An ergometer is a device like a bicycle or rowing machine that’s equipped with instruments to accurately measure the work performed.)
S.E.A. researchers used their Subject Test Laboratories to measured respiration parameters with an instrumented full face mask respirator and at the same time, the work rate in Watts measured with a ergometer. Both devices were connected to a computer to capture the data. Ten test subjects (8 male and 2 female) participated in the study. They had an average age of 34 (min 17, max 59) and weight of 77 kg (min 61, max 96). Each test subject performed the same test sequence of increasing work loads and repeated this sequence 63 times.
The researchers found a work rate of 50 Watts required an average of 22.2 minute liters of lung ventilation. Again, that’s the volume of lung ventilation inhaled every minute just to supply the body with oxygen to sustain life and remove the CO2 produced at that level of metabolism.…
I can hear the wheels turning… “What is a work rate of 50 Watts?” Here’s the answer:
Sitting at ease: Writing, typing on your computer, drawing, sewing, or playing cards.
Standing: Fixing dinner, working with small objects at a workbench.
Walking slowly: Speed up to 3.5 km/h (2.2 mph – 3.2 ft/sec).
In simple terms, 50 Watts is about the same work rate most of us develop during an average cluster headache attack that has us agitated and moving around.
So… If you’re doing any of the above activities… or having a typical cluster headache attack and that requires a minute volume is 22.2 minute liters under normal conditions, you’ll need a minute volume of 24.4 up to 44.4 minute liters of lung ventilation to hyperventilate… and that works out to an oxygen flow rate of 25 to 45 liters/minute.
If you're working hard, like chopping wood with an axe; shoveling or digging; climbing stairs, ramp or ladder; walking quickly with small steps, running, or walking rapidly at a speed greater than 7 km/h or 4.4 mph (6.5 ft/sec), you're at a work rate 150 Watts and that requires a minute volume of lung ventilation over 50 minute liters.
Again, that’s the volume of lung ventilation inhaled every minute just to supply the body with oxygen to sustain life and remove the CO2 produced at that level of metabolism.…
The data we collected in our pilot study shows a clear linear relationship between abort times and pain levels for oxygen flow rates below 25 liters/minute and above… The higher the pain level during oxygen therapy, the longer the abort times. This was consistent for all flow rates.
What literally jumped out of the pilot study data, was a marked difference in abort times between oxygen flow rates below and above 25 liters/minute at the same pain level… For example at a peak pain level of Kip-7 during the oxygen therapy, the average abort time using flow rates that support hyperventilation was 8 minutes while the average abort time was nearly 4 times longer at 31 minutes for the same pain level when using a flow rate of 15 liters/minute.
This difference in abort times was consistent at all pain levels logged between Kip-3 and Kip-9. In short, if the oxygen flow rate is high enough to support hyperventilation and it can be sustained long enough to reach respiratory alkalosis, the abort times will be shorter by nearly a factor of 4.
Bob hit pay dirt with his comment about pH and Michael Crichton’s novel, The Andromeda Strain. Hemoglobin chemistry controls the essential processes that transport of oxygen from the lungs to the body and CO2 from the body to the lungs. It’s also the same process that makes this method of oxygen much more effective and faster in aborting our cluster headaches than the lower flow rates typically prescribed.
When blood pH is high (more alkaline) as it passes through the lungs, hemoglobin has a greater affinity for oxygen so it uploads oxygen. A high pH also causes hemoglobin to offload CO2 although most of the CO2 is carried by the blood serum. When blood reaches the body’s tissues and muscles where the pH is low (more acidic) due to the processes involved with normal metabolism, hemoglobin offloads oxygen. The lower pH also increases hemoglobin’s affinity for CO2 so it uploads CO2.
Respiratory Physiology texts clearly state it’s primarily CO2 levels not a lack of oxygen that actually controls the urge to breathe. When CO2 levels in the blood climb above normal during physical activity, chemoreceptors located in the aorta, carotid arteries, and medulla sense this increase and signal the breathing control center located in the medulla to increase the respiration rate in order to bring the CO2 levels back down to normal.
There are also a number of complex biochemical and hormonal processes controlled by the sympathetic nervous system and the lungs that regulate the vasoactivity of the body’s vascular system. Changes in CO2 and pH levels shift these processes in one direction or the other resulting in vasoconstriction or vasodilation.
If blood CO2 levels are above normal, these processes signal the vascular system to dilate allowing a greater transport of CO2 to the lungs. If blood CO2 levels are below normal, these processes signal the vascular system to constrict. This slows the transport of CO2 to the lungs and allows it to build back up to normal levels.
The majority of the CO2 generated by metabolism dissolves in the blood serum as it passes through the tissues, the rest attaches to hemoglobin. Some of this CO2 disassociates into carbonic acid as shown in the chemical equation below:
CO2 + H2O ⇌ H2CO3 ⇌ HCO3- + H+
The above reaction takes place in the tissues very rapidly in the presence of an enzyme called carbonic anhydrase where CO2 concentrations are the highest. This shifts the chemical reaction to the right. The same reaction takes place in the lungs only the direction of the chemical reaction shifts to the left releasing CO2 through the alveoli as a gas into the exhaled breath. This same reaction is the primary mechanism the body uses to maintain the blood acid-base balance.
Many of us have experience just how effective carbonic anhydrase can be in releasing CO2 from a liquid only we never new why… Have you ever awaken from sleep or worked hard on a hot day then taken a gulp of your favorite carbonated beverage only to have it flash into a mouthful of foam?
It turns out that carbonic anhydrase is present in saliva. During sleep or physical activity where mouth breathing is common, the carbonic anhydrase in our saliva tends to concentrate in the mouth. When it comes in contact with a carbonated beverage, it liberates the dissolved CO2 as a gas.
Higher blood CO2 levels means higher blood acid levels and that results in a lower pH measurement. The body’s vascular system reacts to high CO2 and acid levels by dilating in order to increase blood flow to the lungs allowing CO2 levels to drop back to normal. This also brings the acid - base balance back to a neutral pH of 7.4 (7.35-7.45). This happens whether we’re breathing air or 100% oxygen.
As discussed earlier, a higher than normal blood CO2 level generates more carbonic acid and a lower pH. This results in vasodilation that can make the cluster headache triggering mechanism more effective. We see the results of lower pH levels as an increase in the frequency, intensity, and duration of our cluster headache attacks.
By intentionally hyperventilating long enough on 100% oxygen we pump CO2 from the lungs faster that our body generates it. By continuing to hyperventilate, we pump out enough CO2 to push the bloodstream into respiratory alkalosis.
If we boil it all down, hyperventilating on 100% oxygen enables 4 important processes and their results that combine to abort our cluster headache attacks more effectively and more rapidly:
1. It increases the oxygen content of the blood
(hyperoxia) – A vasoconstrictor
2. It decreases the CO2 content of the blood (hypocapnia)
– A vasoconstrictor
3. Hypocapnia results in respiratory alkalosis that elevates
pH – A vasoconstrictor
4. Elevated pH enables blood hemoglobin to carry more
oxygen – Increased abortive effect
Now here is how we can run into trouble when trying to abort our cluster headache attacks with oxygen at flow rates that don’t support hyperventilation. It only takes an oxygen flow rate of 7 to 9 liters/minute to achieve hyperoxia, the first of the four processes above.
If we use a non-rebreathing mask that limits lung ventilation to the flow rate set on the regulator, and that oxygen flow rate supports a respiration rate that’s less than the body needs to regulate CO2 levels due to the physical activity associated with our cluster headache attack, we have inadequate lung ventilation and are essentially hypoventilating. If this continues, CO2 levels will build until we develop respiratory acidosis.
Now the problem… Even though an oxygen flow rate of 7 to 9 liters/minute may provide adequate oxygenation, the remaining three processes above that worked so well for us when we were hyperventilating are reversed. They start working against us to prevent a successful abort if we don’t have sufficient lung ventilation to remove excess CO2.
2. It increases CO2 content of the blood (hypercapnia)
– A vasodilator
3. Hypercapnia results in respiratory acidosis that lowers
pH – A vasodilator
4. Low pH causes blood hemoglobin to carry less oxygen –
Decreased abortive effect
Symptoms of this condition are easy to spot and many of us have encountered them when trying to abort a painful cluster headache attack at the higher Kip-levels using a disposable non-rebreather oxygen mask and too low an oxygen flow rate. The symptoms are:
• A feeling of restricted respiration (can’t get enough
oxygen or deep enough breath)
• Anxiety
• Panic Attacks
When these symptoms are present, an abort with oxygen therapy can be very difficult if not impossible… Most of us who’ve encountered these symptoms have made one of the following decisions: given up on oxygen therapy completely, kept using oxygen therapy, but frequently resorted to a bailout abortive like imitrex, or dialed up a higher oxygen flow rate.
The following graphic of vasoactivity summarizes the relative impact of oxygen (O2), pH, and CO2 levels with respect to their abortive effects on cluster headache attacks.
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This graphic illustrates the relative influence oxygen, pH, and CO2 levels have on vasoactivity and the effectiveness of oxygen therapy. I’ve reviewed a number of clinical studies that conclude these are essentially independent variables, and that pH and CO2 have a greater effect on vasoactivity than oxygen.
This helps explain how the beneficial effects of hyperoxia can be overridden by higher than normal CO2 levels and a low pH. It also helps explain the pilot study results where cluster headache attacks at higher pain levels took longer to abort. The correlation coefficient between the average abort times for attacks at Kip-levels 3 through 9 is 0.94. This indicates a high level of correlation with a near linear and very predictable relationship between average abort times and Kip-levels.
So far, I’ve covered how this method of oxygen therapy works and why it’s so much more effective in terms of success rate and with much shorter abort times when compared to oxygen therapy at flow rates that don’t support hyperventilation.
As this discussion covered oxygen therapy under “normal” conditions, that begs the question, "What happens when things aren't normal or when there are other conditions that can impact the effectiveness of oxygen therapy?"
I’ll save that discussion for another post… This one is long enough… Hope it helped explain why oxygen therapy at flow rates that support hyperventilation is more effective than the lower flow rates prescribed today… Safe too!!!
Take care,
V/R, Batch
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