Frequently Asked Questions About Carbon Monoxide Poisoning and ClearMate™ Treatment
How is CO removed from the body?
Carbon monoxide (CO) is more attracted to hemoglobin than oxygen (O2). Only small concentrations of CO are required to result in many attachment sites on hemoglobin being replaced by CO. When exposure to CO is stopped, CO is slowly replaced by O2 from air, which is 21% O2. 4. By increasing O2 concentration by 5 times to 100% O2, the rate of replacement of CO by O2 increases by 5 times that of room air.
What is the mechanism for hyperbaric chamber treatment of CO poisoning?
By increasing the pressure of O2 by 3 times, as occurs in hyperbaric chamber, there are 3 times more O2 molecules in the same volume present and the rate of replacement of CO will increase again by 3 times. This means that in the hyperbaric chamber the replacement of CO is 3 times as fast as just giving 100% O2. Since giving 100% O2 replaces CO 5 times as fast as room air, the hyperbaric chamber results in CO elimination that is 3 x 5 = 15 times as fast as room air.
What is the mechanism for ClearMate™ treatment of CO poisoning?
As the blood passes by the lung, CO diffuses into the lung. Breathing 100% O2 causes the CO to diffuse into the lung 5 times as fast as breathing room air (21% O2). Increasing the breathing rate by 3 times resting breathing, the lungs, and therefore the blood, are cleared of CO 3 times as fast. This increased rate of elimination is on top of the 5 times increase in the rate of CO elimination from breathing pure O2. As such, increasing ventilation by 3 times with ClearMate™ results in the elimination of CO by 3 x 5 = 15 times that on room air – same as the hyperbaric chamber.
Does this work even at high blood concentrations of CO?
The rates of elimination of CO were studied in dogs (Fisher et al., 1999) which were poisoned to 70% carboxyhemoglobin, which is near the fatal level for dogs and humans. The animals were treated in the hyperbaric chamber as well as with ClearMate™ . The rates of elimination of CO were the same with ClearMate™ as with hyperbaric O2.
Does this work in humans?
Humans were exposed to CO and then the rates of elimination of CO were examined while breathing O2 at different rates of ventilation (extents of breathing). (Takeuchi et al., 2000). The rates of elimination of CO were found to increase with increased ventilation. The optimal rate of elimination occurred at about 3 times resting breathing. This is about the breathing rate of healthy people after walking up one or two fights of stairs. So, yes, it works in humans.
So, should we just ask humans to hyperventilate?
It is a common experience that people cannot hyperventilate for long as they become light headed and uncomfortable. This is because hyperventilation also eliminates carbon dioxide from the blood. Hyperventilation and loss of carbon dioxide is bad for the patient.
How do we arrange to eliminate CO and not carbon dioxide? Are there carbon dioxide sensors, flow sensors and feed-back loops?
We have designed ClearMate™ to replace the carbon dioxide in exact proportion that it is being lost so the carbon dioxide level in the blood stays the same regardless of how hard the patient breathes. There are no carbon dioxide sensors or flow meters or any other electronics.
ClearMate™ is a simple mechanical device that contains some standard valves that passively and automatically replaces exactly the amount of carbon dioxide that is lost, regardless of the extent and pattern of breathing. Because the carbon dioxide replacement is locked in mechanically, the system is perfect and cannot be fooled.
How do you get the patients to hyperventilate? What if they won’t cooperate?
Patients who are breathing spontaneously on the ClearMate™ circuit will automatically hyperventilate by the following mechanism:
They get 100% O2. Contrary to what most people think, O2 is a respiratory stimulant, NOT a respiratory depressant. Those who need some convincing may review the following references: (Rucker et al., 2002; Iscoe & Fisher, 2005; Becker et al., 1995; Becker et al., 1996). The ClearMate™ can be used to control the carbon dioxide in the blood. The user can use the ClearMate™ to slightly increase the carbon dioxide level which also stimulates ventilation.
If there is a hyperbaric chamber available, do I still need a ClearMate™?
The efficacy of treatment of CO poisoning depends very much on the time to treatment, especially for pregnant patients. The hyperbaric chamber typically takes at least 2 hours to prepare. ClearMate™ is portable and treatment can be started right at the time of rescue and continued in the ambulance or begun in emergency rooms (approved use in USA). Even if it takes only 20 minutes to pick up the patient and arrive at the hospital, in that 20 minutes the CO level would fall to half. In an hour, the CO levels may be too low to detect. This is an advantage in places that don’t have hyperbaric chambers. Treatment with ClearMate™ does not prevent or delay treatment with a hyperbaric chamber, if one is available.
What advantages are there to using the ClearMate™? Why isn’t giving them 100% O2 good enough?
As discussed, 100% O2 increases the CO elimination by 5 times. With ClearMate™, this increase in elimination goes to 15 times. One would think that giving people 100% O2 must provide more O2 to the brain than just giving them air. However, when this is tested, it has been shown that administering O2 actually reduces the brain blood flow, and the net effect is less O2 delivered to the brain. (Rucker et al., 2002). If the O2 is administered with ClearMate™, the carbon dioxide levels are maintained and the O2 delivery to the brain is maintained. (Rucker & Fisher, 2006)
If this is true, the ClearMate™ should be able to increase the elimination from the blood of any volatile substance. Has this been tested?
Yes. Anesthetics are volatile hydrocarbons. With ClearMate™ , anesthetics are quickly cleared and patients wake up quickly. (Katznelson et al., 2008; Katznelson et al., 2010; Katznelson et al., 2011)
Is the ClearMate™ as safe as hyperbaric oxygen?
Safer. There is no foreseeable harm to increased ventilation at normal carbon dioxide in almost anyone – certainly when compared to risk of continued exposure of tissues to CO. Complications from hyperbaric chambers can include ruptured ear drums, trauma to sinuses, seizures, strokes from decompression, and others.
What is the cost comparison?
Hyperbaric chambers require large capital outlay for the equipment and infrastructure, and have large maintenance requirements. ClearMate™ costs an order of magnitude less to purchase and requires no infrastructure to maintain. Its consumables are few and inexpensive.
If it’s so simple, effective and inexpensive, why has it taken so long to become available?
The historical reason for this is given in a recent publication (Fisher et al., 2011). The abstract from this publication is reproduced below:
“At the start of the 20th century, CO poisoning was treated by administering a combination of CO2 and O2 (carbogen) to stimulate ventilation. This treatment was reported to be highly effective, even reversing the deep coma of severe CO poisoning before patients arrived at the hospital. The efficacy of carbogen in treating CO poisoning was initially attributed to the absorption of CO2; however, it was eventually realized that the increase in pulmonary ventilation was the predominant factor accelerating clearance of CO from the blood. The inhaled CO2 in the carbogen stimulated ventilation but prevented hypocapnia and the resulting reductions in cerebral blood flow. By then, however, carbogen treatment for CO poisoning had been abandoned in favour of hyperbaric O2. Now, a half-century later, there is accumulating evidence that hyperbaric O2 is not efficacious, most probably because of delays in initiating treatment. We now also know that increases in pulmonary ventilation with O2-enriched gas can clear CO from the blood as fast, or very nearly as fast, as hyperbaric O2. Compared with hyperbaric O2, the technology for accelerating pulmonary clearance of CO with hyperoxic gas is not only portable and inexpensive, but also may be far more effective because treatment can be initiated sooner. In addition, the technology can be distributed more widely, especially in developing countries where the prevalence of CO poisoning is highest. Finally, early pulmonary CO clearance does not delay or preclude any other treatment, including subsequent treatment with hyperbaric O2.”
What scientific references can I read?
BECKER, H., POLO, O., MCNAMARA, S.G., BERTHON-JONES, M., & SULLIVAN, C.E. (1995). Ventilatory response to isocapnic hyperoxia. J Appl Physiol 78, 696-701.
BECKER, H.F., POLO, O., MCNAMARA, S.G., BERTHON-JONES, M., & SULLIVAN, C.E. (1996). Effect of different levels of hyperoxia on breathing in healthy subjects. J Appl Physiol 81, 1683-1690.
FISHER, J.A., ISCOE, S., FEDORKO, L., & DUFFIN, J. (2011). Rapid elimination of CO through the lungs: coming full circle 100 years on. Exp Physiol.
FISHER, J.A., SOMMER, L.Z., RUCKER, J., VESELY, A., LAVINE, A., GREENWALD, Y., VOLGYESI, G., FEDORKO, L., & ISCOE, S. (1999). Isocapnic Hyperpnea accelerates carbon monoxide elimination. Am J Respir Crit Care Med 159, 1289-1292.
ISCOE, S. & FISHER, J.A. (2005). Hyperoxia-induced hypocapnia: an underappreciated risk. Chest 128, 430-433.
KATZNELSON, R., MINKOVICH, L., FRIEDMAN, Z., FEDORKO, L., BEATTIE, W.S., & FISHER, J.A. (2008). Accelerated recovery from sevoflurane anesthesia with isocapnic hyperpnoea. Anesth Analg 106, 486-91, table.
KATZNELSON, R., NAUGHTON, F., FRIEDMAN, Z., LEI, D., DUFFIN, J., FEDORKO, L., WASOWICZ, M., VAN, R.A., MURPHY, J., & FISHER, J.A. (2011). Increased lung clearance of isoflurane shortens emergence in obesity: a prospective randomized-controlled trial. Acta Anaesthesiol Scand 55, 995-1001.
KATZNELSON, R., VAN, R.A., FRIEDMAN, Z., WASOWICZ, M., DJAIANI, G.N., FEDORKO, L., MINKOVICH, L., & FISHER, J.A. (2010). Isocapnic hyperpnoea shortens postanesthetic care unit stay after isoflurane anesthesia. Anesth Analg 111, 403408.
RUCKER, J. & FISHER, J.A. (2006). Carbon Monoxide Poisoning. In Clinical Critical Care Medicine eds. ALBERT, R.K., SLUTSKY, A.S., RANIERI, M., TAKALA, J., & TORRES, A., pp. 679-683. Mosby, Philadelphia, PA, USA.
RUCKER, J., TESLER, J., FEDORKO, L., TAKEUCHI, A., MASCIA, L., VESELY, A., KOBROSSI, S., SLUTSKY, A.S., VOLGYESI, G., ISCOE, S., & FISHER, J.A. (2002). Normocapnia improves cerebral oxygen delivery during conventional oxygen therapy in carbon monoxide-exposed research subjects. Ann Emerg Med 40, 611-618.
TAKEUCHI, A., VESELY, A., RUCKER, J., SOMMER, L.Z., TESLER, J., LAVINE, E., SLUTSKY, A.S., MALECK, W.H., VOLGYESI, G., FEDORKO, L., ISCOE, S., & FISHER, J.A. (2000). A simple “new” method to accelerate clearance of carbon monoxide. Am J Respir Crit Care Med 161, 1816-1819.