Standard Pulse-ox Study
The first step of the study is placing a small (22 G) catheter in the artery of one wrist*. This is done using local anesthesia to minimize the discomfort. Subject’s will then have pulse oximeters attached to fingers, sometimes ear lobes, occasionally toes. These are attached as a small clip or bandaid that goes over the nailbed. These instruments shine a light through the finger. Attachment and removal involves no discomfort. Subject will have a nose clip placed on either side of the nostrils, so that he/she is forced to breathe through the mouth. Subject will then breathe a special gas mixture through a mouthpiece. The mouthpiece is similar to what is used on a snorkel.
Subjects will be asked to breathe regularly, but more deeply and somewhat faster than normal as the gas mixture is adjusted to lower levels of oxygen. Blood samples are removed from the catheter in the artery at various time points. This does not involved further invasive procedures. Each “run” involves 8-10 samples, takes about 15 minutes, and finishes when the subject breathes oxygen. A complete study consist of 2-3 “runs” depending on the number of samples. The catheter in the wrist is removed at the end of the study, and pressure is held on the puncture site for 10 minutes. Subjects are then free to leave. Normal activities are fine, but vigorous activity of the arm where the catheter was placed should be avoided for several hours.
*Some study sponsors may conduct this study without requiring blood sampling. You will be informed prior to your participation whether this is the case.
Pulse-Ox Study Consent
It is necessary to sign a consent for the study. You can download the Standard Pulse Ox Consent Form ahead of time, which should be read in advance so that we can take time to answer any questions.
This study is different from our standard pulse-ox studies in that we’re testing devices that detect methemoglobin (Met-Hb). This study would require around 2.5 to 3 hours of your time, and it pays $200. Similar to the pulse oximeter study, a 22 gauge arterial catheter is placed using local anesthesia to minimize discomfort. An iv catheter (20 or 22 gauge) is also placed for this study, using local anesthesia. To induce the formation of met-Hb in our study, a slow infusion of sodium nitrate is given via an intravenous line. Sodium nitrite oxidizes normal hemoglobin present in red blood cells into a useless form of hemoglobin called methemoglobin. The nitrite infusion will slowly increase met-Hb in the blood from a normal level of .1%-1% to about 13%-15%. This process will take anywhere from 1.5 to 2 hours. We stop our infusion when blood levels reach 9%, after which the remaining nitrite brings the final level to the 12%-14% mark. Levels of methemoglobin in excess of 20% may cause fatigue, headache, exercise intolerance, dizziness, and mental status changes, but these symptoms are very rarely observed in healthy, normal individuals at levels less than 20%. Blood samples will be periodically drawn from an arterial line and analyzed in a co-oximeter, much like our usual pulse-ox studies. Upon initial infusion of the nitrite, your body already begins to metabolize methemoglobin back to normal, useful hemoglobin; however, it may take several hours for methemoglobin to drop to pre-study levels, so strenuous exercise immediately after the study is discouraged for a few hours.
Methemoglobin Study Consent
It is necessary to sign a consent for the study. You can download the Methemoglobin Pulse Ox Study Consent Form ahead of time, which should be read in advance so that we can take time to answer any questions.
Carboxyhemoglobin is a complex formed by the binding of carbon monoxide and hemoglobin. This complex is formed in the human body when carbon monoxide is inhaled, most commonly from tobacco smoke. The formation of this complex can hinder the delivery of oxygen to your tissues.
In our study, you will be given a very small, safe dose of carbon monoxide to inhale which will increase your carboxyhemoglobin levels to around 10%, approximately equivalent to smoking a pack of cigarettes. Throughout the study, we will periodically take 1cc sized blood samples from an arterial catheter which we will analyze in a blood gas analyzer. Those results will be compared with the results of a non-invasive oximeter, helping to determine it’s accuracy. Once we reach 10% carboxyhemoglobin levels, the subject will complete a round of hypoxia, similar to our standard pulse oximeter studies. The subject will breathe a special mixture of gasses which will be adjusted to bring you oxygen saturation levels down to as low as 80%. 1cc sized blood samples will be taken at each level of oxygen desaturation.
After the completion of the study, it will take between 4-6 hours for the carbon monoxide to leave your system so it is recommended that you not participate in any strenuous activity immediately after. Some possible side effects include fatigue, or a feeling of light headedness. We will have pure oxygen on hand to reverse the effects if you feel any of those symptoms.
Carboxyhemoglobin Study Consent
It is necessary to sign a consent for the study. You can download the Carboxyhemoglobin Pulse Ox Study Consent Form ahead of time, which should be read in advance so that we can take time to answer any questions.
Cerebral Oximetry Study
In this study we will be studying the accuracy of cerebral oximeters (devices that detect brain oxygen levels by shining light through the forehead) in the presence of hypoxia. In addition to hypoxia, you could either be exposed to increased levels of methemoglobin or carboxyhemoglobin but never both. It will be specified in the recruitment email whether or not increased methemoglobin or carboxyhemoglobin will be used. The levels of each substance will be equivalent to those reached in the methemoglobin or carboxyhemoglobin studies mentioned above.
For this study, you will have an arterial catheter inserted into one of your wrist arteries under local anesthesia. An intravenous catheter will also be placed in a vein in your hand. Lastly, a small catheter will be inserted into one of your jugular veins in your neck to enable blood samples to be drawn.
You will first be asked to breathe through a mouthpiece with a nose clip on your nose. A special mixture of gasses will be adjusted to bring your blood oxygen saturation down to as low as 80% over a series of plateaus. Two blood samples will be taken from the arterial catheter and two will be taken from the jugular catheter at each plateau. Each sample will be approximately 1cc. The subject will briefly be given %100 oxygen to restore normal oxygen saturation levels at the end of each run of desaturation.
If carboxyhemoglobin or methemoglobin are being used in the study the subject will then either be asked to breathe small amounts of carbon monoxide or receive an intravenous dose of sodium nitrite to induce the formation of carboxyhemoglobin and methemoglobin respectively. This will be done in the same manner described above for the methemoglobin and carboxyhemoglobin studies.
Once the proper levels of carboxyhemoglobin or methemoglobin are obtained a second run of oxygen desaturation, identical to the first, will be performed. A second desaturation run will also take place if carboxyhemoglobinemia and methemoglobinemia are not induced.
After the completion of the study, it will take several hours for the carbon monoxide or methemoglobin to leave your system so it is recommended that you not participate in any strenuous activity immediately after. Some possible side effects include fatigue, nausea, or a feeling of light- headedness.
Cerebral Oximetry Study Consent
It is necessary to sign a consent for the study. You can download the Cerebral Oximetry Study Consent Form ahead of time, which should be read in advance so that we can take time to answer any questions.
Cerebral Oximetry with CT
In this study we will be studying the accuracy of cerebral oximeters (devices that detect brain oxygen levels by shining light through the forehead) in the presence of hypoxia. In addition to hypoxia you could either be exposed to increased or decreased levels of carbon dioxide (CO2). You will be placed into one of the two groups at random. For this study, you will have an arterial catheter inserted into one of your wrist arteries under local anesthesia. Also an intravenous catheter will be placed in a vein in your hand. Lastly, a small catheter will be inserted into one of your jugular veins in your neck to enable blood samples to be drawn.
The study is broken up into two phases. In the first phase, you will be asked to breathe through a mouthpiece with a nose clip on your nose. A special mixture of gasses will be adjusted to bring your blood oxygen saturation down to as low as 70% over a series of stepwise plateaus. Two blood samples will be taken from the arterial catheter and two will be taken from the jugular catheter at each plateau. Each sample will be approximately 1cc. The subject will briefly be given %100 oxygen to restore normal oxygen saturation levels at the end of each desaturation run.
In the second phase, you will repeat the round of breathing much like the first phase, however, the gasses will be modified to either elevated or decreased levels of carbon dioxide (CO2.) The carbon dioxide will be adjusted based on the subject’s tolerance. Blood samples will be taken, similarly to phase 1, at every stable level of oxygen saturation from both the radial artery catheter as well as from the jugular vein catheter.
One of the goals of this study is to understand why cerebral oximeters do no read accurately in certain individuals. Depending on the readings obtained during your test, you may be asked to have a head CT scan to examine such factors as the thickness of your skull bones and the anatomy of your sinuses. You will be able to do the CT scan at your soonest convenience. You will be compensated an additional $50 if you are asked to do so and complete the CT scan.
Cerebral Oximetry With CT Study Consent
It is necessary to sign a consent for the study. You can download a pdf of the consent ahead of time, which should be read in advance so that we can take time to answer any questions.
The purpose of this study is to determine if new medical devices can detect the level of hemoglobin (the red pigment in the blood that carries oxygen) in the human body. The devices shine light through the skin, similar to a pulse oximeter, or measure the electrical properties of tissues, such as a calf muscle.
On the day of the experiment, you will spend between 2.5 and 8 hours doing the test procedures (the time required depends on the number of units of blood removed and re-infused). 1 to 4 pints of blood are withdrawn and are replaced with other fluid. This blood donation procedure is called hemodilution, which is defined as the replacement of blood with an equal amount of fluid. The blood that has been removed will be returned after processing to remove excess fluid. One pint of the blood that was removed may not be returned to you.
Pulse oximeters and hemoglobin measurement devices will be attached to your fingers, forehead and or calf. Electrocardiogram pads will be placed on the skin of your chest.
You will have catheters (small plastic tubes) placed in vein(s) in one or both arms and an artery of one of your wrists. Before inserting the catheter into your wrist artery, we will check blood flow in your hand by occluding the wrist artery by finger pressure while you make a fist. One to 4 pints of blood (the amount will depend on your weight and starting hemoglobin concentration) will be withdrawn while 5% Human Albumin, a solution of a common blood plasma protein, will be returned through a vein to keep the total amount of fluid in your body at a normal level. All but one of the units of blood that is withdrawn will be processed by the UCSF Blood Bank so that your red blood cells from those units can be returned. The plasma will not be returned to you during the transfusion.
Up to 30 small blood samples will be taken during the study to measure oxygen carbon dioxide, calcium, and other tests (the blood will be taken from the catheter placed in my artery). The total amount of blood taken for these tests is about 2 ounces.
You may be asked to breathe, via a mouthpiece, an air mixture containing reduced amounts of oxygen, as would occur at high altitude. This will be done for just a few minutes.
The physician will be immediately available for emergencies. The subject will be allowed to return home accompanied by a friend or family member. Subjects will be called 48-72 hrs after the study and if they have any symptoms or concerns they will speak with a study MD who may request they return to UCSF to see them if any additional treatment is needed.
Study volunteers may choose to stop the study at any point.
Additional Exclusion Criteria
History of migraine headaches.
Anyone weighing over 80kg (176 lbs)
Any medical condition that the study doctors think will put our study subject’s safety at risk.
Hemodilution Study Consent
It is necessary to sign a consent for the study. You can download the Hemodilution Study Consent Form ahead of time, which should be read in advance so that we can take time to answer any questions.
High Altitude Research Studies at White Mountain
Our lab also has an interest in studying high altitude physiology, adaptations and altitude mountain sickness. We have a history of conducting various research protocols at Barcroft Station, located in the White Mountains near Bishop, CA. Our trips are scheduled intermittently, based on research interests and investigator availability, however, we generally try to go once a year in the summer or fall months. Studies generally consist of physiological measurements, blood draws, and pulse oximetry at altitude over the course of approximately four days. If you are interested in being a volunteer, please join the Pulse-Ox Volunteer Network list-serve, and keep an eye out for our trip announcements. You may also contact our study coordinator for more information.