Lobuche Glacier- the view from the door
This is the big experiment, or at least requires the most hands. We're looking at a number of things but basically we're using ultrasound to measure volumetric flow into our brains (ultrasound measures how fast the red blood cells in you blood move and can give a simultaneous picture of the vessel- from that we can calculate a cross-sectional area, multiplied by the velocity gives us flow), so we have blood flow and oxygen delivery into our brains. This is measured in a number or vessels leading into your brain by 2 people.
The reason it's called an a-v study is that we're also measuring arterial (a) blood gases (PO2,PCO2, remember P means pressure) and metabolites (lactate, hydrogen ions, a multitude of others) as well as the same on the venous (v) side. If we subtract the v from the a we get a value representing what the tissue is using. In this case, the brain. In order to make these measures we have to have an arterial line (this is usually inserted into our radial artery (with ultrasound to help Dave MacLeod, the anesthesiologist from Duke, find the vessel). We can use the radial artery as arterial blood is basically the same no matter where you get it. In order to get the venous side we are doing something much cooler (this is where my mom inserts "dangerous"), but not to worry Dave is as professional as they come. To get these measures, Dave has to insert a cannula (think long needle that stays in) into our jugular vein. To do this he uses ultrasound to differentiate between the jugular vein (good) and carotid artery (hitting that would be bad). It's actually a pretty easy procedure for the subject (I won't speak for Dave), but it's the most invasive study I've ever been involved in. During the experiments one person draws out arterial blood, while the other draws venous blood (at specific time points, and never very much at a time) and are then run by Dave's son Nick (what a great experience for a 17 year old) down to another room that has a blood gas analyzer. All-in-all, 84 samples are drawn over the experiment.
Nima helping Dave get prepped to insert the jugular line
Joe with the jugular line in his neck
We then get a transcranial Doppler ultrasound (this one sends ultrasound into our brains- it can only measure velocity, no cross-sectional area, so no flow) hooked up to our heads, continuous (beat-to-beat) blood pressure and we have our oxygen and carbon dioxide measured breath-by-breath.
Me hooked up to the TCD
That was just the set-up! The experiments involve different ventilatory stimuli: we add CO2 as a stimulus to breathe more, we add higher levels of oxygen to simulate being back at sea-level and we exercise to max! It's a crazy study and takes about 4 hrs to complete. However, it's extremely novel and will hopefully produce some ground breaking data related to brain metabolism under different ventilatory drives and brain metabolism during exercise, all whilst at high altitude (we've also got the sea-level data).
This study took up a bunch of long days, but is complete, except for one more subject who is on his way up from Kathmandu over the next few days. We have since turned our focus back to sleep studies and exercise echoes. Tomorrow we start up with Nia's study again, which will keep us busy for a few days.
After having the line inserted. We keep it in for a while, so here, I'm outside going from the lab to the rooms.
I still haven't found my health (but am still in the middle of the group when it comes to that). Others have upper respiratory track infections, some have had severe AMS symptoms (Phil needed a shot of dexamethosone in the bum last night to help settle his headache- he only jumped a little, and a few others have had it too). One of the group Ren had stomach pain for a few days. Keith, one of the physicians, thought it looked too much like appendicitis, so he and the Pyramid staff arranged for her to be helicoptered down to Kathmandu for further evaluation. Turned out he was right and through some contacts was able to arrange surgery for her. So, we've lost Ren, Chris (went with her) and Gord has headed back to Canada as well. We lose Jim tomorrow, but things are still moving along. There are about 10 more days of work at the Pyramid and then we all head out too.
It's been amazing, but reaching that point where we al want to hug and kiss our families, sleep in our own beds, shower regularly and in my case, go to the beach! My oldest got new swim goggles and I'm sure she's itching to try them out. My youngest told me today that she wished she could have me for real... Straight to the heart! Gotta thank my wife and Ady for holding down the fort.