The Feasibility and Accuracy of Exhaled CO2 to Measure Cardiac Output in Ventilated Patients Without Tracheal Intubation

The purpose of this study is to test the accuracy of a new noninvasive way to measure how
much blood our heart pumps per minute. This new way measures the heart's pumping activity
from outside the body, instead of breaking the skin and measuring it from the inside.

Subjects will breathe normally through a mask while we record how fast and how much air they
are breathing. We will have them "re-breathe" some of the air they breathed out by adjusting
the ventilator. During this time, we will use the air breathed out to calculate how much
blood per minute the subject's heart is pumping. We will also measure how much blood the
heart is pumping at this time by injecting fluid into the catheter in the neck and then
drawing about 1 teaspoon of blood from the catheters in the neck and arm. We will compare
the calculated and measured values of the amount of blood pumped out of the heart for
accuracy.

After we complete this procedure, we will remove the mask and allow you to rest for
10-30min. Following the rest period, we will repeat the process and collect a second set
of measurements. We will draw a total of 4 teaspoons of blood for the study.

If you cannot comfortably breathe along with the ventilator, we will withdraw you from the
study. If you want to stop taking part in the study at any time, let the study doctor know
that you wish to withdraw. We will take off the mask, and your time in the study will end.
This decision will not affect your regular medical care.