Measuring Cardiac Output: A New Respiratory Method David Preiss Institute for Biomaterials and Biomedical Engineering University of Toronto Department of Anesthesia University Health Network November 29, 2004
Dec 18, 2015
Measuring Cardiac Output:
A New Respiratory Method
David PreissInstitute for Biomaterials and Biomedical Engineering
University of TorontoDepartment of AnesthesiaUniversity Health Network
November 29, 2004
Introduction – Cardiac Output
Swan-Ganz Catheter
Non-Invasive: The Fick Equation
CvCO2 CaCO2
VCO2
22 COCO2CO
Ca-Cv
VC.O.
Fick Equation:
Change Ventilation to get CvCO2
Breathing Rate
Final Lung CO2
concentration
Mixed venous arterial
CO2 level
Time
Problem creating change in CO2
Time
Intubated, Ventilated
?
Time
Spontaneous Breathing
Change in CO2 in Awake Patients
• Must be independent of ventilation
• No physical manoeuvre
• Comfortable
Constant O2 flow
Exhaling…
Exhaling…
Exhalation ends
Inhalation starts…
Valve opens
Rebreathing
Rebreathing
Deeper breath
Problem Solved!
CO2 level
Time
Flow
Flow
Problem Solved!
Breathing Rate
Final Lung CO2
concentration
Mixed venous arterial
• Compare with direct measurements
• 3 pilot studies: – Jan, 2003 (32 patients)– June, 2003 (36 patients)– Feb, 2004 (37 patients)
• Patients were conscious and extubated
Evaluating the Method
Comparison with Invasive Methods
0
1
2
3
4
5
6
7
8
10 20 30 40 50 60
Time (min)
C.O
. (L
/min
) Catheter
Non-Invasive
Comparison with Invasive Methods
0
2
4
6
8
10
12
14
0 10 20 30 40 50
Time (min)
C.O
. L/m
in
Catheter
Non-Invasive
Results – 1st and 2nd cohorts
y = 1.0028x + 0.609
R2 = 0.7393
0
2
4
6
8
10
12
14
0 2 4 6 8 10 12 14
Catheter (L/min)
No
n-I
nv
as
ive
(L
/min
)
Results – 3rd cohort
y = 0.8367x + 0.4694
R2 = 0.8637
0
2
4
6
8
10
12
14
0 2 4 6 8 10 12 14
Catheter (L/min)
No
n-I
nva
sive
(L
/min
)
SD = 0.80 L/min
• Periodic breathing• Good seal around mouth required• Requires supply of compressed air• Pain for some patients – deeper breaths
Limitations
Future Work
• Larger range of cardiac outputs• Exercise
• Patients in poorer health• Alveolar deadspace• Shunt
Thanks!
Joseph Fisher MD
Arthur Slutsky MD
Jim Duffin PhD
Al Olszowka MD
Takafumi Azami MD
Cliff Ansel MBA
Ludwik Fedorko MD PhD
George Djaiani MD
Jo Caroll RN
Marat Slessarev
Steve Iscoe PhD
Ron Somogyi MSc
Hiroshi Sasano MD
CVICU Nursing StaffUniversity Health Network