Short description of the primary measurements that are calculated and displayed by the CHEETAH NICOM and Starling SV hemodynamic systems
Cardiac Output (CO)
Cardiac Output is the volume of blood being pumped by the heart in one minute. It is equal to the heart rate multiplied by the average stroke volume. The unit of measurement is liters per minute. CO=HR × SV.
Cardiac Index (CI)
Cardiac Index is a parameter that relates the cardiac output (CO) to body surface area (BSA), thus relating heart performance to the size of the individual. The unit of measurement is liters per minute per square meter (l/min/m2).
Heart Rate (HR)
Heart rate is the number of contractions (heart beats) of the heart in one minute. The HR units are BPM (beats per minute).
Ventricular Ejection Time (VET)
Ventricular Ejection Time is the time of ejection of blood from the ventricle, beginning with aortic valve opening and ending with aortic valve closure. The unit of measurement is millisecond..
Instantaneous thoracic Bioreactance. The input and output of blood through the thorax at each systole causes modifications of the electric properties of the thorax, which can be measured by calculating the electrical Bioreactance. The electrical Bioreactance of the thorax cyclically changes with each pulsatile volume of blood ejected from the heart.
Stroke Volume (SV)
Stroke volume is the amount of blood (milliliters) pumped by the ventricle of the heart in one contraction.
Stroke Volume Index (SVI)
Stroke volume index relates the stroke volume (SV) to body surface area (BSA), thus relating heart performance to the size of the individual (SV/BSA). The unit of measurement is milliliter per minute per square meter (cc/min/m2).
Stroke Volume Variation (SVV)
Stroke volume variation is the calculated variation around the stroke volumes which occur at a window of time (for example, during 30 seconds). SVV reflects the patient’s preload responsiveness. SVV is meaningful only in positive-pressure mechanically ventilated patients, during stable periods (for example, no movement or unstable respiration). SVV is not accurate during cardiac arrhythmia. During other periods, SVV may reflect non-respiratory influences on the stroke volume and be less predictive of actual preload responsiveness. The user should take the SVV results in this context and look for appropriate periods in using this parameter. More insight is available in medical publications about SVV and preload responsiveness. Literature on this topic on hemodynamics and cardiac output monitoring may be referenced by the company upon request.
Thoracic Fluid Content (TFC)
Thoracic Fluid Content is the simple inverse of Zo (or 1/Zo). Because it is the inverse of the impedance, it reflects the electrical conductivity of the chest cavity which is also a corollary to the content of fluid in the thorax.
The TFCd parameter indicates the dynamic change in TFC over time. It calculates this by measuring the percentage change between the average of the last 10 TFC measurements and the average of 10 consecutive TFC readings measured at a specific time as set by the operator. For example, if the user chooses to view TFCd in increments of one hour, the average of the last 10 TFC readings is 60 and the average of 10 consecutive TFC readings occurring one hour before is 50, then the TFCd is 20%.
The TFCd0 parameter indicates the change in percentage terms from the average TFC acquired in the first five TFC readings. To illustrate, if average TFC during the first five readings was 40 and the current TFC is 44, this represents a 10% elevation in the TFC relative to the TFC baseline average absolute value. Thus the TFCd0 that will be displayed will be +10%.
Blood Pressure (BP)
Blood Pressure is the pressure exerted by the blood against the walls of the blood vessels.
Mean Arterial Pressure (MAP)
Mean Arterial Pressure is the mean blood pressure. It depends on the flow of blood from the heart (cardiac output) and the resistance to flow in the small arteries and microscopic resistance vessels (arterioles).
Total Peripheral Resistance (TPR)
Total Peripheral Resistance is the resistance to flow that must be overcome in order to push blood through the circulatory system, or the net resistance to blood flow in all the small arteries and microscopic arterioles. TPR= 80 x MAP/CO
Total Peripheral Resistance Index (TPRI)
Total Peripheral Resistance Index is the indexed version of the TPR. TPRI= 80 x MAP/CI
Cardiac Power (CP)
Cardiac Power represents the work product generated by the heart and is measured in units of Watts. It is derived from CO and MAP by the following formula: CP = CO * MAP/451 (see reference for this formula below).
Reference: Mendoza DD, Cooper HA, Panza JA. Cardiac power output predicts mortality across a broad spectrum of patients with acute cardiac disease. American Heart Journal 2007, Volume 153 (3); 366-370
Cardiac Power Index (CPI)
Cardiac Power Index is the indexed version of the CP. It is measured in units of Watts/M2 and is calculated by dividing CP by the BSA. CPI = CP/BSA
Z0 is the electrical impedance of the chest cavity.
DO2I is the oxygen delivery index. It is calculated according to the following formula: DO2I = 1.39 x Hgb x (SpO2/100) x CI x 10.
SpO2 stands for the arterial blood oxygenation.
Hgb stands for the hemoglobin concentration in the blood.
Systolic Blood Pressure (SBP)
Diastoli Blood Pressure (DBP)