Baseline cerebral oximetry has normal values range from 60% to 80%, some values of 55–60% in some cardiac patients
CO2 affects Cerebral oximetry by decreasing CO2, which leads to cerebral vasoconstriction that causes a decrease in blood flow to the brain ultimately causing brain oxygenation to drop
How O2 affect Cerebral oximetry:
An INCREASE in O2 leads to cerebral vasodilation that causes an increase in blood flow to the brain ultimately causing brain oxygenation to increase
If you’re doing and IPV treatment, cerebral vasoconstriction leading to decreased blood flow due to blowing off too much CO2 can cause brain NIRS to drop
T-COM
General
What it does:
Measures the skin-surface partial pressure of carbon dioxide (PtcCO2) and partial pressure of oxygen (PtcO2) to provide an estimate of the partial pressure of arterial carbon dioxide (PaCO2) and oxygen (PaO2)
Use one when a patient being ventilated by High Frequency ventilation and VDR in the Pediatric Intensive Care Unit
Change site Q4, but if sensitive skin or redness is noticed start changing Q2
Hazards/complications:
False-negative and false-positive results may lead to inappropriate treatment of the patient
Injury may occur at the measuring site
Erythema
Blisters
Burns
Skin tears
Factorsthat may increase the discrepancy between arterial and transcutaneous values:
The presence of hyperoxemia
PaO2 greater than 100 mmHg
The presence of a hypoperfused state
Shock
Acidosis
Improper electrode placement or application
Vasoactive drugs
The nature of the patient's skin and subcutaneous tissue
Skinfold thickness
Edema
Sensor site selection:
A place with good capillary blood flow where the airtight seal between the sensor and the skin can be maintained
Avoid areas with large amounts of fatty deposits or bony prominence that may constrict the blood flow beneath the surface of the sensor
ETCO2
General
What it is:
A noninvasive technique which measures the partial pressure or maximal concentration of carbon dioxide at the end of an exhaled breath
Normal values are 35-45 mmhg
The normal shape of a capnography waveform is rectangular, like a pressure waveform
V/Q mismatch affects:
Related changes in the patient’s condition will be reflected in a widening or narrowing of the etco2 and pCO2 gradient, conveying the V/Q imbalance and therefore the pathophysiological state of the lungs
With healthy lungs and normal airway conditions, end-tidal CO2 provides a reasonable estimate of arterial CO2 (within 2-5 mmHg)
With diseased/injured lungs, there is an increased arterial to end-tidal CO2 gradient due to ventilation-perfusion mismatch
Dead-space ventilation results in ventilated alveoli with insufficient perfusion that leads to low etCo2. Things that can cause this to happen: