what vitals signs can be monitored non-invasively
-HR- electrocardiography( hr and rhythm)
-RR- impedance
-BP- periodic monitoring
define pulse oximetry
continuous noninvasive monitoring of oxygen saturation in the blood
principles of operation
-two light emitting diodes (red and infrared)
-sensor detects pulsatile blood flow
-calculates O2 saturation
what is the application of pulse oximetry
-firm places to avoid motion artifacts
-avoid overtightening
-change routinely
-preductal (right hand) vs postductal saturation (left hand or lower extremities)
what are the limitations of pulse oximetry
-motion artifacts
-ambient light
-nail polish
-low cardiac output
-vasoconstriction
-hypothermia
-dictation of hyperoxia in neonates
-carboxyhemoglobin
define capnography
measurement and representation of exhaled carbon dioxide
principle of operation
-infrared and mass spectrometry
-mainstream (directly in the airway provides real time CO2) vs sidestream (aspirated gas sample through a tube to an external analyzer)
-key value measure is PetCO2
1. endtidal co2: partial pressure of CO2 and end of exhalation
2. displayed in mmHg
define the principle of operation VCO2
- volumetric capnography is the simultaneous measurement of gas flow and CO2 concentrations
-values can be nurmerically or graphically displayed of CO2 elimination
-volumetric carbon dioxide elimination (VCO2) is measures in mililiters per min
define the limitations of capnography
-mainstream adapter are heavy
-water condensation and secretion build up
-added weight of the mainstream sensor can be a concern
-inappropriate sensor selection can have detrimental effect on ventilation
how to interpret capnography
-trending PetCO2 will give bedside clinician a good sense of adequacy of ventilation for the pt
- increase ETCO2=hypoventilation
-decrease ETCO2= hyperventilation
define transcutaneous monitoring (TCOM)
measurement of PtcO2 and PtcCO2
-provides continuous information about bodys ability to deliver oxygen to the tissue and remove CO2
-estimated arterial O2 and CO2
define the principles of operation for transcutaneous monitoring
-heating element to improve gas diffusion : enhance capillary blood flow
-PtcO2 slightly lower than arterial
-PtcCO2 slightly higher than arterial
define the application of transcutaneous monitoring
- most critical aspect is site selection and application
( put sensor in well perfused areas: chest, abdomen, thighs)
-temp range 41C-44C (106-111F)
-change site every 4-12hrs (prevent thermal injury, site breakdown)
-accuracy of sensor is improved by using 1-2 drops of contact gel or normal saline or sterile water
what are the limitations of transcutaneous monitoring
-labor intensive
-take time to obtain measure
-limited use in cardiopulmonary resuscitation,airway obstruction, apnea detection
-change in perfusion
define calorimetry
-measurement of gas exchange and determination of energy expenditure (metabolic needs)
-principle of operation
1. oxygen consumption (VO2)
2.carbon dioxide production (VCO2)
3.calculate resting energy expenditure
4. direct calorimetry ( measuring total amount of heat produced and lost from body)
5. indirect calorimetry (more common, combines measurement of VO2 and VCO2 into an equation to calculate energy expenditure, used at bedside mechancially ventilated pt)
what are the limitations of calorimetry
-direct calorimetry are bulky,expensive,and not suitable for critically ill infants and children
-indirect: time consuming and required well trained personnel
define near infrared spectroscopy (NIRS)
principle of operation
-noninvasive: assessing O2 supply and consumption in tissue
-evaluate cerebral oxygenationand perfusion
-used to estimate blood flow
-NIRS assess ratio of oxyhemoglobin (HbO2) and total hemoglobin (Hbtot)
what is chromosphore
-portion of hemoglobin molecule that absorbs NIR light, changes when oxygen is added or removed
-estimate oxygenation of tissue
define the application of NIRS
- estimating regional oxygen saturation in the brain bRSO2(most common indication)
-bRSO2 decreased=ischemic injury increases
-average cerebral bRSO2< 65% may be global hypoperfusion indicator caused by low cardiac output
what are the limitations of NIRS
-accuracy largely dependent on probe placement
-lack of large trails identifying typical SO2 values for tissue in various pt cohorts
