NON INVASIVE MONITORS

Pulse oximetry

• An inexpensive and noninvasive method to measure arterial blood hemoglobin saturations

• Measures SpO2 – Oxygenation in capillary blood

Pulse oximetry

• Indications – Monitor adequacy of arterial

Oxyhemoglobin – Quantify response to therapeutic

procedures– Comply with mandated regulations

• Contraindications – The need for ongoing actual

measurement of Ph, PCO2, PaO2– Abnormal hemoglobin

Pulse oximetry

• Precautions/complications – False readings – Tissue injury

• Assessment of need– Direct measurement not readily available – Continuous and prolonged measurements – When acid-base status not needed

• Assessment of outcome – SpO2 should reflect condition – Documentation of results and intervention

Pulse oximetry

• Frequency – Determined by clinical status of patient

Pulse oximetry • Instrumentation

– Uses photoplesmography • Light detects volume changes in pulsatile

blood flow – Uses red and infrared light – Transmitter – two sided

• LED’s transmit light through tissue

• Intensity of light measured through photodetector on other side

Pulse oximetry

• Output signal is filtered and amplified

• Processed and displayed

Pulse ox

• Components of absorption – Baseline – Pulsatile

Pulse ox

• Accuracy – Falls within ± 3-5% of ABG’s – As SpO2 falls, the accuracy will also fall – Not accurate with saturations below

70%

Pulse ox

• Procedure – Follow manufactures protocol – Never mix components – Sensor must be right size, fit – Confirm good signal, allow time – Set low SpO2 88-92% – Validate baseline with ABG– Clean and disinfect between patients– Inspect probe site frequently – Never act on SpO2 readings alone – Careful with readings

Pulse ox

• Documentation – Date and time – Patients position, location of probe, activity – FiO2 or O2 flow at time of reading – Model of pulse ox – Comparison of SpO2 to ABG– Stability of readings – Patients clinical appearance – Document HR on pulse ox to manual

palpitation of HR

Pulse ox • Factors effecting efficiency

– COHb– MetHb – Fetal Hb– Anemia – Vascular dyes – Billirubin – Dark skin pigmentation – Poor perfusion – Motion artifact – Nail polish – Ambient light

Pulse ox

• ALWAYS TREAT THE PATIENT. NOT THE NUMBER

End Tidal CO2

• Capnometry – The measurement of CO2 in respiratory

gases

• Capnometer – Instrument that measures end tidal CO2

• Capnography – The graphic display of CO2

concentrations versus time – Shows changes with every breath

ETCO2

• Indications – Evaluate CO2 in mechanically ventilated

patients – Monitoring severity of pulmonary disease and

response to treatment – Determine tracheal vs. esophageal intubation – Monitor integrity of vent circuit, artificial airway,

and ventilator – Reflect CO2 elimination – Monitor inhaled CO2 during therapeutic CO2

administration

ETCO2 • Contraindications

– None, remember that your treating the patient, not the number

• Precautions– Misunderstanding the numbers– Weighing down the vent circuit

• Assessment of need – Standard of care in OR

• Assessment of outcome – Results should reflect patients appearance

• Monitoring– Vent params– Hemodynamics

ETCO2

• Instrumentation – Infrared absorption

• Most common

– Raman scattering – Mass spectroscopy – Photoacustic technology

ETCO2

• Sampling ports are either sidestream or mainstream

ETCO2• Mainstream

– In line analyzer chamber placed between the patients airway and the vent circuit

• Advantages – Sensor at airway – Fast response – No sample flow

• Disadvantages – Secretions and humidity block sensor window – Frequent calibration – Bulky and heavy – Non disposable – Intubated patients only

ETCO2

• Sidestream – Sampling tube placed between patient

and circuit, air pumped into measuring chamber

ETCO2

• Advantages – No bulky sensor – Measures N2O – Disposable sample line – Use with non intubated patients

• Disadvantages – Secretions block sample tube – Trap needed to remove excess water – Frequent calibration – Slow response – Sample flow may decrease tidal volume

ETCO2 • Waveform interpretation • I

– CO2 zero. Origination of exhalation, deadspace

• II– Steep upward slope, mixed deadspace gas

and alveolar gas • III

– Plateau, alveoli empty, end of plateau is PetCO2

• IV– Rapid decrease in CO2, patient inhalation

ETCO2

• In healthy individuals, the PetCO2 averages 1-5mmHg lower than ABG’s

(5-6%)

ETCO2 abnormal waveforms

• Hypoventilation

• Hyperventilation

• Leak

ETCO2 abnormal waveforms

• Disconnect

Transcutaneous monitors

• Provides continuous noninvasive estimated PO2 and PCO2

• Heats blood to arterialize it

• Dependant on age and perfusion status

• CO2 more reliable

• Used mostly in the NICU