PULSE OXIMETRYprinciple,

applications & interpretation

RAVINDAR BETHI

PULSE OXIMETRYis one of the most essential monitors for routine use in anesthesia and intensive care

PULSE OXIMETRYwhat does it measure ?

PULSE OXIMETRYIt measures the O2 saturation of Hb in arterial blood

PULSE OXIMETRYIt measures the heart rate

PULSE OXIMETRYgives an idea about tissue perfusion by pulse wave form

PULSE OXIMETRYgives an idea about tissue perfusion by pulse wave form

PULSE OXIMETRYgives an idea about tissue perfusion by pulse wave form

• increased amplitude indicates vasodilatation

Dicrotic notch descends

PULSE OXIMETRYgives an idea about tissue perfusion by pulse wave form

• decreased amplitude indicates vasoconstriction or hypovolemia

PULSE OXIMETRYgives an idea about tissue perfusion by pulse wave form

Area under the curve indicates stroke volume

PULSE OXIMETRYgives an idea about tissue perfusion by pulse wave form

Can be used for assessment of blood flow in re-vascularised limb In re-anastamosed limb In a digit after or during surgery

The principle

• What is oxygenation of a Hb ?

The principle

• What is oxygenation ?O2

Oxy HbDeoxy Hb

The principle

• What is oxygenation ?O2 O2

OxyHb

DeoxyHb

The principle

• What is oxygenation ?O2 O2

O2

OxyHb

DeoxyHb

The principle

• What is oxygenation ?O2 O2

O2 O2

OxyHb

The principle

• What is oxygenation ?O2 O2

O2 O2

O2 O2

O2 O2

O2 O2

O2

O2 O2

O2 O2

O2 O2

O2 O2

O2 O2

O2 O2

O2 O2

O2 O2

O2 O2

O2 O2

O2 O2

O2 O2

O2 O2

O2 O2

O2 O2

O2 O2

O2 O2

O2

Oxygen saturation = Oxygen contentOxygen capacity

X 100

The principle

• What is oxygenation ?O2 O2

O2 O2

O2 O2

O2 O2

O2 O2

O2

O2 O2

O2 O2

O2 O2

O2 O2

O2 O2

O2 O2

O2 O2

O2 O2

O2 O2

O2 O2

O2 O2

O2 O2

O2 O2

O2 O2

O2 O2

O2 O2

O2 O2

O2

Oxygen saturation = Oxygen contentOxyHb+DeoxyHb

X 100

The spectrophotometry

When a light of particular wavelength passes though a solution sample, the compound of interest absorbs these specific radiations

The spectrophotometry

When a light of particular wavelength passes though a solution sample, the compound of interest absorbs these specific radiations

The spectrophotometry

The spectrophotometry

Oxygen saturation = Oxygen contentOxygen capacity

X 100

The spectrophotometry

Oxygen saturation = OxyHbOxyHb+DeoxyHb

X 100

The spectrophotometry

Oxygen saturation = OxyHbOxyHb+DeoxyHb

X 100

The spectrophotometry

Photosensor(2 LEDs)

Photodetector

Signals from other sources than arterial

The plethysmography

The plethysmography

The spectrophotometry& plethysmography

REFLECTION PHOTOMETRY

ABSORPTION PHOTOMETRY

REFLECTION PHOTOMETRY

ABSORPTION PHOTOMETRY

SpO2 vs SaO2ABG RESULT

• SaO2 96 %• PaO2 90 mmHg

Non functional Haemoglobins SaO2 50%

SpO2 100%

SpO2 vs SaO2ABG RESULT

• SaO2 96 %• PaO2 90 mmHg

Oxy Hb

Non functional Haemoglobins SaO2 50%

SpO2 100%

SpO2 vs SaO2ABG RESULT

• SaO2 96 %• PaO2 90 mmHg

Oxy Hb

OXIMETRY GAP

SaO2 vs PaO2

O2

PRESSURE GRADIENT-1

SaO2 vs PaO2

O2

PRESSURE GRADIENT-1

O2

SaO2 vs PaO2

PRESSURE GRADIENT-2

O2

O2

SaO2 vs PaO2

O2

PRESSURE GRADIENT-2

O2

SaO2 vs PaO2

O2

PRESSURE GRADIENT-1

O2

SaO2 vs PaO2

O2

PRESSURE GRADIENT-2

O2

SaO2 vs PaO2

O2

PRESSURE GRADIENT-2

O2

SaO2 vs PaO2

SaO2 vs PaO2

PaO2 100mmHg

SpO2 100%

SaO2 vs PaO2

PATIENT BREATHING

100% O2

SaO2 vs PaO2

PATIENT BREATHING

100% O2

PaO2 >300SpO2

MAXIMUM 100%

APPLICATIONS

PATIENT BREATHING

100% O2

PaO2 >300SpO2

MAXIMUM 100%

APPLICATIONS

PATIENT BREATHING

100% O2

PaO2 <70

SpO2

MAXIMUM 100%

ALKALOSIS, HYPOTHERMIA

APPLICATIONS

PATIENT BREATHING

100% O2

PaO2 >300SpO2

MAXIMUM 100%

EFFECT OF PREOXYGENATION

APPLICATIONS

PATIENT BREATHING

100% O2

SpO2

100%

BRONCHIAL ASTHMA

APPLICATIONS

PATIENT BREATHING

100% O2

BRONCHIAL ASTHMA

ALVEOLAR COLLAPSE

SpO2

APPLICATIONS

PATIENT BREATHING

60% O2

PaO2 90SpO2

92%

BRONCHIAL ASTHMA

APPLICATIONS

BRONCHIAL ASTHMA

PATIENT BREATHING

60% O2

PaO2 90SpO2

92%

NITROGENSAVES LIFE

!!

OXYGEN DIFFUSES

OUT

APPLICATIONS

PATIENT BREATHING

100% O2

PaO2 >300SpO2

MAXIMUM 100%

COPD

APPLICATIONS

PATIENT BREATHING

100% O2

PaO2 >300SpO2

MAXIMUM 100%

COPDHypercarbia

hypoxia

TAKE HOME MESSAGES

When SpO2 value can be a false reading?• in Carbon monoxide poisoning• in Methemoglobinemias

TAKE HOME MESSAGES

Why only 92% in Bronchial Asthma and COPD ?

TAKE HOME MESSAGES

When SpO2 gives false readings ?• ...in methylene blue therapy, deep

jaundice…

TAKE HOME MESSAGES

When SpO2 is falsely low ? • Ambient light…tourniquet, • Compartment syndrome with

pulsatile veins…

TAKE HOME MESSAGES

• When even SpO2 or PaO2 is not just enough …if PaCO2 is low in head injury

TAKE HOME MESSAGES

• ECG and SpO2 waves in arrhythmias, PEAObserve

TAKE HOME MESSAGES

Take your own pulse oximetry while holding breath

Observe

TAKE HOME MESSAGES

• How SpO 2 alone is unreliable as monitor at intubation?

TAKE HOME MESSAGES

• Why the animals living in high altitudes have a high RBC count ?• Why the RBC count increases in high altitudes?

O2

O2

In order to use the search light effectively we need to have a fairly thorough knowledge of

all the territory to be searched.

THANK YOURAVINDAR BETHI