Oxygen saturation and Arterial Blood gasses Flashcards
What is oxygenation dependent on
- amount of hemoglobin
- partial pressure of oxygen
- amount of oxygen bound to hemoglobin
What will best measure oxygenation
- CBC hemoglobin as it measure oxygen and hemoglobin
Signs and symptoms of hypoxia
- cyanosis - central vs peripheral
- tachycardia/arrhythmias
- peripheral vasoconstriction
- poor judgement/motor incoordination/slow reaction time
- restlessness/agitation/confusion
- fatigue
How is tachycardia a sign or hypoxia
- to increase CO
- since you can’t pick up as much each “load” you need more loads
Central cyanosis vs peripheral cyanosis
- central: related to low oxygen and seen around the lips, tongue, nail beds (mucus membranes where capillary beds are close to the surface
- Peripheral: poor perfusion ie during cold air
How to assess oxygenation status
- indirect: assessment of oxygen saturation of the blood (pulse oximetry)
- direct: sampling of arterial blood (ABGs)
SpO2
- measures oxygen saturation indirectly via pulse oximeter
- LED that detects the absorption of red light
- impacted by cold hands, nail polish, hypoxia, device malfunction, darker skin
SaO2
- measures oxygen saturation directly from blood sample
- ABGs
PaO2
- partial pressure of oxygen (mmHg)
directly from a blood sample (ABG)
Oxygen saturation and partial pressure normal values and abnormal values
Normal:
- PaO2: 80-100 mmHg
- >95%
Mild hypoxia:
- 60-80 mmHg
- 90-95%
Moderate hypoxia:
- 40-60 mmHg
-80-90%
Severe hypoxia
- <40 mmHg
- <80% severe hypoxia
Oxyhemoglobin dissociation curve shifted to the right is caused by
- increased temperature (body)
- increased PCO2
- decreased pH
- O2 unloads quicker/decreased affinity for O2
Oxyhemoglobin dissociation curve that is shifted to the left is caused by
- decreased temperature
- decreased PCO2
- increased pH
- increased affinity for O2
Normal arterial blood gas values
1. PaO2:
2. PaCO2
3. pH
4. HCO3
4. SaO2 (oxygen saturation
- PaO2: 80-100 mmHg
- PaCO2: 35-45 mmHg
- pH: 7.35-7.45
- HCO3: 22-26
- SaO2 (oxygen saturation): 95-99%
Arterial blood gases/blood gas analysis - oxygenation
How is it done and what does it look at
- typically through A-line due to needing multiple measurements
- drive intervention + realists of intervention
Looks at: - Arterial pH
- PaCO2
- PaO2
- HCO3
- SaO2
- oxygenation status is determined by the PaO2 and oxygen saturation SaO2
When does hypoxemia occur
- when PaO2 is <60mmHG and SaO2/SpO2 <90%
- patient with resting SaO2/SpO2 <90% usually require supplemental oxygen during exertion to avoid further desaturation
Oxygen titration order
- MUST be prescribed by an MD
- Can only function within the MD’s orders
- DO NOT increase oxygen without an order
Arterial blood gases/blood gas analysis of acid base
- arterial pH
- PaCO2
- PaO2
- HCO3
- Oxygen saturation
- acid base balance determined by pH, bicarbonate and PaCO2
Acidic state vs alkalotic state
- acidic state exists from TOO much CO2 or too little HCO3
- alkaloid state can exist from either TOO little CO2 or too much HCO3
Acidosis/acidemia
- pH <7.4
- decreased bicarbonate = metabolic acidosis
- increase PaCO2 = respiratory acidosis (aka, alveolar hypoventilation or hypercapnia)
Alkalosis/alkalemia
- pH >7.4
- increase bicarbonate = metabolic alkalosis
- decreased PaCO2 = respiratory alkalosis (aka - alveolar hyperventilation or hypocapnia)
Metabolic acidosis: what and how
- pH<7.4; HCO3 decreased
- acid accumulation from metabolic processes or loss of HCO3
causes: - ketoacidosis
- lactic acidosis
- renal failure
- diarrhea (excrete bases)
Metabolic acidosis signs and symptoms
- lethargy
- confusion
- headahce
- nausea
- vomiting
metabolic acidosis treatment
- monitor and treat underlying cause
Metabolic alkalosis: what and how
- pH>7.4 or increase in HCO3
- acid loss or gain of too much base
causes: - acid loss due to vomiting
- ingestion of alkali (antacids)
Metabolic alkalosis: signs and symptoms
- dysrhythmias, dizziness, irritability
- muscle cramps, twitching, spasms, paresthesia, numbness, tingling
- compensatory hypoventialtion
Metabolic alkalosis treatment
- monitor and treat underlying cause
Respiratory alkalosis: what and how
- pH>7.4; PaCO2 <35 mmHg
- hyperventilation
Causes:
- pain
- anxiety
- fear
- stress
- high altitude
- brain injury
- improper ventilation during anesthesia or ventilation
Respiratory alkalosis: signs and symptoms
- tachypnea
- SOB
- lightheadedness
- numbeness/tingling of extremities
- muscles spasms
- difficulty concentrating
Respiratory alkalosis:Treatment
- monitor and treat underlying cause
- slow down breathing or breathe into paper bag
- rebreather oxygen mask
- sedation
rebreather oxygen mask
- bag is attached and therefore you rebreathe some expired air which has CO2
Respiratory Acidosis: what and how
- pH <7.4; PaCO2 >45mmHg
- hypoventilation
causes
- lung disorders
- sleep disordered breathing
- diseases that impair breathing (COPD = not exhaling adequately and therefore retaining CO2)
- drugs overdose
- sepsis
Respiratory Acidosis: signs and symptoms
- dyspnea
- disorientation
- coma
- headache
- drowsiness
- hypoxemia/ hypercapnia
Respiratory Acidosis: treatment
- monitor and treat underlying cause
- support ventilation if necessary
Rules to remember with acidotic states and alkalotic states
- pH determines acid/alkaline states
- CO2 has an inverse relationship with pH
- HCO3 has a direct relationship with pH
Respiratory failure
- arterial blood pH<7.35 with PaCO2>45
OR - hypoxemia PaO2<60mmHg
- not relieved with O2 = may need ventilator
Types of respiratory failure
- lung failure
- pump failure
lung failure
- type 1 hypoxemic respiratory failure
- PaO2 <60 mmHg
- ventilation/perfusion mismatch - EX: pulmonary edema
- deadspace and shunt
pump failure
- type 2 hypercapnia respiratory failure
- reduced breathing effort
- resistance to breathing ex: COPD
- respiratory pump is impacted mechanically
- PaCO2 >45 mmHg and pH <7.35
