ABG, Oximetry, Spirometry Testing Flashcards
What info do you get from ABG?
Acid base status
Oxygenation (dissolved O2, saturation of Hb)
CO2 elimination –> ventilation
Levels of carboxyhemoglobin/methemoglobin
What are the indications for ABG testing?
Asses ventilatory status (aka CO2 elimination)
oxygenation
acid-base status
Assess response to intervention
What are the contraindications for ABG testing?
Bleeding diathesis
AV fistula
Severe peripheral vascular dz
No arterial pulse
Infection over site
What is better about pulse ox compared to ABG?
Non-invasive
Continuous data
What are drawbacks about pulse ox compared to ABG?
No VENTILATION (pCO2)!!
No acid-base status
Unreliable when pO2 < 70-80%
Can get errors
No methemoglobin/carboxyhemoglobin
Which artery is best for ABG and why?
Radial (can use femoral, dorsal is pedis, brachial in emergency)
Superficial
Has collaterals
Easily compressible
What are the normal ABG values (pH, PaO2, PaCO2, HCO3)?
pH = 7.35 - 7.45
PaO2 = 80 - 100
PaCO2 = 35 -45 mmHg
HCO3 = 22 - 26 mEq/L
What are acidotic ABG values (pH, PaO2, PaCO2, HCO3)?
pH = < 7.35
PaO2 = N/A
PaCO2 = > 45 mmHg
HCO3 = < 22 mEq/L
What are alkalotic ABG values (pH, PaO2, PaCO2, HCO3)?
pH = > 7.45
PaO2 = N/A
PaCO2 = < 35 mmHg
HCO3 = > 26 mEq/L
When interpreting ABG, when would you decide someone has respiratory acidosis?
Low pH
High pCO2
When interpreting ABG, when would you decide someone has metabolic acidosis?
Low pH
Low HCO3
When interpreting ABG, when would you decide someone has respiratory alkalosis?
High pH
Low pCO2
When interpreting ABG, when would you decide someone has metabolic alkalosis?
High pH
High HCO3
What happens in respiratory alkalosis?
For every 10 decrease in pCO2 –> HCO3 decreases by 2/increase in pH of 0.08
What are the central causes of respiratory alkalosis?
Respiratory center issues
Ischemia
CNS tumor
Hyperventilation
What are the lung issues that cause respiratory alkalosis?
Pneumonia
Asthma
PE
What are the chest cavity issues that can caues respiratory acidosis?
Flail Chest
Pneumothorax
Effusion
What are the central causes of respiratory acidosis?
Sedation
CVA
Narcotics
Neuromuscular issues
What are some lung issues that can cause respiratory acidosis?
Pneumonia
Asthma
FB
COPD
What is spirometry used for?
Diagnosing Asthma/COPD
What are the most important indications to use spirometry?
Persistant cough
Chronic sputum production
Breathlessness on exertion
Reduction in activity
What are some other indications for spirometry testing?
Recurrent/chronic respiratory symptoms
Occupational exposure to respiratory irritants
Family Hx of respiratory dz/symptoms –> alpha1-antitrypsin; early onset emphysema
REQUIRED quality measure for accurate COPD diagnosis
Selective screening in high risk populations (fam. medicine)
What types of diseases can spirometry differentiate?
Restrictive vs Obstructive
Is Spirometry recommended for screening of COPD pts?
NOT routine screening tool
Only recommended in PRESENCE of respiratory symptoms
Why is QUALITY spirometry important?
Prevent overdiagnosis of COPD
According to the NAEPP (National Asthma Education & Prevention Program) when should you use spirometry?
For initial diagnosis (can’t diagnosis w/o spirometry testing!)
After treatment is initiated/symptoms and peak flow have stabilized
During periods of loss of asthma control
Assessing response change to pharmacotherapy
Every 1 - 2 years to assess maintenance of airway function
Check PEF meter accuracy
What is the FEV1 or FEV1/FVC of a asthmatic 5 - 11 yo that is considered well controlled?
FEV1 = > 80% predicted
FEV1/FVC = > 80%
What is the FEV1 or FEV1/FVC of an asthmatic 5 - 11 yo that is considered not well controlled?
FEV1 = 60 - 80% predicted
FEV1/FVC = 75 - 80%
What is the FEV1 or FEV1/FVC of an asthmatic 5 - 11 yo that is considered very poorly controlled?
FEV1 = < 60% predicted
FEV1/FVC = < 75%
What do you have to do before you do spirometry?
Coach patient (so get max effort –> accuracy)
What is the most important varible for spirometry?
Pace of expired air –> should be released w/ explosive force)
What is the minimum exhalation interval?
6 seconds w/ 2 second plateau
How should the patients be positioned during spirometry?
Sitting or Standing
What are the contraindications for spirometry (edit this, there’s a lot)?
> 6 wks since last exacerbation
MI < 3 -6 months ago
Unstable agina in last 24 hrs
Haemoptysis of unknown origin
Recent Eye, abdominal Surgery (< 3 - 6 months ago)
CVA < 3 -6 months ago
Pt w/ TB
PE < 3 -6 months ago
Ear infection
Sponatneous pneumothorax
Aortic Aneurysm
What are some of the common reasons for unacceptable/unreliable readings?
Inadequate or incomplete inhalation
Lack of blast effor during exhalation –> false (+) COPD
Additional breath during maneuver
Lips not tight around mouthpiece
Slow start to forced exhalation
Exhalation stops before complete expiration
Exhalation through nose
Coughing
Tight/Restrictive clothing
What should you avoid during spirometry?
Unsatisfactory start (excessive hesitation/false start)
Air leak
Coughing during first second
Early termination of forced expiration
Glottis closure
Obstructed mouthpiece (Tongue/false teeth/Chewing gum)
What is FEV1?
Forced expired volume in 1 second
What is FVC and what can be substituted for this value?
Forced Vital Capacity
FEV6 can substitute it
What is PEFR?
Peak expiratory flow rate
(not reproducible, but useful in tracking progress)
What is FEF 25 - 75%?
Forced expiratory flow between 25 - 75% of the vital capacity
(Usually not clinically useful)
What are some factors that would affect normal spirometry values?
Height –> Tall = larger lungs
Age –> Function declines w/ age
Sex –> females have smaller volumes
Race –> Blacks/Asians had smaller lung volumes
Posture –> reduced in supine position
Why is it important to enter accurate values for pt’s bio-demographic variables?
Prevent misdiagnosis
