PFT's and ABG's Flashcards
PFT Definition
PFT’s obtained on a patient are compared to normal values from population studies. The percent of predicted normal is used to grade the severity of abnormal.
PFT’s include:
Simple Spirometry
Lung Volume Measurements
Diffusing Capacity
Arterial Blood Gases
TV
Tidal Volume: The amount of air that is breathed in and out during resting or normal breathing
VC
Vital Capacity: The total amount of air that can be exhaled after maximal inspiration
AKA Slow Vital Capicity (SVC)
FVC
Forced Vital Capacity: The total amount of air that is exhaled forcefully after a forceful inspiration
FEV1
Forced Expiratory Volume-1 second: The amount of air exhaled forcefully in the first second of expiration
FEV1/FVC
The FEV1 devided into the FVC
Used to determine if there is an obstruction present
IRV
Inspiratory Reserve Volume: The amount of air that is inhaled after a normal breath
IC
Inspiratory Capacity
TV + IRV = IC
ERV
Expiratory Reserve Volume
The amount of air exhaled after the TV
FRC
Functional Residual Capacity
ERV + RV = FRC
The amount of air in your lungs at the end of a normal breath
RV
Residual Volume
The amount of air left in the lungs after a maximal expiration
(Calculated)
TLC
Total Lung Capacity
The amount of air in the lungs after a maximal inspiration
TLC = TV + IRV + ERV + RV
Contraindications for PFT’s
Recent CP or MI
Pneumothorax (recent or untreated)
PE (wait 2-3 months after resolution)
Recent surgery: Eye, Chest, Abdomen
Predicted Values
Based on age, height, and gender. Sometimes race.
Lower Limit of Normal (LLN) is under 80% of predicted
Slow Vital Capacity Measurements
Passive maneuver using a Wright Respirometer
Simple measurement when only VC is needed.
Frequently used in neuro exam when monitoring things like MD, Myasthenia Gravis, and Guillain Barre
FVC Measurement
MC screening tool because can be performed anywhere using a spirometer
Reports
Time Volume Curve: can use to calculate FEV1 and FVC
Flow Volume Loop: size and shape can indicate location of airflow obstruction to help differentiate disease processes
- Restriction: Normal shape but smaller
- Obstruction: Scooping
- Fixed Obstruction: Small circle
Can differentiate between obstructive and restrictive processes
Bronchoprovocation Test
Used to determine airway hyperreactivity
Methacholine is the gold standard
Cold and exercise challenges can also be used
Can be used to differentiate between asthma and VCD (Excercise challenges)
Lung Volumes
Nitrogen washout or helium dilution used to measure ERV, RV, FRC, and TLC
Measured in by body plethysmography (body box)
Air trapping denoated an elevation in FRC, ERV and/or RV
Hyperinflation denotes an elevation in the TLC
FRC, ERV, RV, and TLC can be decreased in restrictive processes
DLCO or Diffusing Capacity
Uses a small volume of CO to assess the ability of gas to diffuse across the alveolocapillary membrane
Generally used to distinguish between obstructive diseases
i.e. COPD is decreased, asthma is increased
FEV1/FVC Ration
Found during FVC measurements from Time Volume Curve
FEV1: normal lung is >70%
Obstructive–decreased flow (low FEV1/FVC)
Restrictive–decreased volume (low FVC)
Non-Pharm Interventions
Chest Physiotherapy (PT) for pts with thick secretions (CF)
Oxygen is hypoxia is present
Smoking cessation
Pulmonary Rehab
- Exercise and conditioning including breathing retraining, ventilatory muscle training, energy conservation as it applies to ADL’s
- Med education
- Education about what to expect from dz (i.e. sleep disturbances)
- Nutrition, smoking cessation
- Advance care planning
- Contraindications: pt unmovitivated to change, dz is progressed to the point where it will not help, or have other comorbidities that make PR an unsafe option
ABG Definition
ABG measures acidity and the levels of oxygen and carbon dioxide
Used to see how well the lungs are able to diffuse gas
