Respiratory Tests Flashcards
Pulmonary Function tests (PFT’s) look at how:
much air lungs can hold
quickly air can move in and out of lungs
well the lungs put oxygen into and remove carbon dioxide from the blood
To determine respiratory values, how many tests are used?
Multiple tests required to determine all values
Some tests may be repeated after using……
Some of the tests may be repeated after using medication (used after a bronchodilator)
The air in the lung is divided in how many compartments? What are they? what do they measure?
Tidal volume (TV): (normal respiration)
- air exhaled during normal respiration
Inspiratory Reserve Volume (IRV):
- maximum air inhaled above TV
Expiratory Reserve Volume (ERV):
- maximum air exhaled below the tidal volume
Residual Volume (RV):
- volume of air remaining in the lungs after maximal expiration
The sum of all 4 compartments is……
TOTAL LUNG CAPACITY
How many lung capacities are there? What do they measure?
Total Lung Capacity (TLC):
- The sum of all 4 compartments or volumes
total volume of air in the lungs at maximal inspiration (VC +RV)
Functional Residual Capacity (FRC):
volume of air in the lungs at the end of normal expiration
Vital Capacity (VC):
- total volume of air exhaled after a maximal inhalation
What is the FEV1? What does it measure?
Forced Expiratory Volume in 1 Second
Patient inspires to TLC and exhales maximally. The volume of air exhaled in the first second = FEV 1
Best measure for assessing severity of airflow obstruction
What is FVC? What does it measure?
Forced Vital Capacity
- Total volume of air expired as rapidly as possible from TLC
What is the difference between obstructive and restrictive lung disease?
Obstructive lung diseases include conditions that make it hard to exhale all the air in your lungs. People with restrictive lung disease have trouble fully expanding their lungs with air.
What is the FEV1/FVC ratio? What is considered a healthy FEV1? Asthma vs. COPD?
Helps to differentiate restrictive from obstructive lung disease (% of total volume of air)
The FEV1 is usually expressed as a % of the total volume of air exhaled and is reported as the FEV1/FVC ratio.
A FEV1 of 80% is normal.
FEV1 is lower in obstructive lung diseases and normal to only a little lower in restrictive lung diseases
In asthma, after bronchidilator, FEv1 improves whereas COPD it does not.
What are some other PFT’s commonly used?
Spirometry (Best test of pulmoary function)
Peak Expiratory Flow Meter
Carbon Monoxide Diffusing Capacity (DLCO)
What is spirometry? Uses?
Uses a spirometer to objectively assess an individual’s pulmonary performance
Uses:
Diagnosing lung disease & assessing severity
Measuring the effect of a disease on lung function
Monitoring the course of disease or result of therapeutic intervention
Assessing surgical risk
Assessing prognosis for pulmonary conditions
Pre-employment screening and surveillance of employees at risk for occupational lung diseases
Assessing the potential effects of environmental lung disease
Who should perform a spirometry test?
Should be conducted by trained personal where there is a quality assurance program
Basic procedure of spirometry test?
In general, the patient is asked to take the deepest breath they can, and then exhale into the sensor as hard as possible, for as long as possible, preferably at least 6 seconds.
What is measured by spirometry?
FVC
FEV1
FEV1/FVC ratio
Most accurate PFT?
Spirometry
What are the results of spirometry compared too?
“Predicted normal” (based on height, weight, race, age and sex)
Patient’s “Personal Best” lung function
Limitations of spirometry?
Requires full cooperation of the patient
Contraindications of spirometry?
Increases intracranial or intraocular pressure (brain surgery, concussion, eye surgery)
Increases in intra-thoracic and intra-abdominal pressure (surgery)
Increases in mycardial demand or changes in bp (severe hypertension, significant arrthymias)
Risk of infection (active TB, hameophilus)
What populations is spirometry not conducted in?
Do not do spirometry under age of 6, elderly, dementia, language barriers
Define obstructive lung disease? FEV1/FEC Ratio?
The inability to get air out of the lung
FEV1/FVC Ratio: Decreased
Define Restrictive Lung Disease? FEV1/FEC Ratio?
The inability to get air into the lung and maintain normal lung volumes
Decreased air in all divisions (i.e. interstitial lung disease, myasthenia gravis, mechanical conditions)
FVC that is low, FEV1 may or may not be low
Ratio: Normal or increased
Spirometry bronchodilator challenege is used to determine…..
REVERSIBILITY
Determining reversibility of airway obstruction can be performed using spiromnetry. How? Use?
PFTs are repeated 10-15 minutes after administration of an inhaled 2 agonist (eg., Salbutamol). This determines if a reversible component to the airway obstruction exists.
An ↑ of FEV1 of 12% (>0.2L in adults) after an inhaled agonists = acute bronchodilator response (reversibility check)
Patient should withhold regular medications prior to testing
If you did not see reversibility, than COPD (progressive disease)
Asthma is reversible
Best way to differentiate asthma and COPD
What is Peak Expiratory Flow Rate? Counselling, use, FEV1 compartibility?
Measured with a portable peak flow meter
Maximal flow rate that can be produced during forced expiration (L/min, L/sec)
Results are compared to “personal best” or to “predicted values”
Changes in PEF generally parallel those of the FEV1, however it is less reproducible
Required maximum patient effort for accuracy
PATIENT EDUCATION is impt for proper technique
Intended for patient self-monitoring once diagnosis established
What is carbon monixe diffusing capacity (DLco) testing? Methods? Uses?
Measurement of the ability of carbon monoxide to diffuse across the alveolar-capillary membrane (gas exchange)
Two methods:
Single breath or breath-holding method
Steady state method
Will be reduced in all clinical situations where gas transfer from the alveoli to capillary blood is impaired (late stages of COPD)
What is pulse oximetry?
Utilizes light absorptive characteristics of hemoglobin and the pulsating nature of blood to aid in determining oxygenation status
Define Arterial Blood Gas Test. Use?
An essential function of the lungs is to maintain blood gas homeostasis (oxygenation and ventilation)
ABG’s reflect how well lungs are oxygenating the blood and are useful to assess acid-base status
Useful for monitoring critically ill patients, monitoring effectiveness of therapy, titrate oxygen flow rates, assess patient for home oxygen
What is an acid? Example?
Any substance with a pH < 7.0. eg., CO2
What is a base? Example?
Any substance with a pH > 7.0. eg., HCO3 (Bicarb)
What is PaCO2?
Pressure or tension exerted by dissolved CO2 gas in the blood (CO2 is combined with hemoglobin & transported to the alveolar capillaries where it is released)
What is PaO2?
Indicates the level of oxygenation of arterial blood
Define metabolic in acid-base balance?
refers to a disorder from an alteration in HCO3- (influenced by the kidneys)
Define respiratory in acid-base balance?
refers to a disorder from an alteration in CO2 (influenced by the lungs)
What is the anion gap formula?
AG = Na+ - (Cl- + HCO3-)
Normal range: 3-11 mmol/L
If elevated = metabolic acidosis (use as a side check, can be elevated in other conditions)
NO INFORMATION ABOUT RESPIRATORY
Time Range of Compensation
Time frame (respiration compensation happens very quickly, metabolic is slower (may take days))
Respiratory compensation – Lungs
Metabolic compensation – Kidneys (will release bicarb in blood if respiratory acidosis)
Normal ph indications:
pH<7.35 = acidosis
pH>7.45 = alkalosis
O2 Saturation Normal Value
≥ 95%
What is a bronchoscopy?
An endoscopic technique of visualizing the airways
The bronchoscope is inserted through the nose or mouth (or tracheostomy)
Tissue and/or fluid samples can be taken if needed
Can be used diagnostically or therapeutically
