Resp Tests Flashcards
What are the uses of pulmonary function tests?
the tests look at how:
-much air lungs can hold
-quickly air can move in and out of lungs
-well the lungs put O2 into and remove CO2 from the blood
Differentiate between the different lung volumes.
tidal volume (TV):
-air exhaled during normal respiration
inspiratory reserve volume (IRV):
-maximum air inhaled above TV
expiratory reserve volume (ERV)
-maximum air exhaled below TV
residual volume (RV):
-volume of air remaining after maximal expiration
What is the total lung capacity?
sum of all 4 volumes (TV, IRV, ERV, RV)
total volume of air in the lungs at maximal inspiration
What is the functional residual capacity?
volume of air in the lungs at the end of normal expiration
What is the vital capacity?
total volume of air exhaled after maximal inhalation
What is the FEV1?
forced expiratory volume in 1 second
-patient inspires to TLC and exhales maximally
-volume of air exhaled in first second=FEV1
What is FEV1 the best measure for?
assessing severity of airflow obstruction
What is the FVC?
forced vital capacity
-total volume of air expired as rapidly as possible from TLC
What is the use of the FEV1/FVC ratio?
differentiate between restrictive from obstructive lung disease
What are the airflow measures?
FEV1
FVC
FEV1/FVC ratio
What are the many uses of spirometry?
diagnosing lung disease & assessing severity
measuring the effect of a disease on lung function
monitoring course of disease or result of therapeutic intervention
assessing surgical risk
assessing prognosis for pulmonary conditions
pre-employment screening and surveillance of employees
assessing the potential effects of environmental lung disease
Briefly describe how spirometry is performed.
patient takes the deepest breath they can
then exhale into the sensor as hard possible, for as long as possible, preferably for at least 6 seconds
What are the important indices measured with spirometry? What are the results of spirometry compared to?
FEV1, FVC, FEV1/FVC ratio
compared to personal best, and predicted normal
What is the most accurate test for predicting and measuring lung disease?
spirometry
What are the limitations of spirometry?
requires full cooperation of the patient
CI: increased intracranial or intraocular pressure, increased intrathoracic and intrabdominal pressure, increased myocardial demand or changes in bp, risk of infection
Differentiate between obstructive and restrictive lung disease.
obstructive:
-inability to get air out of the lung
-FEV1/FVC ratio=decreased
restrictive:
-inability to get air in the lung and maintain normal lung volumes
-FEV1/FVC=normal or maybe increased
How do we determine reversibility of airway obstruction?
PFTs are repeated 10-15min after administration of inhaled B2 agonist (salbutamol)
increase of FEV1 of 12% after an inhaled agonist=acute bronchodilator response
Describe peak expiratory flow rate.
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 PB or predicted values
requires maximum patient effort
intended for patient self-monitoring once diagnosis is established
Describe carbon monoxide diffusing capacity.
measurement of the ability of carbon monoxide to diffuse across the alveolar-capillary membrane
two methods: steady state, single breath or breath-holding
What is a scenario where the carbon monoxide diffusing capacity will be reduced?
clinical situations where gas transfer from the alveoli to capillary blood is impaired
What is pulse oximetry?
utilizes light absorptive characteristics of hemoglobin and the pulsating nature of blood to aid in determining oxygenation status
What do arterial blood gases reflect?
how well the lungs are oxygenating the blood and are useful to assess acid-base status
-critically ill patients, effectiveness of therapy, titrate oxygen flow rates, assess patient for home oxygen
Differentiate PaCO2 and PaO2.
PaCO2: pressure/tension exerted by CO2 in the blood
PaO2: level of oxygenation of arterial blood
How do we interpret acid-base disturbances?
- check the pH (indicates if blood is acidic, normal, alkaline)
- determine the primary cause of the disturbance
-check PaCO2 (indicates lung function to excrete CO2)
-check HCO3 (indicates kidney function) - check for compensation/correction
-resp comp occurs quickly (mins)
-metabolic comp occurs slowly (days) - calculate the anion gap
-Na - (Cl+HCO3)
-normal range: 3-11mmol/L (if elevated=metabolic acidosis) - check the PaO2 and O2 saturation
