spirometry Flashcards
physical description importants
age, height, male/female
calculate pack years
packs smoked per day x years smoked
how long should patient stop smoking before pft
minimum of one hour
bronchodilators should be with held how long prior to testing
short acting beta2- 4 hours
long acting beta2- 12 hours
anticholinergics- 8 hours
steroids do not need to be held
patients who wear o2 during a pft
may be necessary to place patient on o2 between maneuvers or tests
o2 should be removed at least 20mins prior to ABG
contraindications to pft
hemoptysis in past 24 hours
unstable vital signs
unable to cooperate
pft patients should avoid
consuming alcohol for at least 4 hours prior to testing
vigorous exercise at least 30 mins prior to testing
wearing restrictive clothing
eating a large meal 2 hours prior to testing
spirometry testing
identify restrictive and obstructive diseases
volumes and flow rates
restrictive= decreased volume
obstructive= decreased flow rates
slow vital capacity
maximum expiration following a maximum inspiration
typical = 4800mL or 4.8L
decreased with restrictive disease
best volume to diagnose a restrictive disease
Tidal Volume
normal breathing
typcail= 500ml
decreased with restrictive diseases
minute volume
tidal volume x respiratory rate
inspiratory reserve volume
largest volume of has that an in inspired above a normal tidal volume
measured with a spirometer
typical= 3100 mL
decreased with restrictive diseases
expiratory reserve volume
largest volume of gas tha can be expired from a rest end-expiratory level
measured with a spirometer
typical= 1200mL
decreased with restrictive disease
will be lower than IRV
inspiratory capacity
largest volume that an be inspired from end-expiration
measured with a spirometer
typical = 3600mL
decreased with restrictive disease
static volumes
TLC
FRC
RV
Forced Vital Capacity
maximum inspiration followed by a forced and rapid maximum expiration
this maneuver generates the FVC which is a volume and may be substituted for the SVC to identify restrictive lung disease
SVC VS FVC
a patient with normal lung function will have values that are approx. the same for both
if the SVC is greater than the FVC suspect obstructive lung disease
if the FVC is greater question the patients effort
Technique for FVC
inspire as deeply as possible
breath hold
exhale as forcefully as possible
continue exhaling as hard as possible until an expiratory plateau occurs or expiration time of 15 seconds
trouble shooting FVC
if the patient passes out dring the FVC maneuver= vaso vagal response
if FVC > 10% after bronchodilator can be suggestive or air trapping or positive post bronchodilator response
Peak Expiratory Flow
the maximum flowrate achieved during a forced expiratory maneuver
typical= 10L/ sec
very dependent on patient effort
best way to measure asthma patients
Forced Expiratory Flow 200-1200
the average flowrate that occurs during a forced expiratory maneuver after the first 200mL has been expired
typical = 6 L/sec
measures airflow within the large airways
decreased with tumors and obstructive disease
forced expiratory flow 25%-75%
average flowrate during the middle half of a forced expiratory maneuver
typical= 4-5 L/sec
small airways
decreased with obstructive disease
most sensitive test to detect the presence of early small airway disease
only value needed to diagnose obstructive disease is?
FEV1
Forced Expiratory Volume/Time (FEV1)
volume of gas expired over a given time interval in seconds
decreased flows indicated obstructive disease
used to assess the degree of improvement after bronchodilator admin.
Forced Expiratory Volume/Time/Forced Vital Capacity Ratio
the forced expiratory volume for a given time ineterval expressed as a % of the vital capacity
minimum values
FEV1/FVC%- 70% obstruction
decreased with obstructive disease
normal with restrictive disease
calculating the FEV1/FVC%
divide the FEV1 by the FVC then multiply by 100
Maximum Voluntary Ventilation
largest volume of air inhaled and exhaled over a 12 second period
typical= 170 L/min
if patient has a low tidal volume and a fast reparatory rate during the MVV procedure, this indicates restrictive lung disease
MVV technique
patient breathes into a spirometer as deeply ans as rapidly as possible for a minimum of 12 seconds
calculating MVV
of breaths x volume x 5
estimating patients effort for MVV by using the FEV1
multiple the FEV1 by 35
if the mvv is less than that value suspect poor patient effort
FVC to generate a FLow-Volume Loop
forced expiratory vital capacity maneuver followed by a forced inspiratory vital capacity maneuver
volume is horizontal
flow is vertical
expiration above baseline and inspiratory below
pre and post bronchodilatory testing
used to determine degree of reversible airway obstruction
indications for bronchodilator testing
- FEV1 below 80% on pre bronchodilator
- cough of unknown etiology
- known asthmatic condition
- anytime airway hyperreactivity is suspected
fastest acting bronchodilator
isoproterenol
post bronchodilator results
the FEV1 must improve by at least 12% and 0.200L in order to be considered a reversible condition
patients with asthma may improve as much as 50%
calculating % change in pre and post bronchodilator
(post FEV1- pre FEV1) divide pre FEV1
obstructive diseases
C Cystic Fibrosis B Bronchitis A Asthma B Bronchiectasis E Emphysema
secretions and bronchospasm reduce flow
interpretation of PFT data
the measured value is divided by the predicted value to obtain a % predicted
> 80%.... normal < 80%... mild dysfunction <70%... moderate < 60%... moderate/severe < 50 %... severe < 35%... very severe
pediatric spirometry testing
good start of test and are free of artifact for at least the first second are called usable
