Mid-Term Flashcards
What are some indications For PFTs
- Diagnosis
- Screening (pre-op)
- Monitoring
- Effects of chemicals and toxic medications
What is the Gold standard for diagnosing obstructive diseases
Spirometry
What 3 tests are involved in PFT
- Spirometry
- Lung volumes
- DLCO
What do we use to diagnose Restrictive diseases
Lung volumes
What do we use to diagnose gas exchange?
DLCO
For obstruction, DLCO is used to determine the (2)
- severity of the obstruction
- ruling out Emphseyma
Predicated values come from a national data base based on 4 demographics. What are they?
HGAR
- Height
- Gender
- Age
- Race
FEF 50% is the
most accurate measure used to determine pt effort
FEF 25%- 75% reflects
abnormalities in the small airway
When is FEV1 measured
during the FVC
FEV1 is called
Forced Expiratory Volume over 1 second
FEV1/FVC ratio defines
the obstruction
FEV1 defines the
degree/severity of the obstruction or restriction
If FEV1/ FVC ratio is less than ___% what does that indicate?
75%;
obstruction disease (CBABE)
If FVC is _______/high ( ____%) you have an…
normal;
80%
obstruction only
If FVC is low <80% you may have a
restrictive component or mixed
FEV1 <80% to determine if its
mild, moderate moderately severe, severe, or very severe
Mild is
70- 79%
Moderate is
60- 69%
Moderately severe is
50- 59%
Severe is
35- 49%
Very severe is
<35
Define Peakflow
A maximal inspiration, followed by a maximal forced exhalation
What are the predicated values based on for peak flow?
HAG
- Height
- Age
- Gender
If you do not have FEV1/ FVC which do you look at first and why?
RV for air trapping
If RV is high what do you do?
Look at the TLC
If FVC is low (<80%) it is considered
mixed
If FVC is normal or high then you have an
Obstruction only
How do we measure a pt’s height
W/o shoes
What are some contraindications for Spirometry testing?
- Myocardial infarction within the past month
- Chest abdominal, facial, or oral pain
- Stress incontinence
- Dementia, confusion
- Hemoptysis
- Recent cataract surgery (extra pressure)
- Recent abdominal or thoracic surgery
If you want a good effort then what must you do?
Coach pt
How do we know if test is valid?
If it is acceptable and replicable
HE measures (2)
FRC and estimate lung volumes
How long do we perform HE
until equilibrium is reached
For HE test how long do you have to wait until you can retest
5 minutes
Where do we measure alveolar pressure?
At the mouth when the shutter is clsoed
What can cause the DLCO to decrease? (7)
- Asthma
- Emphysema
- PNA
- Pulmonary edema
- OSA
- COPD Exacerbation
- Radiation
What can cause the DLCO to increase (3)
- Polycythemia (increased RBC)
- Increase in pulmonary blood flow (e.g Exercise)
- Alveolar hemorrhage
Would radiation increase or decrease DLCO?
Decrease
The jones method measures
breath hold from 0.3 of the inspiratory time to the midpoint of the alveolar sample
Minute ventilation equation
VE= VT x RR
Respiratory Exchange Ratio (RER) is the ratio between the
volume of carbon dioxide produced (VCO2) divided by the volume of O2 consumed (VO2)
Minute volume must be correlated w/
blood gas values to determine adequacy of ventilation
What is the normal minute volume in healthy adults
5 to 10 L/min
Low VE does not necessarily mean __________________ and high VE does not necessarily mean ________________ b/c not all breaths are created __________
hypoventilation;
hyperventilation;
equal
In the case of CO2 retention, Hyperventilation is not determined until….
ventilation is greater than what is needed to adequately remove excess CO2
Why must VE be correlated w/ blood gases
VE does not determine Hypo/hyperventilation (Remember the body will compensate for an increased or decreased CO2)
What is the criteria for hypoventilation?
- pH <7.35
- PCO2 > 45
What is the criteria for hyperventilation
- pH >7.45
- PCO2 <35
What are the 2 types of deadspace?
Anatomic
Alveolar
Air in the upper airways that does not participate in gas exchange is
Anatomic deadspace
Lung volumes that are ventilated but not perfused by capillary blood flow. Air trapped in the small airways (alveoli) that cannot participate in gas exchange
Alveolar deadpsace
The combination of the 2 deadspaces are called
Respiratory or Physiological Deadspace
How do we measure dead space?
Exhaled gas is collected over a specified interval and measured
What is Bohr’s equation
VD= (Paco-Peco2)/Paco2 x VT
Anatomic dead-space can be calculated as
1ml per pound or 2ml/kg of IBW
When can alveolar deadspace be calculated
During measurements of volumes
Alveolar ventilation is the part of ventilation that participates in
gas exchange at the alveolar level
What is the equation for VA
VA= (VT-VD) x RR
Dead space (VD) is considered equal to
anatomic dead space
(1 ml/lb or 2ml/kg of IBW)
_________ is the pressure generated at the ________ during the _______ 100 milliseconds of an _____________ effort against an _____________ airway
P100 (Occlusion pressure);
mouth;
first;
inspiratory;
occluded
What is the normal range for P100?
1.5 to 5 cm H2O
P100 is helpful in determining the effects of..
treatment in pts w/ abnormal vent responses
What is P100 measured with?
Closed-circuit
Tidal volume is defined as the volume of
air inspired or expired during a normal respiratory cycle
What is the equation the Vt?
Vt=VE/RR
If a pt is hypoxic but they have a good DLCO, what could cause that?
Hypoventilation
