Pulmonary Function and Physiology Flashcards
Infant PFT: Formula for R interruptor
Rint = Pmo/V
Pmo = mouth pressure V = tidal flow Rint = interrupter resistance
How many acceptable maneuvers needed for PFT?
minimum of 3
What is the largest difference between FEV1 or FVC allowed?
> 6yr: <0.150L
<6yr: <0.100L
Acceptability criteria for forced maneuvers (8)
1) Must have Best Expiratory Volume ≤ 5% of FVC or 0.100L (whichever is greater)
2) No evidence of faulty zero-flow setting
3) No cough in 1st second of expiration
4) No glottic closure within or after 1st second
5) Must achieve 1 of 3 End of Forced Expiration indicators
6) No evidence of obstructed mouthpiece
7) No evidence of leak
8) FIVC - FVC ≤0.100 or 5% of FVC
What is the Anaerobic Threshold?
The point above which lactate production exceeds removal
Change to anaerobic metabolism after anaerobic threshold
**At AT, VCO2 increases relative to VO2, changes the slope of the line
Indications for exercise test
- Evaluation of exercise tolerance
- Evaluation of undiagnosed exercise intolerance
- Evaluation of CV disease
- Evaluation of respiratory disease
- Specific clinical scenarios:
- Pre-op eval
- Exercise eval and pulmonary rehab
- Eval for impairment and disability
- Eval for transplant
Absolute contraindications for CPET
- Acute MI (3-5 days)
- Unstable angina
- Uncontrolled arrhythmias
- Syncope
- Endocarditis, Myocarditis, Pericarditis
- Heart failure
- Thrombosis of lower extremity
- Pulmonary edema
- RA desat <85%
- Respiratory Failure
Relative contraindications for CPET
- Left main coronary stenosis
- Moderate stenotic valvular heart disease
- Severe HTN
- Tachy/bradyarrhythmias
- Hypertrophic cardiomyopathy
- Pulmonary HTN
- Advanced or complicated pregnancy
- Electrolyte abnormalities
- Orthopedic impairment
Indications for Spirometry
1) Diagnosis
2) Monitoring
3) Disability/Impairment evaluation
4) Other
- Research
- Surveys
- Derivation of reference values
- Pre-employment
- Health assessment pre-physical activity
Relative contraindications for spirometry
1) Increase in myocardial demand or changes in BP (MI 1 week)
2) Increase in intracranial/intra-ocular pressure (Brain surgery 4 weeks, eye surgery 1 week)
3) Increase in sinus or middle ear pressures
4) Increase in intrathoracic and intra-abdominal pressure
5) Infection control
Indications for Methylcholine challenge
Help determine if current respiratory symptoms may be due to asthma or to make that diagnosis much less likely
Contraindications to methylcholine challenge
1) Airflow limitation (FEV1 <60%)
2) Spirometry quality
3) Cardiovascular problems
4) Cant perform any testing maneuvers properly
5) Pregnant/nursing mothers
6) Use of cholinesterase inhibitor medication
Medications to hold prior to skin testing
1) Anti-histamines (1st = 72 hours, 2nd = 7 days)
2) Topical steroids: 3 weeks
3) TCAs: 7-14 days
4) Benzos: 7 days
5) H2 blockers: 2 days
6) Omalizumab: 6 mos
7) Topical CNI: 7 days
No effect: short term PO steroids (1 week), leukotriene receptor antagonists
What is Aerobic threshold?
60% aerobic capacity + 70% max HR, 80% lactate threshold
Aerobic capacity = VO2 max (plateau where increased work but no change in oxygen uptake)
DLCO2 relative to VO2
VO2 = (HR x SV) x (CaO2 -CvO2)
DLO2 = VO2/AaDO2
What is the forced oscillation technique?
Application of an external pressure (small amplitude oscillations) signal superimposed on spontaneous breathing and measurement of the flow response of the respiratory system
Optimal frequency for forced oscillation technique?
4-8 Hz
Limiting factor for forced oscillation technique
- potential influence of upper airway compliance on respiratory system
- non-cooperation: refusal to use mouthpiece, inability to breathe without leak, difficulty breathing against oscillations
- wide range of health reference data
What is the respiratory exchange ratio?
Ratio of CO2 output to O2 consumption (VCO2/VO2)
Rest = 0.8-0.9
Increased exercise: increased carb utilization = larger fraction of metabolic fuel = increased R
Rapid rise after ventilatory threshold with increased VCO2, also increased after stopping exercise due to decreased VO2
What happens to end-tidal oxygen concentration during hyperventilation phase of exercise?
PETO2 remains relatively constant until the ventilatory threshold (AT) then it increases due to increase in minute and alveolar ventilation
What is the role for NO in the airways?
NO regulates vascular and bronchial tone (dilation), facilitates the coordinated beating of cilia and is a neurotransmitter for non-adrenergic and non-cholinergic neurons in the bronchial wall
Why is nasal NO increased in asthma?
Dual purpose:
1) relaxes bronchial smooth muscle and inhibits pro-inflammatory signaling events
2) can contribute to airway inflammation/injury through formation of toxic reactive nitrogen species
What is the amino acid precursor for NO?
What enzyme produces NO?
Amino acid: L-arginine
Enzyme: nitric oxide synthase
Advantages of allergy skin testing
- more sensitive
- rapid results
- able to visualize reaction
- wider variety of allergens