15 Pulmonary mechanics ad spirometry Flashcards
Inspiratory capacity
from tidal exhalation to maximal inspiration
Inspiratory reserve
From max tidal to maximal inspiration
Vital capacty
Maximal inspiration to maximal expiration
FRC
Whats left in the lung after tidal expiration
Expiratory reserve
tidal expiration to full expiration
Determinants of lung flow
flow = (pAlv-pAtm)/ airway resistance)
Remember resistance changes at different parts of lung and varies with level of inflation (more inflation = less resistance
Resistance across lung
Highest at medium sized bronchi, almost nonexistent in alveoli
PFT indication
- Diagnostic: Symptoms, signs, abnormal lab results
- Assess effects of disease
- screenings- smokers, occupatinal exposures, preoperative rsk, disability, prognosis
FEV1
How much volume in first second of expiration
forced vital capacity
Full amount able to blow out given all the time in the world
Intrathoracic Vs extrathoracic
Expiration assess intrathoracic
inspiration assess extrathoracic
Obtructive pulmonary disease Flow volume curve
- slower rise to peak
- Lower expiratoryflow
- scalloping of curve from slowing effect on restricted lower airways
Resttrictive disease flow/volume curve
Less volume, skinnier curve, fast expiration, no scalloping
Lung cancer curve
cant gert a peak flow- no scalloping
How to tell id there is restrictiveor obstructive process
look at FEV1/FVC ratio
- Normal (100% of predicted) is either normal or restrictive
- Low ratio indicates obstructive prcess
Normal spirometry
*FEV1/FVC is normal
and
*VC is normal 80% or greater of predicted.
Obstrucive FEV1 grading in low FEV1/FVC
FEV1 >99 - physiologic 70-99 Mild 60-69 Moderate 50-59 moderrate/severe 34-49 Sever <34 very severe
Bronchodilator response criteria
FVC or FEV1 increases 12% and 200mls
Obstructive pulmonary diseases
Tumors and FB in large airwaus
Asthma, chronic bronchitis, CF in pepheral airways
Emphysema in parenchyma
Restrictive disease
Sarcoidosis,collagen vasc diseas, pulmonary fibrosis pneumonectomy Pleural effusion Kyphosis and NMJ disorders Obesity
Restrictive defect criteria
Normal FEV1/FVC and DCR. FVC
Reduced TLC
70% to lower limit normal - mild
60-69% mild restrictivve defect
<60% moderately severe
Accepttability/repeatablility
Acceptability:
- No artifacts
- PEF reached with <5% of volume or less than .15L, and in less than 120ms
Repeatability:
Two largest FVC within .2L?
Same with FEV1s?
test up to 8 times, keep top 3
