Lung Volume Concepts Flashcards
Ventilation
refers to the movement of air exchanged in the pulmonary system
What are the 3 major areas of Pulmonary Function Testing?
- Volumes and Capacity
- Gas Flow Rates
- Diffusion
What are the 4 primary Lung Volume Measurements?
- Tidal Volume - TV
- Inspiratory Reserve Volume - IRV
- Expiratory Reserve Volume - ERV
- Residual Volume - RV
Tidal Volume TV
of air that is inhaled and exhaled during normal resting breathing
Normal = approximately 400 mL
Inspiratory Reserve Volume (IRV)
the volume of air that can be forcefully inhaled following a tidal inspiration
Expiratory Reserve Volume (ERV)
the volume of air that can be forcefully expelled following a tidal expiration
Residual Volume (RV)
volume of air remaining in the lungs following a full or maximal expiration
Normal is around 30% of TLC
What are the 4 Primary Capacity Measurements of the Lung
- Total Lung Capacity (TLC)
- Vital Capacity (VC)
- Inspiratory Capacity (IC)
- Functional Residual Capacity (FRC) or Exp Cap (EC)
Total Lung Capacity
Total volume of gas in the lungs at the end of a maximal volitional inspiration
TLC = TV + IRV + ERV + RV
Vital Capacity
The maximum amount of gas that can be expired after a maximum inspiration
VC = IRV + TV + ERV
Inspiratory Capacity
The maximum amount of gas that can be inspired at the end of a tidal expiration
IC = TV + IRV
Functional Residual Capacity
The amount of gas remaining in the lungs after a normal quiet tidal expiration
FRC = ERV + RV
Tests of Gas Flow (7)
- Forced Vital Capacity (FVC)
- Forced Exp Volume in 1 second (FEV1)
- Forced mid-exp flow (FEF25-75)
- Maximum Voluntary Ventilation (MVV)
- Peak Expiratory Flow (PEF)
- Airway Resistance (Raw)
- Compliance (C)
Forced Expiratory Volume (FEV1)
volume of GAS FLOW that can be forcefully expelled in 1 second following a full inspiration.
- Normal = 75%
- Obstructive = 25%
- Restrictive = 83%
Forced Vital Capacity (FVC)
Measure of air flow that indicates the amount of air that is under volitional control (measures VC and Rate)
FVC = IRV + TV + ERV
PFT and Restricive Airway Disease
- Volume and Capacity Changes
- Gas Flow Rate Changes
- Examples of Disease
- Volume and Capacity Changes
- decreased TLC, FRC, RV, PaCO2
- Gas Flow Rate Changes
- decreased FVC
- NORMAL FEV1/FVC = 83%
- Reduced FVC in the absence of reduced FEV1/FVC ratio is hallmark of restrictive disease
- SMALL/NORMAL SHAPED FLOW RATE LOOP
- Examples of Disease
- auto immune = pulmonary fibrosis
- Neuro Musc = ALS, MS, Ms Dystrophy
- Obesity and Pregnancy
PFT and Obstructive Disease
- Volume and Capacity Changes
- Gas Flow Rate Changes
- Examples of Disease
- Volume and Capacity Changes
- increased TLC ~165%
- increased RV ~50-70% excess
- increased FRC
- increased PaCO2
- Gas Flow Rate Changes
- **decreased FEV1 **
- Normal FVC
- decreased FEV1/FVC = 25%
- disproportionate decrease in FEV1 to FVC and resultant FEV1/FVC ratio is hallmark
- SCOOPED FLOW CHART
- Examples of Disease
- asthma
- bronchitis
- Cystic fibrosis
- bronchiectasis
- pneumonia
- alpha 1 -tripsin deficiency
Severity of Reduction in FVC and or FEV1
Normal >80%
Mild - 70-79%
Moderate - 60-69%
Mod-Severe - 50-50%
Severe - 35-49%
Very Severe <35%
Changes of Pulmonary Function Tests based on Severity of Impairment
FEV1/FVC
normal >70%
mild: 60-70
moderate: 45-59
severe: <45
Normal Diffusion and Reasons for Reduction
- Normal Diffusion = 25-30 mL/min/mmHg
- Reasons for reduction =
- low Hct
- thickened alveolar membrane
- decreased alveolar surface area