Lung Capacities and Volume.

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Lung Volumes and Capacities
Recording Changes in Pulmonary
Volume—Spirometry
Spirometer is an instrument which records the volume movement of air into and out of the lungs.

Lung volumes
Tidal volume
Inspiratory reserve volume
Expiratory reserve volume
Residual volume

Lung capacities
Inspiratory capacity
Functional residual capacity
Vital capacity
Total lung capacity
Lung volumes

1. Tidal volume
 The tidal volume is the volume of air inspired or expired with each normal breath.
it amounts to about 500 milliliters.
Lung volumes
2. Inspiratory Reserve Volume
The inspiratory reserve volume is the extra volume of air that can be inspired forcefully over and above the normal tidal volume.
Amount= 3000ml.
Lung volumes
3. Expiratory Reserve Volume
The expiratory reserve volume is the maximum extra volume of air that can be expired by forceful expiration after the end of a normal tidal expiration.
Amount= 1100ml.
Lung volumes
4. Residual volumes
The residual volume is the volume of air remaining in the lungs after the most forceful expiration.
Amount= 1200ml.
Lung Capacities
1. Inspiratory Capacity
It is the amount of air which can be inspired by maximum effort after a normal expiration.
It is the amount which is equal to IRV+ TV= 2500-3500ml.
Lung capacities
2. Total lung capacity (TLC)
It is the maximum amount of air that is contained in the lungs after maximum inspiration.
TLC= RV + ERV + TV + IRV= 5.5liters.
Lung Capacities
3. Vital Capacity
It is the amount of air that can be breathed out by maximum expiration after a maximum inspiration.
Value:
In males= 4-5 liters
In females= 3-4 liters.
Vital capacity shows the strength of the respiratory muscles.
Factors influencing vital capacity
Age
Sex
Body size
Posture
Physical training
Dynamic Lung Volume and Capacities
Timed Vital Capacity (TVC) or Forced Vital Capacity (FVC)
Minute Ventilation (MV) or Pulmonary Ventilation (PV)
Peak Expiratory Flow Rate (PEFR)
Maximum Breathing Capacity or Maximum Voluntary Ventilation (MVV)
Dynamic Lung Volume and Capacities
Timed Vital Capacity (TVC) or Forced Vital Capacity (FVC)
FVC is the maximum volume of air which can be breathed out as forcefully and “rapidly” as possible following a maximum inspiration.
Components of FVC:
  1. FEV1 (Forced Expiratory Volume in 1 sec of exhalation. Normal:       80% of FVC.
  2. FEV2 (Forced Expiratory Volume in 2 sec of exhalation. Normal: 95% of FVC.
  3. FEV3 (Forced Expiratory Volume in 3 sec of exhalation. Normal: 98-100% of FVC.
In restrictive lung disorders, VC decreases while FEV1 is normal.
In obstructive lung disorder, VC is less than normal while FEV1 decreases.
Dynamic Lung Volume and Capacities
Minute Ventilation (MV) or Pulmonary Ventilation (PV)- The volume of air expired or inspired by the lungs in one minute.
Peak Expiratory Flow Rate (PEFR)- the expiratory flow rate during the peak of FVC. Normal: 400-450L/min
Maximum Breathing Capacity or Maximum Voluntary Ventilation (MVV) – the largest volume of air that can be moved into and out of the lungs in one minute by maximum voluntary effort. Normal: 90-170L/min
Alveolar Ventilation
The amount of air ventilating the alveoli per minute.
Alveolar ventilation =(Tidal volume-Dead space) X Respiratory rate
So, AV= (500-150)ml X 12
AV= 4.2liter/min
•       Dead Space- the amount of air in the respiratory passage which does not take part in exchange of gases. It is of two types:
•       Anatomical dead space
•       Physiological dead space

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