Lung Volumes Lung Capacities PFT Spirometry Dead Space Anatomical Dead Space Physiological Dead Space

2. LUNG VOLUMES
The Lung Volumes are measured (using a Spirometry)
The various Lung Volumes are as follows :
Tidal Volume (VT )
Residual Volume (RV)
Expiratory Reserve Volume (ERV)
Inspiratory Reserve Volume (IRV)
Forced Expiratory Volume in 1sec (FEV1)

3. TIDAL VOLUME (VT)
• The Volume of air inspired or expired with each Normal Breath
• It is about 6 to 8 ml/kg
• Average in a healthy Adult Male – 500ml
• Average in a healthy Adult Female – 400ml
• It decreases with Decreased Lung Compliance or when patient has Reduced Ventilatory Muscle Strength

4. INSPIRATORY RESERVE VOLUME (IRV)
• The Extra Volume of air that can be Inspired over and above the normal Tidal Volume when the person inspires with full force
• Average in a healthy Adult Male – 3000ml
• Average in a healthy Adult Female – 1900ml

5. EXPIRATORY RESERVE VOLUME (ERV)
• The Maximum Extra Volume of air that can be Expired by forceful expiration after the end of Normal Tidal expiration
• Average in a healthy Adult Male – 1100ml
• Average in a healthy Adult Female – 700ml

6. RESIDUAL VOLUME (RV)
• The Volume of air Remaining in the Lungs after the most Forceful Expiration
• Average in a healthy Adult Male – 1200ml
• Average in a healthy Adult Female – 1100ml

7. FORCED EXPIRATORY VOLUME IN 1SEC (FEV1)
• The Volume of air that can be Exhaled in 1 Second with Maximal effort from the point of Maximal Inspiration
• It is Decreased in both Obstructive and Restrictive Lung Diseases
• Normal FEV1 is about ¾ of FVC

8. LUNG CAPACITIES
The Lung Capacities are Calculated as the Sum of Specific Lung Volumes
The various Lung Capacities are as follows :
Inspiratory Capacity (IC)
Functional Residual Capacity (FRC)
Vital Capacity (VC)
Total Lung Capacity (TLC)
Forced Vital Capacity (FVC)

9. INSPIRATORY CAPACITY (IC)
• This capacity is the Amount of air that a person can Breath in, Beginning at the normal expiratory level and distending the Lungs to
maximum amount
• Average in a healthy Adult Male – 3500ml
• Average in a healthy Adult Female – 2400ml
• IC = TV + IRV
• This can Detect Extrathoracic Airway Obstruction (IC will be Decreased)

10. FUNCTIONAL RESIDUAL CAPACITY (FRC)
• This capacity is the amount of air that Remains in the Lungs at the end of Normal Expiration
• Average in a healthy Adult Male – 2300ml
• Average in a healthy Adult Female – 1800ml
• FRC = ERV + RV
• FRC is the Resting Expiratory Volume of Lung and is the Primary Determinant of Oxygen Reserve in Humans when Apnea occurs
• It is also Used to Quantify the Degree of Pulmonary Restriction

11. VITAL CAPACITY (VC)
• This Capacity is the Maximum of air a person can expel from the Lungs after first filling the Lungs to their Maximum extent and then
Expiring to the Maximum extent
• Average in a healthy Adult Male – 4600ml
• Average in a healthy Adult Female – 3100ml
• VC = IRV + TV + ERV
• It is Decreased by Restrictive Lung Disease (Pulmonary edema/Atelectasis/Pleural Effusion/ Pneumothorax/Pregnancy/Ventilatory Muscle
Waekness)

12. TOTAL LUNG CAPACITY (TLC)
• The Maximum Volume to which the Lungs can be Expanded with the Greatest Possible Effort
• Average in a healthy Adult Male – 5800ml
• Average in a healthy Adult Female – 4200ml
• TLC = IRV + TV + ERV + RV

13. FORCED VITAL CAPACITY (FVC)
• The Volume of air that can be exhaled with maximal effort from TLC
• Normally it is equal to Vital Capacity
• May be Reduced in Chronic Obstructive Diseases
• Always Reduced in Restrictive Diseases

15. • The Various Pulmonary Function tests Used To determine the Lung Volumes and Capacities are :
• Spirometry
• Body Plethysmography

17. • Some of the Air a person breaths never reaches the gas exchange areas but simply fills Respiratory passages (Nose, Pharynx, Trachea)
where gas exchange does not occur
• This is called DEAD SPACE Air because it is not useful for Gas Exchange
• On expiration, the gas in the Dead space is expired first
• VE = VA + VD
• VE = Minute Ventilation
• VA = Alveolar Ventilation
• VD = Dead Space Ventilation

18. MEASUREMENT
• The Subject takes deep breath of 100% O2, which fills entire Dead Space with pure O2
• Then expires through a rapidly recording nitrogen meter, Which makes the graph
• Early part – only O2 / Nitrogen is 0
• Alveolar Air – Rise in Nitrogen rapidly
• Gray area – No Nitrogen – Volume of Dead Space
• Normal Dead Space Volume in Young Men – 150ml