Lung volumes and Capacities

 Breathing (inspiration and expiration) occurs in
a cyclical manner due to the movements of the
chest wall and the lungs. The resulting changes
in pressure causes changes in lung volumes,
i.e.. the amount of air the lungs are capable of
occupying.
 These volumes tend to vary depending on the
depth of respiration, ethnicity, gender, age and
in certain respiratory diseases.

 It refers to the volume of air associated with
different phases of the respiratory cycle.
 Lung volumes are measured independently
whereas lung capacities are inferred from
lung volumes.

There are four types of lung volumes :
 Tidal Volume
 Inspiratory Reserve Volume
 Expiratory Reserve Volume
 Residual Volume

 It represents the normal volume of air
displaced between inhalation and exhalation
wherein extra effort is not applied.
 Normal value: 500ml per inspiration

 The maximum amount of additional air that
can be drawn into the lungs by a determined
effort after normal inspiration.
 Normal value: 3,100 ml(M)
1,900ml(F)

 The additional amount of air that can be
expired from the lungs by determined effort
after normal expiration.
 Normal value : 1,200 ml(M)
700 ml(F)

 The volume of air still remaining in the lungs
after the most forcible expiration possible.
 Normal value : 1,200 ml(M)
1,100ml (F)

 These are combinations of two or more lung
volumes.
Types :
 Inspiratory Capacity(IC)
 Expiratory Capacity(EC)
 Vital Capacity(VC)
 Functional Residual Capacity(FRC)
 Total Lung Capacity(TLC)

 The volume of gas that can be taken into the
lungs in a full inhalation, starting from the resting
inspiratory position; equal to the tidal volume
plus the inspiratory reserve volume.
 IC = TV + IRV
 Normal values : 3,600ml (M)
2,400ml (F)

 Total volume of air a person can expire after
a normal inspiration. This includes tidal
volume and expiratory reserve volume.
 EC = TV+ ERV.
 Normal value :1,700ml (M)
1,200ml (F)

 It is the maximum amount of air that can be
expelled out forcefully after deepest possible
inspiration.
 It includes inspiratory reserve volume,tidal
volume and expiratory reserve volume.
 VC = TV + IRV + ERV
 Normal value: 4,800ml (M)
3,100ml (F)

Physiological variations:
1. Gender – Females <Males.
2. Body built – It is more in heavily built persons.
3. Posture – More in standing and less in lying.
4. Athletes – More than average people.
5. Occupation – Less in sedentary jobs, more in
people who play musical wind instruments like
flute.

Pathological variations:
1. Asthma
2. Emphysema
3. Weakness or paralysis of respiratory muscles.
4. Pulmonary congestion
5. Pneumonia
6. Haemothorax
7. Pyothorax
8. Hydrothorax
9. Pulmonary oedema
10. Pulmonary tuberculosis

 It is the volume of air that can be exhaled
forcefully and rapidly after a maximal or deep
inspiration.
 It is a dynamic lung capacity.
 Normally FVC= VC. However it may
decrease due to some pulmonary diseases.

 It is the volume of air that can be expired
forcefully in a given unit of time.
 FEV1 = Volume of air expired forcefully in 1
second.
seconds.
seconds.

 FEV1 = 83% of total vital capacity

FEV has great diagnostic value:
 It is significantly decreased in obstructive
diseases like Asthma.
 It is slightly reduced in some restrictive
respiratory diseases like Fibrosis of lungs.

 Functional Residual Capacity (FRC) refers to
the volume of air left in the lungs after
a normal, passive exhalation. It is mainly
determined by the balance between the elastic
forces of the lung and chest wall.
 It includes Expiratory reserve volume and
Residual volume.
 FRC = ERV+RV
1,800ml (F)

 It is the volume of air present in lungs after a
deep(MAX)inspiration.
 TLC = IRV + TV + ERV + RV
4,200ml (F)

 It is the volume of air breathed in and out of
lungs every minute.
 It is the product of tidal volume and respiratory
rate.
 RMV = TV * RR
= 500 * 12 = 6,000ml (normal)
Variations :
• It increases in physiological conditions like
voluntary hyperventilation, exercise.
• It is reduced in respiratory diseases.

 It is the maximum volume of air that can be
breathed in and out of lungs by forceful
respiration (hyperventilation) per minute.
 It is a dynamic lung capacity and is reduced
in respiratory diseases.
 Normal value (Adult): Male:150-170L/min
Female:80-100 L/min
 Measurement: Respirometer

 It is the maximum rate at which the air can be expired
after a deep inspiration.
 Normal value: 400L/min
 Measurement: Wright peak flow meter
Significance:
• It can be useful in assessing and differentiating
respiratory diseases(i.e.. Obstructive and Restrictive)
• Reduction is more in obstructive than restrictive.
• In restrictive diseases PEFR = 200L/min
• In obstructive diseases PEFR = 100L/min

• Spirometer
• Respirometer
• Plethysmograph
• Wright Peak Flow Meter

Restrictive Respiratory Diseases:
It is an abnormal respiratory condition
characterized by difficulty in inspiration.
Expiration is not affected.
RRD may be because of abnormality of
lungs,thoracic cavity and/or nervous system.

 It is an abnormal respiratory condition
characterized by difficulty in expiration.

Disease:
• Poliomyelitis
• Myasthenia Gravis
• Flail chest(broken ribs)
• Paralysis of diaphragm
• Spinal cord disease
• Pleural effusion
Structures involved:
• CNS
• CNS and thoracic cavity
• Thoracic cavity
• CNS
• CNS
• Thoracic cavity

 Disease :
• Asthma.
• Chronic bronchitis.
• Emphysema
• Cystic fibrosis
 Laryngotracheobronchiti
s(Croup)
 Tumors
 Severe cough and cold
with phlegm
 Structures involved :
• Lower respiratory tract.
 Upper respiratory tract.

Lung volumes and Capacities

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