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LUNG VOLUMES & CAPACITIES. Lecture-3 Dr.Zahoor Ali Shaikh. Lung Volumes. Tidal Volume [TV] It is volume of air we breathe in or breathe out during normal single breath. It is about 500ml. Inspiratory Reserve Volume [IRV]

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lung volumes capacities

LUNG VOLUMES & CAPACITIES

Lecture-3

Dr.Zahoor Ali Shaikh

lung volumes
Lung Volumes
  • Tidal Volume [TV]

It is volume of air we breathe in or breathe out during normal single breath. It is about 500ml.

  • Inspiratory Reserve Volume [IRV]
  • It is volume of air that can be breathed in [inspired] forcefully, over and above normal tidal volume.
  • IRV is about 3000ml.
  • It is done by maximal contraction of diaphragm, external inter-costal muscles and accessory muscles of inspiration.
lung volumes1
Lung Volumes
  • Expiratory Reserve Volume [ERV]
  • It is maximum volume of air that can be expired forcefully after normal tidal expiration.
  • ERV is about 1000ml.
  • It is done by contracting the accessory expiratory muscles of expiration [abdominal and internal-intercostal muscles].
lung volumes2
Lung Volumes
  • Residual Volume ( RV )
  • It is volume of air remaining in the lungs after maximal expiration.
  • RV is about 1200ml.
lung capacities
Lung Capacities
  • Inspiratory Capacity [IC]
  • It is maximum volume of air that can be inspired after normal tidal expiration.
  • It includes tidal volume and inspiratory reserve volume.
  • (IC = IRV + TV)
  • It is about 3500ml.
lung capacities1
Lung Capacities
  • Functional Residual Capacity [FRC]
  • It is volume of air that remains in the lungs after normal tidal expiration.
  • (FRC = ERV + RV)
  • Average value FRC = 2200ml.
lung capacities2
Lung Capacities
  • Vital Capacity [VC]
  • It is maximum volume of air that can be expired forcefully after taking maximum inspiration [during a single breath].
  • (VC = IRV + TV + ERV)
  • Average value VC = 4500ml.
lung capacities3
Lung Capacities
  • Total Lung Capacity [TLC]
  • It is the maximum volume of air that the lungs can hold.
  • (TLC = TV + IRV + ERV + RV)
  • Average volume TLC = 5700ml [5.5-6 liter].
  • TLC is affected by Age, Build, Height and Weight, and presence of Lung disease.
forced expiratory volume in one second fev1
Forced Expiratory Volume In One Second [FEV1]
  • Forced Expiratory Volume
  • It is volume of air that can be expired forcefully during the first second of expiration [normally we expire in 3sec].
  • FEV1 = 80% [80% of vital capacity(VC)]
  • FEV2 = 92%
  • FEV3 = 99%
  • FEV1 indicates maximal air flow rate from the lungs.
  • FEV1 is decreased in obstructive lung disease e.g. bronchial asthma.
respiratory diseases
Respiratory Diseases
  • Obstructive Lung Disease e.g. bronchial asthma.
  • Restrictive Lung Disease e.g. pulmonary fibrosis.
  • Obstructive Lung Disease
  • Patient has difficulty in expiration [due to obstruction of bronchi].
  • Therefore, FEV1 and FEV1% is decreased.
  • Example: Normal VC = 5 liters, FEV1 = 4 liters.
  • FEV1% = (FEV1/FVC) * 100

= (4/5) * 100

= 80%

  • In Obstructive Lung Disease, VC = 4 liters, FEV1 = 2 liters
  • FEV1% = (2/4)*100

= 50%

respiratory diseases1
Respiratory Diseases
  • Restricted Lung Disease
  • Lungs are smaller than normal, therefore, vital capacity[VC], TLC, all are decreased as lungs can not expand.
  • When we do respiratory function test:
  • FEV1 is decreased, FVC is also decreased but FEV1% is normal [80% or more].
  • Example: Normal VC = 5 liters, FEV1 = 4 liters.
  • FEV1% = (FEV1/FVC) * 100

= (4/5) * 100

= 80%

  • In Restricted Lung Disease, VC = 3 liters, FEV1 = 2.7 liters
  • FEV1% = (2.7/3)*100

= 90%

pulmonary ventilation alveolar ventilation
Pulmonary Ventilation & Alveolar Ventilation
  • Pulmonary Ventilation or Minute Ventilation
  • It is volume of air we breathe in and out in 1min.
  • Pulmonary Ventilation

= Tidal Volume * Respiratory rate

= 500ml * 12= 6000ml or 6 liter

  • Normal respiratory rate is 12 -18/min.
  • Adult young person can increase pulmonary ventilation 25-fold to 150 liters/min [to increase pulmonary ventilation one has to increase tidal volume and respiratory rate].
anatomic dead space
Anatomic Dead Space
  • As we breath in, all air does not go to alveoli for gas exchange but some of the air remains in trachea and bronchi [conducting zone] and does not take part in gas exchange.
  • It is 150ml. It is called ‘Anatomic Dead Space’.
  • As our tidal volume is 500ml, anatomic dead space is 150ml, therefore, 350ml goes to lungs for gas exchange.
alveolar ventilation
Alveolar Ventilation
  • It is volume of air reaching the alveoli/min.
  • It is more important than pulmonary ventilation.
  • It is alveolar air that takes part in gas exchange.
  • Alveolar Ventilation

= TV – Dead Space * Respiratory Rate[RR]

= (500 – 150) * 12

= 350 * 12 = 4200 ml/min

  • Alveolar Ventilation is less than Pulmonary Ventilation.
effect of breathing pattern on alveolar ventilation
Effect of Breathing Pattern on Alveolar Ventilation
  • Rapid shallow breathing is not good, as TV is decreased and most of the air is lost in dead space and little or no air goes to alveoli.
  • Person may get unconscious within few minutes.
alveolar dead space
Alveolar Dead Space
  • Normally air going into the alveoli, takes part in gas exchange, therefore, there is no alveolar dead space in healthy person.
  • In case of disease, where alveoli are abnormal e.g. pneumonia, gas exchange does not take place in affected alveoli, therefore, alveolar dead space is there.
  • Physiological Dead Space

= Anatomical Dead Space + Alveolar Dead Space

dead space
Dead Space
  • In Health,

Physiological dead space=Anatomical dead

space

[As all alveoli are functioning].

  • In Disease,

Physiological dead space is more than Anatomical dead space

[As many alveoli are not functioning].

ventilation and perfusion in the lungs
Ventilation and Perfusion in the Lungs
  • Regional difference exist at the top and bottom [apex and base] of the lung due to gravitational effect.
  • Standing upright
  • Gravity effect is more on blood flow than on airflow.
  • Effect on Ventilation/Perfusion ratio.
ventilation and perfusion in the lungs1
Ventilation and Perfusion in the Lungs
  • Top of the lung receives relatively more air than blood, therefore, ventilation perfusion ratio is increased.
  • Bottom of the lung receives relatively less air than blood, therefore, ventilation perfusion ratio is decreased.
important points
Important Points
  • During normal breathing, lungs are not totally full nor totally deflated.
  • At the end of normal quiet expiration, the lungs contain about 2200 ml of air.
  • Lungs can never be completely emptied therefore gas exchange can take place after forceful expiration.
what you should know from this lecture
What You Should Know From This Lecture
  • Lung volumes – TV, IRV, ERV, RV
  • Lung capacities – IC, FRC, VC, TLC
  • FEV1, FEV1% and their importance in Obstructive and Restrictive Lung Disease
  • Alveolar Ventilation & Pulmonary Ventilation
  • Anatomic Dead Space
  • Physiological Dead Space
  • Ventilation Perfusion at the Apex and baseof the lung
ad