Lung volumes capacities
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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

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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.


Normal fev1 fvc curve

Normal FEV1, FVC Curve


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%


Flow volume loops

Flow Volume Loops


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


Thank you

Thank you


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