Resp. 3. Compliance

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Compliance Of Lung And Thorax:

Compliance Of Lung And Thorax Husan Bano Associate Professor Department Physiology Al-Tibri Medical College Isra University Karachi Campus

Learning Objectives :

Learning Objectives At the end of this lecture you should be able to: 1. know the significance of intra-alveolar, intrapleural and trans-pulmonary pressure in process of respiration. 2. define the compliance of lung and thorax . 3. explain the factors affecting on compliance of lung and thorax


REVIEW OF PULMONARY PRESSURES Intra-alveolar pressure Intra-pleural pressure 3. Trans-pulmonary pressure


REVIEW OF PULMONARY PRESSURES Definition: Pressure inside the alveoli. During normal quiet inspiration= -1mmHg During normal quiet expiration= +1mmHg with respect of atmospheric pressure 1. Intra-alveolar Pressure


REVIEW OF PULMONARY PRESSURES Difinitation: Pressure inside the pleural space. 2 . Intra-pleural pressure resting state of lungs = - 5cm H2O During normal quiet inspiration = - 7.5 cmH2O In expiration goes back = - 5cmH2O Also called recoil pressure

Why intra-plural pressure is called “Recoil Pressure”:

Why intra-plural pressure is called “Recoil Pressure” Recoil pressure means the pressure which is required for the contraction of lung or expiration. Resting - 5 CmH2O Inspiration - 7.5 CmH2O Expiration - 5 CmH2O

3. Trans-pulmonary Pressure:

3. Trans-pulmonary Pressure Trans-pulmonary pressure is the pressure difference between inside and outside of the lungs. It is difference between intra-alveolar and intra-pleural pressure It determines the degree of inflation of the lungs.


COMPLIANCE OF LUNG AND THROAX During inspiration, the lung expanded which expand the thoracic cavity. The expansibility of lungs and thorax is called compliance.


Compliance It is expressed as that “the volume of air in the lungs increases with each unit increase in intra-alveolar/intra-pleural pressure. - 1mmHg -2mmHg - 3mmHg 110 ml air 220 ml air 330 ml air


Compliance The compliance of normal lungs and thorax together is about 110 ml/cmH2O pressure. It means that every time when alveolar pressure increase by 1cm of H2O , the lungs expanded 11o ml .


Compliance Compliance in the lungs is defined as a change in volume divided by a change in trans-pulmonary pressure CL = ΔV / ΔPL. The compliance of lung alone is 200 ml/cm H20 . Lung compliance is higher at the base of the lung and lower at the apex of the lung.

Compliance Diagram:

Compliance Diagram

Factors That Causes Abnormal Compliance:

Factors That Causes Abnormal Compliance Any disease which destroy the lung tissues causes decrease lung compliance. eg Cancer of lung ( Lung of smoker ) Tuberculosis of lung Fibrosis of lung

Factors That Causes Abnormal Compliance:

Factors That Causes Abnormal Compliance 2. Any disease which depress the rib cage, causes the decrease lung compliance. eg 4. Excessive round back 3. scoliosis 1. Fibrosis of respiratory muscle 2. Paralysis of respiratory muscle

Work of Breathing:

Work of Breathing Inspiration is an active process which requires energy. This energy is utilized in performing the 3 different types of work. Compliance work Tissue resistance work. Airway resistance work.

Work of Breathing:

Work of Breathing In pulmonary diseases, all 3 types of work increases. e.g. Compliance work and Tissue resistance work increases in fibrosis of lung , Airway resistance work increases in all air way obstructed diseases. During expiration no such work performed because expiration is passive process.

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