Pulmonary Compliance and Work of Breathing SAQ PDF

Pulmonary compliance and work SAQ of breathing By: Dr. Mona Mohamed Ahmed Assistant Professor of physiology Ibn-Sina National College [email protected]  LLOs 1. Define lung compliance and its normal value....

Pulmonary compliance and work SAQ of breathing By: Dr. Mona Mohamed Ahmed Assistant Professor of physiology Ibn-Sina National College [email protected]  LLOs 1. Define lung compliance and its normal value. 2. Differentiate factors affecting At the end of this the lung compliance. lecture, you should 3. Outline different component of be able to: work of breathing. 4. Differentiate causes of increased work of breathing  Pulmonary Compliance Any distensible organ has got a compliance V Gisfftional Compliance e.g: urinary bladder and blood vessels ❏ Compliance measures the distensibility AP ftp Yonal Complaince ❏ Compliance is the change in volume (V) per unit change in pressure (P) C = ∆V / ∆P. P= Transmural pressure (distending pressure= IAP– IPP). normal valuesof complaiance NL values: mlfoulomwater a) Lungs 0 or chest wall alone = 200 ml/cm H2O pressure. b) Combined lung and thorax= 100 ml/cm H2O pressure  Dynamic lung pressure-volume curve during single normal tidal volume: WIT Is Shows hysteresis loop. 9S static Hysteresis= The lung (V) does NOT change in response to (P) change in same way Inspiration Expiration dynamic during inflation and deflation. Expiration In deflation, the surfactant concentration bb increases, leading to decreasing the surfaceBg tension and therefore a higher compliancewh Trans munal pressure  Factors affecting compliance: 1. Factors in the lung: Compliance is affected by: a) Elastic forces (recoil tendency) of the lung b)Surface tension of the fluid lining the alveoli volume Therefore,…Lung compliance decreased in 1. In Restrictive lung diseases as in pulmonary congestion, fibrosis and edema, lung become stiffer and more difficult to inflate 2. Decreased surfactant (due to increased ++ surface tension)  volume ⮚Lung compliance 99 increased in: 1. Old age. 2. Emphysema rupture due to: Elastic fibers decreased recoil tendency  2. Factors in the chest wall: Compliance is decreased in: 1. Thoracic cage deformities as kyphosis (Forword) and scoliosis (sideward) 2. Obesity. mw swim Jw 3. Arthritis, poliomyelitis, myositis While Compliance is increased in: 1- Athletes WORK OF BREATHING Work of breathing definition ⮚Def: it is the work or effort done by respiratory muscles to overcome resistance in thorax and respiratory tract (to move air in and out of the lung) ⮚During normal respiration: work is done only during inspiration (respiratory muscles contraction), but expiration is entirely EE a passive process. ⮚At rest, work of breathing is about 1-2% of the total body energy expenditure. ⮚At heavy exercise, work is only about 3-5% of the total energy expenditure of the body.  Work of breathing can be divided into: mm 1. Compliance work 2. Tissue resistance work 3. Airway resistance work  Compliance work Tissue resistance Airway def work resistance work It is the work required to It is the work required to It is the work required to expand the lung against its overcome the resistance of overcome airway resistance a e elastic force (recoil tendency) non-elastic tissue of the lungs and thoracic cage during the movement of air into the lung. 65% of total work of breathing 7% of total work 28% of total work Increased in: Increased innarrowairway 0 Decreased surfactant × bronchiolar constriction 0 pulmonary congestion e.g: Bronchial asthma 0 pulmonary fibrosis 0 pulmonary edema 0 Thoracic cage deformities kyphosis scoliosis  volume Factors affecting airway Resistance: Radius Esther 1. lung volume: 8mm ⮚The bronchi are supported by radial traction of the surrounding lung tissues (elastic fibers). So… ▪ At high lung volume, the diameter of 0 is increased. resistance 9 bronchi ▪ At low lung volume, the diameter of bronchi is decreased. resistance  diameter 2. Airway radius and number: Inversely proportional failsto the powerof four ⮚Airway resistance α 1/r4 radius 511998 So, If the radius of bronchi decreases from 1mm to 0.5 mm →→ resistance increases 16 times a  Airway number: The greater number of airways the less resistance?? because there are more paths for the air to flow into. Less radius= higher resistance. More number = less resistance.  Question: Which have more resistance, bronchi or terminal bronchioles? Medijyoms.is Radius Radius But But number my L resistance So resistance ANSWER: ✔A: Bronchi. Radius the terminal bronchioles are the smallest airway (in terms of radius),but their high number compared to the larger airways, makes it less resistance. or mediumsized SO, the bronchi actually have greater resistance because there are less so number of them compared to the terminal bronchioles. 1 Most resistance to air flow occurs in medium sized bronchi It  Factors affecting Diameter of bronchi: MCQReceptor Bronchodilation Bronchoconstriction an (decreases e resistance) (increases on resistance) 1. Sympathetic nervous system 1. Parasympathetic nervous system - Releases noradrenaline - Releases acetylcholine - Acts on bronchial muscles via Beta-2 - Acts on bronchial muscles via muscarinic adrenergic receptors receptors 2. Adrenal medulla secrete adrenaline and noradrenaline that reach bronchial muscles through the blood - Both adrenaline and noradrenaline act on Beta-2 adrenergic receptors  Bronchodilatation Bronchoconstriction 2. Histamine (via H-1 receptors) 3. Leukotrienes(via Leukotriene receptors) Both are Released during allergic conditions (bronchial asthma ). Inspired warm air 4. Inspired Cold air increased PCO2 in small airway 5. Decreased PCO2 in small airway 6. Bronchial irritation by dust and gases  Summary of compliance  Compliance is the change in volume (V) per unit change in pressure (P) = Lungs or chest wall alone = 200 ml/cm H2O pressure. 0 0 = Combined lung and thorax= 100 ml/cm H2O pressure  It shows hysteresis loop (During deflation, there is higher compliance).  Compliance decreased in: 1. Pulmonary causes: congestion, fibrosis and edema, and causes of surfactant deficiency 2. Chest wall causes: Thoracic cage deformities, Arthritis, poliomyelitis & myositis ⮚Compliance increased in: 1. Old age and emphysema 2. Athletes  Summary of work of breathing Def: it is the work done by respiratory muscles to overcome resistance in thorax and respiratory tract (to move air in and out of the lung). Increased in: 1. Causes of decreased compliance (increased compliance work) 1. Decreased surfactant 2. pulmonary congestion 3. pulmonary fibrosis 4. pulmonary edema 5. Thoracic cage deformities 2. Causes of bronchoconstriction (increased airway resistance work) Factors affecting airway Resistance: 1- lung volumes 2- Airway radius and number N.B: Most resistance to air flow occurs in medium sized bronchi THANK YOU.