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Respiratory Block Physiology 439 Team Work

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Respiratory Block Physiology 439 Team Work Mechanics of pulmonary ventilation Respiratory Block Physiology 439 team work •Black: in male / female slides •Red : important Editing file •Pink: in female slides only •Blue: in male slides only •Green: notes @physiology439 •Gray: extra information •Textbook: Guyton + Linda Objectives : List the muscles of respiration and describe their roles during inspiration 01 and expiration Identify the importance of the following pressure in respiration: atmospheric, 02 intra-alveolar, intrapleural and transpulmonary Explain why intrapleural pressure is always subatmospheric under normal 03 conditions, and the significance of the thin layer of the intrapleural fluid surrounding the lung Define lung compliance and list the determinants of compliance 04 Mechanics of breathing Air movement depends upon : Boyle’s Law: Pulmonary Ventilation : the Volume depends on physical movement of air into PxV=K 1 2 P1xV1=P2xV2 3 movement of diaphragm and out of the lungs and ribs P= pressure , V= volume, K= constant Respiratory muscles Inspiratory muscle Expiratory muscle It is a passive process that depends on During resting Diaphragm and external intercostal the recoil tendency of the lung and need no muscle contraction Accessory muscles e.g It is an active process and need muscles Sternomastoid, anterior serratus, scalene During forced contraction the abdominal muscles and muscles contract in addition to the the internal intercostal muscles muscles of resting inspiration During deep forceful inhalation accessory muscles of inspiration -Expiration during forceful breathing is participate to increase size of the thoracic an active process cavity Deep forcef ul - Muscles of exhalation increase pressure breathing -Sternomastoid: elevate sternum in abdomen and thorax: -Scalene: elevate first two ribs (Abdominal muscles and Internal -Anterior serrati: elevate many of the ribs intercostal) -Pectoralis minor: elevate 3rd , 4th and 5th ribs Different pressures that affect respiration Atmospheric Alveolar Intrapleural Transpulmonary pressure pressure pressure pressure Intra-alveolar pressure ( intrapulmonary pressure ) During inspiration: Between breaths: At the end of During expiration: -1 mmHg, and air 0 mmHg inspiration: +1 mmHg (tidal volume ) flows (Zero pressure) 0 mmHg and and air flows out of from outside to inside “We also called it air stops flowing. the lungs. pause “ the lungs Relation between intra-alveolar pressure and lung volume The values of Intra-alveolar pressure in the diagram indicate the difference between INTRA-ALVEOLAR pressure and ATMOSPHERIC PRESSURE Not the exact values of P-alv Increase in volume 1 Decrease in pressure 2 Atmospheric pressure = alveolar pressure Decrease in volume 3 3 4 1 2 Increase in pressure 4 Atmospheric pressure = alveolar pressure ﻣﮭم ﻧﻌرف ﻗﺎﻋدﺗﯾن ﻗﺑل دراﺳﺔ ھذا اﻟﺿﻐط اوﻻً : أي ﺳطﺣﯾن ﯾﻘﺗرﺑون ﻟﺑﻌض ﺑﯾوﻟّدون ﺿﻐط ﻣوﺟب، واي ﺳطﺣﯾن ﯾﺑﺗﻌدون ﺑﯾوﻟدون ﺿﻐط ﺳﺎﻟب ﺛﺎﻧﯾًﺎ: اﻟﺻدر داﺋﻣًﺎ ﯾﻧدﻓﻊ ﻟﻠﺧﺎرج، واﻟرﺋﺔ ﻟﻠداﺧل ﻟﻠﺧﺎرج واﻟداﺧل > ﯾﺑﺗﻌدون ﻋن ﺑﻌض > ﺿﻐط ﺳﺎﻟب Intrapleural pressure وش اﻟﻔﺎﺋدة ﻣﻧﮫ؟ ﻟو ﻛﺎن ﻣو ﻣوﺟود اﻟرﺋﺔ ﺑﯾﺣﺻل ﻟﮭﺎ Collapse The site of intrapleural pressure: pleural space ( Between the visceral pleura and parietal pleura ) The values of pressure: ● During resting position (between breaths) it = -5cm H2O(-4 mmHg) . ● During resting inspiration it becomes more –ve = -8 cm H2O, -7.5 cm H2O (Notice that the values are negative with respect to atmospheric pressure at the end of normal expiration) What are the causes of negativity 1 2 The pleural space is a potential space, The lung's elastic tissue causes it to recoil, while that (empty space) due to continuous suction of fluids by of the chest wall causes it to expand. Because of these lymphatic vessels. two opposing forces the pressure in the pleural cavity (which is also the basis of the negative pressure becomes negative. found in most tissue spaces of the body). Female slide only Cont. Of Intrapleural pressure (Negative pressure in pleural fluid) 3-Actual measurements have shown that 1- A negative force is always the pressure is usually about −7 mm Hg, required on the outside of the lungs which is a few millimeters of mercury more to keep the lungs expanded. negative than the collapse pressure of the -This force is provided by negative lungs. pressure in the normal pleural Not that important* space. (Between two pleura) 4-The negativity of the pleural fluid pressure keeps the normal lungs pulled 2- Because the normal collapse against the parietal pleura of the chest tendency of the lungs is about −4 cavity, except for an extremely thin layer mm Hg, the pleural fluid pressure of mucoid fluid that acts as a lubricant. must always be at least as negative as −4 mm Hg (- 5 cm/H2O) to keep the lungs expanded. ﻋﺸﺎن ﻧﻘﺎوم اﻧﻜﻤﺎش اﻟﺮﺋﺔ ﻻزم ﺗﻜﻮن اﻟﻘﯿﻤﺔ ﻧﻔﺲ ﻗﯿﻤﺔ ﺳﺎﻟﺒﯿﺘﮭﺎ أو اﻛﺜﺮ What do you think will happen if someone got a stab at the lungs? Normal Intrapleural We already said that intrapleural pressure ; normal lungs pressure should be ”at least as negative as 4mmHg=5cm/H2O ” but in this case it will become ZERO! Causing the lung to collapse and chest wall to expand Pneumothorax: اﻟﻠﻲ ﺻﺎﯾﺮ ﻓﯿﮫ ان اﻟﮭﻮاء دﺧﻞ اﻟﻤﻨﻄﻘﺔ اﻟﻠﻲ ﻣﻔﺮوض ﺗﺼﯿﺮ ﻣﻨﻄﻘﮫ ﻓﺎﺿﯿﮫ Intrapleural pressure in a normal person and in a person with a pneumothorax. The ف ﺑﺘﺎﻟﻲ اﺛﺮ ﻋﻠﻰ اﻟﻀﻐﻂ اﻟﻤﻮﺟﻮد ﻓﻲ اﻟﻤﻨﻄﻘﺔ numbers are pressures in cm H 0. Pressures are referred to atmospheric pressure; thus, zero وﺻﺎر ال اﻟﻠﻲ 2 pressure means equal to atmospheric pressure. The arrows show expanding or collapsing pressure ”intraplural pressure“ ﻛﺎن ﻧﯿﻘﺘﻒ ﯾﺴﺎوي اﻟﻀﻐﻂ اﻟﺠﻮي وھﺬي ﻣﺸﻜﻠﺔ !! ﻟﯿﮫ؟ elastic forces. Normally, at rest, intrapleural pressure is-5 cm H20 because of equal and ﺑﯿﺼﯿﺮ ﺻﻌﻮﺑﮫ ﻓﻲ الinspiration ﻻن الopposite forces trying to collapse the lungs and expand the chest wall. With a pneumothorax lung أﺧﺬت اﻟﻮﺿﻊ اﻟﻤﺮﯾﺢ ﻟﮭﺎ وﺻﺎر ﻟﮭﺎ the intrapleural pressure becomes equal to atmospheric pressure, causing the lungs to collapse والchest ﺻﺎر collapse and the chest wall to expand. Expand Transpulmonary pressure (Extending Pressure) The difference between the alveolar pressure (Palv) and the pleural pressure(Ppl) TPp = Palv-Ppl It is a measure of the elastic forces in the lungs that tend to collapse the lungs ( the recoil pressure). It prevents lung collapse. زي اﻟﺑﻠوﻧﺔ اﻟﻣﺗﻔوﺧﺔ The bigger the volume of the ﺑﻘوة، ﺑﯾرﺟﻊ ﻣﻧﮭﺎ lung the higher will be its اﻟﮭواء ﺑﻘوة .tendency to recoil The atmospheric pressure is 760 mmHg Summary Pressure During rest During inspiration During expiration Intra-alveolar pressure (0 cmH20) 760 mmHg (-1cmH2o) 759 mmHg (+1cmH2o) 761 mmHg (-4 mmHg) 756 mmHg (-5mmHg) 755 mmHg (just for your information) Intrapleural pressure -5cmH2o -7.5cmH2o -6.5 mmHg according to Linda Transpulmonary pressure (just for your information) TPp= 0 - (-5)= +5 cmH2o TPp= -1 - (-7.5)= +6.5 cmH2o TPp = Palv-Ppl TPp= +1 -(-6.5)= +7.5 mmHg The Intra-alveolar pressure is normally zero (i.e . atmospheric) during the pause. At the start Transpulmonary pressure: of inspiration, it decreases to about -I mmHg During expiration. Intrapleural due to lung expansion. This allows the entry pressure increases, becoming less -ve, Is the pressure that prevents of about 500 ml of atmospheric air into the which helps the lung to recoil. As a lung from collapsing. A newly lungs and as a result, it increases Gradually till result, the intrapulmonary pressure born infant normally requires a it becomes atmospheric again by the end of increases to about +1 mmHg leading transpulmonary pressure of About inspiration. to entry of about 500 ml of air (tidal + 60 mmHg at the first breath to On the other hand, at the start of expiration, expand his lungs it rises to about +1 mmHg due to lung recoil. volume) . This moves 500ml of air outwards from the lungs and as a result, it decreases gradually till becoming atmospheric again by the end of expiration . Compliance of the Lung (CL) Definition The extent to which the lungs will expand for each unit increase in the transpulmonary pressure. In other words: it’s the measure of the lungs ability to stretch and expand. -Transpulmonary pressure = Alveolar pressure - pleural pressure i.e the ratio of the change in the lung volume produced per unit change in the distending pressure. For both lungs in adult = 200ml of air / cm H2O For lungs and thorax together = 110 ml/cm H2O Example ﻧﻘﺺ ﻷن ﻣﻄﺎطﯿﺔ اﻟﺜﻮراﻛﺲ ﻗﻠﯿﻠﺔ A thick rubber is considered to have a low Compliance A thin rubber is considered to have a high ﻣطﺎط = compliance Rubber CL = Change in Volume / Change in Pressure Helpful video Imagine we have tissue A and tissue B. if we increase the pressure in both by +1 mmHg, and tissue A increases its volume more than B. Then we conclude that the compliance of A is higher that B Lung compliance diagram The characteristics of the lung 1 compliance diagram are determined by 2 the elastic forces of the lungs. These can be divided into: ⅓ is due to the elastic forces of the lung tissue itself ( elastin, collagen). ⅔ of the elastic forces caused by surface tension of the fluid that lines inside walls of the alveoli and other lungs air space. This is a Compliance diagram in a healthy person. This diagram shows compliance of the lungs alone Diseases affecting the lung compliance Increase in lung compliance: Reduce in lung compliance: Emphysema increases the compliance Lung compliance is reduced in of the lungs because it destroys the pulmonary fibrosis, pulmonary alveolar septal tissue rich with elastic edema, diseases of the chest wall fibers that normally opposes lung (kyphosis, scoliosis, paralysis of the muscle, etc….). expansion.
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