Mechanism of Breathing PDF

MECHANIC OF BREATHING DR/ AHMED ADEL +201017762287  MECHANIC OF BREATHING ❖ Transport of oxygen from atmosphere to tissue Def ❖ Oxidation of food stuff and removal of CO2 1) External respiration...

MECHANIC OF BREATHING DR/ AHMED ADEL +201017762287  MECHANIC OF BREATHING ❖ Transport of oxygen from atmosphere to tissue Def ❖ Oxidation of food stuff and removal of CO2 1) External respiration Pulmonary ventilation Classification: Gas exchange 2) Carriage of gases (O2, CO2) by blood. 3) Internal respiration. Respiratory cycle: Each respiratory cycle consists of 1-Inspiration: Active process (needs energy) Contraction of respiratory muscles (diaphragm and intercostal muscles) Thoracic cavity increase and air rush in. Its duration 1.3 sec. 2-Expiration: Passive process Relaxation of respiratory muscles Reduction of the thoracic cavity size Air rush out Duration 1.7 sec. 3-Expiratory pause. Dr/ Ahmed Adel +201017762287 1  Mechanics of respiration Muscles of respiration 1-diaphragm:-  It is responsible for about 75% of respiration  Contraction of diaphragm leads to its descend from 1.5-7cm  It is supplied by phrenic nerve(cervical 3,4,5) 2-External intercostal Ms.:  Their Contraction increase the antero-posterior diameter and transverse diameter of the chest.  Nerve supply:1-10 thoracic segments. Mechanics of Inspiration:  As a result of contraction of both Diaphragm and Intercostal ms  Chest increase in all its dimensions.  Lung follows the chest passively.  Lung volume increase and the intra pulmonary pressure decrease to about -2 mmHg.  Intra pleural pressure decrease to -6 mmHg  Air rush in (inspiration). Dr/ Ahmed Adel +201017762287 2  How Expiration occurs  Relaxation of respiratory Ms.  Chest decrease in all its dimensions.  Lung volume decrease & intra pulmonary pressure increase to about +2 mmHg.  Air rush out (expiration). Forced respiration: Forced inspiration:  Accessory muscles of respiration (sternocleiomastoid, serratus anterior & scalini muscle) Forced expiration::  Active process contraction of abdominal muscles & internal intercostal. Pulmonary ventilation Air flow to the lung It is affected by : 1- Resistance of the air passage. 2-pressures in the thoracic cavity( I.P.P & I.Pul.P) 3- surfactant 4-lung & chest compliance. Factors affecting pulmonary ventilation Resistance of Pressure Chest and lung respiratory relationship in Surfactant compliance passage thoracic cavity Dr/ Ahmed Adel +201017762287 3  Bronchial muscle tone Nervous factors:- Autonomic nervous system Sympathetic >>>>>bronchodilation. Parasympathetic>>>>bronchoconstriction. Chemical factors:- Histamine>>>constriction Serotonin>>>constriction Platelet activating factor Intra pulmonary pressure  It is the pressure inside lung alveoli. It is connected to the atmosphere.  It equals -2mmHg during inspiration.  +2mmHg during expiration.  It equals atmospheric pressure in the expiratory pause. pleura  Each lung is enclosed in a double –walled sac called the pleura.  Both layer of pleura is formed of serous membrane  The portion that adheres to the thoracic cavity is parietal pleura  The portion which covers the lung is the visceral layer  Between the two layers of pleura a space called intra pleural space Dr/ Ahmed Adel +201017762287 4  Intra Plural fluid  It is the fluid that filled pleural cavity  It is a lubricant fluid which allow the pleura to slide easily against each other during ventilation.  Normal amount of fluid equals 20-25 ml in each space  It is formed and reabsorbed continuously.  It is produced by parietal circulation (intercostal arteries)  It is reabsorbed by lymphatic system  If formation exceeds reabsorptions pleural effusion occurs Intra Plural fluid  It is the pressure inside the pleural cavity.  It is a negative pressure.  It equals -3mmHg during expiration.  It equals -6 mmHg during inspiration. Intra plural pressure  It is the pressure in the space between the two layers of pleura  It is usually negative pressure  Normal value of I.P.P.  -3mm Hg at the end of normal expiration.  -6mm Hg at the end of normal inspiration.  -30.mm Hg->forced inspiration. Causes of negativity of I.P.P  Lack of air in the pleural cavity  Surface tension of the fluid lining the alveolar wall  Elastic recoil lf the lung which continuously pulls the visceral pleura away from the parietal pleura  N.B –ve force is a suction force. Dr/ Ahmed Adel +201017762287 5 Significance of -ve I.P.P  It helps expansion of the lung.  Helps venous return to the heart.  Helps blood flow through pulmonary vessels.  Helps lymphatic flow in the thoracic duct Puemothorax  Presence of air in the pleural cavity.  Air can enter the pleura through wound in the chest wall Types:-  1-closed  2- open  3-valvular  4-artificial Manifestation:-  sudden occurrence of pleural pain.  Dyspnea.  Patient may be cyanosed surfactant  It is a lipoprotein substance.  It is synthesized and released from type 11 alveolar cells. Functions of surfactant:-  1-it decreases the surface tension of the fluid lining the alveoli so it helps lung expansion.  It may activate and exert stimulant effect on macrophage. Dr/ Ahmed Adel +201017762287 6  It has a bacteriolytic effect, rendering the bacteria more susceptible to alveolar macrophage.  It assists the ciliary movement of upper respiratory tract. Surfactant decrease in :-  Respiratory distress syndrome.  cigarette smoking. compliance  Ability of the lung and chest to expand.  Expansibility of the lung and chest wall. Factors affecting:-  Lung factors  Elastic force of the lung tissues, compliance decreases in cases of fibrosis.  Surface tension of the lung and surfactant Factors in the chest wall  The elastic properties of the thorax are caused by the natural elasticity of muscles, tendons and connective tissues of the chest. Dr/ Ahmed Adel +201017762287 7