Lung Volumes Lecture Note PDF

OVERVIEW ANATOMY AND PHYSIOLOGY OF THE PULMONARY SYSTEM AND THORACIC CAGE. Prof. Dr./ Mona Abdel Khalek Dr. Ahmed Abd Elhalim Anatomy of Respiratory System The respiratory system consists of organs: 1. Nose 2. Mouth (oral cavity) 3. Pharynx (throat) 4. Larynx (voice box...

OVERVIEW ANATOMY AND PHYSIOLOGY OF THE PULMONARY SYSTEM AND THORACIC CAGE. Prof. Dr./ Mona Abdel Khalek Dr. Ahmed Abd Elhalim Anatomy of Respiratory System The respiratory system consists of organs: 1. Nose 2. Mouth (oral cavity) 3. Pharynx (throat) 4. Larynx (voice box) 5. Trachea (windpipe) 6. Bronchi 7. Lungs Organs of the Respiratory System Divided into: Conducting zone Respiratory zone  Nose Provides an airway for respiration Moistens and warms air Filters inhaled air Resonating chamber for speech  The Trachea Descends into the mediastinum C-shaped cartilage rings keep airway open Carina Marks where trachea divides into two primary bronchi  Bronchi Bronchial tree: Primary bronchi (main bronchi) Secondary (lobar) bronchi Three on the right Two on the left Tertiary (segmental) bronchi Branch into each lung segment Bronchioles Little bronchi, less than 1 mm in diameter Terminal bronchioles Less than 0.5 mm in diameter  Structures of the Respiratory Zone Consists of air-exchanging structures Respiratory bronchioles branched from terminal bronchioles Lead to alveolar ducts Lead to alveolar sacs Gross Anatomy of the Lungs Major landmarks of the lungs Apex, Base, Hilum, and Root Left lung Superior and inferior lobes Fissure – oblique Right lung Superior, middle, and inferior lobes Fissures – oblique and horizontal Anterior View of Thoracic Structures  The Pleurae A double-layered sac surrounding each lung Parietal pleura Visceral pleura Pleural cavity Potential space between the visceral and parietal pleurae The Mechanisms of Ventilation Two phases of pulmonary ventilation Inspiration – inhalation Expiration – exhalation  Inspiration The principal muscles are: 1. The diaphragm 2. Intercostal muscles - Volume of thoracic cavity increases - Decreases internal gas pressure -Action of the diaphragm Diaphragm flattens -Action of intercoastal muscles Contraction raises the ribs  Inspiration Accessory muscles are typically only used when the body needs to process energy quickly (e.g. during strenuous exercise, during the stress response, or during an asthma attack): Scalenes Sternocleidomastoid Pectoralis major Pectoralis minor Erector spinae – extends the back Expiration Quiet expiration – chiefly a passive process Inspiratory muscles relax Diaphragm moves superiorly Volume of thoracic cavity decreases Forced expiration – an active process Produced by contraction of Internal and external oblique muscles Transverse abdominal muscles  Neural Control of Ventilation Most important respiratory center Ventral respiratory group Located in reticular formation in the medulla oblongata Neurons generate respiratory rhythm Lung Volumes and Capacities 6000 IRV IC Volume (ml) VC VT TLC ERV FRC RV 0 Primary Lung Lung Capacities Volumes Basic Lung Volumes There are 4 volume subdivisions: 1. Tidal Volume: TV 2. Inspiratory Reserve Volume: IRV 3. Expiratory Reserve Volume: ERV 4. Residual Volume: RV Basic Lung Volumes There are 4 volume subdivisions: They do not overlap They can not be further divided When added together equal total lung capacity Basic Lung Volumes Tidal Volume: TV The amount of gas inspired or expired with each normal breath. About 500 ml Basic Lung Volumes Inspiratory Reserve Volume: IRV Maximum amount of additional air that can be inspired from the end of a normal inspiration. Basic Lung Volumes Expiratory Reserve Volume: ERV The maximum volume of additional air that can be expired from the end of a normal expiration.  Basic Lung Volumes Residual Volume: RV The volume of air remaining in the lung after a maximal expiration. This is the only lung volume which cannot be measured with a spirometer.  Lung Capacities Are subdivisions of the total volume that include two or more of the 4 basic lung volumes Lung Capacities Total Lung Capacity: TLC Vital Capacity: VC Functional Residual Capacity: FRC Inspiratory Capacity: IC Lung Capacities Total Lung Capacity: TLC The volume of air contained in the lungs at the end of a maximal inspiration. Called a capacity because it is the sum of the 4 basic lung volumes TLC= RV+IRV+TV+ERV  Lung Capacities Vital Capacity: VC The maximum volume of air that can be forcefully expelled from the lungs following a maximal inspiration. Called a capacity because it is the sum of inspiratory reserve volume, tidal volume and expiratory reserve volume. VC= IRV+TV+ERV = TLC - RV Lung Capacities Functional Residual Capacity: FRC The volume of air remaining in the lung at the end of a normal expiration. Called a capacity because it equal residual volume plus expiratory reserve volume. FRC= RV+ERV Lung Capacities Inspiratory Capacity: IC Maximum volume of air that can be inspired from end expiratory position. Called a capacity because it is the sum of tidal volume and inspiratory reserve volume. This capacity is of less clinical significance than the other three. IC= TV+IRV Respiratory Diseases Restrictive Disease: Makes it more difficult to get air in to the lungs. They “restrict” inspiration. Decreased VC; Decreased TLC, RV, FRC Includes: Fibrosis.Sarcoidosis Muscular diseases Chest wall deformities.Tumors Pleural Effusion, Pneumothorax Respiratory Diseases Obstructive Disease Make it more difficult to get air out of the lungs. Decrease VC; Increased TLC, RV, and FRC Includes: Emphysema Chronic bronchitis Asthma  Respiratory Muscles Primary Accessory Inspiratory Primary inspiratory Forced expiration )any muscle attached Expiratory )Diaphragm and )Abdominal ms and to the upper limb and )Abdominal muscles( external intercostal( internal intercostal ( the thoracic cage ( Scm / scalenii / Pectoralis / Serratus  Sternal Part: Costal Part: Narrow Slips Arise From Arise From The Inner The Back Of The Xiphoid Surfaces Of The Lower 6 Costal Cartilages &Lower Process As TwoHorizontal 4 Ribs. Bundle And Then They Interdigitate With The Descends To The Central Transversus Abdominis Tendon Lumbar or Vertebral Part: Each Part Arises From TwoFibrous Arches & From The Bodies Of The Upper 2-3 Lumbar Vertebral Bodies & Disc. Extend to the tip of transverse process of the same vertebra. These Arches Are The Medial And Lateral Arcuate Ligaments. The diaphragm is the major muscle of respiration It is a curved, modified half-dome, muscluofibrous sheet that separates the thoracic cavity from the abdominal cavity. The word diaphragm literally means, dia that is across, and phragm means wall.  The Diaphragm The body relies on the diaphragm for normal respiratory function. It is accounting for 75% of the tidal volume which is achieved by its excursion during respiration.  The Diaphragm Contraction of the diaphragm has following functions: ▪ Decreasing intrapleural pressure, ▪ Expanding the rib cage through its zone of apposition by generating positive intra-abdominal pressure, ▪ Expanding the rib cage using the abdomen as a fulcrum.  The Diaphragm The diaphragm is also important in performing such actions as: blowing out the air, laughing, singing, whistling, crying, yawning, coughing, sneezing, vomiting, defecating, urinating, and in delivering a baby or giving birth.  TheDiaphragmaticTone: It was revealed that the muscle spindles definitely present in the human diaphragm in the area adjacent to the central tendon.  The DiaphragmaticTone: The natural stimulus for the stretch reflex is the abdominal content weight in the supine position. The resultant tonic activity in the diaphragm has a considerable significance in the maintenance of functional residual capacity and preventing the viscera from being pushed into the thorax. Diaphragmlength, velocity of shorteningandpower Diaphragmatic length is determined by: Lung volume Chest wall configuration. Pre-inspiratory changes in diaphragmatic length are uniquely determined by abdominal volume. The diaphragm's main role during exercise is to generate flow rather than pressure and that its 13% increase in power from quiet breathing to 70% of maximal workload is due to mainly an increase in velocity of shortening. The diaphragm is composed of 55 ± 5% type I fibers (high oxidative, slow twitch fibers), 20 ± 6% type IIa fibers (high oxidative fast twitch fibers), and 25% type IIb (low oxidative fast twitch fibers). These findings might be responsible for the diaphragmatic endurance capacity and its unique function characteristics. The increase in the respiratory load results in adaptation in both endurance and strength The natural stimulus for the stretch reflex is the abdominal content weight in the supine position  The phrenic nerve is the sole motor supply Phrenic Nerve to the diaphragm. It arises chiefly from the fourth cervical ramus, so it is formally considered part of the cervical plexus. An accessory phrenic nerve may arise from roots C5 and C6 or from the nerve to the subclavius muscle Originating around the level of the scalenus anterior muscle, the phrenic nerve courses inferiorly through the neck and thorax before reaching its end point, the diaphragm. Thus, the phrenic nerve has a relatively long course before reaching its final destination. Phrenic Nerve The successful impulse of respiratory stimulus from the brain to the diaphragm can be compromised by an interruption of the phrenic nerve at any point along this course.  diaphragmatic dysfunction Mechanical diaphragmatic dysfunction can be caused by many disorders which can affect the transmission of the respiratory stimulus from the brain down to the diaphragm through the phrenic nerve. If the diaphragm is fatigued due to accumulation of lactic acid, the result is breathlessness Fatigue develops when the diaphragm is made to generate a pressure with each inspiration greater than 40% of the maximal transdiaphragmatic pressure. The time limit of human diaphragm was shorter than 60 min. About 55% of the fibers of human diaphragm were of the slow twitch high oxidative type I which are fatigue resistant. Diaphragmatic blood flow increased as the work of breathing increased. Respiratory muscle fatigue play a role in the sensation of Dyspnea. Dyspnea might occur as a result of either hyperventilation at a given exercise load or weakness of respiratory muscles Limitation of exercise capacity in normal subjects might be due to respiratory muscle fatigue; levels of ventilation greater than 55% of maximal breathing capacity