Pulmonary Ventilation PDF

PULMONARY VENTILATION Dr. Berrak YEĞEN The goals of respiration to provide oxygen to the tissues and to remove carbon dioxide. To achieve these goals: (1) pulmonary ventilation, the inflow and outflow of air between the atmosphere and the lung alveoli; (2) diffusion of oxygen and carbon...

PULMONARY VENTILATION Dr. Berrak YEĞEN The goals of respiration to provide oxygen to the tissues and to remove carbon dioxide. To achieve these goals: (1) pulmonary ventilation, the inflow and outflow of air between the atmosphere and the lung alveoli; (2) diffusion of oxygen and carbon dioxide between the alveoli and the blood; (3) transport of oxygen and carbon dioxide in the blood and body fluids to and from the body's tissue cells; (4) regulation of ventilation Objectives: You will be able to define- internal and external respiration the nonrespiratory functions atmospheric, intra-alveolar, intrapleural pressures respiratory cycle / muscles involved elastic behavior of lungs work of breathing lung volumes and capacities “pulmonary” and “alveolar” ventilation  Respiratory System Pulmonary circulation: Right ventricle → pulmonary trunk → lungs → pulmonary veins → left atrium Ventilation-Perfusion -Circulation → *External Respiration *Internal Respiration (=Cellular Respiration)  External respiration All events involved in the exchange of O2 and CO2 between the external environment and the cells 1. Ventilation 2. Exchange of gases between alveoli and blood 3. Transport of gases 4. Exchange of gases between tissues and blood Respiratory sys. involved only in 1 & 2. Internal or cellular respiration Intracellular metabolic processes carried out within the mitochondria: use O2 and produce CO2 during the derivation of energy from nutrient molecules what is respiratiry quptient Respiratory Quotient (RQ) Mixed diet- RQ= CO2 produced = 200 ml/ min = 0.8 O2 consumed 250 ml/ min (carbohydrate: 1; fat: 0.7; protein: 0.8) Conditioning Respiratory epithelia found in the nasal cavity and trachea: Warm air to body temperature Add water vapor Filter out foreign material Non-respiratory functionsof the respiratorysystem 1. Water loss and heat elimination- humidification and warming of insp. air 2. Enhancement of venous return 3. Control of acid base balance 4. Speech, singing, other vocalization 5. Defense against foreign matter 6. Removing, modifiying, activating (AG II), inactivating (PG) materialstrue false 7. Smell VENTILATION PERFUSION The lung is an elastic structure collapses like a balloon → force is needed to keep it inflated "floats" in the thoracic cavity, surrounded by a thin layer of pleural fluid continual suction of excess fluid into lymphatic channels - suction between the visceral and the parietal pleura Atmospheric pressure Pressures important in ventilation  Exhalation: When the diaphragm and chest wall muscles relax, the Inhalation: When the diaphragm and chest wall thoracic cavity recoils, decreasing muscles contract, the volume of the thoracic the volume. This increases the cavity (chest cavity) increases. This expansion intrapleural pressure (Pip) towards lowers the intrapleural pressure (Pip) relative to atmospheric pressure. The pressure gradient between the alveoli and the atmospheric pressure (P atm). As a result, the intrapleural space reverses, causing pressure difference (transpulmonary pressure) the lungs to deflate and passively between the alveoli and the intrapleural space expel air. Transpulmonary pressure Pressure in the Pleural Cavity At any constant temperature P1V1 = P2V2 The lungs can be expanded and contracted in 2 ways: (1) by downward and upward movement of the diaphragm to lengthen or shorten the chest cavity, (2) by elevation and depression of the ribs to increase and decrease the anteroposterior diameter of the chest cavity. INSPIRATION Rib elevations by external intercostal muscles EXPIRATION During inspiration, Contraction of the diaphragm pulls the lower surfaces of the lungs downward During heavy breathing, extra force is achieved mainly by contraction of – all the muscles that elevate the chest cage : a) external intercostals b) others that help are: (1) sternocleidomastoid muscles lift upward on the sternum (2) anterior serrati- lift many of the ribs; (3) scaleni- lift the first two ribs. During expiration, The diaphragm simply relaxes, and the elastic recoil of the lungs, chest wall, and abdominal structures compresses the lungs and expels the air During heavy breathing, the muscles that pull the rib cage downward are (1) abdominal recti, pulling downward on the lower ribs; they and other abdominal muscles also compress the abdominal contents upward against the diaphragm, (1) internal intercostals Changes in lung volume and intra-alveolar pressure during inspiration and expiration  Intraalveolar and intrapleural pressure changes throughout the respiratory cycle Compliance The magnitude of change in lung volume by a given change in transmural pressure gradient Compliance =  V P stretchability of the lungs and chest wall Compliance diagram in a healthy person. This diagram shows compliance of the lungs alone. Compliance how much effort is required to stretch or distend the lungs asbestosis  stiff lung  force to stretch : less compliant 0.13 L / cm H2O in thoracic cage 0.22 L / cm H20 when removed from thorax  V P The characteristics of the compliance diagram are determined by the elastic forces of the lungs: 1. elastic forces of the lung tissue itself (elastic recoil) in cause of incerased surface tension what is the elemet that gets infulensed as well 2. elastic forces caused by surface tension of the fluid that lines the inside walls of the alveoli  Elastic recoil Returning back to preinspiratory volume when inspiratory muscles relax at the end of inspiration elastin and collagen fibers interwoven among the lung parenchyma deflated lungs, these fibers are in an elastically contracted and kinked state when the lungs expand, the fibers become stretched and unkinked, thereby elongating and exerting even more elastic force  Surface tension When water forms a surface with air, the water molecules on the surface of the water have an especially strong unequal attraction for one another water surface is attempting to contract causes the alveoli to try to collapse an elastic contractile force of the entire lung “surface tension elastic force” Surfactant complex mixture of lipids and proteins (phospholipid dipalmitoylphosphatidylcholine, surfactant apoproteins, and calcium ions) intersperses between water molecules water lowers the alvolar surface tension surfactant Benefits: 1. reduces the tendency to recoil 2. increases pulmonary compliance “maintaining lung stability” Pulmonary elastic behavior 1. Elastic connective tissue (elastin fibers) -1/3- 2. Alveolar surface tension -2/3- Less the surface tension, greater compliant is the lungs Alveolar Structure Figure 17-2g 10 per cent of the surface area of the alveoli Interdependence of the alveoli “tug of war” Second factor in “maintaining lung stability” Newborn RDS ARDS?? NRDS: deficiency of pulmonary surfactant infants born prematurely More difficult to expand - a collapsed alveolus by a volume than to increase a partially expanded alveolus by the same volume Changes in compliance decreased:* fibrotic lung tissue (interstitial fibrosis) * pulmonary congestion * kyphosis, scoliosis, * paralyzed or fibrotic muscles increased: emphysema Barrel chest "Work" of Breathing during normal quiet breathing, all respiratory muscle contraction occurs during inspiration expiration is almost entirely a passive process Work of inspiration: (1) to expand the lungs against the lung and chest elastic forces, compliance work or elastic work; (2) to overcome the viscosity of the lung and chest wall structures, tissue resistance work; (3) to overcome airway resistance for the movement of air into the lungs, airway resistance work. Work of Breathing 3 % of total energy expenditure May be increased: 1. Pulmonary compliance  2. Airway resistance  3. Elastic recoil  (abdominal muscles work) 4. A need for increased ventilation Exercise- ventilation  25 fold Total energy exp. 15-20 folds; work of breathing 5 % Patients with poorly compliant lungs, COPD 30 % spirometry A simple method for studying pulmonary ventilation is to record the volume movement of air into and out of the lungs: Volumes: tidal volume (500 milliliters in the adult male) inspiratory reserve volume (3000 milliliters). expiratory reserve volume (1100 milliliters). residual volume (1200 milliliters). Capacities: inspiratory capacity functional residual capacity vital capacity total lung capacity SPIROGRAM Lung Volumes and Capacities Volumes: 1. Tidal Volume (TV): The amount of air inhaled or exhaled during a normal breath. Value: 500 milliliters (mL) in an adult male. 2. Inspiratory Reserve Volume (IRV): The additional amount of air that can be inhaled after a normal inspiration. Value: 3000 mL. 3. Expiratory Reserve Volume (ERV): The additional amount of air that can be exhaled after a normal expiration. Value: 1100 mL. 4. Residual Volume (RV): The amount of air remaining in the lungs after a maximal exhalation. Value: 1200 mL. Capacities: Capacities are combinations of two or more volumes. 1. Inspiratory Capacity (IC): The total amount of air that can be inhaled after a normal exhalation. Calculation: IC = TV + IRV. Value: 500 mL (TV) + 3000 mL (IRV) = 3500 mL. 2. Functional Residual Capacity (FRC): The amount of air remaining in the lungs after a normal exhalation. Calculation: FRC = ERV + RV. Value: 1100 mL (ERV) + 1200 mL (RV) = 2300 mL. 3. Vital Capacity (VC): The maximum amount of air that can be exhaled after a maximal inhalation. Calculation: VC = IRV + TV + ERV. Value: 3000 mL (IRV) + 500 mL (TV) + 1100 mL (ERV) = 4600 mL. 4. Total Lung Capacity (TLC): The total amount of air in the lungs after a maximal inhalation. Calculation: TLC = IRV + TV + ERV + RV. Value: 3000 mL (IRV) + 500 mL (TV) + 1100 mL (ERV) + 1200 mL (RV) = 5800 mL. Summary Table Volume/Capacity Value (mL) Tidal Volume (TV) 500 Inspiratory Reserve Volume (IRV) 3000 Expiratory Reserve Volume (ERV) 1100 Residual Volume (RV) 1200 Inspiratory Capacity (IC) 3500 Functional Residual Capacity (FRC) 2300 Vital Capacity (VC) 4600 Total Lung Capacity (TLC) 5800  FEV1/FVC =80 % Forced expiratory volume 1 (sec) FEV1= 1.2 L; FVC= 3 L FEV1= 4 L; FVC= 5L FEV1/FVC = 40 % FEV1/FVC =80 % Minute RespiratoryVolume Equals Respiratory Rate Times Tidal Volume minute respiratory volume is the total amount of new air moved into the respiratory passages each minute tidal volume times the respiratory rate per minute 500 milliliters x 12 breaths/minute = 6 L/min Pulmonary ventilation Alveolar Ventilation pulmonary ventilation continually renews the air in the gas exchange areas of the lungs, where air is in proximity to the pulmonary blood alveoli, alveolar sacs, alveolar ducts, and respiratory bronchioles Some of the air simply fills respiratory passages where gas exchange does not occur, such as the nose, pharynx, and trachea “dead space air” “anatomic dead space” Rate of Alveolar Ventilation Alveolar ventilation per minute is the total volume of new air entering the alveoli each minute. With a normal tidal volume of 500 milliliters, a normal dead space of 150 milliliters, and a respiratory rate of 12 breaths per minute, alveolar ventilation= 12 × (500 - 150), or 4200 ml/min  volume of all the space of the respiratory system other than the alveoli -anatomic dead space some of the alveoli themselves are nonfunctional or only partially functional because of absent or poor blood flow through the adjacent pulmonary capillaries - physiologic dead space 500 ml 150 ml Anatomic dead space Physiologic 350 ml dead space Ventilation Total pulmonary ventilation and alveolar ventilation Total pulmonary ventilation = ventilation rate  tidal volume Dead space filled with fresh air The first exhaled 150 air comes out of mL the dead space. Only 350 mL leaves 1 the alveoli. 2700 mL Atmospheric 1 End of inspiration air 2 Exhale 500 mL Dead space 2 (tidal volume). is filled with 150 fresh air. 150 mL Respiratory 3 At the end of Only 350 expiration, the 350 mL cycle in 2200 mL dead space is of fresh air 150 an adult filled with reaches 2200 mL “ stale” air from alveoli. alveoli. Dead space filled 4 with stale air The first 150 mL 4 Inhale 500 mL of air into the 150 of fresh air alveoli is stale mL (tidal volume). air from the dead space. KEY 2200 mL 3 PO2 = 160 mm Hg PO2 ~ ~ 100 mm Hg  Effects of different breathing patterns on alveolar ventilation Quiet breathing: 500 ml / breath; 12 /min; Pulm. V. 6 L/ min; Alv. Vent. 4.2 L/min Deep-slow beathing: 1.2 L/breath; 5 /min; Pulm. V. 6 L/ min; Alv. Vent. 5.25 L/min Shallow-rapid breathing: 150 ml/ breath; 40 / min; Pulm. V. 6 L/ min; Alv. Vent. 0 L/min A person can live for a short period with a minute respiratory volume as low as 1.5 L/min and a respiratory rate of only 2 to 4 breaths per minute