RESPIRATORY PHYSIOLOGY Anatomy review Anatomy review Anatomy review

Pressures Atmospheric pressure Atmospheric pressure Alveolar pressure (intrapulmonary pressure) Alveolar pressure (intrapulmonary pressure) Intrapleural pressure Intrapleural pressure Boyle’s Law Boyle’s Law More volume=less pressure More volume=less pressure Less volume=more pressure Less volume=more pressure

Diaphragm is chief respiratory muscle (80%) Diaphragm is chief respiratory muscle (80%) Intercostal muscles are secondary (20%) Intercostal muscles are secondary (20%) - Diaphragm is controlled by phrenic nerve (C3,4,5) - Diaphragm is controlled by phrenic nerve (C3,4,5) - Range of movement: from 1 cm (normal breathing) to 10cm in heavy breathing. Parietal pleura attaches to diaphragm Visceral pleura attaches to parietal pleura (thin space in b/w filled with serous fluid) Lungs attach to visceral pleura.

Inspiration: Inspiration: - Before inspiration pressure in lung equals atmospheric pressure: 760 mm Hg or 1 atm - Increasing the size of the lungs will cause pressure to drop and air to rush in. How does lung increase in size? - Boyle’s law: the pressure of a gas in a closed container is inversely proportional to the volume of the container. - incr. in size of container pressure will decrease pressure.. Intrapleural pressure is 756 mm Hg and during inspiration (as diaphragm is pulling down) pressure drops to 754 mm Hg. External intercostals contract and pull rib cage up and forward (anterior) causing a-p diameter to increase.

When volume increases, pressure inside lung When volume increases, pressure inside lung (alveolar, intrapulmonic pressure) drops from 760 to 758. A pressure gradient is established between the atmosphere and the alveoli. Air rushes in (pressure gradient) to alveoli from atm. Air rushes in (pressure gradient) to alveoli from atm. Expiration: pressure in lungs is greater than atm. Expiration: pressure in lungs is greater than atm. - diaphragm relaxes and dome shape muscle pushes up (elasticity). Internal intercostals cause a-p diameter to decrease - lung pressure increases to 762. Air will flow from higher to lower pressures.

Thoracic Volume and Inspiration

Thoracic Volume and Expiration

Changes in Thoracic Volumes

Factors Influencing Pulmonary Ventilation Airway Resistance: Airway Resistance: Amount of drag air encounters in respiratory passageways; not significant since airway diameters are large and at terminal bronchioles gasses travel by diffusion Amount of drag air encounters in respiratory passageways; not significant since airway diameters are large and at terminal bronchioles gasses travel by diffusion Surface Tension: Surface Tension: At gas-liquid boundaries, liquids are more attracted to each other (cohesiveness), surfacant at the alveoli keeps water from being cohesive and allows alveoli to be more functional (less energy needed for breathing) At gas-liquid boundaries, liquids are more attracted to each other (cohesiveness), surfacant at the alveoli keeps water from being cohesive and allows alveoli to be more functional (less energy needed for breathing) Lung Compliance: Lung Compliance: The distensibility of the lungs, ability to stretch; higher compliance leads to better ventilation (fibrosis, airway blockages, decreased surfacant, and decreased thoracic cage flexibility lead to less compliance) The distensibility of the lungs, ability to stretch; higher compliance leads to better ventilation (fibrosis, airway blockages, decreased surfacant, and decreased thoracic cage flexibility lead to less compliance)

Respiratory Volumes and Capacities

Respiratory Volumes Tidal Volume: Tidal Volume: The amount of air that moves in and out of the lungs with a normal breath at rest (~500 mL) The amount of air that moves in and out of the lungs with a normal breath at rest (~500 mL) Inspiratory Reserve Volume: Inspiratory Reserve Volume: The amount of air that can be inspired forcibly beyond the tidal volume ( mL) The amount of air that can be inspired forcibly beyond the tidal volume ( mL) Expiratory Reserve Volume: Expiratory Reserve Volume: The amount of air that can be expired forcibly beyond a tidal expiration ( mL) The amount of air that can be expired forcibly beyond a tidal expiration ( mL) Residual Volume: Residual Volume: The amount of air remaining in the lungs even after the most forceful expiration (1200 mL) The amount of air remaining in the lungs even after the most forceful expiration (1200 mL)

Respiratory Capacities Inspiratory Capacity: Inspiratory Capacity: Total amount of air that can be inspired after a tidal expiration; TV + IRV Total amount of air that can be inspired after a tidal expiration; TV + IRV Functional Residual Capacity: Functional Residual Capacity: Total amount of air remaining in lungs after a tidal expiration; ERV + RV Total amount of air remaining in lungs after a tidal expiration; ERV + RV Vital Capacity: Vital Capacity: Total amount of exchangeable air; TV + IRV + ERV Total amount of exchangeable air; TV + IRV + ERV Total Lung Capacity: Total Lung Capacity: Sum of all lung volumes Sum of all lung volumes

Volumes and Capacities

Dead Space Anatomical dead space: Anatomical dead space: The volume of air found in the conduits of the respiratory system NOT involved in gas exchange The volume of air found in the conduits of the respiratory system NOT involved in gas exchange Alveolar dead space: Alveolar dead space: Regions where alveoli cease to function due to collapse or obstruction Regions where alveoli cease to function due to collapse or obstruction Total dead space: Total dead space: Alveolar dead space + Anatomical dead space Alveolar dead space + Anatomical dead space

Non-Respiratory Air Movements Cough Cough Sneeze Sneeze Crying Crying Laughing Laughing Hiccups Hiccups Yawn Yawn

Regulation of Respiration Medullary respiratory center Medullary respiratory center Dorsal respiratory center (DRC) Dorsal respiratory center (DRC) Ventral respiratory center (VRC) Ventral respiratory center (VRC) Pontine center Pontine center formerly called the Pneumotaxic center Hypothalamus Hypothalamus

Gas Transport Oxyhemoglobin: HbO 2 Oxyhemoglobin: HbO 2 Deoxyhemoglobin: HHb Deoxyhemoglobin: HHb Carbaminohemoglobin: HbCO 2 Carbaminohemoglobin: HbCO 2 External Respiration: Oxygen and Carbon Dioxide concentration is measured as a unit of pressure called partial pressure (p) Blood coming into the lungs (pulmonary artery- capillary) is deoxygenated blood= PO 2 is 40 mm Hg. PCO 2 is 45 mm Hg

Air in the alveoli: PO 2 = 105 mm Hg PCO 2 = 40 mm Hg Oxygen and Carbon dioxide are highly fat soluble and can diffuse through membranes with ease. As gases pass from the blood pass an alveolus gases will diffuse from areas of higher concentration to lower. (diffusion gradients) PO 2 in blood after passing alveolus is 105 mm Hg PCO 2 in blood after passing alveolus is 40 mm Hg

Internal respiration: Exchange of gases in the tissues. Internal respiration: Exchange of gases in the tissues. CO 2 is a byproduct of cellular metabolism. PCO 2 in tissue space: 45 mm Hg PO 2 in tissue spaces: 40 mm Hg O2 will diffuse into tissue spaces (105) and CO2 will diffuse into blood (45)

Gas Transport at the Tissues Carbon dioxide transported to and from the lungs and tissues in three ways: Carbon dioxide transported to and from the lungs and tissues in three ways: Dissolved in plasma 7% Dissolved in plasma 7% Chemically bound to hemoglobin (carbaminohemoglobin) 23% Chemically bound to hemoglobin (carbaminohemoglobin) 23% As Bicarbonate in plasma (Reaction between carbon dioxide and water, catalyzed by carbonic anhydrase)  pH buffer system. 70% of CO2 is transported this way. As Bicarbonate in plasma (Reaction between carbon dioxide and water, catalyzed by carbonic anhydrase)  pH buffer system. 70% of CO2 is transported this way. Chloride shift (Chloride anions diffuse into RBCs to counteract bicarbonate anions leaving RBCs) Chloride shift (Chloride anions diffuse into RBCs to counteract bicarbonate anions leaving RBCs) Process results in diffusion of Oxygen from RBC to tissues and from Carbon dioxide from tissues to RBCs Process results in diffusion of Oxygen from RBC to tissues and from Carbon dioxide from tissues to RBCs This process is reversed in the Lungs This process is reversed in the Lungs

At the Lungs

At the Tissues

Oxygen Transport Molecular oxygen carried in blood or bound to hemoglobin Molecular oxygen carried in blood or bound to hemoglobin HbO2 - hemoglobin bound to oxygen HbO2 - hemoglobin bound to oxygen HHb + O 2 --  HbO2 + H+ HHb + O 2 --  HbO2 + H+ Hb can bind 4 oxygens; after first binding, there is a higher affinity for other 3 Hb can bind 4 oxygens; after first binding, there is a higher affinity for other 3 Hemoglobin is fully saturated when all 4 heme sites bound to oxygen Hemoglobin is fully saturated when all 4 heme sites bound to oxygen

Clinical corner Eupnea - quiet breathing Eupnea - quiet breathing Tachypnea - rapid breathing Tachypnea - rapid breathing Costal breathing - shallow Diaphragmatic breathing - deep Atelectasis - collapse or incomplete expansion of lungs Costal breathing - shallow Diaphragmatic breathing - deep Atelectasis - collapse or incomplete expansion of lungs Cheyne-Stokes respiration - irregular breathing (increase/decrease in depth and rapidity) Cheyne-Stokes respiration - irregular breathing (increase/decrease in depth and rapidity)

Laryngitis - inflammation of the vocal cords Laryngitis - inflammation of the vocal cords Pleurisy - inflammation of the pleura Infant respiratory distress syndrome (IRDS) - insufficient surfactant produced, surface tension forces collapse of the alveoli Pleurisy - inflammation of the pleura Infant respiratory distress syndrome (IRDS) - insufficient surfactant produced, surface tension forces collapse of the alveoli Hypoxia - inadequate amount of oxygen is delivered to body tissues anemic - to few RBCs, or RBCs with inadequate hemoglobin stagnant - blood circulation is impaired or blocked interference with gas exchange Hypoxia - inadequate amount of oxygen is delivered to body tissues anemic - to few RBCs, or RBCs with inadequate hemoglobin stagnant - blood circulation is impaired or blocked interference with gas exchange Hypercapnia - apnea (breathing cessation) increase in carbon dioxide levels in cerebrospinal fluid, causing pH to decrease, exciting chemoreceptors to increase rate of breathing (compensating) Hypercapnia - apnea (breathing cessation) increase in carbon dioxide levels in cerebrospinal fluid, causing pH to decrease, exciting chemoreceptors to increase rate of breathing (compensating) Hypocapnia- low levels of CO2 in plasma and CSF due to depth and rate of breath increase (hyperventilation) Hypocapnia- low levels of CO2 in plasma and CSF due to depth and rate of breath increase (hyperventilation)

Chronic Obstructive Pulmonary Disease (COPD), common features: Chronic Obstructive Pulmonary Disease (COPD), common features: 1- Patients with history of smoking 2- Dyspnea - difficult or labored breathing 3- Coughing and frequent pulmonary infection 4- Will develop respiratory failure COPDs: Obstructive emphysema - permanent enlargement of the alveoli, deterioration of alveolar walls COPDs: Obstructive emphysema - permanent enlargement of the alveoli, deterioration of alveolar walls Chronic inflammation leads to lung fibrosis (lungs lose their elasticity) Chronic inflammation leads to lung fibrosis (lungs lose their elasticity) Victims sometimes called "pink puffers" - breathing is labored, but doesn't become cyanotic because gas exchange remains adequate until late in the disease Victims sometimes called "pink puffers" - breathing is labored, but doesn't become cyanotic because gas exchange remains adequate until late in the disease Chronic bronchitis - inhaled irritants lead to chronic excessive mucus production by the mucosa of lower respiratory passageways and inflammation and fibrosis of that mucosa Chronic bronchitis - inhaled irritants lead to chronic excessive mucus production by the mucosa of lower respiratory passageways and inflammation and fibrosis of that mucosa Victims sometimes called "blue bloaters" - hypoxia and carbon dioxide retention occur Victims sometimes called "blue bloaters" - hypoxia and carbon dioxide retention occur