RESPIRATORY RESPIRATORY PHYSIOLOGYPHYSIOLOGY

Anatomy review

PressuresPressures Atmospheric pressureAtmospheric pressure

Alveolar pressure Alveolar pressure (intrapulmonary (intrapulmonary pressure)pressure)

Intrapleural pressureIntrapleural pressure

Boyle’s LawBoyle’s Law More volume=less More volume=less

pressurepressure Less volume=more Less volume=more

pressurepressure

Diaphragm is chief respiratory muscle Diaphragm is chief respiratory muscle (80%) (80%)

Intercostal muscles are secondary (20%)Intercostal muscles are secondary (20%) - Diaphragm is controlled by phrenic - Diaphragm is controlled by phrenic

nerve (C3,4,5)nerve (C3,4,5)- Range of movement: from 1 cm (normal - Range of movement: from 1 cm (normal

breathing) to 10cm in heavy breathing.breathing) to 10cm in heavy breathing.Parietal pleura attaches to diaphragmParietal pleura attaches to diaphragmVisceral pleura attaches to parietal pleura Visceral pleura attaches to parietal pleura

(thin space in b/w filled with serous fluid)(thin space in b/w filled with serous fluid)Lungs attach to visceral pleura.Lungs attach to visceral pleura.

Inspiration:Inspiration:- Before inspiration pressure in lung equals Before inspiration pressure in lung equals

atmospheric pressure: 760 mm Hg or 1 atmatmospheric pressure: 760 mm Hg or 1 atm- Increasing the size of the lungs will cause Increasing the size of the lungs will cause

pressure to drop and air to rush in. How pressure to drop and air to rush in. How does lung increase in size?does lung increase in size?

- Boyle’s law: the pressure of a gas in a Boyle’s law: the pressure of a gas in a closed container is inversely proportional to closed container is inversely proportional to the volume of the container.the volume of the container.

- incr. in size of container pressure will decrease - incr. in size of container pressure will decrease pressure..pressure..

Intrapleural pressure is 756 mm Hg and during Intrapleural pressure is 756 mm Hg and during inspiration (as diaphragm is pulling down) inspiration (as diaphragm is pulling down) pressure drops to 754 mm Hg.pressure drops to 754 mm Hg.

External intercostals contract and pull rib cage up External intercostals contract and pull rib cage up and forward (anterior) causing a-p diameter to and forward (anterior) causing a-p diameter to increase.increase.

When volume increases, pressure inside lungWhen volume increases, pressure inside lung(alveolar, intrapulmonic pressure) drops from (alveolar, intrapulmonic pressure) drops from 760 to 758. A pressure gradient is established 760 to 758. A pressure gradient is established between the atmosphere and the alveoli.between the atmosphere and the alveoli.

Air rushes in (pressure gradient) to alveoli Air rushes in (pressure gradient) to alveoli from atm.from atm.

Expiration: pressure in lungs is greater than Expiration: pressure in lungs is greater than atm.atm.- diaphragm relaxes and dome shape muscle - diaphragm relaxes and dome shape muscle pushes up (elasticity). Internal intercostals pushes up (elasticity). Internal intercostals cause a-p diameter to decreasecause a-p diameter to decrease- lung pressure increases to 762. Air will flow - lung pressure increases to 762. Air will flow from higher to lower pressures.from higher to lower pressures.

Thoracic Volume and Thoracic Volume and InspirationInspiration

Thoracic Volume and Thoracic Volume and ExpirationExpiration

Changes in Thoracic VolumesChanges in Thoracic Volumes

Factors Influencing Pulmonary Factors Influencing Pulmonary VentilationVentilation

Airway Resistance:Airway Resistance: Amount of drag air encounters in respiratory passageways; Amount of drag air encounters in respiratory passageways;

not significant since airway diameters are large and at not significant since airway diameters are large and at terminal bronchioles gasses travel by diffusionterminal bronchioles gasses travel by diffusion

Surface Tension:Surface Tension: At gas-liquid boundaries, liquids are more attracted to At gas-liquid boundaries, liquids are more attracted to

each other (cohesiveness), each other (cohesiveness), surfacant surfacant at the alveoli keeps at the alveoli keeps water from being cohesive and allows alveoli to be more water from being cohesive and allows alveoli to be more functional (less energy needed for breathing)functional (less energy needed for breathing)

Lung Compliance:Lung Compliance: The distensibility of the lungs, ability to stretch; higher The distensibility of the lungs, ability to stretch; higher

compliance leads to better ventilation (fibrosis, airway compliance leads to better ventilation (fibrosis, airway blockages, decreased surfacant, and decreased thoracic blockages, decreased surfacant, and decreased thoracic cage flexibility lead to less compliance)cage flexibility lead to less compliance)

Respiratory Volumes and Respiratory Volumes and CapacitiesCapacities

Respiratory VolumesRespiratory Volumes Tidal Volume:Tidal Volume:

The amount of air that moves in and out of the lungs The amount of air that moves in and out of the lungs with a normal breath at rest (~500 mL)with a normal breath at rest (~500 mL)

Inspiratory Reserve Volume:Inspiratory Reserve Volume: The amount of air that can be inspired forcibly The amount of air that can be inspired forcibly

beyond the tidal volume (2100-3200 mL)beyond the tidal volume (2100-3200 mL) Expiratory Reserve Volume:Expiratory Reserve Volume:

The amount of air that can be expired forcibly beyond The amount of air that can be expired forcibly beyond a tidal expiration (1000-1200 mL)a tidal expiration (1000-1200 mL)

Residual Volume:Residual Volume: The amount of air remaining in the lungs even after The amount of air remaining in the lungs even after

the most forceful expiration (1200 mL)the most forceful expiration (1200 mL)

Respiratory CapacitiesRespiratory Capacities Inspiratory Capacity:Inspiratory Capacity:

Total amount of air that can be inspired after a Total amount of air that can be inspired after a tidal expiration; TV + IRVtidal expiration; TV + IRV

Functional Residual Capacity:Functional Residual Capacity: Total amount of air remaining in lungs after a Total amount of air remaining in lungs after a

tidal expiration; ERV + RVtidal expiration; ERV + RV Vital Capacity:Vital Capacity:

Total amount of exchangeable air; TV + IRV + Total amount of exchangeable air; TV + IRV + ERVERV

Total Lung Capacity:Total Lung Capacity: Sum of all lung volumesSum of all lung volumes

Volumes and CapacitiesVolumes and Capacities

Dead SpaceDead Space Anatomical dead space:Anatomical dead space:

The volume of air found in the conduits of the The volume of air found in the conduits of the respiratory system NOT involved in gas respiratory system NOT involved in gas exchangeexchange

Alveolar dead space:Alveolar dead space: Regions where alveoli cease to function due to Regions where alveoli cease to function due to

collapse or obstructioncollapse or obstruction

Total dead space: Total dead space: Alveolar dead space + Anatomical dead spaceAlveolar dead space + Anatomical dead space

Non-Respiratory Air Non-Respiratory Air MovementsMovements

CoughCough

SneezeSneeze

CryingCrying

LaughingLaughing

HiccupsHiccups

YawnYawn

Regulation of RespirationRegulation of Respiration Medullary respiratory Medullary respiratory

centercenter Dorsal respiratory Dorsal respiratory

center (DRC)center (DRC) Ventral respiratory Ventral respiratory

center (VRC)center (VRC)

Pontine center Pontine center formerly called the formerly called the Pneumotaxic centerPneumotaxic center

HypothalamusHypothalamus

Gas TransportGas Transport Oxyhemoglobin: HbOOxyhemoglobin: HbO22 Deoxyhemoglobin: HHbDeoxyhemoglobin: HHb Carbaminohemoglobin: HbCOCarbaminohemoglobin: HbCO22

External Respiration:External Respiration:Oxygen and Carbon Dioxide concentration is Oxygen and Carbon Dioxide concentration is

measured as a unit of pressure called measured as a unit of pressure called partial pressure (p)partial pressure (p)

Blood coming into the lungs (pulmonary Blood coming into the lungs (pulmonary artery-capillary) is deoxygenated blood= artery-capillary) is deoxygenated blood= POPO22 is 40 mm Hg. PCO is 40 mm Hg. PCO22 is 45 mm Hg is 45 mm Hg

Air in the alveoli:Air in the alveoli:POPO22= 105 mm Hg= 105 mm HgPCOPCO22= 40 mm Hg= 40 mm Hg

Oxygen and Carbon dioxide are highly fat Oxygen and Carbon dioxide are highly fat soluble and can diffuse through soluble and can diffuse through membranes with ease.membranes with ease.

As gases pass from the blood pass an As gases pass from the blood pass an alveolus gases will diffuse from areas of alveolus gases will diffuse from areas of higher concentration to lower. (diffusion higher concentration to lower. (diffusion gradients)gradients)

POPO22 in blood after passing alveolus is 105 in blood after passing alveolus is 105 mm Hgmm Hg

PCOPCO22 in blood after passing alveolus is 40 in blood after passing alveolus is 40 mm Hgmm Hg

Internal respiration: Exchange of Internal respiration: Exchange of gases in the tissues.gases in the tissues.

COCO22 is a byproduct of cellular is a byproduct of cellular metabolism.metabolism.

PCOPCO22 in tissue space: 45 mm Hg in tissue space: 45 mm HgPOPO22 in tissue spaces: 40 mm Hg in tissue spaces: 40 mm HgO2 will diffuse into tissue spaces (105) O2 will diffuse into tissue spaces (105)

and CO2 will diffuse into blood (45)and CO2 will diffuse into blood (45)

Gas Transport at the TissuesGas Transport at the Tissues Carbon dioxide transported to and from the lungs Carbon dioxide transported to and from the lungs

and tissues in three ways:and tissues in three ways: Dissolved in plasma 7%Dissolved in plasma 7% Chemically bound to hemoglobin (carbaminohemoglobin) Chemically bound to hemoglobin (carbaminohemoglobin)

23%23% As Bicarbonate in plasma (Reaction between carbon As Bicarbonate in plasma (Reaction between carbon

dioxide and water, catalyzed by carbonic anhydrase) dioxide and water, catalyzed by carbonic anhydrase) pH buffer system. 70% of CO2 is transported this way.pH buffer system. 70% of CO2 is transported this way.

Chloride shift (Chloride anions diffuse into RBCs to Chloride shift (Chloride anions diffuse into RBCs to counteract bicarbonate anions leaving RBCs)counteract bicarbonate anions leaving RBCs)

Process results in diffusion of Oxygen from RBC to Process results in diffusion of Oxygen from RBC to tissues and from Carbon dioxide from tissues to tissues and from Carbon dioxide from tissues to RBCsRBCs

This process is reversed in the LungsThis process is reversed in the Lungs

At the LungsAt the Lungs

At the TissuesAt the Tissues

Oxygen TransportOxygen Transport Molecular oxygen carried in blood or Molecular oxygen carried in blood or

bound to hemoglobinbound to hemoglobin HbO2HbO2-- hemoglobin bound to oxygen hemoglobin bound to oxygen HHb + OHHb + O2 2 ---- HbO2 + H+ HbO2 + H+ Hb can bind 4 oxygens; after first binding, Hb can bind 4 oxygens; after first binding,

there is a higher affinity for other 3there is a higher affinity for other 3 Hemoglobin is fully saturated when all 4 Hemoglobin is fully saturated when all 4

heme sites bound to oxygenheme sites bound to oxygen

Clinical cornerClinical corner EupneaEupnea - quiet breathing - quiet breathing TachypneaTachypnea - rapid breathing - rapid breathing Costal breathingCostal breathing - shallow - shallow

Diaphragmatic breathingDiaphragmatic breathing - deep - deep AtelectasisAtelectasis - collapse or incomplete - collapse or incomplete expansion of lungs expansion of lungs

Cheyne-Stokes respirationCheyne-Stokes respiration - - irregular breathing irregular breathing (increase/decrease in depth and (increase/decrease in depth and rapidity) rapidity)

LaryngitisLaryngitis - inflammation of the vocal cords - inflammation of the vocal cords PleurisyPleurisy - inflammation of the pleura - inflammation of the pleura Infant Infant

respiratory distress syndrome (IRDS) respiratory distress syndrome (IRDS) - - insufficient surfactant produced, surface tension insufficient surfactant produced, surface tension forces collapse of the alveoliforces collapse of the alveoli

HypoxiaHypoxia - inadequate amount of oxygen is - inadequate amount of oxygen is delivered to body tissues anemic - to few RBCs, or delivered to body tissues anemic - to few RBCs, or RBCs with inadequate hemoglobin stagnant - blood RBCs with inadequate hemoglobin stagnant - blood circulation is impaired or blocked interference with circulation is impaired or blocked interference with gas exchange gas exchange

HypercapniaHypercapnia - apnea (breathing cessation) increase - apnea (breathing cessation) increase in carbon dioxide levels in cerebrospinal fluid, in carbon dioxide levels in cerebrospinal fluid, causing pH to decrease, exciting chemoreceptors to causing pH to decrease, exciting chemoreceptors to increase rate of breathing (compensating)increase rate of breathing (compensating)

Hypocapnia- Hypocapnia- low levels of CO2 in plasma and CSF low levels of CO2 in plasma and CSF due to depth and rate of breath increase due to depth and rate of breath increase (hyperventilation) (hyperventilation)

Chronic Obstructive Pulmonary Disease (COPD)Chronic Obstructive Pulmonary Disease (COPD), common , common features: features:

1- Patients with history of smoking 1- Patients with history of smoking 2- Dyspnea - difficult or labored breathing 2- Dyspnea - difficult or labored breathing 3- Coughing and frequent pulmonary infection3- Coughing and frequent pulmonary infection4- Will develop respiratory failure4- Will develop respiratory failure COPDs: COPDs: Obstructive emphysemaObstructive emphysema - permanent enlargement - permanent enlargement

of the alveoli, deterioration of alveolar wallsof the alveoli, deterioration of alveolar walls Chronic inflammation leads to lung fibrosis (lungs lose their Chronic inflammation leads to lung fibrosis (lungs lose their

elasticity) elasticity) Victims sometimes called "pink puffers" - breathing is Victims sometimes called "pink puffers" - breathing is

labored, but doesn't become cyanotic because gas labored, but doesn't become cyanotic because gas exchange remains adequate until late in the diseaseexchange remains adequate until late in the disease

Chronic bronchitisChronic bronchitis - inhaled irritants lead to chronic - inhaled irritants lead to chronic excessive mucus production by the mucosa of lower respiratory excessive mucus production by the mucosa of lower respiratory passageways and inflammation and fibrosis of that mucosapassageways and inflammation and fibrosis of that mucosa Victims sometimes called "blue bloaters" - hypoxia and Victims sometimes called "blue bloaters" - hypoxia and

carbon dioxide retention occurcarbon dioxide retention occur