respiratory volumes

Respiratory VolumesRespiratory Volumes Tidal volume (TV) – air that moves into and Tidal volume (TV) – air that moves into and

out of the lungs with each breath out of the lungs with each breath (approximately 500 ml)(approximately 500 ml)

Inspiratory reserve volume (IRV) – air that can Inspiratory reserve volume (IRV) – air that can be inspired forcibly beyond the tidal volume be inspired forcibly beyond the tidal volume (2100–3200 ml)(2100–3200 ml)

Expiratory reserve volume (ERV) – air that Expiratory reserve volume (ERV) – air that can be evacuated from the lungs after a tidal can be evacuated from the lungs after a tidal expiration (1000–1200 ml)expiration (1000–1200 ml)

Residual volume (RV) – air left in the lungs Residual volume (RV) – air left in the lungs after strenuous expiration (1200 ml)after strenuous expiration (1200 ml)

Respiratory CapacitiesRespiratory Capacities

Inspiratory capacity (IC) – total amount of air that Inspiratory capacity (IC) – total amount of air that can be inspired after a tidal expiration (IRV + TV)can be inspired after a tidal expiration (IRV + TV)

Functional residual capacity (FRC) – amount of air Functional residual capacity (FRC) – amount of air remaining in the lungs after a tidal expiration remaining in the lungs after a tidal expiration (RV + ERV)(RV + ERV)

Vital capacity (VC) – the total amount of Vital capacity (VC) – the total amount of exchangeable air (TV + IRV + ERV)exchangeable air (TV + IRV + ERV)

Total lung capacity (TLC) – sum of all lung volumes Total lung capacity (TLC) – sum of all lung volumes (approximately 6000 ml in males); also described as (approximately 6000 ml in males); also described as the total amount of gases contained within the lungsthe total amount of gases contained within the lungs

Dead SpaceDead Space

Anatomical dead space – volume of the Anatomical dead space – volume of the conducting respiratory passages (150 ml)conducting respiratory passages (150 ml)

Alveolar dead space – alveoli that cease to act Alveolar dead space – alveoli that cease to act in gas exchange due to collapse or obstructionin gas exchange due to collapse or obstruction

Total dead space – sum of alveolar and Total dead space – sum of alveolar and anatomical dead spacesanatomical dead spaces

Pulmonary Function TestsPulmonary Function Tests

Spirometer – an instrument consisting of a Spirometer – an instrument consisting of a hollow bell inverted over water, used to hollow bell inverted over water, used to evaluate respiratory functionevaluate respiratory function

Spirometry can distinguish between: Spirometry can distinguish between: Obstructive pulmonary disease – increased airway Obstructive pulmonary disease – increased airway

resistanceresistance Restrictive disorders – reduction in total lung Restrictive disorders – reduction in total lung

capacity from structural or functional lung changes capacity from structural or functional lung changes

SpirometerSpirometer


Total ventilation – total amount of gas flow Total ventilation – total amount of gas flow into or out of the respiratory tract in one into or out of the respiratory tract in one minuteminute

Forced vital capacity (FVC) – gas forcibly Forced vital capacity (FVC) – gas forcibly expelled after taking a deep breathexpelled after taking a deep breath

Forced expiratory volume (FEV) – the amount Forced expiratory volume (FEV) – the amount of gas expelled during specific time intervals of gas expelled during specific time intervals of the FVCof the FVC


Increases in TLC (total lung capacity), FRC Increases in TLC (total lung capacity), FRC (functional residual capacity), and RV (functional residual capacity), and RV (residual volume) may occur as a result of (residual volume) may occur as a result of obstructive diseaseobstructive disease

Reduction in VC, TLC, FRC, and RV result Reduction in VC, TLC, FRC, and RV result from restrictive diseasefrom restrictive disease

Alveolar VentilationAlveolar Ventilation

Alveolar ventilation rate (AVR) – measures Alveolar ventilation rate (AVR) – measures the flow of fresh gases into and out of the the flow of fresh gases into and out of the alveoli during a particular time, typically 1 alveoli during a particular time, typically 1 minuteminute

Slow, deep breathing increases AVR and Slow, deep breathing increases AVR and rapid, shallow breathing decreases AVRrapid, shallow breathing decreases AVR

Nonrespiratory Air MovementsNonrespiratory Air Movements

Most result from reflex actionMost result from reflex action Are used to clear airways, express emotions, Are used to clear airways, express emotions,

speak, etc.speak, etc. Examples include: coughing, sneezing, crying, Examples include: coughing, sneezing, crying,

laughing, hiccupping, and yawninglaughing, hiccupping, and yawning

Basic Properties of Gases: Basic Properties of Gases: Dalton’s Law of Partial Dalton’s Law of Partial

PressuresPressures

Total pressure exerted by a mixture of gases is Total pressure exerted by a mixture of gases is the sum of the pressures exerted independently the sum of the pressures exerted independently by each gas in the mixtureby each gas in the mixture

The partial pressure of each gas is directly The partial pressure of each gas is directly proportional to its percentage in the mixtureproportional to its percentage in the mixture

When a mixture of gases is in contact with a When a mixture of gases is in contact with a liquid, each gas will dissolve in the liquid in liquid, each gas will dissolve in the liquid in proportion to its partial pressureproportion to its partial pressure

The amount of gas that will dissolve in a liquid The amount of gas that will dissolve in a liquid also depends upon its solubility:also depends upon its solubility: Carbon dioxide is the most solubleCarbon dioxide is the most soluble Oxygen is 1/20Oxygen is 1/20thth as soluble as carbon dioxide as soluble as carbon dioxide Nitrogen is practically insoluble in plasmaNitrogen is practically insoluble in plasma

Basic Properties of Gases: Basic Properties of Gases: Henry’s LawHenry’s Law

Composition of Alveolar GasComposition of Alveolar Gas

The atmosphere is mostly oxygen and The atmosphere is mostly oxygen and nitrogen, while alveoli contain more carbon nitrogen, while alveoli contain more carbon dioxide and water vapordioxide and water vapor

These differences result from:These differences result from: Gas exchanges in the lungs – oxygen diffuses from Gas exchanges in the lungs – oxygen diffuses from

the alveoli and carbon dioxide diffuses into the the alveoli and carbon dioxide diffuses into the alveolialveoli

Humidification of air by conducting passagesHumidification of air by conducting passages The mixing of alveolar gas that occurs with each The mixing of alveolar gas that occurs with each

breath breath

External Respiration: Pulmonary External Respiration: Pulmonary Gas ExchangeGas Exchange

Factors influencing the movement of oxygen Factors influencing the movement of oxygen and carbon dioxide across the respiratory and carbon dioxide across the respiratory membranemembrane Partial pressure gradients and gas solubilitiesPartial pressure gradients and gas solubilities Matching of alveolar ventilation and pulmonary Matching of alveolar ventilation and pulmonary

blood perfusionblood perfusion Structural characteristics of the respiratory Structural characteristics of the respiratory

membranemembrane

Partial Pressure Gradients and Partial Pressure Gradients and Gas SolubilitiesGas Solubilities

The partial pressure oxygen (POThe partial pressure oxygen (PO22) of venous ) of venous

blood is 40 mm Hg; the partial pressure in the blood is 40 mm Hg; the partial pressure in the alveoli is 104 mm Hgalveoli is 104 mm Hg This steep gradient shows that oxygen partial This steep gradient shows that oxygen partial

pressures reaches equilibrium (high enough pressure pressures reaches equilibrium (high enough pressure is achieved that O2 can move into the blood vessels) is achieved that O2 can move into the blood vessels) rapidly, and thus blood can move very rapidly rapidly, and thus blood can move very rapidly through the pulmonary capillary and still be through the pulmonary capillary and still be adequately oxygenatedadequately oxygenated

Partial Pressure Gradients and Partial Pressure Gradients and Gas SolubilitiesGas Solubilities

Although carbon dioxide has a lower partial Although carbon dioxide has a lower partial pressure gradient:pressure gradient: It is 20 times more soluble in plasma than oxygenIt is 20 times more soluble in plasma than oxygen It diffuses in equal amounts with oxygen It diffuses in equal amounts with oxygen

Ventilation-Perfusion CouplingVentilation-Perfusion Coupling

Ventilation – the amount of gas reaching the Ventilation – the amount of gas reaching the alveolialveoli

Perfusion – the blood flow reaching the alveoliPerfusion – the blood flow reaching the alveoli Ventilation and perfusion must be tightly Ventilation and perfusion must be tightly

regulated for efficient gas exchangeregulated for efficient gas exchange

Ventilation-Perfusion CouplingVentilation-Perfusion Coupling

Changes in PChanges in PCO2CO2 (partial pressure of CO2) in (partial pressure of CO2) in

the alveoli cause changes in the diameters of the alveoli cause changes in the diameters of the bronchiolesthe bronchioles Passageways servicing areas where alveolar Passageways servicing areas where alveolar

carbon dioxide is high dilatecarbon dioxide is high dilate Those serving areas where alveolar carbon dioxide Those serving areas where alveolar carbon dioxide

is low constrictis low constrict

Surface Area and Thickness of Surface Area and Thickness of the Respiratory Membranethe Respiratory Membrane

Respiratory membranes:Respiratory membranes: Are only 0.5 to 1 Are only 0.5 to 1 m thick, allowing for efficient m thick, allowing for efficient

gas exchangegas exchange Have a total surface area (in males) of about 60 mHave a total surface area (in males) of about 60 m22

(40 times that of one’s skin)(40 times that of one’s skin) Thicken if lungs become waterlogged and Thicken if lungs become waterlogged and

edematous, whereby gas exchange is inadequate edematous, whereby gas exchange is inadequate and oxygen deprivation resultsand oxygen deprivation results

Decrease in surface area with emphysema, when Decrease in surface area with emphysema, when walls of adjacent alveoli break throughwalls of adjacent alveoli break through

Internal RespirationInternal Respiration

The factors promoting gas exchange between The factors promoting gas exchange between systemic capillaries and tissue cells are the systemic capillaries and tissue cells are the same as those acting in the lungssame as those acting in the lungs The partial pressures and diffusion gradients are The partial pressures and diffusion gradients are

reversedreversed PPO2O2 in tissue is always lower than in systemic in tissue is always lower than in systemic

arterial bloodarterial blood PPO2O2 of venous blood draining tissues is 40 mm Hg of venous blood draining tissues is 40 mm Hg

and Pand PCO2CO2 is 45 mm Hg is 45 mm Hg

Oxygen TransportOxygen Transport

Molecular oxygen is carried in the blood: Molecular oxygen is carried in the blood: Bound to hemoglobin (Hb) within red blood cells Bound to hemoglobin (Hb) within red blood cells Dissolved in plasmaDissolved in plasma

Each Hb molecule binds four oxygen atoms in Each Hb molecule binds four oxygen atoms in a rapid and reversible processa rapid and reversible process

The hemoglobin-oxygen combination is called The hemoglobin-oxygen combination is called oxyhemoglobin (HbOoxyhemoglobin (HbO22))

Hemoglobin that has released oxygen is called Hemoglobin that has released oxygen is called reduced hemoglobin (HHb)reduced hemoglobin (HHb)

Oxygen Transport: Role of Oxygen Transport: Role of HemoglobinHemoglobin

HHb + O2

Lungs

Tissues

HbO2 + H+

Hemoglobin (Hb)Hemoglobin (Hb)

Saturated hemoglobin – when all four hemes Saturated hemoglobin – when all four hemes of the molecule are bound to oxygenof the molecule are bound to oxygen

Partially saturated hemoglobin – when one to Partially saturated hemoglobin – when one to three hemes are bound to oxygenthree hemes are bound to oxygen

The rate that hemoglobin binds and releases The rate that hemoglobin binds and releases oxygen is regulated by:oxygen is regulated by: PPO2O2, temperature, blood pH, P, temperature, blood pH, PCO2CO2, and the , and the

concentration of BPG (an organic chemical)concentration of BPG (an organic chemical) These factors ensure adequate delivery of oxygen to These factors ensure adequate delivery of oxygen to

tissue cellstissue cells

Influence of PInfluence of PO2O2 on Hemoglobin on Hemoglobin

SaturationSaturation 98% saturated arterial blood contains 20 ml 98% saturated arterial blood contains 20 ml

oxygen per 100 ml blood (20 vol %)oxygen per 100 ml blood (20 vol %) As arterial blood flows through capillaries, 5 As arterial blood flows through capillaries, 5

ml oxygen are releasedml oxygen are released The saturation of hemoglobin in arterial blood The saturation of hemoglobin in arterial blood

explains why breathing deeply increases the explains why breathing deeply increases the PPO2O2 but has little effect on oxygen saturation in but has little effect on oxygen saturation in hemoglobinhemoglobin

Hemoglobin Saturation CurveHemoglobin Saturation Curve

Hemoglobin is almost completely saturated at Hemoglobin is almost completely saturated at a Pa PO2O2 of 70 mm Hg of 70 mm Hg

Further increases in PFurther increases in PO2O2 produce only small produce only small

increases in oxygen bindingincreases in oxygen binding Oxygen loading and delivery to tissue is Oxygen loading and delivery to tissue is

adequate when Padequate when PO2O2 is below normal levels is below normal levels

Only 20–25% of bound oxygen is unloaded Only 20–25% of bound oxygen is unloaded during one systemic circulationduring one systemic circulation

If oxygen levels in tissues drop:If oxygen levels in tissues drop: More oxygen dissociates from hemoglobin and is More oxygen dissociates from hemoglobin and is

used by cells used by cells Respiratory rate or cardiac output need not Respiratory rate or cardiac output need not

increaseincrease

Hemoglobin Saturation CurveHemoglobin Saturation Curve

Other Factors Influencing Other Factors Influencing Hemoglobin SaturationHemoglobin Saturation

Temperature, HTemperature, H++, P, PCO2CO2, and BPG, and BPG Modify the structure of hemoglobin and alter its Modify the structure of hemoglobin and alter its

affinity for oxygenaffinity for oxygen Increases of these factors:Increases of these factors:

Decrease hemoglobin’s affinity for oxygenDecrease hemoglobin’s affinity for oxygen Enhance oxygen unloading from the bloodEnhance oxygen unloading from the blood

Decreases act in the opposite mannerDecreases act in the opposite manner These parameters are all high in systemic These parameters are all high in systemic

capillaries where oxygen unloading is the goalcapillaries where oxygen unloading is the goal

Factors That Increase Release of Factors That Increase Release of Oxygen by HemoglobinOxygen by Hemoglobin

As cells metabolize glucose, carbon dioxide is As cells metabolize glucose, carbon dioxide is released into the blood causing:released into the blood causing: Increases in PIncreases in PCO2CO2 and H and H++ concentration in capillary concentration in capillary

bloodblood Declining pH (acidosis), which weakens the Declining pH (acidosis), which weakens the

hemoglobin-oxygen bond (Bohr effect)hemoglobin-oxygen bond (Bohr effect) Metabolizing cells have heat as a byproduct and Metabolizing cells have heat as a byproduct and

the rise in temperature increases BPG synthesisthe rise in temperature increases BPG synthesis All these factors ensure oxygen unloading in All these factors ensure oxygen unloading in

the vicinity of working tissue cellsthe vicinity of working tissue cells

Nitric oxide (NO) is a vasodilator that plays a role in blood Nitric oxide (NO) is a vasodilator that plays a role in blood pressure regulationpressure regulation

NO is free radical, a by-product of combustion (as from NO is free radical, a by-product of combustion (as from automobiles) and has a very short half life (a few seconds) automobiles) and has a very short half life (a few seconds) in the bloodin the blood

Hemoglobin is a vasoconstrictor and a nitric oxide Hemoglobin is a vasoconstrictor and a nitric oxide scavenger (heme destroys NO)scavenger (heme destroys NO)

However, as oxygen binds to hemoglobin:However, as oxygen binds to hemoglobin: Nitric oxide binds to a amino acid on hemoglobin Nitric oxide binds to a amino acid on hemoglobin

(cysteine)(cysteine) Bound nitric oxide is protected from degradation by Bound nitric oxide is protected from degradation by

hemoglobin’s ironhemoglobin’s iron

Hemoglobin-Nitric Oxide Hemoglobin-Nitric Oxide PartnershipPartnership

Hemoglobin-Nitric Oxide Hemoglobin-Nitric Oxide PartnershipPartnership

The hemoglobin is released as oxygen is The hemoglobin is released as oxygen is unloaded, causing vasodilationunloaded, causing vasodilation

As deoxygenated hemoglobin picks up carbon As deoxygenated hemoglobin picks up carbon dioxide, it also binds nitric oxide and carries dioxide, it also binds nitric oxide and carries these gases to the lungs for unloadingthese gases to the lungs for unloading

Carbon Dioxide TransportCarbon Dioxide Transport

Carbon dioxide is transported in the blood in Carbon dioxide is transported in the blood in three formsthree forms Dissolved in plasma – 7 to 10% Dissolved in plasma – 7 to 10% Chemically bound to hemoglobin – 20% is carried Chemically bound to hemoglobin – 20% is carried

in RBCs as carbaminohemoglobinin RBCs as carbaminohemoglobin Bicarbonate ion in plasma – 70% is transported as Bicarbonate ion in plasma – 70% is transported as

bicarbonate (HCObicarbonate (HCO33––) )

COCO22 ++ HH22OO HH22COCO33 HH++ ++ HCOHCO33––

Carbon Carbon dioxidedioxide

WaterWaterCarbonic Carbonic

acidacidHydrogen Hydrogen

ionionBicarbonate Bicarbonate

ionion

Transport and Exchange of Transport and Exchange of Carbon DioxideCarbon Dioxide

Carbon dioxide diffuses into RBCs and combines Carbon dioxide diffuses into RBCs and combines with water to form carbonic acid (Hwith water to form carbonic acid (H22COCO33), which ), which quickly dissociates into hydrogen ions and quickly dissociates into hydrogen ions and bicarbonate ionsbicarbonate ions

In RBCs, carbonic anhydrase reversibly catalyzes the In RBCs, carbonic anhydrase reversibly catalyzes the conversion of carbon dioxide and water to carbonic conversion of carbon dioxide and water to carbonic acidacid


At the tissues:At the tissues: Bicarbonate quickly diffuses from RBCs into the Bicarbonate quickly diffuses from RBCs into the

plasmaplasma The chloride shift – to counterbalance the outrush The chloride shift – to counterbalance the outrush

of negative bicarbonate ions from the RBCs, of negative bicarbonate ions from the RBCs, chloride ions (Clchloride ions (Cl––) move from the plasma into the ) move from the plasma into the erythrocyteserythrocytes


At the lungs, these processes are reversedAt the lungs, these processes are reversed Bicarbonate ions move into the RBCs and bind Bicarbonate ions move into the RBCs and bind

with hydrogen ions to form carbonic acidwith hydrogen ions to form carbonic acid Carbonic acid is then split by carbonic anhydrase Carbonic acid is then split by carbonic anhydrase

to release carbon dioxide and waterto release carbon dioxide and water Carbon dioxide then diffuses from the blood into Carbon dioxide then diffuses from the blood into

the alveolithe alveoli

Haldane EffectHaldane Effect

The amount of carbon dioxide transported is The amount of carbon dioxide transported is markedly affected by the Pmarkedly affected by the PO2O2

Haldane effect – the lower the PHaldane effect – the lower the PO2O2 and and

hemoglobin saturation with oxygen, the more hemoglobin saturation with oxygen, the more carbon dioxide can be carried in the bloodcarbon dioxide can be carried in the blood

Haldane EffectHaldane Effect

At the tissues, as more carbon dioxide enters At the tissues, as more carbon dioxide enters the blood:the blood: More oxygen dissociates from hemoglobin (Bohr More oxygen dissociates from hemoglobin (Bohr

effect)effect) More carbon dioxide combines with hemoglobin, More carbon dioxide combines with hemoglobin,

and more bicarbonate ions are formedand more bicarbonate ions are formed This situation is reversed in pulmonary This situation is reversed in pulmonary

circulationcirculation

Influence of Carbon Dioxide on Influence of Carbon Dioxide on Blood pHBlood pH

The carbonic acid–bicarbonate buffer system The carbonic acid–bicarbonate buffer system resists blood pH changesresists blood pH changes

If hydrogen ion concentrations in blood begin If hydrogen ion concentrations in blood begin to rise, excess Hto rise, excess H++ is removed by combining is removed by combining with HCOwith HCO33

–– If hydrogen ion concentrations begin to drop, If hydrogen ion concentrations begin to drop,

carbonic acid dissociates, releasing Hcarbonic acid dissociates, releasing H++

Influence of Carbon Dioxide on Influence of Carbon Dioxide on Blood pHBlood pH

Changes in respiratory rate can also:Changes in respiratory rate can also: Alter blood pH Alter blood pH Provide a fast-acting system to adjust pH when it Provide a fast-acting system to adjust pH when it

is disturbed by metabolic factorsis disturbed by metabolic factors

Control of Respiration: Control of Respiration: Medullary Respiratory CentersMedullary Respiratory Centers

The dorsal respiratory group (DRG), or The dorsal respiratory group (DRG), or inspiratory center: inspiratory center: Is located near the root of nerve IX Is located near the root of nerve IX Appears to be the pacesetting respiratory centerAppears to be the pacesetting respiratory center Excites the inspiratory muscles and sets eupnea Excites the inspiratory muscles and sets eupnea

(12-18 breaths/minute)(12-18 breaths/minute) Becomes dormant during expirationBecomes dormant during expiration

The ventral respiratory group (VRG) is The ventral respiratory group (VRG) is involved in forced inspiration and expirationinvolved in forced inspiration and expiration

Control of Respiration: Control of Respiration: Pons Respiratory CentersPons Respiratory Centers

Pons centers:Pons centers: Influence and modify activity of the medullary Influence and modify activity of the medullary

centerscenters Smooth out inspiration and expiration transitions Smooth out inspiration and expiration transitions

and vice versaand vice versa The pontine respiratory group (PRG) – The pontine respiratory group (PRG) –

continuously inhibits the inspiration center, continuously inhibits the inspiration center, cyclically, by limiting the action potentials of cyclically, by limiting the action potentials of the phrenic nervethe phrenic nerve

Respiratory RhythmRespiratory Rhythm

A result of reciprocal inhibition of the A result of reciprocal inhibition of the interconnected neuronal networks in the interconnected neuronal networks in the medullamedulla

Other theories includeOther theories include Inspiratory neurons are pacemakers and have Inspiratory neurons are pacemakers and have

intrinsic automaticity and rhythmicityintrinsic automaticity and rhythmicity Stretch receptors in the lungs may help establish Stretch receptors in the lungs may help establish

respiratory rhythmrespiratory rhythm

Depth and Rate of BreathingDepth and Rate of Breathing

Inspiratory depth is determined by how Inspiratory depth is determined by how actively the respiratory center stimulates the actively the respiratory center stimulates the respiratory musclesrespiratory muscles

Rate of respiration is determined by how long Rate of respiration is determined by how long the inspiratory center is activethe inspiratory center is active

Respiratory centers in the pons and medulla Respiratory centers in the pons and medulla are sensitive to both excitatory and inhibitory are sensitive to both excitatory and inhibitory stimulistimuli

Depth and Rate of Breathing: Depth and Rate of Breathing: ReflexesReflexes

Pulmonary irritant reflexes – irritants promote Pulmonary irritant reflexes – irritants promote reflexive constriction of air passagesreflexive constriction of air passages

Inflation reflex (Hering-Breuer) – stretch Inflation reflex (Hering-Breuer) – stretch receptors in the lungs are stimulated by lung receptors in the lungs are stimulated by lung inflation inflation

Upon inflation, inhibitory signals are sent to Upon inflation, inhibitory signals are sent to the medullary inspiration center to end the medullary inspiration center to end inhalation and allow expirationinhalation and allow expiration

Depth and Rate of Breathing: Depth and Rate of Breathing: Higher Brain CentersHigher Brain Centers

Hypothalamic controls act through the limbic Hypothalamic controls act through the limbic system to modify rate and depth of respiration system to modify rate and depth of respiration Example: breath holding that occurs in angerExample: breath holding that occurs in anger

A rise in body temperature acts to increase A rise in body temperature acts to increase respiratory raterespiratory rate

Cortical controls are direct signals from the Cortical controls are direct signals from the cerebral motor cortex that bypass medullary cerebral motor cortex that bypass medullary controlscontrols Examples: voluntary breath holding, taking a deep Examples: voluntary breath holding, taking a deep

breathbreath

Depth and Rate of Breathing: Depth and Rate of Breathing: PPCO2CO2

Changing PChanging PCO2CO2 levels are monitored by levels are monitored by

chemoreceptors of the brain stemchemoreceptors of the brain stem Carbon dioxide in the blood diffuses into the Carbon dioxide in the blood diffuses into the

cerebrospinal fluid where it is hydratedcerebrospinal fluid where it is hydrated Resulting carbonic acid dissociates, releasing Resulting carbonic acid dissociates, releasing

hydrogen ionshydrogen ions PPCO2CO2 levels rise (hypercapnia) resulting in levels rise (hypercapnia) resulting in

increased depth and rate of breathing increased depth and rate of breathing


Hyperventilation – increased depth and rate of Hyperventilation – increased depth and rate of breathing that:breathing that: Quickly flushes carbon dioxide from the bloodQuickly flushes carbon dioxide from the blood Occurs in response to hypercapnia (too much CO2 Occurs in response to hypercapnia (too much CO2

in the blood stream) or emotional distressin the blood stream) or emotional distress

Though a rise COThough a rise CO2 2 acts as the original acts as the original

stimulus, control of breathing at rest is stimulus, control of breathing at rest is regulated by the hydrogen ion concentration in regulated by the hydrogen ion concentration in the brainthe brain


Hypoventilation – slow and shallow breathing Hypoventilation – slow and shallow breathing due to abnormally low Pdue to abnormally low PCO2CO2 levels levels Apnea (breathing cessation) may occur until PApnea (breathing cessation) may occur until PCO2CO2

levels riselevels rise

Arterial oxygen levels are monitored by the aortic and Arterial oxygen levels are monitored by the aortic and carotid bodies carotid bodies

Substantial drops in arterial PSubstantial drops in arterial PO2O2 (to 60 mm Hg) are (to 60 mm Hg) are

needed before oxygen levels become a major stimulus needed before oxygen levels become a major stimulus for increased ventilationfor increased ventilation

If carbon dioxide is not removed (e.g., as in If carbon dioxide is not removed (e.g., as in emphysema and chronic bronchitis), chemoreceptors emphysema and chronic bronchitis), chemoreceptors become unresponsive to Pbecome unresponsive to PCO2CO2 chemical stimuli chemical stimuli

In such cases, PIn such cases, PO2O2 levels become the principal levels become the principal

respiratory stimulus (hypoxic drive)respiratory stimulus (hypoxic drive)


Depth and Rate of Breathing: Depth and Rate of Breathing: Arterial pHArterial pH

Changes in arterial pH can modify respiratory Changes in arterial pH can modify respiratory rate even if carbon dioxide and oxygen levels rate even if carbon dioxide and oxygen levels are normalare normal

Increased ventilation in response to falling pH Increased ventilation in response to falling pH is mediated by peripheral chemoreceptorsis mediated by peripheral chemoreceptors

Depth and Rate of Breathing: Depth and Rate of Breathing: Arterial pHArterial pH

Acidosis may reflect: Acidosis may reflect: Carbon dioxide retentionCarbon dioxide retention Accumulation of lactic acidAccumulation of lactic acid Excess fatty acids in patients with diabetes Excess fatty acids in patients with diabetes

mellitusmellitus Respiratory system controls will attempt to Respiratory system controls will attempt to

raise the pH by increasing respiratory rate and raise the pH by increasing respiratory rate and depthdepth

Respiratory Adjustments: Respiratory Adjustments: ExerciseExercise

Respiratory adjustments are geared to both the Respiratory adjustments are geared to both the intensity and duration of exerciseintensity and duration of exercise

During vigorous exercise:During vigorous exercise: Ventilation can increase 20 fold Ventilation can increase 20 fold Breathing becomes deeper and more vigorous, but Breathing becomes deeper and more vigorous, but

respiratory rate may not be significantly changed respiratory rate may not be significantly changed (hyperpnea)(hyperpnea)

Exercise-enhanced breathing is not prompted by an Exercise-enhanced breathing is not prompted by an increase in Pincrease in PCO2CO2 or a decrease in P or a decrease in PO2O2 or pH or pH These levels remain surprisingly constant during exerciseThese levels remain surprisingly constant during exercise


As exercise begins:As exercise begins: Ventilation increases abruptly, rises slowly, and Ventilation increases abruptly, rises slowly, and

reaches a steady statereaches a steady state When exercise stops:When exercise stops:

Ventilation declines suddenly, then gradually Ventilation declines suddenly, then gradually decreases to normaldecreases to normal


Neural factors bring about the above changes, Neural factors bring about the above changes, including:including: Psychic stimuliPsychic stimuli Cortical motor activationCortical motor activation Excitatory impulses from proprioceptors in Excitatory impulses from proprioceptors in

musclesmuscles

Respiratory Adjustments: High Respiratory Adjustments: High AltitudeAltitude

The body responds to quick movement to high The body responds to quick movement to high altitude (above 8000 ft) with symptoms of altitude (above 8000 ft) with symptoms of acute mountain sickness – headache, shortness acute mountain sickness – headache, shortness of breath, nausea, and dizzinessof breath, nausea, and dizziness

Respiratory Adjustments: High Respiratory Adjustments: High AltitudeAltitude

Acclimatization – respiratory and Acclimatization – respiratory and hematopoietic adjustments to altitude include:hematopoietic adjustments to altitude include: Increased ventilation – 2-3 L/min higher than at Increased ventilation – 2-3 L/min higher than at

sea levelsea level Chemoreceptors become more responsive to PChemoreceptors become more responsive to PCO2CO2

Substantial decline in PSubstantial decline in PO2O2 stimulates peripheral stimulates peripheral

chemoreceptorschemoreceptors

Chronic Obstructive Pulmonary Chronic Obstructive Pulmonary Disease (COPD)Disease (COPD)

Exemplified by chronic bronchitis and Exemplified by chronic bronchitis and obstructive emphysemaobstructive emphysema

Patients have a history of:Patients have a history of: SmokingSmoking Dyspnea, where labored breathing occurs and gets Dyspnea, where labored breathing occurs and gets

progressively worseprogressively worse Coughing and frequent pulmonary infectionsCoughing and frequent pulmonary infections

COPD victims develop respiratory failure COPD victims develop respiratory failure accompanied by hypoxemia, carbon dioxide accompanied by hypoxemia, carbon dioxide retention, and respiratory acidosisretention, and respiratory acidosis

Pathogenesis of COPDPathogenesis of COPD

Figure 22.28

AsthmaAsthma

Characterized by dyspnea, wheezing, and Characterized by dyspnea, wheezing, and chest tightnesschest tightness

Active inflammation of the airways precedes Active inflammation of the airways precedes bronchospasmsbronchospasms

Airway inflammation is an immune response Airway inflammation is an immune response caused by release of IL-4 and IL-5, which caused by release of IL-4 and IL-5, which stimulate IgE and recruit inflammatory cellsstimulate IgE and recruit inflammatory cells

Airways thickened with inflammatory Airways thickened with inflammatory exudates magnify the effect of bronchospasms exudates magnify the effect of bronchospasms

TuberculosisTuberculosis

Infectious disease caused by the bacterium Infectious disease caused by the bacterium Mycobacterium tuberculosisMycobacterium tuberculosis

Symptoms include fever, night sweats, weight Symptoms include fever, night sweats, weight loss, a racking cough, and splitting headacheloss, a racking cough, and splitting headache

Treatment entails a 12-month course of Treatment entails a 12-month course of antibioticsantibiotics

Accounts for 1/3 of all cancer deaths in the Accounts for 1/3 of all cancer deaths in the U.S.U.S.

90% of all patients with lung cancer were 90% of all patients with lung cancer were smokerssmokers

The three most common types are:The three most common types are: Squamous cell carcinoma (20-40% of cases) arises Squamous cell carcinoma (20-40% of cases) arises

in bronchial epitheliumin bronchial epithelium Adenocarcinoma (25-35% of cases) originates in Adenocarcinoma (25-35% of cases) originates in

peripheral lung areaperipheral lung area Small cell carcinoma (20-25% of cases) contains Small cell carcinoma (20-25% of cases) contains

lymphocyte-like cells that originate in the primary lymphocyte-like cells that originate in the primary bronchi and subsequently metastasizebronchi and subsequently metastasize

Lung CancerLung Cancer

Olfactory placodes invaginate into olfactory Olfactory placodes invaginate into olfactory pits by the 4pits by the 4thth week week

Laryngotracheal buds are present by the 5Laryngotracheal buds are present by the 5 thth weekweek

Mucosae of the bronchi and lung alveoli are Mucosae of the bronchi and lung alveoli are present by the 8present by the 8thth week week

Developmental AspectsDevelopmental Aspects


By the 28By the 28thth week, a baby born prematurely can week, a baby born prematurely can breathe on its ownbreathe on its own

During fetal life, the lungs are filled with fluid During fetal life, the lungs are filled with fluid and blood bypasses the lungsand blood bypasses the lungs

Gas exchange takes place via the placentaGas exchange takes place via the placenta

At birth, respiratory centers are activated, At birth, respiratory centers are activated, alveoli inflate, and lungs begin to functionalveoli inflate, and lungs begin to function

Respiratory rate is highest in newborns and Respiratory rate is highest in newborns and slows until adulthoodslows until adulthood

Lungs continue to mature and more alveoli are Lungs continue to mature and more alveoli are formed until young adulthoodformed until young adulthood

Respiratory efficiency decreases in old ageRespiratory efficiency decreases in old age


respiratory volumes

Documents

tlc total lung capacity

gas flow

mlresidual volume rv

rv residual volume

gas exchanges

rv result

mixture of gases

lungs oxygen