Pulmonary Flashcards
Why respiratory system - respiratory function
Gas transport for metabolism
Why respiratory system - non respiratory function
Filtering and metabolism
Stages of gas transport
Ventilation
Lung diffusion
Circulation
Tissue diffusion
Internal respiration
Stages of gas transport - ventilation
Movement of bulk airflow from atmosphere into lungs and vice evrsa
Stages of gas transport - lung diffusion
Gas exchange between respiratory zone and plasma/RBC across alveolar membrane
Stages of gas transport - Circulation
Blood flow carries gas to and from tissues
Stages of gas transport - tissue diffusion
Movement of oxygen from blood supply to tissue
CO2 from tissue to blood supply
Stages of gas transport - Internal respiration
Cellular metabolism using O2 and producing CO2 –> generates energy
Upper respiratory tract - function
Gas humidification, filtration, warming
Nasal passages
Air turbulence
Conducting airways function
Gas distribution to respiratory zone
No diffusion of gas
Airway patency based on structure: Trachea, bronchi, bronchioles
Trachea - cartialage arches (tracheal rings)
Bronchi - cartilage plates
Bronchioles - no cartilage, depend on lung recoil
Airway clearance mechanisms
Bronchi - Cilia and bronchial glands clear contaminants
Distal conducting airways - cilia and goblet cells
Defensins - innate lung immunity
Ventilatory pump contents
Rib cage and spine
Diaphragm
Intercostal muscles
Abdominal muscles
Accessory muscles
Visceral and parietal pleura and pleural fluid
Ventilatory pump - rib cage and spine
Walls of pump
Increase volume of chest cage during inspiration
Posture
Ventilatory pump - Diaphragm
Generates significant negative pressure for inspiration
Ventilatory pump - Intercostal muscles
External intercostals - chest wall expansion
Internal intercostals - Exhalation
Ventilatory pump - Abdominal muscles
Muscles of expiration
Utilized in lung disease or vigorous exercise
Ventilatory pump - Accessory muscles
Used in lung disease or exercise
Tripod sitting - Lean forward on table/desk to stabalize shoulder girdle and neck/shoulder to act on chest wall
Ventilatory pump - Parietal pleurae and pleural fluid
Visceral pleura - lies on lung, no pain fibers
Parietal pleura - covers inside of rib cage, pain fibers
Pleural space normally closed but can open/fluid filled in disease states
Pleural fluid acts as lubricant between two pleura
Quiet breathing
Diaphragm contracts –> thorax volumed expands –> pleural space pressure decreases below atmospheric –> lungs expand and alveoli increase volume (negative pressure) –> air flows down airways into alveoli
Inspiratory muscles relax –> lung recoils –> alveoli decrease volume (pressure increases) –> air flows out of lung
Exercise/lung disease breathing
Expiration may become active
Abdominal muscles and internal intercostals used –> further alveoli compression and expiration
Repiratory zone: Contents and characteristics
Respiratory bronchioles, alveloar ducts, alveoli - gas exchange
Large surface area
Large volume of gas maintain diffusion pressure gradient
Very thin membrane
Thin alveolar blood gas barrier contents
Respiratory epithelium
INterstitial space
Capillary endothelium
Plasma
Erythrocyte
Gas diffusion and heart pumping
Oscillating nature of heart provides energy to gas in small airways and increases diffusion
Non respiratory function of lung - Maintenece and defense
Keeps itself clean via cleansing mechanisms and innate/adaptive immunity
Constant turnover and remodeling
Surfactant to maintain alveolar compliance
Non respiratory function of lung - filtering
Small capillaries can filter out physical material (clots, foreign bodies etc)
Non respiratory function of lungs - chemical processing
Hormone production: ACTH, prsotaglandings, vasoactive peptides, GF, serotonin
ACE
Arachiadonic acid release after pulomnary endothelium damage
Physiological dead space
Sum of:
Anatomic dead space (conducting airways)
Gas in NON PERFUSED alveoli (no gas exchange occurs)
Alveolar ventilation and PaCO2
Inversely proportional
Double alveolar ventilation = halved arterial CO2
Halved alveolar ventilation = double arterial CO2
Driving force of oxygen between alveoli and capillary
60mmHg towards capillary
Driving force of CO2 between alveoli and capillary
5mmHg towards alveoli
Perfusion limitation
Diffusion is controlled by perfusion
No blood flow = equilibration of gasses and no more diffusion
Conditions that cause O2 transfer to become diffusion limited
Thickening of alveolar capillary membrane
High altitude/Low FIO2
Increased pulmonary blood flow
Diffusion limited O2 transfer - thickening of capillary membrane
Increases time for diffusion across membrane
Decreases rate of diffusion
Sever pulmonary diseases - pulmonary fibrosis
Diffusion limited O2 transfer - Low FIO2/high altitude
Decreased alveolar O2 pressure and decreased gradient across alveolar membrane
Decreases rate of diffusion
Diffusion limited O2 transfer - Increased pulmonary blood flow
Increased cardiac output = blood moves rapidly through lung and complete saturation is not achieved
Diffusion is not fast enough to keep up with perfusion
Amount of dissolved O2 in 1L of blood
3mL at PO2 of 100mmHg
Majority of oxygen in blood is located where…?
Bound to Hb
~96%
1g of Hb contains how much O2 when 100% saturated
1.34mL
Hb saturation in lung vs tissues
Hb in lung is almost 100% saturated
Hb in tissue is <60% saturated (O2 leaves Hb to go to tissue)
Left shift of HbO2 curve - causes and meaning
Hb has higher affinity for O2 at lower partial pressure
Decreased PC02
Increased pH (Decreased H)
Decreased temp
Decreased 2,3 BPG
HbO2 curve shifted to right - causes and meaning
Lower affinity to Hb given partial pressure of O2
Increase PCO2
Decrease pH
Increase temp
Increased 2,3 BPG
CO poisoning
Super high affinity to Hb, making it unavailable to carry Oxygen
When Hb binds to CO, P50 decreases and increases affinity for oxygen
Less oxygen carried and less oxygen released
Fetal hemoglobin
Higher affinity for O2
HbO2 shifted to left, decreased P50
Need to be able to take oxygen from placenta to fetus
Adequate delivery of oxygen to tissues requires:
Oxygen content in blood: Adequate PaO2 and hemoglobin
Cardiac output: Adequate delivery of oxygen to arteries
Vascular supply: Adequate delivery of oxygen to tissues
Hypoxemic hypoxia
Low PaO2 –> low oxygen saturation of Hb
Anemic hypoxia
PaO2 is normal
Oxygen carrying capacity is low –> low O2 content
Anemia
Circulatory hypoxia
Oxygen content normal
Blood flow to tissues reduced
Shock
Histotoxic hypoxia
Oxygen content and blood flow is normal
Tissue cannot use oxygen at cellular level
Cyanide poisoning
Carriers of CO2
Physical solution
Bicarbonate
Carbamino compounds (CO2 bound to NH4 on Hb)
Solubility of CO2
20x more solube than O2
.06mL CO2 dossolved/100mL blood per mmHg partial pressure
Major form of CO2 carried in blood
HCO3 in RBC
Deoxygenated Hb and Carbonic anhydrase equation
Deoxygenated hemoglobin accepts H+ –> reduces H+ –> drive reaction to HCO3
Tissues = deoxygenated Hb = H acceptance = CO2 pickup as HCO3
Oxygenated Hb and Carbonic anhydrase equation
Oxygenated Hb releases H+ and drives reaction towards CO2
Oxygenated Hb in lungs = released H+ = CO2 production
Difference between CO2 curve and O2 curve
Higher total content of CO2 in blood per mmHg partial presure
Steeper slope (more change in CO2 content per change in PCO2)
No effective plateau or max content
Haldane effect
As PO2 increases, CO2 dissociation curve shifts downward
Less CO2 carried in blood
Lungs: Blood takes up oxygen, CO2 released and expired
Tissues: Blood releases oxygen, increases capacity for CO2, takes up CO2 to transport ot lungs
Law of mass action and CO2: Lungs and tissue
Lung: PCO2 drop causes carbamino compounds and Bicarb to generate CO2 (In RBC)
Tissues: Increase in PCO2 forms HCO3 and carbamino compunds for transfer to lungs
RBC Carbonic anhydrase action in lungs
HCO3 decreases rapidly b/c forming H20 + CO2
Decrease in RBC HCO3 = HCO3 diffuses into cell = Cl exit from cell
RBC carbonic anhydrase in tissues
HCO3 rapidly increases inside RBC –> diffuses out of cell –> Cl entry
Ventilation/Perfusion (V/Q) ratio and CO2?O2 levels
Increased V/Q = increased ventilation = increased O2 and decreased CO2 (removal of CO2 and delivery of fresh O2)
Decreased V/Q = increased perfusion = decreased O2 and increased CO2 (Increased CO2 delivery with less O2, increased gas exchange)
V/Q at bottom/base of lung
Decreased V/Q
Perfusion higher than ventilation
Bottom of lung will have higher PCO2 and lower PAO2
V/Q at top/apex of lung
Increased
More ventilation relative to perfusion
Increased PAO2 and decreased PCO2
V/Q = infinity = ?
Highest amount of Oxygen and no CO2
Dead space, no perfusion, no gas exchange
V/Q = 0 = ?
No ventilation and complete perfusion
High CO2 and no O2
Shunt, blood does not get oxygenated
Compensatory response of hypoventilated part of lung
Other lung units can hyperventilate and lower CO2
Average all units CO2 to get CO2 of lungs
Compensatory O2 response of hypoventilated lung
Mixed blood O2 is NOT average of different units because hyperventilation of other units does not increase O2, saturation has already occurred
Central hypoventilation gas result and treatment
Central hypoventilation results in an increased PaCO2 which results in a decreased PAO2
Giving oxygen with an increased FIO2 can overcome this
Steps to find cause of hypoxemia
Calculate PAO2 and decide if hypoventilation is cause
If not hypoventilation –> measure diffusion capacity to see if there is diffusion limitation
If not diffusion limitation –> V/Q mismatch or shunt. Give oxygen: V/Q mismatch will resolve, R->L shunt will not
Tidal volume
Amount of air exchanged with each breath
~7.5L/min
Residual volume
Volume of gas left in lung after a complete expiration
Unable to completely empty lung because we cannot completely collapse chest
25% TLC
Inspiratory reserve volume
Volume of air that can be inspired from end of tidal inspiration to total lung capacity
Use if need to take deeper breath
Expiratory reserve volume
Volume of air we can exhale from end of tidal expiration
Forced exhale, dry cough
Total lung capacity
Total lung capacity
Volume at which inspiratory muscles are no longer strong enough to overcome expiratory recoil of lung and chest wall
Vital capacity
Volume of air that can be exhaled from TLC to RV
All volumes except RV
Measure by asking pt to inspire completely and expire into spirometer
Functional Residual capacity
Volume of gas in lungs at end of tidal expiration
Sum of ERV and RV
FRC prevent hypoxemia during exhalation
Inspiratory capacity
Complement of FRC
TLC = FRC + IC
Sum of TV + IRV
Non compliant lung
Require greater pressure change for each breath
Restrictive
Surfactant
Complex protein/phospholipid taht interrupts surface tension laws of lung
Low surface tension when area is small
High surface tension when surface area is large
Accounts for hysteresis in lung inflated with air
Surfactant and low/high volumes
Low volume inflation –> surfactant is in water layer and not at surface, does not reduce surface tenstion
High volume inflation –> surfactant spreads on surface and reduces surface tension
Lung more compliant at higher volume (inflated)
Pleural pressure gradient in lung
Occurs due to weight of lung
Top of lung: No weight added, pleural pressure at its most negative
Bottom of lung: Lung weight added and causes less negative pleural pressure
Pleural pressure gradient and alveoli
Alveoli at apex will be higher percent of max volume compared ot base of lung
Lung base: pleural pressure, alveolar volume
Pleural pressure is less negative
Alveoli at a lower volume
Alveoli are more compliant
Lung apex: Pleural pressure and alveolar volume
Pleural pressure is more negative
Alveoli at higher volume
Apex alveoli are less compliant
Pulmonary HTN definition
Resting mean pulmonary arterial pressure >25mmHg
Normal is between 8 and 20mm Hg
Pulmonary arterial HTN (PAH) definition
Mean pulmonary arterial pressure >25mm Hg
PUlmonary venous (pulmonary capillary wedge) pressure <15
Group 1 PAH
Pulmonary arterial HTN
Idiopathic PAH
Inherited
Connective tissue disease, HIV, portal HTN, congenital heart disease
Group 2 Pulmonary HTN
Pulmonary HTN due to left heart disease
Systolic dysfunction
Diastolic dysfunction
Valvular disease
Group 3 Pulmonary HTN
Pulmonary HTN due to lung disease and/or hypoxia
COPD
Interstitial lung disease
Sleep disordered breathing
Group 4 pulmonary HTN
Chronic thromboembolic pulmonary HTN
CTEPH
Components of pulmonary pressures
Pulmonary venous pressure/LA pressure
Pulmonary vascular resistance
Right sided Cardiac Output
Causes of increased pulmonary venous pressure
Left ventricular or diastolic dysfunction
MItral valve disease
Causes of increased pulmonary vascular resistance
Conditions that decreases area of pulmonary vascular beds (pulmonary emboli, CT disease, interstitial lung disease, COPD)
Conditions that induce hypoxic vasoconstriction
Causes of increased right sided cardiac output
L–>R ASD
L–>R VSD
Other systemic –> pulmonary shunts
Increases Right Ventricular volume
Pulmonary HTN sequence of events
Initiatl injury –> mild P HTN –> elevated pressure damages pulmonary vasculature –> narrowed pulmonary vascular bed –> RV hypertrophy to overcome increased resistance –> vascular injury accelerates with increased pulmonary arterial pressure –> increased RV afterload –> RV failure
Genetic predisposition to PAH
Genetic mutations in bone morphogenetic protein receptor type 2
BMPR2
Inuces apoptosis in certain cell types
Permits excess endothelial cell grownt and proliferation in response to injury
Sigaling pathways disturbed in PAH
Decreased prostacyclin and decreased Nitric Oxide pathways –> Inhibit vasodilation and increases proliferation
Increased endothelin pathway –> Vasoconstriction and increased proliferation
Pulmonary HTN clinical presentation and physical exam
Dyspnea on exertion and fatigue
RV failure = ankle swelling
Exertional chest pain, syncope can develop
Increased intensity of pulmonic component of S2
Community acquired pneumonias
95% due to viral, mycoplasma, pneumococcal, or Leigonella infections
Nonsocomial pneumonias
1% of hospital patients
ICU patients at highest risk
G(-) bacilli
Staph Aureus
Aspiration pneumonias
Caused by aspiration of infective material and/or gastric contents
Anaerobic bacteria
Chemical pneumonitis, necrotizing pneumonia, lung abscess, empyema
Pneumonia in immunocompromised hosts
Suppressed immune system due to disease or drugs
Opportunistic organisms
Pathogenesis of pneumonia
Loss of defense mechanisms
- Inhibition of normal cough reflex from NM disease, drug overdose, intubation, coma –> allows gastric contents/oropharyngeal flora to aspirate into lungs
- Injury of mucociliary apparatus prevents clearance of small inhale particles/microorganisms: Viral destruction, smoking, genetic disease
- Interference of phagocytic or bactericidal action of alveolar macrophages - alcohol, tobacco smoke, snoacia
- Bronchial obstruction - neoplasm, mucus plugging –> prevents clearance
- Decreased immunity
Alternative factors/mechanisms of pneumonia pathogenesis
Direct introduction of organisms into sterile lung by intubation/contaminated respiratory equipment
Hematogenous spread of infections
Bacteria common to hospital environments are often drug resistant
Bacterial pneumonia classification
Based on etiological agent and anatomic distribution pattern
Clinical presentation, PE, CXR of bacterial pneumonia
Malaise, fever, chills, pleuritic pain, productive cough (blood tinged)
Decreased breath sounds in affected lobes, expiratory rales
May have Leukocytosis with left shift
CXR - focal opacaties and occasionally pleural effusions
Most common organism causing pneumonia in ambulatory patients
Strep Pneumoniae
Most common cause of pneumonia in hospitalized patients
Gram(-) bacilli (Pseudomonas, Klebsiella, Proteus, E Coli)
Reach lungs via upper airways or through blood
Upper respiratory viral infections follwe dby…
Staphylococcal and Haemophilus
Legionella pneumophila
Associated with aerosols from cooling systems
Multiple small abscesses
Only grows on special media, may be missed on culture
Pathology: Bronchopneumonia
Lobular pneumonia
Gross: Patchy consolidation. Infiltrates associated with airways and represent extension of preexisting bronchitis/bronchiolitis
Microscopic: Alveolar spaces filled with suppurateive exudate composed of PMN, RBC, fibrin, edema, macrophages
Alveolar septa hyperemic and congested, not inflamed
Pathology: Lobar pneumonia
Gross/microscopic:
Consolidation by fibrinopurulent material is widespread and involves entire lobes/lobules
Rarely seen
Complications of bacterial pneumonia
- Abscess
- Empyema
- Organization
- Bacteremic dissemination
Complication of bacterial pneumonia: Abscess
Local suppurative process
Destruction of lung tissue and accumulation of neutrophils
Associated with aspiration, septic emboli, and bronchial obstruction
Strep Pneumoniae
Organism that most commonly causes abscess in pneumonia
Strep Pneumoniae, Pseudomonas aeruginosa, Staph aureus, anaerobes
Contain enzymes that liquify lung tissue
Complication of bacterial pneumonia: Empyema
Purulent inflammation of pleural space caused by spread of infection into pleural cavity
Complication of bacterial pneumonia: Organization
If fibrinous alveolar exudate is not broken down and reabsorbed –> organization
Formation of intraalveolar plugs of granulation tissue composed of fibroblasts, fibrin, and inflammatory cells
Can mature into fibrous tissue –> Scarring
Complication of bacterial pneumonia: Bacteremic dissemination
Sepsis
Spread to other organs
Viral pneumonias - more common in children or adults
Children
Clinical presentation of atypical pneumonias
Fever, headache, muscle aches
Dry, hacking, non productive cough
Most common complication is secondary bacterial pneumonia
Atypical pneumonia gross appearance
Discrete infiltrates, difficult to appreciate
Rare pleural effusions
Microscopic appearance of atypical pneumonias
Mononuclear interstitial inflammatory infiltrate within walls of alveoli
Alveolar septa widened and edematous, alveolar space may contain protein rich fluid
Type II pneumocytes are hyperplastic
Alveolar wals lined by hyaline membranes
Herpes, varicela, adenovirus atypical pneumonia microscopic appearance
Necrosis of bronchial and alveolar epithelium
CMV, herpes, and measles atypical pneumonia microscopic appearance
Viral inclusions within infected cells
Chronic Granulomatous infection categories
Fungal infections
TB
Pneumonial fungal infections
Coccidiomycosis
Histoplasmosis
Blastomycosis
Coccidiomycosis
Fungal infection caused by Coccidioides
Southwest US
Lung lesions, pleuritic pain, cough
Seen in tissue as large double walled spherules - filled with endospores
Granulomatous inflammation with giant cells and macrophages
Histoplasmosis
Fungal infection caused by Histoplasma
Central US
Usually asymptomatic until immunocompromised
Blastomycosis
Funcgal infection caused by Blastomyces
Eastern US
Granulomatous response
Tuberculosis
Mycobacterial infection caused by Mycobacterium tuberculosis
TB: Pattern of infection
Primary infection: Granulomas in lung and lymph nodes that frequently calcify
Secondary infection: Re activation. Usually in apices
Fibrocaseous disease: Upper lobe, cavities common
Miliary Spread: Hematogenous dissemination, innumerable micronodules in lungs, liver, spleen etc
Bronchopneumonia: Seen in overwhelming disease
TB clinical presentation
Primary infection - asymptomatic or flu like disease
Secondary infection - more severe symptoms
Erosion of lesions into blood vessels –> hemoptysis
TB pathology
Caseating granuloas
Epithelioid histocytes surrounded by lymphocytes, fibroblasts, giant cells
Central caseous necrosis
Progressive pulmonary TB
Active lesions may continue to progress –> cavitary fibrocaseous TB, miliary dissemination, TB bronchopneumonia
Opportunistic infections
Pneumocystis jiroveci
Aspergillus
Zygomycetes
Cryptococcus
Candida/torulopis
CMV, HSV
Actinomyces and Nocrdia
Pneumocystis jirovechi
Alveolar infiltrate of foamy material and mononuclear cells
Seen in HIV pts with CD4 <200
Aspergillus
Ubiquitous fungal organism found in soil and inhaled into lungs
Colonize old cavities from previous disease and grow as fungus ball
Can invade parenchyma and produce necrotizing pneumonia
Invades arteries and veins –> hemorrhagic infarcts
Septae hyphae branching @ 45 degree angle
Zygomycetes
Invade arteries and veins
Hyphae are pauciseptate and branch at 90 degree angle
Cryptococcus
Inhaled encapsulated yeast which causes mild pulmonary symptoms
Often spreads to CNS
Thick gelatinous capsule which appears as halo after tissue fixation
Candida and Torulopis
Produce bronchitis,bronchopneumonia, hemorrhagic pneumonia, acute abscesses
In immunicompromised patients
CMV and HSV
Hemorrhageic interstitial pneumonias
Actinomyces and nocardia
Filamentous branching bacteria which produce acute pneumonia with rapid progression to abscesses
FEV1/FVC less than LLN = ?
Obstructive defecit present
FVC less than LLN = ?
Restrictive deficit
Pulmonary circulation, pressure and resistance?
Low pressure, low resistance system
Gravity and pulmonary circulation
Apex: Low vascular pressure, collapsed vessels
Base: High vascular pressure, distended vessels
Interstitial pressure most negative at apex –> alveolar pressure is greatest at apex –> compresses vessels
Zone 1 of lung
Apex of lung
Palveoli > Parterial > Pvenous
No flow conditions, vessels collapsed shit
Alveolar dead space
Zone 2 of lung
Parterial > Palveolar > Pvenous
Arterial pressure is greater than alveolar so there is flow
Zone 3 of lung
Parterial > Pvenous > Palveolar
Continuous flow
Blood pressures at either end of system determine flow
Vessels completely distended
Extrapulmonary vessel distention at apex and base of lung
Apex: Fully distended b/c not exposed to alveolar pressure AND pleural pressure most negative
Base: Collapsed b/c pleural pressure least negative
Passive effects on pulmonary vascular resistance
- Vascular pressures
- lung volume
Vascular pressure effects on pulmonary vascular resistance
Increased vascular pressure = distended vessels = decreased resistance
Pulmonary vascular resistance during exercise
Increased CO = increased pulmonary artery pressure = Decreased pulmonary vascular resistance
- Vessels distended = decreased resistance
- Opening of closed (zone 1) vessels increases total cross sectional area = decreased resistance
Pulmonary vascular resistance during shock
Decreased cardiac output = decreased pulmonary vascular pressure = collapsed vessels = increased resistance
De-recruitment of upper zones due to drop in pressure and collapse of vessels
Lung volume and pulmonary vascular resistance
High lung volume: Intra-alveolar vessels = collapsed, extra-alveolar = distended
Low lung volume: Intra-alveolar vessels = distended, extra-alveolar vessels collapsed
Intra-alveolar vessels have lowers resistance at what volume
Residual volume (lowest volume)
Extra-alveolar vessels have lowest resistance at what volume
TLC, highest volume
Active regulation of pulmonary vascular resistance
- Neural
- Local
- Humoral
Local control of pulmonary vascular resistance
- Alveolar hypoxia causes vasoconstriction. Shunt blood to ventilated areas of blood
- Acidosis, hypercapnia, and prior smooth muscle hypertrophy accentuate the hypoxic vasoconstrictive response
Pulmonary vascular resistance is highest when alveolar hypoxia occurs in the face of acidemia
Pulmonary edema types
Hydrostatic edema
Non hydrostatic edema
Hydrostatic edema
Pulmonary edema due to increased pulmonary capillary pressure
Fluid backup:
Mitral valve stenosis
LV failure
Fluid overload due to renal failure
Non hydrostatic pulmonary edema
Chemical/thermal injury: Chemical inhalation, drowning, smoke inhalation
Humoral and immune injury: Endotoxin, prolonged shock, head injury
Receptors that monitor effects of breathing
- Chemoreceptors - respond to O2, CO2, and pH
- Mechanoreceptors - Respond to mechanical information from respiratory pump
Dorsal Respiratory Group
Inspiration
Controls basic rhythm of breathing
Quiescence –> crescendo of neuronal activity (inspriation) –> quiescence (expiration occurs here)
Input from CN IX/X
Output via phrenic nerve to diaphragm and other outputs to chest wall/upper airway muscles
Ventral Respiratory group
Expiratory area is inactive during normal respiration (expiration is passive during quiet breathing)
Exercise/lung disease - Activity in these neurons for active expiration
The Apneustic Center
Lower pons
Brainstem damage above this area results in apneustic breathing –> isolated from pneumotaxic center
Sends signals to DRG that prolong duration of excitatory ramping of diaphragm activity
Apneustic breathing
Prolonged inspiratory gasps with rapid expiration
Pneumotaxic Center
Upper pons
Responsible for ending inspiration, terminates inspiration activity
Central chemoreceptor
Primary chemical control of regular quiet breathing
Ventro-lateral medulla, close contact with CSF
Increased CO2 = increased ventilation
Chemoreceptor senses H+ difference (carbonic anhydrase equation)
Peripheral chemoreceptor locations and respond to ?
Carotid and aortic bodies
Respond to:
- Decreased PaO2
- Increased PaCO2
- Increased H+ (decreased pH)
Ventilatory response to hypoxia
Increase in peripheral chemoreceptor activity with PaO2 less than 500
NON LINEAR RESPONSE
Minimal increase until PaO2 less than 100
Dramatic increase when PaO2 less than 60
Pulmonary stretch receptors
Slowly adapting receptors that respond to stretching of airways
Transmit information via vagus
Responsible for vagal mediated inhibition of inspiration and promotion of expiration
Pulmonary irritant receptors
Extra-pulmonary airway epithelium
Rapidly adapting
Under conditions of continued irritation –> adapt and reduce activity
Respond to:
- Chemical irritation: Gas, antigens, inflammatory mediators
- Physical irritation: Airflow, particulates, bronchial smooth muscle tone
- Lung volume: Initiate sighs to maintain lung volume
Juxtacapillary Receptors
Located in alveolar walls near capillaries
Connect to central controllers via unmyelinated fibers, rapidly adapting
Stimulated by interstitial edema, inflammation
Also stimulated by increased left atrial and pulmonary venous pressure
Cause laryngeal closure and apnea, followed by shallow rapid breathing
Chest wall proprioceptors
- joint receptors
- Tendon receptors
- Muscle spindle receptors
Joint receptors
Ruffini, pacinian, golgi organs
Activity proportional to rate of rib movement
Tendon organs
PResent in intercostal and diaphragm muscle tendons
Monitor force fo contraction and inhibit inspiration
Muscle spindle receptors
Abundant in intercostals, rare in diaphragm
Stabalize rib cage and compensate for changes in body positions
Passive stretch –> increase afferent activity –> stimulate alpha motor neuron –> contract intercostal muscle
Respiratory control failure and disease states: Increased work of breathing
Obstructive diseases: COPD, obesity, sleep apnea
Causes response to CO2 to be blunted –> rise in CO2
Due to down regulation of response system due to maximum amount of work level reached
Respiratory control failure and disease states: Decreased efficiency of gas exchange
More work needed to achieve same result
Can lead ot diminished ventilatory drive
Respiratory control failure and disease states: Impaired ventilatory pump performance
Hyperinflation due to obstruction stretches inspiratory muscles and they become inefficient
Chest wall restriction (muscular dystrophy) also decreased ventilatory response
Respiratory control failure and disease states: Chronic CO2 retention
Leads to bicarb reabsorption in kidney causing metabolic alkalosis
Bicarb enters CSF over time and buffers change in H normally associated with CO2 increase
Abolishes central chemoreceptor drive
CFTR gene and mutation
DF508
Deletion of Phenylalanine at 508 position
CFTR protein
ATP binding anion channel
Pathophysiology of CF respiratory disease
Mucociliary clearance dysrupted due to inadequate hydration of airway surface liquid
Increased activity of ENaC –> Cl entry via electrochemical gradient –> water entry into cell –> decreased airway surface liquid
No mucociliary clearance = higher risk of infection, inflammation, obstruction –> chronic lung disease
Most common infective organism in CF
Pseudomonas
Staph aureus
CF is what type of lung disease?
Obstructive
Pathophysiology of CF GI disease: exocrine
Exocrine pancreatic insufficiency:
Autodigestion of pancreas w/ fibrosis, cysts, fatty replacement –> no enzyme production
–> Maldigestion of fats/proteins
Can cause bowel obstruction
Pathophysiology of CF GI disease: Other
CF Diabetes mellitus
Hepatobiliary disease: Inadequate bile flow, altered bile salts, inadequate bicarb concentration in bile –> Cholelithiasis, cholecystitis, biliary cirrhosis + portal HTN
GERD: Lung hyperinflation + reduced GI motility