Respiratory Physiology Lecture Powerpoint Flashcards
Respiratory system functions (5)
- Gas exchange
- Regulation of pH
- voice production
- olfaction (smell and taste)
- protective against infection
Conducting zone vs respiratory zone of the respiratory system
Conducting is down to terminal bronchioles, respiratory zone begins at respiratory bronchioles, and extends to alveolar ducts and alveoli
2 major functions of the conducting zone of the respiratory system
- warms and moistens air
- removal of microbes and toxins thru macrophages and mucociliary escalator
Respiratory membrane and its 4 layers
- The thickness that the gas has to move thru to be exchanged between the vasculature and the alveoli
- cell membrane of RBC, interstitial space, alveolar membrane, and fluid/content within the alveoli
Pleural membranes and their 2 functions
- Visceral and parietal adherant double layered serosa filled in potential space cavity with lubricating fluid
- functions to reduce friction when breathing, creates a slightly negative pressure gradient to promote inflation of the lungs
Stages of respiration (5)
1) ventilation - movement of air into and out of lungs
2) external respiration - gas exchange between air in lungs and blood
3) respiratory gas transport - movement of o2 and co2 throughout circulation
4) internal respiration - gas exchange between blood and tissues in the body
5) cellular respiration - usage of o2 and production of co2 from cells
Boyle’s law
States pressure of any given quantity of gas is inversely proportional to its volume assuming constant temperature
Dalton’s law
Total pressure of gas mixture is equal to the sum of its partial pressures of individual gases
Henry’s law
At the air water interface, the amount of gas dissolves in water is determined by its solubility in water (coefficient, property of the chemical) and its partial pressure in the air assuming constant temp
Atmospheric pressure value at sea level
1atm or 760mmHg
Air enters lungs when…
Air exits lungs when….
…alveolar pressure is less than atmospheric
….alveolar pressure is greater than atmospheric
Poiseuille’s law and importance
- States R=8n(viscosity)*l/pi r^4
- Small changes in the diameter of the bronchioles greatly impacts resistance of airflow
Pulmonary compliance, what dz states decrease and increase it?
- Refers to distensibility of lungs, change in lung volume relative to given change in transpulmonary pressure
- decreased with disease states such as pulmonary fibrosis and increased in diseases such as emphysema or copd (harder to get air out of lungs)
Triggers of bronchoconstriction (4)
- airborne irritants
- cold air
- paraysmpathetic stimulation
- histamine
Triggers of bronchodilation (2)
Sympathetic nerves, epi (or a b-2 agonist such as albuterol)
Most common causes of increased airway resistance (3)
- swelling (laryngedema)
- obstruction (mucus plugging)
- spasm of smooth muscle (asthma attack)
Muscles involved in inspiration and how do they move? (3)
- diaphragm (flattens and increases superior inferior aspect of chest cavity)
- external intercostals (elevate ribs moving the thoracic cavity up and out)
- pec minors, sternocleidomastoid, erector spinae muscles (accessory use for deep inspiration only)
Intrapleural pressure at rest vs during inspiration
Intrapleural pressure becomes even more neg (decreases***) going from -756mmHg at rest (creating the adherence of the pleura to each other) to -754mmHg on inspiration
Intrapulmonary (intraalveolar) pressure at rest vs. during inspiration
Pressure drops from resting value of 760mmHg to 757mmHg (subatmospheric)
Transpulmonary pressure at rest vs during inspiration
Rises from resting value of 0mmHg to 3-4mmHg due to gradient difference between atmosphere and intrapulmonary pressure, causes airflow inward
Passive expiration and what does it do to intrapulmonary pressure, intrapleural pressure, and transpulmonary pressure?
Refers to how during quiet breathing expiration is achieved by the elasticity of the lungs and thoracic cage creating a intrapulmonary pressure of approx 763mmHg, intrapleural pressure increase back to 756mmHg, and transpulmonary pressure to reverse to begin flow outward
Forced expiration
Use of internal intercostal muscles that lie underneath external intercostal muscles and function to contract rib cage down and inward decreasing size of thoracic cavity, alongside abdominal muscles contracting increasing intra-abdominal pressure forcing diaphragm upward and increasing pressure on thoracic cavity to improve force of expiration
Pneumothorax
Loss of negative intrapleural pressure due to air in pleural cavity causing lungs to recoil and collapse (atelectasis)
Elasticity of lungs
Ability of lungs to return to normal shape after being distended, function of elastin protein content within lungs
Surface tension
Collapsing pressure resulting from attractive forces between molecules of liquid lining the alveoli (pulmonary surfactant decreases it naturally), the greater the surface tension the more difficult to expand the alveoli and the transpulmonary pressure needed to be generated
When lung compliance is abnormally high, lungs are prone to ____, often seen in the dz state ____, due to _____
collapse, emphysema, elastin protein loss
Respiratory distress syndrome of premature infants and its 3 treatment options
- Occurs often in premature born infants before production of surfactant has occurred at approx 8 months
- Can be treated with corticosteroids to mother, provision of synthetic surfactant, or placement on positive pressure airway
Surfactant allows for alveoli size to….
….be smaller without increased tendency to collapse
5 facts about pulmonary surfactant
- contains mix of phospholipids and protein
- type II alveolar cells secrete it
- lowers surface tension making lungs easier to expand
- deep breath increases secretion
- not produced until late gestation (>8months)
Anatomic dead space
150mL of respiratory tract in the conducting division of the airway that does not participate in gas exchange
Physiologic dead space
Sum of anatomic dead space and any pathological alveolar dead space where lungs are damaged from dz state
Alveolar ventilation
Volume of air actually reaching the alveoli, equals tidal volume (500mL)- anatomic dead space (150mL) = 350mL
Minute respiratory volume and its approx value at rest
total volume of air taken in 1 minute, =RR x tidal volume, at rest 6000mL but can increase significantly in exercise
Alveolar ventilation rate
Air that actually ventilates alveoli (Tidal volume - dead space volume) x the respiratory rate, directly relevant to body’s ability to exchange gases
Partial pressure of a gas =
vol%of that gas x total pressure
Composition of atmospheric air and their partial pressures at sea level (760mmHg) (4)
- 79% nitrogen (600mmHg at sea level)
- 21% oxygen (160mmHg at sea level)
- water presence depending on humidity
- trace amounts carbon dioxide and others (.23 mmHg at sea level)
Gases move ____ a partial pressure gradient
down
PO2 and PCO2 in alveoli
104 mmHg, 40mmHg
PO2 and PCO2 in oxygenated blood
104 mmHg, 40mmHg
PO2 and PCO2 in cells
40mmHg, 45mmHg
PO2 and PCO2 in deoxygenated blood
40mmHg, 45mmHg
O2 is ____ in water/plasma, while CO2 is ____ by ___x more
not very soluble, highly soluble, 24
Nitrogen narcosis
Excessive nitrogen buildup in the tissues often seen in patients at elevated pressures such as divers due to henry’s law where nitrogen increases in solubility because of its increased partial pressure, causing individuals to experience an intoxication due to the exposure
Decompression sickness
Nitrogen gas bubble build up in tissue causing deep pain and obstruction in the body from sudden drops in pressure such as ascending too quickly during a dive where because nitrogens partial pressure has decreased due to atmospheric pressure decrease, the solubility of it in the tissues decreases creating symptoms
Time required for gases to equilibrate in alveolar gas exchange vs time for RBC to pass the alveoli at rest and exercise
.25 sec, .75 at rest and .3 sec during exercise
At high altitudes, how is the partial pressures of gas affected?
-Atmospheric PO2 decreases, (not the number of O2 molecules, big difference) causing less oxygen to diffuse into the blood and perfuse the tissues (compensated over time with increased erythropoietin production), common causing high altitude sickness
How does decreased membrane surface area affect gas exchange?
Decreases rate of external respiration, requiring more respiration to achieve the equivalent perfusion
Opioid impact on respiratory rate
Slows respiratory center in medulla that can eventually cause hypoperfusion of tissue
V/Q matching
Required to adequately oxygenate blood, must match air moved into and out of lungs (V) with amount of blood flow thru the lungs (Q)
When standing, blood flow is increased in this zone and decreased in this one
Zone 3, zone 1
Standing patient alveolar, arterial, and venous pressure relationships in zones 1-3
Zone 1 - pAlveolar >parterial >pvenous
Zone 2 - parterial>pAlveolar>pvenous
Zone 3 - parterial>pvenous>pAlveolar
Normal V/Q ratio in healthy lungs
.8, perfusion exceeds ventilation under normal conditions
Causes of poor ventilation with continued perfusion (5)
Airway obstruction, mucus, edema, restrictive disease, atelectasis
Causes of poor perfusion with continued ventilation (1)
Pulmonary emboli secondary to DVT
Causes of impaired diffusion with continued perfusion and ventilation (2)
Pulmonary edema or pulmonary fibrosis that create a barrier to diffusion across the alveolar membrane
Positioning for lung dysfunction to max V/Q matching
Refers to trying to maximize the greatest pulmonary flow using gravity and positioning in coordination to ensure adequate blood flows past the good lung to maintain a good V/Q
Perfusion adjustment to match ventilation mech of action
-increased airflow
-causes elevated PO2 in blood vessels
-this causes vasodilation of pulmonary vessels
-increased blood flow occurs
-blood flow matches up to airflow
(works vise versa too)
Ventilation adjustment to match perfusion mech of action
-decreased blood flow
-reduced PCO2 in alveoli
-constriction of bronchioles decreases airflow
-airflow matches blood flow
(works vise versa as well)
At rest, only ___% of available o2 in oxygenated blood enters tissue, in exercise, ___%
25, 75
In 100mL of blood, __% of O2 is dissolved in plasma, and ___% is bound to hemoglobin
1.5, 98.5
How many O2 molecules can bind hemoglobin?
4, each one being EASIER than the last
Law of mass action
Refers to positive cooperativity where more oxygen binds to hemoglobin results in increased capacity to bind more o2 till all 4 slots fully saturated
As PO2 levels drop, what happens to hemoglobin saturation?
Hemoglobin saturation decreases
Venous blood is ___% saturated with O2 while arterial is normally ___%
75, 96-98
What factors cause the hemoglobin dissociation curve to shift to the right (improve O2 unloading)? (5)
- Decreased PO2 in metabolically active tissue
- temp increase in metabolically active tissue
- Bohr effect (active tissue has increased CO2 which raises H+ and lowers pH facilitating O2 release)
- Carbamino effect (Decreased affinity of HbCO2 for O2)
- DPG metabolite conc. increases facilitating O2 release by binding Hb
What factors cause the hemoglobin dissociation curve to shift to the left (improve O2 loading) (5)
- Increased PO2 conc. in metabolically inactive tissue
- temp decrease in metabolically inactive tissue
- Bohr effect (inactive tissue has decreased CO2 which lowers H+ and raises pH facilitating O2 loading)
- carbamino effect (decreased affinity of oxygen in HbCO2, which there is not a lot of HbCO2)
- DPG metabolite conc. decreases facilitating O2 binding to Hb
Carbon monoxide
Deadly gas that is undetectable by sense, has 200x greater affinity for hemoglobin than oxygen and thus prevents o2 from binding hemoglobin, can cause rapid loss in 50% of functional hemoglobin from just .5mmHg of partial pressure presence and thus leads to poisoning at low levels of exposure
Carbon dioxide 3 different transport mechanisms in circulation and what % travels in that form
- Bicarbonate ion HCO3- + H+ (70%)
- carbaminohemoglobin (binds hemoglobin in diff place than o2 making HbCO2 - 23%)
- dissolved gas in plasma (7%)
Carbonic anhydrase
Enzyme that converts carbon dioxide picked up at the tissue and water into carbonic acid in the a RBC in circulation which then dissociates into H+ and HCO3- ions which then leave the cell in exchange for a Cl- ion uptake (the reverse process undergoes upon the cell reaching the lungs
Haldane effect
Refers to how o2 bound with hemoglobin decreases affinity of hemoglobin for carbon dioxide, beneficial in venous blood flow upon the unloading of O2
Unconscious breathing control (quiet respiration) is facilitated by…
…neurons in medulla oblongata and pons
Voluntary breathing control is facilitated by…
What nerve groups (2) are these?
…Motor cortex inspiratory neurons which fire during inspiration to skeletal muscles of inspiration and expiratory neurons which fire during forced expiration to skeletal muscles of forced expiration
The phrenic nerve and intercostal nerves
Inspiratory center/dorsal respiratory group
1 of 2 respiratory nuclei in medulla oblongata that with more frequent firing cause more deep inhalation
Expiratory center/ventral respiratory group
1 of 2 respiratory nuclei in medulla oblongata that is involved with forced expiration
Pneumotaxic center
Part of pons that inhibits apneustic and inspiratory center/dorsal respiratory group to prevent overinflation of lungs during inspiration
Apneustic center
Part of pons that encourages and prolongs inspiration, continually active but overridden by pneumotaxic center to prevent overinflation
The apneustic and pneumotaxic centers do not ____ rhythms, but act as…
generate, …modifiers of established rhythm by the medullary centers (dorsal and ventral respiratory groups)
Respiratory control center mech of action
- Inspiratory center becomes active increasing AP’s to respiratory muscles and to pneumotaxic center
- After short delay, pneumotaxic center is stimulated to inhibit inspiratory and apneustic center
- inspiration ends and expiration begins
- pneumotaxic center activity declines back to baseline
- apneustic center and inspiratory center generate drive to begin the cycle anew
Irritant receptors of the lungs function
Lung receptors tat respond to inhaled irritants to result in bronchoconstriction or coughing by stimulating vagal afferents to medulla
Hering breur reflex (stretch receptors) function
Lung receptors that prevent excessive inflation by being triggered upon stretch to cease inspiration
J receptors function
Juxtapulmonary capillary receptors located near capillaries in alveolar septa, sensitive to increased pulmonary capillary pressure stimulates them to initiate rapid shallow breathing
Perpiheral chemoreceptors that monitor pH, PCO2 and PO2 of body fluids (2)
The aortic and carotid bodies that signal to the medulla via the vagus and glossopharyngeal nerves respectively
Central chemoreceptors function
Located on the surface of the medulla and primarily monitor the pH of CSF (and indirectly CO2 because of the relationship between CO2 levels and pH)
Increase in CO2 is related to a ___ in pH
Drop
In a patient with COPD with chronic elevated CO2 levels, peripheral chemoreceptors become…
Why is this clinically relevant?
…more sensitive to decreased O2 pressures
-don’t want to give positive pressure O2 to stop their respiration
Most important cause of pulmonary artery constriction is….
….low alveolar PO2 (hypoxia), to not waste blood in areas of the lung where gas exchange is not occurring but to shunt it and increase pressure to better ventilated areas
Why does emphysema lead to right sided heart failure?
Emphysema raises peripheral resistance to high levels and rises afterload of right side of heart causing failure
Primary control over resistance to airflow
Bronchiolar diameter
Valsalva maneuver
Involves contraciton of abdominal muscles while holding breath causing increased pressure in abdominal cavity to expel urine, feces, or aid in childbirth
State that shifts the oxyhemoglobin dissociation curve to the right
Exercise
