Respiratory Flashcards
What is directly proportional to the pressure difference between the mouth (or nose) and the alveoli?
Airflow
What is inversely proportional to airway resistance?
Airflow; the higher the airway resistance, the lower the airflow
What are some factors that change airway resistance?
- The major site of airway resistance is the medium- sized bronchi
- The smallest airway would seem to offer the highest resistance, but they do not because of their parallel arrangement
What is anatomical Dead Space?
The volume of the conducting airways; 150mL
What is tidal volume? TV
the volume inspired or expired with each normal breath
What is Inspiratory reserve volume? IRV
the volume that can be inspired over and above the tidal volume; used during exercise
What is Expiratory reserve volume? ERV
the volume that can be expired after the expiration of a tidal volume
What is Residual volume? RV
the volume that remains in the lungs after a maximal expiration
What is physiologic dead space?
volume of the lungs that does not participate in gas exchange; it is approximately equal to the anatomic dead space in normal lungs; may be greater than the anatomic dead space in lung diseases in which there are ventilation/ perfusion defects
What is alveolar ventilation?
Tidal volume- dead space X breaths/min
What is the inspiratory capacity?
the sum of tidal volume and IRV
What is Functional residual capacity (FRC)?
the sum of ERV and RV; the volume remaining in the lungs after a tidal volume is expired.
What is vital capacity, or forced vital capacity?
the sum of the tidal volume, IRV, and ERV; it is the volume of air that can be forcibly expired after a maximal inspiration
What is total lung capacity? TLC?
the sum of all four lung volumes; the volume of the lungs after a maximal inspiration; it cannot be measured by spirometry
What is FEV1?
The volume of air that can be expired in the first second of a forced maximal expiration. It is normally 80% of the forced vital capacity.
What are the muscles of inspiration?
External intercostals, sternocleidomastoid, serratus anterior, scalenes
What are the muscles during expiration?
rectus abdominus, and internal intercostals
What is compliance of the respiratory system?
- Describes the distensibility of the lungs and the chest wall
- inversely related to elastane
- inversely relate to stiffness
- is the change in volume for a given change in pressure. Pressure refers to transmural or transpulmonary pressure (the pressure difference across pulmonary structures)
What is transmural pressure?
alveolar pressure- intrapleural pressure
What happens when the pressure outside of the lungs (intrapleural pressure) is negative?
the lungs expand and lung volume increases
What happens when the pressure outside of the lungs (intrapleural pressure) is positve?
The lungs collapse and lung volume decreases
What happens when the lungs are at rest?
Lung volume is at FRC (volume remaining in lungs after tidal volume) and the pressure in the airways and lungs is equal to atmospheric pressure (i.e. zero).
What happens when the lungs are at rest, under equilibrium conditions?
There is a collapsing force on the lungs and an expanding force on the chest wall. At FRC these two forces are equal and opposite. The combined lung- chest wall system neither wants to collapse nor expand.
When the lungs are at rest, under equilibrium conditions, what is the pressure of the intrapleural space?
As a result of the two opposing forces, the intrapleural pressure is negative.
What is a Pneumothorax?
When air is introduced into the intrapleural space; the intrapleural pressure becomes equal to the atmospheric pressure; and the lungs will collapse and the chest wall will spring outward.
What happens with a patient with emphysema?
Their lung compliance will increase; and the tendency of the lungs to collapse is decreases. The lung- chest wall system will seek a new, higher FRC so that the two opposing forces can be balanced; the patients chest wall becomes barrel-shapped.
What happens with a patient with Fibrosis?
Lung compliance is decreased and the tendency of the lungs to collapse is increased. At the original FRC, the tendency of the lungs to collapse is greater than the tendency of the chest wall to expand. The lung- chest wall system will seek a new, lower FRC so that the two opposing forces can be balanced.
Surface tension of the alveoli results in what?
results from the attractive forces between liquid molecules lining the alveoli.
What kind of alveoli have a low collapsing pressure and are easy to keep open?
Large alveoli (large radii)
What kind of alveoli have high collapsing pressures and are more difficult to keep open?
Small alveoli (small radii)
In the absence of surfactant, which alveoli have a tendency to collapse?
Small Alveoli
How does surfactant reduce the surface tension?
disrupting the intermolecular forces between the liquid molecules. It prevents the small alveoli from collapsing and increases compliance.
How is surfactant synthesized?
Type II alveolar cells
Surfactant may be present as early as gestational week___?
24
What does contraction or relaxation of bronchial smooth muscle change?
Changes airway resistance by altering the radius of the airways
What does parasympathetic stimulation do to the bronchial smooth muscle?
constrict the airways, decrease the radius, and increase the resistance to airflow; also done by the slow- reacting substance of anaphylaxis (asthma)
What does sympathetic stimulation do to the bronchial smooth muscle?
Sympathetic stimulation and sympathetic agonist (isoproterenol) dilate the airways via Beta 2 receptors, increase the radius, and decrease the resistance to airflow
What are high lung volumes associated with?
greater traction and decreased airway resistance. Patients with increased airway resistance (e.g. asthma) “ learn” to breathe at higher lung volumes to offset the high airway resistance
What are low lung volumes associated with?
less traction and increased airway resistance, even to the point of airway collapse.
What changes the resistance to air flow?
Viscosity or density of inspired air
What happens when the lungs are at rest (before inspiration begins)?
The alveolar pressure equals atmospheric pressure; because lung pressure are expressed relative to atmospheric pressure, the alveolar pressure is said to be zero
The intrapleural pressure is negative
- The opposing forces of the lungs trying to collapse and the chest wall trying to expand create a negative pressure in the intrapleural space btwn them
- Lung volume is the FRC
What happens during inspiration?
- Inspiratory muscles contract and volume of the thorax increases
- As lung volume increases, the alveolar pressure decreases to less than atmospheric pressure
- The pressure gradient between the atmosphere and the alveoli now causes air to flow into the lungs; airflow will continue until the pressure gradient dissipates
- The intrapleural pressure becomes more negative; because lung volume increases during inspiration, the elastic recoil strength of the lungs also increases.
What are changes in the intrapleural pressure during inspiration used to measure?
dynamic compliance of the lungs
At the peak of inspiration, lung volume is the FRC plus one___?
TV
What happens during expiration?
- Alveolar pressure becomes greater than atmospheric pressure; because alveolar gas is compressed by the elastic forces of the lung.
- The pressure gradient is reversed, and air flows out of the lungs
- Intrapleural pressure returns to its resting value during a normal (passive) expiration
What happens during a forced expiration?
Intrapleural pressure actually becomes positive. This positive intrapleural pressure compresses the airways and makes expiration more difficult.
What happens with patients with COPD?
airway resistance in increased, patients learn how to expire slowly with “pursed lips” to prevent the airway collapse that may occur with a forced expiration
What is asthma?
obstructive disease in which expiration is impaired
What is COPD?
an obstructive disease with increased lung compliance (less elasticity) ; in which expiration is impaired
What is Fibrosis?
restrictive disease with decreased lung compliance (More stiffness, more elasticity) in which inspiration is impaired.
What do the diffusion rates of O2 and CO2 depend on?
The partial pressure difference across the membrane and the area available for diffusion
What happens with the diffusion- limited exchange for patients with Fibrosis?
the diffusion of O2 is restricted because thickening of the alveolar membrane increases diffusion distance.
What happens with the diffusion- limited exchange for patients with emphysema?
the diffusion of O2 is decreased because the surface area for diffusion of gases is decreased.
How is oxygen transported?
O2 is carrie din blood in two forms: dissolved or bound to hemoglobin.
What at its normal concentrations, increase the O2 carrying capacity of blood 70-fold?
Hemoglobin
What is the O2 binding capacity of blood?
max amount of O2 that can be bound to hemoglobin in blood. It is dependent on the hemoglobin concentration in blood, it limits the amount of O2 that can be carried in blood, is measured at 100% Saturation
What is the O2 content of blood?
the total amount of O2 carried in blood, including bound and dissolved O2, depends on the hemoglobin concentration, to PO2 and the P50 of hemoglobin.
What is the hemoglobin- O2 dissociation curve a plot of?
It is a plot of percent saturation of hemoglobin as a function of PO2
What is P50 represent?
The PO2 at 50% saturation; which means that on average, tow of the four heme groups of each hemoglobin molecule have O2 bound.
What is the sigmoid shape of the curve a result of?
change in the affinity of hemoglobin as each succesive O2 molecule binds to a heme site (called positive cooperatively).
What happens when there is a shift to the right in the oxygen hemoglobin curve?
Occurs when the affinity of hemoglobin for O2 is decreased.
P50 is increased; unloading of O2 from the arterial blood to the tissues is facilitated
- Increases in PCO2 or decreased in pH
-Increases in temperature (during exercise)
- Increases in 2,3-DPG concentration
What happens when there is a shift to the left in the oxygen hemoglobin curve?
Occurs with the affinity of hemoglobin for O2 is increases. P50 is decreased; unloading of O2 from arterial blood into the tissues is more difficult - Decreased PCO2 - Increased pH -Decreased temperature -Decreased 2,3- DPG conc -HbF -Carbon monoxide poisoning
What is hypoxemia?
decrease in arterial PO2
What is hypoxia?
decreased O2 delivery to the tissues
What can cause hypoxia?
decreased cardiac output, decreased O2- binding capacity of hemoglobin, decreased arterial Po2
Where is CO2 produced?
Produced in the tissues and carried to the lungs in the venous blood in three forms:
- Dissolved CO2 (Small amount) which is free is solution
- CO2 bound to hemoglobin
- HCo3- which is the major form 90%
What is generated in the tissues and diffuses freely into the venous plasma and then into the RBC’S?
CO2
Once CO2 is in the RBS’s what happens?
In the RBC’s, CO2 combines with H2O to form H2CO3, a reaction that is catalzyed by carbonic anhydrase. H2CO3 dissociates into H+ and HCO3-
What happens to the HCO3-?
HCO3- leaves the RBC’s in exchange for Cl- (chloride shift) and is transported to the lungs in the plasma.
What is the major form in which CO2 is transported to the lungs?
HCO3-
Pressures in the pulmonary circulation are____ in the systemic circulation.
Lower
What is also much lower in the pulmonary circulation than in the systemic circulation?
Resistance
Cardiac output of the right ventricle is____ ____ _____.
Pulmonary blood flow
Cardiac output of the right ventricle is equal to cardiac output of the ____ _____?
Left Ventricle
When a person is _____, blood flow is nearly uniform throughout the lung.
Supine
When a person is _____blood flow is unevenly distributed because of the effects of gravity.
standing
T/F Blood flow is the lowest at the apex of the lung (zone 1) and highest at the base of the lung (zone 3)
True
Zone 1
blood flow is the lowest; the higher alveolar pressure may compress the capillaries and reduce blood flow.
Zone 2
blood flow is medium; arterial pressure is greater than alveolar pressure, and the blood flow is driven by the difference between arterial pressure and alveolar pressure.
Zone 3
Blood flow is highest; blood flow is driven by the difference between arterial and venous pressure, as in most vascular beds.
When can zone 1 blood flow be present?
If arterial blood pressure is decreased as a result of hemorrhage or if alveolar pressure is increased because of positive pressure ventilation .
In the lungs hypoxia causes what?
Vasoconstriction; redirects blood away from poorly ventilate, hypoxic regions of the lung and towards well- ventilated regions.
What is the V/Q ratio?
the ratio of alveolar ventilation (v) to pulmonary blood flow (Q) (perfusion). Ventilation and perfusion matching is important to achieve the ideal exchange of O2 and CO2. Normal V/Q is 0.8. This V/Q results in an arterial PO2 of 100mmHg and an arterial PCO2 of 40 mmHG
What is the lowest in the apex and highest at the base because of gravitational effects?
Blood Flow
T/F The V/Q ratio is higher at the Apex of the lung and lower at the base of the lung.
True
T/F At the apex (higher V/Q), PO2 is highest and PCO2 is lower because gas exchange is more efficient.
True
T/F at the base (lower V/Q) PO2 is lowest and PCO2 is higher because gas exchange is less efficient.
True
What is a shunt?
If the airways are completely blocked, then ventilation is zero. If blood flow is normal, then V/Q is zero, which is called a shunt. There is no gas exchange in a lung that is perfused but not ventilated. The PO2 and PCO2 of pulmonary capillary blood will approach their values in mixed venous blood.
What happens to the V/Q ratio in pulmonary embolism?
If blood flow to a lung is completely blocked, then blood flow to that lung is zero. If ventilation is normal, then V/Q is infinite, which is called dead space. There is no gas exchange in a lung that is ventilated but not perfused. The PO2 and PCO2 of alveolar gas will approach their values in inspired air.
What is the Bohr effect?
A decrease in the amount of oxygen associated with hemoglobin and other respiratory compounds in response to a lowered blood pH resulting from an increased concentration of carbon dioxide in the blood.
What is the Haldene effect?
oxygenation of blood in the lungs displaces carbon dioxide from hemoglobin which increases the removal of carbon dioxide. Oxygenated blood has a reduced infinity for carbon dioxide.
Alveoli oxygen concentration and partial pressure is controlled by?
- The rate of absorption of oxygen into the blood
2. The rate of entry of new oxygen into the lungs by the ventilatory process.
Blood becomes almost saturated with oxygen by the time it has passed through ___ of the pulmonary capillary.
1/3
What can diffuse about 20 times as rapidly as oxygen?
Carbon dioxide
Where is respiratory drive generated in?
The brainstem
The respiratory drive is modulated by what?
- Conscious inputs from the cortex (medulla and pons)
- Influences from the limbic system and reticular activating system
- Chemoreceptors
- Metaborecpetors
- Mechanorecpetors
What do the chemoreceptors sense?
They sense changes in the chemical constituents of blood, primarily CO2 and H+ (pH)
- Central (brainstem)
- Peripheral (carotid and aortic bodies)
Where are the metaboreceptors located?
in muscle
Where are the mechanoreceptors located?
in the lung
What is the Hering- Bruer Reflex?
Reflex inhibition of inspiration triggered by pulmonary stretch receptors upon expansion of the lungs and mediated by the vagus nerve
What are rCPG’s? (Respiratory central pattern generator)
Within the medulla and pons, interconnected neuronal networks; form the rCPG which generate the respiratory rhythm.
What do the rCPG’s do?
They generate the respiratory rhythm. Afferent signals from lung mechanoreceptors and peripheral chemoreceptors enter this pontomedullary network via the nucleus of the solitary tract (nTS)
-The rCPG drives the activity of spinal phrenic, intercostal, and lumbar motor neuron pools that innervate the muscles of respiration.
T/F the RCPG can be influenced by higher CNS structures, to allow for conscious control of the ventilatory pattern.
True; you can think about breathing more or less
What are the two components of the respiratory CPG?
- The pre- Botxinger complex (pre-BotC), located within the medullary ventral respiratory column (VRC) is considered a major source of rhythmic inspiratory activity.
- The pre-BotC, interacts with the adjacent Botzinger complex (BotC) containing mostly expiratory neurons
What is the advantage of the ramping of the nervous signal to control breathing?
It causes a steady increase in the volume of the lungs during inspiration, rather than inspiratory gasps which helps keeps flow of air more consistent
The nervous signal that is transmitted to the inspiratory muscles, mainly the diaphragm, is _____ an instantaneous burst of action potential instead it functions as a ramp signal.
NOT
The respiratory centers in the pons and the medulla_____ independently modulate breathing in the context of emotional challenges.
Cannot; it requires input from higher brain centers
hat integrates visual, auditory, olfactory, and somatosensory info and informs subcortical structures about the results?
Prefrontal cortex; Amygdala, hypothalamus, and finally the midbrain periaquctalgray (PAG)
What does PAG do?
Generates the final motor output for basic survival
What is PAG strongly influenced by?
the limbic system and prefrontal cortex
What does PAG also control?
Heart rate, blood pressure, micturition, sexual behavior, vocalization, and many other basic motor output systems
What structure changes the eupneic (resting) respiratory rhythm into a breathing pattern necessary for basic survival?
PAG
What does exercise do to O2 and CO2 production?
Exercise increases O2 consumption and CO2 production.
Minute ventilation ____ with the level of exercise; it ____ linearly with both oxygen consumption and carbon dioxide production up to a level of about 60% VO2max.
increases
What causes the increase in ventilation above oxygen consumption at high work levels?
Caused by the increased metabolites from anaerobic metabolism
The increase in minute ventilation during exercise is usually a result of what?
increases in both tidal volume and rate; initially tidal volume increases more than the rate of respiration- as metabolic acidosis develops, the increase in breathing rate predominates
