Respiratory Physiology Flashcards
What is quite breathing
Quite breathing is made in volume of air we breath in and out naturally = tidal volume
Tidal volume in healthy adult is 500 mL of gaz per movement
When we inhale and retain what volume do we reach ?
Total lungs’ capacity
Do we expulse all the air from the lungs when we exhale ?
No, there is a residual volume
Is the respiratory system an external or an internal organ ?
External organ
What are the functions of the respiratory system ?
- provide oxygen to the body tissues
- remove carbon dioxyde
- help maintenant pH balance of the blood
- sensing odors
- voice production
- defense against the pathogens
- pulmonary ventilation
- gaz exchange between air and blood
- transportation of gases to tissue
- gaz exchange between the blood and tissues
What is systemic respiration ?
It’s the exchange of O2 and CO2 between atmosphere and organs
What is pulmonary ventilation ?
Inspiration and expiration
What is the connexion between respiration and ventilation ?
Aerobic respiration requires O2
O2 is provided by the gaz exchanges provoked by ventilation
Which parts of the NS control the ventilation ?
Mainly neurons in the reticular formation of the pons and medulla
The medulla sets the ventilation rhythm and the pons influences and modifies the activity of the medullary neurons
What are the 2 neurons’ clusters essential to ventilation ? Where are they located ?
In the medulla oblongata
- dorsal respiratory group
- ventral respiratory group
What is the function of the ventral respiratory group of neuron influencing the ventilation ?
- rhythm generative and integrative center
- when inspiratory neurons fire : impulses travel along the phrenic and intercostal nerves to excite the diaphragm and external intercostal muscles. As a result, the thorax expands and air rushes into the lungs
- when expiratory neurons fire : inspiratory signal is inhibited and expiration happens passively as the inspiratory muscles relax and the lungs recoil.
What is the function of the dorsal respiratory group of nerves influencing ventilation ?
They integrate peripheral sensory inputs and modify the rhythm generated by the ventral respiratory group of nerves.
What is the role of pontine respiratory centers ?
They influence and modify the activity of medullary neurons
They smooth out the transition between inspiration and expiration
They modify and fine-tune the breathing rhythm generated by the ventral respiratory group during specific activities such as vocalization, sleep and exercise.
What are the chemical factors influencing volume and frequencies of ventilation ?
- changing volume of O2, CO2 in the arterial blood
- chemoreceptors in the brain stem : central chemoreceptors located in the brain stem and peripheral chemoreceptors located in aortic arch and carotid artery.
What are the neural controls exerted on ventilation ?
- hypothalamic controls acting through hypothalamus and the rest of the limbic system, triggered by strong emotions and pain and impact the respiratory rate and depth.
- cortical controls is a volitional control over the rate and depth of our breath
What vessel brings deoxygenated blood to the alveoli ?
The pulmonary artery
In which part of the internal airways do gaz exchange take place ?
In the respiratory zone composed of respiratory bronchi, alveolar ducts and alveoli
What happens when the diaphragm contracts ?
It moves downward to become flat. The rib cage expends.
What is the atmospheric pressure ?
The pressure exerted by gaz present in the air
Pn = 78%
PO2 = 21%
Pother gaz = 1%
Atmospheric pressure = 760 mmHg at sea level
What is the relation between atmospheric pressure and intrapulmonary pressure during inspiration ?
Patm > Palv
What is the relation between atmospheric pressure and intrapulmonary pressure during expiration ?
Palv > Patm
What happens to pressure in alveoli when inhalation takes place ?
Pressure in the alveoli drops
What happens to pressure in the alveoli when the exhalation takes place ?
Pressure rises
What is the relation between atmospheric pressure and intra pulmonary pressure during pause ?
They equalize
What adjective can describe the pressure in the pleural cavity ?
Subatmoshperic
What happens to the pressure in the pleural cavity during inhalation / exhalation ?
Pressure drops during inhalation
Pressure rises during exhalation
Why is the pleural pressure negative ?
- tendency of thorax to expend outwards
- tendency of lungs to recoil inward
To what is equal trans pulmonary pressure ? What will cause its increase ?
P alv - P ip
The alveoli expand
What is the pressure gradient during breathing ?
During each breath, the pressure gradient moves 0, 5 liter into and out of the lungs
What is the relation between the pleural pressure and alveolar pressure at rest ? What is the relation between both at the end of inspiration ?
It’s the same
How does gravity acts on ventilation ?
Gravity and the weight of the lungs act on ventilation by increasing the pleural pressure at the base of the lungs (making it less negative) and thus reducing the volume of the alveoli - it is dépendant on the position !
What is the name of the base of lungs in relation with gravity ?
The dependent zone
In which part of the lung is the pleural pressure the most negative ?
In the apex
In which part of the lung do we ventilate ?
The dependent zone
What is Boyle’s law ?
The pressure is inversely related to the volume (in constant temperature in a closed system)
Gaz will move from a high pression region to a low pressure region.
Define respiration
Exchange of gaz between the environnement and the cell tissue, through external respiration taking place between alveoli and capillary and through internal respiration taking place at capillary-tissue level.
Define ventilation
Gaz movement between the outside and the alveoli
Expressed in movement per minute :
Ventilation = volume of air x frequency (number of breath per minute)
What is the usual ratio between cardiac output and ventilatory output ?
Q/V = 1
What is the relation between alveolar ventilation and pressure of CO2 ?
Inverse relation
In the respiratory tract, how are non respirating structures called ?
Dead space
What are the types of “dead space”
- physiological dead space
- anatomical dead space
Define anatomical dead space
Structures of the intrathoracic airways not meant for respiration such as the main bronchi
Define physiological dead space
Structures of the respiratory tract meant for respiration, like the alveoli, but which are not functioning.
What is a shunt unit ?
In the couple alveoli and capillary : there is perfusion but no ventilation
What is collateral ventilation ? What are the 3 types ?
The communications between alveoli and all ends of the respiratory system
- interbronchiolar pathways of Martin
- Bronchiole-alveolar communication of Lambert
- interalveolar pores of Kohn
What is hyperventilation ?
Increasing of exhaled volume
Increasing elimination of CO2
Leads to hypocapnea
What is hypoventilation
Reduction of alveolar ventilation
Reduction of tidal volume
Causes hypercapnea
What is tachypnoea ?
Increased respiratory rate > 20 movements per minute (=increase of respiratory frequency)
What is bradypnoea ?
Reduction of the respiratory rate < 20 breath per minute
What is apnea ?
Cessation of breathing
What is the normal volume of CO2 in the alveoli ? What happens if it drops ?
- 40 mmHg
- blood becomes more basic, there is an increase in pH
Give a synonyme of deep breath
Laminar breath
What are the physical factors influencing ventilation ?
- airways resistance
- lungs compliance
- alveolar surface tension
- frequency
- quality of flow (turbulent/ laminar)
To what airways resistance is dependent ?
It’s dependent on the calibre of the airway
What happens if the alveoli merge ?
Less surface for gaz exchange to take place
Gaz accumulation
Increased gaz resistance
Pathologic
What is Poiseuille’s law ?
Resistance (R) through airways depends on :
- gaz viscosity (n)
- length of type (l)
- radius of type (r)
R = (8nl)/ pi r cube
What are the consequences of pathologic decrease of airways caliber ?
Increased airway resistance
Reduced airflow
Increase breathing work
Breathlessness
Define work of breathing ?
WOB = work done during inspiration to overcome the resistive and elastic forces of airways, lungs and chest walls.
WOB uses 2-5% of total O2 at rest
What is compliance ?
Willingness of elastic structure to distend
What influences lungs’ compliance ?
- lungs distencibility
- alveolar surface tension
Define pulmonary surfactant
Is a surface active lipoprotein complex formed by pneumocytes II
It reduces the surface tension in alveolus and maintains it open
What are the different lung capacities ?
- inspiratory reserve volume (ca 3L)
- tidal volume (ca 0,5L)
- expiratory reserve volume (ca 1,7L)
- residual volume (ca 1,3L)
What capacities are included in total lung capacity ?
- inspiratory reserve volume
- tidal volume
- expiratory reserve volume
- residual volume
Which capacities are included in the vital capacity
- inspiratory reserve volume
- tidal volume
- expiratory reserve volume
What capacities composes the inspiration capacity ?
Inspiratory reserve volume
Tidal volume
Which capacities compose the functional residual capacity ?
- expiratory reserve volume
- residual volume
Define tidal volume
Vt = movement of air during quiet breathing
Define Expiratory reserve volume
ERV extra air pushed out of the lungs beyond tidal volume after full exhalation
Define inspiratory reserve volume
IRV extra air drowned in beyond Vt after full inhalation
Define residual volume
RV air remaining in lungs after full exhalation
What is Fick’s law of diffusion ?
Rate of transfer of a gaz through a sheet of tissue is proportional to :
- tissue area
- difference in gaz partial pressure between the two sides
- concentration/pressure gradients
- diffusion constant
- gaz solubility
- transit time red blood cells
- ventilation / perfusion coupling
Is inversely proportional to:
- tissue thickness
Is ventilation even in the lungs ? Why ?
No
Ventilation is not distributed evenly in the lung because of gravity and weight of the lungs and increased pleural pressure at the base.
In the apex the alveoli are so inflated that they compress the capillaries and stop perfusion
Apex :
PA>Pa>Pv
Midzone:
Pa>PA>Pv
Base:
Pa >PV>PA
Where does optimal ventilation happen ?
Lower third of the lungs
Alveoli are partially expended and volume can still increase
What happens in the intermediate zone of the lungs during systole and diastole ?
During systole : the pressure in the capillary rises which allows the perfusion
During diastole : the pressure in the capillary drops which stops the perfusion
What is a shunt
When a fraction of cardiac output is not exposed to gaz exchange
Regarding the ventilation/perfusion matching, what are the local auto regulatory mechanisms ?
Efficiency + synchronisation V/Q
Hypoxemic pulmonary vasoconstriction
Pulmonary capillary recruitment
Bronchial response
