Respiratory Physiology Flashcards
Pulmonary ventilation?
BREATHING! – inspiration + expiration
What is Atmospheric pressure? and number that it is specifically measured by?
This is the pressure exerted by air around the body!
= 760 mm Hg sea level
Respiratory pressures are described relative to what?
Relative to atmospheric pressure. (Reminder: atmospheric pressure=760 mmHg)
What’s an example of negative respiratory pressure?
-4 mm Hg respiratory pressure = 760-4 = 756 mm Hg
What is Intrapulmonary Pressure?
- pressure within the alveoli of lungs
- rises and falls with breathing but always eventually equalizes with atmosphere
What is intrapleural Pressure?
This is the pressure within the pleural cavity
It fluctuates with breathing
When it comes to Intrapleural Pressure is it always a POSITIVE or NEGATIVE pressure?
ALWAYS a NEGATIVE pressure
With the Intrapleural pressure what are the 3 factors of interaction?
- natural tendency of lungs to recoil
- surface tension of alveolar fluid
- opposed by elasticity of chest wall pulls thorax outwards
What is the net result of intrapleural pressure?
Negative intrapleural pressure
Any condition equalizing intrapleural pressure with intrapulmonary pressure causes what?
causes immediate lung collapse!
If one lung collapses do both lungs collapse?
No! One can collapse while the other may not because of the separation of the pleural cavities
Transpulmonary pressure
Intrapulmonary (P_pul) minus intrapleural (P_ip) pressure: (Ppul − Pip) this keeps the lungs from collapsing
What does Pulmonary Ventilation consist of? and what does this mechanical process depend on?
It consists of inspiration and expiration.
It depends on volume changes in the thoracic cavity
What do volume changes lead to?
pressure changes
What do pressure changes lead to?
Leads to flow of gases to equalize pressure
What is Quiet Inspiration?
Active process involving inspiratory muscles
Explain it!
The action of the diaphragm: it moves inferiorly and flattens out –> increasing in thoracic volume
The action of intercostal muscles: external intercostals contract, rib cage is lifted up and out –> in an increase in thoracic volume
Quiet Expiration
normally is passive process
- depends more on elastic recoil of lungs than on muscle contraction
- inspiratory muscles relax, thoracic volume decreases, and lungs recoil
- volume decrease causes intrapulmonary pressure to increase by +1mm Hg
- Ppul > Patm so air flows out of lungs down its pressure gradient until Ppul = Patm
What are Forced (deep) inspirations?
Accessory muscles (neck and chest) raise ribs more; extend back by straightening spine
What is Forced expiration? (2 parts)
- contract abdominal wall muscles: increase intra-abdominal pressure
- depress rib cage using internal intercostal muscles
What are the physical factors influencing Pulmonary ventilation?
Airway resistance / alveolar surface tension / lung compliance
What is Airway resistance?
the change in transpulmonary pressure needed to produce a unit flow of gas through the airways of the lung.
Why is airway resistance insignificant in healthy individuals? (3 reasons)
- airway diameter at beginning are large
- airway diameter decreases, the number of branching pathways increases
- gas flow stops at terminal bronchioles (diffusion), at this level, resistance is no longer an issue
What is the formula for Gas flow?
Gas flow = ΔP/R
(P=pressure;R=resistance)
What are the 2 neural influences? (3rd bonus)
- Parasympathetic
- Sympathetic
Bonus: disease
How does parasympathetic have a neural influence?
constricts bronchioles also occurs during acute asthma attack
How does sympathetic have a neural influence?
dilates bronchioles
How does disease have a neural influence?
these can be sources of airway resistance
What is Alveolar Surface tension?
At any gas/liquid boundary, molecules of liquid more strongly attracted to each other than to the gas –> tension at liquid surface
Water has a very high surface tension. What does Water have to be IN to cause a collapse?
Alveoli
What is Surfactant?
It is a detergent-like lipoprotein produced by type II cells; it interferes with cohesiveness of water molecules»_space; less energy to overcome surface tension
What is Infant respiratory distress syndrome?
This is when premature babies produce too little surfactant. They experience this increased surface tension which results in the collapse of alveoli after each breath/alveoli must be re-inflated with every breath
What is the treatment for Infant respiratory distress syndrome?
Spraying natural or synthetic surfactant into newborn’s air passages.
Positive pressure devices also help to keep alveoli open between breaths
What is Lung Compliance?
The ease with which lungs can be distended. The more a lung expands for a given increase in transpulmonary pressure, the greater its compliance
What does distensibility mean?
The capacity to swell as a result of pressure from the inside.
What are the two things that lung compliance depends on?
- distensibility of lung tissue
- alveolar surface tension (reduced by surfactants.)
Finish the sentence…
The more a lung expands for a given increase in transpulmonary pressure
The greater its compliance
Compliance is diminished by any factor that: (3)
- reduces natural resilience of lungs
- increases surface tension of alveolar fluid
- impaired flexibility of thoracic cage
What is elasticity of lungs important for?
Both inspiration and expiration
Assessing Ventilation
- several respiratory volumes can be used to assess respiratory status
- can be combined to calculate respiratory capacities, which can give information on person’s respiratory status
When are respiratory volumes and capacities usually abnormal?
in people with pulmonary disorders
What was the original, cumbersome clinical tool used to measure patient’s respiratory volumes
SPIROMETER
Respiratory volumes involve what four volumes?
- Tidal volume (TV)
- Inspiratory reserve volume (IRV)
- Expiratory reserve volume (ERV)
- Residual volume (RV)
Tidal volume
Amount of air moved into and out of lung with each breath
Inspiratory reserve volume
amount of air that can be inspired forcibly after the tidal volume
Expiratory reserve volume
amount of air that can be forcibly expelled from lungs after tidal volume
Residual volume
amount of air that always remains in lungs
Respiratory Capacities (4)
- Inspiratory capacity
- Functional residual capacity
- Vital capacity
- Total lung capacity
