Resp. 2 - Resp cycle and dynamics of vent Flashcards
Spirometry
• The drum is calubrated and as the person breathes, it measures how much air enters and leaves
Lung volumes
• Tidal volume
• Expiratory reserve volume
• Inspiratory reserve volume
•
• Tidal volume →
the volume of air moved IN OR OUT of the respiratory tract (Breathed) during each ventilatory cycle.
• Expiratory reserve volume →
the additional volume of air that can be forcibly exhaled following a normal expiration; it can be accessed simply by expiring maximally to the Maximum Voluntary Expiration.
• Inspiratory reserve volume →
the additional volume of air that can be forcibly inhaled following a normal inspiration; it can be accessed simply by inspiring maximally, to the Maximum Possible Inspiration
Residual volume →
the volume of air remaining in the lungs after a Maximal Expiration; it cannot be expired no matter how vigorous or long the effort; RV cannot be measured with a spirometry test; RV = FRC - ERV
(Always a small volume of air remaining in the lungs – prevents collapsing of the alveoli)
Capacities:
- Vital capacity (VC)
- Inspiratory capacity (IC)
- Functional Residual Capacity (FRC)
- Total Lung Capacity (TLC)
• Vital capacity (VC) →
the maximal volume of air that can be forcibly exhaled after a Maximal Inspiration; VC = TV + IRV + ERV
• Inspiratory capacity (IC) →
the maximal volume of air that can be forcibly inhaled; IC = TV + IRV
• Functional Residual Capacity (FRC) →
the volume of air remaining in the lungs at the end of a normal expiration; FRC = RV + ERV
• Total Lung Capacity (TLC) →
the volume of air in the lungs at the end of a Maximal Inspiration; TLC = FRC + TV + IRV = VC + RV
What can we not measure with the spirometer
• We cannot measure residual volume with the spirometry test and as a result we cannot measure all the capacities that have residual volume as a component of the capacity itself.
Inspiration:
CNS sends an excitatory drive to the muscles of inspiration (diaphragm) → muscles contract = increase in the thoracic volume → intrapleural pressure becomes more negative → transpulmonary pressure (which is dependent on the intrapleural pressure) increases → increase in lung volume → decrease the alveoli pressure → alveoli pressure will be smaller than the atmospheric pressure → a difference in pressure generates movement of gas → gas will move from a region of high pressure to a region of low pressure → alveolar pressure is smaller so air will move from the atmosphere into the lungs
Expiration:
Relaxation of the inspiratory muscles → chest wall recoils (goes back to its resting state) → intrapleural pressure moves back to a pre-inspiratory value→ as transpulmonary pressure is equal to the alveolar pressure minus the intrapleural pressure, the transpulmonary pressure will also will be reduced as the intrapleural pressure returns to pre-inspiratory values → as transpulmonary pressure is also linked to lung volume, lungs recoil and a reduce volume, generating compression of the gas molecules inside the alveoli → increase in alveolar pressure so it is greater than the atmospheric pressure → air will move from a region of high pressure to a region of low pressure, flowing out of the lungs to the environment
All points follow Boyles Law, accept for 2 points in inspiration and 2 in expiration, where they follow ideal gas law, this is because at these point your chnaging the # of mol. of gas at these points
- point B where vol. INC. and aveolar press. INC.
* point D where vol. DEC. as aveolar press. DEC.
The types of ventilation measurements
- Minute ventilation (Vf) = RR x Vt
- Alveolar ventilation (Va) = PPx(vt-Vd)
- DEADSPACE ventilation (Vd)
Tachypnea:
rapid breathing (rate) / shallow breathing / hyperventilation
- no alveolar ventilation = no gas exchange
- reduced tidal volume, increased rate
Deep breathing
High tidal volume, low rate = very high alveolar ventilation = lots of gas exchange
Hyperpnea:
any increase in breathing rate and/or depth (e.g., exercise)
• Compliance gives indication of
stiffness or rigidity of structure
- LOW COMPLIENCE = stiff / rigid (not good, cuz takes more E to expand it)
- HIGH COMPLIENCE = less stiff, requires less E to inflate or deflate.
Formula for compliance
C= DELTA V / DELTA P
DELTA P = Ptp
Ptp = Pa = Pip
lung compliance:
- determined by both dynamic and static properties
- Occurs in the absence or presence of airflow
- Measure of elasticity
• The proprieties of the lung are diff when you expire VS inspire, that’s why the curves aren’t exactly the same, this is called
hysteresis.
Hysteresis curve gives info on COMPLIENCE. Now we have lung COMPLIENCE during inflation or expiration.
If the curve is more to the right, tends to be
Less compliant
Is inflation or expiration have more compliance
- Inflation curve is less compliant. at point 2, only 25% lung capacity
- Expiration curve is more compliant, at point 2, its at around 80% lung capacity.
What determines compliance
Surface tension
Why is there less surface tension during deflation then inflation
Deflation contains more surfactin
• When the lungs were INFLATED with liquid, the hysteresis was
eliminated, and all the curves shift to the left = greater compliance, its more compliant then expiration because the liquid inside eliminated surface tension.
What do you need for surface tension to exist?
• you need an air-water interface for surface tension to exist.
That’s why when u inflate lung with liquid, ST is gone.
a measure of the attracting forces acting to pull a liquid’s surface molecules together at an air-liquid interface
- would cause alveoli to collapse as they contain liquid
- produce elastic recoil of lungs
Surfactant is a
phospholipid, has hydrophilic head, oriented towards water, and hydrophobic tails that’s orientated away from water.
How does surfactant work?
The overall effect of positioning the surfactant at the interface is that it breaks the strong attractive forces that occur between the molecules of water at the
surface
Does emphysema give more or less compliance and why?
More compliance
- due to smoke = destroy lung tissue = elasticity
- Inhalation = easy. Exhalation = hard
Does fibrosis give more or less compliance and why?
Less compliant
= stiff lungs require more E to inhale
- more surface tension and less surfactant
- overproduction of callogen
Increased resistance in the tissues does what to airflow
Is decreases airflow, therefore, when R INC, it takes a lot more E to move the same V of air into and out of the lungs.
