What is ventilation?
The process of moving gas (air) in and out of the lungs
Why is ventilation regulated? In disease and respiratory care
- To meet the body's need under a wide range of conditioning
- 1. In disease, inadequate ventilation or an increased WOB results
- 2. Respiratory care modalities try to reduce WOB and provide artifical ventalation if neccessary
Complex physiological process at the blood and cellular levels
What are the 2 phases of ventilation?
- Inspiration and expiration
- During each cycle, volume gas moves in and out of the respiratory tract
What is Vt?
- Tidal volume
- Amount of gas that moves in and out of the respiratory tract
- Normal Vt refreshes the gas present in the lung removing CO2 and supplying O2
What are the 3 different pressure gradients?
- Transrespiratory- Difference in pressure between atmosphere (body surface) and alveoli; causes gas to flow in and out of alveoli
- Transpulmonary- Difference between alveoli and pleural space; keeps alveoli open
- Transthoracic- Difference in pressure between pleural space and body surface; total pressure needed to expand or contract the lungs
What are the different kinds of pressures throughout the lungs?
- Alveolar pressure
- Pleural pressure
- Mouth pressure
- Body surface pressure
What is transpulmonary pressure?
Difference between alveoli and pleural space; keeps alveoli open. pressures vary
What is Transrespiratory pressure?
Difference in pressure between atmosphere (body surface) and alveoli; causes gas to flow in and out of alveoli
What is Transthoracic pressure?
Difference in pressure between pleural space and body surface; total pressure needed to expand or contract lungs
What are the 2 forces of lung inflation has to work against?
- Elastic forces: the tissues of the lungs and thorax along with the surface tension in the alveoli
- Frictional forces: resistance caused by gas flow and tissue movement
Without surfactant, what would happen to alveoli?
alveoli collapsewithout surfactant, decrease surface tension, and provide alveoli stability.
What is pleural pressure before inspiration (no gas flow)? alveolar pressure?
-5 cmH2O and 0cmH2O
What is the normal value for compliance?
What does compliance mean?
- Measures the distensibility of the lungs
- "Stretch out"
- How far a lung can be expanded to
How do we measure good compliance?
Cl = Vt/P
In emphysema, compliance __________ and elastic tissue ___________.
increases, decreases or drops
In fibrosis, compliance __________ and elastic tissue ___________.
decreases, increases or raises
What is elastance?
- Property of resisting deformation
- "Back to original shape"
When does airway resistance happen?
- It occurs when the system is in motion
- Has 2 components:
- 1. Tissure viscous resistance: impedance of motion caused by displacement of tissues (lungs, rib cage, diaphragm, abnormal organs) during ventilation (approx 20% of R)
- 2. Airway resistance: impedance to ventilation by movement of gas through the airway
What are 2 factors that affect airways?
- 1. Laminar flow: gas moves in discrete layers layers or streamlines. Layers near the center of the airway move faster than those close to the wall of airway. Results from the friction between gas molecules and the wall (Poiseulle's Law)
- 2. Turbulent flow: gas flow through a tube changes significantly and gas molecules form irregular currents
What factors are needed for laminar to turbulent flow?
- 1. Gas density
- 2. Viscosity
- 3. Linear velocity
- 4. Tube radius
What is the flow of small airways?
What happens to the lung tissue during inspiration?
Widens transpulmonary pressure gradient and increase the diameter of the airways
What happens when you increase airway diameter and increase lung volume?
Decreases airway resistance
What compliance is less then normal?
What compliance is increased?
What are some symptoms of PTs with stiff lungs?
- Increase elastic WOB - pulmonary fibrosis
- Often have a rapid, shallow breathing pattern which minimizes the mechanical work of distending the lungs but at the expense of more energy to increase breathing rate
What is Raw and what is the equation?
Resistance airway and equation is P/F
What is the normal value of Raw or airway resistance?
What is Poiselles law?
- Decreased radius = increased pressure
- law that gives the pressure drop in a fluid flowing through a long cylindrical pipe.
- P = V / r4
Does it take any energy when we exhale or during expiration?
- Yes, its passive but potential energy is used.
- Potential energy: saved energy, from inflated lungs that want to go back to its original size
In the distribution of ventilation in disease, where does all the blood go through the lungs?
Gets pull down through the apices down to the bases and the periphary of the lungs causing, deadspace
What is the % of wasted deadspace volume?
Deadspace is calculated by?
- Modified bohr equation
- multiply by 1 if lbs
- multiply by 2 if kg
What is the normal value for minute ventilation?
What is the normal PaCO2 value?
During resting CO2, what is the normal value?
If CO2 goes UP because of slow breathing, its called?
Hint: VA decreases
If CO2 goes DOWN its called?
Hint: VA increases
Hyperventilation (blowing in a bag for CO2)
What happens to PaCO2 if you were to hold your breath?
Where are the DRG and VRG located?
What's in the Pons?
- Apneustic center
- Pneumotaxic center
What controls It? (Inspiration time)
What is the Hering-Breuer Reflex?
stretch receptors send signals to DRG and vasovagal nerve, stopping further inspiration
What chemoreceptors are found in arch of aorta and carotid sinus?
Which chemoreceptors are found in the medulla?
When the PaCO2 level is below 60mmHg which receptors are more sensitive or triggered?
Should COPD PTS or O2 induced hypercapnia PTs ever be denied O2?
- No, they should never be denied, but never give them 100% O2. Just give them enough, 60-80%
- Watch pulse oxymetry
What are Cheyne-stokes patterns?
RR and Vt gradually increase and then gradually decrease to complete apnea
Biot's patterns are seen in PTs with?
Occurs in PTs with ICP (intercranial pressure)
What are Biot's patterns?
Similar to cheyne-stokes except Vt are of identical depth.
Anytime there is damage to the pons it will be in the?
Apneuistic pattern - Long gasping breathing pattern
Which kind of PTs get cheyne-stokes patterns?
CHF and brain injury PTS
In CO2 and cerebral blood flow, or closed brain injury what can happen?
- Increased CO2
- Cerebral Vessel dilation
- Increased ICP
Air in the lungs that you dont exhale out is called?
What is the TLC made up of?
IRV + VT+ ERV + RV
What is the Vital Capacity or VC made up of?
TLC - RV
What is the sum of IRV + VT?
What is the sum of ERV + RV?
Functional Residual Capacity