Flashcards in Pulmonary Mechanics 1 Deck (38):
What is eupnea?
Normal quiet breathing (7.5 L/min). Inspiration is active but expiration is passive.
Which muscles are used during eupnea?
The diaphragm may be the only active inspiratory muscle. Expiration is due to the passive recoil of the lung and the chest wall without the participation of expiratory muscles.
In terms of active and passive describe inspiration and expiration in a eupneic patient:
Inspiration is active while expiration is passive.
What is hyperpnea?
Active breathing like during exercise. Deeper and faster than normal (120 L/min max).
What muscles are used during inspiration in a hyperpnic patient?
Inspiration is aided by the contraction of the external intercostals which lift the ribs upwards and outward to expand the chest cavity to accommodate the larger volumes of air.
What are the accessory muscles of inspiration and what do they function to achieve?
Sternocleidomastoid - lifts
sternum scalene - lifts upper ribs
Facial neck and head also have some function.
They are all used to reduce the resistance to airflow.
What muscles are used during expiration in a hyperpnic patient?
The internal intercostals and all four of the abdominal muscles are used.
For active inspiration what intercostal muscles are used?
The external intercostals
For active expiration what intercostal muscles are used?
What is tachypnea?
More rapid breathing than normal
What is hypoventilation? What does it lead to?
It is inadequate ventilation due to breathing too slowly. Leads to alveolar hypoxia, hypercapnea (elevated CO2 levels), and respiratory academia.
What is hyperventilation? What does it lead to?
Breathing faster than required for oxygenation leads to alveolar hypocapnea (low CO2) and reparatory alkalemia.
Alveolar pressure is one of three pressures that drive breathing, what is it? What happens to it during the breathing cycle.
It is the pressure inside of the alveolar sacs and that pressure varies during the breathing cycle. During inspiration Palv < Patm. During expiration Palv > Patm
Intrapleural pressure is one of three pressure that drive breathing, what is it? How does it change during the breathing cycle?
It is the pressure in the space outside the lung but within the chest wall. Contraction of the diaphragm exerts an expansive force on the intrapleural space, thus decreasing its pressure, making it more negative, and acting to inflate the lung.
External pressure is one of three pressure that drive breathing, what is it? How does it change during the breathing cycle?
It is usually the atmospheric pressure which is constant during the reparatory cycle, however, if a weight is placed on the chest then the external pressure on the chest wall is greater than Patm and is referred to as body surface pressure.
What is transmural pressure? What is an outwardly directed transmural pressure, what about inward? (positive or negative)
Pressure across and elastic vessel is defined as internal minus external pressure. Outwardly directed transmural pressures are regarded as positive while inwardly directed transmural pressures are negative.
What is the formula for Transmural chest wall pressure Pc?
Pc = Ppl - Patm. Sets degree of inflation of chest wall.
What is transmural lung pressure Pl?
It is the transmural pressure across the lung and is the difference between alveolar and intrapleural pressures. Sets degree of inflation of lung. It must always be positive to maintain inflation
What is the formula for Transmural lung pressure Pl?
Pl = Palv- Ppl.
What is chest wall pressure?
Is the transmural pressure across the chest wall and is the difference in pressure between the intrapleural space and atmospheric or body surface pressure. Pc is negative at rest.
What is the total transmural pressure Pt?
Also called the relaxation pressure. It is the total transmural pressure across the lung and the chest wall. The total pressure is the difference between alveolar and atmospheric pressure and is equal to the sum of the lung pressure and the chest wall pressure.
What is the formula for total transmural pressure Pt?
Pt = Palv - Patm = Pc + Pl
At rest what is the positive outward lung pressure balanced by?
The inward passive elastic recoil pressure of the lung.
What balances the negative inward chest wall pressure?
It is balanced by the passive outward elastic recoil pressure of the chest wall.
If the intrapleural space is exposed to atmospheric pressure what will happen?
The lung will collapse inward while the chest wall will spring outward.
What would the compliance of one lung be comported to the compliance reported for both lungs?
It would be 1/2. Don't forget this. This is due to half the volume being in each lung.
The lung and the chest wall are compliant in series, what does this mean?
You can add their pressures together.
What is the formula for total compliance?
Ct = ∆V/ ∆Pt = ∆V/ ∆Palv
What is the formula for lung compliance?
Cl = ∆V / ∆Pl. ∆Pl = Pl final - Pl initial
What is the formula for chest wall compliance?
Cc= ∆V/ ∆Pc. ∆Pc = Ppl - Patm
When thinking about the lung and the chest wall they can both be thought of as springs, describe each.
The lung is a one way spring which is always trying to move in. The chest is a two way spring.
What happens to lung compliance in fibrosis?
It is decreased making it difficult to inspire
What happens to lung compliance in emphysema?
It is increased making it difficult to exhale
Increasing lung compliance will do what to FRC and TLC? Decreasing Cl will do what?
Increase will increase both while decrease will decrease both.
What does surfactant function to do? What effect does it have on compliance?
It lowers the surface tension of the lung and increases compliance.
What would happen if someone had a deficiency in surfactant?
It increases the surface tension of alveoli and thus increases their elastic recoil and tends to deflate the lung.
Which bubble has higher pressure if they both have the same surface tension, a small bubble or a larger bubble?
The smaller bubble. Air would flow from the small to the bigger one. This is from Laplace's law P = 2T/r . This is what happens without surfactant.