Pulmonary Mechanics I Flashcards
1
Q
negative pressure pump
A
- lung inflates due to a drop in intrapleural pressure outside the lung but inside the chest wall
- diaphragm drops, volume increases, pressure decreases, lung inflates
- respirator inflates using positive pressure and lung deflates due to recoil
- when diaphragm stops contracting, passive elastic recoil deflates lungs
- when relaxed, pressure is less than atmosphere by 5 cm water
- pulmonary pressures given relative to atm pressure, less than atm is negative
- intrapleural is -5
- in absolute terms intralpleural is actually positive because Patm=760/1034 cm h20, then pleural is 1029 cm h20
- when wounded, intrapleural pressure rises to atm and lung collapses
2
Q
inspiration muscles
A
- accessory- SCM, stermun scalene, facial, neck, head
- external intercostals-lifts ribs up and forward and increases post/ant dimension of chest cavity, adds tone
- diaphragm is primary muscle of inspiration
3
Q
muscles of expiration
A
- internal intercostals- lower ribs
- abdominal-depresses lower ribs, compresses abd cavity, pushes diaphragm up
- rectus abdominus, external/internal oblique, transversus abdominus
4
Q
eupnea
A
- quiet breathing
- diaphragm may be only muscle working
- enlarges thoracic cavity by moving downward
- expiration due to passive recoil of lung and the chest wall
5
Q
hypernea
A
- active breathing during exercise
- inspiration is aided by the contraction of external intercostals
- deeper and faster than normal
- tidal volume and freq increase
- inspiration uses external intercostals
- expiration uses internal intercostals
6
Q
strenuous exercise
A
- muscles of the chest and neck are used to reduce the resistance to air flow
- expiration aided by internal intercostals over 40L/min
- inspiration and expiration are active
7
Q
tachypnea
A
-more rapid than normal but not deeper
8
Q
hypoventilation
A
- muscular dystrophy, respiratory muscle paralysis
- leads to alveolar hypoxia and hypercapnea respiratory acidemia (high CO2, high H+, low pH)
- can’t breathe
9
Q
hyperventilation
A
- anxiety, panic attack
- breathing faster than required for oxygenation
- alveolar hypocapnea (low CO2, low H+, high pH)
- respiratory alkalosis
10
Q
pulmonary pressures
A
- alveolar compartment
- intrapleural space
- external space
11
Q
alveolar pressure
A
- varies during breathing cycle
- air movement requires pressure gradient
- during inspiration, Palv Patm
- if breath held with out and glottis open, pressure are equal
12
Q
intrapleural pressure
A
- Ppl
- space outside the lung but within the chest wall
- fluid filled and only 10 microns thick
- lung in close apposition to inner chest wall, movements of both elastic vessels lubricated by the fluid in the intrapleural space
- estimated by swallowing esophageal balloon so tip is in intrathoracic esophagus
- esophagus thin walled with little tone and transmits intrathoracic pressure changes
- upper end of balloon exposed to atm if mouth open, lower end changes in Ppl
13
Q
external pressure
A
- atm
- constant during cycle
- if weight placed on chest, external pressure is greater than Patm and is called body surface pressure
14
Q
transmural pressures
A
- pressure across and elastic vessel
- internal P minus external P
- outwardly directed positive, inwardly directed negative
15
Q
lung pressure
A
- Pl
- transmural pressure across lung
- Palv-Ppl (alveolar-intrapleural)
- sets degree of lung infiltration and must be positive to maintain inflation
16
Q
chest wall pressure
A
- Pc
- across chest wall
- Ppl-Patm (intrapleural minus atm)
- negative at rest
17
Q
total pressure
A
- Pt
- relaxation pressure
- across lung and chest wall
- Palv-Patm=Plung+Pc
18
Q
muscles relaxed
A
- mechanical equilibrium
- Pt=0
- Plung=-Pc
- positive outward pressure balanced by inward passive elastic recoil of the lung
- negative inward chest wall pressure balanced by passive outward elastic recoil of the chest wall
- exposed to air- lung collapses and chest wall springs out
19
Q
static compliance
A
-determines what particular volume the lung and chest wall will assume for a given transmural pressure when elastic vessels at mechanical equilibrium
20
Q
spirometer
A
- attached through a breathing tube connected to pressure gauge
- patient inspires then holds breath with glottis open, then relaxes muscles against weighted spirometer
- must be relaxed because passive elastic recoil is measured
- weight maintains lung inflation while the muscles are relaxed
- Ct about 0.1L/cm H20 near resting position of lung
21
Q
total compliance
A
-Ct=deltaV/deltaPt
-also equals deltaV/deltaPalv because P is Palv-Patm, but Patm is zero so P is Palv
-transmural pressures are additive
-Pt=Pl+Pc
-delta Pt=deltaPl +deltaPc
elastance:
-deltlaP/deltaV=deltaPl/deltaV+deltaPc/deltaV
-1/Ct=1/Cl +1/Cc (Ct=Cl+Cc)
-compliance of 1 lung is 1/2 of both lungs
-to normalize, specific compliance is used=deltaV/VdeltaP
22
Q
lung compliance
A
- need to separate from total to find source of problem
- deltaV/deltaPl
- remember Pl= Palv-Ppl (alveolar- intrapleural)
23
Q
chest wall compliance
A
- Cc=deltaV/deltaPc
- Pc= Ppi-Patm (intrapleural minus atm)
24
Q
functional residual capacity
A
- lung volume when Pt equals 0
- end expiratory
- 36% of vital capacity
- Pc=-Pl
- when lung is expanded to mechanical resting position of chest wall when Pc=0, only elastic force of lung opposes inspiration
- at larger lung volume when Pc>0, elastic recoil of both the lungs and chest wall provide passive DF for expiration
25
Q
forced expiration
A
- volumes below FRC, expansive force of chest wall provides DF for return of lung to FRC
- compliance depends on degree of inflation and is measured at FRC
26
Q
intrapleural pressure
A
- positive when muscles relaxed and the weight is on spirometer
- larger degrees of inflation, becomes more positive (contrasts with negative Pl during breathing)
27
Q
lung compliance in disease
A
- increased in emphysema
- decreased in fibrosis
28
Q
emphysema
A
- smoke contains inhibitor of alpha1 antitrypsin (normally inhibits proteases) so proteases aren’t inhibited- cuts CT up
- destruction of alveolar septae, merging of adjacent alveoli and formation of large blebs with loss of SA
- loss of elastic recoil and increased compliance
- neutrophils accumulate in lung to remove inhaled smoke, release the proteases, which aren’t checked
29
Q
pneumoconioses
A
- induced by inhalation of dust asbestos, coal, silica, other toxic particles
- induce granulomas and fibrous tissues
- decrease compliance
- stiffer lung
- changes in compliance also change total lung capacity and functional residual capacity
30
Q
air filled vs saline filled
A
- surface tension reduces compliance in air filled lung
- fluid removes recoil pressure leaving only elastic fiber recoil
31
Q
surfactant
A
- contains insoluble lipoprotein with diapalmitoyl lecithin
- lowers surface tension and increases compliance
- deficiency in surfactant increases surface tension and increases elastic recoil and deflates lung
32
Q
respiratory distress syndrome
A
- hyaline membrane disease
- premies
- no surfactant
- can’t keep lungs inflated due to decreased compliance
- use continuous positive airway pressure
- permeable to plasma proteins-glassy hyaline appearance
33
Q
bubbles
A
- if two bubbles have same surface tension, smaller bubble has larger internal pressure
- without surfactant, smaller alveolus empties into larger
- with surfactant, pressures are equal, surface tension increases with radius, larger area dilutes surfactant (less surface tension equalizes pressure)
- less surfactant per unit area and increase surface tension and pressure
- p=2T/r
