8. Pulmonary Lung Vol Flashcards
What is diff b/w vol + capacities?
Vol = directly measured; capacities = inferred from lung vol
What is normal TV?
6-8ml/kg
What is normal vital capacity (VC)?
60ml/kg +/- 20% (~10x TV)
What is normal RR?
12-20bpm for adults
30-60bpm at birth
To cough effectively VC has to be how much greater than TV?
VC > 3 x TV
What is TV?
Normal volume of air breathed in during baseline state
What is expiratory reserve vol (ERV)?
Add. vol of air forcefully expired past norm. expiration
What is residual volume (RV)?
Vol remaining after max. expiration –> vol to keep alveoli open, RV=FRC-ERV
What is inspiratory reserve volume (IRV)?
Add. vol of air that can be forcefully inhaled past norm. inspiration
What is vital capacity (VC)?
Max vol of air that can be forcibly expired after max inspiration
VC=TV+IRV+ERV
What is inspiratory capacity?
If at end of tidal vol expiration, vol of max inspiration
What is total lung capacity (TLC)?
Vol air at end of max. inspiration
TLC=FRC+TV+IRV=VC+RV
What is functional residual capacity (FRC)?
Vol air remaining after norm. passive exhalation
FRC=RV+ERV
What is minute ventilation?
Vol air exhaled per min
What is normal TV?
500ml
What is normal IRV?
3000ml
What is normal ERV?
1100ml
What is normal RV?
1200ml
What is normal FRC?
2300ml
What is normal TLC?
5800ml
How does pt positioning affect alveolar size?
Size of alveoli diff at top than bottom (upright) –> weight of lungs compressing alveoli at base. W less weight pushing against upper alveoli, expanded out more (alveolar interdependence). Top alveoli has decr. compliance b/c closer to TLC –> lesser ventilation.
(T/F) Gravity doesn’t affect perfusion.
False, greater perfusion near base of lungs. HOWEVER, perfusion and ventilation have diff slopes resulting in V/Q mismatches at both extremes of apex + base.
Describe a flow-volume loop.
Full expiration near 0 on Lhand side TLC/total inhalation on Rhand Lower curve inhalation Upper curve exhalation BUT typically move only small range w/in flow-vol loop (from FRC to TLC), typically w/ most compliance
What happens to elasticity + compliance in a sick lung?
Lower compliance (easier to distend) + elasticity (ability of lungs to recoil) worsens –> greater V/Q mismatches, alveoli are hyperextended
What is FVC/FEV1
Forced VC is when pt asked to take biggest breath as can + as quick + hard as can blow out –> vol measured. Forced expiratory volume at 1s measured over 1s (norm=~4L)
What is Max. Voluntary Vent (MVV)?
MVV (aka Maximal breathing capacity) is max vol air that can be exhaled by voluntary effort in 15s interval, then multiplied by 4 –> L/min
What is closing capacity?
Vol in lungs at which airway + alveoli start to collapse. Want to stay above this or else cause atelectasis.
FRC + alveolar interdependence helps compete against this. CC typically well below FRC. HOWEVER, CC sig. increases with age while FRC barely if any. FURTHERMORE, FRC decr. based on position + esp. w anes., smoking history, and lung disease –> encourage coughing + deep breathing after GA.
What happens as alveoli remain collapsed for longer + longer periods of time?
More V/Q mismatch, gas exchange prob, hypoxemia + other post-op pulm. complications
(T/F) In young, healthy pt, a few coughs + deep breaths is not sufficient to re-expand alveoli.
False
What variables affect FRC?
- Sex
- Body habitus (obesity adds extra weight –> blunts outward recoil of chest wall –> decrease FRC)
- Posture/positioning
- Age
- Lung disease
- Diaphragmatic tone
Where is the dependent part of lung?
Lower portion of lung
What happens when you lose diaphragmatic tone?
(almost imm w induction of anes even before MR) abd contents push up on lungs –> compress to smaller size –> sig. drop FRC
What % of all pt have atelectasis under GA as result of loss of diaphragmatic tone
85-95%
When pt transitions from upright to supine position, how much does FRC drop?
0.5-1L
What is the relationship between FRC + age
FRC decreases w increasing age
How does induction of anesthesia affect muscle tone?
GA causes diaphragm + chest wall muscle tone to decrease
By what % does FRC decrease w GA?
10-20% drop
How long does it take for FRC to return back to normal after GA?
Hours
(T/F) Elderly pt can’t generate enough P to overcome atelectasis after GA.
True
What are different types of ventilation that you can use on pts + how do they affect atelectasis?
Standard TV ventilation (10-20cmH2O) - ineffective
Sigh breaths (20cmH2O) - ineffective
40cmH2O - typically effective
How does size + number change as progress down pulm. airway?
The size of airways decrease but number increases sig –> sig. increase in sum cross-sectional airway (many terminal bronchioles vs. trachea)
Describe the tracheobronchial tree and how it affects ventilation.
Terminal bronchi have smooth muscle surrounding them –> contract + dilate. However, are very small –> greater resistance in bronchus than in trachea
Which flow system has lowest resistance to flow?
Laminar flow as opposed to turbulent flow
Which type of airway has the greatest resistance to flow?
Small airways, esp. those lined w secretions –> increased work of breathing. Larger airways = easier to maintain laminar flow
What is Poiseuille’s Law?
Resistance is inversely related to r^4 –> small increase in radius decreases resistance sig!
How does lung volume affect airway resistance?
As lung vol increase, resistance decreases sig (exponential drop). Alveolar expansion helps extend term. bronchioles
How does airway resistance change as pt changes from upright to supine position?
Resistance increases, R in upright pt is close to its lowest
Where is the greatest resistance found in pulm. airway + why?
Greatest R in bronchi because of smaller size compared to trachea. However, R decreases sig. as branch from bronchus to bronchioles to term. bronchioles –> sig. increase in total surface area (make up sig. portion of airflow)
How does secretions or bronchospasm affect airway resistance?
Change in diameter –> sig increase in R –> increased work of breathing
What is alveolar interdependence?
Tethering of alveoli to each other –> helps stent open alveoli + airway –> drops R. HOWEVER, tethering decreases w disease + destruction of alveoli
