respiratory: intro

Question 1

equation for resistance

equation for flow

Answer 1

R=8VL/pi r^4
F= change in pressure/resistance
=(p1-p2) pi r^4/8VL

Question 2

how are lungs prevented from collapsing

Answer 2

outward recoil of chest wall opposes inward recoil of lungs

Question 3

what happens in inspiration

Answer 3

thoracic cage expands-> intrapleural pressure drops to become -ve -> lungs expand -> alveolar pressure drops-> air flows into lungs

Question 4

is expiration and inspiration active/passive

Answer 4

inspiration is active

expiration is passive AT REST

Question 5

Inspiratory muscles

Answer 5

diaphragm 
external intercostal muscles 
parasternal internal intercostal muscles (1-5 intercostal spaces) 
scalenes 
accessory muscle: sternocleidomastoid

Question 6

expiratory muscles

Answer 6

internal intercostal
rectus abd 
ext oblique
int oblique
transversus abdominis

Question 7

equations and values of 
vital capacity
inspiratory reserve vol 
tidal vol 
expiratory reserve vol 
residual vol
inspiratory capacity
TLC
FRC

Answer 7

vital cap: vol from biggest breath in to biggest breath out 5.5L
inspiratory reserve vol: extra breath in biggest breath in 3.3L
expiratory reserve vol: extra breath out in biggest breath out 1.7L
tidal vol: normal breathing 0.5L
residual vol: vol left after biggest breath out 1.8L
inspiratory capacity: vol from bottom of tidal vol to max 3.8L
TLC: 7.3L
FRC: RV + ERV

Question 8

transpulmonary (pl), transtotal (prs) and transwall (pw) equation

Answer 8

transpulmonary= alveolar pressure- intrapleural pressure
transtotal= alveolar pressure - atm pressure
transchest= intrapleural pressure- atm pressure

Question 9

when pl is high what does it imply

Answer 9

harder to inspire

Question 10

what happens in pneumothorax

Answer 10

air sucked into pleural space until intrapleural pressure=atm pressure -> lung collapses due to inward elastic recoil; chest wall expands to resting state due to outward directed elastic recoil

Question 11

what’s dead space
typical volume in healthy individual
two types of dead space

Answer 11

airway volume with no gas exchange
150ml
anatomic : all except alveoli +bronchioles
physiologic: anatomic + areas with dysfunctional gas exchange

Question 12

how to derive alveolar ventilation

Answer 12

minute ventilation- dead space ventilation

minute ventilation: total ventilation in ml per min

Question 13

two types of resistance to airflow

Answer 13

elastic: resistance of stretch of lung tissue + air-liquid interface
airway: friction between layers of flowing air + air and airway walls

Question 14

how is elastic resistance measured? equation

Answer 14

compliance

change in lung vol/change in transmural pressure

Question 15

how is airway resistance measured? equation

Answer 15

(alveolar pressure-mouth pressure)/airflow at mouth

Question 16

what causes increased airway resistance?
2 examples
what causes wheezing?

Answer 16

high velocity/sharp edges/branch points cause laminar flow-> turbulent flow-> increases resistance-> vibrations
bronchial smooth muscle tone/hypertrophy of glands-> mucous secretion/inflammation
in forced expiration-> intrapleural pressure becomes +ve-> transpulmonary pressure is -ve -> collapsing force on airways
oscillations in airways near point of closure

Question 17

main sites of airway resistance

which airways contribute the most to airway resistance

Answer 17

nose/pharynx/larynx
medium sized bronchi (smaller distal airways have high individual resistance but they are in// to net resistance is low)
generation 3-5

Question 18

where does generation 0 start

Answer 18

trachea

Question 19

what causes bronchodilation

Answer 19

SNS: b2
inhibitory NANC
co2

Question 20

what causes bronchoconstriction

Answer 20

WBC-> histamines/prostaglandins
Pulmonary stretch receptors inhibit brainstem-> CNX prevent over inflation of lung
airway irritant receptors-> activate brainstem-> CNX
NANC excitatory