Mechanics of breathing

Question 1

What are the accessory muscles for deep inhalation?

Answer 1

Sternocleidomastoid
Scalenes
Pectoralis minor

Question 2

What are the muscles used during deep exhalation?

Answer 2

Abdominal muscles
Internal intercostals

Question 3

What is Boyle’s law?

Answer 3

Pressure exerted by a gas in a closed container is inversely proportional to the volume of the container at a constant temperature

Question 4

What is the normal range of the intrapleural pressure?

Answer 4

-3 to -5 cm of H20

Question 5

What is transpulmonary pressure?

Answer 5

The difference between alveolar pressure and intrapleural pressure

Pt = Pa - Pi

Question 6

What are the pressure changes during no breathing?

Answer 6

Intrapulmonary pressure is equal to atm
Intrapleural pressure is less than atm

Question 7

What are the pressure changes during normal inhalation?

Answer 7

Intrapulmonary pressure decreases to -1
Intrapleural pressure drops to -6

Question 8

What are the pressure changes during normal expiration?

Answer 8

Intrapulmonary pressure increases to +1
Intrapleural pressure increases to -4

Question 9

What is the typical tidal volume?

Answer 9

~ 500 mL

Question 10

What happens to transmural pressure during inspiration?

Answer 10

Difference increases, becoming more positive

Question 11

What is positive pressure breathing?

Answer 11

Air can be forced into the lung by raising the pressure at the nose

Question 12

What are the two methods for air to move into the lung?

Answer 12

Negative pressure breathing
Positive pressure breathing

Question 13

What are indications for mechanical ventilation?

Answer 13

Poor oxygenation
Raised CO2 level
Increased work of breathing

Question 14

What is the purpose of PEEP and what does it stand for?

Answer 14

Prevent alveolar collapse at the end of expiration

Positive end-expiratory pressure

Question 15

What are factors contributing to the mechanics of respiration?

Answer 15

Lung compliance
Surface tension of alveolar fluid - surfactant
Airway resistance

Question 16

What is the equation for compliance?

Answer 16

C = deltaV/deltaP

Question 17

What is the normal compliance of both the isolated lungs?

Answer 17

200 mL of air/cm of H2O

Question 18

What is represented by the slop of a pressure volume curve?

Answer 18

Compliance

Question 19

What is the reciprocal of compliance?

Answer 19

Elastance

Question 20

What are the two components of lung recoil?

Answer 20

Collagen and elastic fibers of the tissue
Surface tension forces

Question 21

What factors cause the stability of the alveoli?

Answer 21

Surfactant
Alveolar interdependence

Question 22

What can be assessed by the L/S ratio in amniotic fluid?

Answer 22

Fetal lung maturity

Question 23

At what L/S ratio is the lung mature?

Answer 23

> 2

Question 24

What is the forced vital capacity?

Answer 24

Maximal volume attained on forced expiration beginning at TLC

Question 25

What is the FEV1?

Answer 25

Forced expiratory volume in the first second

Question 26

What is the FRC?

Answer 26

Functional residual capacity Amount of air left in lungs after normal expiration

Question 27

What is the ERV?

Answer 27

Expiratory reserve volume Amount that remains in lungs above the RV after quiet expiration ERV = FRC - RV

Question 28

What is the IRV?

Answer 28

Inspiratory reserve volume Amount of air that can be inspired above the tidal volume

Question 29

What is the IC?

Answer 29

Inspiratory capacity or inspiratory vital capacity Maximal volume of air inhaled above FRC

Question 30

What is DLCO?

Answer 30

Diffusion capacity of CO Measures the uptake of CO as surrogate for capillary beds

Question 31

What is the pressure relationship at FRC?

Answer 31

Balance between inward elastic recoil of lung and outward elastic recoil of chest wall

Question 32

What is the pressure relationship above FRC?

Answer 32

Overall pressure is positive

Question 33

What is the pressure relationship below FRC?

Answer 33

Overall pressure is negative

Question 34

What makes up non-elastic resistance?

Answer 34

Pulmonary tissue resistance Airway resistance due to friction between gas molecules and airway walls

Question 35

What is the major site of airway resistance?

Answer 35

Medium-sized bronchi

Question 36

What is the general equation for airflow?

Answer 36

Flow(Q) = deltaP/R

Question 37

What is the equation for resistance using Poiseuille's law?

Answer 37

R = (8 x eta x l)/(pi x r^4)

Question 38

What is the equation for airflow using Poiseuille's law?

Answer 38

Flow = (deltaP x r^4 x pi)/(8 x eta x l)

Question 39

What is the equation for Reynold's number?

Answer 39

Rn = (rho x Ve x D)/eta rho = density eta = viscosity

Question 40

At what value does airflow change from laminar to turbulent?

Answer 40

Rn > 2000

Question 41

What is the effect of SyNS stimulation on bronchial smooth muscle?

Answer 41

Bronchodilation

Question 42

What is the effect of PsNS stimulation on bronchial smooth muscle?

Answer 42

Bronchoconstriction

Question 43

What factors affect airway resistance?

Answer 43

Lung volume Bronchial smooth muscle tone Density and viscosity of inspired gas Chemicals and other irritants

Question 44

What happens to the equal pressure point during expiration and why?

Answer 44

It moves deeper into the lung as expiration progresses because of increased resistance

Question 45

What is the pressure gradient for airflow during normal expiration?

Answer 45

Difference between alveolar pressure and atmospheric pressure

Question 46

What is the pressure gradient for airflow during forced expiration?

Answer 46

Between alveolar pressure and intrapleural pressure

Question 47

Why does alveolar elastic recoil pressure oppose dynamic compression?

Answer 47

Radial traction

Question 48

What is the equation for work?

Answer 48

W = Pt x deltaV

Question 49

What is airway resistance work?

Answer 49

Work required to overcome the resistance to airflow through the respiratory passage

Question 50

What is tissue resistance work?

Answer 50

Work required to overcome the resistance of the lungs and chest wall structures to change in shape because of molecular cohesion

Question 51

Why do patients with emphysema breath with pursed lips?

Answer 51

Moves site of main airway resistance closer to the mouth, keeping airways patent by extending time airway pressure remains high