Ventilation

Question 1

External Ventilation

Answer 1

Exchange of gases between atmosphere & pulmonary loop of circulation

Question 2

Internal Ventilation

Answer 2

Exchange of gases between blood and tissues and O2 utilization

Question 3

Fx of Respiration

Answer 3

1. ventilation 2. diffusion of O2 and CO2 b/t alveoli and blood 3. Transport of O2 and CO2 via blood to tissues 4. regulation of ventilation

Question 4

2 ways of lung expansion & contraction

Answer 4

1. up (contraction) and down (expansion) movement of diaphragm to shorten and lengthen the chest cavity 2. elevating and depressing the ribs to incr. or decr. the anteroposterior diameter

Question 5

normal breathing - inspiration

Answer 5

1. contraction of diaphragm –> pleural cavity expands –> intrathoracic volume increases 2. intrapleural pressure drops –> lungs expand to fill the empty space –> 3. lung pressure drops below atmospheric pressure and draws in air from the outside –> occurs until atmospheric and intraplumonic pressure are equal

Question 6

normal breathing - expiration

Answer 6

1. diaphragm relaxes –> thoracic cavity contracts 2. intrapleural and intrapulmonic pressure rises > than atmospheric pressure –> forces air out of the lungs 3. elastic recoil of lungs chest walls and diaphragm also help to expel air

Question 7

Heavy breathing - expiration

Answer 7

additonal forces required, elastic recoil isn’t enough contraction of abdominal muscles –> pushes abdominal contents upward into diaphragm –> compresses lungs

Question 8

muscles of inspiration

Answer 8

1. external intercostal 2. sternocleidomastoid (lift sternum up) 3. Anterior Serrati (lift ribs) 4. Scaleni (lift first 2 ribs)

Question 9

muscles of expiration

Answer 9

1. abdominal recti (pull lower ribs downward) 2. internal intercostals

Question 10

inflow of air vs. outflow of air

Answer 10

alveolar pressure has to be lower than atmospheric pressure (falls to -1 cm of h2o –> negative pressure pulls in 0.5 L of air alveolar pressure greater than atmospheric (rises to +1 cm of h2o) –> forces out 0.5 L of air

Question 11

Transpulmonary pressure

Answer 11

difference between pressure in alveoli and pressure on the outer surfaces of lungs; measures the recoil pressure (elastic forces that cause collapse of lungs at each instant of respiration)

Question 12

lung compliance

Answer 12

transpulumonary pressure increases by 1 cm of h2o –> lung volume will expand 200 mL (after 10-20 sec; enough time to reach equilibrium) total compliance of both lungs (normal) = 200 mL of air/cm of h2o transpulmonary pressure

Question 13

compliance characteristics of lungs determined by elastic forces

Answer 13

Elastic forces of lungs 1. elastic forces of lung tissue –> given by elastin and collagen 2. elastic forces caused by surface tension of fluid in the walls of alveoli

Question 14

total lung elasticity (breakdown)

Answer 14

1/3 - tissue elasticity –> causing collapse of lungs 2/3 - surface tension in alevoli

Question 15

intrapleural pressure

Answer 15

always subatmospheric under normal conditions varying between 25 and 27.5 cm H2O during quiet breathing. AKA pleural pressure

Question 16

Functional Residual Capacity (FRC)

Answer 16

the pressure immediately before inspiration, which is normally about -5 cm H2O; occurs when all of the respiratory muscles are relaxed.

Question 17

surfactant

Answer 17

when present reduces surface tension secretion starts between 24-35 weeks in utero increases lung compliance (decreasing amt of work required to inflate the lungs during inspiration) synthesized from type II alveolar cells composed of DPPC

Question 18

neonatal respiratory distress syndrome

Answer 18

surfactant is lacking in the fetus the more premature the infant, the less likely surfactant will be present –> if born b/f 24 weeks absolutely will never have surfactant no surfactant –> increase surface tension –> causing alveoli to collapse (ATELECTASIS)–> no ventilation to alveoli –> won’t have gas exchange (PULM SHUNT) –> hypoxemia develops

Question 19

Law of Lapace

Answer 19

P = 2T/ r P - collapsing pressure on alveolus or pressure required to keep alveolus open (dynes/cm2) T - surface tension (dynes/cm) r - radius of alveolus (cm) large alveolus –> low collapsing pressure 1/2 normal radius –> 2 x the collapsing pressure

Question 20

Dipalmitoyl Phosphatidylcholine (DPPC)

Answer 20

amphipathic phospholipid that reduces surface tension; found in surfactant hydrophobic portions –> attracted to each other, hydrophilic portions –> repelled intermolecular forces break up attracting forces of liquid molecules lining the alveoli

Question 21

compliance of thorax and lung together

Answer 21

combined the compliance is 1/2 the compliance of the lungs alone (110 mL/cm of h2o pressure vs. 200 ml/cm of h2o) in extreme high or low volumes –> combined compliance can be 1/5 of the lung-alone compliance

Question 22

Respiratory Volumes and Capacities

Answer 22