Resistance To Airflow

Question 1

Resistance

Answer 1

Anatomical 90% (esp nasal)
Resistance in airway dec toward alveoli, greatest at mid sized bronchi
Tissue 10%

R = P/Q

Question 2

Flow

Answer 2

Laminar: if radius halved, resistance increases 16 fold
Lower resp airways
Turbulent: pressure proportional to square of flow rate
Higher Reynolds number more turbulence
Upper resp airway

Question 3

Transitional flow

Answer 3

Mix

Lower resp tract

Question 4

Factors determine airway resistance

Answer 4

ANS
SNS: bronchodilation, dec resistance, beta 2
PNS: bronchoconstriction, inc resistance, Ach
Racial traction: inc alveolar size, dec resistance and vise versa
Inc air viscosity, inc resistance

Question 5

Forced expiration to RV, intraplueral pressure

Answer 5

Exceeds airway pressure and causes compression and limits airflow out of lungs

Question 6

Flow Volume loops

Answer 6

Obstructive: higher vol, low PEFR, high RV, dec elastic recoil, bowing inward, dec FEV1/FVC

Restrictive: lower vol, lower PEFR, bowing outward, slight increase FEV1/FVC

Question 7

Fixed obstruction

Answer 7

Blunts both insp and exp loops

Not affected by transmural pressures

Question 8

Variable extrathoracic obstruction

Answer 8

Blunted insp loop
Affected by transmural pressure
Tumors, fat deposits, weak pharyngeal muscles, paralyzed vocal cords, enlarged lymph nodes

Question 9

Variable intrathoracic obstruction

Answer 9

Blunted expiratory curve
Affected by transmural pressure
Tumors of trachea within thoracic cavity

Question 10

Work of breathing

Answer 10

1. Work of compliance
   W = VxP/2
2. Work of airway resistance

No work of compliance in expiration
Obstructive have to do work to expire