Lecture 3 - impaired gas exchange and airflow limitation

Question 1

O2 travels via:

Answer 1

haemoglobin

plasma

Question 2

CO2 travels via

Answer 2

haemoglobin (carbaminohaemoglobin)
plasma (CO2 +H2O -> H2CO3 -> HCO3- + H+ )
reaction sped up by enzyme carbonic anhydrase in RBC

Question 3

Short term effects of impaired gas exchange

Answer 3

• metabolic demands not met.
• increased arterial CO2
• decreased arterial O2
• Increased WOB
• increased respiratory exchange ratio
• increased work of heart
• impaired tissue oxygenation
• multiorgan failure

Question 4

Long term effects of impaired gas exchange

Answer 4

• pulmonary HTN

- cor pulmonale

Question 5

Indicators of impaired gas exchange

Answer 5

pulse oximetry

ABGs

Question 6

Type 1 respiratory failure

Answer 6

low Pa O2 (<60mmHg), normal or low CO2

Question 7

Type 2 respiratory failure

Answer 7

low Pa O2 (<60mmHg), high CO2 (>55mmHg)

Question 8

ABGs - Pa O2 normal

Answer 8

> 80mmHg

Question 9

ABGs - pH normal

Answer 9

7.35-7.45

Question 10

ABGs - Pa CO2 normal

Answer 10

35 - 45mmHg

Question 11

ABGs - Pa HCO3- normal

Answer 11

22-26mmHg

Question 12

ABG limitations

Answer 12

• cannot be used as a screening test for early pulmonary disease
• cannot be used to give specific diagnosis
• does not reflect how much abnormality is affecting pt

Question 13

3 factors influencing airflow

Answer 13

1. resistance is reduced by increasing lung volumes
2. resistance is reduced by increasing the calibre of airways (inc LV, bronchodilator med)
3. resistance is increased by reducing calibre of airways (i.e. asthma, bronchitis etc)

Question 14

airflow limitation causes:

Answer 14

1. obstruction in airway
2. change inside airway wall
3. change outside airway wall

Question 15

Airflow limitation obstruction causes:

Answer 15

1. inside the lumen (excessive mucous)
2. in the airway walls (contraction, oedema or hypertrophy)
3. peribronchial region (lack of radial traction)
4. more localised (tracheal or bronchial obstruction)

Question 16

Airflow limitation Restriction causes:

Answer 16

1. Lung parenchyma (excessive radial traction due to fibrosis)
2. lung pleura (pleural effusion/thickening)
3. chest wall (ankylosing spondilitis, scoliosis)

Question 17

Airflow limitation subjective signs

Answer 17

wheeze
dry tight cough
breathlessness
chest tightness
reduced ADLs/ex tolerance
difficulty clearing secretions

Question 18

Airflow limitation objective signs

Answer 18

abnormal pattern of breathing - reduced chest expansion
increased WOB
PLB
hyperinflation
abnormal PFTs
Acc muscle use
indrawing of lower ribs
auscultation - exp wheeze, dec. BS T/O

Question 19

Spirometry sign of obstructive lung disease

Answer 19

<70% than predicted FEV1/FVC ratio

Question 20

Spirometry sign of restrictive lung disease

Answer 20

Preserved FEV1/FVC ratio but <80% predicted FVC

Question 21

Spirometry sign of asthma

Answer 21

post bronchodilator medication, 12% increase in FEV1 and 200ml increase in FVC