00AA - To Review for finals!

Question 1

Alveolar gas equation

Answer 1

PAO2 = [(760 - 47) X FIO2] - PaCO2/0.8

Question 2

A-a gradient equation and ref range

Answer 2

Aa∆ = PAO2 - PaO2
= ([(760 - 47) X FIO2] - PaCO2/0.8) - PaO2

Reference range: 10-20mmHg (<10mmHg expected in healthy, young pts)

Question 3

Oxygen Content Equation

Answer 3

oxygen content = bound O2 + dissolved O2

= (1.34 •Hgb • SaO2) + (0.003 • PO2)

Question 4

Define and give 5 general causes of restriction.

Answer 4

Restriction is a reduction in the total volume to which the lungs can be inflated, i.e. a reduction in total lung capacity.

Causes include:

1. neuromuscular disease (e.g. MG)
2. chest wall disorders(e.g. kyphoscoliosis)
3. pleural disease (e.g. thickening s/p infection),
4. acute or chronic loss of aerated lung tissue (e.g. pneumonectomy, bacterial pneumonia)
5. interstitial lung disease (e.g.sarcoidosis, idiopathic pulmonary fibrosis).

Remember that restriction is a pattern of
abnormality, not a specific diagnosis or disorder.

Question 5

Draw a flow-volume curve for:

1. normal
2. obstructive
3. restrictive
4. fixed upper airway obstruction

Answer 5

see practice test answer

Question 6

Light Criteria

Answer 6

Pleural fluid protein/serumprotein ratio > 0.5
Pleural fluid LDH/serum LDH ratio > 0.6
Pleural fluid LDH> 2/3 upper limit of normal

Question 7

What does plateau pressure represent?

What does peak pressure represent?

Answer 7

.

Question 8

Neuromuscular vs. ILD Restrictive Findings:

Answer 8

ILD Neuromusc

FEV1: Decreased | Decreased

FVC: Decreased | Decreased

FEV1/FVC:
Often incr. (b/o incr elastic recoil) | Normal

TLC: Decreased | Decreased

FRC: Decreased
(due to incr elastic recoil) | Normal

RV:
Decreased (b/o incr lung elastic recoil) |
Often increased

DLCO: Decreased (often very low) | Decreased

PCO2:
Usually low or normal; may be
increased in very advanced disease |
Normal until advanced disease when PCO2 may rise

PO2:
Usually decreased | Normal until hypoventilation ensues

(A‐a): difference Increased | Normal

PO2 with exercise:
Further decrease | Generally unaffected

Question 9

Hypoxia vs. Hypoxemia vs. ischemia

Answer 9

hypoxia is decr O2 delivery to tissues

hypoxemia is decrt PaO2

ischemia is decr blood flow to tissues