Pulmonary Physiology and Pulmonary Function Tests

Question 1

Four major factors that determine alveolar gas composition

Answer 1

1. Inspired gas composition
2. Mixed venous gas composition
3. Alveolar ventilation
4. Alveolar perfusion

Question 2

Most frequently used objective tool to assess teh mechanical characteristics of the lung

Answer 2

FVC

Question 3

Maximum volume expired after maximal inspiration

Answer 3

Vital capacity

Question 4

Volume in lungs after maximal inspiration

Answer 4

Total Lung Capacity

Question 5

Volume remaining in lungs after maximal exhalation

Answer 5

Residual volume

Question 6

Volume in lungs at end of normal exhalation

Answer 6

Functional residual capacity (FRC)

Question 7

Volume of spontaneous breath

Answer 7

Tidal volume (TV)

Question 8

Maximum volume inspired from resting end expiratory position to total lung capacity

Answer 8

Inspiratory capacity

Question 9

Volume expired from spontaneous end expiratory position

Answer 9

Expiratory reserve volume

Question 10

Volume that can still be inspired from a spontaneous end inspiratory position

Answer 10

Inspiratory reserve volume

Question 11

PFT technique most commonly used

Answer 11

Forced Expiratory Vital Capacity Maneuver

• Maximal inhalation followed by rapid and completed exhalation

Question 12

FVC may be decreased due to what

Answer 12

• Intrinsic lung disease
• Pleural disease
• Chest wall restriction
• Respiratory muscle dysfunction

Question 13

FEV1 decreased in what setting

Answer 13

Airway obstruction or restrictive disease

Question 14

Normal range (FEV1/FVC ratio)

Answer 14

75-85%

• Decreased with age
• Increased in children (90%)
  
  • Children have higher flow rates for their size

Question 15

Low FEV1 with normal FEV1/FVC ratio

Answer 15

Restrictive lung disease process

Question 16

Low FEV1 and decreased FEV1/FVC ratio

Answer 16

Obstructive lung disease process

Question 17

Test performed where patient is asked to breathe as hard and fast as possible for 10-15 seconds and result is extrapolated to 60 seconds and reported in L/min

Answer 17

Maximal Voluntary Ventilation (MVV)

• Low MVV occurs in both obstructive and restrictive lung disease
• Very nonspecific test
• Useful to estimate patient’s ability to undergo major pulmonary resection

Question 18

Estimates transfer of CO across alvelolar capillary membrane

Answer 18

DLCO

• Impacted by:
  
  • Area of alveolar capillary membrane
  • Thickness of capillary membrane
  • Driving pressure for each gas being transferred

Question 19

Positive response to bronchodilators during PFT testing

Answer 19

• 12% or 200 ml increase in FEV1 or FVC

Question 20

Important elements of Preoperative Pulmonary Assessment

Answer 20

• Preop PFTs
• ABG (room air)
  
  • resting hypercapnea (pCO2 > 50) high-risk for periop morbidity
• Predicted Postop PFTs
  
  • multiply preop value of test by fraction of functional segments that remain postoperatively
  • quantitative radiographic assessment: V/Q scan or CT
• Maximal Oxygen Consumption During Exercise (VO₂max)

Question 21

Best method to determine the risk of perioperative morbidity and complications following major lung resection

Answer 21

Maximal Oxygen Consumption During Exercise (VO₂max)

• Prohibitive for lung resection: < 10 ml/kg/min
• High-risk for lung resection: 10-15 ml/kg/min

Question 22

Prohibitive and High-Risk results for Predicted Postoperative PFT testing

Answer 22

• Prohibitive:
  
  • ppoFEV1 < 20%
  • ppoDLCO < 20%
• High-Risk
  
  • ppoFEV1 < 40%
  • pproDLCO < 40%

Question 23

Preopeative values considered high-risk or prohibitive for pulmonary resection

Answer 23

• ppoFEV₁ < 0.8L or < 40% predicted
• ppoDLCO < 40%
• FVC < 1.5 L or < 30% predicted
• FEV₁/FVC ratio < 50%
• resting pO₂ < 45 mmHg
• resting pCO₂ > 50 mmHg
• VO₂max < 10 ml/kg/min
• unable to climb 1 fight of stairs
• resting O₂ saturation < 90% or desaturation >4% during exercise