Pulmonary Physiology and Pulmonary Function Tests Flashcards
Four major factors that determine alveolar gas composition
- Inspired gas composition
- Mixed venous gas composition
- Alveolar ventilation
- Alveolar perfusion
Most frequently used objective tool to assess teh mechanical characteristics of the lung
FVC
Maximum volume expired after maximal inspiration
Vital capacity
Volume in lungs after maximal inspiration
Total Lung Capacity
Volume remaining in lungs after maximal exhalation
Residual volume
Volume in lungs at end of normal exhalation
Functional residual capacity (FRC)
Volume of spontaneous breath
Tidal volume (TV)
Maximum volume inspired from resting end expiratory position to total lung capacity
Inspiratory capacity
Volume expired from spontaneous end expiratory position
Expiratory reserve volume
Volume that can still be inspired from a spontaneous end inspiratory position
Inspiratory reserve volume
PFT technique most commonly used
Forced Expiratory Vital Capacity Maneuver
- Maximal inhalation followed by rapid and completed exhalation
FVC may be decreased due to what
- Intrinsic lung disease
- Pleural disease
- Chest wall restriction
- Respiratory muscle dysfunction
FEV1 decreased in what setting
Airway obstruction or restrictive disease
Normal range (FEV1/FVC ratio)
75-85%
- Decreased with age
- Increased in children (90%)
- Children have higher flow rates for their size
Low FEV1 with normal FEV1/FVC ratio
Restrictive lung disease process
Low FEV1 and decreased FEV1/FVC ratio
Obstructive lung disease process
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
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
Estimates transfer of CO across alvelolar capillary membrane
DLCO
- Impacted by:
- Area of alveolar capillary membrane
- Thickness of capillary membrane
- Driving pressure for each gas being transferred
Positive response to bronchodilators during PFT testing
- 12% or 200 ml increase in FEV1 or FVC
Important elements of Preoperative Pulmonary Assessment
- 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)
Best method to determine the risk of perioperative morbidity and complications following major lung resection
Maximal Oxygen Consumption During Exercise (VO2max)
- Prohibitive for lung resection: < 10 ml/kg/min
- High-risk for lung resection: 10-15 ml/kg/min
Prohibitive and High-Risk results for Predicted Postoperative PFT testing
- Prohibitive:
- ppoFEV1 < 20%
- ppoDLCO < 20%
- High-Risk
- ppoFEV1 < 40%
- pproDLCO < 40%
Preopeative values considered high-risk or prohibitive for pulmonary resection
- 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
