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Pulmonary Function Tests: Spirometry Lung Volumes Diffusion Capacity Maximal Voluntary Ventilation (MVV) Maximal Inspiratory Pressure (Pi max) Maximal Expiratory Pressure (Pe max) Arterial Blood Gas (ABG) Walking Oxymetry Bronchochallenge Tests
INDICATIONS:
Pulmonary Evaluation: Presence of impairment Type of Pulmonary dysfunction Quantification of impairment in known disease Monitor the progression of known disease Monitor the treatment response of known disease Preoperative Assessment: Estimate the risk for postoperative complications (operability) Tolerance for lung resection (resectability) Disability Evaluation
LUNG VOLUMES & CAPACITIES:
Tidal Volume (VT): The volume of air entering the nose or mouth per breath (500 ml).
Residual Volume (RV): The volume of air left in the lungs after a maximal forced expiration (1.5L).
Expiratory Reserve Volume (ERV): The volume of air that is expelled from the lung during a maximal forced expiration that starts at the end of normal tidal expiration (1.5L).
Inspiratory Reserve Volume (IRV): The volume of air that is inhaled into the lung during a maximal forced inspiration starting at the end of a normal tidal inspiration (2.5L).
Functional Residual Capacity (FRC): the volume of air remaining in the lungs at the end of a normal tidal expiration (3 L).
Inspiratory Capacity (IC): The volume of air that is inhaled into the lung during a maximal forced inspiration effort that begins at the end of a normal tidal expiration (VT+IRV=3L).
Vital Capacity (VC): The volume of air that is expelled from the lung during a maximal forced expiration effort starting after a maximal forced inspiration (4.5L).
Total Lung Capacity (TLC): The volume of air that is inhaled into the lung after a maximal inspiration effort (5-6 L).
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(Maher K. Tabba MD, MS)
Spirometry: Measures the lung volume change during forced breathing maneuvers: Forced vital capacity (FVC) Forced expiratory volume in the first second (FEV-1)
Spirometry Obstruction Restriction FEV-1 Decreased (--) Decreased (-) FVC Decreased (-) Decreased (-) FEV-1/FVC Decreased (definition) Normal & Increased
Obstructive Lung Diseases: Emphysema & Chronic Bronchitis Cystic Fibrosis Asthma Bronchiectasis Some Interstitial Lung Disease: (combined)
Restrictive Lung Diseases:
Diffusion Capacity:
Estimates the transfer of oxygen in the alveolar air to the red blood cell. Factors that influence the diffusion:
- Area of the alveolar-capillary membrane (A)
- Thickness of the membrane (T)
- Driving pressure
- Hemoglobin
A-Decreased:
Decrease the area of the diffusion: Lung/lobar resection, bronchial obstruction, and IPF.
Increase the thickness of the alveolar-capillary membrane: IPF, CHF, pulmonary vascular diseases
Decrease the driving pressure: smoking, CO exposure
Hemoglobin : Anemia, Hemoglobinopathy.
B- Increased:
- Pulmonary hemorrhage
- Polycythemia
- Early CHF
- Asthma
- Exercise
- Obesity
- Left to right shunt
Technique:
- He or CH4 to measure the alveolar volume (VA)
- CO to measure the diffusion capacity (DLCO)
- DLCO
- DLCO corrected to Hgb _(DLCO corr Hgb)_*
- DLCO corrected to CO
- Alveolar Volume
- DLCO adjusted to the alveolar volume _(DLCO/VA)_*
Walking Oxymetry:
Goal: detects the hidden diffusion defect. Technique: check O2 saturation at rest, 4 mins and 6 mins walk. Walking Oxygen Desaturation:
- Diffusion defect.
- V/Q mismatch
- Shunt Criteria for Oxygen Supplementation (Home Oxygen):
- PO2 <55 or Oxygen Saturation <88%
- PO2 <59 with:Pulmonary Hypertension or Polycythemia
Maximal Voluntary Ventilation (MVV):
Measures the ventilatory reserve The subject breaths as hard and fast as possible for 10-15 sec, and then adjust it to 1 min. MVV = FEV-1 times 35- Decreases:
- Poor effort
- Neuromuscular diseases
- Obstructive & restrictive lung diseases
- Heart diseases
- Obesity
Maximal Inspiratory Pressure (Pi max) & Maximal Expiratory Pressure (Pe max):
Goal: To measure the strength of the respiratory muscles. Technique: the amount of pressure the subject can generate in: Deep inspiration (inspiratory muscles): (Pimax) Deep expiration (expiratory muscles): Pemax Normal value: Pimax (-60) & Pemax (+120) cm H2O Indications: Neuromuscular diseases Unexplained decrease in VC & MVV
Weaning (Pimax > -30)
Arterial Blood Gas: Oxygenation (PO2 and FiO2) & Ventilation (PCO2 and PH) Acid – Base balance (PCO2, HCO2, and PH)
Bronchochallenge Tests:
Goal: evaluate the airway hyperresponsivness (asthma). Technique: Methacholine, Histamine, Cold, Exercise…etc. Criteria: 20% decrease in baseline FEV-
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