1 Mosby items and derived items © 2010 by Mosby, Inc., an affiliate of Elsevier Inc. Chapter 9 Pulmonary Function Testing

2 Mosby items and derived items © 2010 by Mosby, Inc., an affiliate of Elsevier Inc. Overview  PFT includes:  Spirometry  Flow volume loop (FVL) before and after bronchodilator inhalation  Lung volume studies  Diffusing capacity (D LCO )  Airway resistance (Raw)  Arterial blood gas (ABG) measurements  Pulmonary response to exercise and bronchial provocation

3 Mosby items and derived items © 2010 by Mosby, Inc., an affiliate of Elsevier Inc. Purpose of PFT  Evaluate cause of pulmonary symptoms  Evaluate abnormalities seen on the CXR and/or CT scan  Follow course of disease and response to treatment  Evaluate perioperative risk for pulmonary complications  Rule out pulmonary pathology in people with high risk for pulmonary dysfunction  Evaluate disability

4 Mosby items and derived items © 2010 by Mosby, Inc., an affiliate of Elsevier Inc. Normal Values  PFT normal values vary with age, height, gender, and race  Height the most important factor predicting lung volumes  The taller the person, the larger the values  Weight important when BMI >30 = restrictive  Gender: males have larger lungs  Race: African Americans, Asians, East Indians have 12% smaller lung volumes

5 Mosby items and derived items © 2010 by Mosby, Inc., an affiliate of Elsevier Inc. PFT Equipment  American Thoracic Society standards  Spirometer: routine flows and volume  Body plethysmograph: TLC and airway resistance studies  Diffusion system: lung diffusion  Gas analysis (carbon dioxide, carbon monoxide, helium, nitrogen, and oxygen)  Nebulizer equipment for albuterol and methacholine

6 Mosby items and derived items © 2010 by Mosby, Inc., an affiliate of Elsevier Inc.  Arterial blood gas analyzer  Treadmill or bicycle for exercise evaluation  Laboratories with smaller volumes of tests  Multifunction device that measures lung volumes, flow rates, diffusing capacity, and response to bronchial provocation  all spirometric values obtained under ambient conditions convert to Body temperature, ambient pressure, saturated (BTPS)

7 Mosby items and derived items © 2010 by Mosby, Inc., an affiliate of Elsevier Inc. Measures of Lung Function  Tidal volume (V T )  Residual volume (RV)  Expiratory reserve volume (ERV)  Inspiratory reserve volume (IRV)  Minute volume (V E )  Vital capacity (VC)  Total lung capacity (TLC)  Functional residual capacity (FRC)  Inspiratory capacity (IC)  Maximal voluntary ventilation (MVV)

8 Mosby items and derived items © 2010 by Mosby, Inc., an affiliate of Elsevier Inc. Measures of Lung Function (cont’d)  Tidal volume  Volume during quiet breathing  Adults: 350 to 600 ml  Stiff lungs: small volumes at higher rate  Obstruction: normal volume at slower rate  Minute volume  Rate x volume  4 to 8 L/min

9 Mosby items and derived items © 2010 by Mosby, Inc., an affiliate of Elsevier Inc. Measures of Lung Function (cont’d)  Vital capacity: maximal volume exhaled  Measured after deepest breath possible  Slow vital capacity (SVC)  Forced vital capacity (FVC)  Proper coaching is essential  Phases  Maximal inspiratory effort  Initial expiratory blast  Forceful emptying of lungs  <20 ml/kg: risk for complications

10 Mosby items and derived items © 2010 by Mosby, Inc., an affiliate of Elsevier Inc. Measures of Lung Function (cont’d)  Total lung capacity  Sum of SVC and RV  Normal % predicted is 80% to 120%  Increased in obstructive diseases due to air trapping  Obtained by body plethysmography, open- circuit nitrogen washout, closed-circuit helium dilution, XR planimetry

11 Mosby items and derived items © 2010 by Mosby, Inc., an affiliate of Elsevier Inc. Body Plethysmography  Boyle’s law  Pressure and volume of a gas vary inversely if temperature is constant  Accurate but body box is expensive  A Calibrated 3l sirynge is use to determine the accuracy of a water-sealed spirometer in measuring lung volumes  Used to measure Lung Volumes

12 Mosby items and derived items © 2010 by Mosby, Inc., an affiliate of Elsevier Inc.

13 Mosby items and derived items © 2010 by Mosby, Inc., an affiliate of Elsevier Inc. Nitrogen Washout  To determine distribution of ventilation  Patient breathes 100% oxygen  Nitrogen analyzer measures diminishing N 2 concentration from lungs  Well-ventilated units empty first  Uneven pattern common in obstructive lung disease

14 Mosby items and derived items © 2010 by Mosby, Inc., an affiliate of Elsevier Inc. Nitrogen Washout  Oxygen 100% for 7 minutes or until nitrogen is washed out of patient’s lungs, by putting an amount of know oxygen volume we can estimate lung volume, 79% of RV is NITROGEN.  If air trapping is present this technique will underestimate total intrathoracic volume

15 Mosby items and derived items © 2010 by Mosby, Inc., an affiliate of Elsevier Inc.

16 Mosby items and derived items © 2010 by Mosby, Inc., an affiliate of Elsevier Inc.

17 Mosby items and derived items © 2010 by Mosby, Inc., an affiliate of Elsevier Inc. Closed-System Helium Dilution  Helium is inhaled and not significantly absorbed from lungs by blood  Helium is diluted in proportion to size of lung volume being measured  Equilibrium takes 7 minutes

18 Mosby items and derived items © 2010 by Mosby, Inc., an affiliate of Elsevier Inc.

19 Mosby items and derived items © 2010 by Mosby, Inc., an affiliate of Elsevier Inc. RV, ERV, and FRC  Residual volume (RV)  Gas left after exhalation  Obtained from TLC studies  TLC-SVC or FRC-ERV  Increased in air trapping  Expiratory reserve volume (ERV)  Maximal gas exhaled from resting status  Functional residual capacity (FRC)  Gas left after full exhalation at resting status  3 way of measuring FRC are Helium, body box, and Nitrogen Washout

20 Mosby items and derived items © 2010 by Mosby, Inc., an affiliate of Elsevier Inc. Indices of Flows  Forced expiratory volume at 1 sec (FEV 1 )  Forced expiratory volume at 3 sec (FEV 3 )  Forced expiratory flow, mid-expiratory (FEF 25%-75% )  Peak expiratory flow (PEF)

21 Mosby items and derived items © 2010 by Mosby, Inc., an affiliate of Elsevier Inc. FEV 1  Maximal volume exhaled during 1st second of expiration  It is a forced maneuver  Varies with age, gender, race, and height  The % predicted is 80% to 100%  Reduced in obstructive and restrictive lung disease

22 Mosby items and derived items © 2010 by Mosby, Inc., an affiliate of Elsevier Inc. FEV 3  3-second point of the expiratory curve  Not as reproducible as FEV 1  Reported as % of the FVC (normal ~95%)  FEF 25%-75%  Average flow rate during middle half of expiratory curve  Normal 65% to 100%  More sensitive to airway obstruction than FEV 1

23 Mosby items and derived items © 2010 by Mosby, Inc., an affiliate of Elsevier Inc. Peak Expiratory Flow  Maximum flow rate achieved during FVC maneuver  Effort dependent  Peak flowmeters are inexpensive  Asthma action plans  Green zone: 80% to 100% of personal best  Yellow zone: 50% to 80%  Red zone: <50% = urgent physician intervention

24 Mosby items and derived items © 2010 by Mosby, Inc., an affiliate of Elsevier Inc. Maximal Voluntary Ventilation  Patient breathes as rapidly and deeply as possible for 12 to 15 seconds  Extrapolated to obtain MMV in 1 minute  MMV reflects:  Status of respiratory muscles  Compliance of thorax-lung complex  Airway resistance  Patient motivation and ability to move air  Important in the preoperative patient

25 Mosby items and derived items © 2010 by Mosby, Inc., an affiliate of Elsevier Inc. Flow Volume Curves (Loops)  Volume plotted on horizontal axis and flow on vertical axis  Fixed or variable upper airway obstruction  COPD/asthma  Restrictive lung disease  Pre- and postbronchodilator curves

26 Mosby items and derived items © 2010 by Mosby, Inc., an affiliate of Elsevier Inc.

27 Mosby items and derived items © 2010 by Mosby, Inc., an affiliate of Elsevier Inc. PFT Before and After Bronchodilators  FVC, FEV 1, FEF 25%-75% and FVL to assess reversibility  Amount of change required to qualify as improvement  FVC >10%  FEV 1 >200 ml or >15%  FEF 25%-75% >20% to 30%

28 Mosby items and derived items © 2010 by Mosby, Inc., an affiliate of Elsevier Inc. Diffusion Capacity (D L )  Determinants of gas exchange  Surface area of membrane  Thickness of membrane  Hemoglobin and blood flow in capillaries  Measures crossing of co from Alveoli to cap and back  Pt breaths in mixture of 4% CO and 16% Helium. Holds breath for sec. Machine reads time of CO crossing membrane and back.  D LCO-SB  Normal: 80% to 120% predicted

29 Mosby items and derived items © 2010 by Mosby, Inc., an affiliate of Elsevier Inc. Bronchoprovocation Testing  Diagnosis of occult asthma  Provoking agents  Inhaled histamine or methacholine  Exercise  Cold air  A 20% decrease in FEV 1 indicates hyperreactive airways

30 Mosby items and derived items © 2010 by Mosby, Inc., an affiliate of Elsevier Inc. Other Applications of PFT  Smoking cessation  Surgery  Sleep apnea  Environmental lung disease

31 Mosby items and derived items © 2010 by Mosby, Inc., an affiliate of Elsevier Inc. Obstructive and Restrictive Disorders  Obstructive  Expiratory flow <80% predicted  TLC >80% predicted (air trapping)  Obstruction changes flow volume loop (FVL)  Fixed: flattened expiratory and inspiratory limbs of FVL  Restrictive  Lung volume <80% predicted

32 Mosby items and derived items © 2010 by Mosby, Inc., an affiliate of Elsevier Inc. Approach to PFT Interpretation  If FVC  >80% predicted = no restrictive  <80% predicted = look at TLC  If TLC  >80% predicted = no restrictive  <80% predicted = restrictive

33 Mosby items and derived items © 2010 by Mosby, Inc., an affiliate of Elsevier Inc. Approach to PFT Interpretation (cont’d)  FEV 1 and FEF 25%-75%  FEV 1 normal and FEF 25%-75% <65% predicted = mild obstructive disease  Response to bronchodilator  If FVC, FEV 1, FEF 25%-75% improve = response

34 Mosby items and derived items © 2010 by Mosby, Inc., an affiliate of Elsevier Inc. Approach to PFT Interpretation (cont’d)  FVL  Scooping of expiratory limb = obstructive  Flattening inspiratory and expiratory limbs = fixed or variable large airway obstruction  D L >80% predicted is normal

35 Mosby items and derived items © 2010 by Mosby, Inc., an affiliate of Elsevier Inc. Pattern Recognition  Asthma  Low FEV 1 and FEF 25%-75% ; normal TLC; normal D L ; response to bronchodilator  Emphysema  Low FEV 1 and FEF 25%-75% ; normal TLC; low D L ; no response to bronchodilator  Pulmonary fibrosis  Low FVC; low FEV 1 but normal FEV 1 /FVC; small TLC, low D L ; no response to bronchodilator