Pulmonary Function Testing

1. Pulmonary Function Testing SPECIALIZED TEST REGIMENS

2. The diagnosis of specific pulm. disorders requires certain testing •  The subject must go through a thorough Hx •  Regimens • Clinic or MDs office • VC, FVC, FEVT, FEVT%, FEF 25-75, 200-1200, MVV, VT, f, VE • Hospital lab & CP lab • lung volumes and diffusing capacity

3. PULMONARY FUNCTION TESTING IN CHILDREN • Uses many of the same basic tests as for adults • Differences exists in dimensions and two main areas of concern • newborns, infants, and very young children cannot strictly perform tests that require and depend on pt. cooperation ( VC, FVC, MVV and DLCO) • young children may perform with variability those tests that are effort dependent and require cooperation

4. A cooperative patient and good PFT technologist • Children may not meet ATS criteria but careful evaluation of partial parameters can provide important information.

5. Techniques for infants and young children • Partial Exp. Flow-Volume Curves ( PEFV) - record of the maximal flow developed over a portion of the VC The forced exhalation is obtained by applying either a positive pressure to the thorax and abdomen or a negative pressure to the airway

6. RAPID THORACOABDOMINAL COMPRESSION ( RTC) the “squeeze” or “hug” • Non-intubated infants • uses an inflatable jacket that surrounds the thorax and abdomen • the PEFV is obtained by rapidly applying pressure to the thorax and abdomen at the end of insp. • performed after the infant has fallen asleep or slightly sedated ( chloral hydrate) • flow is measured using an infant mask sealed with a lubricant and attached to a low Ds pneumotach

7. Flow @ FRC or Vmax FRC • By Rapid Thoraco-Abd. Compression(Squeeze) expiratory flow limitations can now also be measured in babies. The baby wears an inflatable cuff with the help of which a forced expiration is produced.From Viasys (Jaeger)

8. WOW! • testing

9. RAISED VOLUME RAPID THORACOABDOMINAL COMPRESSION - RVRTC •  Standardization of spirometry is dependent on TLC • during insp., flow is augmented by a pump to increase pressure and volume • the airway is occluded at the exh. port using a cuff with variable pressure - rapid chest compression is then performed - higher flows are generated • uses a pump to increase volume before the squeeze is performed

10. METHODS • FORCED DEFLATION TECHNIQUE - The infant needs to intubated, sedated & paralyzed • the lungs are manually inflated to TLC using approx. +40 cmH20 - performed 4 times with a 2-3 sec breath hold • the airway is then connected to a source of negative pressure ( -40 cmH20) • air is evacuated for a max. of 3 secs or until airflow ceases • exp. flow is plotted on a flow - volume graph • lungs are reinflated with 100 % O2 • reserved for the critically ill

11. BRONCHODILATOR BENEFIT TEST • Is the dz is reversible? Let’s find out. • Indication • a pt. with an FEV1% of less than 70% • Technique • follow guidelines on withholding certain meds prior to test • do PFT - give tx with bronchodilator via neb or MDI - wait 15-20 mins before doing post tests • monitor pt. for adverse effects

12. Significance Calculate “ percent change of each parameter” %change = postdrug - predrug predrug FEV 1 or FVC are evaluated - an increase of > 12 % and > 200 ml is significant asthma shows the best improvement SGaw should increase 30-40 % to be significant

13. BRONCHOPROVOCATION  (METHACHOLINE CHALLENGE)

14. Methacholine • Used to determine whether or not a patient has a disorder of airway hypersensitivity • And to what extent • Is a parasympathomimetic • May trigger bronchospasm

15. Methacholine challenge • the test is positive when there is a 20 % decrease in the FEV 1 - the concentration at which the decrease occurs is called the provocative concentration or PC20% • Healthy subjects do not display a decrease in FEV1 greater than 20 % • SGaw can be used with FEV1 to demonstrate a reaction • Use a 16 mg/ml stock methacholine solution

16. Technique • Subjects should be tested when asymptomatic, baseline FEV 1 > 70 % of the pt. norm • Withhold meds according to chart • 2 methods accepted by ATS,1st baseline spiro • 5-breath dosimeter method • 2-minute tidal breathing method

17. 5-Breath Dosimeter Method • Dosimeter- deliveres a consistent volume of drug • Uses 5 doses each 4 x larger than the previous • pt. inhales 5 nebulized NS breaths 1st • perform spirometry • if no positive response, start dosimeter inhalations of 5 breaths for 2 minutes • Repeat spirometry • Use largest FEV1 and the average of 2 RAW • Look for > 20% drop in FEV1 and>35% drop in SGAW

18. 2-Minute Tidal Breathing Method • Use nebulizer, nose clips and relaxed breathing • Perform diluent inhalation first, then spirometry • 10 double concentrated doses are used, each dose is breathed for exactly 2 minutes • Spirometry is performed 30 & 90 seconds after the dose • Look for > 20% in FEV1 and >35% drop in SGAW • Give a bronchodilator & repeat spirometry in 10”

19. To caluculate the percent of decrease • %Decrease = Con. FEV1 – Current FEV1 Control FEV1

20. Preoperative PF Testing- to… • Estimate postop lung function • Plan periop care • Estimate morbidity & mortality • Look at • Spirometry/obstruction • Bronchodilation studies • ABG’s, Ex. Testing & DLCO

21. PULMONARY FUNCTION TESTING FOR DISABILITY • Respiratory impairment - the failure of one or more functions of the lungs as determined by PFT • Disability - the inability to perform tasks required for employment and includes medically determinable physical or mental impairment - the impairment must be expected to result in death or last for at least 12 months

22. To determine impairment • should characterize the type, extent and cause of impairment • other factors need to be known - age, educational background and the subjects motivation and energy requirements • for pulm. dz impairment, you also need a hx, physical, CXR, other appropriate imaging techniques and PFT’s - (should be specific to disorder being investigated)

23. FVC and FEV1 • spirometry is the most useful for determination of impairment caused by airway obstruction • the subject should be stable- use largest of the 3 tests • the 2 largest FVC and FEV1 should be within 5% or 100 cc • should be cont. for 6 secs or no volume change detected for 2 secs • - must have a volume-time tracing so hand calculations can be performed • before and after bronchodilator - all parameters reported in BTPS and ht. obtained without shoes or arm span method • must use disability limits • Calibration of equipment is specific and must be documented

24. DLCO & ABG’s • useful in determining disability for restrictive disorders • should not be corrected for Hgb or COHb abnormalities but… the values at the time of the test should be noted • if the DLCO is > 40% predicted but < 60% , get resting ABG • ABGs • may be nonspecific due to various factors • look at other parameters along with ABGs

25. Exercise Testing • subjects considered should have resting ABGs • a Steady State protocol using the treadmill is preferred • specific protocols should be followed • Limits for determining disability on the bases of pulm. impairment have been set for the US by the SS administration