2007 pfts the forced oscillation technique
TRANSCRIPT
The Forced Oscillation TechniqueThe Future of Pulmonary Function Testing?
Alexander S. Niven, MDClinical Assistant Professor, University of Washington
Director, Respiratory Care ServicesMadigan Army Medical Center
Conflict of Interest Disclosure
Equipment loan from Viasys Inc.
Why Look for New Techniques?
72 yo with bronchiectasis, MAC 21 yo with VCD, possible asthma
Disadvantages of Spirometry
• Requires maximal,
reproducible efforts• Flow limiting segment (FLS)
– Central to peripheral airways
• Maximal expiratory flow
(MEF) is dependent on– Lung recoil pressure– Dynamic airway resistance– Airway properties at FLS
Pride NB. Clin Chest Med 2001; 22(4): 599-622
Lapperre TS et al. Am J Respir Crit Care Med 2004; 170; 449-504
Fabbri LM et al. Am J Respir Crit Care Med 2003; 167: 418-424
Evaluation of Obstructive Lung Disease
• Spirometry, bronchoprovocation testing– Cannot reliably differentiate these patients – Insensitive to early airway changes
Forced Oscillation Technique
• Superimposed external pressure signals on spontaneous tidal breathing
• Effort independent assessment of mechanics– Significant pediatric literature– Increasing interest in adult lung function testing
Dubois AB. J Appl Physiol 1956; 8: 587-94
Smith HJ. Eur Respir Mon 2005; 31: 1-34
DuBois AB, Brody AW, Lewis DH, Burgess BF. Oscillation mechanics of lungs and chest in man. J Appl Physiol 1956; 8: 587-94
Loudspeaker
Transducer
Resistor
Pneumotach
Methodology
• Mono or multi frequency– 2-4 Hz to 30-35 Hz
• Continuous– Pseudo-random noise
(PRN)• Time discrete
– Impulse oscillation (IOS)
Modified from Smith HJ et al.
Smith HJ et al. Eur Respir Mon 2005; 31: 1-34
Impulse Oscillometry Testing
• Seated• Head in neutral
position• Tidal breathing• 20 – 90 seconds• Cheek support
when necessary
Niven A et al. Am J Respir Crit Care Med 2003; 167(7): A419
Large Airways Small Airways
Small Airways Large Airways
Total Respiratory Impedance (Zrs)
Goldman MD. Pulm Pharmacol Ther 2001; 14(5): 341-350
Resistance (Rrs)
Small Airways Large Airways
Normal
COPD
Baseline
Post Bronchodilator
Rrs
Frequency Dependence
Reactance (Xrs)
Small Airways Large Airways
Reactance Area (AX)
Smith HJ et al. Eur Respir Mon 2005; 31: 1-34
Resonant Frequency (frs)
0
Normalfrs
frs = 18 Hz
COPD
Post Bronchodilator
Baseline
AX
http://sunsite.unc.edu/dave/drfun.html
Clinical Applications
• Screening
• Upper airway obstruction
• Obstructive lung disease– Bronchoprovocation testing– Bronchodilator response
• Respiratory Mechanics– Obstructive sleep apnea
Screening• 96 iron workers at 9/11 clean up site• 53 noted new respiratory symptoms
– Cough, dyspnea, wheezing, sinus complaints
Smokers Nonsmokers
FVC,% pred 100 + 14 99 + 10
FEV1, % pred 97 + 15 99 + 13
FEV1/FVC 0.78 + 0.08 0.82 + 0.07
R5, cm H2O/L/s 3.9 + 0.9 3.5 + 0.8
R20, cm H2O/L/s 3.1 + 0.6 3.1 + 0.7
R5-R20, cm H2O/L/s 0.8 + 0.5* 0.5 + 0.3
AX, cm H2O/L/s 3.9 + 0.3* 1.8 + 0.1* p < 0.01Adapted from Skloot G. Chest 2004; 125: 1248-1255
Large Airway Resistance• Large particles deposit in central airways• Increased resistance causes impulse shadow
Large Airways (increased resistance)
Measurement reflects large airways only
Central (Large Airway) Obstruction
Reactive airways at “Ground Zero”
Pre-BD
Post Bronchodilator
Baseline
Courtesy of MD Goldman
Vocal Cord Dysfunction
• Pathologic adduction of vocal cords– 10-15% of young dyspnea patients
• More common in females– Perfectionism, psychiatric conditions
• Etiology may be multifactorial– Conversion disorder– Post-nasal drip syndrome, GERD
Morris M et al. Chest 1999; 116: 1676-1682Newman K et al. Semin Respir Crit Care Med 1994; 15: 162-167Christopher KL et al. N Engl J Med 1983;308:1566-1570
Vocal Cord Dysfunction
Inspiration Expiration
Inspiratory impedance “spikes” due to variable extrathoracic obstruction from VCD
Red = Impedance (H2O/L/s)
Blue = Volume (L)
Bronchoprovocation Testing
• Oscillometry consistently more sensitive in the detection of small airway changes– Greater magnitude of change– Lower dose of challenge agent
• Histamine, methacholine• Eucapneic voluntary hyperventilation, cold air
Hnatiuk OW et al. Chest 2000; 118(4): 198SEvans TM et al. J Asthma 2006; 43(1): 49-55Rundell KW et al. Can Respir J 2005; 12(5): 257-63Evans TM et al. Chest 2005; 128(4): 2412-9
Bronchoprovocation Testing
Courtesy of MD Goldman
Bronchoprovocation Testing
Courtesy of MD Goldman
Lung Allograft Rejection• IOS in 22 bilateral lung allograft recipients
– 5 acute rejection, 7 bronchiolitis obliterans
– Abnormalities in R5 (9), R5-15 (10), frs (12), AX (12)
Goldman MD et al. Respir Physiol Neurobiol 2005; 148: 179-194
Ross D et al. J Heart Lung Transplant 2004; 23: S131
Bronchodilator Response
Gaw, frs, R5 more sensitive to airway changes but demonstrate greater variability than FEV1
sGaw
frs
R5
FEV1
Coefficient of Variation (%)
Test Day
sGaw 9.3 7.8
frs 5.0 7.4
R5 8.4 13.5
FEV1 3.3 3.5
IC 3.2 6.6
Borrill ZL et al. Br J Clin Pharmacol 2005; 59: 379-384
CPAP Titration
Navajas D et al. Am J Respir Crit Care Med 1998; 157: 1524-1530
Impact of Uvulopharyngoplasty
Lin CC et al. Eur Arch Otolaryngol 2006; 263: 241-7
Standardization of Spirometry
• Acceptable and reproducible data
• Reference standards– Diverse demographics
• Interpretation strategies
• Clinical significance of measurements
Adapted from Brusasco V et al, eds. Eur Respir J 2005; 26: 319-338
Data Collection Criteria
• Minimum data acquisition ( > 20 seconds)• Multiple tests• Artifacts
– Swallow, cough– Circuit leak– Tongue, cheeks
• Data coherence
measurementsTongue Artifact
Goldman MD et al. Respir Physiol Neurobiol 2005; 148: 179-194
Reference ValuesHz Male Female
Rrs (cmH20/L/s)
n Age (yrs)
Rrs (cmH20/L/s)
n Age (yrs)
Landser, 1982 4 - 24 2.5 (0.6) 224 26 (10)
Clement, 1983 8 - 24 ~ 2.6 442 29
Gimeno, 1992 10 2.9 (0.8) 102 50
Pasker, 1994 6 - 24 2.6 (0.6) 126 33 (12) 3.0 (0.6) 100 29 (12)
Govaerts, 1994 10 - 32 2.6 (0.7) 32 48 (15) 3.4 (0.7) 28 55 (13)
Pasker 1996 6 - 24 2.5 (0.5) 137 53 (14) 3.1 (0.7) 140 58 (14)
Adapted from Oostveen E. Eur Respir J 2003; 22: 1026-1041
Age and Ethnic Variation
Age > 65 Japanese African American
n 223 166 13
Age (SD) 83 (8) 39 (17) 35 (6)
Rrs (SD) (cmH20/L/s) 2.2 (0.6) M
2.6 (0.7) F
2.8 (0.5)
R5 (SD) (cmH20/L/s) 2.8 (0.7) 3.1 (0.5)
R20 (SD) (cmH20/L/s) 2.4 (0.6) 2.4 (0.4)
R5-R20 (SD) (cmH20/L/s) 0.8 (0.3)
AX (SD) (cmH20/L/s) 4.8 (2.1)
Guo YF et al. Eur Respir J 2005; 26: 602-608Shitoa S et a. Respirology 2005; 10: 310-315Haymore BR et al. Am J Respir Crit Care Med 2005; 2: A32
Which Small Airways?
• Airflow obstruction in COPD correlates to pathologic airway changes (< 2 mm)
• “Small airway resistance” using FOT– Airway resistance– Tissue impedance
• Respiratory compliance• Tissue resistance
• Concomitant lung volume measurements may aid physiologic interpretationHogg JC. N Engl J Med 2004; 350: 2645-2653
Marchal F. Eur Respir J 1996; 9: 253-261
Conclusions
• Promising tool in pulmonary testing
• Minimal cooperation, no maneuvers
• Unique tool to evaluate central airways
• Sensitive to peripheral airway changes and respiratory mechanics
• Further standardization is needed
The Future of Pulmonary Function Testing?
COPD and Plethysmography
• Increased interest in inspiratory capacity
• Indirect measurement of small airways
• Influenced by – Patient effort– Respiratory muscle
strength
Gibson GJ. Clin Chest Med 2001; 22(4): 623-635
Sutherland RE et al. NEJM 2004; 350: 2689-97
