Obstructive lung disease

At physical exam rounds, we discussed the diagnosis of obstructive lung disease.

There are many potential findings, outlined below, and 3 major papers on the evidence-based diagnosis of obstructive lung disease.


Possible findings:

General inspection:
Signs of respiratory distress (accessory muscle use, indrawing, paradoxical abdominal movement), pursed lip breathing, barrel chest, signs of malnutrition, look for clubbing (not expected in COPD), asterixis from CO2 retention, cyanosis, elevated JVP from cor pulmonale, many other possibilities...

Vitals:
Pulsus paradoxus

Palpation:
Subxiphoid cardiac impulse, palpable P2 from pulmonary HTN

Percussion:
Hyperresonance
Decreased diaphragmatic excursion
Decreased cardiac dullness

Auscultation:
Wheezes

Special manouevers:
Forced expiratory time (Patient takes a deep breath and exhales forcefully with open mouth, and examiner listens over lower trachea)
Laryngeal height- measure the maximum distance between the sternal notch and the thyroid cartilage. Less than 4cm is significant.

Evidence:

From JAMA Rational Clinical exam (1995):

Most sensitive tests (i.e. rule out if not present)- no single test sensitive enough
Most specific tests (i.e. rule in if present)
Wheezing (LR 36)
Barrel chest (LR 10)
Decreased cardiac dullness (LR 10)
Match test (patient unable to blow out match held 10cm in front with open mouth) (LR 7.1)
Hyperresonance
Forced exp time over 9 seconds
Other less useful tests to rule in, but positive LR's: Forced exp time 6-9s, subxiphoid impulse, pulsus paradoxus over 15, decreased breath sounds.


From JGIM- Straus et al, 2002
Took 161 pts with varying disease severity (known, suspected, or no COPD), did spirometry on all, looked at components of history and physical that predicted FEV1 5th percentile.

Key point here is combining findings is powerful in ruling in or ruling out.

Forced exp time over 9 seconds - LR 6.7
Wheezing - LR 4.0
Self-reported COPD LR 5.6

If all 3, LR 59 (rules in). If none, LR 0.3 (i.e. good for ruling out)

Other significant features: Over 40 pack-year smoker: LR 3.3


From JAMA- Straus et al (2000)- primary study, not Rational Clinical Exam

History of smoking over 40 pack-years: LR 8.3
Self-reported COPD: LR 7.3
Maximum laryngeal height less than 4cm LR: 2.8
Age over 45 LR 1.3

If all 4, LR is over 200
If none, LR- is 0.13

Links

For JAMA Rational Clinical Exam abstract click here

For Straus et al JAMA paper click here

For Straus et al JGIM paper click here