Pulmonary embolism: capnogram wave area can help diagnose PE.

Clinical bottom line (level 1b)

Patients with suspected pulmonary embolism who have low capnogram areas were more likely to have a PE (LR+13) .
Patients with capnogram areas > 50 Hg.sec were unlikely to have a PE.

Kline and Arunachlam: Annals of Emergency Medicine 1998; 32 (3): 289-296

Expires September 2003

The study

Setting: emergency department, university hospital, USA

139 patients (aged range 18 to 86 years; mean 44, 60% female) clinically suspected pulmonary embolism referred for ventilation-perfusion scanning

Excluded if

unable to tolerate breathing room air

evidence of shock

clinical evaluation protocol not completed

Independent blinded reference standard, applied in all patients from a consecutive appropriate spectrum.
Reference standard:

ventilation-perfusion scan: low probability cases with DVT on ultrasound, and intermediate probability cases had pulmonary angiography. Other low probability cases were followed for 3 to 6 months by telephone.

Diagnostic test: capnogram waveform area (area under curve produced by one expiration). Subjects breathed room air for 5 minutes, before performing the test.

The evidence

pre-test probability of pulmonary embolism: 14%, (95% CI: 8.0% to 19%)

diagnostic test	pulmonary embolism	no pulmonary embolism	LR (95% CI)	post-test probability
capnogram waveform area <25 Hg.sec	8	4	13 (4.2 to 38)	67%
capnogram waveform area 25-50	11	56	1.2 (0.81 to 1.9)	16%
capnogram waveform >50	0	60	0.0 (0.0 to 0.29)	0%
total	19	120

Comments

Original numbers were calculated from the data in the text.

Citation

Kline JA, and Arunachlam M: Preliminary study of the capnogram waveform area to screen for pulmonary embolism. Annals of Emergency Medicine 1998; 32 (3): 289-296

Search Terms: hand search
Contributor: Chris Ball and Clare Wotton, Unknown Month 2000
Reviewer:

_{Clinical Question.}

_Patient	_{suspected PE}
_{Intervention or Exposure}	_{capnogram wave area}
_Outcome	_diagnosis