Here’s Dr. Alsup with today’s Morning Report!
ETCO2 – Capnography
Technology
-Infrared spectroscopy, co2 absorbs specific wavelength
-Micro sampling vs in line spectroscopy
Physiology
-Aerobic cell metabolism produces co2
-CO2 diffused easily across alveoli and exhaled
-CO2 partial pressure measured
-Small difference between arterial co2 -ETCO2 usually 2-5mm Hg lower
Normal values CO2
ETCO2 and ABG similar: 35-45mm Hg
Venous: 38-52 Hg
Uses:
-Intubation confirmation
-Critical pt monitoring
-Evaluating obstructive airway disease
-Procedural Sedcation
-Detects hypoventilation earlier
-Allows supplemental o2 administration
Waugh et al: meta-analysis reported improved diagnostic performance with capnography. In the meta-analysis, capnography was 17.6 (95% confidence interval [CI] 2.5 to 122) times more likely to detect respiratory depression than standard monitoring alone.
-Assessment of CPR and cardiac death
After 20 minutes of advanced cardiac life support, end-tidal carbon dioxide was 4.4mm Hg in nonsurvivors and 32.8 mm Hg in survivors A 20-minute end-tidal carbon cioxide value of 10 mm Hg or less successfully discriminated between the 35 patients who survived to hospital admissionand the 115 nonsurvivors.
AHA 2010 guidelines: It is reasonable to consider using quantitative waveform capnography in intubated patients to monitor CPR quality, optimize chest compressions, and detect ROSC during chest compressions or when rhythm check reveals an organized rhythm (Class IIb, LOE C). If PETCO2 is <10 mm Hg, it is reasonable to consider trying to improve CPR quality by optimizing chest compression parameters (Class IIb, LOE C).
References:
- Capnography. Emerg Med Clin N Am 26 (2008) 881–897
- Life in the fast lane
- 2010 AHA guidelines
- Robert L. Levine. End-Tidal Carbon Dioxide and Outcome of Out-of-Hospital Cardiac Arrest. N Engl J Med 1997; 337:301-306
Jay Khadpe MD
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