Alaris® EtCO2 module
Topic 6: Responding to Abnormal Waveforms

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Abnormal Waveform: *Hypoventilation with Shallow Breathing

Case: Later the nurse noted Mr. Johnson's RR was 10 breaths/minute and EtCO2 was 25 mmHg. He took a deep breath and EtCO2 increased to 58 mmHg.

Clinical Findings & Abnormal Waveform1-3:

  • RR
  • EtCO2 because tidal volumes and less CO2 gas is exhaled
  • Followed by occasional deep breath indicated by sharp upward slope in waveform (see arrow in diagram)

Possible Causes1-3:

  • Over medication/increased sedation
  • Low tidal volume

Possible Responses1-3: Follow hospital protocols, which may include:

  • Assess ABC's (Airway, Breathing, Circulation)
  • Maintain patient airway
  • Encourage patient to take deep breaths
  • Notify Respiratory Therapy and/or M.D.

1Capnography in the Management of the Critically Ill Patient, EducationPAK for Critical Care and Procedural Sedation - A Guide to Capnography. CD-ROM - Needham, MA. Oridion Medical. 2003.
2AACN Procedure Manual for Critical Care 4th Ed. (2001). Ed. Lynn-McHale, D.J. & Carlson, K.K.. American Association of Critical Care Nurses.
3Thalan's Critical Care Nursing Diagnosis and Management 4th Ed. (2001). Ed. Urden, L.D.; Stacy, K.M.; & Lough, M.E. C.V. Mosby

*The following are examples of common EtCO2 waveforms. The waveform trends are examples only and do not represent all potential abnormal waveforms. Analysis of these waveform trends may provide an early indication of the noted possible causes. The associated possible responses are suggestions only and are not meant to replace current clinical practice or hospital protocols. Always consult hospital protocols. Abnormal waveforms are not always associated with alarms.