Capnography Waveform Interpretation

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In our previous blog we have seen about capnography, its phases and uses. Please check out for the link below.

CAPNOGRAPHY

Today we are going to see about interpretation of capnography waveform and its indications.

Capnography is a important diagnostic and monitoring equipment used mainly during anesthesia procedure. Failure to used capnography in patients dependent on an artificial airway contributed to more than 70 percent of the ICU related airway deaths.

Therefore it is important for every healthcare professional to know in detail about capnography.

Let’s get into the topic.

WHAT IS

CAPNOGRAPHY?

Capnography is used to measure the amount of carbon dioxide in exhaled air. It is also used in indirect monitoring of carbon dioxide in arterial blood. It has its contribution in the fields of anesthesia and intensive care.

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HOW TO READ

CAPNOGRAPHY

WAVEFORM?

The capnography waveform with a dramatic up sloping plateau phase suggests that the patient has bronchospasm, which means airway is partially blocked or the endotracheal tube has migrated beyond the Carina and into main bronchus.

The capnography waveform with a peaked triangular appearance suggests that there is a significant leak around the tracheal tube or tracheostomy.

Flat capnography waveform indicates that the oesophagus has been mistakenly intubated instead of the trachea, the breathing circuit has become disconnected, the airway has been blocked with secretions.

A top hat appearance of capnography waveform indicates a good unobstructed airway.

COMMON INDICATIONS OF CAPNOGRAM WAVEFORM

APNEA

Apnea means no breath for ten seconds or longer. There is no respiratory effort or respiratory effort without air movement.

Causes of Apnea:

Cardiac arrest, Respiratory arrest, Equipment failure, Displaced airway adjunct.

HYPOVENTILATION

Hypoventilation is a buildup of carbon dioxide as a result of insufficient elimination of the carbon dioxide. Shape of capnogram is normal with rapid increase in phase 2, gradual, smooth and possibly prolonged upslope during phase 3, abrupt descent to baseline during inhalation. Elevated level of above 45 mmHg is seen.

Causes of hypoventilation:

Decrease in respiratory rate, decrease in tidal volume, chest compression during CPR, Obesity hypoventilation.

HYPERVENTILATION

Low carbon dioxide level resulting from excessive elimination through rapid or deep breathing or due to metabolic acidosis. Shape of capnogram is normal with rapid increase in phase 2, gradual, smooth and possibly shortened or peaked upslope during phase 3, abrupt descent to baseline during inhalation. Decreased level of Co2 below 35 mmHg is seen.

Causes of Hyperventilation:

Anxiety/panic disorder, Excessive exercise, Increased respiratory rate, Increased tidal volume.

TACHYPNEA WITH

HYPOCARDIA

Abnormally rapid breathing with reduced Co2. Respiratory rate is rapid and above a rate of 20 breaths per minute. Breathing  pattern is usually regular and occurs at least once in every 3 seconds. Shape of capnogram is normal with rapid increase in phase 2, gradual upslope during phase 3, abrupt descent during phase 0, back to baseline during inhalation.

BRADYPNEA WITH

HYPERCARBIA

Presence of an abnormally high level of carbon dioxide in the circulating blood. Respiratory rate is generally slow and below a rate of 12 breaths per minute, representing bradypnea. As a result of increased levels of exhaled carbon dioxide, capnogram waveform appears enlarged with a rapid increase in phase 2, gradual and smooth upslope during phase 3, abrupt descent during phase 0, back to inhalation. Breathing pattern is usually regular which occurs less than once in every 5 seconds.

HYPOPNEA WITH

BRADYPNEA

Hypopnea is shallow breathing less than 0.5 liters in adult patient. Bradypnea is a low respiratory rate which is less than 12 breaths per minute. The capnogram waveform is abnormal with short, non plateauing waveform and slow respiratory rate followed by a higher concentration of Co2 when a deep breath is taken.

REBREATHING OF CO2

Respiratory rate is generally between 12 and 20 breaths per minute in a adult patient. Breathing pattern usually occurs at every 3 – 5 seconds. Increase or rise in baseline, phase 1 and etco2 value increase with each successive breath or remains same due to hyperventilation.

Now I hope you have acquired some knowledge about capnography. We will discuss in detail about topics related to Biomedical Engineering, Medical Devices, Healthcare in our next blog.

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