Capnography Waveform Interpretation

Hi friends!!!

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.

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.

NOTE: Dear friends!!! …Please do comment a topic related to
Biomedical, so that we can discuss it in future blogs.

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