Image Based Question-66704

A. End-Tidal Carbon Dioxide

B. Inspiratory point

C. Baseline Inspired Gas

D. Expired Air

Correct Answer » B Explanation

Ans: B. Inspiratory Point.

The image shown is of a Capnograph.

Waveform capnography

• It represents the amount of carbon dioxide (CO2) in exhaled air, which assesses ventilation.

• It consists of a number and a graph.

• The number is capnometry, which is the partial pressure of CO2 detected at the end of exhalation. This is end-tidal CO2 (ETCO2) which is normally 35-45 mm Hg.

• The capnograph is the waveform that shows how much CO2 is present at each phase of the respiratory cycle, and it normally has a rectangular shape

Phases:

• Phase I:

• Starts with exhalation.

• The first gases that pass over the capnography sensor usually do not contain carbon-di-oxide because they are the gases that fill the physiological dead spaces in the “conducting airway” (Lungs, bronchi, trachea, mouth, and nose). This phase is the baseline of the capnograph.

• Phase II:

• Phase II is known as the “Expiratory upstroke “ and trace the steep rise in CO2 level.

• This phase measures a mixture of dead space (No CO2) and alveolar (CO2).

• Phase III:

• The phase represents the “Expiratory plateau” which represents mostly alveolar gas exhalation.

• The plateau is indicative of the homeostasis of the patient.

• The gases released at the end of the expiratory plateau have the highest concentration of CO2.

• This is also known as the “End-tidal point” and is what is measured with calorimetry capnometry or capnography.

• Phase IV:

• This phase reflects the “Inhalational phase”, which brings oxygenated gases into the lung, returning the gas levels and the capnograph waveform to the beginning of a new cycle and the baseline

Causes of end-tidal carbon dioxide changes are as follows:

• Causes of high end-tidal carbon dioxide:

• Malignant hyperthermia, shivering, fever, sepsis, endocrine disease, hypoventilation.

• Cause of low end-tidal carbon dioxide:

• Hypothermia, low cardiac output, hyperventilation, pulmonary embolism.