Below image shows a monitoring device attached to a patient’s airway circuit displaying waveform and numerical values of exhaled gases. What is the primary use of this device?

1. A

   . To check peak inspiratory pressure

2. B

   To check expiratory pressure

3. C

   To check PCO₂ level in expired air

4. D

   . To check PO₂ in expired air

Appeared in: NORCET 10 Prelims-2026

Explanation

• The image displays a mainstream capnography sensor (Capnostat 5), which is specifically designed to measure carbon dioxide.
• Capnography is the monitoring of the concentration or partial pressure of carbon dioxide (CO2) in respiratory gases.
• Its primary use is to continuously measure the end-tidal CO2 (EtCO2), which reflects the patient's ventilation status.
• The normal value for EtCO2 is between 35 and 45 mmHg.

Why Other Options Were Wrong

• Option A: Peak inspiratory pressure (PIP) is the maximum pressure reached during inspiration. It is a measure of lung compliance and airway resistance, monitored by the ventilator's pressure manometer, not a capnograph.
• Option B: Expiratory pressure, such as Positive End-Expiratory Pressure (PEEP), is the pressure maintained in the lungs at the end of expiration. This is set and monitored on the mechanical ventilator.
• Option D: Measuring the partial pressure of oxygen (PO2) assesses oxygenation, not ventilation. This is done using pulse oximetry (for SpO2) or arterial blood gas analysis (for PaO2), not capnography.

Related Visual

Clinical Relevance

• Nursing practice connection: Prioritize focused assessment, early escalation, and real-time monitoring when managing Identification and function of capnography equipment in respiratory monitoring in acute care settings.
• Capnography is the gold standard for confirming correct endotracheal tube (ETT) placement immediately after intubation. The presence of a consistent EtCO2 waveform confirms the tube is in the trachea, not the esophagus.
• It provides critical, real-time feedback on the effectiveness of ventilation and chest compressions during cardiopulmonary resuscitation (CPR).
• A sudden drop in EtCO2 can indicate catastrophic events like cardiac arrest, ETT displacement, ventilator disconnection, or massive pulmonary embolism, allowing for rapid intervention.

How to Approach the Question

• First, carefully examine the image. Identify the device as a 'Capnostat 5' sensor, noting its design with two airway connectors.
• Recognize that the prefix 'capno-' relates to carbon dioxide. This immediately links the device to CO2 monitoring.
• Read the question stem, which asks for the 'primary use' of this device that monitors 'exhaled gases'.
• Evaluate the options based on your identification. Option C, 'To check PCO2 level in expired air,' directly matches the function of a capnograph.
• Eliminate the other options by recalling how they are measured: pressures (A and B) are measured by the ventilator, and oxygen (D) is measured by a pulse oximeter or ABG.

Concept Tested & Keywords

• Concept Tested: Identification and function of capnography equipment in respiratory monitoring.
• Stem keywords: monitoring device, airway circuit, waveform, exhaled gases
• Lead-in keywords: primary use
• Clinical cues: The image shows a 'Capnostat 5' sensor, which is a brand name for a capnograph.

Question ID

QvaJPjMi6AYZBxGZMFvvhm

Copy ID

Reference Book

E6 Nursing Fundamentals Potter Perry 12e Part 3 p. 24-26

E6 Nursing Fundamentals Taylor p. 720-722