When performing Oro-pharyngeal suctioning, the nurse uses a suction machine. This works on the principle of creating:

Appeared in: NCL (MP) Nursing Officer - 2020

Explanation

Suction machines work by creating a vacuum, which is a space with pressure lower than the surrounding atmosphere.
This state of lower-than-atmospheric pressure is defined as negative pressure.
The pressure gradient between the patient's airway (higher pressure) and the suction catheter (negative pressure) is what pulls secretions out.
This is the fundamental principle for removing fluids and secretions from body cavities.

Option A: Positive pressure involves pushing air or fluid into a space, which is the opposite of suctioning.
Option C: Atmospheric equilibrium means the pressure inside the suction system is equal to the surrounding room air. With no pressure difference, no suction or flow of secretions would occur.
Option D: Hydrostatic force is the pressure exerted by a column of fluid at rest due to gravity. It is not the mechanism used by a suction machine.

Clinical Relevance

Nursing practice connection: Knowing The physical principle behind the operation of a medical suction machine helps nurses interpret findings accurately and avoid errors in routine assessment, medication administration, and patient teaching.
Understanding that suction creates negative pressure is crucial for patient safety. Excessive negative pressure can cause trauma to the delicate mucosal tissues of the airway, leading to bleeding and swelling.
Nurses must set the suction regulator to the appropriate level (e.g., 100-150 mmHg for adults) to ensure effective secretion removal without causing harm.
What if? If a nurse applies suction while inserting the catheter instead of only during withdrawal? This would cause the catheter tip to grab onto the mucosal lining, stripping it away and causing significant trauma and hypoxia because air is being removed from the lungs during insertion.

How to Approach the Question

First, identify the core of the question, which is asking about the working principle of a suction machine.
Think about what 'suction' means in everyday life—it's the act of pulling something in, like using a vacuum cleaner.
Relate this concept to physics. Pulling something in requires creating a lower pressure at the destination compared to the source. This is known as a negative pressure gradient.
Evaluate the options: 'Positive Pressure' is pushing, the opposite of suction. 'Atmospheric Equilibrium' means no pressure difference, so no flow. 'Hydrostatic Force' relates to gravity and static fluids, not an active machine.
Conclude that 'Negative Pressure' is the only option that accurately describes the creation of a vacuum to draw out secretions.

Concept Tested & Keywords

Concept Tested: The physical principle behind the operation of a medical suction machine.
Stem keywords: Oro-pharyngeal suctioning, suction machine, principle
Lead-in keywords: creating
Negative lead-in flag: false

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E6 Nelson Textbook of Pediatrics(2024) — Volume 1 p. 665-667

E6 Nursing Fundamentals Taylor p. 745-747

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