Anesthetic Equipment and Monitoring Practice Questions

Q: All of the following cause a decrease in pulse oximeter readings except:

CarboxyHb. ***CarboxyHb*** - **Carboxyhemoglobin (COHb)** absorbs light similarly to oxyhemoglobin at 660 nm, causing the pulse oximeter to **overestimate oxygen saturation** rather than decrease the reading. - The pulse oximeter cannot differentiate between oxyhemoglobin and carboxyhemoglobin, leading to a falsely elevated or normal SpO2 reading despite **tissue hypoxia**. *MetHb* - **Methemoglobin (MetHb)** absorbs light equally at both 660 nm and 940 nm, causing the pulse oximeter reading to trend towards **85% regardless of the true arterial oxygen saturation**. - High levels of MetHb can lead to an artificially low or inaccurate SpO2 reading, reflecting a **functional hypoxemia**. *Hb-S, Hb-F* - **Hemoglobin S (HbS)** and **Hemoglobin F (HbF)**, when present in significant concentrations, can **interfere with accurate pulse oximetry readings**. - While not universally causing a direct decrease, their altered light absorption properties can lead to **inaccurate and often lower SpO2 values** compared to actual arterial oxygen content, particularly HbS which can aggregate. *Sulf-Hb* - **Sulfhemoglobin (SulfHb)** is a very rare form of hemoglobin that absorbs light uniquely at wavelengths measured by pulse oximeters, causing a **significant decrease in SpO2 readings**. - Sulfhemoglobinemia typically results in an SpO2 reading between **80-85%**, regardless of the actual oxygen saturation, similar to methemoglobin but with slightly different spectral properties.

Q: In anesthesia, fitting of wrong gas cylinder to the anesthesia machine can be prevented by:

Pin index system. ***Pin index system*** - The **pin index safety system** is a safety feature on anesthetic machines that ensures the correct gas cylinder is connected to the corresponding gas inlet. Each gas cylinder type has a unique pin configuration that only matches the specific yoke for that gas. - This system **prevents accidental connection** of a wrong gas cylinder, which could have serious patient safety implications. *Yoke assembly* - The **yoke assembly** is the component that holds the gas cylinder in place on the anesthesia machine. - While it's part of the connection, it's the **pin index system within the yoke** that provides the safety mechanism, not the yoke assembly itself. *Gas analyser* - A **gas analyzer** is used to measure the concentration of gases being delivered to the patient or exhaled by the patient during anesthesia. - It functions as a **monitoring device** and does not prevent the initial incorrect connection of a gas cylinder. *Bodok seal* - A **Bodok seal** is a type of washer often made of neoprene or nylon that provides a tight seal between the gas cylinder and the yoke assembly. - Its primary function is to **prevent gas leaks**, not to ensure that the correct type of gas cylinder is connected.

Q: Which of the following is NOT a rebreathing system used in anesthesia?

Mapleson F. ***Mapleson F*** - This system is known as the **Jackson-Rees modification** of the Mapleson T-piece and is a **non-rebreathing system** used primarily in pediatric anesthesia. - It features an **open-ended reservoir bag** attached to the expiratory limb, allowing for manual ventilation without rebreathing of expired gases if fresh gas flow is adequate. *Circle system* - The **circle system** is a common **rebreathing system** in anesthesia characterized by unidirectional valves and a CO2 absorber, allowing rebreathing of expired gases after CO2 removal. - It utilizes a **low fresh gas flow** to conserve anesthetic agents and moisture, making it a more economical and environmentally friendly choice. *To & fro system* - The **to & fro system** is an older type of **rebreathing system** that uses a soda lime canister placed directly in the breathing circuit, allowing exhaled gases to pass back and forth through it. - While effective for CO2 absorption, it is less commonly used now due to problems with heat buildup, airway resistance, and potential for caustic dust aspiration. *Water's system* - The **Water's system**, also known as the Waters-Dale system, is a type of **closed-circuit rebreathing system** that was also used for CO2 absorption. - It features a canister of CO2 absorbent placed close to the patient, enabling rebreathing of anesthetic gases.

Q: The instrument below is used for

Oesophageal temperature probe. **Oesophageal temperature probe** - This instrument, typically a thin, flexible tube with a sensor, is inserted into the **oesophagus** to continuously monitor **core body temperature**. - It is often used during surgery, critical care, or in situations where precise temperature management is essential, as the oesophagus is close to large blood vessels and well-perfused organs. *Endoscopic ultrasound probe* - An **endoscopic ultrasound probe** is much thicker and has an integrated ultrasound transducer at its tip for imaging internal organs from within the gastrointestinal tract. - It would be too bulky and complex for simple temperature monitoring and is used for diagnostic and staging purposes, not basic physiological monitoring. *Enterography* - **Enterography** refers to an imaging study (CT or MR enterography) used to visualize the small intestine, often involving oral contrast administration. - It is a diagnostic technique that does not typically involve inserting a dedicated probe like the one described for continuous monitoring. *None of the options* - This option is incorrect because the instrument described and depicted is clearly an **oesophageal temperature probe**, serving a specific and recognized medical function.

Q: A 40–year female has to undergo incisional hernia surgery under general anaesthesia. She complains of awareness during her past cesarean section. Which of the following monitoring techniques can be used to prevent such awareness ?

Bispectral index monitoring. ***Bispectral index monitoring*** - **Bispectral Index (BIS) monitoring** is a technology that processes electroencephalogram (EEG) signals to provide a numerical value (0-100) indicating the patient's **level of consciousness or depth of anesthesia**. - A lower BIS value (typically 40-60) indicates a suitable depth of anesthesia for surgery, helping to prevent **intraoperative awareness**, especially in patients with a history of it. *Color doppler* - **Color Doppler** is an imaging technique used to visualize blood flow in vessels and assess the speed and direction of flow. - It is primarily used to diagnose conditions like **deep venous thrombosis**, *arterial stenosis*, or to evaluate blood flow to organs, and has no direct role in monitoring depth of anesthesia. *Transesophageal echocardiography* - **Transesophageal echocardiography (TEE)** is an invasive imaging technique that uses ultrasound from a probe inserted into the esophagus to provide detailed images of the heart. - TEE is critical for assessing **cardiac function**, *valvular heart disease*, or *aortic dissection* during surgery, but it does not monitor brain activity or the depth of anesthesia. *Pulse plethysmography* - **Pulse plethysmography** is a non-invasive method that measures changes in blood volume in a part of the body, often used to determine **heart rate** and assess peripheral perfusion. - While it is a component of pulse oximetry, it does not provide information about the **depth of anesthesia** or brain activity.

Q: Which nerve is used for monitoring anesthesia during surgery?

Ulnar. ***Ulnar*** - The **ulnar nerve** is commonly used for monitoring the depth of neuromuscular blockade during anesthesia due to its accessibility and predictable motor response. - Stimulation typically occurs at the wrist, and muscle contractions (twitches) in the **adductor pollicis muscle** are observed or measured. *Facial* - While the **facial nerve** can be used, it's generally reserved for procedures specifically involving the head and neck, as it can be less accessible and its responses may vary. - Monitoring the facial nerve often involves observing muscle contractions around the eye (**orbicularis oculi**) or mouth. *Radial* - The **radial nerve** is less commonly used for routine neuromuscular monitoring because its motor responses can be more variable and less easily isolated than the ulnar nerve. - Its stimulation can lead to complex movements, making quantitative assessment difficult. *Median* - Similar to the radial nerve, the **median nerve** is not the primary choice for routine neuromuscular monitoring due to potential for more diffuse muscle responses compared to the ulnar nerve. - Monitoring the median nerve would involve observing flexion of the fingers and thumb, which can be less precise for blockade assessment.

Q: Which is wrong regarding somato sensory evoked potentials (SSEP)?

Is contraindicated under general anaesthesia. ***Is contraindicated under general anaesthesia*** - This statement is incorrect because **somatosensory evoked potentials (SSEPs)** are routinely used under **general anesthesia** to monitor neurological function during surgery. - Anesthetic agents can affect SSEP waveforms (e.g., increased latency, decreased amplitude), but techniques exist to adjust for these effects and maintain monitoring utility. *Can be used during spinal cord surgery to detect spinal cord damage* - **SSEPs** are valuable for monitoring the integrity of the **dorsal columns** (sensory pathways) in the spinal cord during procedures that risk spinal cord injury. - A significant change in SSEP amplitude or latency can indicate impending or actual **spinal cord damage**, allowing for timely intervention. *Can be used to monitor CNS during intracranial surgery* - **SSEPs** can be used to monitor the cortical and subcortical sensory pathways during **intracranial surgeries**, especially those involving areas like the **somatosensory cortex** or brainstem. - This helps to detect and prevent iatrogenic injury to these critical sensory pathways. *Can be used intraoperatively inside OT* - **SSEPs** are a common form of **intraoperative neurophysiological monitoring (IONM)**. - They are actively used in the operating room during various surgical procedures to assess the functional integrity of sensory nerves, spinal cord, and brain.

Q: Gas stored in liquid form is:

Nitrous oxide. ***Nitrous oxide*** - **Nitrous oxide** has a critical temperature of 36.5°C, meaning it can be stored as a **liquid** at ambient temperatures under pressure. - Due to its physical properties, it is commonly supplied in cylinders as a **liquid-gas mixture**, with the liquid phase vaporizing as gas is drawn off. *Oxygen* - **Oxygen** has a very low critical temperature (-118°C), making it a **permanent gas** at normal room temperature and pressure. - It exists only in a **gaseous state** in cylinders at ambient temperatures, no matter how much pressure is applied. *Cyclopropane* - **Cyclopropane** is a highly flammable anesthetic gas that has largely been replaced due to safety concerns. - While it has a critical temperature of 124.7°C, which would allow it to be liquefied, it is typically supplied as a **gas** in cylinders, and its clinical use is now rare. *Carbon dioxide* - **Carbon dioxide** has a critical temperature of 31°C, allowing it to be stored as a **liquid** in cylinders. - However, the question asks for a gas commonly stored in liquid form in medical contexts, and while CO2 can be, **nitrous oxide** is the most prominent example of a medical gas stored this way.

Q: True about anaesthesia breathing circuit is

Cylinder is a part of high pressure system. ***Cylinder is a part of high pressure system*** - The **cylinders** containing medical gases (e.g., oxygen, nitrous oxide) are stored under very high pressure, typically **2000 psi** (pounds per square inch) or more, classifying them as part of the high-pressure system. - The high-pressure system also includes components like the cylinder **pressure gauge** and the **pressure regulator**, which reduce the gas pressure to a safer, more manageable level before entering the low-pressure system. *Oxygen flush delivers more than 135 litres* - The **oxygen flush mechanism** typically delivers oxygen at a rate of 35-75 L/min (liters per minute), which is significantly less than 135 L/min. - This function bypasses the flowmeters and vaporizer, providing a rapid surge of **unvaporized oxygen** directly to the breathing circuit. *Pipelines is a part of low pressure system* - **Medical gas pipelines** (e.g., oxygen, nitrous oxide, air) deliver gases from a central supply (like a bank of cylinders or a liquid oxygen tank) at an intermediate pressure, typically around **50-55 psi**, to wall outlets in the operating room. - This intermediate pressure is then further reduced by pressure regulators at the anesthesia machine to enter the low-pressure system, making pipelines an **intermediate pressure system** rather than a low-pressure one. *Oxygen flush delivers less than 35 litres* - The **oxygen flush valve** delivers oxygen at a rate of approximately **35-75 L/min**, not less than 35 L/min. - This high flow rate is used for rapidly filling the breathing bag or diluting anesthetic gases.

Question 1

All of the following cause a decrease in pulse oximeter readings except:

Accepted Answer

CarboxyHb

Answer

MetHb

Answer

Hb-S, Hb-F

Answer

Sulf-Hb

Question 2

In anesthesia, fitting of wrong gas cylinder to the anesthesia machine can be prevented by:

Accepted Answer

Pin index system

Answer

Yoke assembly

Answer

Gas analyser

Answer

Bodok seal

Question 3

Which of the following is NOT a rebreathing system used in anesthesia?

Accepted Answer

Mapleson F

Answer

Circle system

Answer

To & fro system

Answer

Water's system

Question 4

The instrument below is used for

Accepted Answer

Oesophageal temperature probe

Answer

Endoscopic ultrasound probe

Answer

Enterography

Answer

None of the options

Question 5

A 40–year female has to undergo incisional hernia surgery under general anaesthesia. She complains of awareness during her past cesarean section. Which of the following monitoring techniques can be used to prevent such awareness ?

Accepted Answer

Bispectral index monitoring

Answer

Color doppler

Answer

Transesophageal echocardiography

Answer

Pulse plethysmography

Question 6

Which nerve is used for monitoring anesthesia during surgery?

Accepted Answer

Ulnar

Answer

Facial

Answer

Radial

Answer

Median

Question 7

Which is wrong regarding somato sensory evoked potentials (SSEP)?

Accepted Answer

Is contraindicated under general anaesthesia

Answer

Can be used during spinal cord surgery to detect spinal cord damage

Answer

Can be used to monitor CNS during intracranial surgery

Answer

Can be used intraoperatively inside OT

Question 8

Gas stored in liquid form is:

Accepted Answer

Nitrous oxide

Answer

Oxygen

Answer

Cyclopropane

Answer

Carbon dioxide

Question 9

True about anaesthesia breathing circuit is

Accepted Answer

Cylinder is a part of high pressure system

Answer

Oxygen flush delivers more than 135 litres

Answer

Pipelines is a part of low pressure system

Answer

Oxygen flush delivers less than 35 litres

Question 10

True about anesthesia cylinders is all EXCEPT:

Accepted Answer

DISS is the safety mechanism to prevent wrong fitting of cylinder to machine.

Answer

Most commonly used cylinder is type E.

Answer

Air is stored in cylinder with grey body with black and white shoulder.

Answer

Cylinders are part of high pressure system.

Anesthetic Equipment and Monitoring — MCQs

Anesthetic Equipment and Monitoring — MCQs

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