Anesthetic Equipment and Monitoring — MCQs

Anesthetic Equipment and Monitoring Indian Medical PG Practice Questions and MCQs

Question 331: Which of the following is NOT a rebreathing system used in anesthesia?

A. Mapleson F (Correct Answer)
B. Circle system
C. To & fro system
D. Water's system

Explanation: ***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.

Question 332: Nephrotoxic anaesthetic agent is :

A. Methoxyflurane (Correct Answer)
B. Isoflurane
C. Halothane
D. Nitrous Oxide

Explanation: ***Methoxyflurane*** - **Methoxyflurane** is metabolized to inorganic fluoride ions, which can cause dose-dependent **nephrotoxicity** by damaging renal tubules and impairing the kidneys' concentrating ability. - Due to its significant risk of kidney damage, **methoxyflurane** is now rarely used as an anesthetic in clinical practice, though it is still used as an inhaled analgesic in some regions. *Isoflurane* - **Isoflurane** has a low metabolic rate and is largely excreted unchanged, making its potential for organ toxicity, including **nephrotoxicity**, much lower compared to methoxyflurane. - It is considered a relatively safe and commonly used inhalational anesthetic for cardiovascular stability and minimal renal effects. *Halothane* - **Halothane** is primarily associated with **hepatotoxicity** (halothane hepatitis) due to its metabolism into reactive intermediates, rather than nephrotoxicity. - While it can cause some degree of renal vasoconstriction, its direct toxic effects on the kidneys are not a primary concern compared to its hepatic risks. *Nitrous Oxide* - **Nitrous oxide** has minimal direct organ toxicity, including to the kidneys, as it is largely eliminated unchanged via the lungs. - Its main concern is its potential to inactivate **vitamin B12**, which can lead to megaloblastic anemia and neurological deficits with prolonged exposure.

Question 333: Diffusion hypoxia is seen with –

A. Cyclopropane
B. Halothane
C. Nitrous oxide (Correct Answer)
D. Ether

Explanation: ***Nitrous oxide*** - **Diffusion hypoxia** occurs when **nitrous oxide** rapidly diffuses out of the blood and into the alveoli during elimination, diluting the partial pressures of oxygen and carbon dioxide. - This rapid diffusion can lead to a transient decrease in the **partial pressure of oxygen** in the alveoli, potentially causing hypoxia if patients are not given supplemental oxygen during recovery. *Cyclopropane* - **Cyclopropane** is an older, potent inhalational anesthetic not commonly used today due to its **flammability** and high risk of **cardiac arrhythmias**. - It does not cause diffusion hypoxia as its blood solubility and elimination characteristics differ significantly from nitrous oxide. *Halothane* - **Halothane** is a potent volatile anesthetic that can cause **dose-dependent myocardial depression** and **hepatotoxicity**. - Its elimination primarily occurs via the lungs, but its relatively high blood solubility and slower wash-out prevent the rapid alveolar gas dilution seen with nitrous oxide, thus not causing diffusion hypoxia. *Ether* - **Ether** (**diethyl ether**) is another historical anesthetic agent known for its strong analgesic properties and slow induction/recovery. - While it has a high blood-gas solubility, its slower kinetics of elimination do not lead to the rapid outward diffusion phenomenon that causes diffusion hypoxia.

Question 334: 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 ?

A. Color doppler
B. Transesophageal echocardiography
C. Bispectral index monitoring (Correct Answer)
D. Pulse plethysmography

Explanation: ***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.

Question 335: Which nerve is used for monitoring anesthesia during surgery?

A. Facial
B. Radial
C. Median
D. Ulnar (Correct Answer)

Explanation: ***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.

Question 336: Which is wrong regarding somato sensory evoked potentials (SSEP)?

A. Can be used during spinal cord surgery to detect spinal cord damage
B. Can be used to monitor CNS during intracranial surgery
C. Can be used intraoperatively inside OT
D. Is contraindicated under general anaesthesia (Correct Answer)

Explanation: ***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.

Question 337: Gas stored in liquid form is:

A. Oxygen
B. Cyclopropane
C. Nitrous oxide (Correct Answer)
D. Carbon dioxide

Explanation: ***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.

Question 338: To what extent must the oxygen content be reduced before an explosion of methane and air is impossible?

A. 10 percent
B. 11 percent
C. 7 percent
D. 12 percent (Correct Answer)

Explanation: ***12 percent*** - An explosion of **methane and air** becomes impossible when the oxygen content is reduced to below **12 percent**. This is the **limiting oxygen concentration (LOC)** or minimum oxygen concentration (MOC) for methane. - Below this threshold, even with a suitable fuel concentration, there is **insufficient oxygen** to sustain a combustion reaction, preventing ignition and explosion. *10 percent* - While 10% oxygen is significantly reduced, the **flammability limit** for methane in air is typically considered to be below 12%. Reducing oxygen to 10% would indeed prevent an explosion, but it's not the precise **minimum threshold**. - This level offers a margin of safety but is not the exact point at which an explosion becomes impossible based on standard flammability data. *11 percent* - Similar to 10%, 11% oxygen is below the **critical concentration** for methane combustion. However, the precise value cited for the **limiting oxygen concentration** for methane is slightly higher, at around 12%. - While this concentration would likely prevent an explosion, it is not the most accurately reported **upper limit** at which an explosion remains possible. *7 percent* - Reducing the oxygen content to **7 percent** would definitely prevent a methane and air explosion as it is well below the **limiting oxygen concentration** of 12%. - This level represents a much safer margin than strictly necessary, as explosions are already prevented at a higher oxygen concentration.

Question 339: When using low-flow circle absorber techniques, the uptake of nitrous oxide must be considered. In a healthy 70 kg adult, the expected uptake of nitrous oxide, with a 70% inspired concentration, after 1.5 hours would be about

A. 500 ml/min
B. 250 ml/min
C. 1000 ml/min
D. 100 ml/min (Correct Answer)

Explanation: ***100 ml/min*** - The uptake of **nitrous oxide (N2O)** decreases significantly over time as the blood and tissue compartments become saturated. After 1.5 hours, the uptake slows considerably. - At this point, the uptake rate for a 70 kg adult with 70% N2O is expected to be approximately **100 ml/min**, reflecting the near-saturation of less vascular tissues. *500 ml/min* - An uptake of **500 ml/min** is typical during the **initial, rapid uptake phase** of nitrous oxide (first 5-15 minutes) as it quickly equilibrates with the blood and highly perfused tissues. - This rate would be too high after 1.5 hours, as the body's capacity to absorb N2O has decreased significantly. *250 ml/min* - This rate represents an **intermediate phase** of N2O uptake, typically occurring within the first 30-60 minutes, when the drug is still being absorbed into moderately perfused tissues. - After 1.5 hours, the uptake would have slowed down further than this rate due to continued saturation of tissue compartments. *1000 ml/min* - An uptake of **1000 ml/min** (or 1 L/min) is an **extremely high rate** of N2O uptake, far exceeding what is physiologically possible in a 70 kg adult even during the initial rapid phase. - This would imply a massive, unsustainable absorption, which is not clinically relevant for N2O in a healthy individual.

Question 340: True about anaesthesia breathing circuit is

A. Oxygen flush delivers more than 135 litres
B. Pipelines is a part of low pressure system
C. Cylinder is a part of high pressure system (Correct Answer)
D. Oxygen flush delivers less than 35 litres

Explanation: ***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.

Practice by Chapter

Anesthesia Machine Components

Practice Questions

Breathing Systems

Practice Questions

Vaporizers

Practice Questions

Gas Cylinders and Pipeline Supply

Practice Questions

Anesthesia Ventilators

Practice Questions

Standard Monitoring: ECG, BP, Pulse Oximetry

Practice Questions

Capnography

Practice Questions

Neuromuscular Monitoring

Practice Questions

Temperature Monitoring

Practice Questions

Invasive Hemodynamic Monitoring

Practice Questions

Equipment Troubleshooting

Practice Questions

Safety Features in Modern Anesthesia Equipment

Practice Questions

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