Anesthetic Equipment and Monitoring — MCQs

Anesthetic Equipment and Monitoring Indian Medical PG Practice Questions and MCQs

Question 351: What is the PIN index number for nitrous oxide?

A. 3-5
B. 2-5
C. 3-6
D. 3-4 (Correct Answer)
E. 2-6

Explanation: ***3-4*** - The **pin index safety system** is a safety feature on anesthetic gas cylinders and equipment, with **nitrous oxide** specifically corresponding to pins in positions 3 and 4. - This configuration ensures that a nitrous oxide cylinder can only be fitted to equipment designed for nitrous oxide, preventing the accidental administration of the wrong gas. *3-5* - This pin index combination does not correspond to a standard medical gas cylinder, indicating a mismatch in the safety system. - Correct identification of pin indices is crucial for patient safety in anesthesia and respiratory care. *2-5* - This pin index combination is used for **air**, not nitrous oxide. - Each medical gas has a unique pin position to prevent errors in gas delivery. *3-6* - This pin index combination does not correspond to any standard medical gas cylinder, highlighting an incorrect identification within the safety system. - The precise arrangement of pins is a critical safeguard against gas mix-ups. *2-6* - This pin index combination is used for **oxygen**, not nitrous oxide. - The pin index system is a physical safety mechanism designed to prevent the connection of an incorrect gas cylinder to the corresponding gas-specific yoke.

Question 352: Anaesthetic circuit that prevents rebreathing of CO2 –

A. Ayre's piece
B. Mapleson D circuit
C. Circle system (Correct Answer)
D. Magill's circuit

Explanation: ***Circle system*** - The **circle system** incorporates a **carbon dioxide absorber** (soda lime or barium hydroxide lime) which chemically removes CO2 from exhaled gases, preventing rebreathing. - It uses both inspiratory and expiratory limbs with one-way valves to ensure unidirectional flow of gases through the CO2 absorber and to the patient. *Ayre's piece* - This is a modification of the **Mapleson F (Jackson-Rees) circuit** and is a non-rebreathing system for pediatric use. - It **prevents rebreathing** by having high fresh gas flow but does not contain a CO2 absorber. *Mapleson D circuit* - The **Mapleson D circuit** prevents rebreathing by using a high fresh gas flow to flush exhaled gases out of the system, not via a CO2 absorber. - It is classified as an **open non-rebreathing system** and effectively prevents CO2 rebreathing if fresh gas flow is sufficient (typically 2-3 times minute ventilation). *Magill's circuit* - The **Magill's circuit** (Mapleson A) is designed to prevent rebreathing at fresh gas flows approximately equal to minute ventilation, but it relies on separating fresh gas flow from exhaled gas, not CO2 absorption. - Rebreathing can occur if the fresh gas flow is not adequate or if there is insufficient emptying of the reservoir bag during expiration.

Question 353: If an anesthetist at high altitude uses plenum vaporizers, what will be the delivered vapor concentration?

A. Lower than concentration at same partial pressure
B. Higher than the concentration at same partial pressure (Correct Answer)
C. Lower than the concentration at lower partial pressure
D. Higher than the original concentration at high partial pressure

Explanation: ***Higher than the concentration at same partial pressure*** - Plenum vaporizers are calibrated at **sea level** and deliver a constant *volume percent* of volatile anesthetic. At high altitude, ambient pressure is lower, meaning a given volume percent represents a **higher partial pressure** of anesthetic. - While the *anesthetic partial pressure* might be what the anesthetist aims for, the *delivered concentration* (volume percent) will be higher than the concentration that would achieve the same partial pressure at sea level because the total pressure is lower. *Lower than concentration at same partial pressure* - This statement is incorrect because a plenum vaporizer will deliver a **higher partial pressure** at altitude for a given dial setting, due to the reduced ambient pressure. - A lower partial pressure for the same set concentration would only occur if the ambient pressure were higher than calibration. *Lower than the concentration at lower partial pressure* - This option is vaguely worded and does not accurately describe the behavior of plenum vaporizers at altitude. When total pressure drops, the *partial pressure* delivered by a plenum vaporizer at a given dial setting will increase, not decrease. - A lower vapor concentration leading to a lower partial pressure is generally true, but it doesn't address the specific issue of a plenum vaporizer's performance at high altitude. *Higher than the original concentration at high partial pressure* - This option is confusing as it refers to "original concentration at high partial pressure" which isn't a standard comparison. The key is that a plenum vaporizer's *delivered volume % remains constant*, regardless of altitude. - However, this constant volume % translates to a higher *partial pressure* when the **ambient atmospheric pressure is lower**, as is the case at high altitude.

Question 354: Gas cylinder with single pin index ?

A. Nitrogen
B. Oxygen
C. Entonox (Correct Answer)
D. Air

Explanation: **Entonox** - Entonox cylinders have a unique **single pin index** safety system to prevent accidental connection to incorrect gas lines. - This distinct pin configuration ensures the delivery of the correct 50% nitrous oxide and 50% oxygen mixture. *Nitrogen* - Nitrogen cylinders typically use a **double pin index** system (7-2 configuration) for connection. - This gas is primarily used for powering surgical equipment and is not a breathing gas. *Oxygen* - Oxygen cylinders are easily identifiable by their **white colour** and use a **double pin index** system (2-5 configuration) for connection. - This prevents interchangeability with other medical gases that have different pin configurations. *Air* - Medical air cylinders are grey and white and use a **double pin index** safety system (1-5 configuration). - This ensures only medical air is connected and used for patient ventilation or nebulization.

Question 355: A 25 year old male is undergoing incision and drainage of abscess under general anaesthesia with spontaneous respiration. Which of the following is the most efficient anaesthetic circuit which can be used in this patient?

A. Mapleson A (Correct Answer)
B. Mapleson D
C. Mapleson B
D. Mapleson C

Explanation: ***Mapleson A*** - This circuit is highly efficient for **spontaneous respiration** due to its design, which effectively sweeps away exhaled CO2 with a low fresh gas flow. - The **reservoir bag** is close to the patient, and the APL valve is at the machine end, preventing rebreathing of carbon dioxide during spontaneous breathing. *Mapleson D* - While versatile, the Mapleson D circuit is considered far more efficient for **controlled ventilation** rather than spontaneous respiration, requiring higher fresh gas flows in the latter. - It features the **APL valve near the patient** and a longer expiratory limb, leading to potential rebreathing of CO2 if fresh gas flows are not sufficiently high during spontaneous breathing. *Mapleson B* - This circuit is generally considered **inefficient for both spontaneous and controlled ventilation** compared to other Mapleson systems. - The fresh gas inlet and APL valve are both near the patient, leading to significant rebreathing unless very high fresh gas flows are used. *Mapleson C* - Similar to Mapleson B, the Mapleson C circuit is also considered **inefficient for spontaneous respiration**, requiring high fresh gas flows to prevent CO2 rebreathing. - It has a very short expiratory limb and the APL valve near the patient, making it less effective for maintaining normocapnia during spontaneous breathing compared to Mapleson A.

Question 356: The pulse oximetry reading is affected in:

A. Jaundice
B. Anemia
C. Red nail polish
D. Dark skin (Correct Answer)

Explanation: ***Dark skin*** - **Dark skin pigmentation**, especially in individuals with very dark complexions, can cause **underestimation of oxygen saturation** by pulse oximetry. - This is due to the increased absorption of light by **melanin**, which can interfere with the device's ability to differentiate between oxygenated and deoxygenated hemoglobin. *Jaundice* - **Jaundice** primarily involves the accumulation of **bilirubin**, which typically does not significantly interfere with the absorption spectra used by pulse oximeters. - While **severe jaundice** might theoretically have a minor effect, it is not considered a primary or common cause of pulse oximetry inaccuracy. *Anemia* - **Anemia** is a reduction in **hemoglobin concentration**, which affects the oxygen-carrying capacity of blood. - Pulse oximeters measure the **percentage of hemoglobin saturated with oxygen**, not the absolute amount of hemoglobin, thus a low hemoglobin count alone does not directly alter the SpO2 reading. *Red nail polish* - **Red nail polish** can absorb and scatter light, especially the red light wavelengths used by pulse oximeters, leading to a falsely low or erroneous SpO2 reading. - This interference can prevent the sensor from accurately detecting the pulsatile blood flow and light absorption characteristics of hemoglobin.

Question 357: The Pin Index Safety System (PISS) number for nitrous oxide (N2O) is

A. 2,6
B. 1,6
C. 3,5 (Correct Answer)
D. 2,5

Explanation: ***3,5*** - The **Pin Index Safety System (PISS)** is designed to prevent incorrect gas tank connections by using specific arrangements of pins on the cylinder yoke. - For **nitrous oxide (N2O)**, the pins are located at positions **3 and 5** on the cylinder valve. *2,6* - This pin configuration corresponds to **air**, which is a mixture of nitrogen and oxygen. - Using this for nitrous oxide would be a **misconnection**, potentially leading to patient harm. *1,6* - This specific pin index combination is associated with **oxygen**. - Incorrectly connecting a nitrous oxide tank to an oxygen yoke position would be a serious **safety breach**. *2,5* - This is the PISS configuration for **carbon dioxide (CO2)**. - Misconnection with nitrous oxide could lead to **hypoxia** or other adverse events due to incorrect gas delivery.

Question 358: According to standard medical gas cylinder color coding, the colour of ethylene cylinder is:

A. Purple (Correct Answer)
B. Orange
C. Blue
D. Grey

Explanation: ***Purple*** - Ethylene gas cylinders are **color-coded purple** to ensure quick and accurate identification in medical settings. - This standardized color coding helps prevent dangerous mix-ups of medical gases. *Orange* - **Orange** is the standard color for **cyclopropane** gas cylinders in many medical gas color-coding systems. - Cyclopropane is an anesthetic agent rarely used today, but its color code differs from ethylene. *Blue* - **Blue** is typically used to identify **nitrous oxide** cylinders, a common anesthetic and analgesic gas. - Mistaking nitrous oxide for ethylene could have significant clinical consequences. *Grey* - **Grey** is commonly associated with **carbon dioxide (CO2)** cylinders, used for insufflation during surgery and as a respiratory stimulant. - This color is distinct from ethylene's purple cylinder.

Question 359: Early and reliable indication of air embolism during anaesthesia can be obtained by continuous monitoring of:

A. Oxygen saturation
B. End Tidal CO2 (Correct Answer)
C. ECG
D. Blood pressure

Explanation: ***End Tidal CO2*** - A sudden and unexplained decrease in **End Tidal CO2 (EtCO2)** is often the first sign of an air embolism. - This occurs because air in the pulmonary circulation obstructs blood flow, leading to reduced CO2 delivery to the lungs. *Oxygen saturation* - **Oxygen saturation** changes are typically a later sign of air embolism, as significant pulmonary impairment or right-to-left shunting must occur before a drop is detectable. - A decrease in saturation indicates a more advanced and potentially severe embolism. *ECG* - **ECG changes**, such as arrhythmias or signs of right heart strain, are usually late and non-specific indicators of air embolism. - These changes reflect the cardiovascular consequences of the embolism rather than its initial event. *Blood pressure* - A drop in **blood pressure** is a late and often profound sign of an air embolism, reflecting significant cardiovascular compromise. - Early detection methods precede observable changes in systemic blood pressure.

Question 360: Hardening of sodalime done by?

A. Sodium silicate (Correct Answer)
B. BaSO4
C. CaCO3
D. CaSO4

Explanation: **Sodium silicate** - **Sodium silicate** solution, also known as **water glass**, is used to harden soda lime. - It reacts with **calcium hydroxide** in the soda lime to form a durable, insoluble matrix, increasing its structural integrity. *BaSO4* - **Barium sulfate (BaSO4)** is an insoluble salt primarily used as a **radiocontrast agent** in medical imaging. - It does not possess properties that would facilitate the hardening of soda lime. *CaCO3* - **Calcium carbonate (CaCO3)** is a common filler or antacid and is a primary component of chalk and limestone. - It does not react with soda lime in a way that would induce hardening; in fact, soda lime is often used to absorb CO2. *CaSO4* - **Calcium sulfate (CaSO4)**, particularly in its hydrated forms (like plaster of Paris), is known for its hardening properties. - However, for hardening soda lime, the interaction with calcium hydroxide specifically favors **sodium silicate** due to the formation of a rigid silicate structure.

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

Want unlimited practice?

Get full access to all questions, explanations, and performance tracking.

Start For Free