During use of the ventilator on an anesthesia machine, positive pressure is noted on the airway pressure gauge during exhalation. Positive end-expiratory pressure has not been purposefully added to the breathing circuit. Which of the following is the most likely cause?

An otherwise healthy 16-year-old girl is undergoing posterior spinal fusion for thoracolumbar scoliosis. During the procedure, the most likely cause of a marked decrease in the amplitude of the somatosensory evoked potentials after stimulation of the posterior tibial nerve is

A radial artery catheter is to be used for blood pressure measurement during a sitting craniotomy. When zeroing the transducer, which of the following describes the best levels for placement of the transducer and opening of the system to air? (Transducer, Opening to Air)

In a 5-kg child, the end-tidal carbon dioxide tension is 35 mmHg during spontaneous ventilation through a Mapleson D system. Which single change is most likely to increase this value?

The two E oxygen cylinders on an anesthesia machine have pressure readings of 1100 psi each. At an oxygen flow of 3 L/min, there will be sufficient oxygen for approximately

Oxygen 100 ml/min is bubbled through a vaporizer containing an anesthetic with a vapor pressure of 150 mmHg, and this mixture is added to a fresh gas flow of 5 L/min. The delivered anesthetic concentration is

The Bain circuit

Which of the following will occur if the top of the oxygen flowmeter is cracked and leaking during anesthesia with nitrous oxide and oxygen?

A patient whose trachea is intubated develops partial airway obstruction two hours after induction of fentanyl, nitrous oxide, oxygen anesthesia. The anesthesiologist discontinues the nitrous oxide and controls ventilation, and there is gradual improvement during the next hour. No evidence of a respiratory disorder is found at the conclusion of the anesthetic. Which of the following is most likely?

A 5-year-old boy is to undergo microlaryngeal carbon dioxide laser vaporization of laryngotracheal papillomas under halothane administered through a small polyvinylchloride (PVC) endotracheal tube. The diluent gas mixture LEAST likely to support laser combustion of the PVC tube is

A 75-year-old man with a left bundle branch block is undergoing placement of a pulmonary artery catheter through the right internal jugular vein. He becomes pale and his heart rate decreases to 40 bpm when the catheter tip enters the right ventricle. The most likely cause is

The most sensitive means of detecting venous air embolism is

An isoflurane-specific vaporizer that is 25% full is mistakenly refilled with halothane, and the dial is set at 1.5%. Which of the following statements concerning this situation is true?

A pulmonary artery catheter is placed in an awake patient breathing room air. Typical right ventricular and pulmonary artery pressure tracings are obtained. With the catheter balloon inflated, blood drawn from the distal port has a PaO2 of 100 mmHg, while a simultaneous radial artery sample has a PaO2 of 90 mmHg. These data indicate that the

During anesthesia with nitrous oxide, oxygen, and a relaxant, the patient's lungs are being mechanically ventilated and there is a heated humidifier in the circuit. The most likely cause of an apparent increase in inspired oxygen concentration is

Arterial pressure in the radial artery is 155/70 mmHg measured by a correctly calibrated catheter-transducer system. At the same time aortic pressure is 140/75 mmHg using a high-fidelity catheter tip transducer. The most likely cause of this discrepancy is

Postoperatively, a patient is being mechanically ventilated by a constant-flow, pressure-cycled ventilator with the following initial settings: inspiratory/expiratory (I/E) ratio of 1:2, peak inspiratory pressure (PIP) of 25 cmH2O, and rate of 10/min. One hour later, the I/E ratio is 1:4. Which of the following would ensure that the minute ventilation is the same as that initially set?

Each of the following factors may lead to erroneous readings using pulse oximetry EXCEPT

Following antagonism of a nondepolarizing muscle relaxant with neostigmine, twitch height is normal. To achieve this effect, the percentage of the acetylcholine receptor pool that must be free of muscle relaxant is

Which of the following is a characteristic of the Bain breathing circuit?

A 16-year-old child has an arterial catheter inserted prior to a potentially difficult intubation for a craniofacial operation. While awake and breathing room air, arterial blood gas values are: PaO2 134 mm Hg, PaCO2 28 mm Hg, and pH 7.45. These values can be explained by

In the operating room

On routine inspection of an anesthesia machine, the nitrous oxide E cylinder pressure is 360 psi. This indicates that the

With direct arterial blood pressure monitoring

Electrocautery units operate at frequencies between 300 kHz and 2 mHz to

The principal rationale for the use of warmed humidified inspired anesthetic gases in children is to

A 46-year-old patient who abuses intravenous drugs develops acute aortic valvular insufficiency from bacterial endocarditis. Which of the following statements concerning pressures measured through a pulmonary artery catheter is true?

A healthy 57-year-old man with a ureteral calculus is scheduled for immersion extracorporeal shock wave lithotripsy. Which of the following statements is true?

An 88-kg man is anesthetized with 66% nitrous oxide, 33% oxygen, and 1% isoflurane using a circle system. Following tracheal intubation, the nitrous oxide flow is set at 1 L/min and the oxygen flow is set at 0.5 L/min. After two hours the oxygen monitor indicates a circuit oxygen concentration of only 25% despite the flows noted above. The most likely explanation for this discrepancy is

During surgery with a carbon dioxide laser, which inhaled gas mixture is LEAST likely to promote combustion of the endotracheal tube?

A 35-kg child requires mechanical ventilation with pure oxygen at a tidal volume of 350 ml and a rate of 20/min during a severe asthma attack. The most likely cause of severe hypotension after initiating mechanical ventilation is

Maximum current is delivered to the myocardium by a countershock for defibrillation when

While delivering nitrous oxide 1.5 L/min, oxygen 1.5 L/min, and halothane 1%, a leak in the oxygen flowmeter will most likely be detected by the

Pulmonary artery diastolic pressure is an unreliable indicator of left ventricular end-diastolic pressure in patients with

The lungs of a 7-kg infant are being ventilated with a volume-cycled ventilator at a rate of 20/min. The anesthetic circuit has a compressible volume of 5 ml/cm H2O, and the peak inspiratory pressure is 20 cmH2O. To achieve adequate ventilation, the ventilator tidal volume should be set at

During steady-state intraoperative controlled mechanical ventilation, exhaled tidal volume will be increased by

Proper handling of oxygen cylinders includes

One full E-cylinder of oxygen at 20°C can deliver 2 L/min of oxygen for at most

Reduction of fire hazards during laser surgery of the airway is best accomplished by use of

During induction of general anesthesia in a patient with a supraglottic tumor, both intubation and subsequent ventilation via a face mask are impossible. A cricothyroidotomy is performed with a 16-gauge intravenous catheter. Which of the following statements is true?

A 27-month-old, 14-kg infant with intestinal obstruction is anesthetized with nitrous oxide at 1 L/min, oxygen at 0.4 L/min, and halothane at 0.8% using a Bain circuit. Ventilation is controlled at a rate of 30/min. The child's temperature is 39°C, and the PaCO2 is 65 mmHg. Which of the following is most likely?

A healthy, 18-year-old, 65-kg woman undergoing diagnostic laparoscopy is being monitored with a properly functioning and calibrated capnograph. The end-tidal carbon dioxide concentration is 6%, and the inspired carbon dioxide concentration is 1%. This may be caused by each of the following EXCEPT

Compared with a semiclosed circle system, a closed system

The pin index system

The fail-safe mechanism on an anesthesia machine is activated by

Leakage current and microshock hazards are eliminated by

Recommendations for maximal allowable trace anesthesia gases are based on

Which of the following statements concerning monitoring of neuromuscular function during general anesthesia is true?

Which of the following decreases dead space in an anesthetic circle system?

After removing the electrocautery pad from the thigh, a burn is noted at that site. Which of the following most likely contributed to this injury?

A Fluotec vaporizer is set to administer halothane 4% using a fresh gas flow of 4 L/min. If the diluent gas flow is increased to 8 L/min, and at the same time the room temperature increases from 20 to 25°C, the approximate concentration of halothane delivered to the patient would be

Which of the following statements concerning use of a Bain circuit is true?

Measurement of blood pressure with a Doppler device involves

The vapor pressure of a volatile anesthetic depends on

Which of the following statements concerning absorption of carbon dioxide by soda lime in an anesthetic circuit is correct?

The risk for airway fire during laser resection of a tracheal tumor is decreased by use of

Cardiac output measured by thermodilution with a pulmonary artery catheter most accurately reflects systemic blood flow in a patient with

During general anesthesia using a modern anesthesia machine, a patient's spontaneous ventilation is manually assisted with a fresh gas flow of 5 L/min. A sudden malfunction of the pressure-relief (pop-off) valve of the circle absorption system occurs, and the valve cannot be opened. The most appropriate next step is to

Which of the following vaporizer filling errors is most likely to result in inadvertent anesthetic overdose?

After inflation of both the tracheal and endobronchial cuffs of a left-sided double-lumen tube, the following are noted on auscultation of the chest: Left lumen clamped --> Breath sounds absent bilaterally; Right lumen clamped --> Breath sounds present on left only; Both lumens open --> Breath sounds present on left only. The most appropriate action is to

While checking an anesthesia machine, opening the oxygen flow-control valve yields no oxygen flow, although the wall-mounted oxygen pipeline supply gauge reads 50 psig. Opening the backup oxygen cylinder results in normal oxygen flow. The most likely cause is

Which of the following is indicated by an alarm condition in the line-isolation monitor?

Arterial pressure in the radial artery is 155/70 mmHg measured by a correctly calibrated catheter-transducer system. At the same time, aortic pressure is 140/75 mmHg using a high-fidelity catheter tip transducer. The most likely cause of this discrepancy is

Which of the following is the most appropriate action after an anesthetic vaporizer is tipped?

During laser excision of vocal cord polyps in a 5-year-old boy, dark smoke suddenly appears in the surgical field. The trachea is intubated and anesthesia is being maintained with halothane, nitrous oxide, and oxygen. The most appropriate initial step is to

Proper zeroing of an arterial pressure transducer attached to a supine anesthetized patient is best accomplished by

During extracorporeal shock wave lithotripsy, the shock wave should be synchronized with

Equipment that is attached to a patient should have leakage current no greater than

The gauge pressure on a cylinder of nitrous oxide

Which of the following is most effective in decontaminating an anesthesia machine that was splattered with HIV-contaminated blood?

A burn is found at the site of the electrocautery pad. Which of the following is most likely?

Which property of oxygen is detected by the fail-safe device on the anesthesia machine?

Which of the following is most effective in preventing intraoperative hypothermia in adults?

The accuracy of oxyhemoglobin saturation determined by digital pulse oximetry is affected significantly by each of the following EXCEPT

If the low-pressure alarm of an anesthesia circuit is broken, which of the following monitors will provide the earliest indication of a disconnected ventilator hose?

An arterial blood sample is obtained from a patient undergoing hypothermic cardiopulmonary bypass at 28 C. Analysis at 37 C shows a pH of 7.40 and PaCO2 of 40 mmHg. Which of the following values are most likely if the analysis is corrected to 28 C?

During direct intra-arterial measurement of blood pressure

A child undergoing general anesthesia is breathing spontaneously using the Jackson-Rees modification of the Ayres T-piece. Respiratory rate is 20/min and tidal volume is 75 ml. What is the minimum fresh gas flow required to prevent rebreathing?

During induction of anesthesia, a patient is breathing isoflurane from a semiclosed circle absorber system. The temperature-compensated vaporizer is set to deliver isoflurane 1.5%. Which of the following will result in the lowest inspired concentration of isoflurane?

An air/oxygen blender with E-size cylinders is supplying gas to a Mapleson D circuit being used to ventilate a neonate during transport. The air tank is full (psi= 1900/625 L) and flow is 4 L/min. The oxygen tank flow is 5 L/min and the pressure gauge indicates 500 psi. If the flow rates remain unchanged, which of the following statements is correct?

During anesthesia using the Bain circuit

Intraoperatively, the occurrence of prominent "a" waves on the central venous pressure waveform can be explained by each of the following EXCEPT

When using a Venturi face mask with a reservoir bag

With respect to mechanical ventilation, which of the following statements concerning the portion of tidal volume known as compression volume is true?

A waste-gas scavenger has an active disposal system. Which of the following safety features is necessary to prevent removal of excess gas from the breathing circuit?

During attempted cannulation of the right internal jugular vein, the exploring needle goes lateral to the vein. Which of the following structures is most likely to be encountered?

A 32-year-old woman is anesthetized for suboccipital craniotomy. During positioning, the capnograph shows an abrupt decrease in the slope of the expiratory upstroke. Which of the following is the most likely cause?

During laser excision of a vocal cord polyp, the tracheal tube ignites. Which of the following is the most appropriate next step?

A 55-year-old man is undergoing craniotomy in the sitting position. Mean arterial pressure is 75 mmHg; arterial blood gas values are PaCO2 41 mmHg and pH 7.37. End-tidal CO2 is 7 mmHg. Which of the following is the most likely cause of the increased PaCO2 to PetCO2 gradient?

Which of the following is characteristic of soda lime and Baralyme carbon dioxide absorption canisters used in circle systems?

A 68-year-old patient is undergoing total hip replacement during general anesthesia using positive pressure ventilation and neuromuscular blockade. Intraoperative monitoring shows a gradual decrease in end-tidal CO2, an increase in exhaled tidal volume, and an increase in measured FiO2. Which of the following is the most likely cause of these changes?

When inspired anesthetic gases are humidified

Which of the following malfunctions causes the line isolation monitor to alarm?

Which of the following combinations of anesthetic and incorrect vaporizer results in the smallest error in delivered concentration?

Which of the following is the greatest disadvantage of pressure-cycled ventilation?

The jet ventilation technique using an injector during laryngobronchoscopy relies on

Which of the following decreases the risk for burns during electrocauterization?

Two opened oxygen cylinders, one full and one empty, are attached to an anesthesia machine. The check valve to the empty cylinder fails. This is expected to result in

Which of the following statements concerning anesthesia machine flowmeters is true?

Which of the following statements concerning the check valve of the common gas outlet on an anesthesia gas machine is true?

Which of the following is the most important function of temperature compensation in anesthetic vaporizers?

A neurologically intact 48-year-old woman is scheduled for removal of a parietal lobe arteriovenous malformation. The relative risk for complete resection is to be determined by a test occlusion of the feeding artery. Which of the following intraoperative monitoring techniques is most appropriate for this test?

In a normally functioning circle anesthesia system, if the length of the inspiratory and expiratory hose is doubled, the mechanical dead space will be

A healthy patient is receiving general endotracheal anesthesia with nitrous oxide 4 L/min, oxygen 2 L/min, and isoflurane 1% with spontaneous ventilation. The inspiratory breathing hose becomes disconnected from the inspiratory valve. The earliest alarm will be produced by

Desflurane at a stable alveolar concentration of 7%

The flow proportioning system on an anesthesia machine

During general anesthesia administered through a circle system, the soda lime absorbant is exhausted. No fresh soda lime is available for use. Which of the following is the most appropriate next step to prevent hypercapnia in this patient?

An unconscious adult patient is being ventilated through an esophageal obturator airway (EOA) in the emergency department. In the absence of cervical spine injury, which of the following is appropriate?

Which of the following detects the smallest volume of venous air embolization?

An anesthesia machine is set to deliver oxygen 2 L/min, nitrous oxide 2 L/min, and sevoflurane. After 30 minutes of stable anesthesia, which of the following, is the most likely cause of a decrease in the oxygen analyzer reading from 50% to 30%?

Desflurane is delivered using a vaporizer that contains internal heaters because

During laser microsurgery of the larynx using an endotracheal tube, a fire occurs in the airway. Which of the following is the most appropriate initial management?

Pulse oximetry accurately reflects SaO2 in which of the following situations?

Which of the following neurophysiologic monitoring modalities is LEAST affected by administration of volatile anesthetic agents?

An otherwise healthy 20-year-old man undergoes laser surgery for vocal cord polyp removal. During jet ventilation with 100% oxygen, arterial blood gas analysis shows PaO2 90 mmHg, PaCO2 40 mmHg, and pH 7.40. Which of the following is the most likely explanation?

A 30-year-old man who is undergoing laparotomy and resection of a large kidney tumor has a decrease in SpO2 from 100% to 92% and an increase in peak airway pressure from 20 to 35 cm H2O. Plateau pressure is unchanged at 18 cm H2O. Which of the following is the most likely cause?

The two E oxygen cylinders on an anesthesia machine have pressure readings of 1100 psi each. At an oxygen flow of 3 L/min, there will be sufficient oxygen for approximately

Pulmonary artery occlusion pressure

A 30-kg patient with asthma is receiving general anesthesia and being mechanically ventilated with a measured tidal volume of 300 mL. Increasing the fresh gas flow from 3 L/min to 9 L/min without changing the ventilatory rate or I:E ratio will result in

After the bronchial and tracheal cuffs of a right endobronchial tube are inflated, ventilation through the tracheal lumen is not possible. This finding is most consistent with

While delivering nitrous oxide 1.5 L/min, oxygen 1.5 L/min, and sevoflurane 2%, a leak in the oxygen flowmeter would most likely be detected by the

An sevoflurane vaporizer is filled with isoflurane and the vaporizer dial is set at 1%. Which of the following will occur?

Which Mapleson breathing circuit permits the LEAST amount of fresh gas inflow to prevent rebreathing during spontaneous ventilation?

In this diagram of a circle system, an increase in dead space is most likely to result from placement of the pressure relief valve at location

To detect the delivery of hypoxic gas mixture, the optimal location for an oxygen analyzer in this circle is

A 2-year-old child has cardiac arrest during an inguinal herniorrhaphy under general anesthesia administered during a Jackson-Rees system. The graph shows end-tidal PCO2 monitored from the tip of the endotracheal tube during cardiopulmonary resuscitation; minute ventilation is unchanged. Which of the following is the most likely cause of the change beginning at the arrow?

The most likely cause of this capnographic tracing obtained just after laryngoscopy and intubation is

A multi-orifices right heart catheter is being positioned by EKG control prior to sitting craniotomy. The EKG tracing is obtained between the distal tip of the catheter and the right arm lead. The most appropriate next step is to

The capnographic tracing is from a 2-month-old infant anesthetized using a pediatric circle system and mask at a fresh gas flow of 4 L/min. The sampling port is in the elbow connector. This tracing indicates

In the event of a leak in the air flowmeter, which flowmeter arrangement produces the lowest risk of delivering hypoxic gas mixtures?

The trend plot shows end-tidal gases measured during a radical neck dissection. The event occurring at A is most likely

A normal adult is receiving general anesthesia via a standard circle system and controlled ventilation. Mass spectrometer data are shown. Which event is most compatible with these data?

The tracing shown is from a femoral artery catheter. Which of the following is the most likely explanation?

To detect the delivery of a hypoxic gas mixture, the optimal location for an oxygen analyzer in this circle is

Which Mapleson breathing circuit shown in the illustration permits the LEAST amount of fresh gas inflow to prevent rebreathing during spontaneous ventilation?