Question 1

Which of the following would decrease PaCO₂ when ventilating a patient using intermittent mandatory ventilation with pressure support?

Accepted Answer

The PaCO₂ can be decreased by increasing tidal volume, increasing PSV for spontaneous breaths, or increasing the machine rate.

Question 2

A physician orders intubation and mechanical ventilation in the synchronized intermittent mandatory ventilation mode for a 160-lb adult man with a history of chronic obstructive pulmonary disease. Which of the following settings would you recommend? Rate V_T

Accepted Answer

The recommended initial ventilator settings for an adult typically include a tidal volume of 6-8 ml/kg of ideal body weight and a respiratory rate of 12-20 breaths per minute. For a 160-lb (approximately 73 kg) adult, a tidal volume of 500 ml (close to 6-8 ml/kg) and a rate of 12 breaths/min falls within these guidelines, making it a suitable choice for someone with chronic obstructive pulmonary disease (COPD) to ensure adequate ventilation without causing overdistension or rapid breathing that could lead to increased work of breathing or air trapping.

Question 3

A physician orders intubation and mechanical ventilation in volume-controlled ventilation mode for a 170-lb adult man with neuromuscular disease. Which of the following initial settings would you recommend? Rate V_T

Accepted Answer

The initial settings for mechanical ventilation in an adult should aim for a tidal volume of 6-8 ml/kg of ideal body weight. For a 170-lb (approximately 77 kg) adult, a tidal volume around 462-616 ml is appropriate. A rate of 14 breaths/min with a tidal volume of 540 ml (which falls within the recommended range) is a reasonable starting point, ensuring adequate ventilation without risking lung injury from overdistension.

Question 4

Patient's RR is 12 breaths/min, PaCO₂ is 60 mm Hg. If a PaCO₂ of 40 were desired, the RR be set at what value?

Accepted Answer

This formula predicts what RR adjustment effects will be on PaCO₂, with no change in VCO₂ or V_Dphys:

Question 5

In what scenario is pressure-controlled ventilation (PCV) most often used?

Accepted Answer

PCV may be used immediately upon ventilator initiation when limiting the plateau pressure is a concern and in the care of patients expected to need prolonged inspiration or an increased 1:E ratio (1:1, 1.5:1, 2:1). These patients typically have acute lung injury or ARDS.

Question 6

What phrase is used to describe the situation where the patient with acute lung injury is ventilated with a smaller tidal volume and the PaCO₂ is allowed to increase above normal range to avoid additional lung injury?

Accepted Answer

This technique is known as permissive hypercapnia.

Question 7

On a ventilator that has separate rate and minute ventilation (V_E) controls, the rate is set at 13/min and the V_E at 11 L/min. Approximately what V_T is the patient receiving?

Accepted Answer

Tidal volume (V_T) and rate (f) determine minute ventilation.

Question 8

Which of the following statements is false regarding ventilation in the assist-control mode?

Accepted Answer

With assist-control mode, every breath is supported by the ventilator. Breaths are patient- or time-triggered to inspiration and may be volume or pressure limited. Inspiration may be volume, pressure, or time cycled to the expiratory phase. Assist-control ventilation typically is delivered as volume-controlled (VC) continuous mandatory ventilation. Suggested initial settings for assist-control volume ventilation in the care of adults are listed in Box 48-4. Advantages of assist-control volume ventilation include the assurance that a minimum, safe level of ventilation is achieved. Every breath is a volume breath, yet the patient can set his or her own breathing rate. In the event of sedation or apnea, a minimum, safe level of ventilation is guaranteed by the selection of an appropriate backup rate, usually approximately 2 to 4 breaths/min below the patient's assist rate, but not less than the rate necessary to provide a minimum safe level of ventilation (e.g., a backup rate of at least 8 to 10 breaths/min, depending on tidal volume set). Because assist-control ventilation usually provides full ventilatory support, it may result in a lower work of breathing than partial support modes.

Question 9

A physician orders intubation and mechanical ventilation in the continuous mandatory ventilation assist-control mode for a 125-lb adult woman with normal lungs. Which of the following initial settings would you recommend? Rate V_T

Accepted Answer

For a 125-lb adult woman with normal lungs, initial ventilator settings should be a respiratory rate of 12-16 breaths/min and a tidal volume of 6-8 mL/kg, which equates to 340-450 mL. Option B meets these criteria with a rate of 14 breaths/min and a tidal volume of 400 mL.

Question 10

Air trapping is a major concern in patients with what diagnosis when using the assist-control mode?

Accepted Answer

Patients with COPD are at special risk of air trapping in the assist-control mode, especially if they attempt to breathe at an increased rate.

Question 11

A ventilator has separate rate and V_T controls. If you set a V_T of 650 ml and a respiratory rate of 12/min in the continuous mandatory ventilation mode, what will the minute ventilation be?

Accepted Answer

Tidal volume (V_T) and rate (f) determine minute ventilation (E).

Question 12

Which of the following are used as alternative lung protective strategies in patients with ARDS?
1) Prone positioning
2) ECMO
3) High-frequency ventilation
4) Pressure support ventilation

Accepted Answer

Prone positioning, ECMO, and high-frequency ventilation are all alternative lung protective strategies commonly used in patients with ARDS. Pressure support ventilation, however, is not typically used as a lung protective strategy in ARDS.

Question 13

Which of the following statements is false regarding pressure-supported ventilation?

Accepted Answer

Pressure support ventilation assists the patient's spontaneous inspiration with a clinician-selected level of positive pressure. Pressure support is patient triggered, pressure limited, and flow cycled. Pressure support ventilation can reduce work of breathing and may improve patient-ventilator synchrony and comfort while limiting the pressure applied to the airway. Pressure support to overcome WOB_I should be considered in the care of all spontaneously breathing patients in the IMV mode. IMV, as originally developed, allowed spontaneous breathing interspersed with volume-limited, patient- or time-triggered machine breaths. The WOB_I during spontaneous breathing due to slow demand flow systems, ventilator circuitry, and the artificial airway prompted the addition of pressure support. Today it is suggested that all spontaneous breaths during IMV be supported with an appropriate level of pressure support, usually in the range of 5 to 10 cm H₂O, to overcome the WOB_I.

Question 14

For adolescents in the 8- to 16-year-old age range, which of the following ranges of ventilator setting would you initially recommend? Rate V_T

Accepted Answer

Recommended initial tidal volume and frequency for various patient types are described in Table 48-4.

Question 15

Which of the following trigger levels is appropriate when setting a ventilator for pressure triggering?

Accepted Answer

With pressure triggering, the range is generally -0.5 to -1.5 cm H₂O.

Question 16

A ventilator has separate rate and minute ventilation controls. A physician orders continuous mandatory ventilation with a V_T of 550 ml at a respiratory rate of 12/min. What minute ventilation would you set on this ventilator?

Accepted Answer

Tidal volume (V_T) and rate (f) determine minute ventilation.

Question 17

A physician orders intubation and mechanical ventilation in the continuous mandatory ventilation mode for a 200-lb predicted body weight (PBW) adult man with acute asthma exacerbation. Which of the following initial ventilator settings would you recommend? Rate V_T

Accepted Answer

For a 200-lb predicted body weight (PBW) adult man, the appropriate tidal volume (VT) is calculated based on the ideal body weight, which is roughly 6-8 ml/kg of ideal body weight. For a man, ideal body weight is estimated as 50 kg + 2.3 kg for each inch over 5 feet. Assuming a 200-lb man is approximately 90.7 kg (200 lbs / 2.2 lbs/kg), his height and corresponding ideal body weight would need to be estimated to calculate the appropriate tidal volume. However, without specific height information, we generally aim for the lower end of the tidal volume range to minimize the risk of ventilator-induced lung injury. A tidal volume of 450 ml (choice B) is within the recommended range when considering a lower end of 6 ml/kg for a roughly estimated ideal body weight in the absence of specific height data. The rate of 11 breaths/min is reasonable for an adult with acute asthma exacerbation, aiming to avoid hyperventilation and the risk of auto-PEEP (positive end-expiratory pressure).

Question 18

On some ventilators, which of the following can occur if a trigger setting is set too sensitive on a mechanical ventilator?

Accepted Answer

If the trigger setting is too sensitive on a mechanical ventilator, it can lead to autotriggering, which means the ventilator will initiate a breath even when the patient is not trying to breathe. This can result in discrepancies between the patient's respiratory effort and the ventilator's support, leading to flow dyssynchrony, increased work of breathing, and ultimately, barotrauma if not corrected.

Question 19

Which of the following are primary goals of mechanical ventilation? 1) Adequate alveolar ventilation (V_A) 2) Maintaining adequate hemoglobin levels 3) Restoring acid-base balance 4) Maintaining adequate alveolar oxygenation

Accepted Answer

The primary goals of mechanical ventilation include maintaining adequate alveolar ventilation, restoring acid-base balance, and maintaining adequate alveolar oxygenation. Maintaining hemoglobin levels is not a primary goal of mechanical ventilation. Therefore, options A, C, and D are incorrect.

Question 20

Which of the following statements are true regarding the use of controlled ventilation?
1) May allow the muscles of breathing to rest.
2) Can use larger 1:E ratio and may improve oxygenation.
3) Requires use of paralytic agents in spontaneously breathing patients.
4) Therapist has little control of needed inspiratory flow and pressure.

Accepted Answer

1) Controlled ventilation indeed allows the muscles of breathing to rest by taking over the work of breathing, which is beneficial in cases where the patient is unable to breathe effectively on their own.2) By adjusting the inspiratory to expiratory (I:E) ratio, controlled ventilation can indeed improve oxygenation, especially in conditions like ARDS (Acute Respiratory Distress Syndrome) where prolonged inspiratory times can help improve oxygenation.3) In patients who are spontaneously breathing, the use of paralytic agents (neuromuscular blocking agents) may be required to ensure that the patient's breathing efforts are fully synchronized with the ventilator or to eliminate spontaneous breathing efforts entirely, ensuring the full benefits of controlled ventilation.

Quiz 48: Initiating and Adjusting Invasive Ventilatory Support

Which of the following would decrease PaCO2 when ventilating a patient using intermittent mandatory ventilation with pressure support?

A physician orders intubation and mechanical ventilation in the synchronized intermittent mandatory ventilation mode for a 160-lb adult man with a history of chronic obstructive pulmonary disease. Which of the following settings would you recommend? Rate VT

A physician orders intubation and mechanical ventilation in volume-controlled ventilation mode for a 170-lb adult man with neuromuscular disease. Which of the following initial settings would you recommend? Rate VT

Patient's RR is 12 breaths/min, PaCO2 is 60 mm Hg. If a PaCO2 of 40 were desired, the RR be set at what value?

In what scenario is pressure-controlled ventilation (PCV) most often used?

What phrase is used to describe the situation where the patient with acute lung injury is ventilated with a smaller tidal volume and the PaCO2 is allowed to increase above normal range to avoid additional lung injury?

On a ventilator that has separate rate and minute ventilation (VE) controls, the rate is set at 13/min and the VE at 11 L/min. Approximately what VT is the patient receiving?