Multiple Choice Questions MCQ

Question 6# Print Question

Regarding mechanical ventilation in the acute asthmatic, which ONE of the following is TRUE?

A. Pressure-controlled ventilation is preferred over volume-controlled to prevent lung damage due to hyperinflation

B. Peak inspiratory pressures (P_peak) should be limited to ≤25 cm H₂O

C. Plateau pressures (P_plat) and not P_peak is associated with ventilator induced lung injury (VILI)

D. The aim of ventilation is to maintain oxygenation and correct the CO₂ to normal levels

Answer: C: The major concern in commencing mechanical ventilation in acute severe asthma is the risk of worsening lung hyperinflation due to gas trapping, with an increased risk of barotrauma, and inducing or aggravating haemodynamic instability. Therefore, the focus of mechanical ventilation has moved away from normalising blood gas values to where the primary goal now is to avoid excessive airway pressure and minimising lung hyperinflation, while maintaining adequate gas exchange (see Table below).

ACCEPTABLE INITIAL VENTILATOR SETTINGS IN THE INTUBATED ASTHMATIC:

As a result, mechanical ventilation strategies are aimed at reducing the likelihood that this complication will occur. To achieve this goal it is often necessary to hypoventilate the patient and therefore to tolerate hypercapnoea, a strategy termed ‘controlled hypoventilation’ or ‘permissive hypercapnoea’.

P_peak is not a reflection of what is happening at the alveolar level. Subsequently, it is not that useful for assessing lung hyperinflation in asthmatic patients because it depends strongly on the airway resistance and inspiratory flow setting. Higher P_peak than usual may be necessary to prevent delivery of inappropriately small tidal volumes. In contrast, P_plat is an estimate of the average alveolar pressure at the end of inspiration and is directly proportional to the degree of hyperinflation. This should be maintained at <25–30 cm H₂O in asthma. P_plat is associated with VILI, not peak inspiratory pressure (see Table above).

Both volume- and pressure-controlled ventilation can be used in ventilating asthmatics, but volumecontrolled ventilation is usually preferred. Pressurecontrolled ventilation entails the risk of variable tidal volume (due to fluctuating high airway resistance and intrinsic PEEP), with sometimes unacceptably low alveolar ventilation.

References:

Oddo M, Feihl F, Schaller M, et al. Management of mechanical ventilation in acute severe asthma: practical aspects. Intensive Care Med 2006;32:501–10.
Stather DR, Stewart TE. Clinical review: mechanical ventilation in severe asthma. Critical Care Medicine 2005;9:581–7.
Marik PE,Varon J, Fromm Jr R. The management of acute severe asthma. The Journal of Emergency Medicine 2002;23(3):257–68.

Question 7# Regarding providing ventilatory support in patients with an acute lung injury (ALI) or the adult respiratory distress syndrome (ARDS), which ONE of the following is TRUE?
A. NIV has a high success rate and is therefore recommended over invasive ventilation
B. The FiO₂ should be weaned to maintain a SaO₂ of at least 95%
C. The respiratory rate should be increased to compensate for lower tidal volumes to maintain a normal PaCO₂ and pH
D. Plateau pressures should be kept <30 cm H₂O and may require reducing tidal volumes as low as 4 mL/kg
Answer: D: The role of NIV in ARDS is still uncertain and not routinely recommended, although it may be considered in certain circumstances. Recommendations for ventilation according to the ARDS Network are: tidal volumes (TV) 6–8 mL/kg ideal body weight Plateau pressures <30 cm H₂O: may require reducing TV as low as 4 mL/kg Wean FiO₂ to maintain a SaO₂ 88–95% Strategic use of PEEP to permit lower FiO₂ and reduce risk of oxygen toxicity Rate 20–25 (<30) per minute Permissive hypercapnia (pH should be maintained >7.25) References: The Acute Respiratory Distress Syndrome Network. Ventilation with lower tidal volumes as compared with traditional tidal volumes for acute lung injury and the acute respiratory distress syndrome. N Engl J Med 2000;342:1301–8. Berston AD. The acute respiratory distress syndrome (ARDS). In: Berston AD, Soni N, editors. Oh’s intensive care manual. 6th ed. Philadelphia: Elsevier; 2009. p. 375–85.

Question 8# The International Liaison Committee on Resuscitation (ILCOR) has published new recommendations in 2010 on CPR in adult cardiac arrest. Regarding this, which ONE of the following statements is TRUE?
A. In an unwitnessed cardiac arrest the patient should receive 2 minutes of CPR before defibrillation is attempted
B. Continuous ETCO₂ monitoring can be used to indicate the quality of CPR
C. Effective external cardiac compressions provide an output of about 40–50% of the pre-arrest value
D. The inspired concentration of oxygen should be reduced to 21–60% as hyperoxaemia is associated with worse neurological outcome
Answer: B: Continuous ETCO₂ monitoring can be used to indicate the quality of CPR, although an optimal target for ETCO₂ during CPR has not been established. An ETCO₂ < 10 mmHg is associated with failure to achieve ROSC and may indicate that the quality of chest compressions should be improved. Effective external cardiac compressions provide an output of 20–30% of the pre-arrest value. A 2-minute period of CPR before defibrillation has previously been recommended in patients with OHCA. The 2010 ILCOR guidelines recommend that good-quality CPR should be provided while a defibrillator is retrieved, applied and charged, but the guidelines no longer recommend routine delivery of a specified period of CPR before rhythm analysis and a shock. There is insufficient evidence to support or refute the use of a titrated oxygen concentration or constant 21% oxygen (room air) when compared with 100% oxygen during adult cardiac arrest. In the absence of any other data there is no reason to change the current treatment algorithm. However, hyperoxemia may lead to potential harm in patients with ROSC and titrating the inspired oxygen concentration to achieve saturation of 94–98% is recommended in the post-resuscitation phase. Reference: Nolan JP, Hazinski MF, Billi JE, et al. 2010 International consensus on cardiopulmonary resuscitation and emergency care science with treatment recommendations. Resuscitation 2010;81(1) suppl1:e1–e332.

Question 9# Regarding CPR in adult cardiac arrest for advanced life support providers, which ONE of the following is TRUE?
A. The chest compression ratio is 30:2 if one rescuer present and 15:2 if more than one rescuer
B. The internipple line is a reliable landmark for hand placement during chest compressions
C. Chest compression depths should be at least one half of the depth of the adult chest
D. When using an advanced airway, ventilation should be delivered during the relaxation phase of a chest compression
Answer: D: When an advanced airway is established, compressions do not have to be paused in order to give ventilation, but ventilations should be timed with compressions and delivered during the relaxation phase of compression without any pause. Ventilations of 6–10 per minute are recommended and can be achieved by giving a timed ventilation after every 15 compressions. The 2010 ILCOR and ARC guidelines recommend a universal compression ratio of 30:2 (30 compressions followed by two ventilations) regardless of the number of rescuers present. The desired compression point for CPR in adults is over the lower half of the sternum. This location can simply be taught by saying, ‘Place the heel of the hand in the centre of the chest’. The use of the internipple line as a landmark for hand placement is not reliable. The depth of compressions should be at least one-third of the depth of the chest or at least 5 cm. References: Nolan JP, Hazinski MF, Billi JE, et al. 2010 International consensus on cardiopulmonary resuscitation and emergency care science with treatment recommendations. Resuscitation 2010;81(1) suppl1:e1–e332. Australian Resuscitation Council, New Zealand Resuscitation Council. Cardiopulmonary resuscitation for advanced life support providers. ARC and NZRC guideline 2010. Emerg Med Austr 2011;23(3):286–91.

Question 10# Regarding defibrillation with a manual biphasic defibrillator using pads in patients with cardiac arrest, which ONE of the following statements is TRUE?
A. For rescuer safety, chest compressions should briefly be stopped while charging the defibrillator in preparation for delivery of a shock
B. After delivery of a shock, one should check for the presence or absence of a pulse before restarting chest compressions
C. Three stacked shocks should initially be delivered in all patients suffering from a ventricular fibrillation (VF) arrest
D. The default energy level for adults should be set at 200 J for all shocks
Answer: D: The default energy level for adults using a biphasic defibrillator should be set at 200 J for all shocks. Other energy levels may be used, providing there is relevant clinical data for a specific defibrillator that suggests that an alternative energy level provides adequate shock success. ILCOR and the ARC now recommend that chest compressions be continued while the defibrillator is charged if using pads. This approach appears to be safe and it minimizes interruption to chest compressions. CPR should be restarted immediately after delivering a shock, irrespective of apparent electrical success. A pulse check should not be performed. The likelihood of developing a rhythm associated with an output is extremely small in the first minute after a shock has been delivered. It is now recommended that a single shock strategy be used in patients with VF/VT arrest with immediate resumption of chest compressions after the shock. Studies have shown no benefit from a three-stack shock protocol compared with a one-shock protocol. Additionally, there is significantly more hands-off time. However, a sequence of up to 3 stacked shocks can be considered in patients with a perfusing rhythm who develop a shockable rhythm where the setting is: A witnessed and monitored setting The defibrillator is immediately available (e.g. first shock able to be delivered within 20 seconds The time required for rhythm recognition and for recharging the defibrillator is short (i.e. <10 seconds) References: Australian Resuscitation Council, New Zealand Resuscitation Council. Cardiopulmonary resuscitation for advanced life support providers. ARC and NZRC guideline 2010. Emerg Med Austr 2011;23(3):286–91. Sunde K, Jacobs I, Deakin CD, et al. Part 6: Defibrillation. 2010 International consensus on cardiopulmonary resuscitation and emergency care science with treatment recommendations. Resuscitation 2010;81(1) suppl1:e71–e85. Australian Resuscitation Council, New Zealand Resuscitation Council. Electrical therapy for adult advanced life support. ARC and NZRC guideline 2010. Emerg Med Austr 2011;23(3):277–81.

Question 6# Regarding mechanical ventilation in the acute asthmatic, which ONE of the following is TRUE?
A. Pressure-controlled ventilation is preferred over volume-controlled to prevent lung damage due to hyperinflation
B. Peak inspiratory pressures (P_peak) should be limited to ≤25 cm H₂O
C. Plateau pressures (P_plat) and not P_peak is associated with ventilator induced lung injury (VILI)
D. The aim of ventilation is to maintain oxygenation and correct the CO₂ to normal levels
Answer: C: The major concern in commencing mechanical ventilation in acute severe asthma is the risk of worsening lung hyperinflation due to gas trapping, with an increased risk of barotrauma, and inducing or aggravating haemodynamic instability. Therefore, the focus of mechanical ventilation has moved away from normalising blood gas values to where the primary goal now is to avoid excessive airway pressure and minimising lung hyperinflation, while maintaining adequate gas exchange (see Table below). ACCEPTABLE INITIAL VENTILATOR SETTINGS IN THE INTUBATED ASTHMATIC: As a result, mechanical ventilation strategies are aimed at reducing the likelihood that this complication will occur. To achieve this goal it is often necessary to hypoventilate the patient and therefore to tolerate hypercapnoea, a strategy termed ‘controlled hypoventilation’ or ‘permissive hypercapnoea’. P_peak is not a reflection of what is happening at the alveolar level. Subsequently, it is not that useful for assessing lung hyperinflation in asthmatic patients because it depends strongly on the airway resistance and inspiratory flow setting. Higher P_peak than usual may be necessary to prevent delivery of inappropriately small tidal volumes. In contrast, P_plat is an estimate of the average alveolar pressure at the end of inspiration and is directly proportional to the degree of hyperinflation. This should be maintained at <25–30 cm H₂O in asthma. P_plat is associated with VILI, not peak inspiratory pressure (see Table above). Both volume- and pressure-controlled ventilation can be used in ventilating asthmatics, but volumecontrolled ventilation is usually preferred. Pressurecontrolled ventilation entails the risk of variable tidal volume (due to fluctuating high airway resistance and intrinsic PEEP), with sometimes unacceptably low alveolar ventilation. References: Oddo M, Feihl F, Schaller M, et al. Management of mechanical ventilation in acute severe asthma: practical aspects. Intensive Care Med 2006;32:501–10. Stather DR, Stewart TE. Clinical review: mechanical ventilation in severe asthma. Critical Care Medicine 2005;9:581–7. Marik PE,Varon J, Fromm Jr R. The management of acute severe asthma. The Journal of Emergency Medicine 2002;23(3):257–68.

Your-Doctor Multiple Choice Questions (MCQ)

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Multiple Choice Questions (MCQ)