For confirming endotracheal tube placement following intubation of a patient in cardiac arrest, which ONE of the following methods is the most reliable?
Answer: A: The detection of ETCO2 is widely accepted as the most reliable method for verifying tracheal intubation. However, the efficacy of this method can be hindered in situations where insufficient CO2 is exhaled because of reduced pulmonary blood flow, such as during cardiac arrest, which has led to the assumption that the oesophageal detector device (EDD) might be more accurate in cardiac arrest situations. However, conflicting results have been reported regarding the accuracy of EDD in emergency situations, and even less evidence is available for patients with cardiac arrest. Studies of colorimetric ETCO2 detectors, non-waveform ETCO2 capnometers and EDD showed that the accuracy of these devices is similar to the accuracy of clinical assessment for confirming the tracheal position of a tracheal tube in those experiencing cardiac arrest. Two studies of waveform capnography to verify endotracheal tube placement in those experiencing cardiac arrest after intubation demonstrated 100% sensitivity and specificity in identifying correct tracheal tube placement. These studies were reviewed by ILCOR in 2010, which has led to the recommendation that ETCO2 monitoring with waveform capnography is the most sensitive and specific way to confirm and continuously monitor the position of a tracheal tube in a patient in cardiac arrest and should supplement clinical assessment (visualization of the tube through the cords and auscultation).
Regarding the use of bilevel positive airway pressure (BiPAP) in acute hypercapnic respiratory failure in chronic obstructive pulmonary disease (COPD), adjustment of which ONE of the following parameters will most effectively reduce PCO2 levels?
Answer: B: Increasing the IPAP increases the pressure support (IPAP–EPAP) provided by the ventilator. Pressure support augments the tidal volume during a spontaneous breath and reduces the work of breathing, resulting in increased alveolar ventilation, and therefore reduced CO2 . Increasing the PEEP (also known as EPAP) alone will improve oxygenation due to alveolar recruitment and reduction of intrapulmonary shunting but not ventilation. Increasing PEEP and IPAP proportionally may improve oxygenation but not ventilation because the pressure support remains unchanged. During S/T mode, the timed ventilations are merely a back-up rate should spontaneous respirations cease and therefore do not influence gas exchange.
Regarding non-invasive ventilation (NIV) in acute cardiogenic pulmonary oedema, which ONE of the following is TRUE?
Answer: D: There is high-quality evidence that NIV decreases the need for intubation and induces a more rapid improvement in respiratory distress and metabolic disturbance than does standard oxygen therapy in patients with acute cardiogenic pulmonary oedema. However, there is conflicting evidence regarding the impact of NIV on mortality, with most studies suggesting that it has no effect on short-term mortality. The optimal mode of NIV (BiPAP versus CPAP) is yet to be established. NIV improves cardiogenic pulmonary oedema by establishing a positive intrathoracic pressure and reducing LV afterload. In patients with acute pulmonary oedema, the application of PEEP can improve haemodynamics by reducing preload and afterload, as positive pressure reduces venous return to the left ventricle. In patients with normal LV function, and hence those sensitive to changes in preload, a subsequent reduction in cardiac output may occur. However, in patients with impaired LV function, a reduction in preload actually improves cardiac function. The optimal PEEP remains to be resolved, although 10 cm H2O appears to be safe and effective in the majority of patients. The addition of a differential inspiratory pressure (BiPAP) appears to be as effective as CPAP but does not appear to provide an additional outcome benefit and some concerns have been raised that BiPAP may increase the rate of myocardial infarction.
Regarding NIV in COPD, which ONE of the following is FALSE?
Answer: D: BiPAP is particularly indicated in patients with an acute exacerbation of COPD in whom a respiratory acidosis (pH < 7.35) persists despite maximum medical treatment and controlled oxygen therapy. The application of CPAP/PEEP promotes the ability to counteract intrinsic or dynamic PEEP, reducing lung hyperinflation and assisting in passive exhalation. Although no difference in hospital mortality has been demonstrated, patients have a survival advantage that becomes apparent after discharge, at 3 months and 1 year. It is widely accepted to maintain saturation between 88 and 92%. The British Thoracic Society (BTS) recommends even lower levels of 85–90%.
Regarding severe life-threatening asthma, which ONE of the following is the most appropriate indication for intubation?
Answer: D: The decision to intubate in acute severe asthma is a clinical decision and should not be based solely on blood gases. Markers of deterioration include rising PaCO2 levels, exhaustion, mental status depression, refractory hypoxaemia and haemodynamic instability. Many patients will present with hypercapnia or hypoxia and will rapidly improve with medical intervention and not require intubation.
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