Q). For
confirming endotracheal tube placement following intubation of a patient in
cardiac arrest, which ONE of the following methods is the most reliable?
A. Waveform
capnography
B. Calorimetric
end-tidal carbon dioxide (ETCO2)
C. Oesophageal
detector device
D. Pulse
oximetry
1. 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 (visualisation of the tube through the cords and
auscultation)
Q). 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?
A. Increase
positive end-expiratory pressure (PEEP)
B. Increase
inspiratory positive airway pressure (IPAP)
C. Increase
PEEP and IPAP proportionally
D. Decrease
the timed ventilations when in spontaneous/timed (S/T) mode
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
Q). Regarding non-invasive ventilation (NIV) in acute cardiogenic
pulmonary oedema, which ONE of the following is TRUE?
A. BiPAP
has been shown to be superior to continuous positive airway pressure (CPAP)
B. PEEP
should never be increased above 5 cm H2O
C. It
has a proven short-term mortality benefit
D. It
improves cardiac output
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.
Q).Regarding severe life-threatening asthma, which ONE of the
following is the most appropriate indication for intubation?
A. PCO2
> 70 mmHg
B. pH
< 7.35
C. SaO2
85%
D. Respiratory
exhaustion
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.
