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MCQs in Respiratory Critical Care

Posted by Dr KAMAL DEEP on March 19, 2015

Transpulmonary pressure (TPP) and ventilator-associated lung injury:

a At end-inspiration, the TPP is the principal force maintaining inflation.
b TPP is calculated from the alveolar pressure minus the pleural pressure.
c The use of oesophageal TPP monitoring to set positive end-expiratory pressure (PEEP), to achieve an end-expiratory TPP of 0-10cmH20, may be associated with improved outcomes in acute respiratory distress syndrome (ARDS).
d During non-invasive ventilation (NIV), TPPs may be dangerously high, despite low delivered airway pressures.
e Barotrauma is directly due to high airway pressures.

True a,b,c,d
At end-inspiration, the TPP is the principal force maintaining inflation of lung units and thus is an important factor in the genesis of ventilator-induced lung injury (VILI).
TPP is calculated from alveolar pressure minus the pleural pressure, and thus alveolar and pleural pressure differences may both play an important role in the pathophysiology of VILI.
In a study by Talmor et al, where PEEP was set to achieve an end-expiratory pressure of 0-10cmH20 and end-inspiratory TPP was limited to 25cmH20 using oesophageal TPP monitoring, a trend towards reduced 28-day mortality in ARDS was noted.
In patients receiving NIV who generate high negative pleural pressures, TPP may be extremely high despite low delivered pressures, thus increasing the risk of barotrauma.
Barotrauma occurs due to regional lung over-distension leading to lung damage, air leaks and pneumothoraces. It is not directly caused by high airway pressures. Volutrauma occurs due to high absolute lung ventilatory volumes leading to alveolar rupture and air leaks.
1. Talmor D, Sarge T, Malhotra A, et al. Mechanical ventilation guided by esophageal pressure in acute lung injury. New Engl J Med 2008; 359: 2095-104.
2. Slutsky AS, Ranieri VM. Ventilator-induced lung injury. New Engi 1 Med 2013; 369: 2126-36.

In volume-controlled ventilation
A. Tidal volume is given according to a pre-set volume target
B. If the inspiratory time is fixed, the peak and mean airway pressure is
independent of pulmonary compliance
C. If the minute volume and frequency is set, it is not possible to adjust the tidal
volume
D. If tidal volume and minute volume is set, the ventilator frequency must be set
between 10 and 20 breaths per minute

A. T
B. F
C. T
D. F

 

Regarding the Berlin definition for acute respiratory distress’syndfame (ARDS):
a The timing of ARDS must occur within 5 days of a known clinical insult and new or worsening respiratory symptoms.
b Bilateral opacities are evident on chest imaging, which are not attributable to effusions, lobar collapse or pulmonary nodules.
c The respiratory failure seen cannot be fully explained by cardiac failure or fluid overload.
d ARDS is classified into mild and severe according to the PaO2/FiO2 ratio.
e Severe ARDS is defined by a Pa02/Fi02 ratio of <150mmHg with a positive end-expiratory pressure (PEEP) >5cmH2O.

True b & c
The timing of ARDS must occur within 1 week of a known clinical insult and new or worsening respiratory symptoms.
The definition requires bilateral opacities to be evident on chest imaging — either chest X-ray or CT scan — which is not attributable to effusions, lobar collapse or pulmonary nodules.
ARDS exists where respiratory failure cannot be fully explained by cardiac failure or fluid overload. Objective assessment with ultrasound may be required to exclude hydrostatic oedema if no risk factors are present.
The Berlin definition classifies ARDS into mild, moderate and severe. This is determined by the Pa02/Fi02 ratio: mild: a Pa02/Fi02 ratio of less than 300mmHg (39.9kPa) with positive end-expiratory pressure (PEEP) or continuous positive airway pressure (CPAP) >5cmH2O (may be delivered non-invasively); moderate: a Pa02/Fi02 ratio of less than 200mmHg (26.6kPa) with PEEP >5cmH2O; severe: a
a Pa02/Fi02 ratio of less than 100mmHg with PEEP >5cmH2O.

Severe ARDS is defined as a Pa02/Fi02 ratio of less than 100mmHg (13.3kPa) with PEEP >5cmH2O.
1. The ARDS Definition Task Force. Acute respiratory distress syndrome. The Berlin definition. JAMA 2012; 307(23): 2526-33.
2. Ferguson ND, Fan E, Camporota L, etal. The Berlin definition of ARDS: an expanded rationale, justification, and supplementary material. Intensive Care Med 2012; 38: 1573-82.

Which is/are correct statements regarding the inspiratory time (Ti)
A. At the end-inspiratory time, the expiration phase always starts
B. If Ti is set by the Inspiration:Expiration ratio, the Ti is independent of
ventilator frequency
C. If Ti is directly set, the expiratory time decreases with increasing ventilator
frequency
D. Normal Ti is in the range of 3–4 seconds

A. F
B. F
C. T
D. F

 

 

Causes of right ventricle (RV) failure include:
a Acute pulmonary embolus.
b Protamine.
c Extensive lung resection.
d Acute respiratory distress syndrome (ARDS).
e Obstructive sleep apnoea.

All True
Causes of RV failure can be divided into: intrinsic RV failure in the absence of pulmonary hypertension, usually due to RV infarction; RV failure secondary to increased RV afterload and pulmonary hypertension; and RV failure due to volume overload. Acute pulmonary emboli may cause an increase in pulmonary vascular resistance and thus RV afterload and therefore may cause RV failure.
Protamine is used to reverse the effects of heparin and results in the production of protamine-heparin complexes. The complexes stimulate complement activation and the production of thromboxane, which can in turn lead to pulmonary arterial vasoconstriction, increased pulmonary afterload and RV failure.
Extensive lung resection may result in increased pulmonary artery pressures — due to several different mechanisms — and this can potentially result in increased RV afterload and RV failure.
The extensive alveolar and capillary lesions seen in acute respiratory distress syndrome (ARDS) have deleterious effects on pulmonary circulation and may result in increased pulmonary vascular resistance, increased RV afterload and RV failure.
Obstructive sleep apnoea may cause raised pulmonary artery pressures and subsequently RV failure.
1. Kevin LG, Barnard M. Right ventricular failure. Contin Educ Anaesth Crit Care Pain
2007; 7(3): 89-94.

Regarding prone position ventilation:
a.The PROSEVA study group showed no mortality benefit at 28 days
in severe acute respiratory distress syndrome (ARDS).
b.Alveolar recruitment is improved with better drainage of secretions.
c.A more homogenous ventilation distribution is achieved, due to
favourable changes in thoraco-abdominal compliance.
d.Proning increases extravascular lung water.
e.The optimal duration of prone positioning is 24 hours.

True b & C
The PROSEVA study group found improved 28-day mortality (16% prone vs. 32.8% supine [p=0.001]) and 90-day mortality (23.6%
prone and 41% supine [p<0.001]) in severe ARDS (Pa02/Fi02 ratio <150mmHg).
The prone position improves alveolar recruitment and allows better drainage of chest secretions.
With proning a more homogenous ventilation distribution is achieved, due to favourable changes in thoraco-abdominal compliance.
Extravascular lung water is reduced following proning.
The optimal duration of proning is currently unknown. The PROSEVA study proned patients for at least 16 hours. The average number of proning sessions was 4+/-4 per patient.
1. Guerin C, Re gnier J, Richard JC, etal. Prone positioning in severe acute respiratory distress syndrome. New Engl J Med 2013; 368(2):159-68.
2. Waldmann C, Soni N, Rhodes A. Oxford Desk Reference Critical Care. Oxford, UK: Oxford University Press, 2008.
3. Edgcombe H, Carter K, Yarrow S. Anaesthesia in the prone position. Br .1 Anaesth 2008; 100(2): 165-83

In biphasic positive airway pressure (BIPAP):
A. The ventilator generates a dual CPAP level with an upper and lower pressure
set by the user
B. Patients may freely generate spontaneous breaths in the low pressure phase
only
C. Patients are allowed to exhale even during the high pressure phase
D. Airway Pressure Release Ventilation is an extreme concept of BIPAP with a
very short low pressure phase

A. T
B. F
C. T
D. T

 

 

Positive end-expiratory pressure (PEEP):
a In severe acute respiratory distress syndrome (ARDS), a PEEP >15cmH20 improves mortality.
b PEEP increases functional residual capacity.
c Hepatic and renal blood flow is increased with higher levels of PEEP.
d PEEP application increases intrathoracic pressure, diminishing venous return to the right heart.
e An observed increase in lung compliance suggests alveolar recruitment.

True b, d & e

In severe ARDS, high PEEP (>15cmH20) does not improve mortality. Some PEEP (around 5-10cmH20) is associated with improved oxygenation.
Application of PEEP increases functional residual capacity.
Decreased renal blood flow and reduced splanchnic and hepatic perfusion can occur with higher levels of PEEP.
PEEP application increases intrathoracic pressure, diminishing venous return to the right heart.
Following PEEP application, an observed increase in lung compliance is suggestive of alveolar recruitment.

The National Heart, Lung and Blood Institute ARDS Clinical Trials Network. Higher versus lower positive end-expiratory pressures in patients with the acute respiratory distress syndrome. New Engl J Med 2004; 351: 327-36
2. Waldmann C. Soni N, Rhodes A. Oxford Desk Reference Critical Care. Oxford, UK: Oxford University Press, 2008.

 

 

Regarding the I:E ratio
A. Is normal set between 1:3 and 1:4
B. Should be lowered to decrease intrinsic PEEP
C. Increase I:E ratio may improve alveolar recruitment and oxygenation in ARDS
D. Adjustment of I:E ratio must be matched with respiratory frequency

A. F
B. T
C. T
D. T

 

 

The following have been shown to improve mortality in acute respiratory distress syndrome (ARDS):
a Inhaled (b-agonists.
b Prone ventilation.
c Treatment with intravenous glucocorticoids.
d Use of high-frequency oscillatory ventilation (HFOV).
e Ventilation at tidal volumes of 6ml per kg.

True b & e 
The BALTI-2 trial suggested (b agonists may increase mortality in ARDS. 
The PROSEVA study demonstrated a mortality benefit in patients with ARDS. A total of 237 patients were assigned to the prone group, and 229 patients were assigned to the supine group. 28-day 
mortality was 16.0% in the prone group and 32.8% in the supine group (p<0.001).
The use of steroids in ARDS is controversial; methylprednisolone given at least 7 days after the onset of ARDS has been suggested to reduce time spent on mechanical ventilation, but has not shown conclusively to reduce mortality.
HFOV does not improve mortality in ARDS, and has been demonstrated to increase mortality compared to current best practice.
As initially described in the ARDSNET study, low tidal volume ventilation (6-7m1/kg) reduces mortality in ARDS. This is now considered a standard of practice in patients with ARDS.
Smith FG, Perkins GD, Gates S, et al, for the BALTI-2 study investigators. Effect of intravenous 13-2 agonist treatment on clinical outcomes in acute respiratory distress syndrome (BALTI-2): a multicentre, randomised controlled trial. Lancet 2012; 379: 21.7. 
Guerin C, Reignier J, Richard JO; et al. Prone’ [)ositioning in severe acute respiratory distress syndrome. New Engl J Med 2013;.3,58(2): 159-68.
The National Heart, Lung and Blood Institute Acute Respiratory Distress Syndrome (ARDS) Clinical Trials Network. Efficacy and safety of corticosteroids for persistent acute respiratory distress syndrome. The National Heart, Lung and Blood Institute Acute Respiratory Distress Syndrome (ARDS) Clinical Trials Network. N Engl J Med 2006; 354: 1671-84. 
Ferguson ND, Cook DJ, Guyatt GH, et al, for the OSCILLATE Trial Investigators and the Canadian Critical Care Trials Group. High:Oequency oscillation in early acute respiratory distreQs syndrome. New Engl J Med 2013; 368(9): 795-805.
Young D, Lamb SE, Shah S, et al. High-frequency oscillation for acute respiratory distress syndrome. New Engl .1 Med 2013; 368: 80-6-13.
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:yndrome. New Engl J Med 2000; 342(18): 1301-8.

 

Various methods to set optimal PEEP at the bedside include:
A. Arterial PaO2
B. Analysis of the pressure-volume curve (lower inflection point)
C. Recording of the oesophageal pressure to estimate transpulmonary pressure
D. Measurement of end-expiratory lung volume variations

A. T
B. T
C. T
D. T

 

 

The following are recognised strategies in the prevention of ventilator-associated pneumonia (VAP):
a Daily sedation holds.
b Head-up positioning of 30 to 45°.
c Prone positioning.
d Chlorhexidine mouthcare.
e Daily ventilator tubing changes.

True a, b & d
Daily sedation holds have been demonstrated to reduce patient time spent on the ventilator, and thus reduce the incidence of VAP
Head-up positioning of 30 to 45° reduces micro-aspiration, and thus the incidence of VAR
Prone positioning improves mortality in severe ARDS, but its impact on VAP rates per se is as yet unclear.
Chlorhexidine mouthcare has been demonstrated to reduce the incidence of VAP
Daily changes of ventilator tubing may increase the VAP risk due to cross-contamination from excess handling of equipment.
1. Hunter JD. Ventilator-associated pneumonia. Br Med J 2012; 344: e3325.
2. Guerin C, Reignier J, Richard JC, et al. Prone positioning in severe acute respiratory distress syndrome. Now Engl J Med 2013: 368(2): 159-68.

Disadvantages of endotracheal intubation includes all of the
following, EXCEPT

A. Loss of the protective function of the upper airway
B. Loss of phonation
C. Decreased airway resistance
D. Damage to the subglottic area
E. Need for sedation and or analgesia

Answer C is correct

 

During the 2009 H1N1 influenza A pandemic:
a Zanamivir (Relenza) is administered via the oral route.
b Oseltamivir is an M2 channel blocker and given in a dose 75rng twice a day.
c The Sequential Organ Failure Assessment (SOFA) score was suggested by the UK Government as a critical care admission triage tool.
d Pregnancy was an independent predictor of mortality.
e Transfer to an extracorporeal membrane oxygenation (ECMO) centre, in patients with H1N1-related acute respiratory distress syndrome (ARDS) was associated with lower hospital mortality.

True c & e
Zanamivir is given intravenously and is used when the enteral absorption of oral oseltamivir is poor or in cases of resistant virus. Oseltamivir is an oral neuraminidase inhibitor, which is active against both influenza A and B. It is dosed at 75mg bd for 5 days, doubled in severe infection (150mg bd for 10 days). Ribavirin may also be used in conjunction. M2 channel blockers (rimantadine) are not routinely used to treat influenza, due to neurotoxicity.Hemagglutinin (HA) and neuraminidase (NA) are the two large glycoproteins on the outside of the viral particles. HA is a lectin that mediates binding of the virus to target cells and entry of the viral genome into the target cell, while NA is involved in the release of progeny virus from infected cells, by cleaving sugars that bind the mature viral particles.Thus, these proteins are targets for antiviral drugs.

Once inside the cell, the acidic conditions in the endosome cause two events to happen: First, part of the hemagglutinin protein fuses the viral envelope with the vacuole’s membrane, then the M2 ion channel allows protons to move through the viral envelope and acidify the core of the virus, which causes the core to disassemble and release the viral RNA and core proteins.The viral RNA (vRNA) molecules, accessory proteins and RNA-dependent RNA polymerase are then released into the cytoplasm (Stage 2). The M2 ion channel is blocked by amantadine drugs, preventing infection
The SOFA score was suggested by the UK Department of Health as a critical care triage tool. Triage suggested included patients with a SOFA score >11 and certain inclusion/exclusion criteria would not be admitted to critical care, and also withdrawal of care would be considered at 48 hours and on subsequent days for patients with SOFA scores >11. Retrospective survey data post-pandemic suggested if this approach had been undertaken, withdrawal of care would have potentially occurred in several patients who subsequently survived after a short period of ventilation.
Influenza infection whilst pregnant (particularly during the 3rd trimester) carries a high rate of complications and increased need for hospitalisation (4-7 x risk).
Referral and transfer of H1N1-related ARDS to an ECMO centre was associated with a lower hospital mortality compared with non-ECMO referred patients, even if the referred patients did not ultimately receive ECMO.
Gwavava C, Lynch G. Intensive care management of pandemic (H1N1) influenza. Anaesthesia Tutorial of the Week 2009, 2011. http://www.aagbi.org/education/educational -resources/tutorial-week.
2, Noah MA, Peek GJ, Finney SJ, et al. Referral to an extracorporeal membrane oxygenation center and mortality among patients with severe 2009 influenza A JAMA 2011; 306(15): 1659-68,
3 Zangrillo A, Zoccai GB, Landoni G, et al. Extracorporeal membrane oxygenation (ECMO) in patients with HI NI influenza infection: a systemic review and meta-analysis including B studies and 266 patients receiving ECMO. Crit Care 2013; 17: R30.

To increase oxygenation during IPPV all of the following are useful
EXCEPT:

A. Increase FiO2
B. Increase PEEP
C. Decrease I:E ratio
D. Increase peak inspiratory pressure
E. Alveolar recruitment

Answer C is correct

Influenza A:
a Influenza A is a DNA virus.
b Neuraminidase facilitates the release of newly replicated viruses
from infected cells.

c Haemagglutinin allows attachment of the virus to host respiratory
epithelium.
d Influenza A is characterised by cough, fever, myalgia and sore
throat.
e It is best detected using PCR (polymerase chain reaction)
techniques.

True b c d and e
Influenza A is an RNA virus.
Influenza A is described by surface glycoproteins, haemagglutinin (H) and neuraminidase (N). 16 types of haemagglutinin and 9 types of neuraminidase exist. Influenza B is the second type of influenza virus (i.e. A or B).
Haemagglutinin allows attachment of the virus to-host respiratory epithelium.
Influenza A is characterised by cough, fever, myalgia and sore throat.Reverse transcriptase polymerase chain reaction RT-PCR testing,
from nasopharyngeal swabs or aspirates, is the best method of diagnosis.
1. Gwavava C, Lynch G. Intensive care management of pandemic (H1N1) influenza. Anaesthesia Tutorial of the Week 2009, 2011, http://www.aagbi.org/education/educational -resources/tutorial-week.
2. Parsons PE, Wiener-Kronish JP. Critical Care Secrets, 5th ed. Missouri, USA: Elsevier Mosby, 2013.

Effective methods to decrease an elevated PaCO2 may include all of
the following EXCEPT:

A. Increase tidal volume
B. Increase frequency
C. Decrease circuit dead space
D. Increase PEEP
E. Increase inspiratory pressure

Answer D is correct

 

 

Critical care ventilation:
a During volume-controlled ventilation, the difference in peak and plateau pressures reflects the pressure required to overcome resistive forces.
b The plateau pressure during pressure-controlled ventilation reflects the pressure required to overcome elastic forces during inspiration.
c Auto-triggering describes the ventilator incorrectly cycling to inspiration.
d Desirable tidal volume should be based on the patient’s actual body weight.
e A lung protective strategy employs tidal volumes of 8-10m1/kg.

True a & c
During volume-controlled ventilation, the difference in peak and plateau pressures reflects the pressure required to overcome resistive forces.
During pressure-controlled ventilation (PCV), inspiratory pressures are constant, therefore, it is not possible to differentiate the elastic and resistive properties of the patient’s lungs from observation of the airway trace.
Auto-triggering describes the ventilator incorrectly cycling to inspiration.
Tidal volumes generated should be based on ideal body weight.
The ARDS network termed ‘lung protective ventilation’ to be 6-7m1/kg tidal volumes. Lung protective ventilation has been shown to reduce mortality in acute lung injury, with possible benefits also seen in patients with normal lungs.

Adverse effects of PEEP include the following EXCEPT:
A. Over distension of normal alveoli

B. Barotrauma
C. Decreased cardiac output
D. Increased intracranial pressure
E. Increased cyclic collapse of unstable alveoli

Answer E is correct

 

 

In relation to a potential ‘can’t intubate, can’t
ventilate (CICV) scenario’ in anaesthesia practice:

a It is estimated to occur in 0.01 to 2.0 per 100,000 cases.
b Jet ventilation is required for cricothyroidotomy with a cannula of >4mm diameter.
c Over 90% of CICV situations are preventable.
d Fixation error may lead to loss of situational awareness and poor decision making.
e Cricothyroidotomy skills are retained for only a short period.

True c, d & e
The CICV or can’t intubate, can’t oxygenate (CICO) scenario is an inability to secure the patient’s airway with an endotracheal tube and an inability to ventilate a patient’s lungs by conventional non-invasive means. This is a rare complication, estimated to occur in 0.01 to 2.0 per 10.000 cases.
Cannula cricothyroidotomy requires jet ventilation to ventilate a patient’s lungs when a narrow-bore cannula (e.g. 2mm diameter) is
used. A dedicated wide-bore proprietary cannula (>4mm) fits a
standard 15mm connector and does not require jet ventilation.
Data from the United States suggest that >90% of CICV situations are preventable with adequate pre-operative airway assessment and preparation.
The fixation in trying to ‘achieve endotracheal intubation at all costs’, and the persistence in trying an airway method that has already failed, results in significant human error, loss of situational awareness and poor decision making.
Skills in any cricothyroidotomy technique are retained for a short period of time only. It is recommended that chosen techniques should be practised every 3-6 months for optimal performance and skill retention.
1. Popat M. The unanticipated difficult airway: the can’t intubate, can’t ventilate scenario. Johnston I, Harrop-Griffiths W, Gemmell L, Eds. in: AAGB1 Core Topics in Anaesthesia 2012; 4: 44-55.
2. The Difficult Airway Society (DAS). http://das.uk.com/files/ddl-Jul04-A4.pdf

 

Regarding intensive care unit ventilation:
a Prolonging the expiratory time will increase the mean airway pressure.
b Increasing positive end-expiratory pressure (PEEP) may directly increase arterial oxygen tension.
c Decreased inspiratory time may cause gas trapping due to increased expiratory time.
d Morbid obesity may increase chest wall compliance.
e Auto-PEEP can be selected during controlled ventilation.

True b
The mean airway pressure is increased by prolonging the ventilator inspiratory time. This may increase arterial oxygen tension but it may also reduce venous return.
Increasing PEEP may directly increase arterial 02 tension.
Increased inspiratory time may cause gas trapping due to decreased expiratory time.
Generally, morbid obesity reduces chest wall compliance.
Auto-PEEP or intrinsic PEEP due to inadequate patient expiration may impair ventilator triggering.

 

During controlled ventilation:
a Airway pressure generated depends on the compliance and resistance of the respiratory system and circuit.
b The inspiratory pressure waveform is constant during volume ventilation.
c In time triggering, breaths are delivered according to a pre-set frequency.
d Triggering is when the ventilator incorrectly cycles to inspiration.
e Cycling is used to dictate when the inspiratory phase is complete.

True a, c & e
T Airway pressure generated during controlled ventilation depends on the compliance and resistance of the respiratory system and circuit.
F Inspiratory flow is constant (square wave) during volume-controlled ventilation.
T In time triggering, breaths are delivered according to a pre-set frequency.
F Triggering is when the ventilator detects a drop in airway pressure or flow that occurs when a patient makes a spontaneous breath, instigating the ventilator to deliver a positive pressure inspiratory breath.
T Volume, time and flow can be used to cycle the ventilator.

Waldmann C, Soni N, Rhodes A. Oxford Desk Reference Critical Care. Oxford, UK: Oxford University Press, 2008.

 

 

Weaning from mechanical ventilation:
a Weaning is the process of liberation from mechanical ventilation.
b Delay in weaning prolongs critical care stay, increases costs and is associated with a higher mortality.
c Synchronised intermittent mandatory ventilation (SIMV) alone is considered a poor weaning strategy.
d The ongoing need for inotropes precludes weaning.
e No universal consensus exists for weaning.

True a, b, c & e
T Weaning is the process of liberation from mechanical ventilation.
T Delay in weaning prolongs critical care stay, increases costs and is associated with a higher mortality.
T The use of synchronised intermittent mandatory ventilation (SIMV) alone from recent weaning trials is deemed the least efficient method for weaning. Combining SIMV with spontaneous breathing/pressure support may improve efficiency.
F The ongoing need for inotropes does not preclude weaning. There is no universal strategy or consensus currently for weaning critical care patients from mechanical ventilation. Further research and international collaboration is needed.
1. Waldmann C, Soni N, Rhodes A. Oxford Desk Reference eriticaf Care. Oxford, UK: Oxford University Press, 2008.
2. Lermitte J, Garfield MJ. Weaning from mechanical ventilation. Contin Educ Anaesth Crit Care Pain 2005; 5(4): 113-7.

 

Regarding surgical resection of the oesophagus:
a A lumbar epidural is likely to be beneficial.
b A fibre-optic scope should be available to confirm correct double-lumen tube (DLT) placement.
c Respiratory morbidity is high postoperatively.
d Non-invasive ventilation in the early postoperative period is absolutely contraindicated.
e Acute onset of fast atrial fibrillation at 3-7 days postoperatively may herald the development of an anastomotic leak.

True b, c & e
F A thoracic epidural will aid effective postoperative analgesia, improving mobility and cough. It should be considered in all patients if not contraindicated.
T There is a significant morbidity/mortality associated following double-lumen endotracheal tube displacement and/or incorrect positioning. Respiratory failure post-oesophagectomy is common and may affect up to 25% of patients. There should be a low threshold for using a fibre-optic scope to confirm initial DLT placement and subsequent intra-operative tube position checks.
T Respiratory morbidity following oesophagectomy is common with respiratory complications occurring in approximately 25% of patients. These patients may require critical care re-admission and early intervention with potential re-intubation. Cardiovascular complications (12%) and anastomotic leak (16%) may also complicate the postoperative period.
F The use of non-invasive positive pressure ventilation (NPPV) for respiratory failure in the immediate postoperative period following oseophagectomy is controversial, but not absolutely contraindicated. High inspiratory (IPAP) and expiratory (EPAP,

CPAP) pressures may hypothetically cause anastomotic distension and subsequent leak. However, there is increasing evidence that these concerns may be overstated and that NPPV use for postoperative respiratory failure may decrease re-intubation need and acute respiratory distress syndrome (ARDS), without increasing the risk of anastomotic leakage. Although, gastric distension is unlikely below inspiratory pressures of 25cmH20, the use of nasogastric drainage is advocated by many, as this would reduce the risk of distension. Further studies are warranted.
Anastomotic leak may occur typically between 3-7 days and may present with non-specific signs such as pyrexia, general malaise, respiratory infection and cardiac arrhythmias (often atrial fibrillation is seen).
1. Rucklidge M, Sanders D, Martin A. Anaesthesia for minimally invasive oesophagectomy. Contin Educ Anaesth Crit Care Pain 2010; 10(2): 43-7.
2. Sherry KM, Smith FG. Anaesthesia for oesophagectomy. Contin Ethic Anaesth Crit Care Pain 2003; 3(3): 67-90
3. Michelet P, D’Journo XB, Seinaye F, et al. Non-invasive ventilation for the treatment of postoperative respiratory failure after oesophagectomy. Br J Surg 2009; 96: 54-60.

 

Management of tracheostomy and laryngectomy emergencies:
a If the patient is making spontaneous breathing efforts, hand ventilation using a Mapleson C circuit should be used initially to assess the tracheostomy patency.
b High-flow oxygen should be applied to the face and tracheostomy.
c A suction catheter should be used to assess tracheostomy patency.
d A laryngeal mask over the stoma site is inappropriate for ventilation.
e A size 7.0 cuffed endotracheal tube should be used to intubate the stoma

True b & c

Initial manual or hand ventilation of a potentially displaced tracheostomy may cause massive surgical emphysema and impede resuscitative efforts and so is not advised. Attaching the Mapleson C or Water’s circuit with capnography to the tracheostomy tube, whilst the patient is making spontaneous ventilatory effort, is extremely useful as it can quickly establish that the tracheostomy is indeed in the airway and is patent/semi-patent through lung ventilation and CO2 exhalation.
This should be done even in laryngectomy patients as the distinction between a patient with a tracheostomy and a patent upper airway and a patient with a laryngectomy with no patent upper airway, may not be known at the time of resuscitative efforts and initial assessment.
Use of a soft suction catheter is an effective way of assessing tracheostomy patency.
During primary emergency oxygenation, a laryngeal mask or supraglottic airway device over the tracheostomy/laryngectomy stoma site may prove life-saving and should be considered early.
For secondary emergency oxygenation, intubation of the stoma can be undertaken in adults with a size 6.0 endotracheal tube or small tracheostomy tube. A size 7.0 endotracheal tube is not advised in the first instance as this may be too large. The priority here is to obtain a patent airway for oxygenation and ventilation, with success being more likely with a size 6.0 tube. An Aintree catheter may be very useful as one can oxygenate and even ventilate down it. A fibre-optic scope, bougie and/or airway exchange catheter may be considered in this drastic situation. 1. htto://www,tracheostomy.org.uk.
2. McGrath BA, Bates L, Atkinson D, Moore JA. Multidisciplinary guidelines for the management of tracheostomy and laryngectomy airway emergencies. Anaesthesia 2012; 67: 1025-41.

 

 

High-frequency ventilation:
a A high-pressure jet (10-50psi) is used in high-frequency oscillatory ventilation (HFOV).
b Lung compliance is improved by maintaining the lung on its deflation limb on the dynamic pressure-volume curve.

C Peak airway pressures are increased.
d Oxygenation and carbon dioxide elimination are decoupled in HFOV.
e The OSCILLATE trial found a higher mortality associated with HFOV use.

True d & e
In high-frequency jet ventilation (HFJV), a high-frequency, high-pressure jet (10-50 pound/square inch, psi or 68.9-344.5kPa) is delivered via a small-bore cannula into the airway. Air is entrained into the airway by the high-pressure jet. Exhalation occurs passively.
During high-frequency ventilation the lung is maintained on its deflation limb on the static pressure-volume curve, improving lung compliance and alveoli recruitment.
Peak airway pressures are reduced with high-frequency ventilation, minimising barotrauma.
Oxygenation and carbon dioxide elimination are decoupled in high-frequency oscillatory ventilation (HFOV).
In the OSCILLATE trial, 548 patients from 39 centres were recruited. Mortality was 47% in HFOV vs. 35% receiving conventional ventilation. Increased sedative and muscle relaxant use was required in the HFOV group. In another trial conducted around the same time, the OSCAR trial found an identical 41 % 30-day mortality. Increased sedative and muscle relaxant use was also found in the HFOV group.
1. Waldmann C, Soni N, Rhodes A. Oxford Desk Reference Critical Care. Oxford, UK: Oxford University Press, 2008.
2. Ferguson N, Cook DJ, Guyatt GH, et al; the OSCILLATE Trial Investigators. High-frequency oscillation in early acute respiratory distress syndrome. New Eng! J Med 2013; 368(9): 795-805.
3. Young 0, Lamb SE, Shah S, et a!; the OSCAR Study Group. High-frequency oscillation for acute respiratory distress syndrome. New Eng! .1 Med 2013; 368: 806-13.

 

 

Non-invasive ventilation (NIV):
a Decreases work of breathing and may aid weaning from mechanical ventilation.
b Can reduce the need for intubation and hospital morbidity.
c Failure is associated with a higher mortality in respiratory failure.
d Greatest benefit is seen in acute hypercapnic chronic obstructive pulmonary disease (COPD) exacerbation or cardiogenic pulmonary oedema.
e Severe acidosis is a contraindication.

True a b c d
NIV decreases the work of breathing and may aid weaning from
mechanical ventilation.
Can reduce the need for intubation and hospital morbidity.
Failure of NIV is associated with a higher mortality in respiratory failure.
The greatest benefit of NIV use is seen in patients with respiratory failure caused by acute COPD exacerbation or cardiogenic pulmonary oedema.
Severe respiratory acidosis (<pH 7.25) is not a contraindication for a short trial of NIV (1-2 hours) in a monitored environment, where prompt intubation and ventilation may be undertaken as rescue, if NIV fails. Coexistent severe metabolic with respiratory acidosis, may suggest a mixed aetiology and other organ dysfunction, resulting in a greater incidence of NIV failure.

 

Non-invasive ventilation (continuous positive airway pressure [CPAP]/bilevel positive airway pressure [BiPAP]) is contraindicated in:
a Coma.
b Mechanical bowel obstruction.
c Recent upper GI surgery.
d Cardiogenic pulmonary oedema.
e Chest wall trauma.

True a & b
Coma (GCS <8/15) of any cause, the patient is unable to protect their airway and is at risk of aspiration. This is particularly true if non-invasive ventilation is used.
Mechanical bowel obstruction poses a significant aspiration risk which may be exacerbated with non-invasive ventilation.
There is a hypothetical risk of aspiration and strain of suture lines post-oesophagectomy with non-invasive ventilation. However, there is increasing evidence that CPAP with nasogastric tube decompression is safe and may prevent the need for re-intubation post-oesophagectomy. Further studies are warranted to investigate further.
There is a significant mortality benefit with non-invasive ventilation use in cardiogenic pulmonary oedema.
Non-invasive ventilation may be beneficial in chest trauma with persistent hypoxaemia, as it may establish and maintain lung recruitment, improving overall gas exchange.
1. Waldmann C, Soni N, Rhodes A. Oxford Desk Reference Critical Care. Oxford,UK: Oxford University Press, 2006.
2. Michelet P, D’Journo XB, Seinaye F, et al Non-invasive ventilation for the treatment of postoperative respiratory failure after oesophagectomy. Br J Surg 2009; 96: 54-60.

 

High-frequency ventilation (HFV):
a When compared to HFV, tidal volume must exceed dead space for effective ventilation during conventional ventilation.
b During HFV, tidal volumes are near to or less than anatomical dead space.
c Pendelluft is the principal mechanism of gas transport in HFV.
d Taylor dispersion is the exchange of gas between adjacent lung units due to differing time constants.
e Molecular diffusion is not important in HFV.

True a & b
T Tidal volume must exceed dead space for effective ventilation during conventional ventilation: VA=f(VT-VD).
T Tidal volumes are near to or less than anatomical dead space during H FV.
F Pendelluft is the exchange of gas between adjacent lung units due to their differing time constants. Gas flows from fast- to slow-filling units at the end of inspiration and the reverse occurs at the end of expiration.
F Taylor dispersion is the interplay between convective forces and molecular diffusion causing laminar and radial gas dispersion.
F Molecular diffusion is the principal mechanism of gas transport in the terminal airways.

 

Ventilator-induced lung injury (VILI):
a Gross barotrauma manifesting as pneumothorax is a frequent complication of mechanical ventilation.
b Atelectrauma occurs due to direct injury to the alveoli from over-distension.

c Biotrauma occurs due to shearing injury to the alveoli, caused by repetitive collapse and opening.
d Development of extra-alveolar air due to perivascular alveoli disruption is thought to be an initial mechanism of barotrauma.
e Biotrauma in the lung increases leucocytes, tumour necrosis factor (TNF), IL-6 and IL-8 release.

True a, d & e
Gross barotrauma manifesting as pneumothorax is a frequent complication of mechanical ventilation. Other complications include: pulmonary interstitial emphysema or subcutaneous emphysema, progression of pneumothorax to tension pneumothorax and cardiac arrest.
Direct injury to alveoli from over-distension is volutrauma.
Atelectrauma occurs due to the repetitive collapse and opening during mechanical ventilation causing shearing injury to alveoli. Biotrauma results from inflammatory mediators in the airspace and circulation.
Development of extra-alveolar air due to perivascular alveoli disruption is thought to be an initial mechanism of barotrauma.
Biotrauma in the lung increases leucocytes, TNF, IL-6 and IL-8 release.
1. Waldmann C, Soni N, Rhodes A. Oxford Desk Reference Critical Care. Oxford. UK: Oxford University Press, 2008.
Answer 87: Regarding hepatic encephalopathy: True a, c &
d
T The West Haven system is used to stage hepatic encephalopathy from 0 to IV: Grade 0 is when no abnormality is detected; Grade I is lack of awareness, euphoria, agitation, reduced attention span; Grade II is intermittent disorientation, drowsiness, inappropriate

 

Pulmonary function tests:
a The Fowler method can be used to determine functional residual capacity (FRC).
b Vital capacity (VC) monitoring is useful in all critically ill patients when predicting the need for intubation.
c The ratio of respiratory frequency to tidal volume (f/VT) is not a reliable predictor of weaning outcome.
d Intrinsic positive end-expiratory pressure (PEEPi) may develop during mechanical ventilation if the expiratory time is too short or expiratory resistance is increased.
e Respiratory drive can be assessed by measuring airway pressure 0.1 sec after occluding the airway against inspiratory effort.

 

 

in relation to pregnancy and critical care the
following are true:
a Alveolar ventilation is increased during pregnancy.
b There is increased glomerular filtration in pregnancy.
c Major obstetric haemorrhage is the leading cause of maternal mortality worldwide and is the most frequent indication for pregnancy-related critical care admission.
d Anaemia seen in the HELLP syndrome is non-haemolytic in nature.
e The majority of survivors of amniotic fluid embolus syndrome suffer chronic neurological deficits.

True a-c & e

Respiratory
Increased alveolar ventilation (70%), relative hypocarbia (PaCO2 of 25-32mmHg), reduced functional residual capacity (20%), increased 02 consumption and reduced venous oxygen saturation (Sv02)
Cardiovascular Increased cardiac output (40%), increased stroke volume (25%), increased heart rate (25%), reduced total peripheral resistance, normal CVP in superior vena cava distribution, elevated CVP in inferior vena cava distribution, aorto-caval compression, increased circulating volume, increased plasma volume (40-50%), increased red cell mass (20%) and physiologic anaemia
Gastrointestinal Reduced lower oesophageal sphincter tone, elevated risk of gastro-pulmonary aspiration, increased metabolism of carbohydrate +++, protein ++ and fat +, and hyperglycaemia (due to insulin resistance)
Haematopoietic Reduced haemoglobin concentration (functional anaemia despite elevated red cell mass), slightly elevated leucocyte count, slightly reduced platelet count, increased clotting tendency
Renal Increased renal blood and plasma flow (5Q-60%), increased glomerular filtration (50-60%), reduced serum urea and creatinine, glycosuria and mild proteinuria

 

Indications for intubation and ventilation
after traumatic brain injury prior to transfer include:
a Glasgow Coma Scale (GCS) score <12.
b Decrease in motor response score >2 points.
c Bilateral mandibular fractures.
d Spontaneous hyperventilation.
e Seizures.

All True

Traumatic brain injury is a formal indication for intubation and ventilation. The Association of Anaesthetists of Great Britain and Ireland (AAGBI) in their 2006 document state that: "Tracheal  intubation during transfer is difficult and dangerous. All patients with a GCS of 8 or less require intubation prior to transfer. In addition, whatever the baseline GCS, intubation should be considered if the GCS has fallen by 2 or more points. Intubation is essential if there is a fall of 2 or more points in the motor score. Intubation requires adequate sedation and muscle relaxation to avoid an increase in [ICP], and measures to prevent aspiration of gastric contents. This will normally involve rapid sequence induction with in-line stabilisation of the cervical spine". If the GCS has fallen from a baseline of 15 to 12, this is an indication for intubation, particularly if transfer is being considered.
A decrease in motor response score of >2 points indicates a deteriorating conscious level and a likely need for intubation prior to transfer.
Bilateral mandibular fractures pose a bleeding risk to the airway and potential difficult airway.
If spontaneous hyperventilation reduces PaCO2 to less than 4.0kPa, the subsequent vasoconstriction may worsen cerebral perfusion. This warrants intubation and ventilation for neuroprotection.
Seizures are an indication for intubation and ventilation.
1. Dinsmore .1. Traumatic brain injury: an evidence-based review of management. Contin Educ Anaesth Crit Care Pain 2013; 13(6): 189-95.
2. The Association of Anaesthetists of Great Britain and Ireland (AAGBI). Recommendations for the safe transfer of patients with brain injury, 2006. http://www.aagbi.orgisitesidefault/filesibraininjury.odf.

 

The following have been demonstrated to reduce the incidence of ventilator-associated pneumonia (VAP):
a Prophylactic antibiotics in ventilated patients.
b Head-up patient positioning.
c Daily sedation holds.
d Subglottic irrigation devices.
e Low tidal volume ventilation.

 

Regarding the Berlin definition for acute respiratory distress’syndfame (ARDS):
a The timing of ARDS must occur within 5 days of a known clinical insult and new or worsening respiratory symptoms.
b Bilateral opacities are evident on chest imaging, which are not attributable to effusions, lobar collapse or pulmonary nodules.
c The respiratory failure seen cannot be fully explained by cardiac failure or fluid overload.
d ARDS is classified into mild and severe according to the PaO2/FiO2 ratio.
e Severe ARDS is defined by a Pa02/Fi02 ratio of <150mmHg with a positive end-expiratory pressure (PEEP) >5cmH2O.

 

Non-invasive ventilation (NIV):
a Decreases the work of breathing and may aid weaning from mechanical ventilation.
b Can reduce the need for intubation and hospital morbidity.
c Failure is associated with a higher mortality in respiratory failure.
d Greatest benefit is seen in acute hypercapnic chronic obstructive pulmonary disease (COPD) exacerbation or cardiogenic pulmonary oedema.
e Severe acidosis is a contraindication.

 

True a-d
NIV decreases the work of breathing and may aid weaning from
mechanical ventilation.
Can reduce the need for intubation and hospital morbidity.
Failure of NIV is associated with a higher mortality in respiratory
failure.
The greatest benefit of NIV use is seen in patients with respiratory failure caused by acute COPD exacerbation or cardiogenic pulmonary oedema.
Severe respiratory acidosis (<pH 7.25) is not a contraindication for a short trial of NIV (1-2 hours) in a monitored environment, where prompt intubation and ventilation may be undertaken as rescue, if

NIV fails. Coexistent severe metabolic with respiratory acidosis may suggest a mixed aetiology and other organ dysfunction, resulting in a greater incidence of NIV failure.
1. Waidmann C. Soni N, Rhodes A. Oxford Desk Reference Critical Care. Oxford, UK: Oxford University Press, 2008.
2. McNeil_GBS, Glossop AJ. Clinical applications of non-invasive ventilation in critical care. Contin Educ Anaesth Crit Care Pain 2012: 12(1): 33-7.

 

 

Cardiopulmonary exercise testing (CPET):
a A standard seven-panel plot is used to display physiological results graphically.
b Peak VO2 (oxygen consumption) is independent of patient motivation.
c The anaerobic threshold (AT) is the point at which the rate of oxygen consumption (V02) increase exceeds the rate of carbon dioxide output.
d An AT <14m1/kg/min is associated with worse outcomes following major surgery.
e Multivariate analysis can be applied to CPET data to predict 5-year survival after major surgery.

 

True E
A standard nine-panel plot is used to graphically present CPET results. Panels 2, 3 and 5 relate to the cardiovascular system; panels 1, 4 and 7 examine ventilation and panels 6, 8 and 9 examine ventilation perfusion relationships.
The anaerobic threshold (AT) is independent from patient motivation and provides a reliable measure of dynamic functional capacity specific to that patient. Peak VO2 represents the maximum VO2 that is measured, usually at the point where exercise is terminated, and therefore may be influenced by patient motivation to continue exercising. Peak VO2 correlates with postoperative cardiopulmonary complications after oesophagectomy and abdominal aneurysm surgery.
The anaerobic threshold (AT) is the point at which the rate of increase of carbon dioxide output exceeds the rate of increase in oxygen consumption (V02). It is the point where aerobic metabolism alone is no longer adequate and is supplemented by anaerobic production of adenosine triphosphate (ATP).
Patients with a peak VO2 less than 14m1/kg/min have a worse overall prognosis than those with a peak VO2 above 14m1/kg/min in patients with heart failure. Patients with an anaerobic threshold (AT) <11m1/min/kg are considered high risk, as there is a higher associated morbidity and mortality following major abdominal surgery. Patients with a pre-operative AT <11m1/kg/min should be admitted to critical care following major surgery.
Multivariate analysis and model generation techniques can be applied to CPET data to predict 5-year survival after major surgery.
1. Agnew N. Preoperative cardiopulmonary exercise testing. Contin Ethic Anaesth Crit Care Pain 2010; 10(2): 33-7.
2. Drury N, Carlisle J. Cardiopulmonary exercise testing. Anaesthesia Tutorial of the Week 217, 2011. http://www.aagbi.org/educationleducational-resources/tutorial-week.
3. Older P, Hall A, Hader R. Cardiopulmonary exercise testing as a screening test for perioperative management of major surgery in the elderly. Chest 1999; 116: 355-62.

4. Colson M, Baglin J, Bolsin S, Grocott MPW. Cardiopulmonary exercise testing predicts 5-year survival after major surgery. Br) Anaesth 2012; 109(5): 735-41.

 

image

If this man requires invasive ventilation, what problem would you anticipate:-

a. Difficult Bag Mask Ventilation

b.Difficult Tracheal intubation

C.High risk of aspiration

D. Corneal Damage

Ans is B.

Small mandible/ and decrease Thyromental distance

One Response to “MCQs in Respiratory Critical Care”

  1. Shoaib Malik said

    good learning

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