13 During a disaster or pandemic when crisis standards have been activated, which of the following describes the best approach to allocating scarce resources such as ICU beds and invasive mechanical ventilators?First‐come‐first‐servedYoungest patients firstMaximum lives savedHighest SOFA score firstBedside clinician decisionFirst‐come‐first‐served is the approach when acute healthcare facilities operate using conventional standards and is in large part a libertarian approach. Age‐based schemes use a life‐cycle approach and may engender an element of ageism that does not incorporate the influence of underlying comorbid conditions such as malignancy. The highest SOFA score (higher score denotes greater organ failure) is an egalitarian approach and is characteristically inappropriate during crisis standards as those with the greatest illness will, in general, consume the greatest resources, including elements already in short supply and in a patient population with a reduced likelihood of survival. Maximum lives saved (greatest good for the greatest number) is the preferred approach as it is utilitarian and may be equitably supported by decision‐making by a triage committee that is not directly involved in patient care.Answer: CMaves RC, Downar J, Dichter JR, et al. Triage of scarce critical care resources in COVID‐19: an implementation guide for regional allocation an expert panel report of the Task Force for Mass Critical Care and the American College of Chest Physicians. Chest. 2020. https://doi.org/10.1016/j.chest.2020.03.063
14 A 62‐year‐old clinically severely obese patient (BMI = 42) presents with presumed moderate COVID‐19 pneumonia. CXR has ground glass opacities in mid ‐ and lower lung fields. Room air ABG = pH 7.32, PaC02 38, Pa02 64; lactic acid = 3.2 mmol/L. Which of the following is the next most appropriate step in therapy after obtaining cultures, initiating fluid resuscitation, and administering empiric antibiotics as well as dexamethasone?Initiate self‐driven prone position therapyImmediate oral endotracheal intubationBegin helmet CPAP therapyNon‐contrast enhanced chest CT scanNebulized hypertonic saline and albuterolThis patient has a body habitus that potentially precludes self‐prone position therapy due to the risk of vomiting and aspiration. There is no acute need for airway control as CO2 clearance is well‐maintained and oxygenation may be addressed using other modalities. Non‐invasive approaches also avoid iatrogenic ventilator‐induced lung injury and ventilator‐associated infection. A non‐contrast enhanced CT scan of the chest may be useful from a diagnostic standpoint but will not help address the current clinical condition. Initial management of oxygenation using a continuous pressure but variable flow approach that also allows the patient to be seated upright is an ideal initial approach. There is heightened concern with nebulized medications in COVID‐19 patients for possibly nosocomial transmission. This patient also does not have an indication for nebulized hypertonic saline at this time as hypertonic saline therapy in combination with albuterol is ideal for reducing the viscoelasticity of thick secretions but is not indicated to manage ground glass opacities.Answer: CGaulton TG, Bellani G, Foti G, et al. Early clinical experience in using helmet continuous positive airway pressure and high‐flow nasal cannula in overweight and obese patients with acute hypoxemic respiratory failure from coronavirus disease 2019. Critical Care Explorations. 2020; 2(9). doi: 10.1097/CCE.0000000000000216
15 In patients undergoing invasive mechanical ventilation, which of the following most strongly corelates with the risk of ventilator‐induced lung injury?Peak airway pressure = 35 cm H2O pressureMean airway pressure = 14 cm H2O pressure Positive End Expiratory Pressure = 12 cm H2O pressurePlateau pressure = 28 cm H2O pressureDriving pressure = 20 cm H2O pressureVentilator‐induced lung injury (VILI) is often described as the impact of asymmetric distribution of a volume of gas into compliant alveoli that occurs over a short period of time and induces structural damage. That structural damage incites inflammation and leads to a process known as biotrauma that reflects activation of cytokines, the initiation of neutrophil trafficking, and the degradation of surfactant. As a result, alveolar interdependency is deranged, and regional time constants are lengthened. High tidal volumes are associated with these events as noted in the initial ARDSNet trials that led to the current common low tidal volume ventilation approach for ARDS. While high peak airway pressures may occur with inappropriate ventilator prescriptions, a peak pressure of 35 cm H20 does not strongly correlate with VILI. Mean pressures of 14 cm H2O may occur as the ventilator is adjusted to address hypoxemia, and a plateau pressure < 30 cm H2O is an appropriate target.PEEP of 12 is an acceptable pressure, is not associated with VILI and instead may define a patient population with a lung that is difficult to recruit. Driving pressures (plateau minus PEEP) > 15 appear strongly correlated with VILI and may be related to intra‐tidal shear as well with rapid changes in pressure with breath cycling.Answer: EWilliams EC, Motta‐Ribeiro GC and Vidal Melo MF Driving pressure and transpulmonary pressure: how do we guide safe mechanical ventilation?. Anesthesiol. 2019; 131: 155–163 doi: https://doi.org/10.1097/ALN.0000000000002731.
16 The square waveform for gas delivery during volume cycled ventilation is anticipated to be of benefit in which of the following patient populations?Isolated traumatic brain injuryBlast injury pulmonary contusionsAbdominal compartment syndromeDamage control open abdomenClinically severe obesityBlast injury‐related pulmonary contusions lead to alveolar damage and collapse. Such patients benefit from alveolar recruitment to reduce hypoxic pulmonary vasoconstriction. A decelerating waveform – compared to a square waveform at the same peak flow rate for gas delivery – results in a longer inspiratory time and better matching of regional time constants as well as a lower peak airway pressure and a higher mean airway pressure. A higher mean airway pressure supports oxygenation. Since high peak airway pressures are a problem in those with the ACS, a square waveform is not ideal as it too is associated with higher peak pressures. With an open abdomen, using a decelerating waveform helps recruit the maximum number of alveolar units in preparation for abdominal wall closure and an increase in intra‐abdominal pressure. A square waveform is associated with decreased recruitment by comparison. Since there are no valves between the brain and the right atrium, cerebral venous drainage is enhanced with more time at a lower intra‐thoracic pressure – a direct consequence of a shorter inspiratory and a longer expiratory time, both of which are characteristic of the square waveform gas delivery profile. Those with clinically severe obesity demonstrate increased intra‐abdominal pressure at baseline and therefore benefit from the use of a decelerating waveform to help reduce peak airway pressure and support postero‐basal pulmonary recruitment as well.Answer: AHamahata NT, Sato R and Daoud EG Go with the flow‐clinical importance of flow curves during mechanical ventilation: a narrative review. Can J Respir Ther. 2020; 56: 11–20 doi: 10.29390/cjrt‐2020‐002. PMID: 32844110; PMCID: PMC7427988.
17 A surgical ICU’s data indicates that the mean length of time spent on mechanical ventilation is longer than desired. Which of the following is most likely to reduce the duration of mechanical ventilation for their patient population?Emplacing a night‐time intensivistUsing the ICU liberation bundleDaily bedside physical therapyEliminating benzodiazepine useEliminating opioid analgesic useThe goal of reducing the time spent on mechanical ventilation is a worthy goal for every ICU. This benefits from a multi‐professional approach to care that empowers team members to work together across every shift to facilitate liberation from mechanical