A 45-year-old previously healthy woman presents to the emergency department with 3 days of fevers and progressive dyspnea and is admitted to the intensive care unit (ICU) for influenza infection complicated by severe hypoxemia. She is intubated, and chest radiograph following intubation demonstrates an appropriately placed endotracheal tube with bilateral patchy opacities and interstitial markings throughout all lung fields, without effusions. Her bedside echocardiogram reveals a left ventricular ejection fraction of 0.75 with otherwise normal findings. Her ventilator settings are:
An initial arterial blood gas (ABG) is:
Which of the following therapies has been best shown to improve the survival of patients such as this woman?
Correct Answer: B
This patient is presenting with severe ARDS, as defined by the Berlin criteria: onset within 1 week or presentation, bilateral opacities on imaging, edema not fully explained by cardiogenic etiology, and PaO2 :FiO2 ratio of <100. The ARDSnet trial demonstrated a significant mortality benefit with lung protective, low-TV ventilation (6 mL/kg IBW) (answer B is correct). Diuresis to an even fluid balance increases ventilator-free days in patients with ARDS but has not been found to have a mortality benefit (answer A is incorrect). Similarly, while inhaled nitric oxide and PEEP titration may improve oxygenation, neither intervention has been demonstrated to improve survival (answers C and E are incorrect). Invasive respiratory cultures are not recommended in patients with severe community acquired pneumonia (answer D is incorrect).
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A 32-year-old man with severe asthma is admitted to the ICU with an acute asthma exacerbation. He is intubated, paralyzed, and mechanically ventilated. His ventilator settings are:
His ABG on these settings is:
On day 2 of his ICU stay, an end-expiratory hold maneuver is performed and his airway pressure is measured at 15 cm H2O. Several hours later, he is noted to have progressive tachycardia, and his blood pressure has decreased from 120/90 to 75/55 mm Hg. A chest radiograph demonstrates similar findings to the prior day, without evidence of new infiltrate or pneumothorax.
What is the best next step in management?
Correct Answer: A
The patient has developed hemodynamic instability as a result of intrinsic PEEP, or dynamic hyperinflation, which increases intrathoracic pressure and decreases venous return. This is a life-threatening complication that requires immediate release of trapped gas from the lungs; this is best accomplished by disconnecting the ventilator circuit for a brief period of time (answer A is correct). Intrinsic PEEP can be very common in patients with obstructive lung disease on the ventilator.
Without evidence of pneumothorax on radiograph, ultrasound, or other high suspicion, a needle decompression is not warranted (answer B is incorrect). Bronchoscopy is occasionally utilized to clear mucous plugging in patient with severe asthma, however this would not explain the patient’s hemodynamic instability (answer C is incorrect). An increase in the respiratory rate will decrease the patient’s expiratory time and lead to worsening gas trapping (answer D is incorrect). A decrease in the extrinsic PEEP set on the ventilator will not decrease intrinsic PEEP and will not improve this patient’s hemodynamics (answer E is incorrect).
Reference:
A 68-year-old man with community-acquired pneumonia is intubated in the ICU with respiratory failure. Following induction of anesthesia, while paralyzed, his ventilator is set on:
An inspiratory hold maneuver is performed and his peak inspiratory pressure is 25 cm H2O and plateau pressure is 15 cm H2O.
Which of the following is true regarding this patient’s respiratory mechanics?
Correct Answer: D
The respiratory system compliance is equal to the change in volume divided by the change in pressure. In this case, the change in volume is the TV (450 mL) and the change in pressure is the plateau pressure minus the PEEP (15 cm H2O − 5 cm H2O = 10 cm H2O) (answer D is correct). Without a measure of a pleural pressure, it is not possible to separately calculate lung and chest wall compliance (answers A, B and C are incorrect).
A 70-year-old woman is intubated in the ICU for respiratory failure following an episode of aspiration with resulting pneumonitis.
Which of the following practices is most likely to decrease her duration of mechanical ventilation?
Routine, protocolized implementation of a spontaneous breathing trial, paired with a spontaneous awakening trial, or interruption of sedation, results in a decreased duration of mechanical ventilation when compared with spontaneous breathing trial alone. Spontaneous breathing trials should be performed as a routine practice based on protocol, rather than when directed only by a medical provider (answers A and E are incorrect). Studies examining early tracheostomy have not demonstrated a decreased time on the ventilator, though this approach may be appropriate in select cases when reversal of the underlying process is not expected within several weeks (answer D is incorrect). In comparison with a decremental pressure support-based ventilator liberation strategy, spontaneous breathing trial is superior in ability to decrease the duration of mechanical ventilation (answer C is incorrect).
A 68-year-old woman is admitted to the hospital with an acute exacerbation of chronic obstructive lung disease. She is intubated for worsening hypercarbia and transferred to the medical ICU. On day 8 of her ICU stay, she is felt to be clinically improving and close to extubation readiness when she develops intermittent desaturation and increased tracheal secretions. A portable chest radiograph demonstrates a new right lower lobe infiltrate. A tracheal aspiration is obtained for culture.
Which of the following would be appropriate intravenous antibiotic regimen?
Correct Answer: C
The patient has developed a ventilator-associated pneumonia (VAP), as defined by new worsening respiratory status, worsening volume and quality of sputum, and new radiographic infiltrate. VAPs frequently occur because of aspiration of secretions around the cuff of an endotracheal tube. Nosocomial pathogens, including P. aeruginosa and methicillinresistant S. aureus, are common causes of VAP. Empiric coverage for these pathogens with an antipseudomonal beta-lactam and vancomycin is therefore recommended while awaiting culture results; choice of an antipseudomonal agent may depend on local resistance patterns (answer C is correct; answer D is incorrect). Treatment with ceftriaxone is inadequate as is does not provide coverage of Pseudomonas or methicillin-resistant S. aureus. Azithromycin is important when considering treatment of atypical organisms, particularly Legionella in community-acquired pneumonia, but would not be necessary for empiric VAP coverage (answer B and E are incorrect). Metronidazole adds additional anerobic coverage, which is not considered necessary in the treatment of VAP (answer A is incorrect).
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