A 76-year old man is admitted because of cough, fever, and shortness of breath. His medical problems include type 2 diabetes mellitus and hypertension.
His blood pressure is 105/60 mm Hg, pulse is 110/min and regular, and respirations are 30/min. His oxygen saturation is 85% on room air. On examination, he had crackles at the right lower lung base. Chest x-ray showed a dense right lower lobe infiltrate. He was started on antibiotics.
Over the following 24 hours, he developed progressive respiratory failure requiring endotracheal intubation and mechanical ventilation. His antibiotic coverage was broadened. Bilateral crackles are heard on chest examination. Extremities are warm with bounding pulses.
Chest x-ray shows bilateral infiltrates involving both the upper and lower lungs. The current ventilator settings are as follows:

Arterial blood gas analysis shows pH 7.30, pCO₂ 49 mm Hg, and pO₂ 48 mm Hg.
Which of the following is the best next step in managing this patient?

Question

A 76-year old man is admitted because of cough, fever, and shortness of breath. His medical problems include type 2 diabetes mellitus and hypertension.
His blood pressure is 105/60 mm Hg, pulse is 110/min and regular, and respirations are 30/min. His oxygen saturation is 85% on room air. On examination, he had crackles at the right lower lung base. Chest x-ray showed a dense right lower lobe infiltrate. He was started on antibiotics.
Over the following 24 hours, he developed progressive respiratory failure requiring endotracheal intubation and mechanical ventilation. His antibiotic coverage was broadened. Bilateral crackles are heard on chest examination. Extremities are warm with bounding pulses.
Chest x-ray shows bilateral infiltrates involving both the upper and lower lungs. The current ventilator settings are as follows:

Arterial blood gas analysis shows pH 7.30, pCO₂ 49 mm Hg, and pO₂ 48 mm Hg.
Which of the following is the best next step in managing this patient?

Quizplus · Accepted Answer

11ec193a_9711_b3c4_853d_050aa1d23667_MD0002_00 This patient has severe hypoxemic respiratory failure from acute respiratory distress syndrome (ARDS). The oxygenation goal in ARDS is a PaO₂ of 55 to 80 mm Hg or oxyhemoglobin saturation (SpO₂) of 88 to 95%. This is achieved by adjusting the fraction of inspired oxygen (FiO₂) and PEEP. Regarding the amount of PEEP, the ARDS Network ALVEOLI study randomized patients to high levels of PEEP (starting at 12 cm H₂O) versus low levels (starting at 5 cm H₂O). This study found that there were greater improvements in oxygenation with higher levels of PEEP with no difference in the mortality rate between the two groups. The increased PEEP opens collapsed alveoli and spreads out the tidal volume over more alveoli, which decreases overall alveolar distention. This reduces cyclical atelectasis throughout the respiratory cycle and reduces ventilator associated lung injury. Therefore, in this patient, oxygenation is inadequate and it would be appropriate to increase the PEEP. (Choice A) Increasing FiO₂ can help with ventilation/perfusion mismatches but does not usually correct shunting, which is the primary cause of hypoxemia in ARDS. (Choice C) Increasing the respiratory rate will not correct hypoxemia due to shunting. Furthermore, low tidal volume ventilation frequently requires permissive hypercapnic ventilation, a strategy that allows for alveolar hypoventilation in order to maintain a low alveolar pressure and minimize barotrauma. (Choice D) Increasing the tidal volume is not as effective as increasing PEEP, and higher tidal volumes (12 mL/kg) are associated with increased mortality in ARDS patients. The initial tidal volume is set to 8 mL/kg predicted body weight (PBW) and decreased to 6 mL/kg PBW over the next 1-3 hours. (Choice E) Volume-limited and pressure-limited modes are both an acceptable means of ventilation. However, volume-limited ventilation modes have been studied thoroughly and there is no evidence that pressure-limited modes confer any additional benefit. Educational objective: Increasing PEEP improves oxygenation by recruiting flooded and collapsed alveoli, and is first-line therapy in ARDS patients with severe hypoxemia. __________ References: Ventilation with lower tidal volumes as compared with traditional tidal volumes for acute lung injury and the acute respiratory distress syndrome. (http://www.ncbi.nlm.nih.gov/pubmed/10793162) Higher versus Lower Positive End-Expiratory Pressures in Patients with the Acute Respiratory Distress Syndrome. (http://www.ncbi.nlm.nih.gov/pubmed/15269312)

A 76-Year Old Man Is Admitted Because of Cough, Fever