Question

A patient is admitted to the ICU with severe necrotizing pancreatitis. A few hours after admission, he developed increasing oxygen requirements and was intubated for hypoxemic respiratory failure. Initially, his oxygen saturation improved to the mid-90% range on an FiO₂ of 0.5 (50%), but in the past 2 hours, the nurse has had to increase the FiO₂ back to 0.7 (70%) and his SaO₂ is still in the lower 90% range. The patient remains on a PEEP of 5 cmH₂O. The respiratory therapist drew an ABG which shows pH 7.35, PCO₂ 38, PO₂ 60, HCO₃ - 22 on an FiO₂ of 0.8 (80%). The patient's repeat chest x-ray is shown a "ground glass appearance". An echocardiogram performed earlier in the day revealed normal left ventricular function.

How do you explain his worsening oxygenation status?

What can you do to improve his oxygenation?

What other changes should you consider making in the ventilator settings?

If his oxygen saturation fails to improve despite being on high levels of support (i.e., FiO₂ of 1.0 and 20 cm H₂O of PEEP), what other options do you have for improving his oxygenation?

Answer 1

1. How do you explain his worsening oxygenation status?

The patient chest x-ray shows the glass appearance or opacity which means a pulmonary edema, his PaO2 and FiO2 ratio is 75 and echocardiograph report shows the normal ventricular function. The combination of x-ray, P/F ratio and ECG shows the acute respiratory distress and pancreatitis is the predisposing factor for ARDS.

2.What can you do to improve his oxygenation?

For improving the oxygenation is necessary to increase the PEEP pressure it helps in to open alveoli and prevent small airway closure which is effective in ARDS, pulmonary edema or alveoli hemorrhage.

It is important to remember high PEEP pressure may distant the capillaries and impair venous return, decrease cardiac output etc. to prevent these complications monitor the PaO2 and SaO2 of patient are indicative marker that tissue is getting enough oxygen.

3.What other changes should you consider making in the ventilator settings?

As patient has developed ARDS, strategies should be focus on the lung protection. In this the tidal volume increase 6ml/kg of patient weight. The goal is bring plateau pressure below 30cm H2O. if goal is not reached reduce the tidal volume about 4ml/kg of patient weight to achieve target plateau pressure.

4. If his oxygen saturation fails to improve despite being on high levels of support (i.e., FiO2 of 1.0 and 20 cm H2O of PEEP), what other options do you have for improving his oxygenation?

Several intervention can be done to improve the status of oxygenation. In some case the to improve mortality

1. Prone position is very effective (rotating prone position)

2. Inhaled pulmonary medication (it vasodilates the lung and increase the ventilation)

3. Use of paralytic medication such as vecuronium (to eliminate ineffective respiratory effort it increases oxygen consumption.)

These strategies are associated with risk.

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