A 44 year old man, with morbid obesity (175 cm tall and 210 kg) presents to the Emergency Department with respiratory failure. He is obtunded with an arterial blood gas (ABG) showing pH 7.25, Pa C02 82 mmHg and PaO2 53 mm Hg.

CXR reveals cardiomegaly and clear lung fields.

It is day 1. He is intubated  and  ventilated, and no  precipitant  was found  for his respiratory failure. CXR reveals an obscured left hemi-diaphragm and new infiltrates behind the heart.

(b) Outline your management

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College Answer

Ongoing  management   now  relies  on  reversal  of  factors   resulting  in initial  requirement  for ventilation  (predominantly   fatigue   by  exclusion),   removal  of  factors   keeping  him  ventilator dependent,  and   consideration   of   techniques   to   prevent  and   treat   left   lower   lobe  collapse consolidation.

Reversal  of  initial  fatigue   will  occur  with  adequate   provision  of  rest  (including   sleep,  and minimization of imposed work of breathing  [eg. an adequate  sized ETI (probably at least 8 nun), the use of the smallest amount of work to trigger the ventilator (eg. flow triggering), and the use of adequate amounts of ventilatory support (eg. pressure support, or similar  mode)]. The patient will need to  be awake  as  much  as  possible  during  the  day  (using  appropriate  sedation  regimen  if necessary overnight).

Left lower lobe collapse  of some form  may be minimized  by the use of higher levels of PEEP, appropriate  posturing  (mcluding  semi-prone   and  prone). and  the  at  least  intermittent   use  of adequate tidal volumes (eg. sigh or  IMV  breath). The possibility  of nosocomial  pneumonia  and other  differential  diagnoses  (eg.  pulmonary  emboli)  needs  to  be  entertained, and  excluded  if appropriate.

Discussion

Supportive management

  • Nutrition, low carb and high fat.
  • Analgesia and sedation as required to maintain comfort rather than obtundation
  • Thromboprophylaxis
  • ulcer prophylaxis
  • appropriate ventilator settings to minimise work of breathing
  • increase PEEP to reinflate atelectatic left base
  • Posture 45 degrees, sitting up
  • When supine, rotation therapy (alternate between left and right recovery position)
  • Consider pneumonia and commence antibiotics if appropriate