A 44-year-old man with morbid obesity (BMI 68 kg/m2 ) presents to the Emergency Department with respiratory failure. He is obtunded with an arterial blood gas (ABG) showing
- pH 7.25,
- pCO2 75 mmHg (10kPa),
- PO2 53 mmHg (7 kPa),
- HCO3 32 mmol/L on FiO2 0.3.
Chext X-Ray reveals cardiomegaly and clear lung fields.
Describe your management of this problem for the first 24 hours.
Management includes simultaneous resuscitation and assessment with history and examination,
investigations, (appropriate and interpreted) and ongoing fluid therapy (including triage, monitoring,
pharmacology and non-pharmacological interventions).
ABG information given confirms type 1 and type 2 respiratory failure.
Cardiomegaly may relate to AP portable semi-erect film but cardiomyopathy and ?pericardial effusion
should be considered.
Other causes of decreased conscious state in addition to hypercapnia and hypoxia should be
considered, such as drug toxicity, metabolic / endocrine / electrolyte disturbances.
Resuscitation consists of ensuring adequate airway, ventilatory support as needed, ensuring
adequate circulation and assessment of other, readily reversible causes of decreased conscious state
such as opiates, hypoglycaemia.
Airway support may be by simple measures such as positioning and airway adjuncts as needed and
conscious level permits (nasopharyngeal airway better tolerated than oropharyngeal).
NIV if maintaining airway and protective reflexes present but invasive ventilation if NIV not appropriate
Assessment of difficulty of intubation. Invasive ventilation potentially hazardous given morbid obesity.
Appropriate ventilator settings accepting high peak pressures needed to overcome chest wall mass
and intra-abdominal pressure (transpulmonary pressure [Palveolar – Pintrapleural pressure] will be
History and examination should suggest/exclude any diagnoses including: ischaemic heart disease,
cardiac failure (left and right), COAD, venous thromboembolism, respiratory tract infection, CNS
disorder (Stroke, haemorrhage), diabetic conditions, any other endocrine problems eg
hypothyroidism, and potential for drug related problems.
Simple investigations should be ordered and reviewed to assist above differential diagnosis and assist
treatment (FBC U&E, blood sugar, ECG)
Specific treatment should be directed at clinical suspicions and continued supportive treatment with
ventilatory and haemodynamic support,
General treatment of ICU patient with nutritional support, ulcer prophylaxis, thromboprophylaxis and
sedation/analgesia with modification of doses for morbid obesity.
Additional considerations for management of morbidly obese ICU patient - special beds, hoists,
difficulty with procedures, pressure area care, increased risk of complications.
This question does not seem to stem from any specific guidelines.
Let us deconstruct the gospel answer.
"Management includes simultaneous resuscitation and assessment with history and examination,
investigations, (appropriate and interpreted) and ongoing fluid therapy (including triage, monitoring, pharmacology and non-pharmacological interventions). "
This can be viewed as a "motherhood statement". No examiner would disagree with the fact that management should include triage, history, examination, investigations, and simultaneous management of emergent problems.
The next parts of the answer deal with the ABG result. Yes, its acute on chronic hypercapnic respiratory failure, and the patient is hypoxic; but could there be any other reason for this obtundation?
Drug toxicity, metabolic endocrine and electrolyte disturbances are mentioned.
The answer then moves on to airway support and NIV, mentioning the use of simple airway adjuncts and the airway reflex protection caveat for NIV before discussing the difficulty of intubation.
Thus, one might say:
- - Assess airway patency;
- - if airway is not protected, introduce simple airway devices and assess their effect on airway patency
- - if airway reflexes are intact, commence NIV paying attention to the dangers of the high pressures which will be required in an obese patient
- - if airway reflexes are intact, assess for intubation and solicit expert help for intubation.
- - assess any rapidly reversible causes of obtundation such as opioid intoxication and hypo/hyperglycaemia
- - if no rapidly reversible cause is found, mechanical ventilation must commence while the process of investigation continues
- - once airway patency is established and some form of mechanical ventilation is in progress, other causes for the reduced level of consciousness must be pursued and managed, including intracranial causes, thromboembolism, electrolyte abnormalities, cardiac failure, hypothyroidism etc.
- - at the same time, management of the possible causes of hypercapneic respiratory failure must commence (therapies specifically directed at COPD and OSA)
- - at the same time, standard management protocols for the care of an obese ICU patient must be followed, including thromboprophylaxis, pressure area care, the use of specialised bariatric equipment, and ulcer prophylaxis.
One struggles to find references for something like this.
l can only refer to the Oh's Manual chapter 26 (acute respiratory failure in COPD).