Respiratory Medicine in Dundee
Case of the Week #2
 What's wrong with this young lady? |
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Discussion Points:
There is gross emphysema with large bullae present bilaterally. The diaphragms are flattened, and there is hyperexpansion of the lung fields.
This is compensated type 2 respiratory failure
Leave them alone! The NIV is doing it’s job well currently: there is no hypoxaemia; there is no acidosis.
Given this lady’s young age, she should be tested for Alpha-1-anti-trypsin deficiency. Click the “more” link below to see more information on A1AT deficiency.
Alpha-1-Anti-Trypsin Deficiency
Incidence | 4 % of the European population carry the PiZ allele. 1 in 2000 are homozygous PiZZ. |
Age | Presents in childhood with fulminant liver failure, and adulthood with respiratory failure secondary to bullous emphysema |
Sex | Males and female affected equally |
Geography | More common in northerly latitudes. |
Predisposing Factors | Genetic inheritance. Allelic nomenclature:PiM - Normal PiZ - Affected. Homozygous PiZZ most severely affected. Emphysema presents much earlier in adults who smoke. |
Macropathology | Present with fulminant liver failure and chronic type 2 respiratory failure |
Micropathology | Panacinar emphysema |
Symtoms and Signs | Insidious onset of breathlessness, rapid development of end stage type 2 respiratory failure, particularly in smokers |
Treatment | Standard therapy for COPD. Experimental treatments with synthetic forms of Alpha 1 anti-trypsin protein. |
Prognosis | Varied. Those with PiZZ genotype often develop cirrhosis in adolescence, requiring hepatic transplant. Non-smokers with PiMZ genotype may have no symptoms until late in life. Smokers with the PiMZ genotype typically develop emphysema in the 4th and 5th decades. |
Re: Case no. 2 of the week.
You say under the answer for “what should you do with the settings on the NIV machine?” that there is no hypoxaemia. Can you explain this given that her PO2 is 8.3 kPa from the ABG. Is hypoxaemia strictly defined as a PaO2 of <8 kPa?
If there is hypoxaemia with no acidaemia should the inspiratory pressure on the BIPAP be increased?
Many thanks
A PO2 of 8.3 is perfectly reasonable for anyone with chronic type 2 respiratory failure. So, for this patient, there is no hypoxaemia.
If there is no hypoxaemia and no acidaemia you should consider removing the NIV. Remember that BIPAP is a trade name. Much like not all all vacuum cleaners are Hoovers, not all NIV machines are BIPAP; we use VPAP machines.