Arterial blood gases and their use in respiratory disease
I had a letter published in the July 2008 issue of Australian Pharmacist, which was written with the aim of adding a few points to an earlier continuing professional development (CPD) article published in the journal.
In reference to Natalie Soulsby’s recent CPD article on arterial blood gases (ABGs) (Australian Pharmacist May 2008, page 404), indeed ABG interpretation is an area in which many pharmacists have limited experience, even in the clinical hospital pharmacy setting. Furthermore the results may be challenging to interpret, particularly without a comprehensive knowledge of respiratory physiology. There are a few points I’d like to add to those mentioned in the article.
Firstly, supplementary oxygen therapy (particularly in an intubated patient) can often actually cause a very high PaO2 reading. This is an expected consequence of the high alveolar partial oxygen pressure (PAO2), but can potentially be mistaken for a sampling/technical error by inexperienced personnel.
It may also be useful for pharmacists to be aware that one of the major indications for ABGs, besides determination of acidosis/alkalosis, is the characterisation of respiratory failure. Type 1 respiratory failure is hypoxaemia without hypercapnia (low PaO2, low or normal PaCO2) and implies a ventilation/perfusion (V/Q) mismatch – pneumonia, pulmonary oedema, pulmonary embolism, asthma, emphysema, etc.[1] Type 2 respiratory failure is hypercapnia (low PaO2, high PaCO2) and implies alveolar hypoventilation – obstructive/restrictive airways disease, reduced respiratory drive, neuromusculoskeletal disease, etc.[1]
Finally, it should be noted that the major limitation of pulse oximetry (in comparison with ABGs) is that it only measures the percentage oxygen saturation of haemoglobin. An anaemic patient, for example, may have normal oxygen saturation on oximetry but still be hypoxaemic.
Reference:
1. Longmore M, et al. Oxford handbook of clinical medicine. 7th ed. Oxford: Oxford University Press; 2007.
Citation: Po K. Arterial blood gases and their use in respiratory disease. Australian Pharmacist 2008;27(7):516.
Effects of 6-methyl-2’-methoxyflavone on wildtype and mutant GABAC receptors
I also discovered that I’d been credited as second author on a conference poster presented at the recent 3D at the Cove – Drug Design & Development conference, which was organised by the Royal Australian Chemical Institute. My contribution to this research was in helping to lay some of the groundwork, having synthesised 2′-methoxy-6-methylflavone and assessed its activity at α1β2γ2L GABAA receptors during my undergraduate honours project with the research group at the University of Sydney.
Citation: Premoli I, Po K, An SP, Johnston GAR, Chebib M, Hanrahan JR. Effects of 6-methyl-2’-methoxyflavone on wildtype and mutant GABAC receptors. 3D at the Cove – Drug Discovery & Development Conference; 2008 July 13–17; South Stradbroke QLD, Australia.
