Acute Hypercarbia in Chronic Obstructive Pulmonary Disease (COPD): Presentations to a New Zealand Emergency Department
Chronic Obstructive Pulmonary Disease (COPD) is the presence of chronic bronchitis or emphysema, which causes a progressive airway obstruction, characterised by airway hyperactivity (Palm & Decker 2003). In New Zealand there are increasing numbers of people presenting to the Emergency Department (ED) with COPD. COPD exacerbation results in hypoxia and respiratory failure that can be debilitating to the patient because the normal coping mechanisms fail and the patient can end up in a spiralling illness that has a high mortality rate if left un-treated. Hypercarbia is a direct result of hypoventilation either from failed coping mechanisms or respiratory failure from exhaustion. The question lies with, which patients have this hypercarbia during an exacerbation? Treatment patterns within the ED depend largely on the diagnosis of hypercarbia on presentation with an exacerbation of COPD.
A retrospective descriptive design was used to examine the records of all presentations to ED of patients with COPD over a 3-month period to determine whether there is a subset group of people who present with hypercarbia. Data from records were extracted using a specially devised data extraction tool. Of the findings there were 114 presentations, amongst those 114 presentations there were 71 individuals, a number of them presenting more than once within the three months. 80% of the 71 individuals have had a smoking history of which 53% were female. Of the 114 presentations, 76 had arterial blood gases taken during their ED presentation. Of these 76 presentations 30 had hypercarbia and 46 were non-hypercarbia. These 76 presentations involved 58 individuals, with some individuals presenting five times over the three-month period. Three groups emerged, some who were only hypercarbia (n= 18), some in the non-hypercarbia group (n=35) and 5 individuals who had presentations in both the hypercarbia and non-hypercarbia groups.
Data showed that there was no definable subset group of hypercarbia patients within acute exacerbations of COPD presenting to the ED according to the variables. However the sample of presentations (with a blood gas) found within the study suffering hypercarbia was much higher (31.1%) than anticipated. Further analysis showed that the hypercarbia group had a significant lower forced expiratory volume in one second (FEV1) and a combination diagnosis of emphysema or asthma and congestive heart failure. An implication to the clinician is that identification of hypercarbia within COPD exacerbation is problematically difficult until the late signs are shown with the individual. By that time effective treatment patterns may have changed from the initial presenting problem. Future areas of research within this field needs to lie within the community, when are these people starting the exacerbation and what leads them to progression presentation to the emergency department? Also we need to know whether these people are chronic sufferers of hypercarbia or presenting after a period of days exacerbation within their own home?