A pharma sector-sponsored study, published online in the journal Thorax, shows that shifting from a metered-dose inhaler to a dry powder model for maintenance therapy more than halves the carbon footprint of people with asthma, and without causing deteriorating their condition.
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This shifting would be a suitable and valuable “green” option for the majority of patients who can safely handle their condition at home and should be extensively encouraged, conclude the scientists.
Under the 1987 Montreal Protocol agreement, the use of chlorofluorocarbons (CFCs) in aerosol propellants was banned due to their influence on global warming.
Nevertheless, while the hydrofluorocarbons that substituted CFCs in pressurized metered-dose inhalers do not reduce the ozone layer, they are powerful greenhouse gases, say the scientists. Emissions from this source are responsible for 3–4% of the overall carbon footprint linked with healthcare in the United Kingdom.
The scientists were keen to compare the possible impact on carbon footprint and symptom control of changing the maintenance therapy to a dry powder inhaler and carrying on with a metered-dose inhaler comprising hydrofluorocarbon propellant.
They performed a secondary (post-doc) analysis of data from a group of patients who had participated in the Salford Lung Study in Asthma. This comprised a wide range of 4,000 patients with asthma who were handling their condition at home and strictly reflected standard UK clinical practice.
Adults with asthma on standard maintenance therapy to regulate their symptoms were randomly allocated to either begin using a dry powder inhaler (1,081; “switch group”) or to continue using a pressurized metered-dose inhaler (1,151; “usual care”) for a span of 12 months.
Both the groups were matched for symptom severity and average age (49). Symptom control was evaluated at the commencement of the study, and after 12, 24, 40, and 52 weeks, using a validated test (Asthma Control Test).
Yearly CO2 emissions in kilograms were measured for the total number of maintenance (preventer and rescue) inhalers prescribed throughout the 12-month study period.
Patients were permitted to change inhalers during the course of the study, but the majority stuck with the type to which they had been allotted: 80% stayed on a metered-dose inhaler in the usual care group and 85% stayed on a dry powder inhaler in the switch group.
Scrutiny of the data revealed that, after a year, yearly CO2 emissions for each person in the “switch” group were less than half those of the regular care group:108 kg vs. 240 kg.
Asthma control was better in both treatment groups during the course of the study. By week 24, the odds of reacting well to treatment in the switch group were roughly double those of the usual care group, and this variance continued over the complete 12 months.
The switchers were given about one less rescue salbutamol metered dose inhaler than those who continued on usual care: 7.2 vs. 8.
The team quantified that the yearly carbon footprint saving for each patient in the switch group was 130 kg CO2 emissions.
Scaling this up “would represent approximately 40% of the total carbon footprint due to [metered dose inhalers] in the UK,” they suggest.
“The potential for carbon saving could be much greater if patients also switched to a rescue medication administered via a [dry powder inhaler],” as the majority of patients in this study used pressurized metered-dose rescue inhalers, “typical of usual care in the UK,” they add.
In a linked podcast, lead author Professor Ashley Woodcock states that patients with asthma are frequently uninformed of the effect their inhalers have on the environment.
Each puff of a [metered dose inhaler] is equivalent to driving 1 mile in a family car, so one inhaler is close to driving 200 miles… but a powdered inhaler is about a twentieth of that.
Ashley Woodcock, Study Lead Author and Professor
This is an “easy win” for the NHS to decrease its carbon footprint, he recommends, particularly because the United Kingdom is quite an outlier in its use of high carbon inhalers, he states.
Low-carbon inhalers are mainly used in Europe. The large carbon footprint due to the usage of hydrofluorocarbon propellants in metered-dose inhalers in the UK is three times more than that in Europe.
Where possible, shifting these patients to powder inhalers would “make a big difference to our carbon footprint,” he suggests.
Essentially this is about evolution, not revolution. In discussion with patients, healthcare professionals should have a conversation about the environmental footprint of their inhalers.
Ashley Woodcock, Study Lead Author and Professor
The researchers conclude: “The results of this analysis support the growing calls from official bodies that, where possible, switches… to low carbon-impact alternatives should be sought. Together with the role of pharmaceutical companies in producing accessible alternatives, prescribers, pharmacists, and patients should be made aware of the significant differences in the global warming potential of different inhalers.”