Video
COPD: Inhaler Selection and PIF
Factors to consider when selecting an appropriate inhaler device to treat a patient with chronic obstructive pulmonary disease, and the role of measuring peak inspiratory flow to help determine one’s disease severity.
Neil Minkoff, MD: That’s such an important aspect in terms of balancing what’s right for each patient. I’m going to pull Dr Drummond in here to comment on that further. We started touching on the idea of tailoring the right medications to the right patient and how you make those decisions. Would you tell us how you think about choosing the right inhaler or inhale device for a patient with COPD [chronic obstructive pulmonary disease]?
M. Bradley Drummond, MD, MHS: Absolutely. The unique aspect of COPD is that, unlike a pill, you’re prescribing both the device and a molecule or molecules—the medicine you’re trying to deliver to the lungs. You almost have to disassociate these two when you consider how you’re going to prescribe something for a patient. I do think the delivery device is as important as the molecule or molecules that you’re trying to deliver to the lungs.
We have 4 fundamental options with how we can deliver medications to the lungs. The first is the metered-dose inhaler, which is basically pressurized gas to deliver molecules to the lungs. The second is dry powder inhalers, where the patient has to inhale a dry powder containing the molecule. The third is a soft mist inhaler, which delivers the molecules through a flow-independent mist. And finally, the nebulized therapies, which use compressed air or oxygen to suspend liquid solutions into small aerosol droplets that are then inhaled. When we start thinking about how we’re going to prescribe these medicines to patients, we have to consider both the molecule or molecules, as well as these different factors related to the different device characteristics.
This is where peak inspiratory flow [PIF] comes in because it’s relevant to dry powder inhalers because they are flow-dependent devices. Patients must generate sufficient inspiratory flow to disaggregate this powder to a small enough size to deliver to the distal parts of the lung. Because each device has different resistances, the challenge is that how hard you have to inspire, or how hard that flow has to be, varies.
Our work has actually shown that around 40% of outpatients aren’t able to generate sufficient peak inspiratory flow for the device that we’re prescribing them. A lot of work has gone in to understanding how we can identify or predict the peak inspiratory flow in these patients short of actually measuring it. The data support that it’s difficult to predict who this is. It’s not simply a marker of their low lung function because that’s a measure of an expiratory maneuver, and we’re talking about an inspiratory effort. It doesn’t seem to correlate consistently with low lung function. Other factors, like shorter stature and female sex, seem to be associated with reduced peak inspiratory flow in cohort studies.
The only way to know, frankly, is to measure it rather than guess. Peak inspiratory flow is important also because we’re beginning to see that there may be associations with health care utilization. There have been a couple studies, one multicenter and one single center. The single center study seemed to support that individuals with reduced peak inspiratory flow near or at the time of discharge from a COPD exacerbation have a higher risk of being readmitted to the hospital. So whether this could actually be a predictor of not only informing how we select our therapies for our patients, but also what their clinical course may be like, it is an area of interest for many of us.
Neil Minkoff, MD: I want to come back to some of the differences in the devices. I want to bring Mr Hess in, but let me ask one more follow-up question. When somebody like me thinks about these, we tend to think about mild cases of COPD versus a later stage or a more complicated case. Do you actually classify patients that way? How does measuring something like PIF help with that classification or diagnosis?
M. Bradley Drummond, MD, MHS: Yes. Each of the individual inhalers does have what’s thought to be an optimal or sufficient threshold for their inspiratory flow measurement. The general consensus is that if [the patients are] able to generate a number above that threshold, then they’re likely able to deliver that drug sufficiently down into their lungs vs individuals who are not able to generate that sufficient or adequate inspiratory flow.
And so we can think about some binary areas where patients are either able or not able to do sufficient flow, and we can incorporate that into our characterization of their ability to use that inhaler.
Neil Minkoff, MD: Mr Hess, you spend a lot of time trying to tailor therapies to different patients. When you hear about these 4 classifications, who are the kinds of patients you think match up well to the different types of devices and how do you characterize it?
Michael Hess, MPH, RRT, RPFT: It really depends. Each of these devices has a particular set of pros and cons, and it’s important to match the patient’s preferences and their abilities with each individual device. For example, the traditional metered-dose inhaler, what most people probably think of when you hear the word inhaler, works very well. It’s very portable, as it doesn’t require any electricity to use, but it does require a fair bit of hand-breath coordination. You have to be able to inhale at the appropriate rate at the appropriate time. Dry powder inhalers take that coordination requirement out. But as we’ve been talking about, you have to have a certain amount of inspiratory flow in order to disaggregate that powder and get it to where it’s going to be effective.
The slow mist inhalers also work very well. They don’t require as much coordination. I would argue they still require some, because if you don’t inhale at the right time, you may hit the back of your throat and trigger a cough. It can also be a little bit more complex to put together. Then we have nebulizers which are arguably the traditional standard, particularly for folks who are having an exacerbation. They don’t require any special inspiratory technique, particular flow, or particular coordination, but they take longer, which can be a big factor when somebody is doing their medications at home. They also require a little bit more maintenance to the equipment. They generally require a plug so they’re not as portable as some of the other handheld inhaler options.
This activity is supported by an educational grant from Boehringer Ingelheim.
