Go With the (Peak) Flow


A Clinical Swallow Evaluation is a series of screens that we use to determine if the patient requires more testing or not.

Let’s face it, whether we like it or not, insurance likes objective data, including numbers indicating a deficit or no deficit.   Peak Flow is a tool that gives us objective numbers to input into our reports.

What is Peak Flow?

A Peak Flow meter measures how fast air is expelled from the lungs in one fast blast.  A Peak Flow meter can be very beneficial to those with asthma.

Peak Flow also gives us information on the cough reflex and function of the cough, in turn, allowing us to determine patients that are at risk for penetration and/or aspiration.

Why do we care about coughing?

Coughing is a mechanism of airway clearance that adds to normal
ciliary function comprised of three events

  • Inspiratory effort
  • Followed by rapid vocal fold adduction
  • Contraction of the expiratory muscles

Respiratory Muscle Strength Training (RMST)

You can also use Peak Flow to determine baseline for RMST and to measure outcomes throughout your therapy using RMST.

So what has research told us about measuring Peak Flow?

We measure using PEF or Peak Expiratory Flow or PEFR Peak Expiratory Flow Rate.

  • Smith-Hammond, et al 2009-Peak flow identified 82% of aspirators
    (stroke patients) at PEF <2.9 L
  • Pitts, et al  2010-Peak flow identified 86% of aspirators (Parkinson’s) at
    PEF <5.2 L
  • Suarez, et al 2002 identified 74% aspirators (ALS) at
    <4.0 L
  • Plowman, et al 2016 identified voluntary cough airflow in patients with ALS at risk for penetration/aspiration

Peak Flow meters can be purchased to use.

PF 1        PF 2

A less expensive Peak Flow model will have a plastic piece on the side that moves as the person exhales or coughs into the device.   You can determine the PEF or PEFR by having the person exhale or cough into the device 3 times and figuring the average rate.

PF 3

You can also purchase a digital device which will give you a more accurate reading, but will cost you a bit more.

These devices can be purchased on Amazon or a medical supply store.   You can often purchase disposable mouth pieces so that you can use the device with multiple patients after cleaning.


Gregory, S. A. (2007). Evaluation and management of respiratory muscle dysfunction in ALS. NeuroRehabilitation22(6), 435-443.

Hammond, C. A. S., Goldstein, L. B., Horner, R. D., Ying, J., Gray, L., Gonzalez-Rothi, L., & Bolser, D. C. (2009). Predicting aspiration in patients with ischemic stroke: comparison of clinical signs and aerodynamic measures of voluntary cough. Chest135(3), 769-777.

Pitts, T., Troche, M., Mann, G., Rosenbek, J., Okun, M. S., & Sapienza, C. (2010). Using voluntary cough to detect penetration and aspiration during oropharyngeal swallowing in patients with Parkinson disease. Chest138(6), 1426-1431.

Plowman, E. K., Watts, S. A., Robison, R., Tabor, L., Dion, C., Gaziano, J., … & Gooch, C. (2016). Voluntary cough airflow differentiates safe versus unsafe swallowing in amyotrophic lateral sclerosis. Dysphagia31(3), 383-390.

Suárez, A. A., Pessolano, F. A., Monteiro, S. G., Ferreyra, G., Capria, M. E., Mesa, L., … & De Vito, E. L. (2002). Peak flow and peak cough flow in the evaluation of expiratory muscle weakness and bulbar impairment in patients with neuromuscular disease. American journal of physical medicine & rehabilitation81(7), 506-511.










8 thoughts on “Go With the (Peak) Flow

  1. Thank you this is helpful! I am an SLP hoping to use this in the hospital setting, I was wondering if you have the values of peak flow that would indicate possible aspiration risk?

    1. There’s not really a scale that indicates aspiration risk. You’re more looking at strength of the cough and want that to fall in the normal ranges. The cough strength is what you want to prevent aspiration.

  2. “You can also use Peak Flow to determine baseline for RMST and to measure outcomes throughout your therapy using RMST” does that mean PEFR can be used to determine a patient’s MEP and inform selection of threshold device? If so, would you be willing to explain how? Thank you

    1. MEP would only be if you’re working on inspiration. If you have an inspiratory peak flow device. I’ve only used expiration, I’ve personally not had to work on inspiration. I’ve typically used peak flow and EMST to increase cough.

  3. Thank you for your quick response. By MEP I meant to discuss Maximum Expiratory Pressure. I am not sure if the patient meets the required 5cmH2O (Philips device) or the 30 cmH2O (EMST150). I purchase a peak flow meter but am unsure of how that data can support the selection of the appropriate device (either of the two mentioned above). I may have misunderstood you to say that one can determine the baseline for EMST with peak flow meter? I am curious if you used a calculation to convert the L/s or L/m (flow) to cmH2O.

    1. Let me start out by saying, math is my enemy. I’ve use the EMST and often use that to determine where the patient needs to work. I believe the literature for EMST has the calculations to figure. I’ll admit, I always have to look it up! Haha! For me, I use peak flow to determine a baseline, looking at average ranges for age and sex and use the peak flow for progress, has the patient increased their range which can indicate a more productive cough. So I would assess using peak flow, assess using the device and then use the device settings to determine therapy, peak flow for progress. I honestly haven’t seen or used the Philips device but would imagine you can use either device for a patient. If they can’t use the EMST device a lot of people will start with the Breather device.

  4. Hi, I think I understand what Emily in the above comment was asking as I have been searching the literature this afternoon. I just acquired some simple peak flow meters, and my impression was that I could use the meter reading, in L/min, to help determine an appropriate RMST device. In other words, if their peak flow was say, 300L/min, would that indicate an EMST lite is a better starting point. Is there a correlation between L/min and the cm/H2O for the breathers? I’m not trying to get “mathy” I just want to understand *how* you use the peak flow to determine baseline for RMST, as stated in the article. Perhaps it is just for pre/post objective data related to progress?

    1. Basically, you’re taking the peak flow meter and determining where that patient is prior to therapy. What level are they? There is a sheet, typically included with the meter that will tell you what is the normal range by age and gender. After your therapy, RMST, where has the patient improved, as far as on the peak flow meter. They should be able to to maintain a higher number on the meter after therapy.

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