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Citation

Gholamrezaei, A., Van Diest, I., Aziz, Q., Vlaeyen, J. W. S., & Van Oudenhove, L. (2021). Psychophysiological responses to various slow, deep breathing techniques. Psychophysiology, 58(2), [e13712]. https://doi.org/10.1111/psyp.13712

4 FUNDAMENTALS

1. Essential Background Material

This study examined differences in cardiovascular and emotional outcomes between slow breathing using pursed-lips (PLB), right-nostril-only (RNB), left-nostril-only (LNB), and resistance (RB).

There are many ways to perform slow breathing. We can change how we breathe (like listed above), the rate at which we breathe (e.g., 5 vs. 6 breaths/min), or breathe with different inhale-to-exhale ratios.

In general, they all seem to help cardiovascular function, reduce pain, and lessen stress and anxiety.

However, their specific effects might differ, and some methods might be better for some conditions (like hypertension) than others.

Therefore, this study aimed to examine how four common approaches (PLB, RNB, LNB, and RB) uniquely impact cardiovascular and emotional outcomes, focusing on which might be best for hypertension and pain.

2. What Did this Research Do?

Thirty-five volunteers partook in the study, aged 18 to 32. They were taught the four breathing techniques:

Pursed-Lips Breathing: Inhale through the nose and exhale audibly through pursed lips.
Left-or-Right Nostril-Only Breathing: Use the thumb to block either the left or right nostril and breathe exclusively through the other.
Resistance Breathing: Use a resistance device to breathe with a load of 10 cmH2O

The participants rested for 5 minutes for baseline measurements. Then, they performed each breathing technique for 3 minutes, with a 5-minute washout between each exercise.

For all methods, they breathed at a rate of 6 breaths/min using a 1:2 ratio, meaning the exhale was twice as long as the inhale (this comes out to a 3.3-sec inhale with a 6.6-sec exhale).

Because none of the participants had experience with breathing exercises, they only did each exercise for 3 min to make it reasonable to maintain the RB.

Physiological measurements were taken during the breathing (heart rate variability [HRV], blood pressure, etc.). Emotional outcomes were scored via questionnaires given after each breathing exercise.

3. What Were the Major Findings?

Important Overall Caveat

The findings only apply to comparisons amongst the different breathing conditions—not compared to the baseline. Usually, we’d like to see something like ‘blood pressure was “X” at baseline and “Y” after the breathing.’ But here, it’s simply between “X” during RB and “Y” during PLB or RNB, etc.

Here’s why that’s critical: systolic blood pressure actually went up during all of the breathing conditions compared to baseline—not the result we want, right? But, because the breathing conditions were given in random order, it’s impossible to know what caused it. For example, maybe RB caused blood pressure to go up, which carried over into the other exercises.

Of course, the results here are still significant. But, it would be nice to see them performed on separate days or with different groups of people to evaluate the changes from baseline, which are most important, in my opinion. But, alas, no study is perfect.

Overall, pursed-lips and resistance breathing had the best outcomes. Here are the specific results:

All four slow breathing techniques increased tidal volume and minute ventilation
Blood pressure was lowest during PLB, followed by RB
Blood pressure variability was highest during RB, followed by PLB
HRV was highest during RB, followed by PLB
Blood pressure and HRV were similar between LNB and RNB, which might be due to the short breathing time (3 min)
RB caused the most feelings of breathlessness and was the least enjoyable
PLB was the most enjoyable and provided the best sense of control
Some participants reported dizziness, sleepiness, cough, and nausea (it appears the cough and nausea were from the RB device)

A limitation of these results is that capnometry was not used. Since this was the participants’ first time performing slow breathing, they were likely overbreathing (this effect generally goes away after a few training sessions). This helps explain the feelings of dizziness in 6 participants.

Another limitation is that nasal-only breathing was not tested. Thus, it’s unclear if PLB would be better or worse than nasal-only slow breathing.

4. Why Do These Results Matter?

These results are helpful because there are many ways to perform slow breathing. Here we learn that pursed-lip exhales provide the most physiological and emotional benefits with no additional equipment or cost (keeping in mind the above caveat about nasal-only breathing).

However, we also learned that resistance breathing caused the most significant fluctuations in blood pressure and the highest HRV. Thus, RB could be a better overall “workout” for our cardiovascular systems, even though it causes the most unpleasant feelings.

1 BIG TAKEAWAY

Slow breathing using pursed-lip exhales or a resistance device both potentially improve cardiovascular health, but pursed-lips breathing is free, more pleasant, and provides a better sense of control.

1 PRACTICAL APPLICATION

The most straightforward application of this research is to use pursed-lips exhales during our slow breathing practice to improve our heart and emotional health.

If you have a resistance device, this research also shows the added benefit for HRV and blood pressure variation when slow breathing is performed with resistance.

Personally, I have used a resistance device for inspiratory muscle training.However, I used forceful, rapid breaths, which I did not particularly enjoy.Since reading this paper, I have started doing 3 minutes of slow breathing with resistance and find it more enjoyable.It’s too soon to know if it’s helping, but good to know there is an alternative way to perform resistance breathing.