Does holding your breath during an injection make it less painful?

"Hate injections? Holding your breath can make the pain of jabs more bearable," the Mail Online reports. A team of Spanish researchers mechanically squeezed the fingernails of 38 willing volunteers to cause them pain.

For one round of experiments, the group were told to hold their breath before and during the pain squeeze. In the second round, they had to breathe in slowly while the pain was applied. Those holding their breath reported slightly lower pain ratings overall than those breathing in slowly.

The hypothesis underpinning this technique is that holding your breath increases blood pressure, which in turn reduces nervous system sensitivity, meaning you have a reduced perception of any pain signals.

But before you try this out, it's worth saying the pain perception differences were very small – a maximum 0.5 point difference on a scale from 0 to 10.

Also, the pain scores of the experimental breathing styles weren't compared with normal breathers, so we don't actually know if they were beneficial overall at reducing pain perception, only relative to one other.

We wouldn't advise changing your breathing habits in an attempt to avoid pain based on the results of this study.  

Where did the story come from?

The study was carried out by researchers from University of Jaén in Spain, and was funded by the Spanish Ministry of Science and Innovation.

It was published in the peer-reviewed journal, Pain Medicine.

Generally, the Mail Online reported the story accurately. In their article, the lead study author explained that holding your breath won't work for an unexpected injury, such as standing on a pin or stubbing a toe. But it might work if you start holding your breath before the pain kicks in – for example, anticipating the sting of an injection.

The Mail added balance by indicating other scientists were critical of the findings. They said the pain reduction was very small, and pointed out that holding your breath might make your muscles more tense, which could worsen pain in some circumstances, such as childbirth.  

What kind of research was this?

This human experimental study looked at whether holding your breath affects pain perception.

The researchers explain that holding your breath immediately after a deep inhalation slows your heart rate and increases your blood pressure. This stimulates pressure-sensing receptors called baroreceptors to send signals to the brain to reduce blood pressure.

This happens through reduced activity of the sympathetic nervous system, which is involved in the "fight or flight" response to danger. When working as it should, this feedback loop ensures blood pressure doesn't get too high.

The researchers say the dampening down of this part of the nervous system might also reduce sensitivity to pain. In this study, the researchers wanted to test their theory that increasing your blood pressure through holding your breath would reduce your perception of pain.   

What did the research involve?

Researchers used a machine to squeeze the fingernails of 38 healthy adult volunteers at different pressures to stimulate pain. Before the squeeze, the group were told to inhale slowly or to hold their breath after a deep breath in.

The researchers analysed ratings of pain in the two breathing styles to see if there was a difference. Volunteers were pre-tested to find a nail squeeze pressure they found painful and three personalised pain intensity thresholds.

Two breathing styles were tested and compared in each person. One involved breathing in slowly for at least seven seconds while the pain was applied. The other involved inhaling deeply, holding your breath while the pain was applied, before exhaling for seven seconds without actively forcing the breath out.

Both groups practised the breathing styles before the experiment began until they were confident they could do it properly. Once they had established their breathing, each volunteer had one fingernail mechanically squeezed for five seconds. After the squeeze, participants could breathe normally.

They were asked to rate the pain on a Likert scale ranging from 0 (not at all painful) to 10 (extremely painful). The experiment was repeated on the same person using three pain intensity thresholds for each breathing condition.

Volunteers knew the experiment was about pain and breathing, but they were not told which breathing experiment the study team expected to work. 

What were the basic results?

Ratings of pain intensity were consistently higher in the slow breathing group compared with the breath-holders. This held true for each of the three pain intensities tested.

Both breathing styles slowed heart rates, but this happened a little quicker, and the difference was larger, in the breath-holding condition. 

How did the researchers interpret the results?

The researchers concluded that, "During breath-holding, pain perception was lower relative to the slow inhalation condition; this effect was independent of pain pressure stimulation."

On the implications of their findings, they said: "This simple and easy-to-perform respiratory manoeuvre may be useful as a simple method to reduce pain in cases where an acute, short-duration pain is present or expected (e.g. medical interventions involving needling, bone manipulations, examination of injuries, etc.)." 

Conclusion

This small human experimental study used a fingernail-squeezing machine to cause pain to 38 willing volunteers. It found those instructed to hold their breath before the pain stimulus consistently rated their pain lower than those told to breathe slowly.

The difference between the two breathing groups was very small, although statistically significant. The biggest pain difference seen looked to be less than 0.5 points on a 10-point scale. How important this is to doctors or patients is debateable.

Similarly, the study compared two artificial breathing conditions against one another. They did not compare these against pain scores in people breathing normally throughout. This would have been useful, as it would give us an idea of whether one or both of the breathing types were any better than breathing normally.

On this point, the Mail Online reported that, "On a scale of 1 to 10, the pain experienced by volunteers fell by half a point from 5.5 to 5 when they held their breath". It wasn't completely clear whether they were talking about the difference between the two groups, or the absolute pain reduction experienced related to normal breathing.

This figure wasn't clear in the published research, so may have come from an interview. If true, it again highlights the rather small reduction in pain found.

The volunteers knew they were taking part in a pain study related to breathing. Participants' general expectations about the likely effects of the two breathing conditions therefore might have biased the results. Larger studies involving study blinding and randomisation would reduce the chance of this bias and others.

Overall, this study shows that changing your breathing pattern might affect your pain perception – but at such a small level that it might not be useful in any practical way.

There may be other dangers in holding your breath in an attempt to control pain. For example, you might feel lightheaded and pass out, or tense your muscles, which can hamper the ease of injections.

If you are worried about having an injection, you should tell the health professional before they give you an injection. They can take steps to make the experience less distressing.