Standing up while deeply inhaling can cause a blood pressure fall?

Question

Someone told me a few months ago of a technique to stop hiccups. When I followed the simple instructions given to me at that time it was extremely effective.

Recently, I tried to reproduce the technique:

1. breathed in while squatting down, placing the knees against the chest;
2. slowly breathed out while standing up with the arms stretched forward;
3. hold the breath for about one minute.

The hiccups didn't stop this time, so I thought I must have mistaken the breathing order. Therefore I tried reversing:

1. breathed out while squatting down;
2. slowly breathed in (until full lung capacity) while standing up;

Once I stood up, I immediately felt symptoms described in Orthostatic hypotension (found this page through a comment to another question similar to mine):

• dimmed vision with flashes and momentary blindness;
• generalized numbness/tingling and fainting;
• headache.

I squatted down again after approximately 3-5 seconds and the symptoms subsided (with the exception of the headache, which lingered for a while), and I still had the hiccups.

I gave up on the technique and later managed to stop the hiccups while having some yogurt in my mouth and drink it with the head down (close to my knees).

I'm assuming that in the second sequence the blood flows rapidly to the legs and at the same time to the diaphragm to help filling the lungs, causing a blood pressure fall, and the head, in this case, is primarily affected. I'd like to confirm if this makes any sense.

Answer 1

There seem to be a couple different issues under discussion. I will attempt to explain the relevant physiology and respond to the query in the title.

1. Hiccup interruption. Most physical techniques involve stimulating efferent vagal tone. These are effective.¹ Commonly used methods (similar to those used to abort supraventricular tachycardia) include:

   • cold stimulation of the nasopharynx (upside down with ice water in the mouth will do it),
   • carotid sinus massage, and
   • Valsalva maneuver.

   In theory, a sudden increase in afterload could also stimulate vagal tone via baroreceptors. When you describe squatting and breath-holding maneuvers, this is reminiscent of techniques that affect afterload and preload,² namely:

   • squatting (vs. standing) increases both preload and afterload;

   • deep inspiration increases preload to the R heart but decreases venous return to the L heart and thus systemic (including carotid sinus) pressure.

   In theory, squatting and exhaling would be the combination that most effectively increases afterload and could theoretically trigger a vagal response. However, I’m not aware of any data suggesting that these are practically effective for termination of hiccups.

2. Orthostasis. You have outlined an effective method of temporarily depriving your brain of adequate blood flow and eliciting symptoms of orthostatic hypotension.³ This is due to decreased preload to the L heart, most marked upon inspiration occurring simultaneous with standing from the squatting position. This tends to trigger the sympathetic nervous system rather than the parasympathetic. It is the latter that is associated with vagal tone helpful for terminating hiccups.

In summary: Yes, standing up while inhaling will cause systemic blood pressure to fall with resulting decreased cerebral perfusion. This is generally unpleasant and does not come highly recommended. This is unlikely to be effective for hiccups.

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_{1. I have elsewhere outlined the physiology of hiccups (=singultus), which provides some background on why such maneuvers are effective.}

_{2. Techniques known to every med student from their application to dynamic auscultation of heart murmurs.}

_{3. Apologies for the self-promotion, really, but I also answered a question about the visual component of this syndrome, one of the lesser appreciated aspects.}