Breathing for Mental & Physical Health & Performance | Dr. Jack Feldman

KEYPOINTS

• 01

  We breathe to get oxygen in and, just as importantly, to get CO2 out to control blood pH

  Aerobic metabolism produces carbon dioxide, which shifts the blood's acid-base balance, and every cell is sensitive to pH. Inhaling works like pulling a balloon apart: the diaphragm contracts downward and external intercostals lift the ribs, lowering pressure in the alveoli so air flows in.

• 02

  Each breath starts in the pre-Bötzinger complex, a few thousand neurons in the brainstem

  Feldman's lab discovered this bilateral region, which initiates every inspiration and drives the motor neurons of the diaphragm and intercostals. Breathing muscles are skeletal and need neural input, unlike the heart. Airway smooth muscle is separate, and asthma is inappropriate constriction of it. Feldman says the evidence so far does not implicate the pre-Bötzinger complex in asthma.

• 03

  Active exhalation has its own oscillator, the parafacial nucleus

  Feldman admits they initially assumed one source for both inhale and exhale. That missed the fact that at rest exhalation is passive. Experiments in the early 2000s identified a second region that drives active expiration, as during exercise.

• 04

  Nose vs mouth and belly vs chest are largely beside the point for the core muscles

  At rest we default to nasal breathing; during exercise the mouth's larger airway moves more air. Diaphragm and intercostal contraction are almost 'agnostic' to whether the nose or mouth is open. We are obligate diaphragm breathers, and Feldman is agnostic about whether belly-out breathing matters for breathwork's effects on emotion and cognition.

• 05

  You sigh roughly every five minutes to reinflate collapsing alveoli

  People guess they sigh about once an hour, two orders of magnitude too low. The lungs hold about 500 million alveoli, each about 200 microns across and lined with fluid (surfactant), and surface tension makes them slowly collapse. A normal breath can't pop them open; a deep sigh, through nose or mouth, can. Lie quietly and you'll notice the automatic deep breath every few minutes.

• 06

  Sighs are triggered by bombesin-related peptides acting in the pre-Bötzinger complex

  Stress releases bombesin-related peptides from the hypothalamus, and stressed people sigh more. Injecting about $50 worth of bombesin directly into the pre-Bötzinger complex of rats took their sigh rate from 20–30 per hour to about 500 per hour. Ablating the receptor-bearing cells with a saporin conjugate stopped sighing. Lung function and overall health then deteriorated so badly the rats were euthanized, though secondary cell damage couldn't be ruled out.

• 07

  Breathing and emotion influence each other in both directions

  Kevin Yackle, with Lindsey Schwarz in Liqun Luo's lab, found pre-Bötzinger neurons that project to the locus coeruleus, the brain's arousal 'sprinkler system'. Ablating them made mice calmer, with EEG changes consistent with calm. Fear responses to faces, reaction time and pupil size all vary between inhale and exhale.

• 08

  Slow breathing practice dramatically reduced fear in mice

  With a startup grant from the NIH's complementary medicine institute (NCCIH), and after about three years of failed attempts, Feldman's lab slowed awake mice's breathing tenfold for 30 minutes a day over four weeks. In fear conditioning run with Michael Fanselow, these mice froze far less than controls, an effect Fanselow likened to a major amygdala manipulation. The work stalled when the grant and postdoc left.

• 09

  Breathwork may work by disrupting entrenched circuits

  Feldman's hypothesis is that brain oscillations tied to breathing help process signals, and that 30 minutes of altered breathing perturbs a stuck network, much as electroconvulsive therapy or brain stimulation do more bluntly. Repeated sessions could gradually 'fill in the rut' before the circuit rebuilds. He stresses this is still a hypothesis.

• 10

  Episodic hypoxia shows lasting benefits in research settings

  Work since the 1980s (David Millhorn) and now Gordon Mitchell at the University of Florida alternates about three minutes of low oxygen (typically 8%) with about five minutes of normal air. Ventilation then stays elevated for hours, with apparent benefits to motor and cognitive function. Feldman warns listeners not to try 8% oxygen, and notes breath holds differ because CO2 rises too.