Hypocapnia and mental stress can trigger vicious circles in critically ill patients due to energy imbalance: a hypothesis presented through cardiogenic pulmonary oedema.

The pathophysiologic significance of hypocapnia is strongly underestimated both in functional and organic diseases. Alterations of carbon dioxide levels immediately appear in the cytoplasm, causing abrupt pH changes. Compensatory mechanisms develop with latency, so intracellular alkalosis or acidosis can affect metabolism for hours/days. Hyperventilation alkalosis increases metabolic energy/O₂ demand, while ATP production is often reduced due to developing hypophosphatemia. A healthy organism serves the increased energy demand conveniently, as a consequence, the excitability of the corticospinal and neuromuscular systems grows. Functional diseases can occur due to increased membrane Ca2+ transients but tissues remain structurally unchanged. By contrast, a critically ill myocardium cannot satisfy the increased energy demand caused by acute hypocapnia. Vicious circles can occur, with cardiac forward and backward failure; pulmonary wedge pressure increases parallel with the lack of energy which can lead to pulmonary oedema and death. Hypocapnia can generate fatal vicious circles in several critical illnesses. Sympathicotonia and hypocapnia enhance arousal and make biological systems energetically unstable, thus vicious circles almost unavoidably occur. Somatic and psychic processes mutually influence each other, resulting in psychosomatic or somatopsychic disorders. The ability to provide energy supplies can be an important dividing line between organic and functional diseases.