Surfactant complex

A low-fat and simultaneously high-carbohydrate diet can lead to conditions close to hypoxemia (a decrease in blood oxygen levels), especially in the presence of accompanying metabolic disorders.

The main source of energy — carbohydrates

With a high-carbohydrate diet, the body shifts to a glucose-dependent type of metabolism, where the primary source of energy becomes the oxidation of glucose. This process requires active participation of insulin and depends on continuous access to carbohydrates.

However, this type of metabolism has an important physiological drawback — low efficiency in oxygen consumption:

• The oxidation of 1 molecule of glucose yields 36-38 molecules of ATP, but requires 6 molecules of oxygen (O₂).
• At the same time, 6 molecules of carbon dioxide are produced, which creates an additional burden on the respiratory system.

Lower oxygen utilization compared to fats

In comparison, during the oxidation of fatty acids:

• More energy is produced (for example, the oxidation of palmitic acid yields 129 ATP),
• Less carbon dioxide is generated per unit of oxygen, meaning fat metabolism is more economical in relation to oxygen.

Thus, with a fatty type of diet (for example, during ketosis), the body better saturates tissues with oxygen, and the lungs function more efficiently, as less CO₂ is produced that needs to be removed.

The role of fats in maintaining surfactant structure

Surfactant — is a lipid-protein film covering the inner surface of the alveoli in the lungs, which prevents their collapse during exhalation. It is almost entirely composed of phospholipids, the synthesis of which is impossible without fats in the diet.

Against the background of a low-fat diet, the synthesis of surfactant decreases, which worsens:

• gas exchange in the lungs,
• blood oxygen saturation (hypoxemia), especially under increased load (for example, during infection or physical activity).

Insulin resistance and systemic inflammation

Prolonged consumption of large amounts of carbohydrates, especially fast ones (glucose, fructose, starches), provokes insulin resistance, fatty liver, and chronic low-grade inflammation.

As a result:

• the permeability of the alveolo-capillary membrane worsens,
• the risk of pulmonary edema increases,
• breathing efficiency decreases and the likelihood of hypoxemia increases — especially during viral or bacterial loads (for example, COVID-19).

What is a surfactant complex?

A surfactant (surface-active substance) — is a mixture of lipids and proteins produced by type II alveolar cells in the lungs. Its main functions are:

• To reduce surface tension in the alveoli, preventing them from collapsing during exhalation.
• To ensure normal gas exchange and elasticity of lung tissue.
• To protect the lungs from infections, serving as part of the innate immunity.

In children, especially newborns, the surfactant complex is still immature, and in weakened or frequently ill children, it may be damaged or depleted. It can also be depleted on a high-carbohydrate diet without sufficient fats and proteins in the diet.

How does a nebulizer work?

A nebulizer turns liquid medication into an aerosol that is inhaled through a mask or mouthpiece.

The most commonly used are:

• Bronchodilators (salbutamol, berodual);
• Glucocorticoids;
• Mucolytics;
• Saline solutions, mineral waters, and antiseptics.

Why can a nebulizer be harmful?

Irritation and destruction of surfactant. Many substances, especially hyperosmolar solutions, alcohol-containing preparations, or frequent use of antiseptics, can damage surfactant, making the alveoli vulnerable to collapse and microtraumas. This creates conditions for local inflammation and secondary bacterial infection, i.e., pneumonia.

Disruption of the natural defense of the respiratory tract. Frequent humidification of the airways with impaired mucociliary activity can dilute mucus, disrupting the barrier function. This increases the permeability of the epithelium and facilitates colonization by pathogenic microflora.

Formation of areas of stagnant fluid. With a weakened cough reflex and impaired mucus drainage due to immature bronchi, aerosol liquids can accumulate in the bronchioles and alveoli, promoting the development of a moist environment favorable for bacteria.

Why is it especially dangerous for children?

• Small diameter of the airways — more easily obstructed by inflammation or mucus.
• Weak mucociliary activity — poor sputum drainage.
• Immature immune system — weak control over bacterial flora.
• Deficiency or instability of surfactant — lungs collapse more quickly, disrupting ventilation.

Conclusion

Frequent use of nebulizers in children with an immature or weakened surfactant complex can lead to:

• Damage to the alveoli,
• Stagnation in the lungs,
• Disruption of natural drainage and cleansing of the airways,
• Increased risk of inflammation of lung tissue, i.e., pneumonia.

How do solvents and antiseptics affect surfactant?

Vapors of alcohols, chlorine-containing substances, ketones, aldehydes, and other volatile chemicals can destroy the lipid structures of surfactant in the following ways:

1. Chemical dissolution of lipids — alcohols and solvents have the ability to dissolve phospholipids and cholesterol, which make up the surfactant.
2. Denaturation of protein components — for example, SP-A, SP-B, and other proteins of the complex lose their structure under the influence of alcohols and aldehydes.
3. Oxidative stress — vapors of some antiseptics induce the formation of active oxygen species, damaging epithelial cells and disrupting surfactant production.

Liquid vapes (electronic cigarettes)

Vape liquids most commonly contain: propylene glycol, glycerin, flavorings, nicotine or its salts, and sometimes vitamins (for example, vitamin E acetate — particularly dangerous).

Damage to the lipid film. Glycerin and propylene glycol are hygroscopic substances — they attract water and dry out the mucosa and surfactant layer, making it unstable.

Formation of lipoid droplets. Some components of vape liquids (especially fat-soluble substances, such as vitamin E acetate) when inhaled deposit in the alveoli as fat-like inclusions, blocking the alveoli and disrupting surfactant function.

Inflammatory response. Inhaling vape vapors causes local inflammation, attracting neutrophils and macrophages, which further destroy the structure of surfactant by releasing enzymes and free radicals.

Recovery and the "maturation" period

After a single or short-term exposure to a toxic substance, the mucous membrane begins regeneration. The process of restoring surfactant in the upper respiratory tract and alveoli takes up to 15 hours. This is due to the fact that:

• producer cells (including goblet cells and type II pneumocytes) need time to synthesize and secrete new molecules;
• repair of damaged epithelium is necessary;
• local synthesis of lipids and proteins is required.

Why is hypoxia possible?

Without adequate surfactant:

• gas exchange worsens — alveoli are prone to collapse, and ventilation becomes uneven;
• resistance to breathing increases — due to dryness and irritation of the airways;
• vascular permeability increases — which can lead to mucosal edema and impaired oxygen diffusion.

This is especially dangerous during the first 15 hours after exposure, when the respiratory system has not yet had time to recover. During this time, symptoms such as:

• shortness of breath;
• dizziness;
• weakness;
• drowsiness;
• decreased saturation.