Harm caused by inhalation of toxic substances: from the acute event to the risk of fibrosis

DAMAGE FROM INHALATION OF TOXIC SUBSTANCES:
FROM ACUTE EVENTS TO THE RISK OF FIBROSIS

Events like the recent tragic one in Crans-Montana bring to the forefront an often overlooked issue: what are the true respiratory consequences of acute inhalation of toxic substances?

In common perception, these exposures are associated with immediate, sometimes serious, but transitory, damage. In reality, the most recent literature suggests that, in some cases, the impact can extend well beyond the acute phase, leading to persistent sequelae and, in the most severe cases, actual fibrosis.

What happens in the lungs after toxic inhalation

The type and severity of damage depends on several factors:
• nature of the substance (irritant gases, fumes, chemical vapors)
• concentration
• duration of exposure
• individual vulnerability

Gases such as chlorine or ammonia cause direct damage to the respiratory epithelium, while more complex exposures (such as combustion fumes) trigger an intense inflammatory response associated with oxidative stress.

The result is often a pattern of diffuse alveolar damage, similar to that observed in ARDS, with:
• increased vascular permeability
• alveolar edema
• impaired gas exchange

The acute phase: not everything always resolves

Clinically, patients may present with:
• dyspnea
• persistent cough
• bronchospasm
• hypoxemia

Imaging (especially high-resolution CT) frequently shows diffuse infiltrates or areas of "ground glass."

In many cases, especially with less severe exposures, complete regression is observed. However, this is not always the case.

When the damage persists

In a proportion of patients, the inflammatory process does not completely resolve, but evolves into a phase of damage organization.

This is where one of the most interesting, yet still poorly defined, areas of modern pulmonology emerges: the transition from acute damage to chronic remodeling.

Some patients develop:
• persistent diffusion-reduced volume (DLCO)
• ventilatory limitation
• interstitial changes on CT scan

In the most severe cases, a fibrotic process may develop, with characteristics sometimes overlapping with more classic interstitial fibrosis.

Post-inhalation fibrosis: how real is the risk?

The question is far from academic.

To date, it is still unclear:
• the true incidence of fibrotic progression
• which patients are most at risk
• whether it is "progressive" fibrosis or a stable outcome

Factors such as:
• severity of exposure
• need for mechanical ventilation
• advanced age
appear to increase the risk of long-term outcomes.

Clinical Management: Many Certainties, Many Unknowns

In the acute phase, treatment is primarily supportive:
• oxygen therapy
• ventilation in the most severe cases
• bronchodilators

The role of corticosteroids remains controversial and must be evaluated on a case-by-case basis.

What is often missing, however, is a fundamental element: long-term follow-up.

The Key Point: Don't Lose These Patients

One of the most important lessons is that these patients should not be considered "cured" upon discharge.

It is essential to plan for:
• clinical reassessment
• respiratory function monitoring
• possible radiological follow-up
to identify any persistent symptoms early.

A message for clinical practice

Events like the one in Crans-Montana are an important reminder: inhaling toxic substances is not just an acute problem, but can also represent the beginning of a chronic respiratory disease.

For clinicians, this means:
• maintaining high levels of vigilance during follow-up
• avoiding prognostic underestimations
• early consideration of fibrotic progression

Between acute damage and fibrosis, there is a gray area that is still little explored. It is precisely in this area that the most important challenges will be faced in the coming years: identifying patients at risk, understanding the mechanisms of progression, and, above all, intervening before the damage becomes irreversible.