Oxygen Therapy and Mechanical Ventilation

Oxygen therapy is the administration of supplemental oxygen to correct or prevent hypoxaemia, while mechanical ventilation — invasive or noninvasive — uses a machine to support or replace the work of breathing when the respiratory system cannot maintain adequate gas exchange on its own. Together these modalities span the support technologies that respiratory and critical-care nursing use across the spectrum from mild hypoxaemia to acute respiratory failure.

Definition

Oxygen therapy is the delivery of oxygen at concentrations above ambient air to treat or prevent hypoxaemia, titrated to target oxygen saturation (O'Driscoll et al., 2017); mechanical ventilation (artificial respiration) is the assisted or controlled mechanical support of breathing, delivered noninvasively by mask or invasively via an artificial airway.

Scope

This entry covers supplemental oxygen and assisted ventilation as therapeutic modalities within respiratory nursing: how they support gas exchange, the distinction between oxygen therapy and ventilatory support, and the guideline and trial evidence that frames their use. It is reference and educational material; it does not provide oxygen targets, ventilator settings, dosing, or individualised instructions.

Core questions

• What problem does supplemental oxygen address, and why is it targeted rather than maximal?
• How does mechanical ventilation support or replace the work of breathing?
• What distinguishes noninvasive from invasive ventilation?
• What does landmark trial and guideline evidence say about how these modalities are framed?

Key concepts

• Hypoxaemia and oxygenation
• Target oxygen saturation
• Supplemental oxygen delivery devices
• Invasive mechanical ventilation
• Noninvasive ventilation
• Acute respiratory failure
• Lung-protective ventilation
• Gas exchange support

Mechanisms

Supplemental oxygen raises the fraction of inspired oxygen to increase the partial pressure of oxygen in the alveoli and arterial blood, correcting hypoxaemia; guidelines emphasise titrating it to a target saturation range rather than giving high concentrations indiscriminately, because excess oxygen carries its own risks, particularly in patients prone to hypercapnia (O'Driscoll et al., 2017). Mechanical ventilation supports or replaces spontaneous breathing by delivering positive pressure to the lungs, improving alveolar ventilation and oxygenation and reducing the work of breathing; in acute lung injury, ventilation strategies that limit tidal volume to protect the lungs improved survival in landmark trial evidence (Acute Respiratory Distress Syndrome Network, 2000). Noninvasive ventilation delivers this support through a mask, avoiding an artificial airway in suitable patients (Rochwerg et al., 2017).

Clinical relevance

Oxygen therapy and ventilatory support are central to respiratory and critical-care nursing, used across the spectrum from ward-based oxygen for hypoxaemia to noninvasive and invasive ventilation in acute respiratory failure. The entry describes these modalities and their evidence base for orientation and education; it does not specify oxygen targets, device settings, or ventilator parameters, which are individualised clinical decisions.

Evidence & guidelines

The British Thoracic Society guideline for oxygen use in adults frames oxygen as a treatment titrated to target saturation ranges (O'Driscoll et al., 2017). The Acute Respiratory Distress Syndrome Network trial established that lower tidal-volume (lung-protective) ventilation reduced mortality in acute lung injury and ARDS (2000). ERS/ATS clinical practice guidelines define the role of noninvasive ventilation in acute respiratory failure (Rochwerg et al., 2017). These describe evidence and recommendations at a population and care-organisation level rather than individualised orders.

Debates

How much oxygen should be given?

Guidelines moved away from liberal, maximal oxygen delivery toward titrating oxygen to defined target saturation ranges, reflecting evidence that both hypoxaemia and excess oxygen can be harmful, especially in patients at risk of hypercapnic respiratory failure.

Seminal works

• ardsnet-2000-tidal-volume
• odriscoll-2017-bts-oxygen
• rochwerg-2017-niv

Frequently asked questions

Is more oxygen always better?

No; current guidance is to titrate oxygen to a target saturation range rather than give maximal concentrations, because excess oxygen can be harmful, particularly in patients at risk of hypercapnia.

What is the difference between noninvasive and invasive ventilation?

Noninvasive ventilation delivers support through a mask without an artificial airway, while invasive ventilation delivers it via an endotracheal or tracheostomy tube; the choice depends on the clinical situation.