Mechanical Ventilation

Excerpt

Mechanical ventilation is necessary to sustain life in acute settings; hence, its management is essential for clinicians and other healthcare providers to understand and apply it safely. This knowledge must be built on a solid understanding of the basic principles of human physiology and airway mechanics. This article will focus on the management of the intubated patient in the first few hours of care on mechanical ventilation. It will review the basics of invasive mechanical ventilation, the common modes of ventilation, initial settings, and supportive care for intubated patients will be discussed in this review. Noninvasive ventilation (NIV) will be addressed separately.

The primary indications for invasive mechanical ventilation can be divided into the following categories:

1. Airway disease of compromise.

   1. Airway protection in a patient who is obtunded or has a dynamic airway, e.g., from trauma or oropharyngeal infection.

   2. Airways obstruction is either proximal ( eg angioedema) or distal (asthmatic bronchospasm or acute exacerbation of chronic obstructive pulmonary disease).

2. Hypoventilation due to impaired drive, pump failure, or inability to exchange gases resulting in hypercapnic respiratory failure. The etiology can be divided into the following subcategories:

   1. Impaired central drive (e.g., drug overdose)

   2. Respiratory muscle weakness (e.g., muscular dystrophy and myositis)

   3. Peripheral nervous system defects (e.g., Guillain-Barré syndrome or myasthenic crisis)

   4. Restrictive ventilatory defects (e.g., chest wall trauma or disease or massive pneumothorax or effusion)

3. Hypoxemic respiratory failure can be due to the inability to exchange oxygen or delivery to the peripheral tissues due to one of the following reasons:

   1. Alveolar filling defects (e.g., pneumonia, acute respiratory distress syndrome (ARDS), or pulmonary edema)

   2. Pulmonary vascular defects leading to ventilation-perfusion (VQ) mismatch (massive pulmonary embolism or air emboli)

   3. Diffusion defects (advanced pulmonary fibrosis)

4. Increased ventilatory demand due to severe sepsis, shock, or severe metabolic acidosis