Ventilation and Weaning

Introduction

Ventilation can be defined as the process of air exchange between the lungs and the surrounding air [1]. In clinical settings, a type of machine called a mechanical ventilator is used to perform this function on patients facing severe respiratory illness. Once the patient is stable and able to Moving to Spontaneous Breathing It is important to take steps to wean the patient off dependent breathing. Weaning refers to the gradual withdrawal of the patient from life support systems or other forms of therapy for assisted breathing [1]. Take the patient off the ventilator This occurs when a patient improves and decides to breathe spontaneously through endotracheal intubation and eventual extubation (extubation) to remove them from the ventilator.

Goals of Mechanical Ventilation

The goals of mechanical ventilation are [2]:

Provide adequate (not perfect) oxygenation and ventilation
Reduce the patient’s work of breathing
Minimizes lung injury caused by ventilators, known as ventilator-induced lung injury (VILI).
Improve cardiac function
- Decreases preload
- Decreases afterload
- Decreases metabolic demand

Mechanical Ventilation

Mechanical ventilation can be[2]:

Noninvasive (if patient can secure airway and is hemodynamically stable)
- Mask: usually orofacial to start
Invasive
- Endotracheal tube (ETT)
- Tracheostomy – if the upper airway is blocked

Indications for mechanical ventilation[1][3]

Cardiac or respiratory arrest
Tachypnea or bradypnea with respiratory fatigue or impending asystole
Acute respiratory acidosis
Refractory hypoxemia Refractory hypoxemia (when PaO 2 cannot be maintained above 60 mm Hg and fractional inspired O 2 (F I O 2 ) >1.0)
Inability to protect airway associated with low level of consciousness
Shock associated with excessive work of breathing
Inability to clear secretions from impaired gas exchange or excessive respiratory function
Newly diagnosed neuromuscular disease, vital capacity <10 volume <10 – 15 mL/kg
Short-term adjuvant therapy in the management of acute intracranial hypertension (ICP)

The basic setup of a mechanical ventilator includes:

Mode
Tidal Volume
Respiratory rate (RR)
Inspired oxygen concentration (Fio2)
Positive end expiratory pressure (PEEP)

Mechanical ventilator breaths[2]

Breathing can be assisted or supported by ventilator control.

Controlled breaths: These breaths are completely “controlled” by the ventilator. The ventilator is intentionally never set to a breath-only mode. However, if your patient is paralyzed or has no Respiratory actuation (sedation coma, etc.).
Assisted Breaths: Unlike controlled breaths given at set intervals, assisted breaths are delivered to the patient if the patient attempts to trigger a breath. If your patient is trying to breathe, the ventilator will sense this and deliver a full mechanical breath. for assisted breathing The patient must trigger the ventilator (inhale the ETT and create a change in pressure or flow) and then the ventilator takes over completely and delivers a complete breath
Supported (spontaneous) breathing: These types of breathing are triggered by patient effort (like assisted breathing), but once triggered, the ventilator will give you some support, but not full support like assisted breathing.

Modes of Mechanical Ventilation[2]

The different modes of a mechanical ventilator and what they do vary. See some examples below:

Volume assist/control
Pressure assist/control
Pressure support (PS)
Synchronized Intermittent Mandatory Ventilation (SIMV) +PS
Pressure regulated volume control (PRVC)

[2]

Procedure of Weaning patient

Weaning is a gradual reduction in ventilation. Early non-invasive ventilation after extubation helps reduce total days of invasive mechanical ventilation; the less time patients spend on invasive ventilation, the lower its incidence, a new systematic review shows Ventilator-associated pneumonia [4]. In some cases, the process is quick and calm; however, in some patients, the process may be prolonged for days or weeks. Weaning is a term used in two different ways. First, it implies the termination of mechanical ventilation, and second Remove any artificial airway [5].

When to wean[5]

Normalised I:E ratio
Reducing FiO2 (usually <0.5)
No requirement for high PEEP
Appropriate underlying respiratory rate
Appropriate tidal volume and moderate airway pressure

The procedure is as follows:

Explain the procedure to the patient, assuring them that this is just a trial period
Tapering of ventilator support (eg, reducing pressure during pressure support)
The patient is in a better postural position (such as sitting upright or half-sitting)
The airway is suctioned
Patient is disconnected from ventilator and given oxygen or mechanical assistance (CPAP)
Encourage the patient to breathe spontaneously
Monitor patients for signs of dyspnea or increased PaCO2
Extubation should be done as soon as possible because breathing through the endotracheal tube increases the work of breathing
Encourage the patient to cough after extubation

When patients are alert and display a stable breathing pattern and control of their airway, they can be extubated. It may be difficult to wean the patient from the ventilator due to:

Inspiratory muscle atrophy
Fatigue
Paralysis of the diaphragm
A fear of suffocating

The role of physical therapy in mechanical ventilation and weaning

Traditionally, physical therapists have been involved in the respiratory care of mechanically ventilated patients in the ICU. [3] Respiratory care includes optimization of ventilation, airway clearance, prevention of pulmonary complications, and accelerated weaning from mechanical ventilation.

Techniques used by physical therapy to help improve the patient’s breathing and to take the patient off the ventilator may include: