Role of Physiotherapy in Mechanical Ventilation

Mechanical Ventilators

Negative pressure generator

Positive pressure mechanical ventilation

Application of a positive pressure breath to provide essential gas exchange

• Through an artificial airway

  • Tracheal tube 

  • Tracheostomy tube 

Artificial Ventilation Requires

Requires insertion of the tracheal tube into the patient’s airway

Positive pressure breaths are delivered in 2 ways

• pressure generator

• flow generator

Pressure Generator

Maintains constant pressure during inspiration

Flow generator

Maintains a constant flow during inspiration

Mechanical Ventilation Physiological Effects 

Improve gas exchange

Increase lung volume 

Reduce severe hypoxia 

Stabilize chest (flail chest) 

Decrease WoB (ie. post-major surgery) 

Stabilize acute pulmonary oedema 

Mechanical Ventilation Clinical Effects

Correct hypoxemia

Correct respiratory acidosis

Reverse atelectasis

Decrease myocardial oxygen consumption

Buy time for physiotherapist to work on maximizing lung function

Complications of Positive Pressure Ventilation

Decreased venous return

Gastro-intestinal malfunction

Pulmonary barotrauma/volutrauma

Atelectasis

Infection

General weakness

Risk of DVT

Psychological trauma

Implications for Physiotherpay

Understand the respiratory status of the patient

• What support does this patient require?

• How is the patient performing with this support?

VIDD

Ventilator-induced diaphragm dysfunction

Implications of Mechanical Ventilation - VIDD 

Passive inflation of the lung (unloading the diaphragm) 

Sedation 

Metabolic, nutrition, mitochondrial dysfunction 

Impairment of protein synthesis

=VIDD

Pulmonary Ventilation is determined by

Inflation pressure

Regional compliance

Time constant of alveoli

Electrical Impedance Tomography EIR shows

Positive pressure ventilation causes a shift of ventilation to ventral areas of the lung

Microatelectasis 

Supine lying —→ basal collapse despite mechanical ventilation

Role of physiotherapy for patients under mechanical ventilation

Prevention of VIDD

Improve regional lung volume and ventilation

Assist with liberation from MV

Technique-

• Positioning

• Manual Hyperinflation (MHI)

How is breath initiated?

Patient triggered

Time cycled

How is the breath delivered?

Volume controlled/limited 

Pressure controlled/volume 

How is breath terminated?

Time

Volume

Pressure

Decrease in flow

Supported breaths are

Continuous mandatory ventilation CMV

Intermittent mandatory ventilation IMV

Continuous spontaneous ventilation CSV

Ventilation Patterns 

Volume controlled or pressure controlled 

Volume controlled VC -CMV

Volume controlled VC_IMV

Pressure controlled PC_CMV

Pressure controlled PC_IMV

Pressure controlled PC-CSV

CMV

Continuous Mandatory Ventilation

Patient triggered ventilation 

Assist controlled ventilation

PEEP

Positive End Expiratory pressure

Peak airway pressure = 20cmH20; PEEP=5 cmH2O

CPAP

Continuous Positive Airway Pressure

BiPAP

Bi-level positive airway pressure

Implications to the physiotherapist 

MUST check before and after physiotherapy intervention 

• peak airway pressure 

• tidal volume 

• oxygen volume 

• oxygen concentration 

• disconnect alarms are armed 

• observe chest wall movement 

• auscultate breath sounds (air entry) 

  • observe whether the patient is ‘fighting’ with the ventilator delivered breath 

Role in Weaning (liberation from MV)

Maintain airway clearance

Monitor and maximize lung function

Education

• Encourage spontaneous breaths during MI

• Supervise spontaneous breathing

Respiratory muscle rehabilitation

• Consider the use of IMT - Inspiratory Muscle Training

NIPPV

Non-invasive positive pressure ventilation

Delivery of positive breaths without the need of tracheal or tracheostomy tube

Nasal.Full-face mask check

• mask comfort 

• proper seal