Physiotherapy Management in Cardiorespiratory Dysfunction II

Study Notes

Mechanical ventilation is a form of life support that mechanically assists or replaces spontaneous breathing.
Indications for mechanical ventilation include:
- Cardiac or respiratory arrest
- Tachypnea or bradypnea with respiratory fatigue or impending arrest
- Acute respiratory acidosis
- Refractory hypoxemia
- Inability to protect the airway associated with depressed levels of consciousness
Principles of mechanical ventilation:
- Inspiration may be generated by application of either a constant pressure or a constant flow of gas to the lungs
- Expiration is allowed when either a set pressure has been reached, a set volume has been delivered, or a set time has passed

Controlled Mandatory Ventilation (CMV):
- Vent initiates all breaths at a pre-set rate and tidal volume
- Patient has no control over ventilation
- Used mainly in the OR for paralyzed and sedated patients
Assist Control (A/C):
- Vent will allow a patient to initiate a breath and then deliver a pre-set tidal volume
- Machine set at a minimum rate so apnea will not occur if the patient does not initiate a breath
Synchronized Intermittent Ventilation (SIMV):
- Similar to A/C, but patients can take own breaths with their own tidal volume between mechanically assisted breaths
- Can be used as a primary mode or a weaning mode
Pressure Support Ventilation (PSV):
- Also called “spontaneous mode”
- Pt initiates breath & vent delivers a pre-set inspiratory pressure to help overcome airway resistance and keeps airways open
Continuous Positive Airway Pressure (CPAP):
- Positive airway pressure provided during both inspiration and expiration
- Improves gas exchange and oxygenation in patients able to breathe on their own

Adequate oxygenation:
- PaO2 > 60-70 on FiO2 0.4 to 0.5, PEEP 5-8 cmH2O
- PaO2/FiO2 ratio > 150-200
Adequate ventilation:
- PaCO2 35-45 mmHg
- pH 7.3 to 7.45
Adequate respiratory mechanics:
- Tidal volume
- Respiratory capacity
- Minute ventilation
Hemodynamic stability

Spontaneous breathing trials (SBT) lead to extubation more quickly than those receiving pressure support and IMV for weaning purposes in patients who are mechanically ventilated for > 1 week
Signs of distress during weaning:
- Increased tachypnea (> 30)
- Increased heart rate
- Irregular breathing pattern or use of accessory muscles
- Agitation or panic unrelieved by assurance
- Decrease pH to less than 7.25-7.3 with increasing PCO2
Problems encountered while weaning:
- Impaired ventilatory drive
- Upper & lower airway incompetence, obstruction, or secretions
- Lung parenchymal fluid or infection
- Pleural effusion or pneumothorax
- Chest wall abnormality, instability, or respiratory muscle weakness
- Electrolyte or nutritional problems
- Cardiovascular insufficiency

Patients weaning from mechanical ventilation should be considered for mobility and strengthening exercises
Mobilization requires teamwork with the entire medical team
Steps to mobilization include:
- Looking at baseline vitals
- Looking at baseline vent settings
- Locating all wires, tubes, etc.
- Moving IV pole and lines to the side
- Assisting patient to sitting at the side of the bed
- Transferring to the chair while managing lines
- Coordinating with the medical team to place on a portable vent if necessary
- Organizing equipment and lines
- Supporting lines, vent/IV pole, and vent tubing
- Having a tech or nurse follow with a wheelchair for safety

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