Advanced techniques Flashcards
Tidal Volume (TV)
The volume of air inhaled or exhaled during normal breathing.
Inspiratory Reserve Volume (IRV)
The additional volume of air that can be inhaled after a normal inspiration.
Total Lung Capacity (TLC)
The maximum volume of air the lungs can hold.
Vital Capacity (VC)
The maximum amount of air a person can exhale after a maximum inhalation.
Functional Residual Capacity (FRC)
The volume of air remaining in the lungs after normal expiration.
Residual Volume (RV)
The volume of air remaining in the lungs after maximal expiration.
What happens when FRC decreases towards RV?
Dependent airways begin to close – this is known as closing volume (CV).
What occurs if closing volume encroaches on FRC?
Airway closure may happen during normal expiration, leading to atelectasis and a reduction in the V/Q ratio.
Internal factors affecting lung volumes
Restrictive lung diseases, consolidation, atelectasis, pulmonary oedema.
External factors affecting lung volumes
- Chest wall deformity
- lung compression from abdomen
- pleural effusion
- pneumothorax
- obesity
- neuromuscular disease
- reduced inspiratory drive
- pain
- anxiety
- general anaesthetic.
Sputum Retention
The inability of a patient to clear secretions from their respiratory tract due to factors like viscosity, volume, or impaired mucociliary clearance.
Phases of an Effective Cough
- Deep inspiration
- Laryngeal closure & chest/abdominal contraction → rise in intrathoracic pressure
- Glottis opens → rapid expiratory airflow expels mucus.
What can make a cough ineffective?
Pain, muscle weakness, inability to close the glottis, altered skeletal structure.
Factors determining Work of Breathing
- Demand (drive to breathe)
- Load (resistance to breathing)
- Capacity (efficiency of respiratory muscles).
What increases work of breathing?
- Muscle fatigue
- infection
- fever
- kyphoscoliosis
- neuromuscular disease
- lung stiffness
- wheeze
- sputum.
Lung Compliance
The expandability of the lungs and chest wall.
What happens with decreased lung compliance?
- Reduced lung expansion
- lower lung volume
- reduced FRC
- increased tendency to collapse.
What happens with increased lung compliance?
Lungs inflate easily but are harder to exhale due to reduced elastic recoil, leading to air trapping.
Intermittent Positive Pressure Breathing (IPPB) - ‘Bird’
A form of assisted inspiration using pressured oxygen/air with passive expiration.
Indications for IPPB
Increased work of breathing, sputum retention, atelectasis, reduced tidal volume.
Mechanical Insufflation-Exsufflation (MI:E) - ‘Cough Assist’
A device that alternates positive and negative airway pressure to simulate a cough for secretion clearance.
Indications for Cough Assist
Weak, ineffective cough due to poor inspiratory effort or low expiratory flow rate.
Contraindications/precautions for IPPB & Cough Assist
Undrained pneumothorax, cardiovascular instability, large bullae, bronchopleural fistula, lung abscess, severe haemoptysis, active TB, facial trauma, vomiting, raised ICP, recent thoracic/GI surgery.
