Week 11

Question 1

what are some key respiratory physiotherapy problems

Answer 1

• Dyspnoea
• Secretion retention
• Loss of lung volume
• Respiratory Failure

Question 2

what are the normal mechanics of breathing

Answer 2

Diaphragm (+/- external intercostal) contraction
Increased thoracic volume
Decreased thoracic pressure (Boyle’s Law)
Air (a gas) moves from an area of high pressure to low pressure (Dalton’s Law)

Question 3

How do we tell the diaphragm and external intercostals to contract for inspiration?
(Neural control of breathing)

Answer 3

Respiratory centres located in the brainstem (medulla oblongata and pons specifically)
For normal quiet tidal volume breathing – only need diaphragm to contract
Signal originates at the back of the medulla in dorsal inspiratory region
Neurones spontaneously fire off in a fire-stop-fire-stop pattern
With an intact spinal cord they send signals to C3 C4 C5
Send signal to phrenic nerve which innervates the diaphragm

Question 4

what triggers the inspiratory centre

Answer 4

Chemoreceptors which can detect changes in CO2, O2 and H+ in the blood
CO2 + H2O H2CO3 H+ + HCO3-

Peripheral chemoreceptors in the aortic arch (via vagus nerve) and carotid bodies (via glossopharangyl nerve)

Central chemoreceptors near the medulla

Muscle spindles and golgi tendon organs in respiratory muscles – provide input re: muscle length and force

Question 5

what is a hypoxic drive

Answer 5

Normally, people have a hypercapnic respiratory drive i.e. increased CO2 triggers the chemoreceptors to excite the inspiratory centres

But in circumstances where people chronically have high levels of CO2 the respiratory drive becomes triggered by hypoxia (low levels of O2)

We call this a ‘hypoxic drive’

Question 6

how can the 2 types of respiratory failure be classified

Answer 6

Type 1 - Lung failure, Hypoxaemia
Type 2 - Pump failure, Hypoxaemia and Hypercapnia

Respiratory failure occurs when not enough oxygen (O2) passes from your lungs into your blood. (Type I)

Respiratory failure also can occur if your lungs are unable to remove carbon dioxide (CO2) from your blood. Too much carbon dioxide in your blood can harm your body’s organs.

Both of these problems—a low oxygen level and a high carbon dioxide level in the blood—can occur at the same time. (Type II)

Question 7

what is the definition of type 1 respiratory failure

Answer 7

Type 1 Respiratory Failure - Hypoxaemic

Failed oxygenation
Failure in gas exchange function of respiratory system

Typically observed in patients with:
Atelectasis
Pneumonia
Pulmonary embolism
Acute Pulmonary Oedema

Question 8

how can type 2 respiratory failure be defined

Answer 8

Type 2 Respiratory Failure - Hypoxaemic and Hypercapnic

Failed oxygenation AND ventilation
Impaired central respiratory drive, muscle weakness or fatigue
Failure of respiratory pump

Typically observed in:
COPD exacerbations
Asthma
Obstructive Sleep Apnoea
Cystic Fibrosis
Neuromuscular disease (eg: MND)

Question 9

what is the overall definition of Respiratory Failure

Answer 9

“Failure of the respiratory system to provide adequate gas exchange for the metabolic demands of the body”

Question 10

how do we assess for respiratory failure

Answer 10

• ABGs
• coronate their clinical symptoms to their ABGs

Question 11

what are some clinical features of Hypoxaemia

Answer 11

Cyanosis
Tachypnoea
Increased cardiac output
Tachycardia
Peripheral vasoconstriction
Respiratory muscle weakness
Use of accessory muscles
Restlessness, confusion, coma
Clubbing (chronic)

Question 12

what are some clinical features of Hypercapnia

Answer 12

Flapping tremor
Tachypnoea
Tachy/Bradycardia
Peripheral vasodilation
Headache
Clammy/Sweating
Fatigue
Drowsiness, hallucinations, coma

Question 13

how can you manage type 1 respiratory failure

Answer 13

Continuous Positive Airway Pressure (CPAP)

Question 14

how can you manage type 2 respiratory failure

Answer 14

Bilevel Positive Airway Pressure (BiPAP)

Question 15

what is NIV

Answer 15

Non-invasive Ventilation
Application of respiratory support via a sealed patient interface e.g. full face mask or nasal mask without the need for invasive ventilation via endotracheal tube or tracheostomy

Deliver positive pressure ventilatory support

Question 16

what is Invasive Ventilation (IV)

Answer 16

Positive pressure ventilation via an endotracheal tube (ETT) or a tracheostomy

Requires sedation and paralysis to insert and often to tolerate an ETT

Question 17

what are the advantages of NIV

Answer 17

Can be applied and removed according to the patients needs therefore making communication and mobilisation easy
Complications such as URTI and LRTI and tracheal stenosis are avoided
Patients very rarely require sedation
Avoids intubation
Early mobilisation
Maintains nutrition
Better patient morale – enables communication

Question 18

what are the disadvantages of NIV

Answer 18

Claustrophobia
Facial pressure sores
Airway not protected
Difficulty assessing bronchial secretions for suctioning
Time consuming

Question 19

how can NIV be applied

Answer 19

Oxygen mask from flow generator

Question 20

what is CPAP

Answer 20

Continuous Positive Airway Pressure
Continuous positive airway pressure throughout both inspiration and expiration

Question 21

what is the physiology of CPAP

Answer 21

Increases pressure within the airway and holds open collapsed alveoli, pushing more oxygen across the alveolar membrane , forcing interstitial fluid back into the pulmonary vasculature

Airways at risk from excess fluid are stented open

Reduces increased work of breathing

It increases intrathoracic pressure which decreases venous return to the heart and reduces the preload (pressure in the ventricles at the end of diastole)

This lowers the pressure that the heart must pump against (afterload), both of which improve left ventricular function

Gas exchange is therefore maintained or improved

Question 22

what is BiPAP

Answer 22

Bi-level Positive Airway Pressure (BiPAP) two levels

The operator sets two pressure levels:
Inspiratory Positive Airway Pressure (IPAP)
Expiratory Positive Airway Pressure (EPAP)

Note the pressure difference between IPAP and EPAP is called the pressure support
Example: IPAP = 20, EPAP = 6, Pressure Support (PS) = 20-6 = 14

Question 23

what is the Mechanism of action BiPAP

Answer 23

IPAP

Improves pulmonary mechanical movement
Supports inspiratory effort and reduces work of breathing; unloading respiratory muscles
Improves Tidal Volume
Improves CO2 removal

EPAP

It splints open the airway which improves alveolar gaseous exchange and limits further collapse
Prevents rebreathing of CO2 and aids oxygenation
Increases FRC & counteracts intrinsic PEEP

Question 24

what are the differences between CPAP and BiPAP

Answer 24

CPAP
Continuous pressure
Same pressure during exhalation and inhalation
Commonly used at home (less complicated)
Needs little monitoring
Cheaper

BiPAP
Continuous pressure
Different pressures during exhalation and inhalation
Not commonly used at home (complex)
Needs monitoring of delivered pressures
Expensive

Question 25

what is FRC

Answer 25

Functional Residual Capacity Functional residual capacity (FRC) is the volume of air in the lungs at the end of normal passive expiration (approx. 2400 mls in a 70kg person)

Question 26

when does FRC decrease

Answer 26

when lying in supine if you are obese if you are pregnant during anaesthesia

Question 27

hoe does CPAP increase FRC

Answer 27

CPAP increases FRC – by increasing the surface area of the alveoli This increase in alveoli surface area improves and allows for greater gas exchange (oxygenation & ventilation) This improves oxygenation

Question 28

what are some factors that affect FRC

Answer 28

Increases FRC: Height Going from supine to standing/ upright Decreased lung elastic recoil (emphysema) PEEP Decreases FRC: Obesity Muscle Paralysis Supine position Pregnancy Anaesthetic Pulmonary disease causing increased elastic recoil of the lungs

Question 29

what is PEEP

Answer 29

Positive End Expiratory Pressure (PEEP) Do we have a natural PEEP in our lungs? The lungs never fully empty. Some air remains in the alveoli at all times. This is known as FRC or intrinsic PEEP. Normal approx. 4-5 cmH20

Question 30

when do intrinsic positive end and expiratory pressure occur

Answer 30

Intrinsic positive end expiratory pressure occurs when the expiratory time is shorter than the time needed to fully deflate the lungs – preventing the chest wall from recoiling fully – leads to gas trapping PEEP can get confusing…. As we do want some degree of PEEP to stop the airways from collapsing!

Question 31

what are some other positive pressure treatment options

Answer 31

Intermittent Positive Pressure Breathing (IPPB) AKA The Bird Mechanical Insufflation – Exsufflation (MI-E) AKA Cough Assist High Flow Nasal Oxygen (HFNO)

Question 32

what is IPPB

Answer 32

intermittent positive pressure breathing Intermittent positive pressure breathing (IPPB) is a type of noninvasive ventilation (NIV) that delivers positive pressure during inspiration and then returns to atmospheric pressure during expiration. IPPB was designed to help patients take deeper breaths, stimulate a cough, and treat or prevent atelectasis. This article will cover the basics of IPPB and how it works, so keep reading if you want to learn more. - The Bird machine = Provides a positive pressure breath on inspiration via a mouthpiece – the patient triggers the breath

Question 33

what are some indications of IPPB

Answer 33

The need to improve lung expansion in the presence of atelectasis when other forms of therapy have been unsuccessful. Inability of the patient to clear secretions adequately because of pathology that severely limits the ability to ventilate or cough effectively and failure to respond to other modes of treatment. Patient who have an acute flare-up of their breathing problem and are too weak to have an effective cough The need to deliver aerosol medication to the patient 

Question 34

what are some contraindications of IPPB

Answer 34

Undrained pneumothorax Active haemoptysis Hemodynamic instability Raised Intracranial pressure (ICP) Tracheoesophageal fistula Recent surgery on the oesophagus, skull, face, or mouth Untreated, active tuberculosis (hazard to the practitioner) Nausea, air swallowing, or hiccups

Question 35

what is Mechanical Insufflation - Insufflation (MI-E)

Answer 35

AKA Cough Assist Delivers a positive pressure on inspiration and a negative pressure on expiration

Question 36

what are some Mechanical Insufflation- Exsufflation devices

Answer 36

- Nippy clearway - Nippy clearway 2 - Philips Respironics E70

Question 37

what are the MI-E indications for use

Answer 37

Sputum retention typically due to: Respiratory muscle weakness Reduced peak cough flow (<160L/min) Bulbar muscle involvement preventing ability to breath-stack Typical patient groups: Motor neurone disease Spinal muscular atrophy Muscular dystrophy Spinal cord injuries Acute exacerbations of chronic lung conditions (where cough is ineffective due to fatigue) Post-polio syndrome (still common in Africa, South-East Asia) Myasthenia gravis

Question 38

what are some MI-E absolute contraindications

Answer 38

Undrained pneumothorax Severe/Uncontrolled bronchospasm Head injury with intracranial pressure (ICP) > 25mmHg Severe arterial hypotension Trache-oesophageal fistula Significant haemoptysis

Question 39

what are some MI-E relative contraindications

Answer 39

Proximal tumour or obstruction Emphysematous bullae Recent oesophageal or lung surgery e.g. lobectomy Spinal instability Severe exacerbation of COPD / bronchospasm ARDS Raised intracranial pressure (ICP) Hypotension (Systolic <80) Cardiovascular instability / arrythmias Acute head injury Unexplained haemoptysis High respiratory rate Subcutaneous emphysema Recent meal Undrained pleural effusion Recent facial fractures, maxfax surgery or burns

Question 40

what does the High Flow Nasal Oxygen (HFNO) do

Answer 40

Provides humidification, high FiO2 and PEEP (~5cmH2O), reduces anatomical dead space Increasingly used to improve oxygenation in acute Type I respiratory failure