Forum 1: reparing for your patient and subjective assessment

Primary Function of the Respiratory System

• Supply the body tissues with oxygen

• Dispose of carbon dioxide

What system is the airway innervated by?

The autonomic nervous system

Central centers in the brain stem

1. Inspiratory center (medulla)

2. Expiratory center (medulla)

3. Pneumotaxic center (pons) 

4. Apneustic center (pons)

What does the nose contain?

Respiratory mucus- goblet cells

What does the Pharynx contain?

Nasopharynx (air)

Oropharynx (food and air)

Larynggopharyx (food and air)

• bifurcates into larynx

• and oesophagus

• larynx protected by epiglottis

What does the Larynx contain?

vocal cords

What does the Trachea contain?

Trachea

• anterior to the oesophagus

• ‘wind-pipe-

• cartilaginous rings

right vs left bronchus

trachea bifurcates into left and right main bronchus = carina

• right main bronchus - 20-30 degrees

• left main bronchus - 45-55 degrees

how many divisions of airway in the human lung?

approx. 23 divisions

Lung Lobes

Right = 3 (upper, middle, lower)

Left = 2 (upper and lower)

Separated by fissures

• right horizontal and oblique

• left oblique

lung segments

10 right 

8 left 

• anatomically and functionally separate unit of lung 

  • own artery, vein and segmental bronchus

Pleura 

Parietal Pleura- outer layer which connects to the chest wall

• has nerve innervation (pleuritic pain)

Visceral Pleura- inner layer which covers the lungs 

Pleural fluid

Allows pleura to slide during ventilation

• negative pressure which counteracts the tendency of the lungs to recoil

• clear, straw-like colour

• produced and absorbed at a constant rate

  • if excess pleural fluid, there is decreased room for the lungs to expand

Principal muscles of respiration

Intercostals

Diaphragm

Diaphragm

Main muscle of inspiration

Separates thorax from abdomen

Large dome shaped muscle

• Higher anteriorly

Sits 1-2cm higher on the right due to the liver

Intercostals

Pass between adjacent ribs

3 layers - external, internal and innermost

Accessory muscles of respiration (inspiration)

Scalenes (elevation of rib cage) 

SCM (elevation of rib cage)

Pec major

Pec minor 

Muscles of active expiration

Abdominal muscles 

Internal intercostals

Openings of diaphragm

3 structures pass through:

1. Oesophagus

2. Aorta

3. Vena cava

Quiet breathing

Quiet breathing- expiration results from passive recoil of lungs

Active expiration

Internal intercostals - expect interchondral part

Abdominal muscles (depress lower ribs, compress abdominal contents)

Rectus abdominis

External oblique

Internal oblique

Transversus abdominis

What must happen to the thorax for respiration?

The dimensions must change 

2 movements

• pump handle 

• bucket handle 

Pump Handle

Increasing anterior-posterior diameter

Elevation sternum and ribs 2-5 with inspiration

Bucket Handle

Increase transverse diameter of thorax

Anterior ends of ribs 8-10 move upwards and outwards

3 steps of gas exchange at the alveoli

1. oxygen inspired through conducting zone into respiratory zone of bronchial tree

2. alveolar gas contains a mixture of fresh gas and some expired CO2

3. oxygen moves across the alveolar-capillary membrane via diffusion

Diffusion is dependent on:

• surface area of alveolar membrane

• concentration / pressure gradient

• gas solubility n

• thickness of alveolar membrane

• ventilation / perfusion coupling

3 functions of mucociliary clearance

1. to act as a mechanical barrier to trap organisms

2. is a chemical screen with anti-oxidant properties

3. biological barrier interacting with organisms and inflammatory cells

3 main components of mucociliary clearance

1. cilia 

2. aqueous (sol) layer 

3. viscous (gel) layer 

Mucociliary clearance is affected by

Quantity of mucous (increased obstruction)

Viscosity of mucous (hyper-viscous secretions impede movements, airway dehydration- cilia unable to stretch into gel layer as bent over by weight of dehydrated muscous)

Cliliary beat frequency (impaired in diseases such as primary ciliary dyskinesia and immotile cilia syndrome)

Collateral ventilation

Provides an alternate route of ventilation when peripheral airways are obstructed

breathing

the process of moving air into and from the lungs to facilitate gas exchange

respiratory system requires all the following for effective gas exchange:

• nose and mouth

• trachea and airways

• lungs including alveoli

• respiratory muscles

• blood vessels

biomechanical and physiological process

Airway structure and function

Trachea- C shaped rings

Branching Bronchi - semi-circular cartilaginous rings

Small airway

Small Airways

Lie interwoven with lung parenchyma 

Have muscular walls 

Are vulnerable to bronchial disorder (spasm, oedema, hypersecretion)

Repeated coughing can weaken airway walls 

Become floppy/collapsible 

Conducting Zone

Conducting airways brings gas to the respiratory zone

Begin at the nose all the way to terminal bronchioles

Respiratory Zone

Where gas exchange takes place

Respiratory bronchioles and alveoli

Anatomical dead space

The air left within the conducting zone each breath

Anatomical dead space

The air left within the conducting zone each breath

~150ml tidal volume

Alveolar dead space 

Inspiratory gas reaching the alveoli but not participating in gas exchange due to insufficient blood supply 

In health this is almost 0 

Physiological dead space

Sum of all parts of tidal volume breath which does not participate in gas exchange (anatomical and alveolar dead space)

Atmospheric Pressure

Pressure exerted by gases in the air

Intra-Abdominal Pressure

Always positive

Generally higher-pressure system

Helps with core stability

Intra-Thoracic Pressure

Negative pressure during inhalation, positive during exhalation

Generally low-pressure system 

Intrapulmonary Pressure

Pressure within the alveoli

Intrapleural Pressure

Pressure within the pleural cavity

Transpulmonary Pressure

The difference between the intrapulmonary and intrapleural pressures

Mechanics of Ventilation 

Mechanical process that depends on volume changes within the thorax 

VOLUME CHANGES —> PRESSURE CHANGES —→ GAS FLOW

Inspiration

Increase thoracic cage diameter and lung volume

Fall in intrapulmonary pressure so gas flows down pressure gradient

Air flow ceases when intrapulmonary pressure becomes equal to atmospheric pressure

Respiratory Compliance

Measure of stiffness/stretchiness of the lung

Lung Compliance

Distensibility of lung

Chest wall compliance 

Distensibility of chest wall

respiratory compliance can be altered or influenced by disease

• Respiratory disease- reduced total lung compliance is classified as restricted disease- patients have difficulty breathing in

leads to:

• increased respiratory load- increased work of breathing

• accessory muscle use

Reduced respiratory compliance

makes the generation of larger pressures necessary to change volume

• low lung volumes (atelectasis, post surgery, prolonged recumbency in supine)

• high lung volumes (hyperinflation, aging)

• reduced pulmonary surfactant

• pulmonary oedema

• consolidation

• interstitial fibrosis

• pleural effusion

Reduced chest wall compliance 

Lungs are normal but inspiration reduced to chest wall compliance 

• thoracic deformity (kyphosis, scoliosis, sternal deformity) 

• circumferential thoracic burn 

• obesity 

• supine position 

• raised intra-abdominal pressure (abdominal distension, post-surgery, pregnancy) 

• aging 

Ventilation

Air which reaches the lungs

Distribution of ventilation will be influenced by part of lung, position of patient airflow resistance

• occurs optimally in lower 1/3 of lung- partially expanded but large capacity for volume change

Diffusion

Transfer of gases across alveolar-capillary membrane

Perfusion (Q)

Blood flow available to participate in gas exchange

Distribution of perfusion

• increases down the healthy upright lung

Ventilation- Perfusion

Vital to maintain VQ matching to achieve adequate gas exchange

In the presence of respiratory disease, autoregulatory mechanisms employed:

1. Hypoxic pulmonary vasoconstriction

• if low PaO2 then arterioles constrict to redistribute blood flow

• Chronic in COPD - lead to heart failure

2. Pulmonary capillary recruitment

• If good ventilation, additional arterioles recruited to optimise VQ matching

Oxygen Transport

Immediately bound to haemoglobin (Hb) (98%)

Physically dissolved in the plasma (2%)

Carbon Dioxide Transport

Carried in blood entirely as solution - mostly bicarbonate

oxygen dissociation curve

relationship between partial pressure of O2 (either alveoli or tissues) and the degree to which Hb is saturated with O2

Factors which shift the curve

All of the following shift the curve to the R and down

• decreased pH

• increase in PCO2

• increased temp.

• increased 2,3-diphosphoglcerate (DPG) (by product of glycolysis, increased in pregnancy)

A shift to the right reduces oxygen’s affinity for Hb (to allow delivery to tissues)

Haldane Effect

In the presence of hypoxaemia, CO2 bind to Hb to be transported back to the lung 

Bohr Effect

Shift to the right of oxygen equilibrium curve caused by a drop in pH, reducing the Hb’s affinity for O2

• Allows for better oxygen unloading in metabolically active peripheral tissues like skeletal muscle during exercise. Increased skeletal muscle activity causes localized increases in carbon dioxide partial pressure, which lowers the local blood pH.

Goals of a respiratory assessment

• Establishing the patient’s main problems at presentation

• Identifying any relevant co-morbidities

• Identifying precautions or contraindications to treatment

• Formulating a treatment plan

• Identifying outcome measures that can be used to determine effectiveness/responses to treatment

• Identifying patients for whom treatment will not be beneficial

Sources of information

• the medical chart (blood tests, chest x-rays, pulmonary function tests, arterial blood gas analysis)

• observation charts- particularly for vital signs, medications, and clinical pathways 

• medical and nursing staff involved 

• the patient and/or their family/carers

Content gathered from inpatient chart

history of presenting condition (HPC)

past medical history

investigations

• blood

• scans

current condition

attachments

other allied health input

HAIDET

A way to remember meeting a pt the first time

Hand Hygiene

Acknowledge

Introduce

Duration

Explanation

Thank you

Subjective Assessment- Purpose 

Confirm or elaborate on information gained from chart

Establish rapport with patient 

May lessen anxiety

Respiratory Assessment

Shortness of breath

Wheeze

Cough

Sputum

Smoking History

SOB Questions

Do you feel short of breath?

At rest or with exertion?

What activities make you short of breath?

How long to recover?

Wheeze Questions

Do you experience a wheeze?

What provokes it?

What relieves it?

Cough Questions

Have you been coughing?

Is this usual for you or different? (current vs. usual for patient)

Productive or non-productive?

Any difficulties clearing your sputum?

When and how often?

Sputum Questions

Have you been producing any sputum? (current vs usual for patient)

Volume? Colour? Consistency? Haemoptysis?

Smoking history Questions

How much?

For how long?

Respiratory Subjective- pre-existing respiratory conditions

How do they usually manage it?

• physio? meds?

Frequency of exacerbations

• how are they managed?

• do they have an action plan?

Other current status questions

• what have they done today

Functional history

• exercise

• social history

• medication

• tests

Clinical Reasoning Example Form

Clinical Reasoning Process 

1. Identify significant information from subjective and objective assessment

2. Combine with knowledge of normal anatomy and physiology and knowledge of pathophysiology and clinical manifestations and clinical course/prognosis of disease

3. Put puzzle pieces together to identify the key problems amenable to physiotherapy

4. Utilise knowledge of evidence based interventions to best address the identified key problem for that individual

Clinical Reasoning step 1

Identify significant information from subjective and objective assessment

Clinical Reasoning step 2

Combine with knowledge of normal anatomy and physiology and knowledge of pathophysiology and clinical manifestations and clinical course/prognosis of disease

Clinical Reasoning step 3

Put puzzle pieces together to identify the key problems amenable to physiotherapy

Clinical Reasoning step 4

Utilise knowledge of evidence based interventions to best address the identified key problem for that individual