Comprehensive Cardiorespiratory Physiotherapy Notes

Anatomy and Physiology of the Thorax and Rib Cage

• The Thoracic Cage:

  • Consists of the sternum, ribs, and thoracic vertebrae.
  • True Ribs: Ribs 1 through 7 connect directly to the sternum via their own costal cartilage.
  • False Ribs: Ribs 8 through 10 have cartilages that join the cartilage of the rib immediately superior to it.
  • Floating Ribs: Ribs 11 and 12 have no anterior attachment.
  • Rib Landmarks: Include the head, neck, tubercle, angle, and shaft.
  • Joints:
    • Costovertebral Joint: Where the head of the rib articulates with the vertebral body.
    • Costotransverse Joint: Where the tubercle of the rib articulates with the transverse process of the vertebra.

• Rib Movement Mechanics:

  • Pump Handle Movement: Primarily involves the upper ribs and results in the superior and anterior movement of the sternum, increasing the anteroposterior diameter of the thorax.
  • Bucket Handle Movement: Primarily involves the lower ribs, where the lateral shafts of the ribs elevate, increasing the transverse diameter of the thoracic cavity.

Respiratory Musculature

• Muscles of Inspiration:

  • Principal Muscles:
    • Diaphragm: The primary muscle of inspiration. Its domes descend during contraction, increasing the longitudinal dimension of the thoracic cavity and elevating lower ribs. It is innervated by the phrenic nerve ($C3, 4, 5$).
    • External Intercostals: Elevate the ribs ($T1-T11$).
    • Interchondral Part of Internal Intercostals: Also assists in elevating the ribs.
  • Accessory Muscles (Active during increased demand, $C2-7$):
    • Sternocleidomastoid: Elevates the sternum.
    • Scalenes (Anterior, Middle, Posterior): Elevate and fix the upper ribs.
    • Upper Trapezius: Assists in elevation.

• Muscles of Expiration:

  • Quiet Breathing: Expiration is a passive process resulting from the elastic recoil of the lungs and the relaxation of inspiratory muscles.
  • Active Expiration:
    • Internal Intercostals (except interchondral part): Depress the ribs ($T1-T11$).
    • Abdominal Muscles: Depress lower ribs and compress abdominal contents. These include its Rectus abdominis, External oblique, Internal oblique, and Transversus abdominis ($T5-T12$).

The Diaphragm and Internal Thoracic Structures

• Anatomy of the Diaphragm:

  • Features a central tendon and three major openings: the Inferior vena cava opening, the Oesophageal hiatus, and the Abdominal aortic opening.
  • Attachments include sternal, costal, and posterior (lumbar) via the crura and arcuate ligaments.
  • The dome of the diaphragm is typically lower on the left side due to the presence of the liver on the right.

• Pleura:

  • Visceral Pleura: Adheres directly to the lung surface and into the fissures.
  • Parietal Pleura: Lines the inner thoracic wall, superior diaphragm, and mediastinum. Subdivisions include Apical, Costal, Diaphragmatic, and Mediastinal pleura.
  • Pleural Cavity: The potential space between the two layers containing serous fluid.

Cardiac Structure and Function

• External Features:

  • The heart is oriented with an apex (bottom left) and base (top). Key vessels include the Superior and Inferior vena cava, Arch of aorta, and Pulmonary trunk.
  • Significant margins: Inferior margin and Obtuse margin.

• Internal Heart Chambers and Valves:

  • Right Side: The Right Atrium receives deoxygenated blood from the body; the Right Ventricle pumps blood to the lungs through the pulmonary valve. The Tricuspid Valve separates the right atrium and ventricle.
  • Left Side: The Left Atrium receives oxygenated blood from the lungs via pulmonary veins; the Left Ventricle pumps blood through the aorta to the systemic circulation. The Mitral Valve (Bicuspid) separates the left atrium and ventricle.

• The Cardiac Cycle:

  • 1. Blood returns to the heart.
  • 2. Passive filling of atria occurs.
  • 3. Tricuspid and Bicuspid valves open, allowing passive blood flow into the ventricles.
  • 4. Atria contract to complete ventricular filling.
  • 5. Ventricular contraction closes the AV valves and ejects blood into circulation.

The Respiratory System and Gas Exchange

• Four Phases of Respiration:

  • Ventilation: Movement of air in and out of the lungs.
  • External Respiration (Pulmonary Gas Exchange): Diffusion of $O_2$ from lungs to blood and $CO_2$ from blood to lungs.
  • Gas Transport: Transportation of gases to and from lungs via the cardiovascular system.
  • Internal Respiration: Movement of $O_2$ from blood to cells and $CO_2$ from cells to blood.

• Determinants of Respiratory Effectiveness:

  • Size and patency of airways.
  • Compliance of the lung tissue.
  • Power and endurance of respiratory muscles.

Conductive and Respiratory Zones

• Conducting Zone (Anatomy and Divisions):

  • Upper Respiratory Tract (URT): Nose, nasal cavity, Nasopharynx, Oropharynx, Laryngopharynx.
  • Lower Respiratory Tract (LRT): Larynx, Trachea, Bronchi, Bronchioles.
  • Trachea: Characterized by "C" shaped cartilaginous rings with a posterior gap for the oesophagus to allow passage of a food bolus.
  • Bifurcation: Occurs at the level of the 5th thoracic vertebra ($T5$).
  • Bronchial Tree: Right Primary Bronchus (vertical, shorter, wider) and Left Primary Bronchus (inferior to aortic arch).
    • Secondary (Lobar) Bronchi: One per lobe, reinforced with thick cartilage plates and lined with pseudostratified ciliated columnar epithelium.
    • Tertiary (Segmental) Bronchi: Supply bronchopulmonary segments ($10$ in the right, $8-9$ in the left).

• Branching Generations ($Z$):

  • Generation $0$: Trachea ($15-22mm$ diameter).
  • Generation $1$: Main bronchus.
  • Generations $2-10$: Lobar and Segmental bronchi.
  • Generations $11-15$: Terminal bronchioles (Diameter $0.5-1mm$; approximately $20,000$ in number).
  • Generations $16-23$: Respiratory bronchioles (Respiratory zone starts here).
  • Generation $24$: Alveolar sacs (Diameter $0.3mm$; roughly $300-600 \times 10^6$ alveoli).

Microscopic Anatomy of the Respiratory Zone

• The Mucociliary Escalator:

  • Cilia: Hair-like projections that produce a coordinated metachronal wave motion.
  • Mechanism: Cilia stroke at approximately $15 \text{ times per second}$ within the sol layer of mucus, propelling material at a speed of $2cm \text{ per minute}$ toward the pharynx.

• Alveolar Structure:

  • Type I Alveolar Cells: Site of gas exchange.
  • Type II Alveolar (Septal) Cells: Produce surfactant to reduce surface tension.
  • Alveolar Macrophage (Dust Cells): Responsible for phagocytosis of debris.
  • Acinus: An alveolar sac and its associated alveoli (Latin for "berry").

• Collateral Ventilation Pathways:

  • Pores of Kohn: Interalveolar communications ($1-2μm$; 5–20 per alveolus).
  • Channels of Lambert: Link alveoli and bronchioles ($25-30μm$).
  • Channels of Martin: Inter-bronchiolar communications ($80-150μm$).

• Interdependence: Expanding forces exerted between adjacent alveoli. Higher lung volumes result in greater expanding forces.

Objective Assessment: The Cardiorespiratory Toolbox

• Clinical Reasoning and Problem Identification:

  • Physiotherapists identify 6 core problems: Impaired Gas Exchange, Impaired Airway Clearance, Decreased Lung Volume, Breathlessness, Pain, and Reduced Exercise Tolerance.
  • Assessment follows a cycle: Assess → Problem List → Plan → Treat → Monitor → Re-assess.

• The ABCDE Systematic Approach:

  • A - Airway: Assess type (spontaneous, ventilated, oropharyngeal), patency, and risk of obstruction (secretions, aspiration, stridor).
  • B - Breathing: Respiratory rate ($12-20 bpm$), pattern (pursed lip), accessory muscle use, work of breathing, and oxygen saturation ($SpO_2$) targets (94-98\text{%} for most; 88-92\text{%} for $CO_2$ retainers).
  • C - Circulation: Monitoring Heart Rate ($HR$), Blood Pressure ($BP$), temperature, and specialized findings like edema, inotropes, and stability.
  • D - Disability: Glasgow Coma Scale ($GCS$), previous medical history (COPD, asthma), and current limiting factors (pain, sedation).
  • E - Exposure: Examination of surgical wounds, environmental factors, blood sugar, and relevant medications (nebulizers, mucolytics).

External Patient Observations

• Head and Neck:

  • Cyanosis: Central cyanosis reflects hemogloblin saturation; use of accessory muscles and pursed-lip breathing indicates respiratory distress.
  • Trachea: Check for midline shift or tracheal tug (indicative of hyperinflation).
  • Sculpturing: Visible accessory muscles (Sternocleidomastoid, Scalenes) and supraclavicular fossae.
  • Jugular Venous Pressure (JVP): Pulsation seen at a $45^∘$ angle. Normal is $3-4cm$ above the sternal angle; $> 4cm$ suggests right ventricular failure or hypervolemia.

• Chest Shape and Breathing Patterns:

  • Barrel Chest: Increased AP diameter due to hyperinflation.
  • Pectus Carinatum: Pigeon chest (protrusion).
  • Pectus Excavatum: Sternum is sunken.
  • Hoover’s Sign: Paradoxical inward movement of the lower rib cage during inhalation.
  • Breathing Terminology: Tachypnoea ($>20 bpm$), Bradypnoea ($<12 bpm$).

Palpation and Auscultation

• Palpation Techniques:

  • Assess symmetry and chest expansion ($3-5cm$ variation between inspiration and expiration).
  • Tactile (Vocal) Fremitus: Vibrations felt as the patient says ‘99’; increased vibrations indicates consolidation.
  • Subcutaneous emphysema (crepitus): Feels like "Rice Krispies" under the skin.

• Auscultation Findings:

  • Normal Sounds: Generated by turbulent airflow in central airways, filtered by lung tissue.
  • Wheezes (Added Sounds): Musical sounds from narrowed airways. Expiratory = bronchospasm; Inhalatory/Exhalatory = mechanical obstruction.
  • Crackles (Added Sounds): Discontinuous explosive sounds. Fine crackles = sudden pressure equalization (atelectasis); Coarse crackles = gas bolus moving through fluid.
  • Bronchial Breathing: Abnormal when heard in the peripheries; indicates lung tissue has consolidated.

Sputum and Peripheries

• Sputum Analysis Categories:

  • Mucoid: Clear/white (chronic bronchitis, asthma).
  • Mucopurulent: Discoloured but not frank pus.
  • Purulent: Thick, yellow or green/brown (Pseudomonas, Haemophilus infection).
  • Rusty/Redcurrant Jelly: Pneumococcus or Klebsiella.
  • Pink Frothy: Pulmonary edema.
  • Haemoptysis: Blood-streaked to frank blood (Tuberculosis, carcinoma, trauma).
  • Black Specks: Smoke inhalation or coal dust.

• Peripheries:

  • Clubbing: Found in chronic hypoxia.
  • Nicotine Staining: Indicator of chronic smoking.
  • Flapping Tremor (Asterixis): Sign of $CO_2$ retention.
  • Pitting Edema: Sign of cardiac failure.

Subjective Assessment: The Patient Interview

• Core Symptoms (The Big 5):

  1. Breathlessness (Dyspnoea).
  2. Cough.
  3. Sputum and Haemoptysis.
  4. Wheeze.
  5. Chest Pain.

• Specific Indices:

  • Pack Year History: Calculated as $\text{pack years} = \frac{\text{cigarettes per day} \times \text{years}}{20}$.
  • Dyspnoea Variations: Orthopnoea (shortness of breath when lying flat) and Paroxysmal Nocturnal Dyspnoea (sudden waking with SOB).
  • Clinical Escalatory Findings: Severe unexplained chest pain, sudden SOB, frank haemoptysis, syncope, or inability to speak in full sentences require immediate team review.

Arterial Blood Gas (ABG) Interpretation

• Normal Values (Adult):

  • pH: $7.35 - 7.45$
  • $PaCO_2$: $35 - 45 mmHg$
  • $PaO_2$: $80 - 100 mmHg$
  • $SaO_2$: > 95\text{%}
  • $HCO_3^-$: $22 - 26 mmol/L$
  • Base Excess (BE): $-2.0 \text{ to } +2.0$

• Definitions and Impairments:

  • Hypoxaemia: Reduced transfer of $O_2$ from lungs to blood ($PaO_2 < 80 mmHg$).
  • Respiratory Failure:
    • Type 1 (Hypoxaemic): Low $PaO_2$, normal/low $PaCO_2$. Defective oxygenation (e.g., V/Q mismatch).
    • Type 2 (Hypercapnic): High $PaCO_2$ ($> 50 mmHg$), usually low $PaO_2$. Due to inadequate alveolar ventilation.
  • Hypoxic Drive: In chronic hypercapnia, the body relies on low $PaO_2$ (rather than $CO_2$) as a stimulus to breathe. Excessive supplemental oxygen can depress ventilation in these patients.

• Acid-Base Patterns:

  • Respiratory Acidosis: $\text{pH} ↓$, $\text{PaCO}_2 ↑$, $\text{HCO}_3^- \text{ normal}$.
  • Metabolic Acidosis: $\text{pH} ↓$, $\text{PaCO}_2 \text{ normal}$, $\text{HCO}_3^- ↓$.
  • Compensation: If the primary problem is respiratory, the renal system (metabolic) compensates by adjusting $HCO_3^-$ retention (takes days). If the problem is metabolic, the lungs compensate by adjusting ventilation (takes minutes/hours).

Oxyhaemoglobin Dissociation Curve

• Describes the relationship between $PaO_2$ (partial pressure) and $SaO_2$ (saturation).
• Upper Flat Portion: Favours oxygen loading in the lungs ($PaO_2 > 60 mmHg$).
• Steep Portion: Favours oxygen unloading at the tissues ($PaO_2 < 60 mmHg$).
• Right Shift: Affinity decreases (easier unloading). Caused by hyperthermia (fever), acidosis, and hypercapnia (exercise).
• Left Shift: Affinity increases (harder unloading). Caused by hypothermia, alkalosis, and hypometabolism.

Radiological Interpretation: Chest X-Ray (CXR)

• Technical Quality (RIP):

  • Rotation: Medial ends of clavicles should be equidistant from the spinous processes of $T1-4$.
  • Inspiration: At least 6 anterior ribs or 10 posterior ribs should be visible above the diaphragm.
  • Penetration (Exposure): Vertebral bodies should be visible behind the heart but not clearly defined in the lower shadow.

• Film Types:

  • PA (Postero-Anterior): Gold standard; beam passes from back to front; usually done erect.
  • AP (Antero-Posterior): Beam front to back; common in ICU; magnifies the heart/mediastinum.
  • Lateral Decubitus: Used to identify small pleural effusions or pneumothorax.

• Common CXR Pathologies:

  • Consolidation: Fluid-filled spaces; appear white (opaque).
  • Collapse (Atelectasis): Volume loss leads to tracheal/mediastinal shift toward the lesion and diaphragm elevation.
  • Pleural Effusion: Fluid in pleural space; shows blunting of costophrenic angles and a "meniscus sign".
  • Pneumothorax: Air in pleural space; shows a lack of peripheral lung markings and the "deep sulcus sign" on supine films.

Electrocardiogram (ECG) Interpretation

• Normal ECG Components:

  • P-wave: Atrial depolarisation.
  • PR Segment: AV node delay.
  • QRS Complex: Ventricular depolarisation (Normal width $< 100 ms$).
  • T-wave: Ventricular repolarisation.
  • TP-segment: Key reference point for the isoelectric line.

• Rate Calculation Methods:

  • Square Counting: $\text{Rate} = 300 / \text{number of large squares between R waves}$. Sequence: $300-150-100-75-60-50$.
  • Calculator Method: $\text{Rate} = 1500 / \text{number of small squares}$.
  • Irregular Rhythms: Count complexes on a 10-second strip and multiply by 6.

• Dysrhythmias and Changes:

  • Atrial Fibrillation (AF): Disorganised atrial activity; lacks P-waves; irregularly irregular R-R intervals.
  • Atrial Flutter: "Saw-tooth" wave pattern; rapid atrial rate ($200-300 bpm$).
  • Ventricular Tachycardia (VT): Very fast ($> 160 bpm$); wide QRS complexes; life-threatening.
  • Ventricular Fibrillation (VF): Chaotic contraction; no cardiac output; requires immediate defibrillation.
  • ST Changes: Elevation indicates acute Myocardial Infarction ($MI$); depression indicates Ischaemia.

Lung Volumes and Pulmonary Function Tests

• Standard Lung Volumes:

  • Tidal Volume ($V_T$): Normal quiet breath ($\text{approx. } 500 mL$).
  • Inspiratory Reserve Volume ($IRV$): Air inhaled forcibly beyond $V_T$.
  • Expiratory Reserve Volume ($ERV$): Air exhaled forcibly after normal exhalation.
  • Residual Volume ($RV$): Air remaining after maximal forced expiration.

• Lung Capacities:

  • Vital Capacity ($VC$): $IRV + V_T + ERV$. Total usable air.
  • Functional Residual Capacity ($FRC$): $ERV + RV$. Resting volume of the system. Maintains airway patency. Reduced in supine positions.
  • Total Lung Capacity ($TLC$): The absolute total air lungs can hold ($\text{approx. } 6000 mL$ in males).

• Closing Capacity ($CC$): The volume at which small airways begin to close. Increases with age. If $CC > FRC$, small airway closure occurs during normal breathing, leading to atelectasis.

Spirometry and Ventilatory Patterns

• Simple Spirometry Measurements:

  • $FEV_1$: Forced expiratory volume in the first second.
  • $FVC$: Total volume of air forcefully expired.
  • $FEV_1/FVC$ Ratio: Key indicator of airflow obstruction.

• Patterns of Impairment:

  • Obstructive Pattern: Reduced $FEV_1/FVC$ ratio ($< LLN$). Common in COPD and Asthma. Flow-volume curve shows a concave/"scooped" shape.
  • Restrictive Pattern: Normal $FEV_1/FVC$ ratio but reduced $FVC$ ($< LLN$). Found in pulmonary fibrosis and chest wall deformities. Diagnosis requires confirmation of reduced $TLC$.
  • Mixed Pattern: Both $FEV_1/FVC$ and $FVC$ are below the Lower Limit of Normal ($LLN$).

• Bronchodilator Responsiveness (BDR): Defined as an increase of > 10\text{%} of the predicted value in either $FEV_1$ or $FVC$ after inhalation of a bronchodilator (e.g., Salbutamol).

obstructive vs. Restrictive Pathologies

• Obstructive Diseases:

  • COPD: Persistent airflow obstruction from smoking/pollutants. Comprises chronic bronchitis and emphysema.
  • Asthma: Reversible airway inflammation and hyper-responsiveness.
  • Cystic Fibrosis (CF): Genetic mutation ($CFTR$ gene) causing thick, sticky mucus.
  • Bronchiectasis: Permanent dilation of airways with excessive sputum.

• Restrictive Diseases:

  • Interstitial Lung Disease (ILD): Scarring/fibrosis of lung tissue.
  • Pleural Effusion: External fluid compressing the lung.
  • Pneumothorax: Lung collapse due to pleural air.
  • Extrinsic Causes: Obesity, scoliosis, and neuromuscular diseases (e.g., MND).