Give a summary of the pulmonary anatomy and physiology, including:
- ventilation
- compliance
- resistance
- alveolar-capillary network /alveolar ventilation
Pulmonary ventilation
> Active process: inspiration occurs due to contraction of muscles (using ATP) that cause negative intrathoracic pressure
> Diaphragm main muscle to displace thoracic cage
> Flow is generated due to pressure gradient from atmosphere to alveoli
> Expiration is passive after intrathoracic (specifically intraalveolar) pressure is greater than atmosphere
Compliance:
> Definition: extent to which lungs expand per unit increase in transpulmonary pressure or stretchiness
> Volume change per unit pressure change:
○ C= V / P
> Normal is 200ml.cm of water
> Low compliance- lungs are stiffer and increase effort required to inflate alveoli
> High compliance- easy inflation + loss of elasticity
Resistance
> Definition: obstruction to flow in the airways mainly larger
> Resistance is normally low, most arising from upper airways
> Increase in resistance= oedema, obstruction, spasm
Alveolar-capillary network
> Each alveolus surrounded by capillary network.
> Alveoli - thin epithelial cells + capillary- thin endothelial cells lining alveolar-capillary
Alveolar ventilation
> Dead space= does not participate in gas exchange
> Functional dead space= alveoli not perfused with blood but expanded with air
What are some pre-op risks and assessments for pulmonary complications?
• Peri-operative mortality rate= the highest risk is at 24hrs or 30 days after
• Risk factors: urgency, age, condition
• Pre operative pulmonary risk factor evaluation:
○ History and physical exam, chest x ray, arterial blood gas, lung function tests, type of surgery, exercise tolerance test
Summarise the post op risks of pulmonary complications.
• Risk factors: age, obesity, health status, smoking, lung disease
• Post operative pulmonary complications:
○ Complications: bronchospasm, cough, atelectasis, hypoxaemia, pneumonia
○ Risk factors- Low pre op SpO2, age, pre op anaemia, surgery duration, emergency surgery
Discuss the characteristics and treatment for bronchospasm.
- intraoperative complication = uncommon 2%
- Clinical manifestations: wheeze, tachypnea, hypercapnia
- histamine release causing mast cells (inflammatory response) degranulation occurs due to reflex bronchoconstriction due to tracheal stimulation from secretions, suctioning
Treatment= remove the cause, beta 2 agonist
Discuss reasons and characteristics of coughing.
- coughing is really complex can be good or bad by using extra energy if you have sutures etc.
- usually initiated in larynx and tracheo bronchial tree
- it is a protective mechanism due to airway irritation in large airways
most sensitive areas= larynx, carina, trachea, major bronchi - post op reasons= dry airway, irritated upper airway
Discuss dyspnoea characteristics
- It is a subjective sensation of uncomfortable breathing
- common symptom of respiratory distress
- V/Q mismatch
- lung disease
- may relate to stretch receptors
examples:
there is paroxysmal nocturnal dyspnoea (sudden attack) which is an acute shortness of breath at night.
Also posture-induced dyspnoea: orthopnoea= lying position, characteristic of heart failure.
assess it by asking patient to rate it 1-10.
Describe Atelectasis.
> It is an incomplete expansion or extension of the lungs
diminished volume affect part of all of the lung
common post operative pulmonary complication: especially upper abdominal and thoracic surgery
usually bi-basal and segmental
pathophysiology= decrease expansion and lung compliance, retained airway secretion, post operative pain
Clinical manifestations: can be asymptomatic, minor to severe symptoms, depends on lung collapse. cough and dyspnoea common. Hypoxemia, tachycardia, hypotension, pneumonia.
Diagnosed through a chest x ray (it shows no sharp edges of the lungs, dark shadow is not seen as much) , base of the lung sounds and ABG symptoms
treatment- early mobilisation, chest physiotherapy, coughing and deep breathing, positive pressure ventilation, antibiotics.
Describe characteristics of hypoxia (diagnosis, manifestations, pathophysiology, treatment)
• Low blood tissue oxygen level > can result in tissue hypoxia where tissue cells die which is a significant problem
• Common condition in many post operations
• Often combined with atelectasis
• Causation: hypoventilation, V/Q mismatch
• Pathophysiology:
○ Decreased minute ventilation
○ Shunting of gas volume from under ventilated alveoli
○ Decrease in gas volume to under perfused alveoli
Diagnosis: clinical presentation, oxygen saturation, ABG
Treatment: REVERSE CAUSE, supplement oxygen, positioning, positive pressure ventilationExplain pleural effusion (diagnosis, pathophysiology, treatment, signs)
- Fluid in the pleural space: common in thoracic and upper abdominal surgery (can cause atelectasis)
- 2 types: transudative (water and protein poor) and exudative (protein rich)
- Causation: imbalance between fluid production and removal, inadequate lung expansion, disruption to pleural membrane
- Clinical signs: cough, dyspnoea, pleural friction, decreased in breath sounds
- Diagnosis: chest x ray,
- Treatment: if patient is active is resolves usually, chest physiotherapy, oxygen therapy (if not resolved)
Describe Pneumonia (diagnosis, treatment, signs)
- Occurs within 5 days of surgery
- Signs: Fever, leucocytosis, increased secretions, pulmonary infiltrates on chest xray
- Diagnosis: controversial- generally all patients suspected with x ray infiltrates
- Difficult because many other conditions similar- atelectasis and pulmonary oedema
- Treatment: oxygen, analyse cultures, chest physiotherapy, positioning, positive airway pressure
Explain respiratory and metabolic acidosis/alkalosis.
○ Metabolic acidosis= PaCO2 and HCo3 decreased
○ Respiratory acidosis the opposite ^
○ Respiratory alkalosis = PaCO2 and HCo3 decreased ○ Metabolic alkalosis opposite
What are you assessing when auscultating breath sounds ?
- character of breath sounds
- presence of abnormal (adventitious) sounds
- character of spoken/whispered voice
What are normal breath sounds and where are they heard?
> Tracheal (heard over the trachea): the breath sounds are harsh and sounds like air being blown through a pipe.
> Bronchial (large airways in the anterior chest near the 2nd and 3rd intercostal space): not as harsh as tracheal, more tubular and hollow sounding, loud and high pitch with a short pause, expiratory sounds last longer than inspiratory.
> Broncho-vesicular (heard in the centre part of the 1st and 2nd intercostal spaces, anterior chest- need to know normal sound of this): softer than bronchial, equal inspiration/expiration, abnormalities in pitch and intensity are often more easily detected.
> Vesicular: (between 4th and 5th intercostal): soft blowing or rustling sounds, normally throughout inspiration, may be harsher in children, elderly, obese, and muscular people.
What are two types (two main ones) of adventitious breath sounds?
> Crackles: consolidation of fluid or sputum, air moves abnormally through airways (vibrating with fluid)
> Wheeze: high pitch, airway narrowing (e.g. asthma)
Describe management of post operative respiratory complications.
> adequate and systematic pre-operative assessment (history, their surgery, the disease process, patient status)
identify high risk patients: exisiting pulmonary disease, airway complications, previous post-operative pulmonary complications
Lung protection ventilation: lower volumes improved patient outcomes
