Lung Diseases Flashcards
What are the causes of hypoxaemia
V/Q mismatch Alveolar hypoventilation Impaired diffusion: pulmonary fibrosis Low partial pressure of inspired oxygen Anatomical R-L shunt: PAVM lobar pneumonia - deoyxgenated bypassing capillary bed of lung - won't respond well to O2 therpay
What is the PaO2 for hypoxaemia
Less than 8kPa
What is the most common cause of arterial hypoxaemia
V/Q mismatch. Ventilation and perfusion must be exactlymatched
What happens in regions of high ventialtion
High blood flow i.e. base of lungs
What happens in regions of low ventilation
Low blood flow
What is a shunt alveolar unit
Va/Q = 0
Alveolar that are perfused but not ventilated. Q>V. Wasted perfusion
What is dead space
No perfusion. Gas makeup in alveolar same as room air - ventilation but no perfusion. Q
What is hypercapnia
PaCO2>6 kPa
What is alveolar respiration determined by
RR and tidal volume
What is T1 resp failure
Normal CO2 with hypoxaemia
What is T2 resp failure
Hypoxaemia and hypercapnia
How is alveolar respiration calculate
Va=Ve-VD
What are the two responses to O2 therapy
PaCO2 and clinical state may improve or px may become drowsy
What is the classical teach of what happens when px with COPD is given O2
Px with COPD rely on their hypoxia ventilatory drive due to blunted sensitivity to CO2 and H+
Hypercapnia results from a suppression of hypoxic ventilatory drive causing alveolar hypoventilation
What may actually happen when px with COPD is given O2
Worsened Va/Q matching due to attenuation of hypoxic pulmonary vasoconstriction - directs blood to areas of lung that are better ventilated. Giving O2 increase partial pressure and releases vasoconstriction, but not does increase ventilation. Decreased binding affinity of haemoglobin or CO2. Decreased Ve
What is hypercapnic respiratory failure caused by
Acute (on chronic) imbalance in load-capacity-drive
relationship
Caused by defect in each area or combination
What are examples of drive failure
Drive failure: cortical and brain stem lesion (encephalitis, ischaemia, haemorrhage), drugs (sedative, opioids), metabolic alkalosis (loop diuretics - reduces threshold of CO2 needed)
What are examples of load impedance
Elastic load - pulmonary infection, alveolar oedema, pleural effusion
Resistive load - bronchospasm, UAO, OSA
What is auto intrinsic PEEP
Incomplete expiration prior to the initiation of the next breath causes progressive air trapping (hyperinflation). This accumulation of air increases alveolar pressure at the end of expiration.
What are underlying conditions of resp failure
COPD, pneumonia, pulmonary oedema (cardiogenic, non-cardiogenic), pulmonary embolism, pulmonary fibrosis, asthma
How is resp failure assessed
ABC
Assess vital signs
Oxy-haemoglobin sats (>92% excludes hypoxia unless CO poisoning)
ABG analysis - asses for hypercapnia (hypoventilation from Duchenne’s)
If pH of venous gas is greater than 7.34, very unlikely to have resp failure (no need for ABGs)
How is resp failure managed
Treat underlying condition
Hypoxia kills - titrated oxygen
Non benefit from oxygen if not hypoxic - stroke, MI
Oxygen may worsen hypercapnia (tissue injuries are delivered by free radicals, increasing O2 increases free radicals. High O2 can cause vasoconstriction of the coronary and cerebral vessels)
Oxygen is not ventilation
What are the four types of resp support
Oxygen
Non-invasive ventilation (NIV)
Invasive mechanical ventilation (IMV)
Extra-Corporeal Membrane Oxygentation (ECMO)
What are the clinical features of resp failure
– Confusion
– Cyanosis
– Dyspnoea
– Somnolence / drowsiness
What are the benefits of NIV
Patient remains conscious
Maintains structural host defence system
Level 2 support
Positive pressure ventilators used more often
What are the benefits of invasive ventialtion
Greater control of ventilation
Secure ventilatory delivery
Level 3 support
Gold 3 standard treatment
What is given in severe resp failure
ECMO, VA for paeds
What is the pleura
Lung lining - parietal and visceral
What is pleural effusion
Fluid falls to bottom of pleural space usually
Decreased expansion on side of fluid
Mediastinum shifted away from side of fluid and trachea)
What are the signs of pleural effusion
Stony dull percussion
Breath sounds reduced - bronchial breathing at level of effusion
Vocal resonance reduced
Where is thoracentesis and where is it performed
An invasive procedure to remove fluid or air from the pleural space for diagnostic or therapeutic purposes.
Go above rib to avoid neuromuscular bundle
What is an exudate
Thick fluid - over 35g/L
What is a transudate
Thin fluid - less than 25g
What is pleural fluid protein is between 25-35
Use Light's criteria: Exudate if one or more: Pleural protein/serum protein over 0.5 Pleural LDH/serum LDH is >0.6 Pleural LDH is 2/3 upper limit of lab normal LDH
What are the causes of transudates
Systemic failures: Left ventricular failure, liver cirrhosis Hypoalbuminaemia Peritoneal dialysis Hypothyroidism Nephrotic syndrome Mitral stenosis
What are the causes of exudates
Problems local to lungs: Malignancy, parapneumonic effusions, TB PE Rheumatoid arthritis Other autoimmune pleuritis
What should pleural pH be
Around 7.2. Less than 7.2 - complicated paraneumonic effusion. Indication for tube drainage
What is empyema
Collection of pus in the pleural cavity
What can strep milleri cause
Grows on teeth - can cause bacterial endocarditis
What are malignant pleural effusions
Lung, breast, ovarian cancer
Lymphoma
Medial survival 4-6 motnhs
Describe spontaenous pneumothorax
Can be primary (absence of underlying lung pathology) or secondary (due to presence of underlying lung pathology)
What is tension pneumothorax
Forms due to one way valve where air can enter the pleural space upon inspiration, but not lave. Should have contralateral tracheal deviation, hypotension, tachy, hypoxia, increased JVp
What is restrictive lung disease
Clinical syndrome, reduced lung compliance, reduced lung volume
Describe normal respiration
Diaphragm and inspiratory muscle contract -> thorax expands -> Intrapleural pressure becomes subatmospheric -> increase in trans-pulmonary pressure -> lungs expand -> Alveolar pressure becomes subatmoshperic -> air flows into alveoli
What are the four types of interstitial lung disease
ILD of known association
Idiopathic interstitial pneumonia
Granulomatous ILD
Miscellaneous ILD
Describe granulomatous ILD
Sarcoidosis:
Multisystem granulomatous disease
Pulmonary most commonly affect organ
Range of pulmonary involvement including lung fibrosis
Describe idiopathic interstitial fibrosis
Usually interstitial pneumonia histologically
Male predominance, progressive disease
Associated with finger clubbing
What is hypersensitivity pneumonitis
Reaction to exposure including bacteria, fungi, avian proteins, animal proteins
What is pneumonconiosis
Occupational lung disesae - coal workers pneumoconiosis, silicosis, berylliosis, asbestosis
What is acute respiratory distress syndrome
Acute lung injury - sepsis, toxic inhalation, trauma, drugs, pancreatitis
What are the symptoms of restrictive lung disease
Breathlessness: others due to underlying disease, but may include
Dry cough, wheeze, chest pain, haemoptysis, fever, myalgia, weight loss, weakness
What are the signs of restrictive lung disease
General - tachypnoea, use of accessory muscle, cyanosis
Other signs - chest or spine deformity, obesity, reduced chest expansion, crackles (fibrosis), wheeze
What investigations need to be carried out
Spirometry - FEV1/VC ratio unchanged
Flow volume loop - inspiratory moves to the left. Shape remains the shame
What is the management step for restrictive lung disease
Conservative, pharmacological, oxygen, surgery, ventilatory support
What is spirometry
Measurement of expire and inspired flows and volumes
What is FVC
Forced vital capacity
What is VC
Total volume of gas exhaled after breathing in total lung capacity
What is normal ratio
FVC should be same as VC
What if FVC
Airflow obstruction
How is reversibility defined
Increase in FEV1
following BD of >12% from baseline → significant
reversibility
What does increase in residual volume indicate
Gas trapping - can be due to airway collapse
What is above horizontal axis in flow volume loop
Expiratory
What is below horizontal axis in flow volume loop
Inspiratory
What does obstructive lung disease look like on flow volume loop
Scooping of expiratory curve
What does restrictive lung disease look like on flow volume loop
Miniature version of normal volume
What is the gold standard of lung volume measurement
Body phethymosgraph - gold standard
Inert gas dilution - method underestimates volumes in px with airflow obstruction
What causes an increase in FRC and RV
Intrapulmonary - airway obstruction
Extra pulmonary - expiratory muscle weakness
What causes increased TLC
Emphysema
What causes decreased TLC
Intrapulmonary: pneumonectomy, collapsed lung, consolidation, oedema, fibrosis
Extra pulmonary: pleural disease, rib cage deformity, respiratory muscle weakness
How to measure gas exchange
CO - Measure of gas diffusion from lung to blood AND the combination of gas with Hb.
What is TLCO
Reflects the ability of the lung to transfer gas from lung to blood
What is normal for standardised residual
Between -1.64 to +1.65
What is bronchiolitis obliterans
Inflammatory obstruction of the lung’s tinniest airways
