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Chemical Pathology of Respiratory Disease - Coggle Diagram
Chemical Pathology of Respiratory Disease
ABG Analysis
Arterial Blood Gas
Function
Provides information relating to respiratory function and acid-base balance
Blood Sampling
Arterial / arterialised blood
Anticoagulated (heparinised) syringes
Removal of air bubbles before equilibration
Analysed immediately / transported on ice
Preventing continued metabolism in WBCs
PO2: 11.1 - 14.1
PCO2: 4.1 - 6.7
pH 7.35 - 7.45
H+: 36 - 45
HCO3: 21 - 31
Uses
Establish diagnosis
Asses illness severity
Guid treatment
Monitor progress
Factors Facilitating Tissue Oxygenation
Alveolar ventilation
Alveolar gas diffusion and function
Pulmonary and systemic blood flows
O2 binding to Hb in alveoli and O2 release from Hb tissue
Assessment of Tissue Oxygenation / Hypoxia
Clinical
Central cyanosis
Hypotension
Organ dysfx
ARDS
ARF
Mental obtundation
Lab
Plasma/blood lactate
Arterial O2 saturation (SaO2)
Arterial partial pressure of O2 (PaO2)
Respiratory Failure
Type 1
Hypoxaemia with normo or hypocarpnia
:arrow_down: O2
:arrow_down: / :arrow_right: Co2
Cause
Failure of O2 transfer across alveolar membrane
Ventilation-perfusion (V/Q) defects with resulting right to left shunting of deoxygenated blood
Pneumonia
PE
Pneumothorax
Pulmonary Oedema
Acute asthma
ARDS
Fibrosing alveolitis
COPD
Type 2
Hypoxia with hypercapnia
Clinical Features of Hypercapnia
Confusion
Drowsiness
Headache
Bounding pulse
Warm extremities
Flapping tremor (Asterixis)
Papilloedema
Causes
1 COPD
Opiate / benzo toxicity
Flail chest injury
Neuromuscular disorders
Inhaled foreing body
Obstructive sleep apnoea
KYphoscoliosis
Supplemental O2 therapy
Chronically high PCO2
CO2 receptrs in SND resp centre become desensitised
Hypoxic drive becomes more important CNS stimualtion of ventilation
Overenthusiatic O2 may eliminate hypoxic drive as PO2 normalises, causing severe rise in PO"
Supplemental O2 must be carefully administered and monitored
Endocrine Manifestations of Bronchial Tumours
Pleural Fluid Analysis
This is very abridged
Acid-Base Balance
Mechanisms
Buffers
Respiratory Response
Renal Response
Buffers
Intracellular
Bone
Proteins eg Hb
Extracellular bufferes
Phosphate (HPO4)
Bicarbonate buffer (HCO3)
Henderson-Hasselbach Equation
pH = pKa + log10 ([A–]/[HA]
pH = 6.1 + log HCO3/H2CO3
pH = 6.1 + log HCO3/0.03PCO2
i dunno
Respiratory
Regulates PCO2
Increased or deacreased ventilation
Renal
Regulates HCO3
Reabsorption of HCO3 in proximal tubule
Generation of HCO3 in distal tubule
Titratable acidity (HPO4 buffers throughout tubule)
Slower than resp response
Disorders
Acidosis /Acidaemia
Respiratory
Causes
• CNS depression e.g. trauma, drug OD
• Neuromuscular disorders
• Chest wall disease e.g. kyphoscoliosis
• Pleural effusions
• COPD
• Pulmonary oedema
Metabolic
Alkalosis / Alkalaemia
Respiratory
Metabolic
