Resp Failure Flashcards
Definition?
• Acute impairment in gas exchange between the lungs and the blood causing hypoxia with or without hypercapnia (e.g., caused by acute decompensation of chronic pulmonary disease).
D Type 1?
Hypoxic respiratory failure (type 1 respiratory failure) is hypoxia without hypercapnia and with an arterial partial pressure of oxygen (PaO₂) of <8 kPa (<60 mmHg) on room air at sea level.
D type 2?
• Hypercapnic respiratory failure (type 2 respiratory failure) is hypoxia with an arterial partial pressure of carbon dioxide (PaCO₂) of >6.5 kPa (>50 mmHg) on room air at sea level.
Risk factors?
• Smoking • Pulmonary infection • Chronic lung disease • Obstruction • Alveolar abnormalities /perfusion abnormalities • CHF • Msk problems • Toxic fumes • Spinal thoracic trauma • Vascular occlusion • Pneumothorax Hypercoagulability
ddx?
Metabolic acidosis
• Anxiety
• Sleep apnoea
Obesity
aetiology?
• Hypoventilation • Diffusion impairment • Pulmonary shunt • V/Q mismatch High altitude
CP?
• RFs • Trauma • Dyspnoea • Confusion • Tachypnoea • Accessory breathing muscle use • Stridor • Inability to speak • Retraction of intercostal muscles Cyanosis
P-1-hypoventilation?
• as lower resp rate and tidal volume so a lower amount of air is exchanged per minute
• This means less oxygen enters the alveoli and arteries so less Pao2 and more PCO2
• The alveolar-arterial gradient is normal so adding more oxygen corrects this.
• Diffusion impairment-
• Lower SA or increased thickness of membranes increasing the diffusion gradient of gases but it is unable to diffuse through.
Need to correct problem
P-1-pulmonary shunt?
- Venous blood on right side enters left and systemic circulation without getting oxygenated within the alveoli-normal perfusion poor ventilation
- Cannot exchange gases in the alveoli so hypoxaemia
- Cannot be corrected by oxygen as it will not enter the blood and due to hypoxic VC, blood will bypass the lungs
P1-V/Q mismatch?
• Decreased-decreased ventilation or over-perfusion-too much blood, not enough oxygen to diffuse into it
Increased-decreased perfusion or over-ventilation-too much oxygen, not enough blood to diffuse into
P-1-High altitude?
• Barometric pressure decreases so lower alveolar PO2
• PAO2 = FIO2× (PB – PH2O) – PACO2/R
• The lower alveolar PAO2 decreases the PaO2 too but the gradient remains normal, but the body increases ventilation to increase oxygen.
At high altitudes, hyperventilation occurs, causing respiratory alkalosis and polycythaemia
P2?
• Reduced central respiratory drive, e.g.,, opioid overdose or head injury
• Upper airway obstruction (foreign body,edema, infection)
• Late severe acuteasthma, COPD
• Peripheral neuromuscular diseases, e.g., Guillain–Barre syndrome, myasthenia gravis, botulism
Respiratory muscle fatigue
First line investigations?
• Pulse oximetry less than 80%-use nail or earlobe
ABG-pH <7.38; PaO₂ <8 kPa (<60 mmHg) (or <6.7 kPa [<50 mmHg] in chronic lung disease) on room air; PaCO₂ >6.7 kPa (>50 mmHg) on room air
Second line investigations?
- FBC-infections
- D dimer-indicates thromboembolism
- Serum bicarbonate high
- ECG-see underlying cause
- CXR-infection or pneumothorax or obstructions
- Pulmonary function tests-prognosis
- Toxicology-drug causes
- CT-PE
- CTPA-MI or vascular causes
- VQ scan-excludes PE
- Capnometry-monitoring
- US-ventricular filling
Management obstruction?
- airway clearance and ABCDE
- Laryngoscopes, bronchoscope, cricothyrotomy, tracheostomy,
- Oxygen
- Most least invasive way first
- 94 to 96% target
- Treat underlying cause
- Treatment may include antibiotic therapy for infection, adrenaline (epinephrine) for anaphylaxis, opioid reversal with naloxone, bronchodilation/corticosteroid therapy for chronic lung disease, decompression/chest tube insertion for pneumothorax, fluid resuscitation for hypovolaemia, thrombolysis/embolectomy for pulmonary embolus, radiotherapy for malignancy, and surgery for trauma or malignancy.
