SN5
SHORT NOTE
5M
Write a short note on Cheyne–Stokes breathing.
Definition
Cheyne–Stokes breathing = a form of periodic breathing in which phases of gradually increasing then decreasing tidal volume (crescendo–decrescendo) alternate regularly with periods of apnoea lasting 10–30 s.Cycle length 45–90 s.
Mechanism
Two factors required
1. Prolonged lung-to-brain circulation time → chemoreceptors sample blood several seconds old → response always out of phase
2. ↑ gain of respiratory centre to CO2 (over-response)
↑ PaCO2 → Hyperventilation → Overshoot → ↓ PaCO2 below apnoeic threshold → apnoea → CO2 accumulates again → Cycle repeats
Causes
Physiological
- Sleep in normal infants
- Healthy adults at high altitude
Pathological
- Congestive cardiac failure — commonest cause (prolonged circulation time)
- Cerebral lesions — ↑ ICP, stroke, meningitis, tumour
- Uraemia
- Narcotic and barbiturate poisoning
Differences from Biot’s Breathing
| Feature | Cheyne–Stokes | Biot's (ataxic) |
|---|---|---|
| Pattern | Smooth waxing and waning | Irregular in depth and timing |
| Apnoea | Regular, predictable | Irregular |
| Lesion | Cerebral / cardiac | Medullary damage |
Other Abnormal Breathing Patterns
| Pattern | Description | Lesion / cause |
|---|---|---|
| Kussmaul | Deep, rapid, sighing | Metabolic acidosis (DKA, uraemia) |
| Apneustic | Prolonged inspiratory gasps | Lower pontine lesion |
| Ataxic (Biot) | Completely irregular | Medullary lesion |
| Agonal | Occasional gasps | Terminal brainstem failure |
Applied Aspects
- In an awake adult at sea level it is a grave sign — advanced cardiac failure or brainstem disturbance
All questions in Respiratory System
- Q1Describe the mechanics of breathing. Discuss the muscles involved and the pressure changes occurring during one normal respiratory cycle. Add a note on lung compliance. ★
- Q2Describe the transport of oxygen in the blood. Draw and explain the oxygen–haemoglobin dissociation curve and enumerate the factors that shift it. ★
- Q3Describe the nervous and chemical regulation of respiration. Add a note on the Hering–Breuer reflex. ★
- Q4Describe the transport of carbon dioxide in the blood. Explain the chloride shift and the Haldane effect. ★
- Q5Define the ventilation–perfusion ratio. Describe its regional variation in the upright lung and discuss the consequences of V/Q mismatch. ★
- SN1Write a short note on pulmonary surfactant. ★
- SN2Define lung volumes and capacities. Give their normal values and state which of them cannot be measured by spirometry. ★
- SN3Classify hypoxia. Give the causes and effects of each type. ★
- SN4Write a short note on cyanosis.
- SN5Write a short note on Cheyne–Stokes breathing.
- SN6Define dead space. Describe its types and explain its significance in alveolar ventilation. ★
- SN7Describe the physiological changes that occur during acclimatisation to high altitude. ★