Understanding Paroxysmal Nocturnal Dyspnoea (PND) and Its Connection to Sleep Apnoea

Disclaimer: This article is for educational purposes only and does not replace medical advice. If you are experiencing symptoms of PND, sleep apnoea, or any form of nocturnal breathing difficulty, please consult your GP or a specialist. Seek urgent medical attention if you have severe shortness of breath or chest pain.

Understanding nighttime breathlessness and its connection to sleep disorders

Paroxysmal Nocturnal Dyspnoea (PND) is a distressing condition characterised by sudden episodes of shortness of breath during sleep, often waking the individual and forcing them to sit upright to catch their breath. It is commonly associated with heart failure, but can also be linked to other respiratory and sleep-related conditions such as sleep apnoea. Understanding the similarities, differences, and potential overlap between PND and sleep apnoea is important for diagnosis and management.

What is Paroxysmal Nocturnal Dyspnoea (PND)?

PND is not a disease in itself, but rather a symptom of an underlying condition. It typically occurs 2–4 hours after falling asleep and is relieved by sitting or standing up.

Causes of PND

The most common cause is congestive heart failure, where fluid builds up in the lungs during the night due to a weakened heart. Other contributing factors may include:

Pulmonary diseases (e.g., COPD, asthma)
Fluid overload (kidney disease or excessive IV fluids)
Obesity-related breathing issues
Sleep disorders such as obstructive sleep apnoea

Symptoms of PND

Sudden shortness of breath at night
Coughing or wheezing during episodes
Waking with a sense of panic or suffocation
Needing to sit upright or sleep propped with pillows
Fatigue and poor sleep quality

What is Sleep Apnoea?

Sleep apnoea is a condition where breathing repeatedly stops and starts during sleep. The most common type, Obstructive Sleep Apnoea (OSA), occurs when the airway is blocked by relaxed throat muscles.

Symptoms of Sleep Apnoea

Loud snoring
Repeated pauses in breathing during sleep
Morning headaches
Daytime drowsiness and fatigue
Difficulty concentrating

The Link Between PND and Sleep Apnoea

Although PND and sleep apnoea are distinct conditions, they can be interrelated:

Breathing Disturbances – Both conditions cause sudden interruptions in breathing during sleep, leading to awakenings and anxiety.
Cardiac Strain – Sleep apnoea increases the risk of high blood pressure and heart failure, both of which are closely linked to PND.
Fluid Shifts at Night – In heart failure patients, lying flat redistributes fluid to the lungs, triggering PND. In sleep apnoea, the airway obstruction worsens this fluid shift and breathing effort.
Overlapping Symptoms – Fatigue, poor sleep, and nighttime awakenings are common in both conditions, which sometimes makes diagnosis challenging.

Diagnosis

PND is typically diagnosed through medical history, echocardiogram, chest X-ray, and heart function tests.
Sleep apnoea is usually confirmed via a sleep study (polysomnography).

Because the two conditions can overlap, doctors may recommend both cardiac and sleep evaluations to pinpoint the root cause.

Treatment and Management

For PND

Treat underlying heart failure with medication (diuretics, ACE inhibitors, beta-blockers).
Lifestyle changes: reducing salt intake, managing fluid balance, weight management.
Sleeping in an elevated position with pillows.

For Sleep Apnoea

CPAP (Continuous Positive Airway Pressure) therapy to keep airways open.
Weight loss, avoiding alcohol and sedatives.
Surgery in severe airway obstruction cases.

Comparison: PND vs Sleep Apnoea

Feature	Paroxysmal Nocturnal Dyspnoea (PND)	Sleep Apnoea
Definition	Sudden episodes of breathlessness that wake a person from sleep, usually caused by heart failure.	A sleep disorder where breathing repeatedly stops and starts due to airway obstruction or brain signalling problems.
Timing	Occurs 2–4 hours after falling asleep.	Occurs throughout the night in repeated cycles.
Cause	Most often linked to congestive heart failure; fluid backs up into the lungs when lying flat.	Caused by airway blockage (obstructive) or brain signal issues (central).
Symptoms	Waking up gasping for air, coughing, wheezing, relief when sitting up.	Loud snoring, witnessed pauses in breathing, morning headaches, daytime fatigue.
Risk Factors	Heart disease, kidney disease, obesity, high fluid intake.	Obesity, large neck circumference, alcohol use, family history, airway anatomy.
Diagnosis	Echocardiogram, chest X-ray, heart and lung tests.	Sleep study (polysomnography).
Treatment	Managing heart failure (medications, lifestyle changes, fluid restriction).	CPAP therapy, weight loss, surgery in severe cases.
Overlap	Both cause disturbed sleep, fatigue, and nighttime awakenings.	Sleep apnoea can worsen heart failure, increasing risk of PND.

Conclusion

Paroxysmal Nocturnal Dyspnoea and sleep apnoea are both conditions that cause nighttime breathing difficulties but arise from different underlying mechanisms. However, they can interact and worsen each other, especially in patients with heart failure or obesity. Anyone experiencing sudden nighttime breathlessness should seek medical advice promptly, as it may be a warning sign of serious underlying illness.