Primary spontaneous pneumothorax

01OverviewDefinition, clinical context and the essential points that orientate the chapter.

A spontaneous pleural leak separates visceral and parietal pleura and allows elastic lung recoil. Symptoms and reserve vary more than the measured rim of air, explaining the modern symptom-led pathway.

PSP is a clinical category, not proof of normal lungs. CT may reveal blebs/bullae, and smoking substantially increases risk; familial syndromes or cystic lung disease should be considered when the history is unusual.

Conservative care is active management: analgesia, observations, mobilisation assessment, education and planned review. It is not 'do nothing and discharge'.

Every intervention trades faster symptom relief/expansion against pain, hospital stay, device complications and further procedures. Shared decision-making is therefore part of guideline-concordant care.

Key points

PSP means spontaneous pleural air without known clinically apparent underlying lung disease; actively look for secondary disease rather than assuming it from age or body habitus alone.
Confirm a stable suspected pneumothorax with chest radiography and use thoracic ultrasound/CT when needed; tension physiology is a clinical diagnosis and imaging must not delay decompression.
BTS 2023 makes symptoms and physiological risk—not size alone—the main acute-management decision.
Conservative management can be considered for asymptomatic or minimally symptomatic PSP with no physiological compromise, regardless of radiographic size, provided follow-up and return access are reliable.
Ambulatory management should be considered for appropriate PSP when expertise, a defined device pathway, daily/early review and patient support are available.
When conservative or ambulatory care is unsuitable, needle aspiration or small-bore tube drainage are initial options chosen by symptoms, risk, safe access and patient preference.
High-risk characteristics include haemodynamic compromise/tension, significant hypoxia, bilateral pneumothorax, underlying lung disease, age at least 50 with significant smoking history and haemopneumothorax.
All non-admitted patients need written red flags, direct return access and planned respiratory follow-up; BTS advises review after conservative/needle management in about 2–4 weeks.
Discuss recurrence prevention after a second ipsilateral or first contralateral pneumothorax, and earlier when recurrence would be hazardous, such as prior tension or high-risk occupation.
Advise smoking cessation. Do not fly until complete radiographic resolution and then wait at least 7 days; scuba diving is generally contraindicated unless definitive preventive treatment and specialist diving assessment support return.

02AetiologyUnderlying causes, associations and risk factors, with why each one matters.

Subpleural air-space rupture

Rupture of small apical blebs or porous visceral pleura allows air into the pleural space without recognised underlying lung disease.

Smoking exposure

Tobacco and cannabis smoking increase inflammatory small-airway injury and the risk of a first event and recurrence.

Body habitus and age

Primary events are associated with younger age and a taller, leaner body habitus; these features indicate epidemiological susceptibility but do not by themselves establish the cause.

Familial predisposition

Recurrent or family-associated pneumothorax may signal inherited cystic or connective-tissue disorders even when the initial label appears primary.

03PathophysiologyThe causal sequence from the underlying abnormality to symptoms and harm.

1
Pleural air leak
A visceral pleural defect allows alveolar air to enter the normally negative-pressure pleural space, which links the underlying lesion to the observed respiratory dysfunction.
2
Elastic lung recoil
Loss of pleural coupling permits the affected lung to recoil inward while the chest wall moves outward, reducing ventilated lung volume.
3
Gas exchange change
Ventilation falls in compressed regions while perfusion persists, causing variable ventilation-perfusion mismatch according to pneumothorax size and physiological reserve.
4
Leak resolution or persistence
The defect may seal and pleural gas be absorbed, or remain open and produce continuing air leak and failure of re-expansion.

04Clinical features and red flagsSymptoms, examination findings, patterns of presentation and time-critical warnings.

Typical PSP

Sudden unilateral pleuritic pain and breathlessness, often at rest, with reduced expansion/breath sounds and hyperresonance; examination may be subtle in a small pneumothorax.

Tension physiologyRed flag

Severe distress, hypotension, tachycardia, cyanosis, altered consciousness, raised JVP or peri-arrest deterioration with unilateral reduced breath sounds; tracheal deviation is late and absence does not reassure.

Significant hypoxia/bilateral diseaseRed flag

Marked desaturation or bilateral pneumothoraces reduce reserve and are high-risk features requiring inpatient intervention/specialist care.

Possible secondary pneumothoraxRed flag

Known COPD, asthma, ILD, cystic fibrosis, infection or malignancy—or age at least 50 with significant smoking—moves management toward the higher-risk pathway.

HaemopneumothoraxRed flag

Pleural air plus fluid level, anaemia or shock suggests bleeding and requires urgent drainage and thoracic surgical involvement.

05InvestigationsWhat to request, why it matters and how to interpret it.

Investigation order

Read from the initial assessment onwards. Tests may run in parallel in urgent care; first-line, preferred, confirmatory, definitive and gold-standard labels appear only when the chapter explicitly states them.

01
Chest X-rayFirst step
Why
Confirm pleural air, laterality and approximate extent in a stable patient.
Interpretation and limitations
An expiratory film is not routinely required. Judge high-risk features and symptoms rather than applying a size-only treatment threshold.
02
Thoracic ultrasound
Why
Rapidly support pneumothorax diagnosis and guide any pleural intervention.
Interpretation and limitations
Absent sliding/B-lines and a lung point support pneumothorax in skilled hands; absence of a lung point does not exclude a very large pneumothorax. Do not delay tension decompression.
03
CT chest
Why
Resolve diagnostic uncertainty, assess an unsafe/no intervention window or investigate suspected underlying disease.
Interpretation and limitations
CT is not routine before every PSP treatment; use when it will change classification, access or recurrence planning.
04
Pulse oximetry and observations
Why
Identify physiological compromise and suitability for ambulatory/conservative care.
Interpretation and limitations
Significant hypoxia, hypotension, marked tachypnoea or worsening symptoms are high-risk regardless of measured size.
05
ECG and blood tests when clinically indicated
Why
Assess alternative chest pain, infection, bleeding or procedural risk.
Interpretation and limitations
Routine broad testing is unnecessary in an otherwise well PSP, but haemopneumothorax, sepsis or intervention warrants targeted FBC/coagulation/group-and-save.
06
Post-intervention imaging and device review
Why
Confirm response and device position/function according to the chosen pathway.
Interpretation and limitations
Clinical improvement is essential; persistent symptoms, non-expansion or ongoing leak triggers pleural-team review rather than repeated blind procedures.

06Differential diagnosisRealistic alternatives and the features that help distinguish them.

Secondary spontaneous pneumothorax

Known lung disease, older age or radiographic emphysema, fibrosis or cysts indicates a secondary event with less physiological reserve and a different management pathway.

Pulmonary embolism

Sudden pleuritic pain and breathlessness overlap, but pleural air on imaging establishes pneumothorax while thromboembolic risk may require parallel assessment.

Musculoskeletal chest pain

Reproducible local tenderness and normal respiratory examination or imaging favour chest-wall pain, provided serious intrathoracic causes have been excluded.

Bullous lung disease

A large bulla can mimic pleural air on radiography; CT or expert review avoids placing a drain into an intrapulmonary air space.

07ManagementImmediate care, first-line treatment, alternatives and escalation.

01ConservativeMinimal symptoms, no compromiseFirst stepAsymptomatic or minimally symptomatic PSP with no significant pain/breathlessness, no physiological compromise and reliable follow-up.

1Confirm diagnosis in a stable patient, assess all high-risk characteristics and provide appropriate analgesia; discuss that size alone does not mandate intervention.
2Observe long enough to establish clinical stability and safe mobilisation; supply written red flags and a direct route back for increasing pain, breathlessness, dizziness or syncope.
3Arrange respiratory follow-up and repeat radiography, commonly at 2–4 weeks after conservative/needle management; give smoking, flying and diving advice.

02AmbulatorySymptom relief without routine admissionSymptomatic PSP without instability where ambulatory expertise/device pathway, support and follow-up are available.

1Discuss ambulatory one-way-valve treatment versus aspiration/drain/conservative care, including pain, device failure and possible admission.
2Insert/manage the approved ambulatory device under ultrasound-informed pleural technique, confirm safe function and provide 24-hour contact/return instructions.
3Review through the dedicated pathway—often daily or at the device protocol interval—until air leak ceases and radiographic/clinical resolution allows removal.

03InterventionAspiration or small-bore drainageSymptoms require intervention and conservative/ambulatory management is unsuitable, declined or unsafe.

1Use thoracic ultrasound to identify a safe pleural window, obtain consent, give local anaesthesia and choose needle aspiration or small-bore drain with the patient and pleural team.
2After aspiration, reassess symptoms and imaging; failed symptom relief/re-expansion or recurrence during observation usually moves to drain/ambulatory or specialist management.
3For a chest drain, use an underwater seal or approved ambulatory valve, never clamp a bubbling drain without specialist direction, and manage persistent leak through the pleural pathway.

04RecurrenceThoracic-surgery discussionSecond ipsilateral, first contralateral, bilateral event, prolonged air leak or recurrence would carry high consequence.

1Discuss with thoracic surgery after a second ipsilateral or first contralateral pneumothorax; BTS 2026 defines prolonged leak as ongoing after 3–5 days of drain treatment and supports early discussion.
2Consider first-episode surgery when recurrence prevention is especially important, including tension presentation or high-risk occupations such as professional diving/piloting.
3Explain that VATS/open approaches and pleurodesis/bullectomy reduce recurrence but have pain, bleeding and other surgical trade-offs; individualise with the patient.

Key medicines and prescribing safety4 treatments · regimens, roles and cautions

First-line analgesia for pleuritic pain and after aspiration/device placement.

Paracetamol

1 g orally every 4–6 hours as needed, maximum 4 g in 24 hours for a typical adult; use a lower maximum in body weight below 50 kg, liver disease, malnutrition or heavy alcohol use.

Check combination products and total daily dose. Severe or escalating pain despite treatment may signal tension, bleeding or device complication and needs reassessment.

Additional anti-inflammatory analgesia for pleuritic pain.

Ibuprofen

200–400 mg orally up to three times daily with food for the shortest necessary course when an NSAID is appropriate.

Avoid or use specialist judgement with renal injury, peptic ulcer/bleeding, anticoagulation, NSAID-sensitive asthma, pregnancy or heart failure.

Local anaesthesia for aspiration, drain or ambulatory-device insertion.

Lidocaine 1% for pleural intervention

Infiltrate incrementally through skin, tract and parietal pleura, keeping total lidocaine at or below 3 mg/kg without adrenaline (10 mg/mL) unless a lower patient/product limit applies.

Calculate the total dose, aspirate before injection and monitor for local-anaesthetic toxicity; reduce in frailty or significant liver disease.

Treats hypoxaemia while definitive pleural management proceeds.

Controlled oxygen

Give only when hypoxaemic, usually targeting 94–98%, or 88–92% if at risk of hypercapnic respiratory failure; use high concentration during tension/peri-arrest resuscitation.

Oxygen is not a substitute for decompression and should not be used solely to treat breathlessness in a non-hypoxaemic stable patient.

08ComplicationsImportant consequences, why they occur and why they matter clinically.

Tension physiology

A continuing one-way leak can raise intrapleural pressure, impair venous return and cause obstructive shock, although this is uncommon in an otherwise stable primary event.

Persistent air leak

Failure of the pleural defect to seal prevents durable re-expansion and may require specialist surgical or pleural intervention.

Recurrence

Further ipsilateral or contralateral events are common enough to influence occupation, travel, diving and recurrence-prevention discussions.

Treatment-related injury

Needle or drain procedures can cause bleeding, infection, organ injury or re-expansion pulmonary oedema, reinforcing the need for appropriate selection and imaging guidance.

09Monitoring and follow-upTreatment response, safety checks and longer-term review.

During observation, trend pain, respiratory rate, SpO2, pulse, BP and mobilisation; worsening physiology triggers re-imaging and intervention.
After aspiration/device insertion, assess clinical response, air leak/device function, insertion site and appropriate follow-up imaging.
Ambulatory patients require a named review service, clear device-care instructions and immediate access for worsening breathlessness, pain, dislodgement or blockage.
For a drain, document bubbling/swinging, output and any surgical emphysema; never clamp a bubbling drain without an explicit specialist reason and monitoring.
At follow-up confirm radiographic resolution, smoking status, activity/flying advice and whether recurrence-prevention referral criteria are met.

10Special situationsVariants, exceptions and circumstances that change the usual approach.

Size no longer dictates every action

The 2023 BTS approach allows conservative care regardless of size when symptoms and physiology are minimal and follow-up is robust.

PSP is a provisional phenotype

A first pneumothorax may reveal cystic lung disease, endometriosis-related disease or a genetic syndrome; revisit classification when age, sex, recurrence, family history or CT is atypical.

Ambulatory care is a service

A valve alone is not ambulatory management. Safe care requires expertise, scheduled review, supplies and a 24-hour rescue route.

Persistent leak starts a new decision

After 3–5 days of ongoing drain leak, early thoracic-surgical discussion clarifies surgery and non-surgical options instead of passive prolonged drainage.

Lifestyle advice prevents avoidable harm

Smoking raises recurrence risk; cabin altitude expands trapped gas, and underwater pressure change can be fatal after a pneumothorax.

11Common pitfallsFrequent interpretation and management errors.

01
Using pneumothorax size alone to mandate a chest drain in a stable minimally symptomatic PSP.
02
Calling a pneumothorax primary without assessing smoking history and underlying lung disease.
03
Discharging conservative or ambulatory care without a named review pathway and direct return advice.
04
Waiting for chest X-ray in a patient with tension physiology.
05
Clamping a bubbling chest drain or applying suction automatically without pleural-team direction.
06
Omitting flying, diving, smoking and recurrence-prevention counselling.