Clinical Drowning?
When the Lungs Need Washing
There are very few circumstances in medicine where deliberately filling a patient’s lung with litres of fluid could reasonably be described as treatment.
In a healthy lung, uncontrolled filling of the alveoli with water or saline would be profoundly dangerous. Gas exchange would be lost, intrapulmonary shunting would increase dramatically, and excessive hydrostatic pressure or rapid instillation could cause severe pulmonary injury, including barotrauma and pneumothorax.
Yet in Pulmonary Alveolar Proteinosis — PAP — one of the established treatments involves doing something that initially appears almost contradictory.
The patient is anaesthetised.
The two lungs are separated.
One lung is ventilated.
The other is deliberately filled with litres of warmed saline, drained, refilled and drained again until the material obstructing its alveoli has quite literally been washed away.
It is called Whole-Lung Lavage — WLL.
It might superficially resemble controlled drowning.
In reality, it is a remarkable application of respiratory physiology, specialist thoracic anaesthesia and lung isolation.
What is Pulmonary Alveolar Proteinosis?
Pulmonary alveolar proteinosis is a rare disorder characterised by the abnormal accumulation of surfactant-rich lipoproteinaceous material within the alveoli.
Pulmonary surfactant is essential to normal lung function.
Produced primarily by type II pneumocytes, surfactant reduces surface tension within the alveoli and helps prevent alveolar collapse during expiration.
Under normal circumstances surfactant is continuously produced, recycled and removed.
Alveolar macrophages play an important role in that clearance.
In PAP, this system becomes dysfunctional.
Instead of being efficiently removed, surfactant and associated cellular material accumulate within the alveolar spaces.
The alveolar-capillary membrane may initially remain structurally intact, but the airspace itself becomes progressively occupied by material that should not be there.
Oxygen must therefore travel through an increasingly ineffective gas-exchange environment.
The result is impaired diffusion, ventilation-perfusion mismatch, intrapulmonary shunting and ultimately hypoxaemia.
Why Does PAP Occur?
PAP is not a single disease.
Several different mechanisms can produce the same clinical result.
Autoimmune PAP
The majority of adult cases are autoimmune.
Patients develop antibodies against Granulocyte-Macrophage Colony-Stimulating Factor — GM-CSF.
GM-CSF is essential for normal maturation and function of alveolar macrophages.
When GM-CSF signalling is disrupted, the macrophages become less effective at processing and clearing pulmonary surfactant.
Surfactant consequently accumulates within the alveoli.
Current European Respiratory Society guidance identifies autoimmune PAP as the commonest form and recommends quantitative GM-CSF antibody testing as part of its diagnosis. (PubMed Central (PMC))
Secondary PAP
Secondary PAP occurs when another condition interferes with macrophage number or function.
Associations include:
- haematological malignancy
- myelodysplastic disorders
- immunodeficiency
- some infections
- occupational or environmental exposure to certain dusts and particulates.
Congenital and Hereditary PAP
Much rarer forms can result from genetic abnormalities affecting surfactant metabolism or the GM-CSF receptor pathway.
These may present in infancy or childhood.
How Does PAP Present?
The disease often develops gradually.
Typical symptoms include:
- progressive exertional breathlessness
- declining exercise tolerance
- cough
- sputum production in some patients
- chest discomfort
- fatigue
- hypoxaemia
- fever or sweats where infection is present.
Royal Brompton notes that patients may deteriorate almost imperceptibly because the symptoms can develop slowly. (Royal Brompton NHS Trust)
Some patients have quite striking radiological abnormalities while reporting comparatively modest symptoms.
Others develop severe gas-exchange impairment and respiratory failure.
What Does PAP Look Like?
High-resolution CT typically demonstrates:
ground-glass opacification
together with
interlobular septal thickening.
This produces the characteristic appearance known as:
“Crazy paving.”
Crazy paving is not unique to PAP, but combined with the appropriate clinical picture it can be strongly suggestive.
Bronchoscopy with bronchoalveolar lavage can produce characteristically cloudy or milky fluid containing accumulated surfactant material.
Modern ERS guidance recommends bronchoalveolar lavage as part of the diagnostic work-up where PAP is suspected, while lung biopsy is generally unnecessary unless uncertainty persists. (ERS Publications)
Morbidity
PAP can range from relatively mild disease to profound respiratory disability.
Patients may develop:
- chronic exertional dyspnoea
- severe exercise limitation
- persistent hypoxaemia
- requirement for supplementary oxygen
- recurrent respiratory infection
- repeated requirement for whole-lung lavage
- respiratory failure.
There is also another important consequence of macrophage dysfunction.
Alveolar macrophages do considerably more than remove surfactant.
They are part of the lung’s innate immune defence.
Patients with PAP therefore have an increased susceptibility to infection, including potentially serious opportunistic infections.
A 2026 systematic review of autoimmune PAP found substantial effects on exercise capacity, quality of life and respiratory health, together with an increased rate of serious infection. (PubMed Central (PMC))
Mortality
The prognosis of PAP varies markedly according to the type of disease.
Modern outcomes for autoimmune PAP can be excellent.
A 2026 systematic review reported five-year survival in contemporary autoimmune PAP cohorts of approximately 97.7–100%. (PubMed Central (PMC))
However, this should not imply that PAP is benign.
A 2025 pooled analysis of 3,278 patients with different forms of PAP found overall reported mortality of 9.5%, with respiratory failure accounting for approximately 46% of deaths and pulmonary infection for around 18%. Secondary PAP carried substantially greater mortality than non-secondary disease. (PubMed Central (PMC))
Modern treatment has therefore changed the natural history considerably, particularly in autoimmune disease.
The History of Treatment
Pulmonary alveolar proteinosis was described as a distinct clinical entity in 1958.
Early treatments were understandably experimental.
Antibiotics, corticosteroids and attempts to chemically dissolve the intra-alveolar material were tried.
Agents including potassium iodide, trypsin, streptokinase, heparin and acetylcysteine were investigated.
Then came a strikingly simple idea.
If the alveoli were physically full of abnormal material:
why not wash it out?
Whole-lung lavage developed during the early 1960s and became established following the work of Juan Ramirez-Rivera and others.
The basic principle has survived for more than sixty years. (PubMed Central (PMC))
Modern Treatment
Whole-lung lavage is no longer the only treatment available.
Current ERS guidance recommends whole-lung lavage and/or inhaled GM-CSF as first-line treatment for active or worsening autoimmune PAP where symptoms, impaired gas exchange or lung-function impairment justify intervention. (ERS Publications)
For refractory disease, treatment may also include:
- rituximab
- plasmapheresis
- treatment of an underlying disorder in secondary PAP
- and, exceptionally, lung transplantation.
Yet whole-lung lavage remains one of the most remarkable treatments used in respiratory medicine.
Whole-Lung Lavage
Whole-lung lavage is exactly what its name suggests.
One entire lung is repeatedly filled with warmed sterile saline and then drained.
The procedure is conducted under general anaesthesia.
A double-lumen endotracheal tube — DLT — separates the two lungs.
One lung continues to ventilate the patient.
The other is isolated and attached to the lavage system.
International practice varies considerably.
A survey of specialist centres found average lavage aliquots of approximately 800 mL, with total volumes ranging from 5 to 40 litres per lung and an average of about 15 litres. (PubMed Central (PMC))
Royal Brompton specifically describes some patients requiring 30–40 litres before the initially milky lavage fluid becomes almost clear. (Royal Brompton NHS Trust)
Clinical Drowning?
At first sight it appears extraordinary.
The lung of a patient who already has impaired oxygenation is deliberately filled with fluid.
Why does this not simply kill the patient?
The answer lies in the distinction between controlled therapeutic lavage and uncontrolled flooding of the lungs.
PAP does not make saline harmless.
It does not somehow protect the lungs from drowning.
What PAP does is create a lung in which millions of alveoli are already partially occupied by abnormal surfactant-rich material.
Those alveoli are already functioning poorly.
The saline is introduced not because water is beneficial to normal lung tissue, but because it provides a mechanical means of mobilising and removing the material causing the disease.
The procedure is made possible because the two lungs are completely separated.
One lung is deliberately taken out of gas exchange.
The other keeps the patient alive.
What Would Happen in a Healthy Lung?
A healthy lung has no material requiring lavage.
Filling normal functioning alveoli with saline would therefore provide no therapeutic benefit.
Instead it would convert ventilated alveoli into fluid-filled alveoli.
Gas exchange would stop in that lung while pulmonary perfusion continued, producing a substantial right-to-left shunt.
There is an additional danger.
The lung is a delicate pressure-sensitive organ.
If large volumes of fluid were forced rapidly into it, the resulting hydrostatic pressure could damage alveoli and airways.
Published whole-lung lavage literature specifically warns that rapid instillation of large volumes can cause barotrauma, hydropneumothorax, subcutaneous emphysema and pleural fluid collections. (PubMed Central (PMC))
This is why whole-lung lavage is not simply a matter of pouring saline into the chest.
The fluid is delivered under controlled conditions.
In one established technique the saline bags are positioned approximately 50 cm above the mid-axillary line, limiting the hydrostatic pressure applied to the lung. The initial filling is also deliberately slow to minimise bubble formation and pressure injury. (PubMed Central (PMC))
The important distinction is therefore:
PAP makes the lavage therapeutically worthwhile.
Lung isolation makes it anatomically possible.
Controlled filling pressure reduces pulmonary injury.
Single-lung ventilation keeps the patient alive.
Single-Lung Ventilation
Single-lung ventilation is central to whole-lung lavage.
Without it, the procedure cannot safely occur.
Under normal anaesthesia both lungs receive tidal ventilation.
During PAP lavage, one lung is completely isolated from the breathing system.
The ventilator therefore supports the entire patient through the remaining lung.
The opposite lung contains saline.
This produces major physiological consequences.
Right-to-Left Shunt
Pulmonary blood flow does not simply stop because ventilation stops.
Blood continues to pass through the circulation of the non-ventilated lung.
Because that blood cannot participate normally in oxygenation, it returns to the systemic circulation relatively deoxygenated.
This is effectively a right-to-left intrapulmonary shunt.
The body attempts to limit this through hypoxic pulmonary vasoconstriction.
Pulmonary vessels supplying the poorly ventilated lung constrict, diverting some blood towards the ventilated lung.
This improves ventilation-perfusion matching.
An Additional Effect During Lavage
Whole-lung lavage adds another unusual element.
As the treatment lung fills with saline, the increasing pressure within it can compress the pulmonary vascular bed.
Blood flow through the non-ventilated lung may therefore fall.
That can actually reduce the shunt.
As the saline subsequently drains and pulmonary vascular compression decreases, perfusion can return to a lung that remains temporarily unventilated.
The shunt can therefore increase again.
This means oxygenation can change during the different filling and drainage phases.
It is an extraordinary piece of respiratory physiology taking place repeatedly throughout the procedure.
One Diseased Lung Keeping the Patient Alive
There is another critical difference between PAP lavage and routine thoracic surgery.
During many thoracic operations, the anaesthetist can ventilate the better lung while the diseased or operative lung is collapsed.
In PAP:
the ventilated lung also has PAP.
The patient’s entire oxygen uptake and carbon-dioxide elimination may therefore depend upon a single lung that already has impaired gas exchange.
For severely affected patients, this can represent a considerable physiological challenge.
In very advanced disease some patients may not tolerate single-lung ventilation at all.
Extracorporeal support has occasionally been used to permit lavage in profoundly hypoxaemic patients where single-lung ventilation would otherwise be inadequate. (PubMed Central (PMC))
Protecting the Ventilated Lung
The solution cannot simply be to squeeze the patient’s normal two-lung tidal volume into one lung.
Doing so could produce excessive airway pressures and contribute to volutrauma or barotrauma.
Single-lung ventilation therefore requires a lung-protective strategy tailored to the patient.
The anaesthetic team must continually balance:
- oxygenation
- carbon-dioxide elimination
- tidal volume
- airway pressure
- appropriate PEEP
- haemodynamic effects
- and protection of the ventilated lung.
Excessive PEEP is not necessarily beneficial.
Very high pressure in the ventilated lung may redirect pulmonary blood towards the non-ventilated lung and potentially worsen ventilation-perfusion mismatch. (PubMed Central (PMC))
Monitoring During Single-Lung Ventilation
Monitoring commonly includes:
- continuous pulse oximetry
- continuous capnography
- invasive arterial pressure monitoring
- repeated arterial blood gases
- inspired and expired oxygen concentration
- airway pressure
- tidal volume
- pulmonary compliance
- temperature
- fluid balance
- haemodynamic monitoring appropriate to the patient’s condition.
Arterial access is particularly useful because it provides continuous beat-to-beat pressure measurement and readily accessible samples for repeated gas analysis.
The Double-Lumen Endotracheal Tube
The DLT is the piece of equipment that makes whole-lung lavage possible.
It is not simply an unusual endotracheal tube.
It creates two separately controllable respiratory pathways.
A conventional left-sided DLT consists of a tracheal lumen and a bronchial lumen.
The bronchial component extends into the left main bronchus.
A tracheal cuff seals the trachea.
A bronchial cuff isolates the selected bronchus.
The two lungs can therefore be independently ventilated, collapsed or—as in PAP—one ventilated while the other is filled with saline.
During WLL the tube becomes the physical barrier between:
a lung containing oxygen and respiratory gas
and
a lung containing litres of saline.
Its position is therefore fundamental to patient safety.
Loss of Lung Isolation
During routine thoracic surgery, displacement of a DLT can prevent satisfactory lung collapse, obstruct a lobe or compromise ventilation.
During whole-lung lavage, there is an additional risk.
The isolated lung contains saline.
If the DLT moves sufficiently for the bronchial seal to fail, lavage fluid could cross into the ventilated lung.
Published WLL series report lavage-fluid leakage as a recognised complication, together with hypoxaemia and pneumothorax. (PubMed Central (PMC))
This is why correct DLT positioning is not simply confirmed after intubation and forgotten.
Its relationship with the carina matters throughout the entire lavage.
The Mallinckrodt-Type DLT and the Carina Camera
The conventional Mallinckrodt double-lumen tube will be familiar to most practitioners working in thoracic anaesthesia.
Traditionally its position is confirmed using flexible fibreoptic bronchoscopy.
Bronchoscopy remains the reference technique because it allows direct inspection of the carina, bronchial cuff and bronchial anatomy.
However, camera-equipped double-lumen tubes introduced an important development.
The VivaSight-DL follows the familiar left-sided DLT concept but incorporates an integrated camera that allows continuous visualisation of the distal trachea and carina.
This gives the anaesthetic team a continuous view of the relationship between the bronchial cuff and the carina rather than a single snapshot obtained during intermittent bronchoscopy.
Clinical studies have shown that this continuous view allows intraoperative displacement to be recognised immediately. (PubMed)
Why Continuous Carinal Visualisation is Particularly Valuable in PAP
Whole-lung lavage is arguably one of the procedures where continuous visualisation has its clearest theoretical advantages.
The procedure may involve:
- prolonged anaesthesia
- patient repositioning
- repeated lung filling and emptying
- changes in intrathoracic pressure
- manual or mechanical chest percussion
- movement of the mediastinum
- repeated manipulation of tubing and circuits.
Any of these can alter the relationship between the DLT and the airway.
With a conventional tube, the position is checked bronchoscopically at particular points.
The bronchoscope is withdrawn.
The clinician then relies on airway pressures, lung compliance, auscultation, oxygenation and other indirect signs until the position is checked again.
An integrated camera changes this from:
intermittent confirmation
to
continuous surveillance.
The clinician can watch the carina throughout the procedure.
If the bronchial cuff begins migrating proximally, this may be visible immediately.
That is particularly important when a few millimetres of movement could eventually compromise the barrier separating several litres of saline from the patient’s only ventilated lung.
Does the Camera Replace Fibreoptic Bronchoscopy?
No.
This distinction matters.
A carinal camera provides an excellent view of the distal trachea, carina and proximal bronchial cuff.
But it does not provide the complete diagnostic flexibility of a mobile bronchoscope.
Fibreoptic bronchoscopy may still be needed to:
- inspect distal bronchial anatomy
- investigate obstruction
- examine lobar bronchi
- clear secretions
- troubleshoot questionable positioning.
The camera lens itself can also become obscured by secretions or condensation.
The video DLT should therefore be regarded as an additional layer of continuous airway surveillance rather than a reason to remove the fibreoptic bronchoscope from the theatre.
Washing the Lung
Once satisfactory lung separation has been established, the lavage lung is allowed to degas.
Warm sterile saline is then introduced.
The filling pressure must be controlled.
The lung is progressively filled to the desired volume.
Chest percussion may then be performed.
The objective of percussion is not merely physiotherapy.
It helps mobilise the accumulated surfactant and proteinaceous material so that it becomes suspended within the lavage fluid.
The fluid is then drained, generally under gravity.
Initially the effluent may appear strikingly cloudy or milky.
The cycle is repeated.
Fill.
Percuss.
Drain.
Refill.
Percuss.
Drain.
Again and again.
The returning fluid progressively becomes clearer.
Royal Brompton notes that in some patients 30–40 litres may be required before the fluid becomes almost crystal clear. (Royal Brompton NHS Trust)
Fluid In and Fluid Out
Every litre matters.
The volume entering the lung and the volume leaving it must be monitored carefully.
A significant discrepancy raises an obvious question:
Where has the fluid gone?
Some will remain within the treated lung.
A proportion may be absorbed.
But the possibility of leakage must also be considered.
Has the DLT moved?
Has the bronchial cuff seal failed?
Could fluid be entering the ventilated lung?
This makes fluid balance an airway-safety measurement as well as an accounting exercise.
Barotrauma and Hydrostatic Pressure
The lavage lung is not infinitely compliant.
Filling it with fluid generates pressure.
If large volumes are introduced too rapidly or under excessive hydrostatic pressure, pulmonary injury can occur.
Recognised complications include:
- pneumothorax
- hydropneumothorax
- pleural effusion
- subcutaneous emphysema
- hypoxaemia
- fluid leakage into the ventilated lung.
In the international survey of approximately 1,110 lavage procedures, pneumothorax was reported in around 0.8%, fluid leakage in approximately 4%, and hypoxaemia in approximately 14%. (PubMed Central (PMC))
Experienced centres therefore carefully control both the rate and pressure of lavage.
Completing the Procedure
Eventually the lavage fluid becomes sufficiently clear.
Residual saline is drained from the lung.
Ventilation is then restored.
The treated lung must now make an extraordinary transition.
It has gone from:
diseased but gas-filled
to
completely non-ventilated and saline-filled
and then back to
gas-filled and participating in ventilation.
Recruitment may be required.
Compliance, airway pressures, oxygenation and arterial blood gases are reassessed.
The DLT may then be exchanged for a standard single-lumen endotracheal tube.
Royal Brompton describes continuing controlled ventilation for a period after the procedure before allowing the patient to awaken and breathe spontaneously. (Royal Brompton NHS Trust)
The Royal Brompton Experience
Royal Brompton Hospital has accumulated considerable experience in the management of pulmonary alveolar proteinosis.
Its current service information describes whole-lung lavage under general anaesthesia using a double-lumen endobronchial tube, with one lung ventilated while the opposite lung is washed.
Royal Brompton reports more than 300 whole-lung lavage treatments over more than 20 years without a serious complication directly attributable to the lavage treatment in the experience described by the centre. (Royal Brompton NHS Trust)
The hospital identifies PAP and whole-lung lavage as a specialist area within its cardiothoracic anaesthesia service. (Royal Brompton NHS Trust)
The technique I encountered professionally at Royal Brompton was associated with Dr Thomas Pickworth.
From the theatre perspective, the procedure demonstrates how dependent specialist cardiothoracic practice is upon coordinated multidisciplinary working.
The respiratory physician understands the underlying disease.
The anaesthetist controls an exceptionally unusual physiological situation.
The anaesthetic practitioner assists with the DLT, fibreoptic equipment, invasive monitoring and lavage apparatus.
The physiotherapist may provide repeated chest percussion.
The theatre team manages many litres of warmed sterile fluid over a prolonged procedure.
Everyone must understand what is happening and why.
A Treatment That Appears to Break the Rules
Whole-lung lavage appears, superficially, to contradict almost everything we understand about pulmonary care.
A hypoxaemic patient is anaesthetised.
One diseased lung is switched off.
The other diseased lung is expected to support the entire patient.
Then the first lung is deliberately filled with litres of saline.
But the procedure works precisely because it does not ignore respiratory physiology.
It exploits it.
The lungs are separated.
The lavage pressure is controlled.
The non-ventilated lung is temporarily removed from gas exchange.
Pulmonary perfusion redistributes.
The opposite lung maintains ventilation.
The accumulated material is physically mobilised.
The saline is drained.
The lung is recruited.
And millions of alveoli that were previously clogged with surfactant-rich material can once again contribute more effectively to gas exchange.
Clinical Drowning?
The phrase is deliberately provocative.
But it captures something important.
One lung really is deliberately filled with fluid.
Were that to happen accidentally, uncontrollably, to both lungs—or were large volumes forced into a normal lung at excessive pressure—the consequences could be catastrophic.
In PAP, however, controlled lavage turns something that would normally represent pulmonary disaster into treatment.
The disease creates the reason to wash the lung.
The double-lumen tube creates the separation.
The carinal view protects that separation.
Single-lung ventilation maintains life.
Controlled hydrostatic pressure reduces barotrauma.
And the lavage physically removes the disease from the alveolar space.
Few procedures demonstrate the relationship between pathology, equipment, physiology and anaesthetic practice quite as dramatically as whole-lung lavage for pulmonary alveolar proteinosis.
Sometimes, when the lungs can no longer clean themselves, we quite literally have to wash them.
