Cardiogenic versus non-cardiogenic pulmonary oedema

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

Fluid enters alveoli when filtration exceeds lymphatic clearance. In cardiogenic oedema, elevated left atrial pressure drives hydrostatic transudation, often from acute coronary syndrome, arrhythmia, hypertensive decompensation, valve failure or fluid overload. In permeability oedema, endothelial and epithelial injury produces protein-rich fluid and reduced compliance despite no primary rise in left-sided filling pressure.

The distinction is probabilistic rather than binary. Sepsis can depress the myocardium; renal failure can cause both volume overload and inflammatory injury; aspiration can precipitate ARDS in a patient with chronic heart failure. Treatment should therefore follow current physiology: congestion, perfusion, oxygenation, work of breathing and the precipitating cause.

Bedside response can refine diagnosis but is not a substitute for assessment. Improvement after diuresis supports congestion but can occur in mixed disease, while a transient response to positive pressure benefits both mechanisms. Apply current NICE acute-heart-failure, BTS oxygen, ICS ARDS and local critical-care pathways.

Key points

Cardiogenic oedema results mainly from raised pulmonary capillary hydrostatic pressure; non-cardiogenic oedema reflects increased alveolar–capillary permeability, as in ARDS.
Orthopnoea, raised JVP, peripheral oedema, ischaemia, hypertension, new murmur or known ventricular disease support cardiogenic physiology, but overlap is common.
Sepsis, aspiration, pancreatitis, transfusion, trauma or inhalational injury with bilateral opacities and no dominant left-heart failure suggests non-cardiogenic injury.
Chest radiography can show bat-wing shadowing, septal lines, cardiomegaly or effusions in cardiogenic oedema; ARDS more often has diffuse opacities without cardiomegaly, but no sign is definitive.
Lung ultrasound confirms interstitial fluid through B-lines but cannot alone establish its cause. Add focused cardiac ultrasound, IVC context and the clinical story.
Natriuretic peptides support heart-failure assessment but rise with age, renal dysfunction, right-heart strain and critical illness; low values are more useful for reducing likelihood than high values are for proving cause.
Give intravenous loop diuretic promptly in acute heart failure with congestion and monitor renal function, weight and urine output. Do not use diuresis reflexively in permeability oedema with shock.
NICE advises against routine nitrates, opiates or non-invasive ventilation for every acute-heart-failure patient. Use NIV for severe dyspnoea with acidaemia or failure of initial treatment, and nitrates only in selected circumstances.
Non-cardiogenic oedema management centres on source control, lung-protective support and a conservative fluid strategy after shock has resolved.
Repeated reassessment matters because mixed cardiogenic and inflammatory oedema is common, especially in older people with sepsis and cardiac disease.

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

Raised left-heart pressure

Acute ventricular failure, ischaemia, arrhythmia, hypertension or valve disease raises pulmonary venous and capillary hydrostatic pressure, driving cardiogenic oedema.

Increased alveolar permeability

Sepsis, pneumonia, aspiration, trauma and pancreatitis damage the alveolar-capillary barrier and produce non-cardiogenic protein-rich oedema, with host defence and baseline lung health modifying its clinical effect.

Fluid and renal factors

Excess intravenous fluid, renal failure and salt retention increase intravascular volume and can aggravate hydrostatic oedema in a vulnerable heart.

Mixed mechanisms

Critical illness commonly combines cardiac dysfunction, fluid overload and inflammatory permeability injury, so a binary label may oversimplify the physiology.

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

1
Interstitial fluid accumulation
Hydrostatic pressure or barrier injury moves fluid from capillaries into the pulmonary interstitium faster than lymphatics can clear it.
2
Alveolar flooding
As capacity is exceeded, fluid fills alveoli, reduces surfactant function and causes collapse of dependent gas-exchange units.
3
Shunt physiology
Blood continues to perfuse poorly ventilated fluid-filled lung, producing hypoxaemia that may be severe and poorly responsive to oxygen alone.
4
Reduced compliance
Wet, collapsed lung becomes stiff, increasing work of breathing and precipitating ventilatory fatigue in susceptible patients.

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

Cardiogenic pulmonary oedemaRed flag

Acute orthopnoea, widespread crackles, raised JVP, oedema, cool or hypertensive physiology, cardiomegaly, effusions and a compatible cardiac trigger make hydrostatic oedema likely.

Flash pulmonary oedemaRed flag

Abrupt severe distress with hypertension may follow acute ischaemia, rapid arrhythmia, renal-artery disease or acute mitral/aortic valve dysfunction; little peripheral oedema may be present.

Non-cardiogenic permeability oedemaRed flag

A recognised inflammatory insult, bilateral opacities, hypoxaemia disproportionate to congestion and no dominant left-heart failure suggests ARDS or another permeability process.

Mixed oedemaRed flag

Sepsis, renal disease, transfusion or major surgery can combine ventricular dysfunction, fluid loading and inflammatory capillary leak; discordant findings should prompt a mixed model rather than forced categorisation.

Cardiogenic shockRed flag

Hypotension, cool peripheries, confusion, oliguria and elevated lactate with pulmonary congestion indicate low output; standard diuretic or vasodilator treatment alone may worsen perfusion.

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
ABCDE assessment, pulse oximetry and arterial blood gasFirst step
Why
Quantify immediate respiratory and circulatory failure and identify hypercapnia, acidosis or lactate elevation.
Interpretation and limitations
Hypercapnia with exhaustion, worsening acidaemia or altered consciousness signals ventilatory failure. Record oxygen device and concentration with every gas.
02
ECG and serial high-sensitivity troponin
Why
Identify acute coronary syndrome, ischaemia or arrhythmia as a trigger.
Interpretation and limitations
Troponin can rise from critical illness or wall stress; diagnose myocardial infarction from symptoms, ECG and dynamic change rather than one elevation.
03
Chest radiograph
Why
Assess oedema pattern, heart size, pleural fluid and mimics such as focal infection or pneumothorax.
Interpretation and limitations
Cardiomegaly, upper-lobe diversion, septal lines and effusions favour cardiogenic disease, but portable films and early disease limit specificity.
04
Lung and focused cardiac ultrasound
Why
Confirm diffuse interstitial fluid, evaluate ventricular function, valves, pericardium and venous congestion.
Interpretation and limitations
B-lines indicate lung water, not its cause. Focal sparing, consolidation, right-heart strain or severe valve disease changes the differential and urgency.
05
BNP or NT-proBNP
Why
Support or reduce the likelihood of acute heart failure when diagnosis remains uncertain.
Interpretation and limitations
Interpret against age, renal function, obesity, atrial fibrillation and right-heart strain. A high result is not specific for cardiogenic oedema.
06
FBC, renal profile, liver tests, CRP, cultures and lactate
Why
Find anaemia, renal fluid retention, infection, organ congestion and shock.
Interpretation and limitations
Use cultures before antibiotics when this causes no delay, and trend renal function and electrolytes during diuresis or critical illness.
07
Formal echocardiography
Why
Define systolic and diastolic function, filling-pressure surrogates, valve lesions and mechanical complications.
Interpretation and limitations
Urgent expert imaging is needed for suspected acute severe regurgitation, ventricular septal defect or tamponade; a preserved ejection fraction does not exclude cardiogenic oedema.

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

Multifocal pneumonia

Fever, purulent sputum, focal or patchy consolidation and microbiology support infection, though pneumonia can also trigger cardiac failure or ARDS.

Diffuse alveolar haemorrhage

Falling haemoglobin, haemoptysis, autoimmune or renal features and bloody lavage suggest alveolar bleeding rather than oedema.

Pulmonary embolism

Acute dyspnoea, hypoxaemia and right-heart strain with thromboembolic risk may mimic oedema, while imaging clarifies pulmonary arterial obstruction.

Acute exacerbation of ILD

Underlying fibrosis with new bilateral ground-glass change and no convincing hydrostatic explanation points towards acute inflammatory deterioration.

Fluid overload without pulmonary oedema

Peripheral oedema or positive fluid balance alone does not prove alveolar flooding; lung findings and gas exchange establish respiratory involvement.

Additional chapter-specific clues

Important mimicRed flag

Bilateral pneumonia, diffuse alveolar haemorrhage, lymphangitic cancer, acute eosinophilic pneumonia and severe interstitial-lung-disease exacerbation can resemble oedema radiographically.

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

01First minutesStabilise before classifyingFirst stepAcute respiratory distress with bilateral crackles or pulmonary opacities.

1Sit upright if tolerated, attach monitoring, obtain IV access, prescribe oxygen to target and call senior help while assessing airway, breathing and circulation.
2Use CPAP or NIV when severe dyspnoea with acidaemia persists or initial treatment fails, with immediate intubation planning if consciousness, shock or work of breathing worsens.
3Obtain ECG, portable chest radiograph, blood gas, renal profile, troponin and focused ultrasound without delaying treatment.
4Identify a trigger: ACS, arrhythmia, hypertensive emergency, valve catastrophe, infection, aspiration, transfusion, renal failure or toxin.

02CardiogenicRelieve congestion and correct the triggerClinical, ultrasound and cardiac findings favour raised hydrostatic pressure.

1Give intravenous loop diuretic using prior exposure, renal function and local acute-heart-failure protocol; measure urine output and early response.
2Treat ACS, rapid arrhythmia or hypertensive emergency through the relevant pathway; consider nitrates only with adequate blood pressure and a specific indication.
3Request early specialist echocardiography for new murmur, shock, prosthetic valve concern or suspected mechanical complication.
4EscalationIf diuretic resistance or shock develops, involve heart-failure and critical-care teams rather than repeatedly escalating treatment without haemodynamic review.

03Non-cardiogenicTreat permeability injuryA precipitating inflammatory insult and assessment do not show dominant left-heart congestion.

1Treat the cause promptly, including sepsis source control, aspiration care, transfusion reaction management or toxin advice.
2EscalationEscalate oxygen support with close monitoring; use lung-protective invasive ventilation and early prone-position assessment when ARDS severity requires it.
3Resuscitate shock with repeated reassessment, then avoid ongoing positive fluid balance once perfusion is restored.
4Reassess for cardiac overlap because myocardial dysfunction and renal failure commonly coexist.

04Uncertain or mixedUse serial physiologyHistory, imaging, biomarkers and examination point in different directions.

1State the competing mechanisms explicitly and treat immediate hypoxaemia, shock and reversible triggers.
2Use serial focused ultrasound, fluid balance, renal function, gas exchange and response to cautious therapy rather than one biomarker.
3Obtain formal echocardiography and critical-care or cardiology review when haemodynamics remain unclear.
4Stop ineffective or harmful treatment promptly: avoid continuing fluids into congestion or aggressive diuresis into low preload.

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

Reduces venous and pulmonary hydrostatic congestion in cardiogenic oedema.

Intravenous loop diuretic

Start promptly for acute heart failure with congestion, selecting dose from prior diuretic exposure, renal function and the current local protocol.

Monitor urine output, weight, creatinine, sodium, potassium and blood pressure. Do not assume oliguria means more diuretic when shock or intravascular depletion is present.

Reduces preload and afterload rapidly in selected cardiogenic pulmonary oedema.

Intravenous nitrate for selected patients

Use a titrated monitored infusion only for a defined indication such as severe hypertension, ischaemia or acute regurgitation and adequate blood pressure.

NICE does not recommend routine nitrate use. Avoid with hypotension, right-ventricular infarction, severe aortic stenosis or recent PDE5 inhibitor exposure.

Treats infection driving permeability oedema, sepsis-related myocardial dysfunction or mixed respiratory failure.

Antimicrobial therapy when infection is causal

Give promptly according to the current local sepsis or pneumonia guideline, cultures, allergy, renal function and likely source.

Do not give antibiotics solely because chest opacities are bilateral. Review microbiology, narrow when possible and provide source control.

Corrects hypoxaemia while definitive haemodynamic and ventilatory treatment proceeds.

Controlled oxygen

Titrate to the BTS target saturation for the patient; use a lower target if hypercapnic respiratory failure is a recognised risk.

Oxygen is not treatment for congestion and does not replace ventilatory support. Record the device and repeat blood gases when CO2 retention or exhaustion is possible.

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

Acute respiratory failure

Widespread shunt and low compliance cause severe hypoxaemia and exhausting work of breathing, sometimes requiring positive-pressure or invasive support.

Cardiogenic shock

When myocardial dysfunction drives oedema, falling cardiac output may cause hypotension, coronary hypoperfusion and multi-organ injury.

Ventilator-related harm

High pressures used against stiff lung can cause overdistension, haemodynamic compromise and air leak if support is not carefully titrated.

Renal injury

Shock, venous congestion and competing fluid or diuretic needs can worsen kidney function and make volume management more difficult.

Recurrent decompensation

Uncorrected cardiac, renal or inflammatory drivers predispose to repeated pulmonary oedema and progressive loss of functional reserve.

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

Continuously monitor respiratory rate, work of breathing, saturation, oxygen device, blood pressure, rhythm, consciousness and peripheral perfusion.
Use urine output, weight, net fluid balance, JVP, oedema and serial lung ultrasound to judge decongestion rather than creatinine alone.
Repeat blood gas promptly after ventilatory intervention or deterioration; trend lactate only with perfusion and clinical trajectory.
During diuresis or vasoactive treatment, monitor creatinine, sodium, potassium and magnesium at a frequency matched to instability.
Reassess the diagnosis if oxygenation, congestion or haemodynamics do not respond as predicted, and seek formal echocardiography.
After recovery, identify the precipitant, optimise chronic heart-failure or respiratory care and provide a clear action and follow-up plan.

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

B-lines are not a diagnosis

They show interstitial fluid or thickened interlobular structures and occur in heart failure, ARDS, fibrosis and infection. Distribution and cardiac findings provide mechanism.

Preserved ejection fraction can flood lungs

Acute diastolic dysfunction, tachyarrhythmia or severe hypertension can raise left-atrial pressure despite a normal-looking ejection fraction.

Creatinine may rise during useful decongestion

Interpret a modest change alongside congestion, perfusion and urine output; stopping effective treatment reflexively may leave harmful venous congestion untreated.

Positive pressure helps both mechanisms

CPAP reduces work of breathing and left-ventricular afterload in cardiogenic disease, while PEEP recruits alveoli in permeability oedema; response does not prove cause.

Mixed oedema is common

An older patient with sepsis can have capillary leak, septic cardiomyopathy, renal salt retention and chronic HFpEF simultaneously. Serial physiology is safer than a forced binary label.

11Common pitfallsFrequent interpretation and management errors.

01
Diagnosing cardiogenic oedema from B-lines alone.
02
Giving nitrates, opiates or NIV routinely without a physiological indication.
03
Using a raised natriuretic peptide as proof of left-heart failure in renal or critical illness.
04
Aggressively diuresing permeability oedema while shock remains under-resuscitated.
05
Giving repeated fluid boluses to a patient with obvious venous and pulmonary congestion.
06
Missing acute valve failure or post-infarct mechanical complication because no previous heart failure is known.
07
Assuming one mechanism when infection and cardiac failure clearly coexist.