pulmonary edema

The lungs are built like a fine sponge whose air pockets must stay dry to absorb oxygen. Pulmonary edema is when those air pockets flood with fluid — like a sponge so soaked that air can no longer reach the surface. The person feels they are drowning from the inside and fights for every breath.

In its cardiac form, the cause is high pressure in the left heart. When the left ventricle or left atrium cannot keep up, pressure climbs in the pulmonary veins and capillaries until it overcomes the forces that normally hold fluid inside the vessels, and watery plasma is squeezed out into the alveoli. This impairs gas exchange, producing severe breathlessness, a suffocating sensation, rapid breathing, and sometimes pink, frothy sputum.

Acute cardiogenic pulmonary edema is a medical emergency. Standard measures include sitting the patient upright, giving oxygen, intravenous diuretics to remove fluid, and nitrates to lower pressures; non-invasive ventilation often helps. Not all pulmonary edema is cardiac — it can also arise from lung injury, very low blood protein, or altitude, so the cause must be identified.