2/20/2024 0 Comments Dead space vs shunt usmle“Micro” level dead space – scarred alveoli due to ARDS become inefficient at CO2 clearance.Excess dead space can arise at a “micro” level or a “macro” level: Dead space is essentially wasted breath – the body moves gas in and out of the chest, but it achieves no CO2 clearance. Thus, any patient who is desaturating despite high concentrations of inhaled oxygen likely has a shunt.ĬO2 clearance depends on the amount of gas entering and leaving the lungs every minute, which removes CO2 from the body.Ī key variable here is dead space – which is gas that is inhaled and exhaled but which does not participate in CO2 clearance. A hallmark of shunt physiology is that it is poorly responsive to increased levels of oxygen (because blood isn’t coming anywhere close to ventilated alveoli). Examples include an anatomic abnormality (e.g., ventricular septal defect) or complete dysfunction of parts of the lung (e.g., mucus plugging of one lobe of the lung).
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