Note that with neck flexion, the ETT moves on average 3.8 cm in the adult (but can move as much as 6.4 cm)
Anatomy relevant to the placement of a DLT: R mainstem is 2.5 cm in length. In 10% of adults, RUL departs in < 2.5 cm, and in 2-3% of adults, the RUL opens directly into the trachea.
Carotid and aortic bodies (peripheral chemoreceptors) respond to PaO2 values of ~ 60-65 mm Hg. Their response is unreliable during general anesthesia.
Dead space primarily affects CO2 elimination, whereas shunting primarily affects arterial oxygenation. While alveolar: dead space in the spontaneously ventilating patient is 2:1, in the mechanically-ventilated patient it is 1:1 (? circuit dead space + ? changes in west zones).
Many COPD patients have decreased pulmonary vascular compliance, thus while they may not have pulmonary hypertension at their baseline state, PVR may rise rapidly when cardiac output increases; this can be exacerbated by acidosis, hypoxia, PEEP, and infection, all of which can ultimately lead to right heart failure.