[Acute hemodynamic effects of upper airway obstruction in normal dogs]

Eight normal dogs were anesthetized to assess the effects of an upper airway obstruction (UAO) on arterial blood gases (ABG) and hemodynamic (HD) parameters. Each dog was fitted with an arterial line, a Swan-Ganz catheter and an endotracheal tube. The HD parameters including heart rate, systolic blood pressure, central venous pressure (CVP), cardiac index (CI), pulmonary capillary wedge pressure (PCWP), systemic vascular resistance index (SVRI), pulmonary vascular resistance index (PVRI), left ventricle stroke work index (LVSWI) and right ventricle stroke work index (RVSWI), were monitored. The baseline ABG and HD parameters were taken prior to endotracheal tube clamping, and then checked at 0.3, 1.5, 3.0, 4.0 and 5.0 minutes. The clamp was subsequently removed to allow spontaneous breathing, and then another set of measurements were taken at 5, 15 and 30 minutes, respectively. The above procedures were then repeated a second time. The results showed that UAO can produce the following: (1) decreases in the CI, PaO2 and pH; (2) increases in the mean systemic and pulmonary arterial pressure, PCWP, SVRI, PVRI, LVSWI, RVSWI, and PaCO2; (3) significant and acute changes in PaO2 and pH, with the most significant changes occurring within 90 seconds after clamping and then reaching a plateau; and (4) repeated UAO increases in SVRI and PVRI. In conclusion, upper airway obstructions may possibly induce serious ABG and HD changes in humans, as it does in normal dogs.