Читать книгу Emergency Medical Services - Группа авторов - Страница 186

The patient in shock may require assisted ventilation. Venous return requires a relative negative pressure in the right atrium to ensure return of blood to the heart. Assisted ventilation using any of the typical techniques, such as bag‐valve‐mask ventilation, endotracheal intubation, or supraglottic devices, results in an increase in airway pressure, raising intrathoracic pressure. Patients in shock from any cause are extremely sensitive to increases in intrathoracic pressure. Studies in a swine hemorrhagic shock model showed that even modest increases in the rate of positive‐pressure ventilation significantly reduce brain blood flow and oxygenation [64]. EMS personnel must carefully control the rate of assisted positive‐pressure ventilation in the shock patient, as overventilation is common. Generally, a one‐handed squeeze on the ventilation bag at a rate of approximately once every 8 seconds is reasonable for an adult, producing a minute ventilation of about 5 L/min. Minute ventilation should be adjusted to ensure an EtCO₂ between 35 cmH₂O and 45 cmH₂O.