4 就胸壁而言,橫跨壁壓(transmural pressure)等於:(A)肺泡內壓(intrapulmonary pressure)-胸膜腔內壓(intrapleural pressure)(B)胸膜腔內壓-大氣壓(barometric pressure)(C)肺泡內壓-大氣壓(D)胸膜腔內壓+大氣壓