Hypodynamisk respirationsinsufficiens. Diagnostisk udredning

Patients with restrictive lung disease, owing to respiratory muscle dysfunction, have no parenchymal involvement. Their vital capacity (VC) and total lung capacity (TLC) are reduced to less than 50% and can lead to pneumonia and nocturnal hypercapnia and hypoxia. Their diffusion capacity is normal. With maximal static mouth pressure (Pimax) < 80 cm H2O and/or Pemax < 100 cm H2O, patients are referred to the national centres. Here, inspiratory muscular insufficiency is confirmed by sniff nasal inspiratory pressure and oesophageal pressure < 70 cm H2O. Expiratory muscular insufficiency is confirmed by a cough peak flow < 3-4 L/sec. and cough gastric pressure < 100 cm H2O. Sleep studies reveal nocturnal hypoventilation. Phrenic nerve stimulation is to be introduced in the diagnostic approach. Twitch mouth or oesophageal pressure < 10 cm H2O and twitch gastric pressure < 7 cm H2O are pathognomonic for neuromuscular respiratory insufficiency.