If not removed from the system, it may be reinhaled, causing an increase in the inhaled concentration.Under hyperbaric conditions, hypercapnia contributes to nitrogen narcosis and oxygen toxicity by causing cerebral vasodilation which increases the dosage of oxygen to the brain. Mechanism
Hypercapnia normally triggers a reflex which increases breathing and access to oxygen (O2), such as arousal and turning the head during sleep. A failure of this reflex can be fatal, for example as a contributory factor in sudden infant death syndrome.Hypercapnia can induce increased cardiac output, an elevation in arterial blood pressure (higher levels of carbon dioxide stimulate aortic and carotid chemoreceptors with afferents -CN IX and X- to medulla oblongata with following chrono- and ino-tropic effects), and a propensity toward cardiac arrhythmias. Hypercapnia may increase pulmonary capillary resistance.
A standard chemotherapy two-drug regimen (epirubicin plus ifosfamide) may be used in these cases. In place or combined with surgery and/or radiotherapy, severe and/or metastatic cases of UPS are commonly treated with epirubicin plus ifosfamide; doxorubicin alone or combined with ifosfamide, olaratumab, trabectedin, gemcitabine, or docetaxel;  cyclophosphamide, vincristine, doxorubicin, plus dacarbazine or cisplatin; cyclophosphamide, doxorubicin, plus dacarbazine; high dose methotrexate; or etoposide, ifosfamide, and cisplatin. These treatment regimens have been reported to lower local recurrence rates, prolong disease-free survival rates (i.e. time after treatment when no disease is detected), and increase overall survival rates (i.e. time after treatment to death from any cause). However, other studies report that the addition of radiotherapy and/or chemotherapy to surgical resection does not improve recurrence or overall survival rates; addition of radiotherapy to surgery improves local control of UPS tumors but not disease-free survival rates (i.e. time from treatment to recurrence of disease); and adjuvant chemotherapy and radiotherapy have no significant effects on local recurrence-free survival rates, metastasis-free survival times, and overall survival rates. Further studies are needed to define the best treatments for UPS tumors.In a retrospective study of 176 patients with localized UPS undergoing curative-intent treated with surgical resection or resection plus adjuvant treatment, disease-free survival rates at 120 months for patients with tumors in an extremity (leg or arm), heat/neck area, thorax, and abdomen/pelvis were about 70, 60, 50, and 0%, respectively; overall survival rates at 150 months for disease at these sites were about 90, 80, 75, and 35%, respectively.