Exercise tolerance of patients under nasal intermittent positive pressure ventilation (nIPPV)

Background: There are only a few papers concerning with exercise tolerance of patients under nasal intermittent positive pressure ventilation (nIPPV). Patients and Method: Therefore since 1996 we routinely checked exercise tolerance of our nIPPV-patients when admitted to the hospital. Till March 1997 we had carried out 138 6-minute walking tests (6-min WT) in 111 patients. Questions: Is there an improvement of exercise tolerance in the course of nIPPV-therapy? Are hypoxemia or hypercapnia occurring during exercise-test? Methods: The 6-min WT was performed after one practice walk. The patients got oxygen in case of a preexisting oxygen therapy or in case of an oxygen saturation below 85% before starting. Blood gas analyses were carried out before and after stopping the test. Oxygen saturation and heart rate were registered continuously. The distance walked was measured. Twenty-one patients were tested before introducing nIPPV therapy and 3 months after home mechanical ventilation (HMV). Results: The average distance walked amounted only 283 +/- 82 m (norm in healthy persons: 800 m). pCO(2) decreased from 69 +/- 11 to 58 +/- 12 mm Hg, pCO(2) measured from 47 +/- 8 mm Hg. Oxygen saturation (SaO(2)) fell from 92 +/- 5 to 80 +/- 10%, heart rate increased from 104 +/- 18 to 130 +/- 23 beats/min. The distance walked changed not significantly from 282 +/- 109 to 308 +/- 71 m. Six patients could be tested a 3rd time after 6 months HMV. The distance walked was 315 +/- 103 m (also no significant difference). Conclusions: Everyday activity can cause severe hypoxemia in nIPPV patients. Ambulatory oxygen therapy should be considered in each case. A significant improvement of exercise tolerance under nIPPV therapy is not yet proven. Our data only show a tendency towards an increase.