Impedance cardiography as a tool for haemodynamic monitoring at high altitude: a preliminary study.

BACKGROUND Altitude illness is a relevant threat to the life and health of participants in mountaineering expeditions. AIM To determine if impedance cardiography (ICG) can be used in noninvasive monitoring of haemodynamic disturbances at high altitude. METHODS The study was performed in a group of 13 participants of two mountaineering expeditions in the Himalayas. The ICG examination was performed before the expedition and again at high altitude (4,300-5,700 m) with concurrent estimates of clinical symptoms of acute mountain sickness (AMS) and those suggesting an increased risk of high altitude pulmonary oedema (HAPO). RESULTS High altitude influenced the haemodynamic profile of the subjects. Significant changes were observed for: stroke index (baseline vs. high altitude: 51.2 ± 10.3 vs. 35.5 ± 11.3 mL/m(2); p = 0.0007), cardiac index (3.24 ± 0.49 vs. 2.63 ± 0.66 L/min/m(2); p = 0.013), Heather index (16.6 ± 4.3 vs. 12.8 ± 4.45 Ohm/s(2); p = 0.006), heart rate (64.1 ± 11.7 vs. 75.4 ± 15.4 1/min; p = 0.045) and systemic vascular resistance index (2,051.3 ± 438.9 vs. 2,668.4 ± 856.2 dyn × s × cm(-5) × m(2); p = 0.027). AMS was observed in six subjects (mild: n = 5, severe: n = 1). Three of them revealed symptoms suggesting an increased risk of HAPO and this subgroup (vs. subgroup without such symptoms) was characterised by higher thoracic fluid content index (baseline: 19.2 ± 0.9 vs. 17.9 ± 2.0 1/kOhm x m(2); p = 0.176, at high altitude: 20.8 ± 1.4 vs. 17.7 ± 1.6 1/kOhm x m(2); p = 0.018) and lower Heather index (baseline: 11.4 ± 2.0 vs. 18.2 ± 3.5 Ohm/s(2); p = 0.028, at high altitude: 9.2 ± 2.1 vs. 13.9 ± 4.4 Ohm/s2; p = 0.028). CONCLUSIONS ICG may be a helpful, noninvasive tool in monitoring cardiovascular dysfunction occurring at high altitude, especially with breathing disorders.