Induced-hypercapnia effects in ventilatory mechanics and work of breathing

摘要

Hypercapnia is defined as an excessive blood CO₂concentration, it is a condition associated to some neuromuscular or respiratory diseases due to negative effects of these illness related to gas exchange. Mechanical ventilation is a strategy to normalize the gas exchange and reduce the work of breathing associated with the respiratory response to eliminate the excess of CO₂in critical patients. Characterize the effect of hypercapnia on ventilatory mechanics and work of breathing could help in the identification of warnings concerning the safe thresholding of work of breathing in mechanical ventilation therapy. A trial where healthy men were exposed to an incremental stimulus of FiCO2 from 0% to 6% in steps of 2% for 5 minutes each. Ventilatory signals and capnogram were recorded to estimate PaCO2 with a noninvasive technique. Ventilatory mechanics was estimated with validated techniques using occlusion maneuvers and optimization algorithms to find compliance, resistance and work of breathing (WOB). Our findings show that compliance did not change with hypercapnic stimuli (p<;0.05), resistance decreased (p<;0.05) and WOB increased from 0.85(0.64-0.94) J/L to 1.22(0.97-1.59) J/L having statistically significant differences (p<;0.05). The obtained values of WOB suggest the control of hypercapnia in patients with muscular commitment or dyspnea, even in values of PaCO2 higher than 42 mmHg.