Investigating the Use of Resistance Breathing for the Detection of Acute Hypovolemia

Introduction: Standard vital signs (e.g., heart rate and blood pressure) lack sensitivity and specificity to detect blood volume status following hemorrhage. Inspiratory resistance breathing has therapeutic potential to increase blood pressure and cardiac output following blood loss. We hypothesize that resistance breathing will elicit greater increases in absolute and breath-to-breath amplitude of stroke volume and arterial pressure under hypovolemic vs. normovolemic conditions. Methods: Data were retrospectively analyzed from 23 healthy human subjects aged 18-45 years. Subjects underwent lower body negative pressure (LBNP) protocols to simulate hemorrhage with and without resistance breathing. Continuous mean arterial pressure (MAP) and stroke volume were measured via finger photoplethysmography. Comparisons of absolute and changes in the breath-to-breath amplitude of MAP and stroke volume were made under 4 conditions: 1) normovolemia; 2) normovolemia + resistance breathing; 3) hypovolemia, and; 4) hypovolemia + resistance breathing. Results: Preliminary findings show an average change in MAP of -3.1% in response to resistance breathing during normovolemia, and +8.2% during hypovolemia. MAP amplitude during normovolemia decreased by -1.5% and increased by 22.4% during hypovolemia. Stroke volume maximum increased by 3.8% during normovolemia and 20.0% during hypovolemia, while stroke volume amplitude during normovolemia increased by 52.4% % and 19.0% during hypovolemia. Conclusions: These data indicate that there may be differences in the hemodynamic response to resistance breathing that could aid in the diagnosis of acute hypovolemia.