Anesthesia & Clinical Research
Open Access

Abstract

Hemodynamic Response to Dynamic Changes in Upper Airway Impedance–A Volunteer Study

Ottokar Stundner, Thomas Danninger, Isabelle Kao, Peter Gerner and Stavros G Memtsoudis

Introduction: Intermittent airway obstruction may occurring both intubated and non-intubated critically ill patients due to endotracheal tube obstruction or kinking in the former and loss of oropharyngeal tone particularly during sedation in the latter patient group. Spontaneous breathing efforts against high airway resistance invoke shifts in intrathoracic pressure, which could potentially negatively affect cardiac performance. Previous studies utilized the Mueller Maneuver as a model for pathophysiologic changes during these episodes. However, this model only accounts for the state of maximum inspiration. To study progressive airway obstruction of various degrees, we devised an experimental setup allowing for a dynamic simulation and identification of associated short-term effects of breathing against discretely increasing airway resistance. Material and methods: 14 healthy volunteers (9 female, 5 male; mean age 27.8 ± 4.1 years, mean body mass index 26.1 ± 3.6 kg/m2) were asked to breathe through a set of endotracheal tubeswith decreasing internal diameter, while cardiovascular and hemodynamic parameters were recorded.StrokeVolume (SV) and Cardiac Index (CI) were recorded using thoracic bioreactance. Heart Rate (HR), non-invasive arterial blood pressure, oxygen saturation and spirometry parameters were also recorded. Results: Baseline SV, HR and CI averaged 99.8 ml, 69.5/min and 4.01 l/min/m2. During respiration through tubes with decreasing diameters, SV, HR and CI decreased significantly. At maximum airway resistance, SV, HR and CI averaged 90.7 ml, 65.0/min and 3.38 l/min/m2, representing mean percent changes from baseline of -9.1% (p=0.0041), -6.5% (p<0.0001) and -15.7% (p<0.0001). Strong inverse Pearson correlations were detectible between calculated additional airway resistance (Hagen-Poiseuille) and SV (R=-0.143, p=0.013), and CI (R=-0.147, p=0.011), respectively. Blood pressure, arterial oxygen saturation and spirometry parameters did not differ significantly. Conclusions: Increases in airway resistance were dynamically associated with significant hemodynamic deterioration. Ensuring the maintenance of airway patency is therefore an important factor to consider in hemodynamically unstable patients.