Transmural pressure at any level in the upper airway is dependent on the difference between intraluminal airway and extraluminal tissue pressure (ETP). We have previously shown in rabbits that ETP is positive, fluctuates with respiration and is increased by neck flexion. This study examines the influence of resistive loading on ETP. Methods: Five supine, anaesthetised (ketamine/xylazine), spontaneously breathing, mouth closed, New Zealand White rabbits breathed via a mask with an attached pneumotachograph to measure nasal airflow (Vn), and a pressure transducer to record mask pressure (Pm). ETP was measured directly with a pressure transducer tipped catheter (MPC 500, Millar) surgically positioned in the tissues of the lateral pharyngeal wall. Studies were performed with (Resistance) and without (Control) an external resistor and with head/neck position at 30, referenced to the horizontal. Results: The addition of an external resistive load increased inspiratory resistance at peak inspiratory Vn from 3.4±0.4 cm H20;l/s to 5.9=0.9 cm H20/L/s (group mean±SEM: p=0.01. paired t-test). ETP was positive in all rabbits and varied with respiration by 1.06±0.30 cm HiO during Control, a value which was unchanged with Resistance (1.07±0.30 cm H,0, p=0.2). Maximum and minimum ETP were 8.0±1.8 cm H-,0 and 6.9±1.8 cm H20. respectively, during Control, and were not significantly different with Resistance (7.8±1.9 cm H20 and 6.7±l.9 cm H,0. respectively: both p=0.4). Conclusion: We conclude that small increases in upper airway resistance do not significantly influence upper aim-ay ETP in anaesthetised rabbits. Thus, for a constant head'neck position, intraluminal pressures determine UA transmural pressures associated with UA resistive loading, although the influence of larger resistive loads on ETP still requires further investigation.
|Original language||English (US)|
|Issue number||SUPPL. 1|
|State||Published - 2001|
- External resistance
- Upper airway extraluminal tissue pressure
ASJC Scopus subject areas
- Pulmonary and Respiratory Medicine