Breath-by-breath determinations of airway occlusion pressure in the developing lamb.
The ventilatory effects of breath-by-breath measurements of airway occlusion pressure, i.e., airway pressure determined 100 ms after initiation of inspiration (P0.1) were evaluated in seven lambs studied sequentially between 7 and 28 days after birth. P0.1 was determined by computer-aided, on-line regression analysis of the inspiratory pressure versus time (dP/dt) by means of a pneumatic occlusion valve that allowed occlusion times to vary in proportion to respiratory rate. No significant changes were found in minute ventilation, tidal volume, respiratory rate or end-tidal CO2 concentration when the valve was operating as a oneway valve (opening pressure 0.02 kPa or 0.2 cmH2O) compared to when in occlusion mode [opening pressure 0.18-0.2 kPa or 1.8-2.0 cmH2O, mean occlusion time 44 (25) ms]. The calculated P0.1 values correlated well with those obtained from manual occlusions (r = 0.87, P < 0.0001). This new technique, which detects and discards irregular or non-linear (r < 0.95) inspiratory pressure profiles, enables breath-by-breath determinations of inspiratory drive in rapidly breathing lambs with minimal impact on respiratory pattern and ventilation.
Milerad
J
J
Department of Pediatrics, Vanderbilt University Medical School, Nashville, TN 37232-2585, USA.
Larsson
H
H
Lin
J
J
Lindstrom
D P
DP
Sundell
H W
HW
D000375:Aging / Q000502:physiology*; D000399:Air Pressure; D000403:Airway Resistance / Q000502:physiology*; D000465:Algorithms; D000818:Animals; D000831:Animals, Newborn / Q000502:physiology; D003625:Data Collection; D012129:Respiratory Function Tests; D015656:Respiratory Mechanics / Q000502:physiology*; D012756:Sheep; D014132:Trachea / Q000502:physiology