Breath-to-breath analysis of abdominal and rib cage motion in surfactant-depleted piglets during high-frequency oscillatory ventilation.
OBJECTIVE
To assess the value of monitoring abdominal and rib cage tidal displacement as an indicator of optimal mean airway pressure (Paw) during high-frequency oscillatory ventilation (HFOV).


METHODS
Prospective observational study in a university research laboratory.


METHODS
Eight piglets weighing 12.0+/-0.5 kg, surfactant depleted by lung lavage.


METHODS
Compliance of the respiratory system (C(rs)) was calculated from a quasistatic pressure volume loop. After initiation of HFOV lung volume was recruited by increasing Paw to 40 cmH(2)O. Then mean Paw was decreased in steps until PaO(2)/FIO(2) was below 100 mmHg. Proximal pressure amplitude remained constant.


RESULTS
Abdominal and rib cage tidal displacement was determined using respiratory inductive plethysmography. During HFOV there was maximum in tidal volume (Vt) in seven of eight piglets. At maximal mean Paw abdominal and rib cage displacement were in phase. Phase difference between abdominal and rib cage displacement increased to a maximum of 178+/-28 degrees at minimum mean Paw. A minimum in abdominal displacement and a maximum of Vt was found near the optimal mean Paw, defined as the lowest mean Paw where shunt fraction is below 0.1.


CONCLUSIONS
During HFOV abdominal and rib cage displacement displayed mean Paw dependent asynchrony. Maximal Vt and minimal abdominal displacement coincided with optimal C(rs), oxygenation, and ventilation, suggesting potential clinical relevance of monitoring Vt and abdominal displacement during HFOV.
Markhorst
Dick G
DG
Pediatric ICU, Department of Pediatrics, Vrije Universiteit Medical Centre, Amsterdam, The Netherlands. dg.markhorst@vumc.nl
Jansen
Jos R C
JR
van Vught
Adrianus J
AJ
van Genderingen
Huibert R
HR
D000005:Abdomen / Q000502:physiology; D000818:Animals; D004195:Disease Models, Animal; D006612:High-Frequency Ventilation / Q000379:methods*; D008991:Monitoring, Physiologic; D010991:Plethysmography / Q000379:methods*; D035422:Pleural Cavity / Q000502:physiology; D011663:Pulmonary Surfactants / Q000378:metabolism*; D015656:Respiratory Mechanics / Q000502:physiology*; D012272:Ribs / Q000502:physiology; D034421:Sus scrofa; D013990:Tidal Volume
D011663:Pulmonary Surfactants