The Science Journal of the American Association for Respiratory Care

2004 OPEN FORUM Abstracts

TIDAL VOLUME DELIVERY DURING NASAL SIMV IN NEONATES

Kathleen Deakins RRT-NPS, Robert L. Chatburn RRT-NPS FAARC Rainbow Babies & Children’s Hospital, Cleveland, OH

Introduction: Noninvasive ventilation of neonates using pressure controlled SIMV through nasal prongs has been shown to improve outcomes compared to nasal CPAP alone. (Nasal intermittent positive pressure ventilation versus nasal continuous positive airway pressure for preterm neonates after extubation: The Cochrane Library, Issue 3, 2004) However, no studies have provided data regarding potential tidal volume delivery. The purpose of this bench evaluation was to determine the effects of ventilating pressure, inspiratory time and cannula type on volume delivery.

Methods:
A simple volume displacement test was performed using four nasal CPAP delivery devices. A capped, inverted 30 mL syringe, (plunger removed) was filled with water, supported by a double burette clamp and one end immersed in water. A 3.0mm endotracheal tube adapter was attached to an infant nasal cannula (Salter Laboratories). The cannula was then connected to an Infrasonics Infant Star ventilator. The prongs of the cannula were placed under water inside the syringe. The ventilator was set to cycle at a frequency of 15/min, peak pressures 5 and 10 cm H20 and inspiratory times 0.3 and 0.5 seconds at flows of 8 L/min (PEEP = 0). The volume of water displaced over five consecutive breaths was recorded. The procedure was repeated using small nasal CPAP prongs (Medicomp.) and (Fisher & Paykel), and 2.5 mm O.D.7.5 French Binasal airway (Neotech).

Results:
Experimental data are shown in the table below.

  TI P Volume (mL)
Device (seconds) (cm H2O) mean SD
cannula (Salter) 0.3 5 0.3 0.10
  0.5 5 0.4 0.06
  0.3 10 1.0 0.00
  0.5 10 2.5 0.06
prongs (Medicomp) 0.3 5 8.3 1.53
  0.5 5 11.0 1.00
  0.3 10 14.3 0.58
  0.5 10 22.7 1.15
prongs (Fisher) 0.3 5 10.0 0.00
  0.5 5 13.7 1.53
  0.3 10 14.7 2.52
  0.5 10 25.3 1.53
nasopharyngeal 0.3 5 4.0 0.00
prongs (Neotech) 0.5 5 9.7 1.15
  0.3 10 10.3 1.53
  0.5 10 10.8 1.44

Conclusion: As expected, volume delivery through the fixed resistance of the prongs and cannula was proportional to inspiratory time for all delivery devices. Volume delivery was greatest with the nasal prongs because they had the greatest internal diameter. Selection of appropriate ventilator settings to avoid potentially dangerous volume delivery is highly dependent on the type of delivery device. In our clinical experience, nasal CPAP prongs are the best choice for delivering nasal SIMV using peak pressures of 20 ( P15) and inspiratory time of 0.5 seconds. Nasal cannula should be used only when CPAP prongs are too large for the premature infant.

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