Seventy doctors and nurses from neonatal units administered positive pressure ventilation to a term newborn manikin using a Neopuff T-piece device. Recordings were made (1) before training, (2) after training in mask handling and (3) 3 weeks later. Leak and obstruction were calculated.
Median (IQR) leak was 71% (32–95%) before training, 10% (5–37%) directly after training and 15% (4–33%) 3 weeks later (p<0.001). When leak was minimal, gas flow obstruction was observed before, directly after training and 3 weeks later in 46%, 42% and 37% of inflations, respectively.
The training provided included the following demonstrated mask technique:
- Place the manikin’s head in a neutral position and gently roll the mask upwards onto the face from the tip of the chin.
- Hold the mask with the two-point-top hold where the thumb and index finger apply balanced pressure to the top flat portion of the mask where the silicone is thickest.
- The stem is not held and the fingers should not encroach onto the skirt of the mask.
- The thumb and index finger apply an even pressure on top of the mask.
- The third, fourth and fifth fingers perform a chin lift with the same pressure upwards as applied by the thumb and index finger downwards.
In this technique the mask is squeezed onto the face, between the downward thrust of the fingers and upward pull of the chin lift.
Leak and obstruction with mask ventilation during simulated neonatal resuscitation
Arch Dis Child Fetal Neonatal Ed 2010;95:F398-F402
Even with the right technique, adequacy of ventilation can be hard to assess. Principles to bear in mind are:
- International guidelines recommend that infants with inadequate breathing or bradycardia be given positive pressure ventilation (PPV) via a face mask with a self-inflating bag, flow-inflating bag or T-piece device.
- Adequacy of ventilation is then judged by assessing the heart rate.
- However, if the heart rate does not increase, chest wall movements should be assessed to gauge adequacy of ventilation.
- A human observational study reported a mean VT of 6.5 ml/kg in spontaneous breathing preterm infants in the first minutes of life.
- When assisted ventilation is required, a peak inflating pressure (PIP) is chosen with the assumption that this will deliver an appropriate VT.
- However, lung compliance and therefore the PIP required to deliver an appropriate VT vary in the minutes after birth.
- It is likely that there are even greater differences between infants as the mechanical properties of the lung vary with gestational age and disease states.
- In addition, many infants breathe during PPV adding to the inconsistency of VT delivered with a set PIP. Therefore, relying on a fixed PIP and subjective assessment of chest wall movement may result in either under- or over-ventilation.
- Animal studies have shown that PPV with VT >8 ml/kg or inflations with large VTs can damage the lungs.
In an observational study of actual newborn resuscitations in Melbourne, researchers measured inflating pressures and VT delivered using a respiratory function monitor, and calculated face mask leak. After 60 seconds of PPV, resuscitators were asked to estimate VT and face mask leak. These estimates were compared with measurements taken during the previous 30 s.
In 20 infants, the median (IQR) expired tidal volume (VTe) delivered was 8.7 ml/kg (5.3–11.3). VTe and mask leak varied widely during each resuscitation and between resuscitators, who were also poor at estimating VT and mask leak.
Assessment of tidal volume and gas leak during mask ventilation of preterm infants in the delivery room.
Arch Dis Child Fetal Neonatal Ed. 2010 Nov;95(6):F393-7