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. 2023 Jun 28;10(7):1118.
doi: 10.3390/children10071118.

Incomplete Exhalation during Resuscitation-Theoretical Review and Examples from Ventilation of Newborn Term Infants

Thomas Drevhammar  1 , Peder Aleksander Bjorland  2 , Joanna Haynes  3   4 , Joar Eilevstjønn  5 , Murray Hinder  6   7 , Mark Tracy  6   7 , Siren Irene Rettedal  2   4 , Hege Langli Ersdal  3   4
Affiliations

Incomplete Exhalation during Resuscitation-Theoretical Review and Examples from Ventilation of Newborn Term Infants

Thomas Drevhammar et al. Children (Basel). .

Abstract

Background: Newborn resuscitation guidelines recommend positive pressure ventilation (PPV) for newborns who do not establish effective spontaneous breathing after birth. T-piece resuscitator systems are commonly used in high-resource settings and can additionally provide positive end-expiratory pressure (PEEP). Short expiratory time, high resistance, rapid dynamic changes in lung compliance and large tidal volumes increase the possibility of incomplete exhalation. Previous publications indicate that this may occur during newborn resuscitation. Our aim was to study examples of incomplete exhalations in term newborn resuscitation and discuss these against the theoretical background.

Methods: Examples of flow and pressure data from respiratory function monitors (RFM) were selected from 129 term newborns who received PPV using a T-piece resuscitator. RFM data were not presented to the user during resuscitation.

Results: Examples of incomplete exhalation with higher-than-set PEEP-levels were present in the recordings with visual correlation to factors affecting time needed to complete exhalation.

Conclusions: Incomplete exhalation and the relationship to expiratory time constants have been well described theoretically. We documented examples of incomplete exhalations with increased PEEP-levels during resuscitation of term newborns. We conclude that RFM data from resuscitations can be reviewed for this purpose and that incomplete exhalations should be further explored, as the clinical benefit or risk of harm are not known.

Keywords: infant; intrinsic; newborn; positive end-expiratory pressure; positive pressure ventilation; resuscitation.

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Conflict of interest statement

Joar Eilevstjønn is a Laerdal Medical employee. Siren Rettedal had an unconditional research grant from Laerdal. The other authors have no conflict of interest to disclose.

Figures

Figure 1
Figure 1
Example of a breath with incomplete exhalation. The expiratory time of the first breath was shorter than for the second breath (flow panel solid line) and the expiratory flow does not return to zero (flow panel box indicating magnitude of continued expiratory flow at point of gas flow reversal to inflation). There was higher PEEP with incomplete exhalation (pressure panel dashed line). PEEP was 6.9 cm H2O in first breath and 5.3 cm H2O in second breath.
Figure 2
Figure 2
Example of incomplete exhalation related to increased tidal volumes. The modest increase in tidal volumes (volume panel dashed line) gives incomplete exhalations of increasing magnitude (flow panel box indicating magnitude of continued expiratory flow at point of gas flow reversal to inflation) and increased PEEP (pressure panel dashed line). PEEP was 5.6, 6.5 and 7.9 cm H2O in the three breaths.
Figure 3
Figure 3
Example of increased compliance and tidal volumes during the first minutes of life. The increase in tidal volume in this infant led to incomplete exhalations (right flow panel boxes indicating magnitude of continued expiratory flow at point of gas flow reversal to inflation) with increased PEEP (pressure panel dashed line comparing left to right). This can be explained by the dramatic increase in compliance. The longer time to reach PIP is a consequence of fresh gas flow rate when using TPR as lung compliance increased (right pressure panel).
Figure 4
Figure 4
Example of increased resistance after intubation. Before intubation (left) there was no incomplete exhalation and flow returned to zero. After intubation the increase resistance led to incomplete exhalations (right flow panel box indicating magnitude of continued expiratory flow at point of gas flow reversal to inflation) with an increased PEEP (pressure panel dashed line comparing left to right). After intubation there was reduced compliance and respiratory rate was increased.
Figure 5
Figure 5
Example of increased resistance on both inspiration and expiration. This infant showed incomplete exhalations (flow panel box indicating magnitude of continued expiratory flow at point of gas flow reversal to inflation) but also incomplete inflations with flow not returning to zero and increasing tidal volume when insufflation was terminated. The reduced rate of inspiratory flows can partly be explained by high compliance, but flows are also clearly below the set fresh gas flows, indicating resistance as a cause.
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