How Does Respiratory Rate Affect Alveolar Ventilation in Pediatric Patients?

Abstract

Objective: Minute ventilation is a combination of alveolar ventilation (V'alv) and dead space ventilation which is also a result of multiplication of respiratory rate (RR) by tidal volume. V'alv is the volume of the air which reaches the alveoli per minute by definition. The aim of this study was to examine the effect of RR on V'alv in a pediatric physiologic bench setting. Method: In our study, respiratory parameters of a male child, approximately 1 year old, 78 cm in length and ideal body weight of 10 kg, were simulated. This model was ventilated in two different RR settings and with two different breathing circuits which has different dead space (DS) values. However amount of CO2 was kept same during whole bench. Static compliance, static resistance, end-tidal-carbondioxide, positive end expiratory pressure, peak inspiratory pressure, inspiratory time, expiratory-time values of each breathing circuit were taken as the mean and standard deviation of repeated measurements. Results: V'Alv decreased from 1.84+-0.3 L/m to 1.63+-0.5 L/m (p<0.001) in the pediatric circuit and decreased from 1.95+-0.3 L/m to 1.83+-0.5 L/m (p<0.001) in neonatal circuit group. Conclusion: Younger patients should be ventilated with higher RR because of their physiology. Additionaly, regarding the current guidelines in pediatric mechanic ventilation, higher RR should be selected in restrictive lung disease condition. Therefore, clinicians should be more alert particularly in the younger and/or in the restrictive lung disease group regarding both the increased RR and the increased percentage of instrumental DS which results in a decreased V'alv.

Keywords

• alveolar ventilation
• dead space
• respiratory rate
• minute ventilation
• mecahnical ventilation
• pediatric intensive care unit