Reply to ‘Failure to THRIVE—no cause for alarm’

Abstract

Editor—We would like to thank Keeley1Keeley S. Failure to tTHRIVE—no cause for alarm.Br J Anaesth. 2018; 121: 97-98Abstract Full Text Full Text PDF PubMed Scopus (1) Google Scholar for his comments regarding our prospective randomised controlled trial that examined the effect of the ‘transnasal humidified rapid insufflation ventilatory exchange’ (THRIVE) technique on apnoea time and ventilatory effect in children.2Riva T. Pedersen T.H. Seiler S. et al.Transnasal humidified rapid insufflation ventilatory exchange for oxygenation of children during apnoea: a prospective randomised controlled trial.Br J Anaesth. 2018; 120: 592-599Abstract Full Text Full Text PDF PubMed Scopus (58) Google Scholar Studies of apnoeic oxygenation from the beginning of the 20th century reveal the necessity of a patent airway, administration of 100% oxygen, and denitrogenation. In 2015, Patel and Nouraei3Patel A. Nouraei S.A. Transnasal Humidified Rapid-Insufflation Ventilatory Exchange (THRIVE): a physiological method of increasing apnoea time in patients with difficult airways.Anaesthesia. 2015; 70: 323-329Crossref PubMed Scopus (421) Google Scholar showed even longer apnoea times with THRIVE with a proposed mechanism of increasing CO2 elimination by ventilatory exchange. THRIVE has become popular and raised excitement in the anaesthesia community. However, the exact physiologic mechanisms involved are still unclear. It has been proposed that THRIVE generates a cascade of vortex flows from the upper larger airways to the lower smaller airways. This should combine the physiologic diffusion effect of gas exchange during apnoeic oxygenation with an additional CO2 elimination mechanism. Based on adult data and on preliminary paediatric data,4Riva T. Seiler S. Stucki F. Greif R. Theiler L. High-flow nasal cannula therapy and apnea time in laryngeal surgery.Paed Anaesth. 2016; 26: 1206-1208Crossref PubMed Scopus (26) Google Scholar we also expected that THRIVE would be superior to low-flow techniques eliminating CO2 in children. Surprisingly, transcutaneous CO2 (tcCO2) increased without differences between low-flow and high-flow groups in our study.2Riva T. Pedersen T.H. Seiler S. et al.Transnasal humidified rapid insufflation ventilatory exchange for oxygenation of children during apnoea: a prospective randomised controlled trial.Br J Anaesth. 2018; 120: 592-599Abstract Full Text Full Text PDF PubMed Scopus (58) Google Scholar No ventilatory effect was observed with THRIVE in small children weighing 10–20 kg at 2.0 L kg−1 min−1. Also, the smaller the child, the more significant was the tcCO2 increase during apnoea, likely because of their higher CO2 production kg−1 min−1.5Polgar G. Weng T.R. The functional development of the respiratory system from the period of gestation to adulthood.Am Rev Respir Dis. 1979; 120: 625-695PubMed Google Scholar However, studies on neonates,6Saslow J.G. Aghai Z.H. Nakhla T.A. et al.Work of breathing using high-flow nasal cannula in preterm infants.J Perinatol. 2006; 26: 476-480Crossref PubMed Scopus (177) Google Scholar infants,7Spence K.L. Murphy D. Kilian C. McGonigle R. Kilani R.A. High-flow nasal cannula as a device to provide continuous positive airway pressure in infants.J Perinatol. 2007; 27: 772-775Crossref PubMed Scopus (129) Google Scholar and adults8Groves N. Tobin A. High flow nasal oxygen generates positive airway pressure in adult volunteers.Aust Crit Care. 2007; 20: 126-131Abstract Full Text Full Text PDF PubMed Scopus (292) Google Scholar have shown that high flow nasal oxygen (HFNO) therapy generates low-level continuous positive airway pressure, even with an open mouth. This might prevent atelectasis and improve gas exchange by minimising reduction of functional residual capacity in small children. With that, HFNO might contribute to the prolongation of apnoea time. Additionally, warming and humidification of oxygen is advantageous in long-term use as it prevents drying of the alveolar mucosa. Continuous oxygen delivery reduces the risks of periprocedural hypoxaemia, especially in cases of difficult paediatric airway management, thus enhancing patient safety. The authors declare that they have no conflicts of interest. Failure to THRIVE: no cause for alarmBritish Journal of AnaesthesiaVol. 121Issue 1PreviewThe unsurprising results outlined in the recent paper by Riva and colleagues1 should serve to remind us that all that what is new may be just the old in a different guise. Physiologists have studied the mechanism for gas exchange in apnoea since the 1950s. Measured at the mouth, in apnoea there is oxygen uptake but no carbon dioxide output.2 The mass movement of air is occurring in only one direction preventing elimination of carbon dioxide. The driving pressure for oxygenation is a result of the differential uptake of oxygen from the lung compared with the delivery of carbon dioxide. Full-Text PDF Open Archive