HHHFNC is a new type of noninvasive ventilation mode, which is a new type of neonatal noninvasive respiratory support mode developed on the basis of nasal catheter oxygen therapy[19]. HHHFNC can not only provide humidified respiratory gas and increase the concentration of inhaled oxygen, but also prevent airway heat, water loss and mucosal cilia damage, provide a certain positive airway pressure, improve mucosal perfusion and stimulate respiratory center [20]. It is increasingly widely used in neonatal clinic.
The Meta-analysis showed that there was no significant difference in treatment failure rate and reintubation rate between the HHHFNC and the NCPAP groups. It is worth noting that Collins [9] found there were 22 cases (33.8%) in NCPAP group and 15 cases (22.3%) in HHHFNC group failed in extubation and needed recanalization. The remaining 9 cases in HHHFNC group were successfully extubated after NCPAP and nasal intermittent positive pressure ventilation (NIMV) treatment, without further intubation treatment. A recent forward-looking research has also questioned the effectiveness of HHHFNC in preventing extubation failure of premature infants. The research shows that HHHFNC group (n = 30) and NCPAP group (n = 34) have early-stage babies (28–34 weeks of age) who are respectively subjected to HHHFNC and NCPAP to prevent extubation failure. The failure rate of HHHFNC group (36.7%, 11/30) was significantly higher than that of NCPAP group (14.7%, 5/34), and the difference was statistically significant (P = 0.043). Among the 11 premature infants with extubation failure in HHHFNC group, 5 cases needed to undergo reinsertion therapy, while the remaining 6 cases were successfully extubated after NCPAP therapy and did not need reinsertion therapy [21]. Armanian [6]also pointed out that HHHFNC, as the initial noninvasive auxiliary ventilation mode for the treatment of ARDS in early-born children, increased the risk of recanalization compared with NCPAP. It can be seen that HHHFNC is used to prevent premature infants from extubation failure, and if extubation failure occurs, part of the children can be successfully treated by NCPAP. If NCPAP fails, recanalization and mechanical ventilation are often used to maintain treatment. Chen Jia's research on 129 preterm infants with ultra-low birth weight showed the opposite results. The risk of recanalization within 7 days after primary extubation in HHHFNC group was significantly lower than that in NCPAP group. However, there is no systematic meaning (P > 0.05) in recanalization between the two groups within 3 days after the first extubation. This suggests that HHHFNC has instability in preventing premature infants from extubation failure, which may be related to the adoption of HHHFNC for treatment, the gap between nasal plug and nasal cavity, and the inability to better control airway pressure. Therefore, it is very important to accurately evaluate the real pressure generated by HHHFNC [22, 23].
While in terms of safety, HHHFNC had a significant advantage over NCPAP in reducing the incidence rates of nasal trauma. The reason is that nasal congestion does not need to be completely closed when HHHFNC is used for treatment, thus avoiding the pressure on the skin around the nose. In addition, compared with the traditional nasal catheter oxygen inhalation method, the heating and humidification oxygen infusion method can also reduce the incidence rate of nasal mucous membrane injury and hemorrhage, and increase the comfort of affected children. The results of this study also show that the incidence of frequent hemorrhoid in premature infants in HHHFNC group is lower than that in NCPAP group, and the difference has a systematic meaning. This may be related to the fact that the positive airway pressure produced by HHHFNC therapy is lower than that of NCPAP, and the application phase is relatively warm. A retrospective study conducted by GARG in India included 136 very low birth weight premature infants with gestational age ≤ 32 weeks and birth weight ≤ 1500 g, and the results of analysis also support the above conclusion. In terms of secondary outcomes measurements, there were no significant differences between two groups in the in-hospital mortality rate and incidence rates of BPD, IVH, ROP, and the duration of teaching full enteral feedings [24]. This suggests that HHHFNC does not increase or decrease the risk of premature infants' extubation failure compared with NCPAP. Note that the incidence rate of NEC in infants was significantly lower in the HHHFNC group than NCPAP group (RR: 0.65, 95%CI: 0.43 to 0.98, P = 0.04). This may be related to the treatment of abdominal distension indirectly caused by NCPAP measures, while HHHFNC measures are applied with opposite temperature sum, which produces relatively low abdominal pressure. Considering the safety outcome index, HHHFNC has more advantages than NCPAP in preventing infants from extubation failure.
However, some limitations of this study should be acknowledged. First, the number of research documents included is relatively small, and there are no documents in other languages except Chinese and English, which are representative and have to be verified. Second, there are differences in the basic conditions of the population included in the study, such as fetal age, birth weight, basic diseases, etc. Third, the level of medical treatment and health care in different regions is different, the types and parameter settings of HHHFNC and NCPAP treatment equipment are different, and the main outcome evaluation index and complication occurrence judgment standard are different, which can affect the evidence strength of the conclusion.