Effect of nasal high flow for postoperative respiratory failure: a prospective observational study

Introduction

We studied the effect of nasal high flow (NHF) for postoperative respiratory failure after extubation in our general surgical ICU. Recently some studies have reported that NHF improves oxygenation and reduces respiratory rate. However, the usefulness of NHF in the general surgical ICU has not been fully determined.

Methods

A prospective observational study was conducted in our general surgical ICU to investigate the effect of NHF on respiratory parameters in patients with postoperative respiratory failure. Patients who were admitted to the ICU for postoperative respiratory failure (defined as oxygen saturation as measured by pulse oximetry <96% and/or respiratory rate>24 beats/minute while receiving more than 6 l/ minute oxygen through a facemask) were eligible in this study. Pre and 1 and 6 hours after NHF treatment, we collected PaO₂, PaCO₂, respiratory rate, heart rate, and blood pressure. Data were presented with means and standard deviations. P < 0.05 was considered statistically significant.

Results

Forty-two patients were treated using NHF in our ICU from February 2013 to November 2013. The mean age of the patients was 62.8 ± 15.8 years, and the male:female ratio was 22:19. PaO₂ values after 1 and 6 hours of NHF (104 ± 34 mmHg, 107 ± 26 mmHg, respectively) were significantly higher than that before NHF (89 ± 38 mmHg; P < 0.02). The PaO₂/FiO₂ ratio was increased from 1 hour to 6 hours of NHF (from 218 ± 90 mmHg to 236 ± 86 mmHg, P < 0.05). Respiratory rate after NHF (19.6 ± 4.7/minute) was significantly lower than that at baseline (22.3 ± 4.8/minute; P = 0.0006), whereas PaCO₂ after NHF was reduced compared with baseline (from 41 ± 7 mmHg to 39 ± 5 mmHg, P < 0.02). Thirty-two (76%, success group) patients did not need other positive ventilation. On the other hand, 10 (24%, failure group) patients required non-invasive positive pressure ventilation or intubation. We compared the failure group with the success group. However, there were no significant differences in vital signs, total bleeding, operative duration and preoperative respiratory function between the groups.

Conclusion

In this study, NHF gradually improved oxygenation. Additionally, NHF reduces the respiratory rate and the value of PaCO₂. This result might suggest that NHF decreased dead-space ventilation. There was no difference between the success group and the failure group. So we can use NHF as the first choice for postoperative respiratory failure, but it is difficult to predict success or failure.