The short-term efficacy of high flow nasal oxygen therapy on cardiovascular surgical patients: a randomized crossover trial

Abstract

Background: Oxygen therapy after extubation in the intensive care unit (ICU) is essential in order to maintain adequate oxygenation, especially in patients who have undertaken cardiovascular surgery. A Venturi mask (VM) has been routinely used as an oxygen therapy in the ICU. Recently, however, the high flow nasal cannula (HFNC) has become available, and this device can deliver up to 60 L/min of humidified oxygen. The aim of this study is to evaluate the short-term efficacy between HFNC and VM in cardiovascular surgical patients.

Methods: Forty patients who underwent cardiovascular surgery were randomized to either protocol A (HFNC followed by VM) or protocol B (VM followed by HFNC). After 60-minutes of use with either device, arterial blood gas analysis was performed, and the PaO₂/FiO₂ ratio (PFR) was calculated. Simultaneously, physiological data (respiratory rate, heart rate, mean arterial pressure, continuous cardiac index, and mixed venous oxygen saturation) were recorded. During this procedure, FiO₂ and gas flow were maintained at a fixed rate. These variables were compared by using the paired t-test, and a p value < 0.05 was considered significant. All data were expressed as mean (standard deviation).

Results: Thirty-five patients (17 from protocol A and 18 from protocol B) were enrolled, and 5 patients were excluded from analysis in accordance with the exit criteria. PaO₂ was significantly higher in the HFNC group than in the VM group [101.7 (25.9) vs. 91.8 (23.0), mean difference 9.87 (18.5), 95% confidence interval 3.5 to 16.2, p = 0.003]. Moreover, PFR was significantly higher in the HFNC group than in the VM group [265.9 (81.4) vs. 238.7 (68.5), p = 0.002]. Moreover, PaCO₂ was significantly lower in the HFNC group than in the VM group [33.8 (3.5) vs. 34.7 (2.9), p = 0.033]. The respiratory rate was significantly lower in the HFNC group than in the VM group [18 (4) vs. 21 (4), p = 0.006], and no significant differences were seen in any of the other parameters.

Conclusions: Compared to VM, HFNC ameliorated oxygenation function and decreased patients' effort in breathing. The hemodynamic state did not differ between HFNC and VM. Therefore, HFNC can be used safely in cardiovascular surgical patients.

Trial registration: This trial was registered with the UMIN Clinical Trials Registry (ID UMIN000016572).

Keywords: Cardiovascular surgery; High flow nasal oxygen therapy; Oxygen therapy after extubation; Venturi mask.

Fig. 1

A Patient flowchart of this trial. VM, Venturi mask; HFNC, high flow nasal cannula; RR: respiratory rate; HR, heart rate; MAP, mean arterial pressure; CCI, continuous cardiac index; SvO₂ mixed venous oxygen saturation. B Patient flow after randomization. VM, Venturi mask; HFNC, high flow nasal cannula; RR: respiratory rate; HR, heart rate; MAP, mean arterial pressure; CCI, continuous cardiac index; SvO₂, mixed venous oxygen saturation

Fig. 2

HFNC vs. VM (ABG analysis). HFNC, high flow nasal cannula; VM, Venturi mask; PFR, PaO₂/FiO₂ ratio. Horizontal lines indicate the mean value of each device

Fig. 3

HFNC vs. VM (physiological data). HFNC, high flow nasal cannula; VM, venture mask; RR, respiratory rate; HR, heart rate; MAP, mean arterial pressure; CCI, continuous cardiac index; SvO₂, mixed venous oxygen saturation. Horizontal lines indicate the mean value of each device