|Year : 2019 | Volume
| Issue : 1 | Page : 4-9
Comparison of high-flow nasal cannula versus conventional oxygen therapy following extubation after paediatric cardiac surgery
Vijitha Burra, Adalagere Sathyanarayana Lakshmi, Anand V Bhat, V Prabhakar, N Manjunatha
Department of Cardiac Anesthesia and Critical Care, Sri Jayadeva Institute of Cardiovascular Sciences and Research, Bangalore, Karnataka, India
|Date of Web Publication||25-Apr-2019|
Dr. Adalagere Sathyanarayana Lakshmi
Department of Cardiac Anesthesia and Critical Care, Sri Jayadeva Institute of Cardiovascular Sciences and Research, Bangalore - 560 069, Karnataka
Source of Support: None, Conflict of Interest: None
Background: Respiratory complications after cardiac surgery increase morbidity, mortality and length of hospital stay. Oxygen administered using a high-flow nasal cannula (HFNC) improves oxygenation because of its ease of implementation, tolerance and clinical effectiveness. We sought to compare this technique with conventional oxygen therapy (OT) after extubation following paediatric cardiac surgery. We compared HFNC versus conventional OT in postoperative paediatric cardiac surgical patients. Our primary objective was to evaluate the relative efficiency of improving PaCO2elimination in the first 48 h following extubation. Patients and Methods: A single-centre, prospective, unblinded, randomised controlled trial was conducted in a 15-bedded post-cardiac intensive care unit on 50 paediatric cardiac surgical patients <2 years of age undergoing elective surgery with Risk Adjustment for Congenital Heart Surgery score ≥2. At the start of weaning off ventilation, patients were randomly assigned to either of the following groups: HFNC or OT. Arterial blood samples were collected before and following extubation at the following time points: 1, 6, 12, 24 and 48 h. While the primary outcome was comparison of arterial PaCO2post-extubation, the secondary outcomes were PaO2and PaO2/FIO2 ratios and any complications associated with either technique. Continuous data were expressed as mean ± standard deviation and compared using independent samples t-test or the Mann–Whitney U-test. Chi-square test was used for categorical parameters. Results: Demographic and clinical variables were comparable in the two groups. PaO2and PaO2/FIO2 ratios were significantly improved in the HFNC group (P < 0.05) with lesser requirement of FIO2(P < 0.05) in comparison to conventional OT. No complications were observed during HFNC therapy, nor was there any treatment failure. Conclusion: Compared with conventional OT, the use of HFNC following extubation in paediatric cardiac surgical patients appears to be safe, improves oxygenation and carbon dioxide elimination with lesser inspired oxygen concentration.
Keywords: Conventional oxygen therapy, high-flow nasal cannula, postoperative paediatric cardiac surgery
|How to cite this article:|
Burra V, Lakshmi AS, Bhat AV, Prabhakar V, Manjunatha N. Comparison of high-flow nasal cannula versus conventional oxygen therapy following extubation after paediatric cardiac surgery. Airway 2019;2:4-9
|How to cite this URL:|
Burra V, Lakshmi AS, Bhat AV, Prabhakar V, Manjunatha N. Comparison of high-flow nasal cannula versus conventional oxygen therapy following extubation after paediatric cardiac surgery. Airway [serial online] 2019 [cited 2019 Dec 11];2:4-9. Available from: http://www.arwy.org/text.asp?2019/2/1/4/257048
| Introduction|| |
High-flow nasal cannula (HFNC) ventilation refers to the delivery of a mixture of air and oxygen through a humidified circuit at very high flows which exceed the spontaneous inspiratory demand of the patient. HFNC delivers heated and humidified gases and provides some level of continuous positive airway pressure (CPAP). A flow-dependent effect of CPAP has been documented in healthy volunteers and in patients with chronic obstructive pulmonary disease treated with HFNC. The use of HFNC has been shown to decrease airway resistance and to flush nasopharyngeal dead space, thus contributing to reduced work of breathing favouring the elimination of carbon dioxide (CO2) and bronchial secretions., HFNC is widely used for the treatment of respiratory failure in children with bronchiolitis.,, However, there has been only one study on the use of HFNC after paediatric cardiac surgery.
The primary aim of our study was to evaluate CO2 elimination and effect on PaO2/FIO2 ratios post-extubation after paediatric cardiac surgery using HFNC or conventional oxygen therapy (OT).
| Patients and Methods|| |
The study was a single-centre prospective, unblinded, randomised controlled trial conducted on 50 children in a 15-bedded paediatric cardiac intensive care unit following approval by the Institutional Ethics Committee. Informed consent was obtained from parents. The objective of the study was to evaluate the relative efficacy of HFNC and conventional OT on CO2 elimination and oxygenation. It also aimed to evaluate which of these two techniques provided better PaO2/FIO2 values at different time points up to 48 h post-extubation. Efficacy was determined by normal CO2 levels (35–40 mm Hg) and higher PaO2 levels with better PaO2/FIO2 values. Other outcomes studied included reintubation rate and development of nasal prongs-related complications such as nasal ulcers, gastric distension and need for supplemental sedation.
Children younger than 2 years undergoing elective cardiac surgery under cardiopulmonary bypass (CPB) with a Risk Adjustment for Congenital Heart Surgery (RACHS) score of 2 and above were included in the study. Children with major congenital malformations or neuromuscular disease, postoperative presence of a non-drained pneumothorax or pleural effusions, on ventilator support before surgery, cyanotic children undergoing palliative surgeries and absence of informed consent were excluded from the study. The allocation sequence was generated by a computerised random generation programme. Fifty children were evaluated for eligibility before surgery and randomised at the beginning of weaning off ventilation into HFNC therapy and conventional OT groups.
While all patients received general anaesthesia with inhalational induction, maintenance of general anaesthesia varied according to the preference of the anaesthesiologist. CPB was maintained according to our institutional protocol. At the end of the surgical procedure, children were transferred to the post-cardiac intensive care unit (PCICU) for postoperative monitoring and weaning off ventilator support. All patients were ventilated using synchronised intermittent mandatory ventilation (SIMV) mode with tidal volumes in the range of 6–8 mL/kg. Positive end-expiratory pressure values ranged from 3 to 5 cm H2O, and the children were sedated with a continuous infusion of dexmedetomidine (0.5 μg/kg/min).
Once haemodynamic stability was achieved (heart rate, arterial blood pressure and central venous pressure within normal values), weaning from mechanical ventilation was started. In this phase, they were weaned off SIMV till pressure support in the range of 10–15 cm H2O was achieved. If gas exchange was within the normal range as determined by arterial blood gas analysis, a trial of CPAP (10–15 cm H2O) was set for 30 min, to be followed by extubation. Ability to breathe spontaneously was judged by the attending anaesthesiologist using PaCO2 of 35–40 mm Hg and peripheral oxygen saturation (SpO2) above 90% for extubation. HFNC or conventional OT was used according to the randomisation arm. The attending physician titrated the FIO2 of the administered mixture to achieve an SpO2> 90%. In all patients, a nasogastric feeding tube was placed and left open for the first 6 h.
For HFNC therapy, the appropriate-sized nasal cannula was selected, and the gas mixture was set at 2 L/kg/min. FIO2 was titrated in increments of 0.1–0.2 to maintain SpO2 of > 92%. For conventional OT, cannulas delivering a maximum flow rate of 6–8 L/min were used. The FIO2 in the conventional OT group was calculated using Finer's formula for low-flow OT.,
OT or HFNC therapy support was considered to have failed if the patient's parameters met the criteria for cardiac and respiratory failure. In infants in whom OT failed, treatment was escalated to HFNC followed by endotracheal intubation, whereas infants in whom HFNC failed were treated straight away by endotracheal intubation. At any point in the study, need for urgent intubation and mechanical ventilation was determined by the attending anaesthesiologist.
Demographic data (such as age, weight and diagnosis) and baseline data (such as time on CPB, duration of mechanical ventilation, neonatal age and presence of cyanotic disease) were recorded. Arterial blood gases were checked and collected with the child receiving CPAP before extubation and 1, 6, 12, 24 and 48 h after extubation. At the same time points, heart rate, systolic blood pressure, diastolic blood pressure and respiratory rate were recorded. The presence of nasal ulcers, need for supplemental sedation and gastric distension were recorded every 4 h. The duration of mechanical ventilation and length of PCICU stay were also recorded.
All data were collected on a Microsoft Excel 2012 (Microsoft: Redmond, Washington, USA) database specifically prepared for this study. Continuous data were expressed as mean ± standard deviation or the median and 25th–75th interquartile range and compared by an independent samples t-test or the Mann–Whitney U-test as appropriate for comparison of continuous variables between the two groups (i.e., data at baseline). Chi-square test was used for categorical parameters. P < 0.05 was considered statistically significant.
| Results|| |
Fifty children were enrolled for the study (25 in the HFNC group and 25 in the OT group). Demographic data were comparable between the two groups as shown in [Table 1]. Baseline parameters (PaO2, PaCO2 and FIO2) were comparable between the two groups. PaO2 values at 6, 12, 24 and 48 h post-extubation were significantly higher in HFNC group (P < 0.05) [Table 2], while PaCO2 values were significantly lower in the HFNC group at 1, 6 and 12 h post-extubation (P < 0.05) [Table 3]. FIO2 and PaO2/FIO2 values in HFNC group at all-time points post-extubation were higher and statistically significant [Table 4] and [Table 5]. [Table 6] shows the PaO2, PaCO2 and PaO2/FIO2 with values of significance at various time intervals.
|Table 3: Arterial carbon dioxide tension (PaCO2) at different time points|
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|Table 6: ANOVA for PaO2, PaCO2 and PaO2/FIO2 at various time points post-extubation|
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No child developed HFNC-related complications, such as nasal ulcers or need for supplemental sedation. RACHS category of both the groups of children were comparable (P = 0.056). The mean duration of ventilation was 23.6 ± 16.1 h versus 23.2 ± 10.7 h (HFNC vs OT), with the difference between the two groups being statistically insignificant (P = 0.808).
| Discussion|| |
The use of HFNC has recently gained increasing acceptance and popularity in the treatment of several respiratory conditions. HFNC is currently being applied to patients of all age groups ranging from preterm infants to adults. Several clinical uses for HFNC have been proposed such as to prevent extubation failure, as a primary therapy for respiratory distress syndrome and bronchiolitis and to wean from nasal CPAP. HFNC therapy has become popular because of the ease of application, tolerability and safety.
Our primary aim was to compare postoperative PaCO2 values post-extubation. Using HFNC in an acute lung injury model in piglets, Frizzola et al. demonstrated a flow-dependent improvement in gas exchange as evidenced by the PaCO2. Accordingly, we speculated that the increased flow of HFNC was able to flush the nasopharyngeal space and improve CO2 elimination post-extubation following paediatric cardiac surgery. We have demonstrated that HFNC therapy decreases PaCO2 post-extubation in children. Our findings also confirmed the efficacy of HFNC in improving the PaO2 postoperatively and are similar to other studies.
Roca et al. found a significant improvement in respiratory parameters and arterial blood gases in adults as early as 30 min of HFNC in comparison with 30 min of conventional face mask OT. Our study showed a beneficial effect of HFNC in improving PaO2 levels at 1, 6, 12, 24 and 48 h post-extubation with lesser requirement of FIO2 compared to conventional OT (P < 0.05). The HFNC group also had better CO2 elimination as compared to the conventional OT group, being statistically significant at 1, 6 and 12 h post-extubation. PaO2/FIO2 ratio variation was significant between two groups at all time points following extubation (with higher values in HFNC group; P < 0.05).
In a randomised cross-over study in premature infants, Woodhead et al. compared HFNC (3.1 ± 0.6 L/min) with non-humidified high-flow oxygen (1.8 ± 0.4 L/min) and found a significantly lower rate of reintubation in the HFNC group. Holleman-Duray et al. did a retrospective analysis on 114 premature infants and compared the use of HFNC (4-6 L/min) versus ventilator CPAP (8 cm H2O). They concluded that infants extubated to HFNC spent significantly fewer days on the ventilator. Schibler et al. studied 167 infants with bronchiolitis supported with HFNC and showed that <5% of infants required intubation. McKiernan et al. showed that HFNC reduced intubation rates in patients with bronchiolitis. We observed no complications such as nasal ulcer, gastric distension, non-compliance or irritability during HFNC therapy. However, a nasogastric tube was left in the place for the first 48 h post-extubation as a protocol in all patients. Overall, our study confirms the safety of the use of HFNC even with minimal staff training. In addition, it is important to underline the simplicity of and tolerability to HFNC. This observation is in agreement with the other studies.
In a randomised controlled trial, Campbell et al. found no differences in the incidence of complications or in the reintubation rate between the nasal CPAP and HFNC groups. In preterm infants, HFNC appears to be better tolerated and causes less trauma to the nasal septum. In a prospective observational study, ten Brink et al. confirmed the safety of HFNC in patients with moderate-to-severe respiratory distress. We used flow rates of 2 L/kg/min as was used by ten Brink et al. Previous research had shown that these flows create a distending pressure of 4–8 cm H2O which could result in improvement of functional residual capacity.
The present study has some limitations. The period of observation was relatively short and limited to 48 h. However, this is in accordance with the PCICU admission and length of stay and a relatively small number of patients required a PCICU stay longer than 48 h. Our study was aimed at evaluating the effect of HFNC and conventional OT on clinical variables such as PaO2, PaCO2 and PaO2/FIO2 ratio. We were not able to measure nasopharyngeal pressure and our study was not designed to clarify whether a CPAP effect was present in HFNC patients.
| Conclusion|| |
HFNC decreases PaCO2 and improves oxygenation in infants following extubation after cardiac surgery. HFNC can be considered as a safe and effective alternative to conventional OT following paediatric cardiac surgery.
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Conflicts of interest
There are no conflicts of interest.
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[Table 1], [Table 2], [Table 3], [Table 4], [Table 5], [Table 6]