BRIEF REPORTS

http://dx.doi.org/10.5546/aap.2017.eng.277

Early use of continuous positive airway pressure in the treatment of moderate to severe acute lower respiratory tract infections among patients younger than 2 years old

Laura Figueroa, M.D.^a and Federico Laffaye, M.D.^a

a. Pediatric Intermediate Care Unit. Hospital Provincial Neuquen "Dr. E. Castro Renddn".

Collaborators: Mario González, Germán Kaltenbach, Viviana Arias y Eugenia Cerda.

E-mail address: Laura Figueroa, M.D.: lauritafigueroa@yahoo.com.ar

Funding: None.

Conflict of interest: None.

Received: 5-9-2016
Accepted: 12-26-2016

ABSTRACT

Objective. To analyze the characteristics of patients younger than 2 years old who had a moderate to severe acute lower respiratory tract infection and were treated early with bubble continuous positive airway pressure, and factors associated with a successful intervention.
Method. Retrospective and descriptive study. Children younger than 2 years old admitted to the Pediatric Intermediate Care Unit of Hospital Provincial Neuquen between June 2009 and December 2010. Bubble continuous positive airway pressure was used, and the following outcomes were measured: heart rate, respiratory rate, Tal's score, oxygen saturation, and fraction of inspired oxygen at 0, 2, 6, 24, and 48 h.
Results. One hundred and twenty patients were included. Their median age was 3 months old. The intervention was successful in 72% of patients. At 2 h, a 15% reduction in respiratory rate, and a 2-point decrease in Tal's score were predictors of success, with an odds ratio of 6.41 (95% confidence interval: 2.68-15.36), and of 9.07 (95% confidence interval: 3.72-22.19), respectively.
Conclusions. A reduction in respiratory rate, heart rate, and Tal's score at 2 hours of starting the intervention were predictors of success.

Key words: Bubble CPAP; Bronchiolitis; Pneumonia; Children.

INTRODUCTION

Acute lower respiratory tract infections (ALRTIs) are an important cause of morbidity and mortality in our setting.¹

The main clinical conditions included under the definition of ALRTI are bronchiolitis and pneumonia, which have a greater impact on childhood mortality,² and set the basis for this study.

Non-invasive ventilation is an alternative for patients with moderate to severe ALRTIs.^3-6 Different publications have mentioned a reduction in the length of hospital stay and a lower proportion of failure (less than 30%), defined as the need for endotracheal intubation.⁷

The objective of this study was to analyze the characteristics of patients younger than 2 years old who had a moderate to severe ALRTI and treated early with bubble continuous positive airway pressure (CPAP), and factors associated with a successful intervention.

POPULATION AND METHODS

Retrospective and descriptive study. Children younger than 2 years old hospitalized between June 2009 and December 2010. Bubble CPAP was used, and the following outcomes were measured: heart rate (HR), respiratory rate (RR), Tal's score, oxygen saturation, and fraction of inspired oxygen (FiO₂) at 0, 2, 6, 24, and 48 h.

Inclusion criteria for the use of bubble CPAP were as follows:

• Age between 1 and 24 months old.
• Weight < 12 kg.
• Tal's score > 5 points.
• Admission to the pediatric intermediate care unit.

Exclusion criteria were the following:

• Cardiorespiratory arrest.
• Hemodynamic instability in spite of intravenous treatment with volume expanders.
• Inotrope requirement.
• Absence of gag and/or cough reflex.

Bubble CPAP consists of an interface (nasal cannula), inspiratory tubing, and expiratory tubing immersed in an underwater bottle system. The patient breaths spontaneously with positive pressure air flow, during both inspiration and expiration. Thus, continuous positive airway pressure is maintained throughout the breathing cycle.

CPAP includes an oxygen blender connected to a source of oxygen and compressed air used to supply an appropriate concentration of inspired oxygen (FiO₂). The humidified blended oxygen is then circulated through corrugated tubing. FiO₂ is estimated based on the liters of air and oxygen delivered. Blended oxygen is delivered via a nasal cannula, and pressure in the circuit is maintained by immersing the distal end of the expiratory tubing in water. The depth to which the tubing is immersed underwater determines the pressure generated in the patient's airways (Figure 1).

Figure 1. Bubble continuous positive airway pressure flow

Prior to placing the nasal interface, airway secretions were cleared and, if deemed convenient, a dose of sedative was given (chloral hydrate or benzodiazepines).

The Hudson RCI CPAP Cannula System (USA), sizes 1-5, was used. Bubble CPAP was first connected at 5 cm H₂O and, eventually, this level was progressively increased up to 8 cm H₂O, although a higher initial pressure could be used at the discretion of the treating physician. In addition, initial FiO₂ was 100% and then reduced based on the patient's saturation.

Comorbidities were recorded: congenital heart disease, prematurity, malnutrition, bronchopulmonary dysplasia, and high social risk (unmet basic needs).

The presence of complications, such as abdominal distension, pressure injury, and pneumothorax, was determined.

In addition, patients' weight, age, sex, diagnosis, virological tests (indirect immunofluorescence assay [ilFA], polymerase chain reaction [PCR]), culture results, sedative administration, length of bubble CPAP use, and length of stay in the pediatric intensive care unit (PICU) were recorded.

CPAP was considered successful if the RR reduced by 15% from the previous value and Tal's score decreased by 2 points. CPAP was considered to fail if Tal's score did not reduce (HR, RR, intercostal retraction, wheezing) and/or desaturation (< 90%) and/or sensory deficit occurred, at the discretion of the treating physician.

Criteria to remove bubble CPAP were as follows: CPAP at 4 cm HjO, FiO₂ < 40%, Tal's score of 4 points.

Simple descriptive statistics were used to describe the sample: mean, median, standard deviation (SD), and range. Percentages corresponding to qualitative outcome measures were estimated and compared using a x² test for independence to establish the association among outcome measures, with a significance level < 5%. Odds ratios (ORs) were analyzed for all possible cases. In addition, box-and-whisker plots were used to describe how quantitative outcome measures behaved.

Sensitivity and specificity curves were used to establish cut-off points for bubble CPAP failure predictive outcome measures. Receiver operating characteristic (ROC) curves and their corresponding tests were used to establish which outcome measures worked better to determine bubble CPAP failure.

The study protocol was assessed and approved by the Advisory Commission for Biomedical Research in Humans (Comisión Asesora en Investigación Biomédica en Seres Humanos, CAIBSH).

RESULTS

One hundred and twenty patients were included. The intervention was successful in 72% of cases, and failed in 28%.

Table 1 describes the demographic and clinical outcome measures of enrolled patients before CPAP use and compares successful and failed interventions.

Table 1. Baseline characteristics of the sample and each group as per CPAP success or failure. Age is stated as median and range; the other outcome measures, as mean ± standard deviation

All patients had an indirect immunofluorescence assay (IIFA), and respiratory syncytial virus (RSV) was detected in 70 cases. H1N1 was detected in 5% of patients.

CPAP was established at 5-8 cm H₂O, with an average of 6 cm H₂O.

Complications were observed in 3.3% of cases (abdominal distension, pneumothorax).

Mean bubble CPAP duration was 74.93 h (95% confidence interval [CI]: 65.22-84.65).

Mean length of stay in the intermediate care unit was 10 days (95% CI: 9.11-10.91); in the success group, it was 8.33 days (SD 3.36), and in the failure group, it was 14.93 days (SD 5.19) (the latter included the length of stay in the intensive care unit).

Table 2 shows outcome measures recorded during the hours after initiating bubble CPAP.

Table 2. Results. Respiratory rate, heart, rate, FiO₂, oxygen saturation, and Tal's score

The subsequent analysis identified that a 15% reduction in HR and a 2-point decrease in Tal's score at 2 hours of non-invasive ventilation (NIV) initiation were the factors related to success, with an OR of 6.41 (95% CI: 2.68-15.36), and of 9.07 (95% CI: 3.72-22.19), respectively.

When two qualitative outcome measures are combined, i.e., a 15% reduction in RR and a 2-point decrease in Tal's score at 2 hours, OR increased to 13.31 (95% CI: 4.51-39.26).

No statistically significant findings were made at 24 and 48 h.

DISCUSSION

In our study, we described bubble CPAP use among patients younger than 2 years old with ALRTIs as a treatment strategy to avoid conventional mechanical ventilation.

The intervention was successful in 72% of cases, and failed in 28%. Success percentage was similar to that published by other authors (83% and 75.5%).^8,9

In this study, at 2 hours of NIV initiation with bubble CPAP, a 15% reduction in RR from the previous value and a 2-point decrease in Tal's score were predictors of success.

Other authors have also identified a reduction in RR as a predictor of NIV success.⁶ This fact highlights the importance of monitoring clinical parameters and ongoing assessment of these patients.

Unlike other studies,^8-11 Tal's score was used in this study.

Modified Tal's score has demonstrated to be highly useful in practice for a standardization of clinical management and decision-making.¹²

Although HR significantly reduced at 2 hours, this outcome measure was an adequate predictor of failure as of 6 h, unlike what has been reported by Mayordomo-Colunga et al.,⁸ who mentioned that HR reduction in the first hour was an adequate predictor of success.

In this study, no statistically significant differences were observed between both groups in terms of weight, age, predisposing factors, or bronchiolitis or pneumonia diagnosis. Mayordomo-Colunga et al. indicated that the presence of apnea, a lower weight, and a younger age were predictors of failure,⁸ as well as Antonelli et al.,⁹ who also identified a younger age, a higher Woods' score, acute respiratory distress syndrome (ARDS) or pneumonia.

In our experience, NIV given through bubble CPAP was a highly successful intervention among children with moderate to severe ALRTIs.

CONCLUSION

The early use of bubble CPAP works as a strategy to optimize patients' access to quality care and the utilization of available resources.

In this study, RR, HR at 2 hours, and Tal's score at 2 and 6 hours after NIV initiation were predictors of the success or failure of the intervention.

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