Positive expiratory pressure (PEP) therapy. What pressures do we achieve in young children with cystic fibrosis? A single-centre study

Airway clearance therapy (ACT) is a key aspect of the management in cystic fibrosis (CF).1 CF lung disease is characterised by a cycle of infection, inflammation and airway obstruction which may progress to bronchiectasis.2 ACT aims to clear mucus within the airways to slow progression of lung disease.3

Several forms of ACT are used for individuals with CF, however, no form has been shown to be superior. UK CF standards on ACT state that ‘all CF patients should be considered for positive expiratory pressure (PEP) therapy’. The guidance further recommends that for young children the appropriate resistance is one which ‘achieves a stable mid-expiratory pressure of 10–20 cm H₂O’.4 This recommendation is based on evidence from adult cohorts and minimal published data is available for young children. At the Royal Hospital for Children Glasgow, babies newly diagnosed with CF begin a daily ACT regimen involving PEP therapy via a fitted mask and assisted autogenic drainage (AAD). Therapy is performed on the parent’s knee with 2 min alternating cycles of PEP and AAD (four times).5 The initial PEP resistor diameter is set to 3.5 mm for term babies. This has been determined through clinical experience; to achieve an increase in resistance without a significant increase in work of breathing. At routine reviews, resistor size is adjusted using clinical judgement.

The aim of this study was to measure pressures achieved by young children using PEP therapy in a CF cohort at a UK specialist paediatric CF centre.

A clinical review of pressures achieved during PEP therapy in young children attending a specialist CF centre was conducted. Children under 4 years of age receiving PEP mask therapy as part of their routine care were evaluated while parents performed their ACT on their knee. Data were collected by the physiotherapist using a digital manometer and measured over a cycle of five breaths with the peak pressures being recorded. Observations made in each child were recorded as; settled normal breathing, settled forced breathing, crying and settled but with hiccups.

Twenty-one young children with CF (female=10) were included in the study. Median age was 17 months median age is 17 months (IQR 6–22 months). Initial resistor sizes ranged from 2.5 to 3.5 mm. A mean pressure of 3.74 cm H₂O (range 0.3–16.18 cm H₂O) were recorded across the cohort. Table 1 shows further details of data collected and figure 1 shows a scatter plot of pressures achieved with increased age. A subset of six children had the test repeated using a 1.5 mm resistor. This was performed as part of their clinical management to identify whether using a higher resistance would achieve a higher expiratory pressure. Two of these children showed an increase of greater than 2 cm H₂O with the remaining four having negligible differences (table 1).

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Young children achieved an average pressure of 3.74 cm H₂O with their routine PEP therapy. Values above 10 cm H₂O during tidal volume breathing were not achieved within our cohort. Children are known to have higher airway resistance with higher chest wall compliance.2 It could therefore be hypothesised that much lower PEP pressures may be effective. Furthermore, this study found that increasing age or changing resistor size does not relate to achieving higher pressures. One older child (subject 7) was able to achieve higher pressures above 10 cm H₂O but only when prompted by a parent to ‘blow harder’. Switching to a ‘more active’ PEP device when the child is able to (around 3 years of age) may be more effective in achieving higher consistent PEP pressures.6

Further work is required to establish the efficacy of these lower pressures in young children with CF.

Footnotes

• Twitter: @niamh_kiernan, @barryjohnstone9

• Contributors: PA, RS and NK conceived of the presented idea. PA developed the theory and NK and PA performed the computations. BJ and NK verified the data and formatted the graphs. PA encouraged NK to investigate previous work and standard. All authors discussed the results and contributed to the final manuscript.

• Funding: The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.

• Competing interests: None declared.

• Patient consent for publication: Not required.

• Provenance and peer review: Not commissioned; externally peer reviewed.

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References

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