Assessment of the effects of vibrating mesh nebulisation versus jet nebulisation on respiratory function in patients with long-term tracheostomy ventilation: evaluating neural respiratory drive, breathing mechanics, cardiac parameters, secretions, and breathlessness

Long-term tracheostomy ventilation (LTTV) is frequently complicated by high secretion burden, arising from accumulation of oronasal and bronchial secretions due to impaired bulbar or cough function. Patients are therefore at an increased risk of sputum plugging and respiratory infection, leading to potentially life-threatening deterioration. In patients undergoing weaning from prolonged mechanical ventilation, liberation from invasive mechanical ventilation can be delayed by excessive secretion burden, detrimentally affecting quality of life and escalating healthcare costs.

The principal treatment strategies for secretion retention are oral and tracheal suction, mucolytic therapy (enteral or nebulised) and mechanical insufflation-exsufflation (MIE). There are few robust data to support the use of these treatment modalities, although they are routinely used in clinical practice on an empirical basis. The use of nebulised hypertonic saline is well-established in the management of non-cystic fibrosis bronchiectasis and is frequently used to aid airway clearance in LTTV patients. Nebulised salbutamol is widely used as a bronchodilator in tracheostomised patients with a tendency to develop bronchospasm, whether due to established obstructive airways disease or airways inflammation from secretion retention or ventilator-associated pneumonia.

Vibrating mesh nebulisation (VMN) is increasingly used for aerosol delivery in mechanically ventilated patients, with advantages including reduced residual volume, quieter operation and higher levels of drug deposition. However, its superiority in improving secretion clearance and bronchodilation compared with jet nebulisation (JN) is yet to be established. Both VMN and JN are currently utilised within clinical practice as standards of care.

This pilot randomised crossover trial seeks to recruit 12 patients to establish whether VMN of hypertonic saline and salbutamol has a greater effect than standard JN in improving:

Neural respiratory drive (measured by assessment of the electrical activity of breathing muscles via parasternal EMG) Secretion burden Breathlessness

Participants will be recruited as inpatients within the Lane Fox Unit. Following consent for trial involvement, there will be a 24-hour washout period receiving normal saline nebulisers. Baseline data including ventilator settings, anthropometrics and clinical observations will be recorded before participants are randomly allocated to receive salbutamol and hypertonic (3%) saline via either VMN or JN four times per day for 30 hours. During this period, measurements will include:

Neural respiratory drive (via parasternal EMG) Carbon dioxide levels (via forehead probe) Breathlessness and sputum burden (using numerical scales) 24-hour sputum volume with samples for bacterial/viral analyses

Following a 24-hour washout period, participants will receive salbutamol and hypertonic saline via the alternative nebuliser type for 30 hours, with identical data collection.

Inclusion Criteria:

• Patients receiving long-term tracheostomy ventilation as inpatients of the Lane Fox Respiratory Service at Guy's and St Thomas' NHS Foundation Trust
• Requiring prolonged mechanical ventilation for at least 6 hours per day for at least 21 days
• Has a cuffed tracheostomy in situ
• Aged 18-80 years old
• Receiving normal (0.9%) saline or hypertonic saline nebulisation at the time of enrolment into the study
• Requiring and tolerating tracheal suctioning for secretion management
• Able to communicate symptom burden to the research team
• Able to give informed consent for participation in the study
• Clinical stability, with no requirement for changes in ventilatory support, as assessed by the responsible clinician for at least 48 hours prior to enrolment in study

Exclusion Criteria:

• Severe, non-respiratory organ dysfunction including, but not limited to:

  • Congestive cardiac failure
  • Cardiac arrhythmia
  • End-stage malignancy
  • End-stage renal failure

• Acute pulmonary pathology requiring emergency treatment including, but not limited to:

  • Ventilator associated pneumonia at the time of screening
  • Pneumothorax
  • Pulmonary embolism

• Severe cognitive impairment

• Psychosocial factors that would preclude completion of the study protocol

• Previous intolerance of aerosolised hypertonic 3% saline or nebulised salbutamol

VMN and JN are easily distinguishable due to both their visible and audible signatures. It is therefore not feasible to blind the patient to the delivered intervention. The mode of nebulisation will be known to both the investigator and participant, and the absence of masking is acknowledged to be a potential source of bias. NRD and spirometry analysis will be masked as off-line analysis.