Monitoring at Home
Optimal monitoring strategies for the home environment continue to be debated. In-build ventilator alarms are often inadequate and insensitive to the small tidal volumes seen in paediatric patients, necessitating additional external monitoring devices to minimise risk. Commonly, centres will opt to provide pulse oximeters at home for children on invasive mechanical ventilation. Others have used cardiorespiratory monitors, end-tidal CO2 monitors or rely on direct observation by a nurse 24hr a day. Both The American Thoracic Society and Canadian Thoracic Society clinical practice guideline provide an excellent summary of the rationale for pulse oximetry as the preferred monitoring method for this population of children over other options.(14, 16) However, it is also important to remember that continuous oximetry monitoring may be difficult to undertake in some children and has the potential to falsely alarm or even falsely reassure parents and carers. Therefore, the data needs to be interpreted in the context of the clinical situation and by those with the experience to determine its reliability.
In recent times, the role of home carbon-dioxide monitoring in children on invasive ventilation has been raised, recognising that this is an important measure to gauge effectiveness of ventilation. Non-invasive capnographs and capnometers that can measure either end-tidal carbon dioxide (EtCO2) or transcutaneous CO2(TCM) have become increasingly available and are attractive for use in children, who often cannot tolerate regular invasive blood gas monitoring.(24) Foster et al. recently evaluated the potential of a portable endotracheal capnograph (EMMATM Capnograph) for measurements of EtCO2 at home in children on home invasive ventilation. Overall, this device was demonstrated to show promise for spot-checking carbon dioxide levels in this population of children, but it has not been evaluated for continuous home monitoring purposes.(24) Similarly, there is little evidence for the use of ambulatory transcutaneous carbon dioxide monitoring (TCM) in children on home invasive ventilation. One study has been undertaken in children with neuromuscular disease to determine if ambulatory TCM monitoring could be used for early screening and diagnosis or nocturnal hypoventilation.(25) However, this study did not demonstrate sufficient accuracy for this tool to be used for this purpose, despite patient preference for this option over in-lab polysomnography. Therefore, at present further research is required before non-invasive CO2 monitoring of any type can be recommended as part of routine home continuous routine monitoring.(24)
The exception is in congenital central hypoventilation syndrome, a genetic condition where there is absent or abnormally reduced ventilatory responses to hypercapnia and hypoxia, in the context of systemic autonomic dysfunction. These patients fail to display the typical responses to hypoxia and/or hypercapnia such as increases in respiratory rate or effort. Here, home CO2 monitoring can identify early hypoventilation in times of illness or stress. Which in turn enables parents to institute a predetermined escalation plan such as a ventilation ladder or a second program on the ventilator to better reflect the increasing need for respiratory support. This can avert attendance or admission to hospital. Furthermore, many emergency departments do not have ready routine access to non-invasive CO2 monitoring relying on CO2assessments taken by capillary or arterial blood gases. The pain/ arousal generated by these procedures often alter sleep state and breathing, rendering results potentially less reliable. There has thus been a movement towards providing these patients with home CO2 monitoring, albeit funding can be an issue.
Follow up
It is important for children receiving home ventilation to receive regular follow up at specialist respiratory centres with experience in looking after these children. This may be in the form of an overnight hospital stay, an out-patient visit, a home visit, via telemonitoring or telemedicine, or a combination thereof. Clinical evaluation, nocturnal oximetry and capnography monitoring and/or poly(somno)graphy and analysis of ventilator download data are recommended as part of routine monitoring. Gas exchange, delivered pressure, tidal volumes, inspiratory: expiratory ratio, leak, residual respiratory events, and patient ventilator synchrony ideally should be assessed. Follow up should be provided by a multidisciplinary team, members of which include a pulmonologist, long term ventilation/ tracheostomy nurses, respiratory therapists, physiotherapists and ENT surgeon.