Breathing irregularity

The immediate clinical strategy is to establish the cardiorespiratory phenotype of the breathing dysrhythmia. Assessing this requires an appropriately set up neurophysiology department . It is very important to understand that there is predominantly a disorder of the control mechanisms of carbon dioxide exhalation in RTT including both respiratory alkalosis and respiratory acidosis. The management strategies following identification of any of the three types of breathers are as follows:

Forceful breathers tend to have fixed low levels of pCO₂ (Chronic Respiratory alkalosis). To interrupt an episode of forceful breathing, we recommend first re-breathing in a 5L bag attached to a tightly fitting facial mask. Long-term weaning from the chronic respiratory alkalosis requires Carbogen treatment (5% CO₂ in oxygen mixture). Treatment by controlling the tidal volume with Bi-level Positive Airway Pressure (BiPAP system) is theoretically possible, but some people with RTT may not tolerate the masks used to administer this treatment. Treatments must be monitored continuously and we recommend transcutaneous measurement of blood gases. Levels of carbon dioxide determine the end-points of treatments. We emphasise that due to the reset of the central respiratory chemoreceptors, the operational levels of pCO₂ for stable breathing is very variable in RTT and has to be establish by trial and error during treatment. The long-term aim is to move the operational pCO₂ level towards normal between 5.2-5.9 kPA (39-44 mmHg). The nutritional implications of this cardiorespiratory phenotype are summarised below.

Feeble breathers tend to have fixed higher levels of pCO₂ (Chronic Respiratory acidosis) due to long-term inadequate ventilation. Stimulation of breathing is important in these people. Physical activation during personal contact is useful, but is short-lived. We recommend Theophylline by mouth as a first choice respiratory stimulant in Feeble Breathers. The non-invasive BiPAP system should also be considered, although our clinical experience is limited. The rationale behind using BiPAP is to increase the tidal volume mechanically at night only and this should be sufficient for daytime maintenance. The end-point of treatment is established by monitoring breathing rate and rhythm and transcutaneous pCO₂ . The long-term aim is to achieve a normal breathing rhythm at or near normal operational level of pCO₂. The RTT population with this cardiorespiratory phenotype often have idiosyncratic sensitivity to opiates and other respiratory depressants, all of which must be avoided. Idiosyncrasy to diazepam has also been reported in Feeble Breathers. Anaesthetists should be aware of the hypercapnoea and sensitivity to respiratory depressants in this population of RTT. The high operational pCO₂ in these patients must be considered if spontaneous breathing fails during weaning from artificial ventilation in intensive care.

Apneustic breathers accumulate carbon dioxide due to the delayed and inadequate expirations. We recommend Buspirone by mouth as the drug of first choice and this was shown to be effective against apneusis. Treatment using the BiPAP system in spontaneous time mode with backup frequency is theoretically possible, but has the shortcomings mentioned above. The short and long-term treatment aims are as for Feeble Breathers. This is the only cardiorespiratory phenotype shown to respond to Buspirone. The chronic hypercapnoea and high operational pCO₂ in this cardiorepiratory phenotype breathers has complications in anaesthesia similar to that of Feeble Breathers.                                                                                                                                                            

Valsalva’s manoeuvre is a common complication of breathing dysrhythmia in RTT and has powerful excitatory effects on the autonomic nervous system and brainstem functions leading to recognisable clinical features. All three cardiorespiratory phenotypes are affected. This is not a bedside diagnosis. The typical and diagnostic heart rate and blood pressure changes can only be confirmed during autonomic monitoring in appropriate neurophysiological set up. This complication often leads to visible clinical deterioration of the well being of the person with RTT, particularly the Forceful Breathers. All medical and non-medical carers of persons with RTT should be aware of this.
Autonomic disturbance caused by these manoeuvres mimic epileptic seizures. Therefore, early and correct diagnosis is essential to avoid unnecessary treatment with anti-epileptic drugs that are ineffective against the autonomic paroxysms. The nutritional implications of Valsalva’s manoeuvre are summarised below.