Recent advances in upstream medical therapies for neuromuscular disorders suggest that the best outcomes result from their administration in the pre-symptomatic, and perhaps, neonatal period. Currently available therapies, and many other therapies in the pipeline soon to be considered by the Food and Drug Administration, suggest the importance of avoiding potential life-threatening disease complications. There is evidence that this is almost always possible with the use of respiratory muscle aids to avoid pneumonias and respiratory failure, but these are currently little understood and rarely offered by the medical community. However, restoring neuromuscular function necessitates keeping the patient alive and well.
- Article type
Mechanical insufflationeexsufflation to facilitate ventilator weaning and possible decannulation for patients with encephalopathic conditions
Clinicians are often faced with apparently tracheostomy mechanical ventilation dependent (TMV), patients who are ventilator unweanable due to encephalopathic/upper motor neuron conditions, that hamper return to the community.
A protocol is suggested to wean these patients from mechanical ventilation and criteria offered for possible decannulation.
After excluding patients with severe muscle weakness due to neuromuscular diseases and high level spinal cord disorders, consecutive, apparently unweanable and unresponsive encephalopathic patients were to be weaned by a protocol that first normalized CO2 levels at full ventilatory support settings. Then, supplemental oxygen was discontinued so that ambient air baseline oxyhemoglobin saturation (O2 Sat) could be determined and subsequently be normalized by using mechanical insufflation–exsufflation (MIE), at 60–70 cmH2O pressures, via the tubes every 2 hours, with the tube cuffs inflated. Once ambient air O2 Sat levels remained normal, ambient air spontaneous, unassisted autonomous breathing “sprints” were initiated and continued until O2 Sat decreased below 95% with respiratory distress. Patients spontaneously moving over 300 mL of air into their lungs without pressure support had very good prognoses for rapid ventilator weaning. Patients were not returned to TMV irrespective of tachypnea. After the “sprint”, they were rested by using 1–3 hours of full ventilatory support before the next sprint. Sprints lengthened until being fully weaned. After weaning, potential decannulation was evaluated using MIE expiratory flows (MIE-EF) and O2 Sat.
O2 Sat normalized from the initial use of MIE via the tube for 7 of 13 patients then 4 weaned from the initial ambient air sprint. Weaning occurred in 4 days or less for 11 of 13. Despite continuous TMV dependence for 31 days to 15 months before the intervention, 7 weaned patients were successfully decannulated, 6 of the 7 with MIE-EF ≥ 190 L/m. All but 2 remained unresponsive, but 6 were discharged home to their families once decannulated.
Once primary ventilatory pump failure is excluded and lung disease improved to the extent that the ambient air O2 Sat can be normalized by using MIE via invasive airway tubes to clear airway secretions, encephalopathic patients can have sufficient muscle strength to wean from ventilatory support and possibly be decannulated if mechanically augmented cough flows exceed 190 L/m.
Supplemental O2 is often administered without knowledge of CO2 levels for patients with ventilatory pump failure (VPF). This can render oximetry ineffective as a gauge of alveolar ventilation, airway secretions, and lung disease. We have noted that diurnal hypoventilation with hypercapnia tends to be symptomatic when O2 saturation levels decrease below 95% and patients extend sleep noninvasive ventilatory support (NVS) into daytime hours. We also noted that with advancing age, less hypercapnia results in desaturation. This study was designed to explore oxyhemoglobin desaturations (O2 desats) as a function of age and hypercapnia for patients with VPF.
A retrospective analysis of 8933 consecutive patient visits for whom end-tidal CO2 and O2 sats were measured. O2 sats < 95% at CO2 levels of 45, 50, and 60 cmH2O were correlated with 10 years age intervals to age 80.
Of 8933 visits, 8642 had complete data. Outcomes for CO2 levels > 50 cmH2O were the most significant including for visit-ages < 30 and ≥ 30 years. There was a statistically significant 4% decrease in the odds of O2 desat for every one-year increase in age to age 30 (OR = 0.96, 95% CI = [0.93, 0.99], p = 0.02) and for visit-ages ≥ 30 a significant 30% increase in the odds of O2 desat for every 10-year increase in age (OR 1.3, 95% CI = [1.1, 1.6], p = 0.006). Relationship for ages ≥ 30 years were also significant for CO2 levels over 45 mmHg also. 40% of the time when CO2 was greater than 45 mmHg O2 sat was low.
This study demonstrated a significantly lower risk of O2 desat occurring at EtCO2 levels ≥ 50 mmHg for patients from 10 to 20 years of age than those younger than 10 and a significantly greater risk of O2 desat for 10 years intervals after age 20. Thus, with age, less hypercapnia results in desats and dyspnea with patients tending to extend NVS into daytime hours. This may be due to increases in physiological shunting, decreased pulmonary elasticity, and worsening ventilation/perfusion ratios with age.
An April 2010 consensus of clinicians from 22 centers in 18 countries reported 1,623 spinal muscular atrophy type 1, Duchenne muscular dystrophy, and amyotrophic lateral sclerosis noninvasive intermittent positive pressure ventilatory support users, of whom 760 developed continuous dependence that prolonged their survival by more than 3,000 patient-years without tracheostomies. Four of the centers routinely extubated unweanable patients with Duchenne muscular dystrophy, so that none of their more than 250 such patients has undergone tracheotomy. This article describes the manner in which this is accomplished; that is, the use of noninvasive inspiratory and expiratory muscle aids to prevent ventilatory failure and to permit the extubation and tracheostomy tube decannulation of patients with no autonomous ability to breathe (ie, who are "unweanable" from ventilator support). Noninvasive airway pressure aids can provide up to continuous ventilatory support for patients with little or no vital capacity and can provide for effective cough flows for patients with severely dysfunctional expiratory muscles.