- NEGATIVE EXTRATHORACIC PRESSURE VENTILATION IN INFANTS AND YOUNG CHILDREN WITH CCHS
- Hans Hartmann, MD, Martin Samuels, MD, Jane Noyes, RSCN, M.Sc, and David Southall, MD, FRCP
- The first description of a negative pressure respirator was given in 1832 by John Dalziel, a Scottish physician. VNEP has since been widely used in the treatment of respiratory failure in both infants and adults. Until recently, there were few reports on its successful use in infants with CCHS. The use of VNEP has been limited by poor access to patients and poor skin protection provided by negative pressure respirators. In addition, upper airway obstruction may accompany hypoventilation in CCHS. Olson et al. demonstrated a failure of the normal splinting and dilating activity of the pharyngeal musculature that immediately precedes each inspiratory effort, keeping the upper airway open and allowing air to enter the trachea and lung. Following publication of our first clinical observations with VNEP in patients with CCHS, we now report our results in 13 patients.
- MATERIALS AND METHODS The 13 infants and children (7 boys) with CCHS were referred to North Staffordshire Hospital, UK, or Hanover Medical School, Germany. Eleven patients were diagnosed at an age of 10-150 days (median 21 days). Two patients presented with late onset central hypoventilation at 9 and 24 months, respectively. All had been ventilator dependent for 15 days to 52 months (median, 56 days) before noninvasive ventilation was started. Three children had a tracheostomy. One infant suffered from HSCR, and two had epilepsy. One child was severely mentally retarded, deaf, and blind.
- METHODS Diagnosis of CCHS was based on physiological recordings demonstrating hypoventilation exclusively during sleep with a rise of TcPCO2 above 8 kPa and hypoxemia, defined either as an inability to maintain baseline SaO2 measured by a validated pulse oximeter >96% when in quiet sleep or the occurrence of desaturation to <80% for more than 4 seconds. Negative pressure was applied using a Perspex chamber which is made virtually airtight by a latex seal around the nec. Routine access by the caretaker occurs via two portholes on each side of the chamber. These are fitted with elastic sleeves allowing patient access without loss of pressure. Negative pressure is generated by an electric fan suction unit and monitored by a pressure monitor with an alarm system. All children referred on endotracheal ventilation were extubated and placed on intermittent VNEP at a rate of 20-22 breaths/min, with peak inspiratory pressures of -30 to -40 cmH2O. Rate and pressure were subsequently adjusted to maintain and SaO2 of >96% and a TcPCO2 of 5-9 kPa. Nasal mask ventilation was provided with a Nippy ventilator through a nasal mask or pillows when negative pressure ventilation resulted in upper airway collapse. Inspiratory pressures of 16-24 cmH2O and rates of 16039 breaths/min were used. Transcutaneous oxygen tensions were always monitored and also served as alarms. During the first year of life and whenever the children were ill, TcPCO2 and SaO2 were also monitored during sleep.
- RESULTS We established VNEP in all ten patients without tracheostomy and in one with a tracheostomy. Peak pressures required for adequate ventilation were between -24 and - 40 cmH2O, with the highest pressure required in the oldest patient. Additional respiratory support was at times required in most: ten patients required additional inspired oxygen, initially both during wakefulness and when asleep. Three patients required additional inspired oxygen after age 1 year. Upper airway obstruction had to be treated with nasal continuous positive airway pressure in 6 patients, and mostly ocurred during the first year of life and during respiratory tract infections. Four patients had to be intubated for periods of 4-21 days during respiratory tract infections. From the start of treatment parents were included in the care and training; this took 1.5-16 months(median 5 months). In two patients with tracheostomy, decannulation and trail of VNEP at 29 and 52 months failed. These patients had severe tracheomalacia, and one has undergone laser therapy for a tracheal stenosis. The latter patient is scheduled to undergo an additional trial of nasal mask ventilation. The median duration of treatment with VNEP was 27 months. Five of our patients are treated with VNEP in their homes(VNEP applied for 13-86 months). Five patients have been transferred to positive pressure nasal mask ventilation at ages between 1.8 and 96 months (median 30 months) after treatment with VNEP for 0.5-59 months. In one child with late onset hypoventilation, an attempt to establish nasal mask IPPV was unsuccessful at the age of 34 months and VNEP was begun subsequently. In one child, hypoventilation improved spontaneously, and he has not required respiratory support since he was 28 months old. Hypoventilation termporarily improved in a second child; she was weaned off VNEP at 5 months but became ventilator dependent again 11 months later. No patient had a major respiratory crisis while being treated with VNEP. As an essential part of patient care, psychosocial development has been assessed regularly. Four of the 11 patients treated with VNEP show mild developmental delay, and 3 have delayed speech development. One child is severly mentally handicapped. Of the two patients treated with IPPV, one shows developmental delay and speech development is impaired in both. In 1993, the families of six children (four of whom were treated with VNEP) responded to a questionnaire regarding the acceptability of home ventilation with this technique. Parents estimated that between 4 and 24 hours a day were spent taking care of their child. The greatest advantage of noninvasive ventilation was the ability to treat the child normally during the day. The bulkiness of the system was considered the biggest disadvantage of VNEP. Parents of both children treated with IPPV wanted efforts to wean their children to noninvasive ventilation to continue.
- DISCUSSION Most patients with CCHS are treated with IPPV via a tracheostomy. In patients with hypoventilation during wakefulness, a combination of IPPV at night and pacing of the phrenic nerve during the day has been suggested as the most appropriate treatment since it increases patient mobility. In patients with sleep-related hypoventilation alone, noninvasive ventilation may be an alternative to IPPV via a tracheostomy since complications related to the tracheostomy such as increased risk of infection, lung damage, and sudden and unexpected death may be avoided. IPPV via a nasal mask requires cooperation of the patient and is difficult to establish in infancy. VNEP requires less cooperation, it could be established in all infants and young children without tracheostomy, and it was safe. Careful training of parents and caregivers and monitoring of oxygenation during sleep must be part of the care of any patient with CCHS.
NON-INVASIVE VENTILATION
Home Positive Pressure Ventilation in CCHS:
(Robert C. Beckerman, MD) Exerpts from the First International Symposium on CCHS 1996)
CCHS is a disorder that usually presents during the neonatal period. Infants who have CCHS uniformly require ventilatory support because the automatic control of breathing is lacking. Although the ventilatory control defect is most severe during deep quiet sleep, ventilatory impairment also occurs in active sleep and awake states. During the neonatal period, some form of constant ventilatory support is necessary to support life in infants with CCHS. The defect in ventilatory control is lifelong, however, and ventilatory support is therefore needed for the infant's care outside the hospital, preferably in the home. To date, most centers that provide long-term home care for children with CCHS have employed positive pressure ventilation through a permanent tracheotomy. Experience with alternative techniques of ventilatory support in children with CCHS is also available and is discussed by others in this symposium. Therefore, I will only summarize the reported experience with long-term positive pressure ventilation through a tracheotomy in CCHS. Infants and children with CCHS have been discharged from hospital care and sent home or to extended care facilities for more than 20 years. In the late 1970s to early 1980s, the morbidity and mortality rates were high. There were 13 reported deaths in 54 home ventilatory patients. Seizures and cor pulmonale secondary to acute and chronic hypoxia and hypercapnia were also frequently reported. It was suggested that persistent alveolar hypoventilation predisposed to these latter complications. Additional complications included recurring pneumonia, tracheostomy associated granulomas, growth retardation, generalized hypotonia, and psychomotor retardation. The reported high morbidity and mortality probably reflected a general lack of experience, technical deficiencies of ventilators, selection of high-risk patients, and family-home adjustment problems in a group of children who were totally ventilator dependent, at least during sleep. Gilgoff and co-authors recommended hyperventilating CCHS patients during sleep to PCO2 near 30 mmHg and maintaining normal oxygen saturation values to compensate for hypoventilation during wakefulness and intercurrent illness. Despite advancements in home ventilation technology and in our understanding of the pathophysiology of CCHS, it is still necessary to do periodic assessments of adequacy of sleeping and awake ventilation. To minimize the long-term complications of CCHS, we recommend admitting the patient at least annually for in-hospital study of cardiopulmonary function. During that visit, which may be a simple overnight stay or may span several days, awake and asleep ventilation on and off the ventilator are usually evaluated. In addition, echocardiography is performed to assess cardiac function and pulmonary artery pressure. Patients who have a permanent tracheotomy should also have airway endoscopy to evaluate the tracheobronchial tree for granulation tissue, chronic infection, aspiration, and the presence of malacia. Effective case management of such a complicated disease also requires anticipatory evaluation of non-cardiopulmonary aspects of CCHS such as developmental progress, speech, language, and hearing, as well as ongoing review of care-givers' stress. The follow-up of children with CCHS is best accomplished by a multi-disciplinary medical support team that not only interacts with the patient and family but also communicates with community home health providers, primary care physicians, and teachers. In reviewing the published experiences of home positive pressure ventilation, in sharing information with other pediatric home ventilator programs, and in listening to CCHS patients and their parents for more than 15 years, it becomes apparent that other less invasive techniques of ventilation may be potentially advantageous for CCHS management at home. However, most of the currently published experience using long- term domiciliary nasal mask positive pressure ventilation, nasal mask bi-level positive airway pressure, and intermittent negative pressure ventilation is relevant to children and adults with chronic respiratory insufficiency secondary to chronic obstructive lung disease, cystic fibrosis, muscular dystrophies, and spinal muscular atrophy. On the other hand, children with CCHS who are totally ventilator dependent during sleep may be severely impaired or may die if they are not ventilated effectively. Some reports suggest that both intermittent positive pressure delivered by nasal mask and intermittent negative pressure ventilation without tracheotomy may be effective alternatives to positive pressure ventilation through a tracheotomy in children with CCHS. Most parents who have school-aged children with CCHS have cared for a child who has been dependent on a tracheotomy and ventilator for their entire lives; they wish to move toward that "light at the end of the tunnel," i.e., tracheotomy decannulation. Although alternative methods of home ventilation may eventually offer adequate noctural ventilation without the need for a tracheotomy, such methods must be critically evaluated and compared against the gold standard of positive pressure ventilation through a tracheotomy.
Angela-Marie (IPPV) and Kristen (VNEP)-Porta-lung
Angela-Marie (IPPV), and Kristen (Hyak with Chest Cairass)
Dr. T. Rice (Dir. Critical Care, Ped. Pulmonologist, Trach/Vent.Cl.-Childrens Hospital of Wisconsin) and Angela-Marie at the National CCHS Conferences in Nashville-June/98