Nocturnal assisted ventilation using bilevel positive airway pressure: the effect of expiratory positive airway pressure

179

122

Mouth leak is common during nasal ventilatory assistance, but its effects on ventilatory support and on sleep architecture are unknown. The acute effect of sealing the mouth on sleep architecture and transcutaneous carbon dioxide tension (Ptc,CO 2 ) was tested in 9 patients (7 hypercapnic) on longterm nasal bilevel ventilation with symptomatic mouth leak.Patients slept with nasal bilevel ventilation at their usual settings on two nights in random order. On one night, the mouth was taped closed. Nocturnal nasal bilevel ventilatory support has become an important and successful therapy for respiratory failure during sleep [1±3]. At present, nasal masks are more common than mouthpieces, mouth-nose masks or full face masks (perhaps because of issues related to comfort, fit and deadspace) but a major practical problem is escape of air via the mouth, as has been well documented for nasal continuous positive airway pressure (CPAP) [4,5].In the only study to date to directly measure the effect of mouth leaks on effectiveness of ventilatory support, CAR-REY et al.[6] investigated the effect of voluntary mouth opening on diaphragm electromyogram (EMG) activity during awake nasal intermittent positive pressure ventilation in 5 subjects. With the mouth closed, diaphragm EMG dropped to 15% of unassisted control, but with the mouth open, returned to 98% of unassisted control, implying complete loss of ventilatory support.Mouth leak is ubiquitous during noninvasive ventilatory support in sleep. BACH et al. [7] demonstrated that during nasal intermittent positive pressure ventilation (NIPPV), severe leak (>33% of tidal volume escaping) was present for a median of 55% of sleep time, and was associated with 7.5 desaturations (of at least 4%) per hour of sleep.MEYER et al. [8] found severe mouth leak during most of sleep time and 100% of slow wave sleep.Mouth leak could lead to severe sleep fragmentation, either directly via airway irritation, or indirectly via a reduction in effectiveness of ventilation as discussed above. In the study by BACH et al. [7], there were a total of 34 arousals . h -1 and 74% of desaturations were terminated by either an arousal or a lightening of sleep stage. The authors concluded that leak was reducing ventilatory effectiveness and causing desaturation, and that arousal reversed the leak and desaturation. Similarly, in the study of MEYER et al. [8] there were 46 arousals . h -1 in stages I-II nonrapid eye movement (NREM) sleep, associated in time with mouth leak. However, association in time does not establish causality, and it is not known whether preventing the mouth leak would improve sleep quality.The purpose of the present paper was to directly assess the effect of mouth leak on sleep architecture and transcutaneous carbon dioxide tension (Ptc,CO 2 ) during nasal bilevel ventilatory support, by preventing the leak. To do this, the authors measured the first-night effect of taping the mouth closed, on sleep architecture and Ptc,CO 2 in patients already on long-term nasal bilevel venti...

Section: Effectiveness Of Ventilatory Supportmentioning

confidence: 90%

Effect of mouth leak on effectiveness of nasal bilevel ventilatory assistance and sleep architecture

Teschler¹,

Stampa²,

Ragette³

et al. 1999

179

122

“…During the trial they had EPAP set to the lowest limit (4 cmH 2 O (0.39 kPa)). However, an EPAP of 5 cmH 2 O (0.49 kPa) has been shown to be beneficial in this patient group [20].…”

Section: Limitations Of the Studymentioning

confidence: 99%

Autotitratingversusstandard noninvasive ventilation: a randomised crossover trial

Jaye¹,

Chatwin²,

Dayer³

et al. 2009

The aim of the present study was to compare the efficacy of automatic titration of noninvasive ventilation (NIV) with conventional NIV in stable neuromuscular and chest wall disorder patients established on long-term ventilatory support.In total, 20 neuromuscular and chest wall disease patients with nocturnal hypoventilation treated with long-term NIV completed a randomised crossover trial comparing two noninvasive pressure support ventilators: a standard bilevel ventilator (VPAP III) and a novel autotitrating bilevel ventilator (AutoVPAP). Baseline physiological measurements, overnight polysomnography and Holter monitoring were repeated at the end of each 1-month treatment period.Nocturnal oxygenation was comparable between the autotitrating device and standard ventilator, as were sleep efficiency, arousals and heart rate variability. However, there was a small significant increase in mean overnight transcutaneous carbon dioxide tension (median (interquartile range) 7.2 (6.7-7.7) versus 6.7 (6.1-7.0) kPa) and a decrease in percentage stage 1 sleep (mean¡SD 16¡9 versus 19¡10%) on autotitrating NIV compared with conventional NIV.Autotitrating noninvasive ventilation using AutoVPAP produced comparable control of nocturnal oxygenation to standard nonivasive ventilation, without compromising sleep quality in stable neuromuscular and chest wall disease patients requiring long-term ventilatory support for nocturnal hypoventilation.

“…A peak inspiratory pressure of 20-25 cmH 2 O is often required with pressure-preset ventilation and an inspiratory time of 0.8-1 s with an expiratory time of y2 s. A sensitive triggering system with a short response time is required in view of the rapid respiratory frequency that is adopted by these subjects. Positive end expiratory pressure is not essential, apart from in some bilevel pressure-support systems in which it is mandatory to flush the dead space, but may be useful at a level of 2-4 cmH 2 O [8]. Supplemental oxygen is rarely required unless the oxygen tension in arterial blood (Pa,O 2 ) cannot be normalised.…”

Section: Types Of Ventilatory Supportmentioning

confidence: 99%

Noninvasive ventilation for chest wall and neuromuscular disorders

Shneerson¹,

Simonds²

2002

164

Neuromuscular and chest wall disorders are individually uncommon but together form an important group of conditions that can lead to chronic ventilatory failure. This is best recognised in scoliosis, kyphosis, following a thoracoplasty, in muscular dystrophies, such as Duchenne muscular dystrophy (DMD), and myotonic dystrophy, after poliomyelitis and with motor neurone disease (amyotrophic lateral sclerosis).If bulbar function is impaired, tracheostomy ventilation may be required, but in other situations, noninvasive ventilation is preferable. Positive pressure techniques using nasal and face masks are usually the first choice, but negative pressure ventilation is an alternative.There are no randomised-controlled trials regarding the indications for initiating noninvasive ventilation, but this is usually provided if there are symptoms due to nocturnal hypoventilation or right heart failure in the presence of a raised carbon dioxide tension in arterial blood (Pa,CO2) either at night or, more usually, in the daytime as well. There is no evidence that “prophylactic” ventilatory support is of benefit if this is provided before ventilatory failure has appeared. Careful selection of patients is required, especially in the presence of progressive neuromuscular disorders such as DMD and motor neurone disease.There are no randomised-controlled trials concerning the outcome of noninvasive ventilation in these conditions, but studies have shown an improved quality of life, physical activity and haemodynamics, normalisation of blood gases and slight improvement in other physiological measures, such as the vital capacity and maximal mouth pressures. Survival in chest wall disorders is ∼90% at 1 yr and 80% at 5 yrs, and similar figures have been obtained in nonprogressive neuromuscular conditions. If, however, the underlying disorder is deteriorating, particularly if it involves the bulbar muscles, it may limit survival despite the provision of adequate noninvasive ventilatory support.