Ventilatory Assistance

Patients receiving IPPV represent a small fraction of the patients receiving domiciliary ventilation. In a recent European survey, they comprised 13% of those ventilated at home, representing 24%, 8%, and 5%, respectively, of patients with neuromuscular disease (NMD), parenchymal disease, and RTD, respectively (9). Selection and management of tracheostomy tubes for IPPV must maximize the patients ability to speak and swallow (7). 

The choice of size, shape, and composition of the tube should be individualized. Tracheostomy tubes and cannulae for home use are made of plastic or silicon. Silicone tubes are more flexible than PVC tubes and may offer a better fit. To allow for connection to the ventilator, the tube must extend at least 2 to 3 cm beyond the stoma, but should be situated no closer than 2 cm from the carina. The tube curvature should be such that the tube is in the center of the tracheal lumen rather than impinging on the tracheal wall—to avoid damage to the tracheal wall and to avoid problems with ventilation, comfort, and speech. 

Dependent upon the curvature, cuffed and cuffless tubes may have an inner cannula, which is either reusable or disposable. It can easily be removed for cleaning or if secretions block the airway. 

Fenestrated tubes are designed to allow increased airflow to the upper airway for vocalization, but they are too frequently incorrectly positioned and the fenestration may promote the growth of granulation tissue. An unfenestrated inner cannula must be inserted to ventilate and to suction the patient s airway. 

NIV is often an effective treatment for patients with acute respiratory failure, especially when secondary to exacerbation of chronic obstructive pulmonary disease (COPD) (24). NIV is also utilized for long-term ventilation (LTV) of patients with chronic respiratory failure due to thoracic restriction or NMD. It is used less frequently for COPD as there is only limited evidence of its long-term effectiveness in this condition (25). In stable patients, NIV is affected by the type of interface used (26). 

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Airway support and ventilatory assistance in patients with a depressed level of consciousness or airway compromise... 

Rey and coworkers78 reported methyltin intoxication in six chemical workers exposed to Me2SnCl2 and MesSnCI. After a latent period of 1 -3 days, the first symptoms occurred, including headache, tinnitus, deafness, impair of memory, disorientation, aggressiveness, psychotic behavior, syncope, loss of consciousness and, in the most severe cases, respiratory depression requiring ventilatory assistance. Increased tin excretion was detected in the urine of all patients, particularly those most ill. The patient with the highest tin levels died 12 days after the initial exposure. 

Emergency use Nalmefene is not the primary treatment for ventilatory failure. In most emergency settings, treatment with nalmefene should follow, not precede, the establishment of a patent airway, ventilatory assistance, administration of oxygen, and establishment of circulatory access. 

When overdosing occurs, gastric lavage is advised and an alkaline, high urine output state should be maintained (see Chapter 59 Management of the Poisoned Patient). Hyperthermia and electrolyte abnormalities should be treated. In severe toxic reactions, ventilatory assistance may be required. Sodium bicarbonate infusions may be employed to alkalinize the urine, which will increase the amount of salicylate excreted. 

A 42-year-old woman who presented with a change in mental status and rapidly decompensated into respiratory failure and required ventilatory assistance for 2 months had not taken an overdose—her lithium concentration had increased slowly (567). 

The treatment of acute alcohol intoxication is based on the severity of respiratory and CNS depression. Acute alcohol intoxication can be a medical emergency, and a number of young people die every year from this disorder. Patients who are comatose and who exhibit evidence of respiratory depression should be intubated to protect the airway and to provide ventilatory assistance. The stomach may be lavaged, but care must be taken to prevent pulmonary aspiration of the return flow. Since ethanol is freely miscible with water, ethanol can be removed from blood by hemodialysis. 

There are numerous mechanical devices, including sophisticated ventilators, that can be used to provide ventilatory assistance in an apneic casualty. None of these is available to the soldier or his buddy, and only a few—the mask-valve-bag venti-... 

In summary, spontaneous respiration will stop within several minutes after onset of effects caused by exposure to a lethal amount of nerve agent. Antidotes alone are relatively ineffective in restoring spontaneous respiration. Attempts at ventilation are hindered by the high resistance of constricted bron-chiolar muscles and by copious secretions, which may be thick and plug the bronchi. Ventilatory assistance may be required briefly (20-30 min) or for a much longer period. In several instances, assistance was required for 3 hours18,63 this seems to be the longest reported use of ventilation. 

First, medical personnel must provide oxygenation and administer atropine by a technique that ensures it will be carried to the heart and lungs. If ventilatory assistance is not immediately available, the best treatment is to administer the contents of three MARK I kits and diazepam. If ventilatory assistance will be forthcoming within minutes, the contents of the three MARK I kits should be administered whether the circulation is intact or not. When there is no chance of rapid ventilatory assistance, little is gained by MARK I therapy, but an attempt at treatment should be made anyway. 

If the casualty is not breathing because of nerve agent effects, attempting to provide ventilatory assistance might preclude the immediate care of a severe wound or other assistance in the contaminated area. If ventilation is marginal and the wound alone would classify the casualty as immediate, the time and effort required to stabilize ventilation might preclude timely wound care. The dual requirements might require more care providers than are available. 

Dasgupta and colleagues (1998) treated 20 patients with neoplastic tracheobronchial strictures with uncovered Wallstents. Stents were successfully deployed in all patients and airway patency was restored. Four patients were successfully weaned after stent insertion, five were receiving mechanical ventilatory assistance, while the remaining died from unrelated causes while receiving mechanical ventilatory assistance. No deaths occurred from stent failure or stent related complications. 

The prevalence of home ventilation in different countries is based on differences in the availability of medical care as weU as on the various models of home care. Contrasts between the US and French systems illustrate this point. The majority of patients receiving LTMV at home have been transitioned from the acute care or ICU environment. In France, such patients are typically offered ventilatory assistance on an elective basis, when still relatively stable, although gradually deteriorating. Elective initiation of ventilatory support among less critically ill patients is a major reason fOT the higher use of home ventilation in France. If the French approach was applied in the United Stales, there would be more than 10,000 cases of LTMV in the United States (10). 

The most complete European data on the use of HMV has been reported recently as the Eurovent study, a survey of long-term ventilator use conducted in 16 countries (15). In this survey, home ventilation was defined as ventilatory assistance for three months or more. Those receiving other forms of ventilation, such as rocking beds, negative-pressure ventilation, and phrenic nerve stimulation, were included. A total of 483 surveys were sent to the centers prescribing HMV in the 16 countries, with 329 centers (68%) responding. The numbers of patients and prevalence rates were estimated for each country. As noted in Table 3, there was a wide variation in the prevalence of HMV in Europe, ranging from 0.1/ 100,000 population in Poland to 17/100,000 in France. The survey identified a total of 21,526 VAIs and estimated the prevalence of HMV to be 6.6/100,000 population in Europe. 

The number of VAIs has fluctuated from decade to decade. As the need for LTMV for polio patients declined, the number of patients with spinal cord injuries or progressive neuromuscular disease (NMD) increased due to better acute care. Therefore, the number of patients administered LTMV has progressively increased, due both to advances in medical care and to the more widespread application of invasive mechanical ventilation in the acute setting. The increasing number of VAIs can be documented by comparing surveys performed in the last two decades. Regional surveys carried out in Minnesota, United States, in 1986 and 1992, documented that the prevalence of ventilatory assistance rose from 2.4/100,000 in 1986 to 4.9/100,000 in 1992 (2). Extrapolation of these data would suggest that in the United States, the potential number of VAIs rose from 5777 in 1986 to 12,279 in 1992 (4). 

Robert D, Vitacca M. Ventilatory assistance at home. In Donner CF, Ambrosino N, Goldstein R, eds. Pulmonary Rehabilitation Efficacy and Scientific Basis. London Arnold, 2005 343-352. 

Although a Cochrane meta-analysis (73) does not recommend the institution of NIV for symptomatic sleep hypopneas, a prospective study from Mellies et al. (74) and a randomized controlled trial by Ward et al. (72) support the indication of NIV for patients with NMD and nocturnal hypercapnia. The consensus conference of the American College of Chest Physicians on MV beyond the ICU recommended that patients who develop symptomatic nocturnal hypercapnia, even in the absence of daytime hypercapnia, are candidates for long-term ventilatory assistance (75). 

Ferguson GT, Gilmartin M. CO2 rebreathing during BiPAP ventilatory assistance. Am J Respir Crit Care Med 1995 151 1126-1135. 

Teschler H, Stampa J, Ragette R, et al. Effect of mouth leak on effectiveness of nasal bilevel ventilatory assistance and sleep architecture. Eur Respir J 1999 14 1251-1257. 

Claman OM, Piper A, Sanders MA, et al. Nocturnal noninvasive positive pressure ventilatory assistance. Chest 1996 110 1581-1588. 

During the 1970s, more patients with respiratory failure due to neuromuscular disorders and chest wall deformities received long-term ventilatory assistance at home, either via tracheostomy or body ventilators, which provided effective nocturnal noninvasive ventilation (NIV) (5,6). In the 1970s, the development of home respiratory therapy companies improved support for home mechanical ventilation (HMV). Respiratory therapists could now set up ventilatory equipment, educate the patient and caregivers about using the equipment, and be available to deal with problems. 

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