Long-term mechanical ventilation
In Norway, intensive care doctors have traditionally employed invasive mechanical ventilation. In a number of institutions today, pulmonary specialists monitor patients with both invasive and non-invasive mechanical ventilation. Long-term mechanical ventilation subsequent to SCI is indicated where there is restrictive ventilation reduction (vital capacity 60 – 50 %) and hypoventilation (
pCO₂ > 6 kPa). Hypoventilation may develop several years after the SCI (Table 2), with recurrent lower airway infections, atelectasis, poor cough function, poor sleep quality and dyspnoea. The patient then needs long-term mechanical ventilation around the clock or during parts of the day. Non-invasive mechanical ventilation has a number of advantages over invasive mechanical ventilation: better quality of life and speech function, fewer infections, and cost savings (29). BiPAP (bilevel positive airway pressure) does not make air-stacking possible, and patients must have other methods of mobilising secretion. Today’s ventilators can be programmed in both pressure- and volume-controlled mode. This is practical in non-invasive mechanical ventilation if the patient alternates between using a mask connection at night and a mouthpiece during the day, or if the patient has a tracheostomy tube with a cuffless cannula during the day and a cannula with a cuff at night.
Significance of the injury level for acute and chronic respiratory problems. + = always, (+) = varying degree, = never
Affected respiration muscles
Most frequently permanent invasive mechanical ventilation
Most patients are weaned from the ventilator.Non-invasive ventilation is often relevant during course
50 % need mechanical ventilation in acute phase with ASIA-A (8).Almost 100 % are weaned.Non-invasive ventilation may be relevant in a long-term perspective.
A high spinal cord injury (C1-C3) entails invasive mechanical ventilation (Table 2). Volume-controlled mechanical ventilation has traditionally been the first choice for adult patients with a tracheotomy. It may be simpler to achieve sufficient air leakage for speech function with volume-controlled rather than pressure-controlled mechanical ventilation
(30). However, other studies show improved speech function with pressure-controlled mechanical ventilation because leakage compensation results in a stronger flow of air past the vocal cords (30). In addition, pressure-controlled mechanical ventilation eliminates the challenge of compensating for the leakage associated with cuffless ventilation. The faculty of speech is of great importance for the quality of life of these patients, and depends on both cannula adjustment and ventilator settings. The diameter of the tracheal cannula must be adjusted to the desired degree of leakage. The best results are yielded by a long inspiration time with moderate air flow and the use of positive end-expiratory pressure (PEEP) that ensures sufficient air leakage past the vocal cords during expiration, providing constant vocal volume during the entire respiratory cycle (30).
A Cochrane article concludes that there are no major differences between using passive humidification (humidifier filter) and active humidification (heating elements and water vapour) in mechanical ventilation
(31). However, there may be a lesser risk of pneumonia and greater risk of cannula occlusion when a humidifier filter is used compared with active humidification (31). Experience shows that passive humidification is not effective enough with a cuffless cannula. Active humidification by adding water vapour to the respirator cycle is then necessary. The situation in Norway
The situation in Norway
The prevalence of spinal cord injuries in Hordaland and Sogn og Fjordane counties was 36.5 per 100 000 inhabitants in 2002; the proportion of men to women was 4.7 : 1
(12). In Norway, there will be 90 – 100 persons each year with traumatic SCI who need therapy and rehabilitation, and an additional 70 – 100 with non-traumatic spinal cord injuries (personal communication, Erik Sigurdsen, responsible for the Norwegian Spinal Cord Injury Registry). At the end of 2007, 23 SCI patients (16 men and 7 women) were receiving long-term mechanical ventilation in Norway (32). The number at the end of 2010 was 36 (25 men and 11 women), with an average age of 52. A total of seven patients had invasive mechanical ventilation; the remainder had non-invasive mechanical ventilation. Most of them lived in their own home or in a serviced housing unit. On the basis of the prevalence of spinal cord injuries (12), about 15 % of all patients with SCI in Norway have long-term mechanical ventilation. Lower airway infections in non-ventilated SCI patients entail a considerable risk of respiratory failure and death (13), and today’s use of long-term mechanical ventilation is probably too low. There may be many reasons for this. General practitioners, internal medicine specialists, neurologists, rehabilitation teams and pulmonary specialists often do not recognise that recurrent pneumonia and atelectasis are secondary to ventilation reduction and hypoventilation due to extrapulmonary restrictive disease; consequently their patients are not referred for pulmonary examination and follow-up. Pulmonary expertise in the field of long-term mechanical ventilation varies from hospital to hospital (32).