Pulmonary function and sleep disordered breathing in patients with traumatic tetraplegia: a longitudinal study

[Respiratory and physical recovery in cervical spinal cord injury. Seventeen years' experience in a weaning and rehabilitation center: An observational study]

INTRODUCTION AND OBJECTIVES

Spinal cord injury (SCI) is a devastating entity that generates substantial disability. The outcome of respiratory and motor features has an impact in human and social well-being. We analyzed demographic characteristics, motor and respiratory outcomes, and determined equipment needs at discharge in a weaning and rehabilitation center.

MATERIAL AND METHOD

Observational, descriptive and retrospective study of medical records between January 2002 and December 2018. Tracheostomised cervical SCI patients with invasive mechanical ventilation were included. Forced vital capacity (upright and supine), maximal inspiratory and expiratory pressures, ASIA and Spinal Cord Independence MeasureIII (SCIMIII) were obtained.

RESULTS

Of 1603 patients, 3.5% had SCI, and 28 met the inclusion criteria. The most frequent level of injury was C4-C5 (17/28), 21/28 had ASIAA classification, and 19 showed no change in either the ASIA or the SCIM score. In all, 22/28 patients were weaned, while 15/28 were decannulated. Twenty four patients were discharged to home. The most relevant change in SCIMIII was in the 5th component of respiration and sphincter subscale, related to weaning and tracheostomy. At discharge, 23/24 patients needed both respiratory and motor aids.

CONCLUSIONS

The admission rate of SCI patients was low in our weaning and rehabilitation center, with almost all being admitted for traumatic causes. Severity remained unchanged in most ASIAA patients. Respiratory recovery was more clinically significant than recovery of motor function. Upon discharge, most of our patients had to be equipped with both respiratory and motor aids.

Noninvasive Respiratory Management of Spinal Cord Injury

Intubated ventilator-dependent patients with high-level spinal cord injury can be managed without tracheostomy tubes provided that they have sufficient cognition to cooperate and that any required surgical procedures are completed and they are medically stable. Intubation for a month or more than extubation to continuous noninvasive ventilatory support (NVS) can be safer long term than resort to tracheotomy. Noninvasive ventilation (NIV) is not conventionally being used for ventilatory support. Noninvasive interfaces include mouthpieces, nasal and oronasal interfaces, and intermittent abdominal pressure ventilators. NIV/NVS should never been used without consideration of mechanical insufflation-exsufflation for airway secretion clearance.

Evidence-based respiratory management strategies required to prevent complications and improve outcome in acute spinal cord injury patients

Spinal injuries without neurological damage have little effects on respiratory function unless associated with injury to the chest wall. Early verticalisation or mobilisation of these patients is safe and likely to improve vital capacity. Spinal injury with cord damage has a profound effect on the mechanics of respiration and on respiratory function particularly in cervical cord injuries. Around 40% of spinal cord injuries occur in the cervical spine, a trend that is steadily increasing, with respiratory causes being responsible for death in over 20% of individuals. Loss of lung volumes and relative hypoxemia contribute to global hypoxaemia, exacerbating cord ischaemia in the acute period. Respiratory compromise results in the loss of muscle strength generation capacity and reduced lung volumes and in particular vital capacity, of up to 70%, ineffective cough and secretion clearance abilities; reductions in both lung and chest wall compliance and an additional oxygen cost of breathing due to changes in respiratory mechanics, with obstructive sleep apnoea evident in over 50% of acute tetraplegics. While some countries have specialist spinal centres to manage such catastrophic trauma with a demonstrable improvement in health outcomes attributed to their contribution, many individuals are initially admitted to local hospitals where healthcare professionals are less likely to fully appreciate the significant and continued vulnerabilities of such individuals. This article aims to provide a basic understanding of the causes and identification of the main principles of the respiratory management strategies required to maintain pulmonary health for cervical spinal cord injury patients during the initial and early post trauma phase.

Simplified Approach to Diagnosing Sleep-Disordered Breathing and Nocturnal Hypercapnia in Individuals With Spinal Cord Injury

OBJECTIVE

To evaluate a strategy of home-based testing to diagnose sleep-disordered breathing and nocturnal hypercapnia in individuals with spinal cord injury (SCI).

DESIGN

Case series.

SETTING

Referral center.

PARTICIPANTS

Adults with C1-T6 SCI (N=81). Individuals were eligible if ≥ 18 years old, with SCI of ≥ 3 months' duration, living within 100 miles of the study site, and not meeting exclusion criteria. Of the 161 individuals recruited from the SCI Model System database who were not enrolled, reasons were not interested in participating, change of location, prior positive pressure ventilation use, or medical contraindication. Ten individuals did not complete the study.

INTERVENTIONS

Performance of an unsupervised home sleep apnea test combined with transcutaneous partial pressure of carbon dioxide/oxygen saturation by pulse oximetry monitoring.

MAIN OUTCOME MEASURES

Prevalence of sleep-disordered breathing and nocturnal hypercapnia. Clinical and physiological variables were examined to determine which, if any, correlate with the severity of sleep-disordered breathing.

RESULTS

Obstructive sleep apnea (OSA) was found in 81.3% of individuals, central sleep apnea (CSA) was found in 23.8%, and nonspecific hypopnea events, where respiratory effort was too uncertain to classify, were present in 35%. Nonspecific hypopnea events correlated strongly with CSA but weakly with OSA, suggesting that conventional sleep apnea test scoring may underestimate central/neuromuscular hypopneas. Nocturnal hypercapnia was present in 28% and oxygen desaturation in 18.3%. Neck circumference was the primary predictor for OSA, whereas baclofen use and obstructive apnea/hypopnea index weakly predicted CSA. Awake transcutaneous partial pressure of carbon dioxide and CSA were only marginally associated with nocturnal hypercapnia.

CONCLUSIONS

Unsupervised home sleep apnea testing with transcutaneous capnography effectively identifies sleep-disordered breathing and nocturnal hypercapnia in individuals with SCI.

The impact of spinal cord injury on breathing during sleep

The prevalence of sleep disordered breathing (SDB) following spinal cord injury (SCI) is considerably greater than in the general population. While the literature on this topic is still relatively small, and in some cases contradictory, a few general conclusions can be drawn. First, while both central and obstructive sleep apnea (OSA) has been reported after SCI, OSA appears to be more common. Second, SDB after SCI likely reflects a complex interplay between multiple factors including body mass, lung volume, autonomic function, sleep position, and respiratory neuroplasticity. It is not yet possible to pinpoint a "primary factor" which will predispose an individual with SCI to SDB, and the underlying mechanisms may change during progression from acute to chronic injury. Given the prevalence and potential health implications of SDB in the SCI population, we suggest that additional studies aimed at defining the underlying mechanisms are warranted.

Home-based overnight transcutaneous capnography/pulse oximetry for diagnosing nocturnal hypoventilation associated with neuromuscular disorders

OBJECTIVE

To determine the utility of home-based, unsupervised transcutaneous partial pressure of carbon dioxide (tc-Pco(2)) monitoring/oxygen saturation by pulse oximetry (Spo(2)) for detecting nocturnal hypoventilation (NH) in individuals with neuromuscular disorders.

DESIGN

Retrospective case series analyzed consecutively.

SETTING

Multidisciplinary neuromuscular respiratory failure (NMRF) clinic at an academic institution.

PARTICIPANTS

Subjects (N=35, 68.6% men; mean age, 46.9y) with spinal cord injury (45.7%) or other neuromuscular disorders underwent overnight tests with tc-Pco(2)/Spo(2) monitoring. Fifteen (42.9%) were using nocturnal ventilatory support, either bilevel positive airway pressure (BiPAP) or tracheostomy ventilation (TV).

INTERVENTIONS

A respiratory therapist brought a calibrated tc-Pco(2)/Spo(2) monitor to the patient's home and provided instructions for data collection during the subject's normal sleep period. Forced vital capacity (FVC), body mass index (BMI), and exhaled end-tidal Pco(2) (ET-Pco(2)) were recorded at a clinic visit before monitoring.

MAIN OUTCOME MEASURES

Detection of NH (tc-Pco(2) ≥50mmHg for ≥5% of monitoring time). Data were also analyzed to determine whether nocturnal oxygen desaturation (Spo(2) ≤88% for ≥5% of monitoring time), FVC, BMI, or daytime ET-Pco(2) could predict the presence of NH.

RESULTS

NH was detected in 18 subjects (51.4%), including 53.3% of those using BiPAP or TV. NH was detected in 43.8% of ventilator-independent subjects with normal daytime ET-Pco(2) (present for 49.4%±31.5% [mean ± SD] of the study period), and in 75% of subjects with an elevated daytime ET-Pco(2) (present for 92.3%±8.7% of the study period). Oxygen desaturation, BMI, and FVC were poor predictors of NH. Only 3 attempted monitoring studies failed to produce acceptable results.

CONCLUSIONS

Home-based, unsupervised monitoring with tc-Pco(2)/Spo(2) is a useful method for diagnosing NH in NMRF.

An evidence-based review of aging of the body systems following spinal cord injury

STUDY DESIGN

Systematic review.

OBJECTIVE

To systematically review evidence on aging of the body systems after spinal cord injury (SCI).

SETTING

Toronto, Ontario and Vancouver, British Columbia, Canada.

METHODS

Electronic databases (MEDLINE/PubMed, CINAHL, EMBASE and PsycINFO), were searched for studies published between 1980 and 2009. The search was augmented by reviewing the reference lists of relevant papers. Non-intervention studies that were longitudinal or cross-sectional with able-bodied controls that were at minimum matched on chronological age were included for review. Levels of evidence were assigned to the study design using a modified Sackett scale.

RESULTS

Of the 74 studies selected for inclusion, 16 were longitudinal in design. The hypothesis that SCI represents a model for premature aging is supported by a large proportion of level 5 evidence for the cardiovascular and endocrine systems, level 2, 4 and 5 evidence for the musculoskeletal system, and limited level 5 evidence for the immune system. Only a few level 4 and 5 studies for the respiratory system were found. The evidence on the genitourinary system, gastrointestinal system, and for skin and subcutaneous tissues provide level 4 and 5 evidence that premature aging may not be occurring. The evidence on the nervous system does not provide evidence of premature aging as a result of SCI.

CONCLUSIONS

Premature aging appears to occur in some systems after SCI. Additional longitudinal studies are required to confirm these findings.

Pulmonary function and spinal cord injury

Injury to the cervical and upper thoracic spinal cord disrupts function of inspiratory and expiratory muscles, as reflected by reduction in spirometric and lung volume parameters and static mouth pressures. In association, subjects with tetraplegia have decreased chest wall and lung compliance, increased abdominal wall compliance, and rib cage stiffness with paradoxical chest wall movements, all of which contribute to an increase in the work of breathing. Expiratory muscle function is more compromised than inspiratory muscle function among subjects with tetraplegia and high paraplegia, which can result in ineffective cough and propensity to mucus retention and atelectasis. Subjects with tetraplegia also demonstrate heightened vagal activity with reduction in baseline airway caliber, findings attributed to loss of sympathetic innervation to the lungs. Significant increase in airway caliber following inhalation of ipratropium bromide, an anticholinergic agent, suggests that reduction in airway caliber is not due to acquired airway fibrosis stemming from repeated infections or to abnormal hysteresis secondary to chronic inability of subjects to inhale to predicted total lung capacity. Reduced baseline airway caliber possibly explains why subjects with tetraplegia exhibit airway hyperresponsiveness to methacholine and ultrasonically nebulized distilled water. While it has been well demonstrated that bilateral phrenic nerve pacing or stimulation through intramuscular diaphragmatic electrodes improves inspiratory muscle function, it remains unclear if inspiratory muscle training improves pulmonary function. Recent findings suggest that expiratory muscle training, electrical stimulation of expiratory muscles and administration of a long-acting beta(2)-agonist (salmeterol) improve physiological parameters and cough. It is unknown if baseline bronchoconstriction in tetraplegia contributes to respiratory symptoms, of if the chronic administration of a bronchodilator reduces the work of breathing and/or improves respiratory symptoms. Less is known regarding the benefits of treatment of obstructive sleep apnea, despite evidence indicating that the prevalence of this condition in persons with tetraplegia is far greater than that encountered in able-bodied individuals.

Cardiomyopathy presenting as severe fatigue in a person with chronic spinal cord injury

BACKGROUND/OBJECTIVE

To describe a case of fatigue associated with cardiomyopathy in a man with spinal cord injury.

STUDY DESIGN

Case report.

SUBJECT

An obese 35-year-old man with long-term ASIA A L2 paraplegia, accompanied by a 2-year history of progressive severe fatigue.

METHODS

Physical examination showed obesity, hypertension, tachycardia, and pitting edema. An echocardiogram showed a 20% ejection fraction, severe dilation, and global hypokinesis in the left ventricle and mild to moderate mitral regurgitation.

RESULTS

Symptoms improved after treatment with furosemide, warfarin, ramipril, and continuous positive airway pressure for obstructive sleep apnea.

CONCLUSION

Severe progressive fatigue in a patient with chronic SCI may signal cardiomyopathy. Diagnostic studies may be warranted in patients with progressive fatigue.

The feasibility of sleep assessment by actigraph in patients with tetraplegia

BACKGROUND

Sleep disturbances are frequent in patients with high spinal cord lesions, and are difficult to diagnose by means of polysomnography (PSG).

DESIGN

Retrospective cohort study.

OBJECTIVE

Examine the feasibility of sleep assessment by actigraph in patients with tetraplegia.

SETTING

A rehabilitation center in Israel.

SUBJECTS

Twenty-one patients with tetraplegia and 20 healthy persons.

INTERVENTIONS

Sleep assessment by actigraphs attached to the head and the wrist.

MAIN OUTCOME MEASURES

The actigraphic movement index (MI), total sleep time (TST), sleep efficiency (SE), wake after sleep onset (WASO), sleep latency (SL), and number of awakenings (NOA).

RESULTS

In the control group actigraphy showed that during sleep the hand moves more than the head but that the movements were highly correlated. In patients with tetraplegia below C(5)-C(7) the hand also moved more than the head, but in patients with tetraplegia below C(4), the head moved more (P<0.05). No significant differences were found between patients with C(5)-C(7) tetraplegia and healthy controls in the sleep indices obtained by hand movements, or between patients with C(4) tetraplegia and healthy controls in the indices obtained by head movements. Control subjects and patients showed similar subjective assessment of sleep quality.

CONCLUSIONS

These preliminary findings support the validity of wrist actigraphy for sleep assessment in patients with C(5)-C(7) tetraplegia, and suggest that head-mounted actigraphy is a feasible alternative for sleep assessment in patients with tetraplegia below C(4). To establish these findings, further investigations are required, with a larger number of patients and comparison with PSG.

A longitudinal evaluation of sleep and breathing in the first year after cervical spinal cord injury

OBJECTIVES

To establish the incidence of sleep disordered breathing (SDB) after acute tetraplegia and to determine the relation between the Apnea-Hypopnea Index (AHI) score and the previously postulated predictors of SDB in tetraplegia.

DESIGN

Inception cohort. We performed full polysomnography immediately after acute tetraplegia and at 2, 4, 13, 26, and 52 weeks postinjury. Spirometry, maximum inspiratory and expiratory pressures, medication usage, and neck and abdominal girth were also assessed. Preinjury SDB was estimated using the multivariate apnea prediction equation.

SETTING

Acute care, subacute care, and community.

PARTICIPANTS

Consecutive sample with acute tetraplegia. Thirty subjects (25 men) were initially included. Thirteen completed 12 months of follow-up.

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURES

SDB (AHI score >10 events/h) and respiratory function.

RESULTS

Three subjects (10%; 95% confidence interval [CI], 2%-28%) had probable SDB before injury. In the first 48 hours after injury, no subject had SDB. At 2 weeks, 60% (95% CI, 26%-88%) had SDB; at 4 weeks, 62% (95% CI, 38%-82%); at 13 weeks, 83% (95% CI, 61%-95%); at 26 weeks, 68% (95% CI, 44%-88%); and at 52 weeks, 62% (95% CI, 32%-86%). No consistent relation was found between the previously postulated predictors and SDB.

CONCLUSIONS

SDB is highly prevalent within 4 weeks of acute tetraplegia.

Nocturnal oximetry: utility in the respiratory management of amyotrophic lateral sclerosis

OBJECTIVE

Current recommendations are to institute nocturnal nasal ventilation for amyotrophic lateral sclerosis patients with a forced vital capacity (FVC) of <50% of predicted normal. The purpose of this study was to determine whether this is appropriate.

DESIGN

A total of 87 nocturnal oximetry evaluations were performed on 78 consecutive amyotrophic lateral sclerosis patients symptomatic for sleep-disordered breathing. Nocturnal oximetry measurements were compared for those with FVC >50% vs. those with FVC of <50% of normal. FVC was measured sitting and supine.

RESULTS

A considerable number of these symptomatic patients manifested evidence of nocturnal hypoxemia as measured by oximetry. However, there was no significant difference between patients with sitting percentage-predicted FVC above and below 50% predicted in minimum oxygen saturation, mean oxygen saturation, percentage of time spent with oxygen saturation of <88%, and number of events per hour. There was no significant difference between patients with supine percentage-predicted FVC above and below 50% predicted in minimum oxygen saturation, mean oxygen saturation, percentage of time spent with oxygen saturation of <88%, and number of events per hour.

CONCLUSION

The recommendation that FVC be <50% of normal is inappropriate for justifying introduction of nocturnal nasal ventilation. Many patients are symptomatic at higher FVC and manifest evidence of nocturnal hypoxemia. Nocturnal oximetry adds additional practical information for justifying earlier respiratory intervention for symptomatic patients.

Characteristics of sleep apnea syndrome in tetraplegic patients

OBJECTIVE

To include a larger number of tetraplegics than in previous studies, in order to more reliably characterize the pathogenesis and predisposing factors of sleep apnea in tetraplegia.

METHODS

Sleep breathing data and oxymetric values were investigated in 50 randomly selected tetraplegic patients and discussed in context with age, gender, BMI, neck circumference, type and height of lesion, time after injury, spirometric values and medication. A non-validated short questionnaire on daytime complaints was added.

RESULTS

Thirty-one patients out of 50 had an RDI > or =15, defined as sleep disordered breathing (SDB); 24 of them combined with an apnea index of 5 or more, these cases were diagnosed as sleep apnea syndrome (SAS). SAS was apparent in 55% and 20% of the studied men and women, respectively. Regression analyses showed no significant correlation between RDI and lesion level, ASIA impairment scale or spirometric values. In contrast, a significant correlation between RDI and age, BMI, neck circumference and time after injury could be shown. Kruskal-Wallis test for dichotomous non-parametric factors, such as gender, cardiac medication and daytime complaints, showed significant differences with regard to RDI. In contrast to able-bodied people with SAS, daytime complaints were only present in tetraplegic patients with severe pathology (RDI>40).

CONCLUSION

Incidence of SAS is high in tetraplegia, particularly in older male patients with large neck circumference, long standing spinal cord injury and under cardiac medication. As tetraplegics with RDI between 15 and 40 reported no daytime complaints and often have normal BMI, these tetraplegics are not clinically suspicious for SAS. The increased use of cardiac medication in tetraplegics with SAS may implicate a link between SAS and cardiovascular morbidity, one of the leading causes of death in tetraplegia.

Resistive inspiratory muscle training in sleep-disordered breathing of traumatic tetraplegia

OBJECTIVE

To assess the effect of resistive inspiratory muscle training (RIMT) on the static pulmonary function and sleep-induced breathing disorder of individuals with chronic cervical cord injury.

DESIGN

Before-after training.

SETTING

Home-setting training program.

PATIENTS

Fourteen complete traumatic tetraplegic patients (12 men, 2 women; mean age, 41.1 +/- 14y; range, 19-56y) injured for more than 6 months.

INTERVENTION

Subjects participated in a 6-week RIMT program for 15 minutes twice daily at a training intensity of 60% of maximum inspiratory pressure (MIP). The participants were reevaluated at the end of 6-week training.

MAIN OUTCOME MEASURES

Lung volume, peak expiratory flow (PEF), MIP, and maximum expiratory pressure (MEP) were measured by using a spirometry and inspiratory force meter, respectively. Capnography was used to monitor nocturnal pulse oxyhemoglobin saturation (SpO(2)) and end-tidal carbon dioxide tension level (ETCO(2)) of the patients.

RESULTS

The maximum voluntary ventilation (MVV) and MIP of individuals with chronic cervical cord injury substantially improved after RIMT. MIP increased from -68.7 +/- 27.4cmH(2)O to -77.3 +/- 24.0cmH(2)O and MVV rose from 62.7 +/- 33.2L to 73.4 +/- 31.3L (P <.05). Despite increasing from 3.5 +/- 1.8L/s to 4.0 +/- 1.7L/s, PEF was statistically insignificant. For the individuals with improved MIP, the duration of ETCO(2) greater than 48mmHg reduced from 2.2% +/- 3.3% to 1.0% +/- 2.0% of total sleep time (P =.05) and that of SpO(2) less than 90% significantly declined from 1.8% +/- 2.8% to 1.3% +/- 2.4% of total sleep time (P <.05).

CONCLUSION

These findings suggest that RIMT can enhance the respiratory muscle strength and endurance of chronic tetraplegia and further ameliorate the sleep-induced breathing disorder. Therefore, RIMT is suggested as a home program for patients with sleep-disordered breathing.

Sleep disturbances in the spinal cord injured: an epidemiological questionnaire investigation, including a normal population

STUDY DESIGN

Epidemiological review.

OBJECTIVE

To evaluate sleep disturbances in the spinal cord injured.

SETTING

The Clinic for Para- and Tetraplegia, Hornbaek/Copenhagen, Copenhagen University hospital, Denmark.

METHODS

All patients admitted with traumatic SCI during the 20-year period 1968-1987 were reviewed. The normal population consisted of 339, 222 men and 117 women. These groups were asked to fill in the self-administered Nordic Sleep Questionnaire (NSQ) containing 21 questions. Questions were added regarding employment, smoking, alcohol, coffee or tea consumption, height and weight. The questionnaire for SCI individuals included questions about bladder emptying method, mobility, and spasms. For the SCI population age at injury, cause of injury, neurological level, and functional class were retrieved.

RESULTS

Four hundred and eight SCI individuals, 331 men and 77 women, answered the NSQ corresponding to a response rate of 83.8%. Forty-seven per cent had a cervical cord lesion and about half of the population had a complete motor lesion. In comparison with the normal population the SCI individuals had greater difficulty in falling asleep, described more frequent awakenings, slept subjectively less well, were more often prescribed sleeping pills, slept more hours, took more and longer naps, and snored more and for more years. In particular, spasms, pain, paraesthesia, and troubles with voiding were claimed to be part of the sleep problems.

CONCLUSION

In spite of the same average age and a higher body mass index in the normal than the SCI population, the SCI individuals showed significantly more sleep problems than the normal population.

Delayed apnea in patients with mid- to lower cervical spinal cord injury

STUDY DESIGN

A retrospective study of 36 patients with mid- to lower cervical spinal cord injury (CSCI) divided into two groups based on whether delayed apnea developed.

OBJECTIVES

To determine nonpulmonary risk factors associated with the development of delayed apnea in mid- to lower cervical spinal cord injury.

SUMMARY OF BACKGROUND DATA

Patients with mid- to lower cervical spinal cord injury are generally at lower risk of developing respiratory failure than those with high cervical spinal cord injury. Respiratory failure manifesting as sudden apnea may occur days or even weeks after injury without any pulmonary complications in such patients.

METHODS

An index group of eight patients with complete mid- to lower cervical spinal cord injury in whom delayed catastrophic apnea occurred were reviewed. Another group of 28 patients with cervical spinal cord injury of identical magnitude and presentation but without respiratory failure served as the control group. Six parameters presumed to be related to the delayed apnea were analyzed.

RESULTS

The extent of cord lesions was significantly different, being diffuse in most of the index patients, but focal in the majority of the control patients (P<0.001). Involvement of the C4 segment of cord appeared to be more frequent in the index group; however, the difference was not statistically significant (P = 0.091). The incidence of transient bradycardia (P<0.01) and dyspnea (P<0.001) in the index group was significantly higher than in the control group. Paralytic ileus was a much rarer event and found to be unrelated to the occurrence of apnea. In five of the eight index patients, the apnea occurred during sleep. Six of the eight index patients died of it.

CONCLUSIONS

Delayed but devastating apnea may develop in patients with mid- to lower cervical cervical spinal cord injury, even when they are clinically stable and free from any pulmonary complications. The presence of diffuse, extensive cord lesions, respiratory distress, or bradycardia with or without associated hypotension, however transient and self-limited, should be regarded as warning signs. Sleep was found to be a risky period of time.

Oxygen desaturations during exercise and sleep in fit tetraplegic patients

OBJECTIVE

Tetraplegic patients are particularly at risk for respiratory deficiencies during sleep. In a previous study, it was found that several patients exhibited significant oxygen desaturations during arm ergometry tests. Therefore, the issue of whether patients who desaturate during exercise would be especially at risk for having nocturnal respiratory problems was raised.

DESIGN

Respiratory recordings in connection with arm ergometry tests and during sleep.

SETTING

Arm ergometry tests were performed in a hospital laboratory, and sleep recordings were performed in the patients' homes.

PATIENTS

Nine C5-C6 tetraplegic patients, aged 22 to 42 years with body mass index of 15.2 to 24.2 kg/m2.

MAIN OUTCOME MEASURES

Oximetry during exercise and sleep and sleep recordings.

RESULTS

During exercise, six patients desaturated 6% to 20%. Only one patient had signs of a significant nocturnal respiratory problem with an average of eight desaturations per hour of sleep and an obstructive respiration movement pattern. Two additional patients (with normal oximetry during exercise) showed occasional desaturation below 89% during rapid eye movement sleep.

CONCLUSION

In this study, the majority of tetraplegic patients desaturated during submaximal arm exercise but not during sleep. The reason could be that the patients in this study were all lean and physically active, which is at variance with previously published sleep studies.