Nocturnal nasal ventilation for treatment of patients with hypercapnic respiratory failure

Long-term noninvasive ventilation in COPD: current evidence and future directions

Introduction: Long-term noninvasive ventilation (NIV) is an established treatment for end-stage COPD patients suffering from chronic hypercapnic respiratory failure. This is reflected by its prominent position in national and international medical guidelines. Areas covered: In recent years, novel developments in technology such as auto-titrating machines and hybrid modes have emerged, and when combined with advances in information and communication technologies, these developments have served to improve the level of NIV-based care. Such progress has largely been instigated by the fact that healthcare systems are now confronted with an increase in the number of patients, which has led to the need for a change in current infrastructures. This article discusses the current practices and recent trends, and offers a glimpse into the future possibilities and requirements associated with this form of ventilation therapy. Expert opinion: Noninvasive ventilation is an established and increasingly used treatment option for patients with chronic hypercapnic COPD and those with persistent hypercapnia following acute hypercapnic lung failure. The main target is to augment alveolar hypoventilation by reducing P_aCO₂ to relieve symptoms. Nevertheless, when dealing with severely impaired patients, it appears necessary to switch the focus to patient-related outcomes such as health-related quality of life.

Home initiation of chronic non-invasive ventilation in COPD patients with chronic hypercapnic respiratory failure: a randomised controlled trial

INTRODUCTION

Chronic non-invasive ventilation (NIV) has become evidence-based care for stable hypercapnic COPD patients. While the number of patients increases, home initiation of NIV would greatly alleviate the healthcare burden. We hypothesise that home initiation of NIV with the use of telemedicine in stable hypercapnic COPD is non-inferior to in-hospital NIV initiation.

METHODS

Sixty-seven stable hypercapnic COPD patients were randomised to initiation of NIV in the hospital or at home using telemedicine. Primary outcome was daytime arterial carbon dioxide pressure (PaCO₂) reduction after 6 months NIV, with a non-inferiority margin of 0.4 kPa. Secondary outcomes were health-related quality of life (HRQoL) and costs.

RESULTS

Home NIV initiation was non-inferior to in-hospital initiation (adjusted mean difference in PaCO₂ change home vs in-hospital: 0.04 kPa (95% CI -0.31 to 0.38 kPa), with both groups showing a PaCO₂ reduction at 6 months compared with baseline (home: from 7.3±0.9 to 6.4±0.8 kPa (p<0.001) and in-hospital: from 7.4±1.0 to 6.4±0.6 kPa (p<0.001)). In both groups, HRQoL improved without a difference in change between groups (Clinical COPD Questionnaire total score-adjusted mean difference 0.0 (95% CI -0.4 to 0.5)). Furthermore, home NIV initiation was significantly cheaper (home: median €3768 (IQR €3546-€4163) vs in-hospital: median €8537 (IQR €7540-€9175); p<0.001).

DISCUSSION

This is the first study showing that home initiation of chronic NIV in stable hypercapnic COPD patients, with the use of telemedicine, is non-inferior to in-hospital initiation, safe and reduces costs by over 50%.

TRIAL REGISTRATION NUMBER

NCT02652559.

Home mechanical ventilation for chronic obstructive pulmonary disease: What next after the HOT-HMV trial?

The benefits of acute non-invasive ventilation to treat acidotic exacerbations of chronic obstructive pulmonary disease (COPD) are well-established. Until recently, the evidence for home mechanical ventilation (HMV) to treat patients with stable COPD had been lacking. This has subsequently been addressed by the application of higher levels of pressure support combined with targeted management of chronic respiratory failure, which demonstrated a reduction in all-cause mortality. Similarly, the previous trial of home oxygen therapy (HOT) and HMV delivered following an acute exacerbation failed to demonstrate an improvement in outcome. With the focus on patients with persistent hypercapnic respiratory failure in the recovery phase following a life-threatening exacerbation combined with targeted reduction in carbon dioxide, HOT and HMV (HOT-HMV) was shown to be clinically effective in reducing the time to readmission or death and cost effective in both the United Kingdom and United States healthcare systems. Future work will need to focus on promoting adherence to home ventilation and novel auto-titrating ventilator modes to facilitate and optimize the set-up of overnight ventilatory support in different target population such as COPD patients with obstructive sleep apnoea and COPD patients with episodic nocturnal hypoventilation.

Noninvasive ventilation in stable hypercapnic COPD: what is the evidence?

Long-term noninvasive ventilation (NIV) to treat chronic hypercapnic respiratory failure is still controversial in severe chronic obstructive pulmonary disease (COPD) patients. However, with the introduction of high-intensity NIV, important benefits from this therapy have also been shown in COPD. In this review, the focus will be on the arguments for long-term NIV at home in patients with COPD. The rise of (high-intensity) NIV in COPD and the randomised controlled trials showing positive effects with this mode of ventilation will be discussed. Finally, the challenges that might be encountered (both in clinical practice and in research) in further optimising this therapy, monitoring and following patients, and selecting the patients who might benefit most will be reviewed.

The cost-effectiveness of domiciliary non-invasive ventilation in patients with end-stage chronic obstructive pulmonary disease: a systematic review and economic evaluation

BACKGROUND

Chronic obstructive pulmonary disease (COPD) is a chronic progressive lung disease characterised by non-reversible airflow obstruction. Exacerbations are a key cause of morbidity and mortality and place a considerable burden on health-care systems. While there is evidence that patients benefit from non-invasive ventilation (NIV) in hospital during an acute exacerbation, evidence supporting home use for more stable COPD patients is limited. In the U.K., domiciliary NIV is considered on health economic grounds in patients after three hospital admissions for acute hypercapnic respiratory failure.

OBJECTIVE

To assess the clinical effectiveness and cost-effectiveness of domiciliary NIV by systematic review and economic evaluation.

DATA SOURCES

Bibliographic databases, conference proceedings and ongoing trial registries up to September 2014.

METHODS

Standard systematic review methods were used for identifying relevant clinical effectiveness and cost-effectiveness studies assessing NIV compared with usual care or comparing different types of NIV. Risk of bias was assessed using Cochrane guidelines and relevant economic checklists. Results for primary effectiveness outcomes (mortality, hospitalisations, exacerbations and quality of life) were presented, where possible, in forest plots. A speculative Markov decision model was developed to compare the cost-effectiveness of domiciliary NIV with usual care from a UK perspective for post-hospital and more stable populations separately.

RESULTS

Thirty-one controlled effectiveness studies were identified, which report a variety of outcomes. For stable patients, a modest volume of evidence found no benefit from domiciliary NIV for survival and some non-significant beneficial trends for hospitalisations and quality of life. For post-hospital patients, no benefit from NIV could be shown in terms of survival (from randomised controlled trials) and findings for hospital admissions were inconsistent and based on limited evidence. No conclusions could be drawn regarding potential benefit from different types of NIV. No cost-effectiveness studies of domiciliary NIV were identified. Economic modelling suggested that NIV may be cost-effective in a stable population at a threshold of £30,000 per quality-adjusted life-year (QALY) gained (incremental cost-effectiveness ratio £28,162), but this is associated with uncertainty. In the case of the post-hospital population, results for three separate base cases ranged from usual care dominating to NIV being cost-effective, with an incremental cost-effectiveness ratio of less than £10,000 per QALY gained. All estimates were sensitive to effectiveness estimates, length of benefit from NIV (currently unknown) and some costs. Modelling suggested that reductions in the rate of hospital admissions per patient per year of 24% and 15% in the stable and post-hospital populations, respectively, are required for NIV to be cost-effective.

LIMITATIONS

Evidence on key clinical outcomes remains limited, particularly quality-of-life and long-term (> 2 years) effects. Economic modelling should be viewed as speculative because of uncertainty around effect estimates, baseline risks, length of benefit of NIV and limited quality-of-life/utility data.

CONCLUSIONS

The cost-effectiveness of domiciliary NIV remains uncertain and the findings in this report are sensitive to emergent data. Further evidence is required to identify patients most likely to benefit from domiciliary NIV and to establish optimum time points for starting NIV and equipment settings.

FUTURE WORK RECOMMENDATIONS

The results from this report will need to be re-examined in the light of any new trial results, particularly in terms of reducing the uncertainty in the economic model. Any new randomised controlled trials should consider including a sham non-invasive ventilation arm and/or a higher- and lower-pressure arm. Individual participant data analyses may help to determine whether or not there are any patient characteristics or equipment settings that are predictive of a benefit of NIV and to establish optimum time points for starting (and potentially discounting) NIV.

STUDY REGISTRATION

This study is registered as PROSPERO CRD42012003286.

FUNDING

The National Institute for Health Research Health Technology Assessment programme.

Management of pulmonary complications in neuromuscular disease

Restrictive lung disease occurs commonly in patients with neuromuscular disease. The earliest sign of respiratory compromise in the patient with neuromuscular disease is nocturnal hypoventilation, which progresses over time to include daytime hypoventilation and eventually the need for full-time mechanical ventilation. Pulmonary function testing should be done during regular follow-up visits to identify the need for assistive respiratory equipment and initiate early noninvasive ventilation. Initiation of noninvasive ventilation can improve quality of life and prolong survival in patients with neuromuscular disease.

Current Issues in Home Mechanical Ventilation

As modern health care continues to evolve, we expect and are seeing that more sophisticated medical care will be provided outside the traditional acute care environments. Advances in home medical technology, economic pressures, health-care consumerism, and societal changes are all factors playing a role in this evolution. Medically fragile and technology-dependent individuals who were once limited to care in acute and subacute institutional settings are now frequently cared for at home, most often by their immediate family members. Mechanical ventilation has found its way into the patient's home such that physicians and other providers must be prepared for the challenges associated with managing the conditions of complex, ventilator-dependent individuals outside of the walls, controls, and safety of the institutional setting. With little published science and recognized standards of practice, there are fewer rules to guide clinicians through this process. Experience has shown, however, that successful home management of ventilator-dependent individuals can be traced to a smooth and collaborative discharge from the hospital to home. Reimbursement and coverage issues must also be well understood to avoid the aggravation of denials and challenges for necessary equipment and assistance. Once home, a streamlined, patient-centered process supported by effective communication between all care providers can result in a safe and appropriate long-term home ventilation success story.

Six-month nocturnal nasal positive pressure ventilation improves respiratory muscle capacity and exercise endurance in patients with chronic hypercapnic respiratory failure

BACKGROUND/PURPOSE

This study was designed to investigate the effects of 6 months of nocturnal nasal positive pressure ventilation (NNPPV) on respiratory muscle function and exercise capacity in patients with chronic respiratory failure.

METHODS

A prospective, randomized, controlled design was used. Twenty-nine patients with chronic respiratory failure were enrolled and allocated to either the NNPPV (n = 14) or control group (n = 15). Patients in the NNPPV group received bi-level positive pressure ventilation via nasal mask for 6 consecutive months. Arterial blood gas, respiratory muscle assessment and 6-minute walk test (6MWT) were performed before and after the 6-month NNPPV intervention. Respiratory muscle function was assessed using the variables of maximal inspiratory pressure (Pimax), maximal expiratory pressure (Pemax), and maximum voluntary ventilation (MVV).

RESULTS

Subjects in the NNPPV group showed a significant improvement in blood gas exchange and increased 6-minute walk distance (6MWD) compared to baseline and the control group. The 6MWD was significantly increased from 257.1 +/- 114.1 to 345.2 +/- 109.9 m (34.3%) in the NNPPV group. NNPPV also significantly improved MVV and Pimax relative to baseline. MVV was significantly increased from 19.2 +/- 6.5 to 22.3 +/- 7.1 L/min (16.1%) in the NNPPV group (p < 0.05). Furthermore, there was a significant correlation between the magnitude of MVV improvement and 6MWD change.

CONCLUSION

The 6-month NNPPV treatment significantly decreased the partial pressure of carbon dioxide and improved daytime respiratory muscle function, thus contributing to exercise-capacity increase in patients with chronic respiratory failure.

Management of respiration in MND/ALS patients: an evidence based review

This systematic review comprises an objective appraisal of the evidence in regard to the management of respiration in patients with motor neuron disease (MND/ALS). Studies were identified through computerised searches of 32 databases. Internet searches of websites of drug companies and MND/ALS research web sites, 'snow balling' and hand searches were also employed to locate any unpublished study or other 'grey literature' on respiration and MND/ALS. Since management of MND/ALS involves a number of health professionals and care workers, searches were made across multiple disciplines. No time frame was imposed on the search in order to increase the probability of identifying all relevant studies, although there was a final limit of March 2005. Recommendations for patient and carer-based guidelines for the clinical management of respiration for MND/ALS patients are suggested on the basis of qualitative analyses of the available evidence. However, these recommendations are based on current evidence of best practice, which largely comprises observational research and clinical opinion. There is a clear need for further evidence, in particular randomised and non-randomised controlled trials on the effects of non-invasive ventilation and additional larger scale cohort studies on the issues of initial assessment of respiratory symptoms, and management and timing of interventions.

Ventilatory management of sleep-disordered breathing in children

PURPOSE OF REVIEW

The purpose of this review is to summarize the current management of continuous positive airway pressure and noninvasive positive pressure ventilation in children with sleep-disordered breathing.

RECENT FINDINGS

Although most children with sleep-disordered breathing respond to surgical treatment, the use of continuous positive airway pressure and noninvasive positive pressure ventilation in nonresponders has become common, with hundreds of cases reported in the literature, despite the fact that these devices are not approved by the Food and Drug Administration for use in children weighing under 30 kg. Studies show that continuous positive airway pressure and non-invasive positive pressure ventilation are safe and efficacious. Side-effects are minor, and include nasal symptoms and skin breakdown. Midfacial hypoplasia is an uncommon adverse event. Problems with triggering and cycling of noninvasive positive pressure ventilation remain an issue in small or weak children. As in adults, poor adherence is the major obstacle to successful continuous positive airway pressure or noninvasive positive pressure ventilation use.

SUMMARY

Continuous positive airway pressure is a useful second-line treatment for children with sleep-disordered breathing. Strategies to improve adherence are needed. Equipment manufacturers should be encouraged to develop equipment that better meets children's needs.

Home mechanical ventilatory support in patients with restrictive ventilatory disorders: A 48-year experience

We performed a retrospective analysis to the effects of negative pressure ventilation (NPV), tracheal intermittent positive pressure ventilation (TIPPV), and nasal intermittent positive pressure ventilation (NIPPV, volume or pressure-controlled ventilatory mode), in 114 patients with restrictive ventilatory disorders instituted in our hospital from 1956 until 2005. The patients were assigned on "ad hoc" basis to NPV, TIPPV, or NIPPV. All patients were subdivided in an idiopathic kyphoscoliosis group (IK, n=64), a post-poliomyelitis syndrome group (PP, n=30), or a miscellaneous group (M, n=20). The patients in the PP group had higher survival rates compared to the IK patients (P<0.05), while the M patients had the lowest survival rates (P<0.01). Both NPV (P<0.01) and TIPPV (P<0.05) lead to a decrease in PaCO2 after 9 months compared to baseline. This decrease in PaCO2 was still present after 5 years NPV (P<0.001) and TIPPV (P<0.05). NIPPV lead to an improvement in pulmonary function (P<0.05) and arterial blood gases (P<0.001) after 9 months compared to baseline. After 5 years NIPPV, the arterial blood gases were still significantly improved compared to baseline (P<0.01). Both volume-controlled and pressure-controlled ventilation improved pulmonary function and arterial blood gases.

CONCLUSION

Long-term home mechanical ventilatory support by both NPV and positive pressure ventilation is effective in patients with IK, PP syndrome, and a M group, even after a period of 5 years.

Randomised crossover study of pressure and volume non-invasive ventilation in chest wall deformity

BACKGROUND

Non-invasive ventilation is an established treatment for chronic respiratory failure due to chest wall deformity. There are few data available to inform the choice between volume and pressure ventilators. The aim of this study was to compare pressure and volume targeted ventilation in terms of diurnal arterial blood gas tensions, lung volumes, hypercapnic ventilatory responses, sleep quality, and effect on daytime function and health status when ventilators were carefully set to provide the same minute ventilation.

METHODS

Thirteen patients with chest wall deformity underwent a 4 week single blind randomised crossover study using the Breas PV403 ventilator in either pressure or volume mode with assessments made at the end of each 4 week period.

RESULTS

Minute ventilation at night was less than that set during the day with greater leakage for both modes of ventilation. There was more leakage with pressure than volume ventilation (13.8 (1.9) v 5.9 (1.0) l/min, p = 0.01). There were no significant differences in sleep quality, daytime arterial blood gas tensions, lung mechanics, ventilatory drive, health status or daytime functioning.

CONCLUSIONS

These data suggest that pressure and volume ventilation are equivalent in terms of the effect on nocturnal and daytime physiology, and resulting daytime function and health status.

Mechanisms of improvement of respiratory failure in patients with restrictive thoracic disease treated with non-invasive ventilation

BACKGROUND

Nocturnal non-invasive ventilation (NIV) is an effective treatment for hypercapnic respiratory failure in patients with restrictive thoracic disease. We hypothesised that NIV may reverse respiratory failure by increasing the ventilatory response to carbon dioxide, reducing inspiratory muscle fatigue, or enhancing pulmonary mechanics.

METHODS

Twenty patients with restrictive disease were studied at baseline (D0) and at 5-8 days (D5) and 3 months (3M).

RESULTS

Mean (SD) daytime arterial carbon dioxide tension (Paco(2)) was reduced from 7.1 (0.9) kPa to 6.6 (0.8) kPa at D5 and 6.3 (0.9) kPa at 3M (p = 0.004), with the mean (SD) hypercapnic ventilatory response increasing from 2.8 (2.3) l/min/kPa to 3.6 (2.4) l/min/kPa at D5 and 4.3 (3.3) l/min/kPa at 3M (p = 0.044). No increase was observed in measures of inspiratory muscle strength including twitch transdiaphragmatic pressure, nor in lung function or respiratory system compliance.

CONCLUSIONS

These findings suggest that increased ventilatory response to carbon dioxide is the principal mechanism underlying the long term improvement in gas exchange following NIV in patients with restrictive thoracic disease. Increases in respiratory muscle strength (sniff oesophageal pressure and sniff nasal pressure) correlated with reductions in the Epworth sleepiness score, possibly indicating an increase in the ability of patients to activate inspiratory muscles rather than an improvement in contractility.

Ventilator Weaning by Lung Expansion and Decannulation

This case series of ventilator-dependent patients with neuromuscular disease who had no ventilator-free breathing ability demonstrates that decannulation and switching to continuous noninvasive intermittent positive-pressure ventilation combined with regular lung expansion therapy can result in improvements in pulmonary function and at least partial ventilator weaning. These six patients were also managed using mechanical insufflation-exsufflation for regular lung expansion and cough assistance. Thus, some ventilator users with neuromuscular disease can benefit from tracheostomy tube decannulation and transition to noninvasive intermittent positive-pressure ventilation and assisted coughing for ventilator weaning to predominantly nocturnal-only use.

Longitudinal effects of noninvasive positive-pressure ventilation in patients with amyotrophic lateral sclerosis

OBJECTIVE

To evaluate the duration of benefit on symptoms, quality of life, and survival derived from the use of noninvasive positive-pressure ventilation by patients with amyotrophic lateral sclerosis.

DESIGN

In this prospective, cohort study, 30 of 36 consecutively referred symptomatic patients tolerated nightly noninvasive positive-pressure ventilation and undertook pulmonary function testing and 12 symptom and quality-of-life instruments concerning sleep quality, daytime sleepiness, physical fatigue, mental fatigue, and depression that were administered during a 10-mo period.

RESULTS

With treatment, there was a significant improvement in the majority of patients in sleep quality, daytime sleepiness, physical fatigue, and depression; however, significant improvements lasted for up to 10 mo only in sleep quality. Partial pressure of arterial oxygen, partial pressure of arterial carbon dioxide, and oxyhemoglobin saturation remained stable or even improved for up to 7 mo during use of part-time noninvasive positive-pressure ventilation. A total of 14 patients had survival prolonged by continuous dependence on noninvasive positive-pressure ventilation.

CONCLUSIONS

Noninvasive positive-pressure ventilation provides a long-lasting benefit on symptoms and quality of life indicators for amyotrophic lateral sclerosis patients and should be offered to all patients with symptoms of sleep disordered breathing or inspiratory muscle dysfunction. It can also prolong tracheostomy-free survival.

Nocturnal nasal ventilatory support in the management of daytime hypercapnic respiratory failure

Nasal ventilation is becoming increasingly recognised as an effective therapeutic strategy to minimise or correct hypercapnia in patients with respiratory failure. Intervention may be required on a short or long term basis. In the majority of patients, respiratory failure develops initially during sleep. Assessing patients at risk of nocturnal hypoventilation, and instituting appropriate therapy, is becoming an increasingly important aspect of respiratory care. This review outlines methods and practices involved in commencing nasal ventilation therapy. Twenty-nine patients presenting with hypercapnic respiratory failure were managed with nocturnal nasal ventilation over a 12 month period. With the use of this therapy PaCO2 fell from 64(2) to 50(1)mmHg (Mean(SE)) (p<0.001), while PaO2 improved from 55(2) to 68(2)mmHg (p<0.001) during a mean ventilation time of 10(0.8) days. Those factors which must be addressed for a successful program outcome are discussed.

Objective measures of the efficacy of noninvasive positive-pressure ventilation in amyotrophic lateral sclerosis

The impact of noninvasive positive-pressure ventilation (NIPPV) on pulmonary function studies, quality of life, and survival was assessed in patients with amyotrophic lateral sclerosis. NIPPV did not change the rate of decline of the forced vital capacity (FVC) and forced expiratory volume in the first second (FEV(1)) (2.31 and 2.09 percent-predicted points per month, respectively). NIPPV resulted in a drop of FEV(1) by 5.94 percent-predicted points (P = 0.07), and of maximal inspiratory pressure by 6.33 percent-predicted points (P = 0.11). The change in FEV(1) and FVC pre- and postintervention correlated with the corresponding change in maximal inspiratory pressure. Fatigue and mastery scores were improved by NIPPV. Median survivals in patients intolerant and tolerant of NIPPV were 5 and 20 months, respectively (P = 0.002). Although NIPPV has no impact on the rate of decline of lung function and may have deleterious effects on spirometric measures, it may improve quality of life and survival.

Weaning injured patients with prolonged pulmonary failure from mechanical ventilation in a non-intensive care unit setting

BACKGROUND

Injured patients with pulmonary failure often require prolonged length of stay in an intensive care unit (ICU), which includes weaning from ventilatory support. In the last decade, noninvasive ventilation modes have been established as safe and effective. One method for accomplishing this mode of ventilation uses a simple bilevel ventilator. Because this ventilator has been successfully used in hospital wards, we postulated that bilevel ventilators could provide sufficient support during weaning from mechanical ventilation of injured patients in a non-ICU setting.

METHODS

A retrospective review of trauma patients (August 1996-January 1999) undergoing bilevel positive pressure ventilation as the final phase of weaning was conducted. Before ward transfer with bilevel ventilation, conventionally ventilated ICU patients were changed to bilevel ventilation and were required to tolerate this mode for at least 24 hours. All patients had a tracheostomy as a secure airway. Outcomes analyzed included ICU length of stay, hospital length of stay, duration of mechanical ventilation, weaning success, complications, and survival.

RESULTS

Fifty-one patients (39 men, 12 women) with a mean age of 53 received more than 24 hours of bilevel positive pressure ventilation. Mean Injury Severity Score was 29, with blunt mechanisms of injury occurring in 90%. Chest or spinal cord injuries that affected pulmonary mechanics were present in 75% of patients. Ventilator-associated pneumonia was treated in 43% of patients. Mean ICU length of stay and hospital length of stay were 21 and 34 days, respectively. Weaning was successful in 89% of patients, whereas 11% were discharged to skilled nursing facilities still receiving bilevel positive pressure ventilation. Two patients died, neither from a pulmonary nor airway complication. Of the remaining 49 patients, 12 were weaned in the ICU and 37 were transferred to the ward with bilevel ventilatory support. The average length of ward ventilation was 6.5 +/- 5.4 days (n = 37).

CONCLUSIONS

Implementation of a program using bilevel ventilation to support the terminal phase of weaning seriously injured patients from mechanical ventilation was successful. After initiating this mode in the ICU, it was satisfactorily continued in standard surgical wards. Because this method enabled the withdrawal of ventilatory support in a non-ICU setting, its major advantage was reducing ICU length of stay.

Effect of non-invasive mechanical ventilation on sleep and nocturnal ventilation in patients with chronic respiratory failure

BACKGROUND

Chronic respiratory failure (CRF) is associated with nocturnal hypoventilation. Due to the interaction of sleep and breathing, sleep quality is reduced during nocturnal hypoventilation. Non-invasive mechanical ventilation (NMV), usually performed overnight, relieves symptoms of hypoventilation and improves daytime blood gas tensions in patients with CRF. The time course of the long term effect of NMV on sleep and breathing during both spontaneous ventilation (withdrawing the intervention) and NMV was investigated in patients with CRF due to thoracic restriction.

METHODS

Fifteen consecutive patients (13 women) of mean (SD) age 57.9 (12.0) years with CRF due to thoracic restriction were included in the study. During the one year observation period four polysomnographic studies were performed: three during spontaneous breathing without NMV-before initiation of NMV (T0) and after withdrawing NMV for one night at six months (T6) and 12 months (T12-)-and the fourth during NMV after 12 months (T12+). Daytime blood gas tensions and lung function were also measured.

RESULTS

Spontaneous ventilation (in terms of mean oxygen saturation) progressively improved (from T0 to T12-) during both REM sleep (24.8%, 95% CI 12.9 to 36.9) and NREM sleep (21.5%, 95% CI 12.4 to 30.6). Sleep quality during spontaneous ventilation also improved in terms of increased total sleep time (26. 8%, 95% CI 11.6 to 42.0) and sleep efficiency (17.5%, 95% CI 5.4 to 29.6) and decreased awakenings (54.0%, 95% CI 70.3 to 37.7). Accordingly, REM and NREM sleep stages 3 and 4 significantly improved. However, the most significant improvements in both nocturnal ventilation and sleep quality were seen during NMV at 12 months.

CONCLUSIONS

After long term NMV both spontaneous ventilation during sleep and sleep quality in patients with CRF due to thoracic restriction showed evidence of progressive improvement compared with baseline after withdrawal of NMV for a single night at six and 12 months. However, the greatest improvements in nocturnal ventilation and sleep were achieved during NMV at 12 months.

The control of breathing in clinical practice

The control of breathing results from a complex interaction involving the respiratory centers, which feed signals to a central control mechanism that, in turn, provides output to the effector muscles. In this review, we describe the individual elements of this system, and what is known about their function in man. We outline clinically relevant aspects of the integration of human ventilatory control system, and describe altered function in response to special circumstances, disorders, and medications. We emphasize the clinical relevance of this topic by employing case presentations of active patients from our practice.

Can amyotrophic lateral sclerosis patients with respiratory insufficiency exercise?

The authors have shown in a recent paper that survival with amyotrophic lateral sclerosis (ALS) can be increased by the use of non-invasive methods of assisted ventilation (Bipap). However, the progression of muscle weakness was not affected and the quality of life was not positively enhanced. In ALS, reduced physical activity may partially be secondary to alveolar hypoventilation syndrome. This leads to deconditioning of ALS/motor neuron disease (ALS/MND) patients. The authors decided to investigate the possibility of reducing motor decline by exercising these patients to the anaerobic threshold, but simultaneously compensating the respiratory insufficiency with the Bipap STD. We conducted a controlled single blind study, exercising eight consecutive ALS/MND patients and used a control group of 12 ALS/MND patients. The patients were all evaluated during a 1 year period. Respiratory function tests (RFT) were performed at entry and then at 6 month intervals. Barthel, Functional Independent Mobility scale (FIM) and Spinal and Bulbar Norris scores were recorded every 3 months. There was a significant difference between the two groups with respect to FIM scores (P<0.03), but not Barthel scores (P<0.8). A slower clinical course (Spinal Norris score P<0.02) and a significant difference in the slope of the RFT (P<0.008) were observed in the treated group, suggesting that exercise may be beneficial in ALS patients once Bipap is used to control peripheral and muscle oxygenation.

Efficacy and compliance with noninvasive positive pressure ventilation in patients with chronic respiratory failure

STUDY OBJECTIVES

Previous studies have shown the acute effects of noninvasive positive pressure ventilation (NPPV) in chronic respiratory failure; however, information on the chronic effects of NPPV is limited. We examined the acute and chronic effects of NPPV on gas exchange, functional status, and respiratory mechanics in patients with chronic respiratory failure related to restrictive ventilatory disorders or COPD.

DESIGN

Descriptive analysis of prospectively collected clinical data.

SETTING

Inpatient noninvasive respiratory care unit and outpatient clinic of university hospital.

PATIENTS

Forty patients with chronic respiratory failure (20 with severe COPD and 20 with restrictive ventilatory disorders).

INTERVENTIONS AND MEASUREMENTS

All patients were admitted to a noninvasive respiratory care unit for 20 +/- 3 days for inpatient evaluation consisting of medical treatment, rehabilitation, and NPPV evaluation and instruction. NPPV was titrated via a ventilatory support system (BiPAP; Respironics Inc; Monroeville, PA) or a portable volume ventilator (PLV 102; Lifecare, Inc; Boulder, CO) to achieve a > or = 20% increase in baseline minute ventilation while monitoring gas exchange, expired volume, and clinical evidence of a decrease in the patient's work of breathing.

RESULTS

The patients' mean age (+/- SD) was 65 +/- 9.7 years, and there was a 3:1 female:male predominance. In the noninvasive respiratory care unit, 36 patients used NPPV for 7.31 +/- 0.26 h/night. Four patients (three with COPD, one with restrictive disorder) withdrew from the study during the 3-week inpatient stay because they could not tolerate NPPV. Six patients (5 with COPD, 1 with restrictive disorder) used a portable volume ventilator and 34 patients used BiPAP (15 with COPD, 19 with restrictive disorders). At discharge, compared with at admission, daytime PaO2/fraction of inspired oxygen (FIO2) increased (327 +/- 10 vs 283 +/- 13 mm Hg; p = 0.01), PaCO2 was reduced (52 +/- 2 vs 67 +/- 3 mm Hg; p = 0.0001), and functional score increased (4.76 +/- 1.16 vs 2.7 +/- 1.64 arbitrary units (AUs); p < 0.01). Six months after discharge, improvements in PaO2/FIO2 (317 +/- 10 vs 283 +/- 13; p = 0.05), PaCO2 (52 +/- 2 vs 67 +/- 3 mm Hg; p = 0.0001), and functional score (5.66 +/- 0.41 vs 2.7 +/- 0.3 AUs; p < 0.001) were maintained compared with admission values. FVC, FEV1, and maximum inspired and expired mouth pressures were unchanged before and after long-term NPPV. Ten patients (7 with COPD, 3 with restrictive disorders) discontinued NPPV at 6 months, and 3 progressed to tracheostomy. The remaining 26 patients continued to use NPPV at the 6-month follow-up. They claimed to use NPPV for 7.23 +/- 0.24 h/night, but logged metered use was 4.5 +/- 0.58 h/night. Problems that required adjustment in either the mask (36%) or ventilator source (36%) included mask leaks (43%), skin irritation (22%), rhinitis (13%), aerophagia (13%), and discomfort from mask headgear (7%).

CONCLUSION

NPPV acutely and chronically improves gas exchange and functional status in patients with chronic respiratory failure, but a significant number of patients do not tolerate NPPV on a chronic basis. Comprehensive follow-up is required to correct problems with NPPV and ensure optimal patient compliance.

Mechanical ventilation as a bridge to lung transplantation

Data describing the use of ventilation as a bridge to lung transplantation are scant. However, data from the International Registry suggest that patients who are ventilated at the time of transplantation are at increased risk. The decision to offer invasive ventilatory support to a lung transplant candidate with acute respiratory failure should be individualized and based on variables that include likelihood of expeditious transplantation, and the presence of a reversible superimposed process. A trial of NPPV is justified in patients who present in acute respiratory failure, but is more likely to be successful in patients with hypercapnia and chronic airway obstruction. Lung transplant candidates with chronic respiratory insufficiency secondary to obstructive airway disease are at increased risk of acute respiratory failure, and a trial of NPPV might be considered on an individual basis after maximization of conventional medical therapy. More research in this area is necessary to further define the roles of both invasive and noninvasive ventilation as bridge therapy to lung transplantation.

Non-invasive ventilation in the management of respiratory failure

Non-invasive positive pressure ventilation (NIPPV) has been used increasingly to treat various forms of respiratory failure, with benefits in terms of gas exchange improvement, avoidance of endotracheal intubation and a decreased mortality. This review will focus on the recent developments and recommendations in the use of NIPPV in the treatment of acute and chronic respiratory failure, the methodology in the application of NIPPV, and briefly on its proposed mechanism of action.

Efficacy of nocturnal nasal ventilation in stable, severe chronic obstructive pulmonary disease during a 3-month controlled trial

OBJECTIVE

To evaluate the efficacy of nocturnal nasal ventilation (NNV) in patients with rigidly defined, severe but stable chronic obstructive pulmonary disease (COPD) and hypercapnia.

DESIGN

By randomization, eligible patients were assigned to an active or a sham treatment arm. Data from these two groups were analyzed statistically.

MATERIAL AND METHODS

Initially, 35 patients with severe COPD (forced expiratory volume in 1 second [FEV1] of less than 40% predicted) and daytime hypercapnia (arterial carbon dioxide tension [PaCO2] of more than 45 mm Hg) were enrolled in a 3-month NNV trial. After a minimal observation period of 6 weeks, 13 patients were judged to be clinically stable and were randomized to NNV (N = 7) or sham (N = 6) treatment, consisting of nightly use of a bilevel positive airway pressure (PAP) device set to deliver an inspiratory pressure of either 10 or 0 cm of water (H2O). The device was used in the spontaneous or timed mode and set to a minimal expiratory pressure of 2 cm H2O. Patients underwent extensive physiologic testing including polysomnography and were introduced to the bilevel PAP system during a 2.5-day hospital stay.

RESULTS

The NNV and sham treatment groups were similar in mean age (71.0 versus 66.5 years), PaCO2 (54.7 versus 48.5 mm Hg), and FEV1 (0.62 versus 0.72 L). Only four of seven patients in the NNV group were still using the bilevel PAP device at the completion of the trial, as opposed to all six patients in the sham group. Only one patient had a substantial reduction in PaCO2 - from 50 mm Hg at baseline to 43 mm Hg after 3 months of NNV. He declined further NNV treatment with bilevel PAP. Sham treatment did not lower PaCO2. Lung function, nocturnal oxygen saturation, and sleep efficiency remained unchanged in both groups.

CONCLUSION

Disabled but clinically stable patients with COPD and hypercapnia do not readily accept and are unlikely to benefit from NNV.

Financial implications of noninvasive positive pressure ventilation (NPPV)

Noninvasive positive pressure ventilation (NPPV) is effective in the treatment of acute and chronic respiratory failure. However, the costs and financial balance between costs and diagnosis-related group (DRG) reimbursement for patients with moderate to severe respiratory failure treated with NPPV are unknown. We examined the costs and DRG reimbursement for 27 patients receiving Medicare referred with moderately severe respiratory failure for NPPV to the ventilator rehabilitation unit (VRU) at Temple University Hospital. This unit is one of four Health Care Financing Administration chronic ventilator-dependent demonstration sites that evaluates patients for NPPV, instructs them in home NPPV use, emphasizes rehabilitation, and uses strict cost accounting methods. Nineteen patients were treated with NPPV in the ICU and then referred to the VRU, and 8 patients were directly admitted for NPPV to the VRU. Patients were (mean +/- SE) 69 +/- 9 years age, 14 had severe COPD, and 13 had various restrictive disorders. All were hypercapneic at the time of hospital admission (restrictive 60 +/- 15; obstructive 67 +/- 3 mm Hg, PaCO2) with impaired lung mechanics and limited functional status. Patients averaged 8 +/- 15 days in the ICU, or 8 +/- 4.7 days on the medical floor prior to VRU transfer. The VRU length of stay averaged 20 +/- 18 days, for a total length of stay of 29 +/- 21 days. After implementation of NPPV, all patients had an improvement in gas exchange while spontaneously breathing and functional status that was maintained in follow-up. At 1 and 2 years of follow-up, 74% and 63% of patients were alive, respectively. Eleven patients were admitted with DRG 475 (respiratory system diagnosis with ventilator support); however, 16 of 27 patients were admitted across five different non-475 DRG codes with reimbursement rates ranging from $2,673 to $4,215. After DRG and outlier reimbursement, a total deficit of $261,948 remained (average deficit $9,701 per patient). However, individual patient deficits ranged from $1,113 to $32,892. Eighty-two percent of patients treated with NPPV incurred substantial financial losses that were underreimbursed across all assigned DRGs, including DRG 475, the highest-weighted DRG. We conclude that patients with moderate to severe respiratory failure receiving NPPV demonstrate an improvement in functional status and gas exchange that is maintained in follow-up. In addition, patients treated with NPPV incur high costs that are currently underreimbursed by the present DRG system. Newer DRG payment scales that recognize NPPV as specific treatment should be implemented.

Severe hypercapnia after low-flow oxygen therapy in patients with neuromuscular disease and diaphragmatic dysfunction

OBJECTIVE

To increase the general awareness of the possible exacerbation of hypercapnia by the administration of low-flow oxygen in patients with neuromuscular disorders.

DESIGN

We retrospectively reviewed the medical records of 118 consecutive adult patients with a diagnosis of neuromuscular disease who underwent phrenic nerve conduction studies during a 5-year period, and we analyzed pulmonary function data for 8 patients who underwent arterial blood gas studies before and after the administration of low-flow oxygen.

MATERIAL AND METHODS

In the eight patients with neuromuscular disease and diaphragmatic dysfunction (three with polymyositis, three with amyotrophic lateral sclerosis or nonspecific motor neuron disease, and one each with inflammatory motor neuropathy and chronic poliomyelitis), we analyzed the response of the arterial carbon dioxide tension (PaCO2) after low-flow supplemental oxygen therapy (0.5 to 2 L/min). Linear analysis was used to attempt to find correlations between respiratory variables and the PaCO2 response after oxygen therapy.

RESULTS

For the overall study group, the mean PaCO2 increased 28.2 +/- 23.3 torr after low-flow oxygen treatment; in five patients, it increased by 27 torr or more. Four patients who were subsequently treated with nocturnal assisted ventilation were able to use supplemental oxygen during the day with less severe hypercapnia. Statistical analysis failed to reveal specific correlations between increased PaCO2 values after oxygen therapy and any respiratory variables.

CONCLUSION

In patients with neuromuscular disease and diaphragmatic dysfunction, even low-flow supplemental oxygen should be administered with caution, and assisted ventilation should be strongly considered as an initial intervention.

Nasal intermittent positive pressure ventilation. Analysis of its withdrawal

Nasal intermittent positive pressure ventilation (NIPPV) applied during sleep has been demonstrated to be useful in the treatment of restrictive thoracic diseases (RTD). The purpose of this study was to evaluate the repercussions of a withdrawal period from NIPPV of 15 days. This would be sufficient time for patients to go on trips without the respirator. It was hypothesized that once daytime improvement was achieved and was stable, it could be maintained for this period of time. Five volunteer patients with severe RTD who had been receiving treatment with nocturnal NIPPV for at least 2 months before and who had improved at least 5 mm Hg in daytime PO2 and PCO2 were included in the study. No significant differences were disclosed clinically or with arterial blood gas levels, spirometry results, lung volumes, airway resistances, or maximal muscle pressures 15 days following the withdrawal. However, in the sleep studies, a severe worsening of gas exchange was observed, mainly during rapid eye movement (REM) sleep, as well as a trend toward a more disturbed sleep pattern and more important alterations in cardiac rhythm. Consequently, withdrawing the treatment with nocturnal NIPPV cannot be recommended, at least for this particular removal period. Moreover, alterations in daytime gas exchange were found to originate in those produced during REM sleep through the blunting of the respiratory center to CO2. The NIPPV obstructs this mechanism, preventing the deterioration of gas exchange during sleep.

Efficacy of a new full face mask for noninvasive positive pressure ventilation

Previous studies have shown that noninvasive positive pressure ventilation (NPPV) improves gas exchange in acute and chronic respiratory failure. However, some patients are unable to tolerate NPPV due to air leaks around the mask, facial discomfort, and claustrophobia. A new mask that covers the entire face (Total, Respironics, Monroeville, Pa), attempts to overcome these obstacles. We studied the efficacy of NPPV via the Total face mask (TFM) in nine patients with chronic respiratory failure. In three patients, respiratory failure was due to chronic obstructive lung disease, and in six patients, it was secondary to restrictive disorders. None of the patients were previously able to tolerate NPPV via nasal (N) or nasal-oral (NO) masks. At baseline, all patients had impaired gas exchange with low PaO2/FIO2 (241 +/- 14), elevated PaCO2 (79 +/- 5 mm Hg), and poor functional status (1.89 +/- 1.45, on a scale of 1 to 7). After NPPV in the hospital for 7.1 +/- 1.5 h per night for 22 +/- 26 days, the PaCO2 fell to 59 +/- 3 mm Hg, and the PaO2/FIO2 rose to 304 +/- 27. Following nocturnal NPPV via the TFM for 6.7 +/- 1.5 h a night 6 +/- 5 weeks after hospital discharge, sustained improvements in PaCO2 (58 +/- 3 mm Hg, p < 0.05), PaO2/FIO2 (304 +/- 18), and functional status (5.38 +/- 1.06, p < 0.05) were observed. In four patients, measurements of respiratory rate, tidal volume, minute ventilation, dyspnea, discomfort with the face mask, and mask and mouth leaks were made during 30-min sessions of NPPV applied at constant levels via all three masks (N, NO, TFM). Discomfort with the face mask (0.38 +/- 0.18 vs 1.44 +/- 0.34 vs 2.38 +/- 0.32, p < 0.05) and mask leaks (0.44 +/- 0.18 vs 1.89 +/- 0.39 vs 1.89 +/- 0.35, p < 0.05) were least during NPPV via TFM compared with the N or NO masks, respectively. Moreover, expired tidal volume was highest (804 +/- 10 vs 498 +/- 9 vs 537 +/- 13 ml, p < 0.05) and PaCO2 lowest (51 +/- 2 vs 57 +/- 2 vs 58 +/- 3, p < 0.05) during NPPV via the TFM compared with N or NO masks. We conclude that NPPV delivered via a Total mask ensures a comfortable, stable patient-mask interface and improves gas exchange in selected patients intolerant of more conventional N or NO masks.

Accuracy of end-tidal and transcutaneous PCO2 monitoring during sleep

STUDY OBJECTIVE

Although it is intuitively desirable, the measurement of arterial carbon dioxide tension (PaCO2) during diagnostic polysomnography and nocturnal trials of positive pressure therapy is invasive and potentially expensive. The accuracy of end-tidal carbon dioxide tension (PETCO2) and transcutaneous carbon dioxide (tcPCO2) monitoring in these contexts has not been systematically evaluated. This investigation was undertaken to evaluate the accuracy of PETCO2 and tcPCO2 in patients undergoing polysomnography.

METHODS AND PROCEDURES

Values of PETCO2 were compared with PaCO2 in 19 patients spontaneously breathing room air (condition 1), in 13 patients receiving supplemental oxygen via nasal cannula (condition 2), and in 22 patients receiving nocturnal positive pressure ventilatory assistance (all but one with continuous positive airway pressure or bilevel positive airway pressure) (condition 3). The accuracy of tcPCO2 monitoring during sleep was also examined by comparing tcPCO2 values with simultaneously recorded PaCO2 values obtained during sleep in patients undergoing nocturnal polysomnography. Data were collected using three commercially available brands of tcPCO2 monitors (capnograph R, n = 17 patients; capnograph S, n = 17; and capnograph N, n = 15).

RESULTS

Accuracy of PETCO2--There was significant scatter in the PaCO2 vs PETCO2 relationship such that only 23 percent of the variability in PaCO2 was explained by variation of PETCO2 during condition 1 and only 15 percent and 20 percent of the variability in PaCO2 was explained by variation of PETCO2 during conditions 2 and 3, respectively. 21.3 percent of patients had average PETCO2 values in error by > 10 mm Hg during condition 1, while during conditions 2 and 3, 46.2 and 63.7 percent of patients had average values in error by > 10 mm Hg, respectively. Accuracy of tcPCO2--While capnographs S and N generally overestimated PaCO2 with a wide scatter, capnograph R tended to have offsetting overestimations and underestimations of PaCO2 with a wide scatter. With each capnograph, a relatively small portion of the variability of the PaCO2 was explained by variability of the tcPCO2 (r2 = 0.2, 0.45 and 0.64 for capnographs S, N, and R, respectively). Across the three capnographs, 43.1 to 66.7 percent of measurements were in error by > 10 mm Hg, and 5 to 20 percent of measurements reflected errors > 20 mm Hg. There was no consistent relationship between the tcPCO2 error and the level of PaCO2, nor was the tcPCO2 error consistent in individual patients. There was no relationship between tcPCO2 accuracy and body mass index.

CONCLUSION

Neither PETCO2, measured within a face mask, nor tcPCO2 is a consistently accurate reflection of PaCO2. This limits the utility of these variables in monitoring patients during diagnostic and therapeutic sleep studies, and in particular, during trials of nocturnal ventilatory assistance where adequate levels of support are to be established and unacceptable hyperventilation and respiratory alkalosis must be recognized.

Respiratory muscles and ventilatory failure: 1993 perspective

Some conditions that predispose to ventilatory failure increase the work of breathing (chronic obstructive pulmonary disease [COPD], obesity, kyphoscoliosis), whereas others cause severe respiratory muscle weakness. Specific reasons for muscle weakness include critical illness (electrolyte imbalance, acidemia, shock, sepsis), chronic illness (poor nutrition, cachexia), and neuromuscular diseases. Inspiratory muscle weakness from mechanical disadvantage to the diaphragm is characteristic of asthma and COPD. The increased work of breathing combined with muscle weakness increases the pressure needed to inspire a breath and decreases maximal inspiratory pressure. When this pressure exceeds 0.4, dyspnea and inspiratory muscle fatigue ensue. One way to lower this pressure and avert fatigue is to lower the tidal volume. Ventilatory drive is high, not low, in ventilatory failure. Concomitant shortening of inspiration and breath duration cause the small tidal volume and increased respiratory rate. Gas exchange is compromised by ventilation/perfusion imbalance, and the ratio of dead space to tidal volume is also increased by rapid, shallow breathing. Reduction in tidal volume minimizes dyspnea, but the small tidal volume is inadequate for gas exchange. Acute treatment of respiratory muscle failure involves respiratory muscle rest through mechanical ventilation and removal of noxious influences (infection, metabolic disarray), whereas chronic treatment involves rebuilding the contractile apparatus by nutritional repletion and training.

Chronic respiratory failure due to bilateral vocal cord paralysis managed with nocturnal nasal positive pressure ventilation

A patient with bilateral vocal cord paralysis developed chronic respiratory failure. Treatment with nocturnal inspiratory positive airway pressure via nasal mask improved symptoms and reduced hypercapnia.

Restrictive chest bellows disease and frontometaphyseal dysplasia

We describe a patient with frontometaphyseal dysplasia (FMD), restrictive chest bellows disease, hypercapnic respiratory failure, and cor pulmonale. Treatment with intermittent supplemental oxygen, nocturnal nasal volume ventilation, and posture modification was successful in partial resolution of chronic hypoventilation and excessive daytime somnolence.

Sleep-disordered breathing in patients with Duchenne muscular dystrophy using negative pressure ventilators

We studied the occurrence of nocturnal disordered breathing events and O2 desaturations in 12 patients with late-stage Duchenne muscular dystrophy (DMD) using negative pressure ventilators. We also assessed the effects of O2 supplementation and nasal continuous positive airway pressure (CPAP) on disordered breathing events in selected patients and examined sleep quality in a small subgroup. Average age was 23 + 2 years and FVC was 293 + 33 ml. Eleven of the 12 patients had more than five disordered breathing events per hour during nocturnal monitoring, and the lowest O2 saturation was < 85 percent in nine patients. Nasal O2 (2 L/min) during negative pressure ventilation in four patients did not alter the frequency of disordered breathing events, prolonged the mean and maximum durations of events, and failed to eliminate severe O2 desaturations in two patients. Nasal CPAP was used in two patients during negative pressure ventilation and completely eliminated disordered breathing events in both. Overnight polysomnography during negative pressure ventilation in three patients demonstrated frequent awakenings that fell in frequency following elective tracheostomy in two patients and use of nasal CPAP in one. We conclude that negative pressure ventilation in patients with late-stage DMD is associated with frequent disordered breathing events and severe O2 desaturations in many patients. Concomitant use of O2 supplementation may prolong the events, but a switch to positive pressure ventilation or addition of nasal CPAP is effective therapy.

Pulmonary Manifestations of Neurological Disease

Breathing is a complicated act that requires sophisticated control mechanisms. The nervous system coordinates 3 fundamentally important components of respiration. The central nervous system has a central pattern generator that, along with appropriate feedback mechanisms, establishes both the resiratory rate and the depth of respirations. The peripheral nervous system facilitates transmission of these respiratory commands to the ventilatory muscles. The nervous system also contributes to the control of airway size. Laryngeal function is coordinated with inspiration, and local nerves in the lung have a major role in determining bronchial patency. Finally, the nervous system acts in incompletely understood ways to regulate perfusion of the lungs and to match local pulmonary blood flow with ventilation. Failure of the nervous system to adequately control these 3 different aspects of respiration may result in lifethreatening illness. Understanding how the nervous system affects control of ventilation, airway patency, and pulmonary perfusion therefore will enable intensivists to recognize and manage the pulmonary complications of neurological disease.