Twelve year clinical study of patients with hypoxic cor pulmonale given long term domiciliary oxygen therapy

Baseline Level and Reduction in PaCO2 are Associated with the Treatment Effect of Long-Term Home Noninvasive Positive Pressure Ventilation in Stable Hypercapnic Patients with COPD: A Systematic Review and Meta-Analysis of Randomized Controlled Trials

Purpose

Patients and Methods

Results

Conclusion

Lack of Medical Criteria for Long-Term Oxygen Therapy Usage According to International Guidance in Outpatients With Chronic Hypoxemia

Background

Benefits of long-term oxygen therapy (LTOT) have been observed in hypoxemic respiratory patients. Reports have shown the lack of observance among healthcare professionals of LTOT. Thus, this study aimed to determine the demographic characteristics and observance of the medical indication of LTOT according to the international guidelines.

Methodology

A cross-sectional study was conducted on patients who attended the Medical Unit in Aguascalientes, Mexico to re-evaluate the need for LTOT. Data are presented as mean ± standard deviation. Statistical analyses were performed using the chi-square test or unpaired t-tests. P-values of <0.05 were considered statistically significant.

Results

From 813 outpatients attended to re-evaluate whether they met the medical criteria to use LTOT, 93 outpatients were excluded, and the remaining 714 outpatients were enrolled. The mean age of the patients was 70.0 ± 15.1 years, with a female gender predominance (59.1 %). The mean PaO₂ level in room air was 7.9 ± 2.3 kPa. Hemoglobin and hematocrit levels were 14.9 ± 4.1 g/dL and 44.7 ± 8.4%, respectively. The mean levels of PaO₂ were higher in female patients (8.1 ± 2.5 kPa vs. 7.6 ± 1.9 kPa; p = 0.01). The most common diagnosis was chronic obstructive pulmonary disorder (60.5%). Moreover, the specialty that most indicated the use of LTOT was pulmonology (57.8%); however, 36.8% of patients who used LTOT did not have any criteria according to international guidelines.

Conclusions

Although a significant percentage of patients do not use LTOT correctly, the most important finding is that the medical indication of LTOT by physicians is not always correct, leading to an excessive prescription of oxygen.

Treatment of pulmonary hypertension associated with COPD: a systematic review

Chronic obstructive pulmonary disease-associated pulmonary hypertension (COPD-PH) is an increasingly recognised condition which contributes to worsening dyspnoea and poor survival in COPD. It is uncertain whether specific treatment of COPD-PH, including use of medications approved for pulmonary arterial hypertension (PAH), improves clinical outcomes. This systematic review and meta-analysis assesses potential benefits and risks of therapeutic options for COPD-PH.

We searched Medline and Embase for relevant publications until September 2020. Articles were screened for studies on treatment of COPD-PH for at least 4 weeks in 10 or more patients. Screening, data extraction, and risk of bias assessment were performed independently in duplicate. When possible, relevant results were pooled using the random effects model.

Supplemental long-term oxygen therapy (LTOT) mildly reduced mean pulmonary artery pressure (PAP), slowed progression of PH, and reduced mortality, but other clinical or functional benefits were not assessed. Phosphodiesterase type 5 inhibitors significantly improved systolic PAP (pooled treatment effect −5.9 mmHg; 95% CI −10.3, −1.6), but had inconsistent clinical benefits. Calcium channel blockers and endothelin receptor antagonists had limited haemodynamic, clinical, or survival benefits. Statins had limited clinical benefits despite significantly lowering systolic PAP (pooled treatment effect −4.6 mmHg; 95% CI −6.3, −2.9).

This review supports guideline recommendations for LTOT in hypoxaemic COPD-PH patients as well as recommendations against treatment with PAH-targeted medications. Effective treatment of COPD-PH depends upon research into the pathobiology and future high-quality studies comprehensively assessing clinically relevant outcomes are needed.

The presence of PH in COPD patients is associated with worsening morbidity and mortality. These findings support guideline recommendations for LTOT in hypoxaemic COPD-PH patients as well as recommendations against treatment using PAH-targeted medications.https://bit.ly/3Al4rLb

Long-Term Oxygen Therapy

BACKGROUND

Long-term oxygen therapy (LTOT) is an established treatment for patients with chronic hypoxemia. Its scientific basis is derived mainly from two trials from the early 1980s that showed a survival advantage for patients with chronic obstructive pulmonary disease (COPD) treated with LTOT. Robust data are not available for other diseases associated with hypoxemia.

METHODS

This review is based on pertinent publications retrieved by a selective search in PubMed.

RESULTS

The use of LTOT for 15 to 16 hours per day (or, better, 24 hours per day) is recommended in current guidelines for patients with chronic hypoxemia (PaO2 ≤ 55 mm Hg) because this treatment was found to be associated with a lower mortality rate compared to no LTOT (33% vs. 55%, p <0.05) based on data from the early 1980s. In the short term, oxygen administration to a hypoxemic patient can improve oxygen saturation by nine percentage points and improve physical performance to a clinically relevant extent (6-minute walking test: + 37 m, p <0.001). The available data do not support the use of LTOT for normoxemic patients. LTOT should only be administered for strict indications, in accordance with the guidelines, and only in a form suitable for the individual patient. Skin burns can occur as a side effect of LTOT because of contact explosions with any type of fire.

CONCLUSION

The acquisition of further robust data would be desirable, particularly with respect to patient-relevant outcome parameters including quality of life, performance status, and mortality. Moreover, the German guidelines on oxygen therapy need to be updated.

Low-dose oxygen therapy in COPD patients: are there any radiation-like risks?

PURPOSE OF REVIEW

Low-dose oxygen (LDO) supplementation is used by millions of COPD patients worldwide. The therapeutic benefits of LDO supplementation are well known. There are also several concerns regarding the potential for cellular harm from LDO in COPD patients. This review summarizes the current arguments and evidence pertaining to this important topic.

RECENT FINDINGS

LDO therapy has been used in COPD patients for more than 50 years. Over the years, data from randomized controlled trials has confirmed that LDO provides survival benefit in COPD patients with severe hypoxemia. Recent data, however, show that LDO does not provide any morality benefit for patients with a less severe degree of hypoxemia. There are several theoretical concerns regarding use of LDO in COPD patients, including radiation-like cellular risks because of oxygen toxicity. However, none of these have been validated in human clinical trials and remain somewhat peripheral to the clinician deciding whether or not to initiate LDO in a hypoxemic COPD patient.

SUMMARY

There is high-quality evidence that LDO is both well tolerated and highly efficacious for patients with COPD. There are several theoretical concerns regarding damage from oxygen free radicals from LDO in COPD patients. However, none of these have been validated or confirmed in human clinical trial data. Thus, the benefits of LDO clearly outweigh the risks from any theoretical concerns about oxygen toxicity.

Continuous remote monitoring of COPD patients-justification and explanation of the requirements and a survey of the available technologies

Remote patient monitoring should reduce mortality rates, improve care, and reduce costs. We present an overview of the available technologies for the remote monitoring of chronic obstructive pulmonary disease (COPD) patients, together with the most important medical information regarding COPD in a language that is adapted for engineers. Our aim is to bridge the gap between the technical and medical worlds and to facilitate and motivate future research in the field. We also present a justification, motivation, and explanation of how to monitor the most important parameters for COPD patients, together with pointers for the challenges that remain. Additionally, we propose and justify the importance of electrocardiograms (ECGs) and the arterial carbon dioxide partial pressure (PaCO2) as two crucial physiological parameters that have not been used so far to any great extent in the monitoring of COPD patients. We cover four possibilities for the remote monitoring of COPD patients: continuous monitoring during normal daily activities for the prediction and early detection of exacerbations and life-threatening events, monitoring during the home treatment of mild exacerbations, monitoring oxygen therapy applications, and monitoring exercise. We also present and discuss the current approaches to decision support at remote locations and list the normal and pathological values/ranges for all the relevant physiological parameters. The paper concludes with our insights into the future developments and remaining challenges for improvements to continuous remote monitoring systems. Graphical abstract ᅟ.

Pharmacological Management of People Living with End-Stage Chronic Obstructive Pulmonary Disease

Supportive care and pharmacological treatment can improve the quality of life of people with end-stage chronic obstructive pulmonary disease (COPD) who cope on a daily basis with substantial physical, psychological, social and spiritual morbidity. Smoking cessation is the only intervention that reduces the rate of progression of COPD, but evidence-based drug treatments and non-pharmacological strategies can relieve symptoms and reduce the impact of exacerbations. People with severe COPD live with increasingly troublesome breathlessness and other symptoms such as fatigue, pain, sputum production and weight loss. As breathlessness increases, treatment is stepped up from short-acting to long-acting bronchodilators supplemented by non-pharmacological interventions such as pulmonary rehabilitation. Opiates relieve breathlessness, and referral to a multidisciplinary breathlessness service is an option for those with intractable symptoms. Other smoking-related conditions, such as coronary heart disease and lung cancer as well as depression and anxiety are common and should be treated with conventional pharmacotherapy. Acute exacerbations become more frequent and more severe as the disease reaches end-stage. Inhaled corticosteroids in combination with long-acting bronchodilators can reduce the frequency of exacerbations, and supported self-management aims to facilitate timely treatment of deterioration. Palliative care services have traditionally been predicated on identifying people with end-stage disease-a model that does not resonate with the unpredictable, relapsing trajectory of COPD. Approaches to care that promote a flexible approach to palliation alongside curative care could do much to improve the burden of living with severe COPD.

Home oxygen therapy: evidence versus reality

INTRODUCTION

LTOT is a well-established treatment option for hypoxemic patients. Scientific evidence for its benefits of LTOT dates back to the 1980s, when two randomized controlled trials showed prolonged survival in COPD-patients undergoing LTOT for at least 15 hours/day. In contrast, the potential benefits of LTOT in non-COPD-patients has not been well researched and the recommendations for its application are primarily extrapolated from trials on COPD-patients. Recently, a large trial confirmed that COPD-patients who don't meet classic indication criteria, and have moderate desaturation at rest or during exercise, do not benefit from oxygen therapy. Also the significant technical evolution of LTOT devices has improved its application. Areas covered: A literature research was performed in pubmed regarding home oxygen therapy (terms: LTOT, ambulatory oxygen therapy, short burst oxygen therapy, nocturnal oxygen therapy). Expert commentary: LTOT proved a survival benefit for COPD patients about 30 years ago. Whether the results of these trials are still valid for patients under modern treatment guidelines remains unknown. Nevertheless, the classic indication criteria for LTOT still persist in guidelines, since there is a lack of updated evidence for the effects of LTOT in more severe hypoxemic patients.

Two-year mortality in survivors of acute exacerbations of chronic obstructive pulmonary disease: A North Indian study

OBJECTIVES

Data about long-term mortality of Indian patients following acute exacerbation of chronic obstructive pulmonary disease (AECOPD) are scant. We set out to study the 2-year mortality in north Indian patients following discharge after AECOPD.

MATERIALS AND METHODS

One hundred and fifty-one (96 male) patients admitted for AECOPD and discharged were followed for 2 years at 3, 6, 12, 18, and 24 months for mortality. Statistical analysis was performed to identify risk factors associated with mortality.

RESULTS

Sixty (39.7%) of the 151 recruited died during the 24 months of follow-up, 30 (19.8%) at 3-month, 43 (28.5%) at 6-month, 49 (32.4%) at 1-year, 55 (36.4%) at 18-month, and 60 (39.7%) at 2 years. There was no mortality in Global Initiative for Chronic Obstructive Lung Disease (GOLD) Stage I (0 of 6 cases), whereas it was 12.3% (n = 8 of 65 patients) in GOLD Stage II, 41.7% (n = 15 of 36 cases), in GOLD Stage III, and 84.1% (n = 37 of 4 cases), of patients with GOLD Stage IV. Mortality was associated with 6-min walk distance, oxygen saturation, low body mass index, history of congestive heart failure, and St. George Respiratory Questionnaire score.

CONCLUSION

Indian patients discharged after AECOPD have a high 2-year mortality. Measures to reduce the frequency of exacerbations need to be routinely adopted in patients with COPD.

Saudi Guidelines on the Diagnosis and Treatment of Pulmonary Hypertension: Pulmonary hypertension due to lung diseases and/or hypoxia

Chronic lung diseases are common causes of pulmonary hypertension. It ranks second after the left heart disease. Both obstructive and restrictive lung diseases are know to cause pulmonary hypertension.

The pathophysiology of the disease is complex, and includes factors affecting the blood vessels, airways, and lung parenchyma. Hypoxia and the inhalation of toxic materials are another contributing factors. Recent guidelines have further clarified the association between pulmonary hypertension and chronic lung disease and made general guidelines concerning the diagnosis and management.

In this article, we will provide a detailed revision about the new classification and give general recommendations about the management of pulmonary hypertension in chronic lung diseases.

Hypo- and hypercapnia predict mortality in oxygen-dependent chronic obstructive pulmonary disease: a population-based prospective study

BACKGROUND

The prognostic role of the arterial blood gas tension of carbon dioxide (PaCO2) in severe Chronic Obstructive Pulmonary Disease (COPD) remains unknown. The aim of this study was to estimate the association between PaCO2 and mortality in oxygen-dependent COPD.

METHODS

National prospective study of patients starting long-term oxygen therapy (LTOT) for COPD in Sweden between October 1, 2005 and June 30, 2009, with all-cause mortality as endpoint. The association between PaCO2 while breathing air, PaCO2 (air), and mortality was estimated using Cox regression adjusted for age, sex, arterial blood gas tension of oxygen (PaO2), World Health Organization performance status, body mass index, comorbidity, and medications.

RESULTS

Of 2,249 patients included, 1,129 (50%) died during a median 1.1 years (IQR 0.6-2.0 years) of observation. No patient was lost to follow-up. PaCO2 (air) independently predicted adjusted mortality (p < 0.001). The association with mortality was U-shaped, with the lowest mortality at approximately PaCO2 (air) 6.5 kPa and increased mortality at PaCO2 (air) below 5.0 kPa and above 7.0 kPa.

CONCLUSION

In oxygen-dependent COPD, PaCO2 (air) is an independent prognostic factor with a U-shaped association with mortality.

VCSEL based, wearable, continuously monitoring pulse oximeter

We present the development of a novel pulse oximeter based on low power, low cost, Vertical Cavity Surface Emitting Laser (VCSEL) technology. This new design will help address a need to perform regular measurements of pulse oximetry for patients with chronic obstructive pulmonary disease. VCSELs with wavelengths suitable for pulse oximetry were developed and packaged in a PLCC package for a low cost solution that is easy to integrate into a pulse oximeter design. The VCSELs were integrated into a prototype pulse oximeter that is unobtrusive and suitable for long term wearable use. The prototype achieved good performance compared the Nonin Onyx II pulse oximeter at less than one fifth the weight in a design that can be worn behind the ear like a hearing aid.

Long-term oxygen therapy

Long-term oxygen therapy (LTOT) has been shown to reduce pulmonary hypertension and improve survival in patients with chronic obstructive pulmonary disease and resting hypoxemia (reduced arterial partial pressure of oxygen ≤55 mmHg). However, the benefit of its use for chronic pulmonary diseases other than chronic obstructive pulmonary disease as well as for nonpulmonary conditions is debatable. Its role in patients with mild hypoxemia (reduced arterial partial pressure of oxygen >55 mmHg at rest) is presently being investigated in the LOTT. A meta-analysis of four controlled trials reporting the role of LTOT in patients with either nocturnal desaturation or daytime moderate hypoxemia found no difference in survival between patients on LTOT than those without. Advances in oxygen delivery and conservation devices have made domiciliary oxygen therapy more practical and popular for patients. There still remain concerns with the actual compliance of therapy among the needy patients.

A novel extracorporeal CO(2) removal system: results of a pilot study of hypercapnic respiratory failure in patients with COPD

BACKGROUND

Hypercapnic respiratory failure in patients with COPD frequently requires mechanical ventilatory support. Extracorporeal CO2 removal (ECCO2R) techniques have not been systematically evaluated in these patients.

METHODS

This is a pilot study of a novel ECCO2R device that utilizes a single venous catheter with high CO2 removal rates at low blood flows. Twenty hypercapnic patients with COPD received ECCO2R. Group 1 (n = 7) consisted of patients receiving noninvasive ventilation with a high likelihood of requiring invasive ventilation, group 2 (n = 2) consisted of patients who could not be weaned from noninvasive ventilation, and group 3 (n = 11) consisted of patients on invasive ventilation who had failed attempts to wean.

RESULTS

The device was well tolerated, with complications and rates similar to those seen with central venous catheterization. Blood flow through the system was 430.5 ± 73.7 mL/min, and ECCO2R was 82.5 ± 15.6 mL/min and did not change significantly with time. Invasive ventilation was avoided in all patients in group 1 and both patients in group 2 were weaned; PaCO2 decreased significantly (P < .003) with application of the device from 78.9 ± 16.8 mm Hg to 65.9 ± 11.5 mm Hg. In group 3, three patients were weaned, while the level of invasive ventilatory support was reduced in three patients. One patient in group 3 died due to a retroperitoneal bleed following catheterization.

CONCLUSIONS

This single-catheter, low-flow ECCO2R system provided clinically useful levels of CO2 removal in these patients with COPD. The system appears to be a potentially valuable additional modality for the treatment of hypercapnic respiratory failure.

An arteriovenous fistula increases exercise capacity in patients with COPD

BACKGROUND

Supplemental oxygen usually increases exercise capacity in hypoxemic COPD, but some patients are refractory because of venous admixture. An arteriovenous fistula (AVF) with left-to-right shunt increases mixed venous oxygen content and cardiac output; therefore, this might improve arterial oxygen delivery. We hypothesized that creation of an AVF would therefore increase exercise capacity in severe COPD.

METHODS

We created an AVF in 12 patients with severe hypoxemic COPD: mean (SD) age, 66 (6) years; Pao(2), 57.5 (3.0) mm Hg, and FEV(1), 19% (8%) predicted. We measured 6-min walk distance (6MWD) while the subjects were breathing room air and again while they were breathing portable supplemental oxygen at baseline, 6 weeks, and 12 weeks after creation of an AVF in the iliofemoral region.

RESULTS

After surgery, the mean (SEM) 6MWD increased from 217 (63) m at baseline to 272 (18) m and 276 (25) m, 6 weeks and 12 weeks after surgery, respectively. Patients who walked > 54 m further while breathing supplemental oxygen at baseline (n = 5) increased 6MWD while breathing room air by 129 (34) m after 6 weeks (P = .02) and by 124 (29) m after 12 weeks (P = .004). Walking distance did not change in patients who did not have a clinically meaningful response to oxygen at baseline.

CONCLUSIONS

An iliofemoral AVF increased 6MWD patients with severe COPD, matching the improvement seen with supplemental oxygen. An initial response to supplemental oxygen predicted a therapeutic response to the AVF.

Predictors of first-year survival in patients with advanced COPD treated using long-term oxygen therapy

Little evidence-based guidance is available to aid clinicians in determining short-term prognoses in very severe COPD patients. Therefore, the present study was designed to provide a prospective assessment (1) of the mortality rates and (2) whether the baseline measurements may be determinants of 1-year mortality in hypoxemic COPD patients receiving long-term oxygen therapy (LTOT). Seventy-eight clinically stable patients with advanced COPD treated using LTOT were enrolled in a prospective cohort study.

OUTCOME VARIABLE

first-year mortality. Baseline measurements: categorical variables: age (<60 or > or = 60 years); gender; body mass index (<20 or > or = 20 kg/m(2)); fat-free mass (FFM) index (<16 [men] and <15 kg/m(2) [women]; baseline dyspnea index (BDI) (< or = 3 or >3); and corticosteroid use. Continuous variables: smoking history; lung function; FFM; fat mass; hemoglobin; hematocrit; arterial blood gases; forearm muscle strength; St. George's Respiratory Questionnaire (SGRQ); and comorbidity score. By the end of 1-year of follow-up, 12 patients (15.4%) had died. Kaplan-Meier curves showed that BDI < or = 3 was the only variable associated with higher mortality. Cox proportional hazards analysis revealed that lower PaO(2) and SpO(2), higher PaCO(2) and SGRQ scores were associated with reduced survival. In the multivariate analysis, BDI remained predictive of mortality (hazard ratio [HR], 0.50; 95% confidence interval [CI], 0.31-0.81), as did PaO(2) (HR, 0.49; 95% CI, 0.26-0.95). These data suggest that readily available parameters as dyspnea intensity and hypoxemia severity may be useful in predicting first-year survival rates in advanced COPD patients receiving LTOT.

Predictors of Survival in COPD Patients With Chronic Hypercapnic Respiratory Failure Receiving Noninvasive Home Ventilation

BACKGROUND

Patients with COPD and chronic hypercapnic respiratory failure (CHRF) are at high risk, and noninvasive ventilation at home is increasingly being used. Knowledge of prognostic parameters under these conditions is limited but may be clinically helpful and highlight the role of noninvasive ventilation.

METHODS

In 188 patients with COPD (mean +/- SD FEV1, 31.0 +/- 9.6% of predicted; PaCo2, 56.3 +/- 9.4 mm Hg) discharged from the hospital receiving NIV between July 1994 and July 2004, the prognostic value of body mass index (BMI), lung function, laboratory parameters, and blood gas levels was assessed by univariate and multivariate Cox regression analyses. Moreover, the impact of changes in risk factors on mortality assessed 6.7 +/- 2.8 months after the initiation of noninvasive ventilation was evaluated.

RESULTS

Overall, the mortality rate during follow-up (duration, 32.2 +/- 24.3 months) was 44.7%, with 1-year, 2-year, and 5-year survival rates of 84.0%, 65.3%, and 26.4%. Deaths resulted predominantly from respiratory causes (73.8%). Univariate regression analyses revealed age, BMI, hemoglobin, FEV1, specific airway resistance, residual volume (RV)/total lung capacity (TLC), pH, and base excess (BE) to be associated with prognosis (p < 0.01 each), whereas multivariate analysis identified only age, BMI, RV/TLC, and BE as independent predictors (p < 0.05). In patients at risk (BMI < 25 km/m2, RV/TLC >or= 73%, or BE >or= 9 mmol/L), changes in these predictors were also associated with survival.

CONCLUSIONS

In patients with COPD and CHRF, nutritional status, hyperinflation, and BE, which turned out to be reliable and consistent markers in CHRF, were independent prognostic factors for mortality. These data favor a multidimensional approach in these patients, including the use of noninvasive ventilation.

Sex Differences in Survival of Oxygen-dependent Patients with Chronic Obstructive Pulmonary Disease

RATIONALE

Chronic obstructive pulmonary disease (COPD) is a leading cause of death worldwide. The prevalence of COPD is rising among women and is approaching that of men, but it is not known if sex affects survival.

OBJECTIVES

To measure the survival differences between men and women with oxygen-dependent COPD.

METHODS

We conducted a 7-yr prospective cohort study of 435 outpatients with COPD (184 women, 251 men) referred for long-term oxygen therapy (LTOT) at two respiratory clinics in Sao Paulo, Brazil. Baseline data were collected on enrollment into oxygen therapy, when patients were clinically stable.

MEASUREMENTS

We examined the effect of sex on survival using Kaplan-Meier survival curves, and then used Cox proportional hazards models to control for potential confounders.

MAIN RESULTS

In unadjusted analyses, we observed a nonsignificant trend toward increased mortality for women (hazard ratio, 1.28; 95% confidence interval, 0.98-1.68; p = 0.07). After accounting for potential confounders (age, pack-years smoked, Pa(O(2)), FEV(1), body mass index), females were at a significantly higher risk of death (hazard ratio, 1.54; 95% confidence interval, 1.15-2.07; p = 0.004). Other independent predictors of death were lower Pa(O(2)) (p < 0.001) and lower body mass index (p < 0.05).

CONCLUSIONS

Among patients with COPD on LTOT, women were more likely to die than men.

Home oxygen therapy and cigarette smoking: a dangerous practice

Oxygen as a therapeutic agent is an important form of home therapy for hypoxic chronic obstructive pulmonary disease (COPD) and improved survival has been demonstrated in hypoxic COPD patients receiving continuous oxygen. However, some patients, despite dissuasion, continue to smoke and we describe the case of a patient on home oxygen who sustained a partial-thickness facial flash burn whilst engaged in this habit. A review is made of the literature, as also a comparison of all discovered cases of burns in home oxygen users, followed by a discussion of the implications of this potentially hazardous form of therapy.

Continuous oxygen monitoring--a better way to prescribe long-term oxygen therapy

STUDY OBJECTIVE

The purpose of this study was to determine if an oxygen prescription based on continuous oximetry monitoring, would result in an increased percentage of time spent within an SpO2 level between 88% and 92%.

METHODS

We conducted a prospective, cohort study in an outpatient, pulmonary setting in a tertiary care referral center, on 17 patients with stable chronic obstructive pulmonary disease (COPD) who had previously been prescribed long-term oxygen therapy. The patients were monitored for approximately 24h with a portable oximeter that recorded SpO2 and EKG readings. During the initial 24h of monitoring, the patients were on their previous oxygen prescription. Their oxygen prescription was then altered based on a predetermined protocol described below. The patients were then monitored for an additional 24h.

RESULTS

Sixteen patients completed the study. Based on the initial continuous oximetry, the median oxygen prescription was reduced from 2.5 to 1.2 L/min (P < 0.001). The oxygen prescription during exercise, rest, and sleep decreased from 3.0 +/- 0.9 to 1.8 +/- 1.3 L/min (P < 0.001), 2.2+/-0.4 to 0.8 +/- 0.7 L/min (P < 0.001), and 2.2 +/- 0.4 to 0.9 +/- 0.8 L/min (P < 0.001) respectively. After the oxygen prescription was adjusted, the percentage of the time that the SpO2 was between 88 and 92% increased from 24.8 +/- 21.7% to 52.8 +/- 25.0% (P = 0.001), but the percentage of time that the SpO2 was below 88% did not change significantly (2.8 +/- 6.1% to 4.3 +/- 8.1%).

CONCLUSIONS

This study demonstrates that an oxygen prescription based on continuous oximetry monitoring results in (1) a significant increase in the percentage of time that the SpO2 is between 88% and 92%, (2) a significant decrease in the amount of oxygen prescribed, (3) a slight increase in the amount of time that the SpO2 is below 88% that was not statistically significant.

Impact of long-term ventilation on patients' health status

Therapy and rehabilitation of common causes of respiratory-induced disability are directed towards a reduction of exacerbations, minimization of symptom severity, and improvement, or at least maintenance, of the patient's health. Unfortunately, these diseases are frequently complicated by chronic respiratory failure (CRF), which determines a rapid increase in the impact of the disease on the patient's daily life and well-being. Under such circumstances, the effect of therapy on a patient's health status and well-being represents the most important subjective outcome of treatment. An adequate assessment of patient's quality of life can only be obtained from the patients themselves; that is, it requires direct measurement through the use of valid and reliable questionnaires, whether generic or disease-specific. The St George's Respiratory Questionnaire and the Maugeri Foundation Respiratory Failure Questionnaire have been shown to be applicable and reliable in patients on long-term ventilation.

Outcome of Patients With Stable COPD Receiving Controlled Noninvasive Positive Pressure Ventilation Aimed at a Maximal Reduction of Paco2

STUDY OBJECTIVES

The role of noninvasive positive pressure ventilation (NPPV) has been well established in the treatment of acute hypercapnic respiratory failure due to COPD. However, evidence for a sustained improvement in blood gas levels and survival in patients with stable hypercapnic COPD following NPPV is still lacking. There is concern that this might be due to low inspiratory pressures of < 18 cm H2O used in previous studies, which thereby did not achieve a reduction of Pa(CO2). Therefore, the 2-year survival and changes in lung function and blood gas levels were analyzed in patients with stable hypercapnic COPD in whom controlled pressure-limited NPPV was titrated to achieve a maximal improvement in Pa(CO2).

DESIGN

Retrospective study between March 1997 and September 2003.

SETTING

General ward of a university hospital.

PATIENTS

Thirty-four consecutive patients with stable (mean pH 7.40 +/- 0.03) hypercapnic COPD (mean age, 63.4 +/- 9.7 years [+/- SD]; mean body mass index, 28.3 +/- 7.3 kg/m2).

MEASUREMENTS AND RESULTS

Daytime Pa(CO2) during spontaneous breathing decreased by 6.9 +/- 8.0 (95% confidence interval, - 9.9 to - 3.9), from 53.3 +/- 4.8 to 46.4 +/- 7.0 mm Hg (p < 0.001); while daytime Pa(O2) increased by 5.8 +/- 9.4 (95% confidence interval, 2.3 to 9.3), from 51.7 +/- 8.8 to 57.5 +/- 9.3 mm Hg (p = 0.002); and FEV1 increased by 0.14 +/- 0.16 (95% confidence interval, 0.08 to 0.20), from 1.03 +/- 0.54 to 1.17 +/- 0.59 L (p < 0.001) after 2 months of NPPV. This was achieved with mean inspiratory pressures of 27.7 +/- 5.9 cm H2O (range, 17 to 40 cm H2O) at a mean respiratory rate of 20.8 +/- 2.5 breaths/min (range, 14 to 24 breaths/min). The 2-year survival rate was 86%.

CONCLUSIONS

Controlled NPPV using a mean inspiratory pressure of 28 cm H2O is well tolerated over longer periods and can improve blood gas levels and lung function. Prospective, randomized controlled trials of high-intensity NPPV are required to evaluate its role in patients with stable hypercapnic COPD.

Survival of chronic hypercapnic COPD patients is predicted by smoking habits, comorbidity, and hypoxemia

STUDY OBJECTIVES

Chronic hypercapnia in patients with COPD has been associated with a poor prognosis. We hypothesized that, within this group of chronic hypercapnic COPD patients, factors that could mediate this hypercapnia, such as decreased maximum inspiratory mouth pressure (P(I(max))), decreased maximum expiratory mouth pressure (P(E(max))), and low hypercapnic ventilatory response (HCVR), could be related to survival. Other parameters, such as arterial blood gas values, airway obstruction (FEV1), body mass index (BMI), current smoking status, and the presence of comorbidity were studied as well.

METHODS

A cohort of 47 chronic hypercapnic COPD patients recruited for short-term trials (1 to 3 weeks) in our institute was followed up for 3.8 years on average. Survival was analyzed using a Cox proportional hazards model. The risk factors considered were analyzed, optimally adjusted for age and gender.

RESULTS

At the time of analysis 18 patients (10 male) were deceased. After adjusting for age and gender, P(I(max)), P(E(max)), and HCVR were not correlated with survival within this hypercapnic group. Current smoking (hazard ratio [HR], 7.0; 95% confidence interval [CI], 1.4 to 35.3) and the presence of comorbidity (HR, 5.5; 95% CI, 1.7 to 18.7) were associated with increased mortality. A higher Pa(O2) affected survival positively (HR, 0.6 per 5 mm Hg; 95% CI, 0.4 to 1.0). Pa(CO2) tended to be lower in survivors, but this did not reach statistical significance (HR, 2.0 per 5 mm Hg; 95% CI, 0.9 to 4.3). FEV1 and BMI were not significantly related with survival in hypercapnic COPD patients.

CONCLUSION

In patients with chronic hypercapnia, only smoking status, the presence of comorbidity, and Pa(O2) level are significantly associated with survival. Airway obstruction, age, and BMI are known to be predictors of survival in COPD patients in general. However, these parameters do not seem to significantly affect survival once chronic hypercapnia has developed.

Adult domiciliary oxygen therapy. Position statement of the Thoracic Society of Australia and New Zealand

Patients with chronic obstructive pulmonary disease and a stable daytime PaO2 of < or = 55 mmHg (7.3 kPa) live longer and have a better quality of life if provided with long-term continuous oxygen therapy. It is reasonable to offer continuous oxygen therapy also to patients with other lung diseases that cause chronic hypoxaemia. Indications for supplemental oxygen therapy during exercise (ambulatory oxygen therapy) and sleep (nocturnal oxygen therapy) are less clear.

Continuous Oxygen Therapy for Hypoxic Pulmonary Disease

Continuous oxygen therapy (COT) has become widely accepted in the last 20 years in patients with continuous hypoxemia. This review focuses on guidelines for COT, adherence to these guidelines, and the effect of COT on survival, hospitalization, and quality of life. Guidelines for COT are mainly based on three randomized studies where documentation of hypoxemia (P(a)O2 <60mm Hg) and administration of oxygen at least 15 hours/day, are essential. There is less certainty concerning the required correction for hypoxemia, the attitude against current smokers with hypoxemia, the frequency and methods of follow up, and the effect of prescribing domiciliary oxygen to patients with temporary hypoxemia due to a clinically unstable condition (i.e. short-term oxygen therapy [STOT]). The administration of COT to patients with hypoxemic conditions other than COPD rests on extrapolation of data from COPD patients in the NOTT (Nocturnal Oxygen Therapy Trial) and MRC (British Medical Research Council) studies. Adherence to these guidelines is low in general, and very low in some cases. In some countries, STOT accounts for the majority of all prescriptions of domiciliary oxygen, and because nearly half of these patients do not meet the hypoxemia criteria at 3-month follow-up, re-evaluation is mandatory. Only 35%, approximately, of the patients are followed up, and this is one of the main reasons for poor adherence to the hypoxemia criteria. In order to improve the quality of surveillance of COT, more effort has to be put into education of the patients and staff responsible for COT, centralization of the domiciliary organizations, better equipment for ambulation and traveling, and regular follow-up preferably with home visits. The role of an oxygen register on the quality of surveillance of COT has to be determined. The beneficial effect of COT on survival is well established, and some evidence suggests that COT reduces hospitalization. It appears that ambulatory oxygen from liquid source or lightweight cylinders improves disease-specific quality of life modestly in selected patients who partake in regular outdoor activity. Whether COT from oxygen concentrators improves quality of life significantly is, at present, less clear.

Respiratory Stimulant Use in Chronic Obstructive Pulmonary Disease

OBJECTIVE

To evaluate the use of respiratory stimulants in chronic obstructive pulmonary disease (COPD).

DATA SOURCES

MEDLINE (1966–July 2003) and EMBASE (1980–3rd quarter 2003) were searched using the search terms medroxyprogesterone acetate, acetazolamide, chronic obstructive pulmonary disease, and chronic obstructive lung disease.

DATA SYNTHESIS

Trials are reviewed evaluating ventilatory parameters with acetazolamide and/or medroxyprogesterone in patients with COPD. All studies found improvements in ventilatory parameters, but failed to demonstrate improvements in survival or quality of life.

CONCLUSIONS

Significant improvement in arterial blood gas and ventilatory parameters was reported in COPD patients after acetazolamide and medroxyprogesterone treatment; however, with no improvement in survival or quality of life, the place of these drugs in therapy remains unknown.

Chronic obstructive pulmonary disease * 9: management of ventilatory failure in COPD

The management of respiratory failure during acute exacerbations of COPD and during chronic stable COPD is reviewed and the role of non-invasive and invasive mechanical ventilation is discussed.

Comparison of acetazolamide and medroxyprogesterone as respiratory stimulants in hypercapnic patients with COPD

BACKGROUND

Acetazolamide and medroxyprogesterone acetate (MPA) are two respiratory stimulants that can be used in patients with stable hypercapnic COPD.

DESIGN AND METHODS

The effects of acetazolamide, 250 mg bid, and MPA, 30 mg bid, on daytime and nighttime blood gas values and the influences on the hypercapnic and hypoxic ventilatory and mouth occlusion pressure (P(0.1)) at 100 ms response were studied in a crossover design in 12 hypercapnic patients with stable COPD (FEV(1), 33 +/- 4% predicted [mean +/- SEM]).

RESULTS

Daytime PaCO(2) decreased from 47.3 +/- 0.8 mm Hg (placebo) to 42.0 +/- 1.5 mm Hg during acetazolamide treatment (p < 0.05) and to 42.8 +/- 1.5 mm Hg during MPA treatment (p < 0.05). Daytime PaO(2) improved with acetazolamide from 65.2 +/- 2.3 to 75.0 +/- 3.0 mm Hg (p < 0.05), whereas no significant changes were seen with MPA. Mean nocturnal end-tidal carbon dioxide tension decreased with both treatments, from 42.0 +/- 2.3 to 35.3 +/- 2.3 mm Hg with acetazolamide (p < 0.05) and to 34.5 +/- 0.8 mm Hg with MPA (p < 0.05). The percentage of time that the nocturnal arterial oxygen saturation was < 90% was reduced significantly with acetazolamide, from 34.9 +/- 10.7% to 16.3 +/- 7.5% (p < 0.05). Mean nocturnal saturation did not change with MPA. Resting minute ventilation increased significantly only with MPA from 9.6 +/- 0.7 to 10.8 +/- 0.8 L/min (p < 0.05). The slope of the hypercapnic ventilatory response did not change during acetazolamide and MPA therapy. The hypoxic ventilatory response increased from - 0.2 +/- 0.05 to - 0.4 +/- 0.1 L/min/% during acetazolamide (p < 0.05) and to - 0.3 +/- 0.1 L/min/% during MPA (p < 0.05). The hypoxic P(0.1) response improved with acetazolamide treatment from - 0.05 +/- 0.008 to - 0.15 +/- 0.02 mm Hg/% (p < 0.05).

CONCLUSIONS

This study shows that acetazolamide and MPA both have favorable effects on daytime and nighttime blood gas parameters in ventilatory-limited patients with stable COPD. However, the use of acetazolamide is preferred because of its extra effect on nocturnal saturation.

Mortality after hospitalization for COPD

OBJECTIVES

To identify variables associated with mortality in patients admitted to the hospital for acute exacerbation of COPD.

DESIGN

Prospective cohort study.

SETTING

Acute-care hospital in Barcelona (Spain).

PATIENTS

One hundred thirty-five consecutive patients hospitalized for acute exacerbation of COPD, between October 1996 and May 1997.

MEASUREMENTS AND RESULTS

Clinical, spirometric, and gasometric variables were evaluated at the time of inclusion in the study. Socioeconomic characteristics, comorbidity, dyspnea, functional status, depression, and quality of life were analyzed. Mortality at 180 days, 1 year, and 2 years was 13.4%, 22%, and 35.6%, respectively. Sixty-four patients (47.4%) were dead at the end of the study (median follow-up duration, 838 days). Greater mortality was observed in the bivariate analysis among the oldest patients (p < 0.0001), women (p < 0.01), and unmarried patients (p < 0.002). Hospital admission during the previous year (p < 0.001), functional dependence (Katz index) [p < 0.0004], greater comorbidity (Charlson index) [p < 0.0006], depression (Yesavage Scale) [p < 0.00001]), quality of life (St. George's Respiratory Questionnaire [SGRQ]) [p < 0.01], and PCO(2) at discharge (p < 0.03) were also among the significant predictors of mortality. In the multivariate analysis, the activity SGRQ subscale (p < 0.001; odds ratio [OR], 2.62; confidence interval [CI], 1.43 to 4.78), comorbidity (p < 0.005; OR, 2.2; CI, 1.26 to 3.84), depression (p < 0.004; OR, 3.6; CI, 1.5 to 8.65), hospital readmission (p < 0.03; OR, 1.85; CI, 1.26 to 3.84), and marital status (p < 0.0002; OR, 3.12; CI, 1.73 to 5.63) were independent predictors of mortality.

CONCLUSIONS

Quality of life, marital status, depressive symptoms, comorbidity, and prior hospital admission provide relevant information of prognosis in this group of COPD patients.

Long term effects of non-invasive mechanical ventilation on pulmonary haemodynamics in patients with chronic respiratory failure

BACKGROUND

It is not known whether long term nocturnal mechanical ventilation (NMV) reduces pulmonary hypertension in patients with chronic respiratory failure (CRF).

METHODS

Pulmonary haemodynamics, spirometric values, and gas exchange were studied in 33 patients requiring NMV due to CRF (20 with thoracic restriction, 13 with chronic obstructive pulmonary disease (COPD)) at baseline and after 1 year of NMV given in the volume cycled mode. Patients with COPD also received supplemental oxygen.

RESULTS

Long term NMV improved gas exchange while lung function remained unchanged. Mean pulmonary artery pressure at rest before NMV was higher in patients with thoracic restriction than in those with COPD (33 (10) mm Hgv 25 (6) mm Hg). After 1 year of NMV mean pulmonary artery pressure decreased in patients with thoracic restriction to 25 (6) mm Hg (mean change –8.5 mm Hg (95% CI –12.6 to –4.3), p<0.01) but did not change significantly in patients with COPD (mean change 2.2 mm Hg (95% CI –0.3 to 4.8)).

CONCLUSIONS

Long term NMV in CRF improves pulmonary haemodynamics in patients with thoracic restriction but not in patients with COPD.

Exercise in chronic pulmonary disease: limitations and rehabilitation

Chronic pulmonary disease is common in the community and increasing in prevalence. Although numerous etiologies exist, chronic obstructive pulmonary disease secondary to tobacco smoking, and asthma constitute the majority of cases. The important impact of these diseases on patients is disabling breathlessness and impairment of functional exercise capacity. The symptoms set up a vicious cycle leading to physical deconditioning and worsening exercise performance. The discipline of pulmonary rehabilitation has been conclusively shown to reverse this process, resulting in improved functional capacity and reduced breathlessness. Pulmonary rehabilitation, therefore, should be viewed as essential secondary preventative care for the majority of patients with chronic pulmonary disease. As such, early disease recognition and implementation of exercise reconditioning is important. In order to be maximally effective, pulmonary rehabilitation must recognize the complex underlying pathophysiology in chronic pulmonary disease and be customized to the individual patient. The chosen mode of exercise training should recognize that in order to be truly beneficial, any physiological responses need to translate readily into improvements in activities of daily living. Therefore, sessions in pulmonary rehabilitation should concentrate on exercises that have proven useful in this regard. Aerobic and resistance exercise prescriptions should be rigorous, scientifically based, and derived from an understanding of the basic principles of the human response to exercise prescription. Each of these exercise prescriptions should encompass the basic principles of intensity, frequency, duration, and progression suitably modified for the individual patient with chronic pulmonary disease.

Long term effects of non-invasive mechanical ventilation on pulmonary haemodynamics in patients with chronic respiratory failure

BACKGROUND

It is not known whether long term nocturnal mechanical ventilation (NMV) reduces pulmonary hypertension in patients with chronic respiratory failure (CRF).

METHODS

Pulmonary haemodynamics, spirometric values, and gas exchange were studied in 33 patients requiring NMV due to CRF (20 with thoracic restriction, 13 with chronic obstructive pulmonary disease (COPD)) at baseline and after 1 year of NMV given in the volume cycled mode. Patients with COPD also received supplemental oxygen.

RESULTS

Long term NMV improved gas exchange while lung function remained unchanged. Mean pulmonary artery pressure at rest before NMV was higher in patients with thoracic restriction than in those with COPD (33 (10) mm Hg v 25 (6) mm Hg). After 1 year of NMV mean pulmonary artery pressure decreased in patients with thoracic restriction to 25 (6) mm Hg (mean change -8.5 mm Hg (95% CI -12.6 to -4.3), p<0.01) but did not change significantly in patients with COPD (mean change 2.2 mm Hg (95% CI -0.3 to 4.8)).

CONCLUSIONS

Long term NMV in CRF improves pulmonary haemodynamics in patients with thoracic restriction but not in patients with COPD.

Ambulatory oximetry monitoring in patients with severe COPD: a preliminary study

BACKGROUND

The benefits of long-term oxygen supplementation in COPD patients with hypoxemia are well established. The standard approach to prescribing oxygen uses a static assessment of oxygen requirements in a hospital or clinic setting. The assumption behind this approach is that patients will maintain a "therapeutic" hemoglobin oxygen saturation (SpO2) in the outpatient setting. We questioned the validity of this assumption, and hypothesized that many patients may demonstrate significant oxygen desaturation during normal activities of daily living. STUDY DESIGN, METHODS, AND MEASUREMENTS: We determined if oxygen supplementation maintained a therapeutic SpO2 level in patients with COPD (n = 27), using the technique of ambulatory oximetry monitoring (AOM). AOM consisted of using a portable oximeter to monitor SpO2, pulse rate, and patient activity while patients were engaged in normal activities of daily living over an extended time period (approximately 18 h). The portable oximeter collected and stored these data every 15 s over the monitored time period. Each AOM recording was manually scored for desaturation events and other key variables, including average SpO2 over the monitoring period, the average number of desaturation events per hour, and the percentage of monitored time deleted secondary to artifacts.

SETTING

University-affiliated Veterans Affairs Medical Center.

PATIENTS

All subjects were patients with stable COPD with no recent history of hospitalization or exacerbation of their lung disease.

RESULTS

This cohort of patients demonstrated a surprising frequency of desaturation below the recommended target SpO2 value (90%), which averaged approximately 25% of AOM recording time. There was wide variability among patients in the percentage of time SpO2 was below the target value (range, 3 to 67% of AOM recording time). Motion artifact on the AOM recordings was not a major problem; an average of 8% of the recording time was deleted secondary to artifacts in this patient cohort.

CONCLUSIONS

The results demonstrate that AOM is feasible and accurate with an acceptable level of motion artifact. These results also suggest that the standard approach for prescribing oxygen may lead to subtherapeutic SpO2 values in the outpatient setting. AOM holds promise as a tool to monitor the adequacy of oxygen prescriptions in the outpatient setting in patients with lung disease.

Effects of long-term oxygen therapy in patients with chronic obstructive pulmonary disease

Long-term oxygen therapy is largely used in the management of severe hypoxemia in patients with chronic obstructive pulmonary disease. It was demonstrated that long-term oxygen therapy prolongs life, prevents progression of hypoxic pulmonary hypertension, and controls polycythemia. Recent data suggest that in patients with moderate hypoxemia (Pao2 > 55 mm Hg), long-term oxygen therapy does not prolong life. Life expectancy in those patients seems to depend on the severity of airway obstruction. Long-term oxygen therapy improves cognitive functions and emotional status. There is some evidence suggesting that it also improves quality of life, but more data are needed. There are conflicting data concerning the rationale for nocturnal oxygen supplementation in patients with arterial blood desaturation during sleep.

[The results of the operation of a monitoring unit for home oxygen therapy]

OBJECTIVE

This study aims to a) analyze the prevalence of domiciliary oxygen therapy (DOT) in Mallorca, b) evaluate the cost effectiveness of the DOT monitoring unit, and c) determine the survival of patients with chronic obstructive pulmonary disease who are presently receiving DOT.

METHOD

When the DOT unit was created in April 1994, the situation of all patients receiving DOT in Mallorca was assessed in a transversal study. Over the next three years, these patients were reassessed regularly and all new prescriptions were evaluated (longitudinal study).

RESULTS

Before the unit began work, DOT was prescribed for 71 out of 100,000 inhabitants. DOT was withdrawn from 31% of patients assessed in the transversal study. By the end of the longitudinal study, DOT was being prescribed at a rate of 56 times per 10,000 inhabitants. The activities of the DOT unit brought about annual savings of approximately 38 million pesetas. The number of patients with liquid oxygen and concentrators increased such that the latter has become the main delivery system. The survival of COPD patients with DOT in this study seems to be longer than report.

CONCLUSIONS

a) The prevalence of DOT use in Mallorca before the DOT unit began operating was too high. b) The cost effectiveness of DOT monitoring is positive because DOT use has been optimized and significant savings have ensued (= 38 millions pesetas/year). c) The survival of COPD patients receiving DOT at present appears better than that reported in the literature, possibly related to the greater efficacy of modern treatment.

Domiciliary oxygen and smoking: an explosive combination

Home oxygen therapy has been used to provide symptomatic relief of breathlessness for more than 20 yr. Continuous low-flow oxygen can improve exercise tolerance and decrease pulmonary hypertension in patients suffering from chronic obstructive airway disease. The majority of these patients have been long-time smokers. Despite routine warnings about potential dangers, a considerable number of patients will continue to smoke whilst on oxygen. The incidence of burn injuries related to this practice is not known. Reports of such incidents are, however, very rare. Twenty-one patients who sustained head and neck burn injuries secondary to cigarette related ignition of their oxygen delivery system were admitted to our burn unit over a 7-yr period (1990-1997). All patients (mean age 60.4 yr) had been informed about the associated risks but did not shut off their supplemental oxygen system during smoking. The mean size of their burn injuries was 2% of the total body surface, mainly affecting the face, ears, and neck. The average duration of the hospital stay was 3.6 days. Two patients required split-thickness skin grafting. Whether chronically ill patients on domiciliary oxygen who continue to smoke covertly are amenable to medical advice to abandon this habit is questionable. A more aggressive education about the explosive nature of their activity should help to prevent them from using tobacco and oxygen at the same time.

Prognostic value of hypercapnia in patients with chronic respiratory failure during long-term oxygen therapy

Hypercapnia observed in patients with chronic respiratory failure may not be an ominous sign for prognosis when they are receiving long-term oxygen therapy (LTOT). In this study, we selected 4,552 patients with chronic obstructive pulmonary disease (COPD) and 3,028 with sequelae of pulmonary tuberculosis (TBsq) receiving LTOT from 1985 to 1993 throughout Japan and prospectively analyzed their prognoses. The hypercapnic patients (PaCO2 >= 45 mm Hg) had a better prognosis than the normocapnic patients (35 <= PaCO2 < 45 mm Hg) for TBsq, but no difference was found between the two groups with COPD. Furthermore, Cox's proportional hazards model revealed that in TBsq hypercapnia was an independent factor for favorable prognosis, and that the relative risk for mortality was 0.76 in patients with 45 <= PaCO2 < 55 mm Hg, 0.64 for those with 55 <= PaCO2 < 65 mm Hg, and 0. 49 for patients with PaCO2 >= 65 mm Hg against normocapnic patients. This favorable effect of hypercapnia in TBsq was particularly apparent in the patients without severe airway obstruction. Even a rise of 5 mm Hg or more in PaCO2 over the initial 6- to 18-mo follow-up period was not associated with poor prognosis in TBsq, although it was in COPD. From these findings, we conclude that hypercapnia should not be generally considered an ominous sign for prognosis in those patients who receive LTOT.