The value of forced expiratory volume in 1 s in screening subjects with stable COPD for PaO2 < 7.3 kPa qualifying for long-term oxygen therapy

Burden and Characteristics of Severe Chronic Hypoxemia in a Real-World Cohort of Subjects with COPD

Background

Chronic respiratory failure may occur as a consequence of chronic obstructive pulmonary disease (COPD) and is associated with significant morbidity and mortality. Hypoxemia is determined by underlying disease characteristics and comorbidities. Severe hypoxemia is typically only found in subjects with severe airflow obstruction (FEV₁<50% predicted). However, how hypoxemia relates to disease characteristics is not fully understood.

Methods

In the French Initiatives BPCO real-life cohort, arterial blood gases were routinely collected in most patients. Relationships between severe hypoxemia, defined by a Pa0₂<60 mmHg (8 kPa) and clinical/lung function features, comorbidities and mortality were assessed. In subjects with severe hypoxemia, clinical characteristics and comorbidities were compared between those with non-severe versus severe airflow limitation. Classification and regression trees (CART) were used to define clinically relevant subgroups (phenotypes).

Results

Arterial blood gases were available from 887 subjects, of which 146 (16%) exhibited severe hypoxemia. Compared to subjects with a PaO2≥60 mmHg, the severe hypoxemia group exhibited higher mMRC dyspnea score, lower FEV₁, higher RV and RV/TLC, more impaired quality of life, lower 6-minute walking distance, less frequent history of asthma, more frequent diabetes and higher 3-year mortality rate (14% versus 8%, p=0.026). Compared to subjects with Pa0₂<60 mmHg and FEV₁<50% (n=115, 13%), those with severe hypoxemia but FEV1≥50% predicted (n=31) were older, had higher BMI, less hyperinflation, better quality of life and a higher rate of diabetes (29% versus 13%, p=0.02). Severe hypoxemia was better related to CART-defined phenotypes than to GOLD ABCD classification.

Conclusion

In this cohort of stable COPD subjects, severe hypoxemia was associated with worse prognosis and more severe symptoms, airflow limitation and hyperinflation. Compared to subjects with severe hypoxemia and severe airflow limitation, subjects with severe hypoxemia despite non-severe airflow limitation were older, had higher BMI and more diagnosed diabetes.

Trial Registration

04–479.

NHANES III equations enhance early detection and mortality prediction of bronchiolitis obliterans syndrome after hematopoietic SCT

Bronchiolitis obliterans syndrome (BOS) is a serious complication of chronic GVHD (cGVHD) following HSCT (hematopoietic SCT). The clinical diagnosis of BOS is based on pulmonary function test (PFT) abnormalities including: FEV1<75% predicted and obstructive FEV1/VC ratio, calculated using reference equations. We sought to determine if the frequency of clinical diagnoses and severity of BOS would be altered by using the recommended NHANES III vs older equations (Morris/Goldman/Bates, MGB) in 166 cGVHD patients, median age 48 (range: 12-67). We found that NHANES III equations significantly increased the prevalence of BOS, with an additional 11% (18/166) meeting diagnostic criteria by revealing low FEV1 (<75%) (P<0.0001), and six additional patients by obstructive ratio (vs MBG). Collectively, this led to an increase of BOS incidence from 17 (29/166) to 29% (41/166). For patients with severe BOS, (FEV1<35%), NHANES III equations correctly predicted death 71.4% vs 50% using MGB. In conclusion, the use of NHANES III equations markedly increases the proportion of cases meeting diagnostic criteria for BOS and improves prediction of survival.

Below what FEV1 should arterial blood be routinely taken to detect chronic respiratory failure in COPD?

INTRODUCTION

To diagnose and assess chronic respiratory failure in stable chronic obstructive pulmonary disease (COPD) the measurement of arterial blood gases (ABG) is required. It has been suggested that ABG be determined for this purpose when FEV1 ranges between 50% and 30% predicted, but these thresholds are not evidence-based.

OBJECTIVE

To identify the post-bronchodilator (BD) FEV₁ and arterial oxygen saturation (SaO(2)) values that provide the best sensitivity, specificity, and likelihood ratio (LR) for the diagnosis of hypoxaemic and/or hypercapnic chronic respiratory failure in stable COPD.

METHODS

A total of 150 patients were included (39 with PaO₂ < 60 mmHg [8 kPa], 14 of them with a PaCO₂ ≥ 50 mmHg [6.7 kPa]). The best post-BD FEV(1) and SaO(2) cut-off points to predict chronic respiratory failure were selected using the PC and the Receiver Operating Characteristics (ROC) curves.

RESULTS

A post-BD FEV(1) equal to 36% and an SaO(2) of 90% were the best predictive values for hypoxaemic respiratory failure and a post-BD FEV(1) equal to 33% for the hypercapnic variant. An FEV(1) ≥ 45% ruled out hypoxaemic respiratory failure.

CONCLUSION

A post-BD FEV(1) of 36% is the best cut-off point to adequately predict both hypoxaemic and hypercapnic respiratory failure in the patient with stable COPD. For its part, an SaO(2) of 90% is the best value for isolated hypoxaemic failure. These values could be considered for future clinical recommendations/guidelines for COPD.

Hyperinflation is associated with lower sleep efficiency in COPD with co-existent obstructive sleep apnea

Prior research has shown that individuals with obstructive lung disease are at risk for sleep fragmentation and poor sleep quality. We postulated that patients with chronic obstructive pulmonary disease (COPD) and obstructive sleep apnea (known as overlap syndrome) who have more severe lung disease, as measured by lung hyperinflation (inspiratory capacity/total lung capacity), would have greater sleep disturbances independent of traditional measures of sleep apnea. We performed a retrospective chart review of consecutive patients evaluated and treated in an academic pulmonary clinic for overlap syndrome. Pulmonary function tests and polysomnogram data were collected. Thirty patients with overlap syndrome were included in the analysis. We found significant univariable associations between sleep efficiency and apnea/hypopnea index (beta = -0.285, p = 0.01) and between sleep efficiency and lung hyperinflation (beta = 0.654, p = 0.03). Using multivariable linear regression, the relationship between sleep efficiency and lung hyperinflation remained significant (beta = 1.13, p = 0.02) after adjusting for age, sex, body mass index, apnea/hypopnea index, FEV(1)% predicted, oxygen saturation nadir, medications, and cardiac disease. We conclude that increased severity of hyperinflation is associated with worse sleep efficiency, independent of apnea and nocturnal hypoxemia. The mechanisms underlying this observation are uncertain. We speculate that therapies aimed at reducing lung hyperinflation may improve sleep quality in patients with overlap syndrome.

Cardiopulmonary Rehabilitation and Cancer Rehabilitation. 2. Pulmonary Rehabilitation Review

Pulmonary rehabilitation includes the rehabilitation of not only patients with respiratory failure in need of ventilatory support but also patients with primary pulmonary disease. New advances in medical management now offer treatment to patients with end-stage emphysema, pulmonary hypertension, and interstitial disease, and the principles of rehabilitation can add both function and quality to the lives of these patients. New surgical approaches and better transplantation outcomes that restore pulmonary function have also been introduced. Rehabilitation professionals need to be aware of these advances and be able to incorporate this knowledge into the practice of rehabilitation medicine.

OVERALL ARTICLE OBJECTIVES

(a) To identify major categories of pulmonary disease seen in pulmonary rehabilitation, (b) to know appropriate interventions and support for patients with respiratory failure, (c) to describe the new interventions available for end-stage lung disease, and (d) to describe the appropriate pulmonary rehabilitation for people with pulmonary disease.

Screening patients in general practice with COPD for long-term domiciliary oxygen requirement using pulse oximetry

Epidemiological data suggest long-term oxygen therapy (LTOT) delivered by oxygen concentrators in patients with severe hypoxic chronic obstructive pulmonary disease (COPD) is under-prescribed by General Practitioners (GPs) in England and Wales. One reason for this may be the unavailability to GPs of a measure of arterial oxygenation needed to fulfil the defined prescription criteria. Provision of a non-invasive measure of oxygenation may improve detection of hypoxic subjects and increase appropriate prescribing. This study aimed to evaluate pulse oximetry in a general practice setting and to screen for severe undetected hypoxaemia fulfilling the LTOT prescription criteria in patients with COPD. All COPD patients attending surgery in two practices were screened with oximeters for hypoxaemia. Those with an oxygen saturation of < or = 92% were referred to hospital for formal arterial blood gas analysis and an oxygen concentrator assessment. GPs were asked to evaluate their experience in the ease of use and application of oximetry. The number of patients receiving oxygen by concentrator before the study was compared with the national rate and the number after the study with the estimated need suggested by epidemiological studies. Over a 12-month period a total of 114 patients were screened in the two practices with a combined list size of 15,742. Thirteen patients had saturations of < or = 92%. Two refused and 11 underwent formal arterial gas analysis. Three had PaO2 < 7.3 kPa and new prescriptions for oxygen concentrators were made in these previously unsuspected severely hypoxaemic subjects as a result. One other hypoxaemic subject was referred and found to have another treatable medical condition. The initial prevalence of concentrator prescription (0.013% CI 0.003, 0.047) was similar to the national rate (0.024%) and the prevalence observed after screening (0.031%, CI 0.013, 0.073) fell within the lower suggested prescription need of previous epidemiological data (0.02-0.10%). All practitioners found the oximeters simple to use and helpful in assisting with assessment of the severity of their patient's condition. Oximetry provides a readily usable non-invasive method of screening and when applied to all COPD patients seen in general practice can reveal those fulfilling the criteria for long term oxygen who would otherwise not be identified as needing this treatment.