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

Thoracic Society of Australia and New Zealand clinical practice guideline on adult home oxygen therapy

This Thoracic Society of Australia and New Zealand Guideline on the provision of home oxygen therapy in adults updates a previous Guideline from 2015. The Guideline is based upon a systematic review and meta-analysis of literature to September 2022 and the strength of recommendations is based on GRADE methodology. Long-term oxygen therapy (LTOT) is recommended for its mortality benefit for patients with COPD and other chronic respiratory diseases who have consistent evidence of significant hypoxaemia at rest (PaO2 ≤ 55 mm Hg or PaO2 ≤59 mm Hg in the presence of hypoxaemic sequalae) while in a stable state. Evidence does not support the use of LTOT for patients with COPD who have moderate hypoxaemia or isolated nocturnal hypoxaemia. In the absence of hypoxaemia, there is no evidence that oxygen provides greater palliation of breathlessness than air. Evidence does not support the use of supplemental oxygen therapy during pulmonary rehabilitation in those with COPD and exertional desaturation but normal resting arterial blood gases. Both positive and negative effects of LTOT have been described, including on quality of life. Education about how and when to use oxygen therapy in order to maximize its benefits, including the use of different delivery devices, expectations and limitations of therapy and information about hazards and risks associated with its use are key when embarking upon this treatment.

Improving the management of patients with chronic cardiac and respiratory diseases by extending pulse-oximeter uses: the dynamic pulse-oximetry

Respiratory and cardio-vascular chronic diseases are among the most common noncommunicable diseases (NCDs) worldwide, accounting for a large portion of health-care costs in terms of mortality and disability. Their prevalence is expected to rise further in the coming years as the population ages. The current model of care for diagnosing and monitoring NCDs is out of date because it results in late medical interventions and/or an unfavourable cost-effectiveness balance based on reported symptoms and subsequent inpatient tests and treatments. Health projects and programs are being implemented in an attempt to move the time of an NCD's diagnosis, as well as its monitoring and follow up, out of hospital settings and as close to real life as possible, with the goal of benefiting both patients' quality of life and health system budgets. Following the SARS-CoV-2 pandemic, this implementation received additional impetus. Pulseoximeters (POs) are currently used in a variety of clinical settings, but they can also aid in the telemonitoring of certain patients. POs that can measure activities as well as pulse rate and oxygen saturation as proxies of cardio-vascular and respiratory function are now being introduced to the market. To obtain these data, the devices must be absolutely reliable, that is, accurate and precise, and capable of recording for a long enough period of time to allow for diagnosis. This paper is a review of current pulse-oximetry (POy) use, with the goal of investigating how its current use can be expanded to manage not only cardio-respiratory NCDs, but also acute emergencies with telemonitoring when hospitalization is not required but the patients' situation is debatable. Newly designed devices, both "consumer" and "professional," will be scrutinized, particularly those capable of continuously recording vital parameters on a 24-hour basis and coupling them with daily activities, a practice known as dynamic pulse-oximetry.

Comparison of SpO2 and heart rate values on Apple Watch and conventional commercial oximeters devices in patients with lung disease

Lung diseases have high mortality and morbidity, with an important impact on quality of life. Hypoxemic patients are advised to use oxygen therapy to prolong their survival, but high oxygen saturation (SpO2) levels can also have negative effects. Pulse oximeters are the most common way to assess oxygen levels and guide medical treatment. This study aims to assess whether wearable devices can provide precise SpO2 measurements when compared to commercial pulse oximeters. This is a cross-section study with 100 patients with chronic obstructive pulmonary disease and interstitial lung disease from an outpatient pneumology clinic. SpO2 and heart rate data were collected with an Apple Watch Series 6 (Apple) and compared to two commercial pulse oximeters. The Bland-Altman method and interclass correlation coefficient were used to compare their values. We observed strong positive correlations between the Apple Watch device and commercial oximeters when evaluating heart rate measurements (r = 0.995, p < 0.001) and oximetry measurements (r = 0.81, p < 0.001). There was no statistical difference in the evaluation of skin color, wrist circumference, presence of wrist hair, and enamel nail for SpO2 and heart rate measurements in Apple Watch or commercial oximeter devices (p > 0.05). Apple Watch 6 is a reliable way to obtain heart rate and SpO2 in patients with lung diseases in a controlled environment.

Reducing the effects of parallax in camera-based pulse-oximetry

Camera-based pulse-oximetry enables contactless estimation of peripheral oxygen saturation (SpO₂). Because of the lack of readily available and affordable single-optics multi-spectral cameras, custom-made multi-camera setups with different optical filters are currently mostly used. The introduced parallax by these cameras could however jeopardise the SpO₂ algorithm assumptions, especially during subject movement. In this paper we investigate the effect of parallax quantitatively by creating a large dataset consisting of 150 videos with three different parallax settings and with realistic and challenging motion scenarios. We estimate oxygen saturation values with a previously used global frame registration method and with a newly proposed adaptive local registration method to further reduce the parallax-induced image misalignment. We found that the amount of parallax has an important effect on the accuracy of the SpO₂ measurement during movement and that the proposed local image registration reduces the error by more than a factor of 2 for the most common motion scenarios during screening. Extrapolation of the results suggests that the error during the most challenging motion scenario can be reduced to approximately 2 percent when using a parallax-free single-optics camera. This study provides important insights on the possible applications and use cases of remote pulse-oximetry with current affordable and readily available cameras.

Portable Oxygen Therapy: Is the 6-Minute Walking Test Overestimating the Actual Oxygen Needs?

The appropriate titration for the personalized oxygen needs of patients with chronic obstructive pulmonary disease (COPD) and severe hypoxemia is a determining factor in the success of long-term oxygen therapy. There are no standardized procedures to assist in determining the patient’s needs during the physical activities of daily life. Despite that effort tests are a wide broad approach, further research concerning the development of protocols to titrate O₂ therapy is needed. The main objective of this study was to assess whether the level of oxygen titrated through the 6-minute walking test (6MWT) for patients with COPD and exertional hypoxemia is adequate to meet the patients’ demand during their activities of daily living. Physiological and subjective variables were estimated for a study population during two walking tests: a 6MWT and a 20-minute walking circuit (20MWC), designed ad-hoc to reproduce daily physical activities more truthfully. The results indicate that in a significant proportion of patients, the 6MWT might not accurately predict their oxygen needs at a domiciliary environment. Therefore, the titration of the portable O₂ therapy could not be optimal in these cases, with the detrimental impact on the patient’s health (hyperoxia episodes), the autonomy of the oxygen device, and the decrease of time out of the home.

New Perspectives in Oxygen Therapy Titration: Is Automatic Titration the Future?

Oxygen therapy, like all technology-based treatments, is continuously evolving. There are no doubts as to its effectiveness in the treatment of acute and respiratory failure in different clinical scenarios. However, the dosing guidelines for oxygen therapy are not as strict as for other treatments. The use of higher than necessary flows over excessively long periods, derived from the clinician's perception of it as a 'life-saving treatment with few side effects', has led to a rather liberal use of this intervention, despite evidence that overuse and suboptimal adjustment can be harmful. The titration of oxygen therapy, which is traditionally performed manually, has been shown to be beneficial. Recently, new devices have been developed that automatically adjust oxygen flow rates to the needs of each patient, in order to maintain stable oxygen saturation levels. These closed-loop oxygen supply systems can potentially reduce medical error, improve morbidity and mortality, and reduce care costs. Familiarizing the medical community with these technological advances will improve awareness of the risks of the inappropriate use of oxygen therapy. The aim of this paper is to provide an update of recent developments in oxygen therapy titration.

Association between decreased respiratory function and increased blood pressure variability

OBJECTIVE

The respiratory system is an important component in the control of the autonomic nervous system, and is a possible factor of blood pressure variability (BPV). We examined whether decreased respiratory function is associated with exaggerated BPV in hypertensives.

PATIENTS AND METHODS

This is a substudy of the Japan Morning Surge-Home Blood Pressure Study and patients who underwent both spirometry and ambulatory blood pressure monitoring (ABPM) in the Japan Morning Surge-Home Blood Pressure study were analyzed. In 95 hypertensives without known clinical respiratory diseases, we performed ABPM and the respiratory function test.

RESULTS

Percent vital capacity (%VC), but not forced expiratory volume in 1 s as a percentage of forced vital capacity, was associated with the SD (r=-0.23, P<0.05) and coefficient of variation (r=-0.25, P<0.05) of daytime systolic blood pressure (SBP). Lower %VC was associated with higher SD of daytime SBP (P=0.049 for trend). After adjusting for covariates, %VC tended to be associated with SD of daytime SBP (β=-0.22, P=0.08) and was associated with coefficient of variation of daytime SBP (β=-0.26, P=0.04).

CONCLUSION

Decreased respiratory function was associated with exaggerated ambulatory BPV, especially in the daytime in hypertensives without respiratory diseases. This is the first study to show an association between respiratory function and increased BPV as assessed by ABPM. The results of our study indicate that low respiratory function could exaggerate BPV, and thus may be one of the mechanisms underlying the elevated cardiovascular risk in patients with decreased respiratory function.

Oxygen Desaturation in Daily Life and During a Laboratory-Based Protocol of Activities of Daily Living in COPD: Is There Relationship?

PURPOSE

To analyze the relationship between oxygen desaturation episodes during a laboratory-based ADL protocol and in real-life routine in patients with stable chronic obstructive pulmonary disease (COPD).

METHODS

Twenty patients with stable COPD (12 men, 70 ± 7 years, FEV₁% 54 ± 15 predicted) with no indication for long-term oxygen therapy (LTOT) were submitted to assessments including ADL performance by the Londrina ADL Protocol (LAP) and level of physical activity in daily life, both while submitted to simultaneous activity and pulse oximeter monitoring.

RESULTS

Episodes of desaturation ≥ 4% (ED ≥ 4%) during the LAP were correlated both with ED ≥ 4% in daily life (r = 0.45) and number of episodes of SpO₂ under 88% (ED < 88%) in daily life (r = 0.59). ED < 88% during the LAP was also correlated with ED < 88% in daily life (r = 0.51), explaining 43% of its variance.

CONCLUSION

In stable patients with COPD and no indication of LTOT, episodes of desaturation during a lab-based ADL protocol are moderately related to episodes of desaturation in daily (real) life, especially those episodes under 88%.

Exertional hypoxemia in stable COPD is common and predicted by circulating proadrenomedullin

BACKGROUND

The prevalence of exertional hypoxemia in unselected patients with COPD is unknown. Intermittent hypoxia leads to adrenomedullin (ADM) upregulation through the hypoxia-inducible factor-1 pathway. We aimed to assess the prevalence and the annual probability to develop exertional hypoxemia in stable COPD. We also hypothesized that increased ADM might be associated with exertional hypoxemia and envisioned that adding ADM to clinical variables might improve its prediction in COPD.

METHODS

A total of 1,233 6-min walk tests and circulating proadrenomedullin (proADM) levels from 574 patients with clinically stable, moderate to very severe COPD enrolled in a multinational cohort study and followed up for 2 years were concomitantly analyzed.

RESULTS

The prevalence of exertional hypoxemia was 29.1%. In a matrix derived from a fitted-multistate model, the annual probability to develop exertional hypoxemia was 21.6%. Exertional hypoxemia was associated with greater deterioration of specific domains of health-related quality of life, higher severe exacerbation, and death annual rates. In the logistic linear and conditional Cox regression multivariable analyses, both FEV1% predicted and proADM proved independent predictors of exertional hypoxemia (P < .001 for both). Adjustment for comorbidities, including cardiovascular disorders, and exacerbation rate did not influence results. Relative to using FEV1% predicted alone, adding proADM resulted in a significant improvement of the predictive properties (P = .018). Based on the suggested nonlinear nomogram, patients with moderate COPD (FEV1% predicted = 50%) but high proADM levels (> 2 nmol/L) presented increased risk (> 30%) for exertional desaturation.

CONCLUSIONS

Exertional desaturation is common and associated with poorer clinical outcomes in COPD. ADM improves prediction of exertional desaturation as compared with the use of FEV1% predicted alone.

TRIAL REGISTRY

ISRCTN Register; No.: ISRCTN99586989; URL: www.controlled-trials.com.

TELEMOLD project: oximetry and exercise telemonitoring to improve long-term oxygen therapy

BACKGROUND

Standard assessment of long-term oxygen therapy (LTOT) prescription involves hospital-based clinical tests. However, there is some evidence suggesting that oxygen demand during daily activities may not be correctly estimated by such tests, when compared with continuous ambulatory oximetry. The authors describe the results of a study aiming to evaluate the clinical relevance of a home telemonitoring system in LTOT optimization.

SUBJECTS AND METHODS

Thirty-five chronic respiratory failure patients were monitored in real time with an oximeter sensor and an accelerometer. Signals were sent via Bluetooth(®) (Bluetooth SIG, Kirkland, WA) to a mobile phone and then via 3G or general packet radio service to a server. Continuous and secure access to data was established through an Internet site.

RESULTS

Each patient was monitored an average of 7.6 ± 4.5 days (total, 83 ± 67 h). Valid records were on average 65 ± 24%. Records of rest, activity, and sleep time per patient were, on average, 28 ± 21%, 7 ± 6%, and 59 ± 25%, respectively. Significant desaturation during rest, activity, and sleep was found in 2, 26, and 9 patients, respectively. Patients' ratings of the user-friendliness of the equipments, assessed by questionnaire, were fairly good (76% reported it as easy/very easy).

CONCLUSIONS

Our study suggests that a telemonitoring system combining oximetry and physical activity evaluation might contribute to a more adequate oxygen prescription, mainly during daily activities.

The relationship of the BODE index to oxygen saturation during daily activities in patients with chronic obstructive pulmonary disease

BACKGROUND

The frequency of oxygen desaturation during daily activities in chronic obstructive pulmonary disease (COPD) is poorly defined. The BODE index predicts survival in COPD. The purpose of this study was to determine the relationship between BODE scores and oxygen saturation during daily activities.

METHODS

Seventy-eight patients with COPD (FEV(1) = 37%) underwent ambulatory oximetry and activity monitoring. We defined four activity categories: Walking, Slow-Intermittent-Walking (SIW), Active-Not-Walking (ANW), and Rest. We quantified oxygen desaturation during activity using a desaturation index (DSI = % time oxygen saturation <90%). BODE scores were categorized into three groups: group I (0-3), II (4-6), and III (7-10).

RESULTS

The percentage of patients demonstrating oxygen desaturation (DSI ≥ 10%) during each activity was 55% for Walking, 35% for SIW, 15% for ANW, and 28% for Rest. There was a strong association between BODE score and desaturation for Walking and SIW. During Walking, 21, 44, and 86% of patients in BODE groups I, II, and III, respectively, demonstrated desaturation. The DSI for Walking and SIW was increased in patients in BODE groups II and III compared to group I (P < 0.006, P < 0.007, respectively). BODE score was also linked to long-term oxygen therapy (LTOT) usage; the majority of patients not on LTOT (89%) had a BODE score <7. The majority of patients on LTOT (84%) demonstrated desaturation during Walking, but 42% of patients not on LTOT also demonstrated desaturation. In this subgroup of patients not on LTOT, all patients with a BODE score ≥ 7 demonstrated desaturation during Walking.

CONCLUSIONS

The link between the BODE index and oxygen desaturation during daily activities suggests that desaturation is linked to disease severity. Our data suggest that patients with a BODE score ≥ 7 should be evaluated for desaturation during daily activities. Use of the BODE index to screen for exertional desaturation may have value as a tool that can lead to the earlier identification of patients who may be candidates for LTOT.

Serial pulse oximetry in hepatopulmonary syndrome

BACKGROUND/AIM

The natural history of hepatopulmonary syndrome (HPS) is poorly characterized and how hypoxemia develops and progresses over time is unclear. We evaluated oxygenation over time in advanced liver disease patients with and without HPS using serial pulse oximetry.

METHODS

Data from a prospective cohort of patients evaluated for liver transplantation were analyzed. All patients with significant cardiopulmonary disease were excluded and patients with and without HPS were compared. Arterial oxygen saturation measurements with pulse oximetry (SpO(2)) were recorded serially from initial evaluation until transplantation or last clinic visit on record. Patients with SpO(2) measurements at ≥ 2 visits were included.

RESULTS

A total of 22 HPS patients were compared to 32 non-HPS patients (18 with intrapulmonary vasodilation on contrast echocardiography, CE) over a mean duration of 20 months and 4 SpO(2) measurements. HPS patients had lower SpO(2) at baseline (96.8 vs. 98.4%, P = 0.02) and at end of follow-up (95.8 vs. 98.2%, P = 0.02), and were more likely to have a ≥ 2% reduction (P = 0.04) and faster decline in SpO(2) as compared to non-HPS patients (F = 2.2, P = 0.04). HPS patients with lower SpO(2) and/or PO(2) at baseline appeared more likely to worsen over time. There was no difference in SpO(2) over time between the 2 non-HPS subgroups (- or +CE).

CONCLUSIONS

HPS patients have a significant decline in SpO(2) over time compared to non-HPS patients, and therefore, pulse oximetry may be useful for monitoring cirrhotics for development or worsening of HPS. Presence of intrapulmonary vasodilation in the absence of hypoxemia does not appear to affect SpO(2) over time.

Hypoxemia and arrhythmia during daily activities and six-minute walk test in fibrotic interstitial lung diseases

We performed 24-hr monitoring of pulse oximetric saturation (SpO(2)) with ECG and six-minute walk test (6MWT) in 19 patients with fibrotic interstitial lung diseases (ILD) to investigate; 1) The frequency and severity of hypoxemia and dysrhythmia during daily activities and 6MWT, 2) safety of 6MWT, and 3) the parameters of 6MWT which can replace 24-hr continuous monitoring of SpO(2) to predict hypoxemia during daily activities. All patients experienced waking hour hypoxemia, and eight of nineteen patients spent > 10% of waking hours in hypoxemic state. Most patients experienced frequent arrhythmia, mostly atrial premature contractions (APCs) and ventricular premature contractions (VPCs). There were significant correlation between the variables of 6MWT and hypoxemia during daily activities. All of the patients who desaturated below 80% before 300 meters spent more than 10% of waking hour in hypoxemia (P = 0.018). In contrast to waking hour hypoxemia, SpO(2) did not drop significantly during sleep except in the patients whose daytime resting SpO(2) was already low. In conclusion, patients with fibrotic ILD showed significant period of hypoxemia during daily activities and frequent VPCs and APCs. Six-minute walk test is a useful surrogate marker of waking hour hypoxemia and seems to be safe without continuous monitoring of SpO(2).

Exertional desaturation in patients with chronic obstructive pulmonary disease

Although the Centers for Medicare and Medicaid Services oxygen prescription guidelines utilize a threshold arterial oxygen tension <or=55 mmHg or an oxygen saturation <or=88%, a range of oxygen levels and relative declines have been used in investigations of exertional desaturation in patients with chronic obstructive pulmonary disease (COPD). There is no uniform definition of exertional hypoxemia or standardized exercise protocol to elicit decreases in oxygen levels in individuals with COPD. The causes for exertional desaturation in patients with COPD are multifactorial with ventilation-perfusion mismatching, diffusion-type limitation, shunting and reduced oxygen content of mixed venous blood all contributing to some degree. Neither resting oxygen saturation nor pulmonary function studies can reliably predict which patients with COPD will develop exertional desaturation. However, preserved pulmonary function, especially diffusing capacity, reliably predicts which patients with COPD will sustain oxygenation during exercise. Although exertional desaturation in patients with COPD appears to portend a poor prognosis, there is no evidence that maintenance of normoxemia during exercise improves the survival of these patients. Studies of the effect of supplemental oxygen on exercise performance in individuals with COPD who desaturate with exertion have yielded conflicting results. The use of short-term or "burst" oxygen either prior to or after exertion may not have significant clinical benefit. Differences in the definition of desaturation, mode of exercise, and characteristics of the patient population make it difficult to compare studies of exertional desaturation and its treatment and to determine their applicability to clinical practice.

Relation between Nocturnal Arterial Oxygen Desaturation and Morning Blood Pressure

OBJECTIVE

Arterial oxygen saturation (SpO2) in volunteers had been previously investigated, and the possibility that a decrease in SpO2 leads to an increase in blood pressure (BP) in airline passengers experiencing oxygen desaturation at high altitudes was reported. It was also shown that mean nocturnal SpO2 was lower in subjects with high-normal BP or mild hypertension than in those with normal BP. The present study investigated nocturnal SpO2, evening BP, and morning BP of volunteers during daily life and examined the relation between nocturnal SpO2 and change in BP (morning BP minus evening BP) to determine the influence of SpO2 on BP.

METHODS

Sixty-two volunteers (31 men and 31 women) aged 40-87 years (mean: 55.9 +/- 12 [SD] years) underwent measurement of SpO2 and heart rate with a ring-shaped pulse oximeter during sleep at home. Evening BP and morning BP were measured by automatic BP recorder. Subjects that were classified as having high SpO2 (mean nocturnal SpO2 >or= 95%; n = 23, 10 men and 13 women; mean age: 53.2 +/- 12 years) or low SpO2 (mean nocturnal SpO2 < 94%; n = 21, 12 men and 9 women; mean age: 58.7 +/- 13 years) were compared. The relation between mean nocturnal SpO2 and morning BP and the relation between mean nocturnal SpO2 and change in BP were investigated.

RESULTS

There was a significant negative correlation between mean nocturnal SpO2 and morning systolic BP (SBP; r = -0.50, p < 0.01) and between mean nocturnal SpO2 and morning diastolic BP (DBP; r = -0.37, p < 0.01). A significant negative correlation between mean nocturnal SpO2 and change in SBP was observed (r = -0.57, p < 0.01). Morning BP was significantly higher in the low nocturnal SpO2 group than in the high nocturnal SpO2 group (p < 0.001).

CONCLUSION

The increase in morning BP from evening BP was significantly greater in subjects with a low nocturnal SpO2. The decrease in SpO2 during sleep may affect morning BP rise.

Respiratory disorders during sleep in chronic obstructive pulmonary disease

Patients with COPD may show slow, progressive deteriorations in arterial blood gases during the night, particularly during rapid eye movement (REM) sleep. This is mainly due to hypoventilation, while a deterioration of ventilation/perfusion mismatch plays a minor role. The severity of gas exchanges alterations is proportional to the degree of impairment of diurnal pulmonary function tests, particularly of partial pressure of oxygen (PaO₂) and of carbon dioxide (PaCO₂) in arterial blood, but correlations between diurnal and nocturnal blood gas levels are rather loose. Subjects with diurnal PaO₂ of 60–70 mmHg are distinguished in “desaturators” and “nondesaturators” according to nocturnal oxyhemoglobin saturation behavior. The role of nocturnal hypoxemia as a determinant of alterations in sleep structure observed in COPD is dubious. Effects of the “desaturator” condition on pulmonary hemodynamics, evolution of diurnal blood gases, and life expectancy are also controversial. Conversely, it is generally accepted that occurrence of sleep apneas in COPD is associated with a worse evolution of the disease. Nocturnal polysomnographic monitoring in COPD is usually performed when coexistence of sleep apnea (“overlap syndrome”) is suspected, while in most other cases nocturnal oximetry may be enough. Nocturnal oxygen attenuates sleep desaturations among stable patients, without increases in PaCO₂ of clinical concern. Nocturnal treatment with positive pressure ventilators may give benefit to some stable hypercapnic subjects and patients with the overlap syndrome.

Effect of Oxygen on Health Quality of Life in Patients with Chronic Obstructive Pulmonary Disease with Transient Exertional Hypoxemia

RATIONALE

Ambulatory oxygen improves acute exercise performance in people with chronic obstructive pulmonary disease (COPD). This improvement may not translate into symptomatic benefit for patients during activities of daily living.

OBJECTIVES

We undertook a series of individual randomized controlled trials (N-of-1 RCTs) to measure the effect of oxygen in patients with COPD who do not meet criteria for mortality reduction with long-term oxygen therapy.

METHODS

Twenty-seven patients completed blinded N-of-1 RCTs, each comprising three pairs of 2-week home treatment periods, with oxygen provided during one period of each pair and a placebo mixture during the other.

MEASUREMENTS AND MAIN RESULTS

Patients completed the Chronic Respiratory Questionnaire (CRQ), the St. George's Respiratory Questionnaire, and a home five-minute-walk test at the end of each period. We defined a positive response as a CRQ dyspnea score greater (less dyspnea) on oxygen than placebo during all three pairs of treatment periods, with a difference >or= 0.5 inches for at least two treatment pairs. Oxygen significantly increased the five-minute-walk test (427 vs. 412 steps, p = 0.04). Two of 27 patients met the responder criteria. Among the whole group, neither the CRQ nor the St. George's Respiratory Questionnaire showed any statistical or clinical differences between oxygen and placebo.

CONCLUSIONS

This study does not support the general application of long-term ambulatory oxygen therapy for patients with COPD who do not meet criteria for mortality reduction with long-term oxygen therapy. N-of-1 RCTs can identify patients who may benefit.

Oximetry feedback flow control simulation for oxygen therapy

OBJECTIVES

For many with Chronic Obstructive Pulmonary Disease (COPD), arterial oxygen saturation while receiving Long-Term Oxygen Therapy (LTOT) falls below an acceptable threshold (SpO(2) < 90%) for extended periods during routine daily activities. Using a closed-loop controller, we have evaluated a simulated method to automatically regulate the oxygen flow-rate in response to the measured oxygen demand.

METHODS

The closed-loop control scheme was implemented in a computer simulation on Simulink. Feedback from a pulse oximeter was used to maintain a target SpO(2) of 91% by changing the oxygen flow-rate to the patient. The controller was evaluated using a model to approximate the patient's arterial oxygen saturation response, including hypoxic events from artificial disturbances as well as recorded patient oximetry data.

RESULTS

The simulated controller produced improvement in arterial oxygen saturation throughout a wide range of disturbance frequencies. It suppressed disturbances with periods greater than a couple of minutes by more than -10 dB. When evaluated with patient oximetry recordings, the controller on average reduced the time spent with arterial blood saturation below threshold by 76%. Given the same volume of oxygen, the closed-loop controller also produced a 63% improvement compared to fixed flow-rate LTOT.

CONCLUSIONS

The simulation findings indicate an optimized matching between oxygen supply and demand, maintaining SpO(2) above threshold to improve therapeutic efficacy compared to standard LTOT.

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.

Long-term oxygen therapy in chronic respiratory failure: A Multicenter Italian Study on Oxygen Therapy Adherence (MISOTA)

BACKGROUND

The adherence to the prescribed oxygen therapy is difficult to obtain for patients on long-term oxygen therapy (LTOT). There is little information on the modalities of oxygen utilisation for patients on LTOT who are using liquid oxygen in real life.

STUDY OBJECTIVE

Evaluation of the behaviour and the knowledge regarding LTOT in a large group of patients mainly using liquid oxygen.

DESIGN AND SETTING

Questionnaire administered to consecutive outpatients on domiciliary LTOT for at least 6 months referring to one of 20 clinics throughout Italy. Blinded to this result, the physician who cared for the patient completed another questionnaire.

RESULTS

We evaluated 1504 patients (mean age 71.6 years; males 64%; 74% suffering from COPD). Most respondents (93%) used liquid oxygen with mobile device. Fifteen per cent of patients had a prescribed length of oxygen therapy less than 15 h/day; 21% reported to practice oxygen for less than 15 h/day. Patients reported using oxygen for less hours than had been prescribed during the day at rest (P=0.02, k=0.80) during exercise (P=0.002, k=0.72) and at night (P=0.0036, k=0.77). There was no difference between the flow prescribed by the physician and that known and practised by the patient at rest or during sleep; during exercise the flow reported by patients was lower than that prescribed by the physician. Patients used in the night but not at rest or during exercise, a lower level of oxygen flow than what they knew had been prescribed. Fifty-five per cent of patients received indications to modify the oxygen flow in the various situations of life. Liquid oxygen was almost always useful to decrease breathlessness. Most (84%) patients possessed a mobile device, but only 40% declared they used it daily, 'shame' being indicated as the principal barrier. On the physicians' side, we found that the criteria used in prescribing did not always correspond to evidence-based recommendations.

CONCLUSION

The widespread use of liquid oxygen did not automatically assure optimal adherence to the prescribed treatment as regards times and modality of oxygen use. A better education of patients, relatives, and the general public, as well as increased self-assessment on the part of health caregivers would improve the practice of LTOT in Italy.

Efficacy of the 6-Minute Walk Test in Evaluating Ambulatory Oxygen Therapy

OBJECTIVE

To compare oxyhemoglobin saturation (SpO2) observed during the 6-minute walk test with that of pulse oximetry carried out during activities of daily living (ADLs). The efficacy of the 6-minute walk test for determining adequate oxygen flow to prevent arterial desaturation during ADLs was also analyzed.

PATIENTS AND METHODS

We studied 37 patients diagnosed with chronic obstructive pulmonary disease (COPD)--mean (SD) forced expiratory volume in 1 second, 26% (9%) of predicted--and compared SpO2 values obtained in the 6-minute walk test with those obtained with ambulatory pulse oximetry during ADLs. Eleven of the 20 patients with exercise-induced desaturation agreed to use portable liquid oxygen and were randomized to ambulatory pulse oximetry on 2 consecutive days, both with and without the administration of oxygen. Oxygen flow was adjusted on successive 6-minute walk tests until a mean SpO2 greater than 85% was reached.

RESULTS

The mean SpO2 for all patients was 84% (7%) during the 6-minute walk test and 89% (4%) during ADLs (P<.001). Cumulative percentages of time with SpO2 less than 90%, 88%, and 85% were higher during the 6-minute walk test than during ADLs (P<.001). During the walk test, desaturation was detected in 27% of patients, but was not confirmed by ambulatory pulse oximetry during ADLs. In the subgroup of 11 patients using portable liquid oxygen no significant differences were found between SpO2 values recorded during the walk test and during ADLs with the appropriate oxygen flow.

CONCLUSION

The 6-minute walk test is an effective method for detecting desaturation during ADLs and for establishing the oxygen flow needed to correct exercise-induced desaturation.

COPD in VA hospitals

The Department of Veterans Affairs (VA) Health Care System is the largest integrated single-payer system in the United States. Its primary mission is to provide primary care, specialized care, and related medical and social support services to veterans. Much time and resources are expended on chronic obstructive pulmonary disease, known as COPD, at VA hospitals and clinics, thereby justifying the development of multifaceted strategies to address this problem. This article discusses the special problems of COPD in veterans who use VA facilities. The article also highlights the contributions of the VA to the research, training, and development of clinical practice guidelines for the management of this pervasive disease and presents the challenges that threaten its role in this area.

The clinical utility of arterialized earlobe capillary blood in the assessment of patients for long-term oxygen therapy

The prescription of long-term oxygen (LTOT) is underpinned by the measurement of arterial PO2, generally obtained by radial artery puncture. This test is commonly associated with patient discomfort and a test that is reliable, well-tolerated and non-invasive would be advantageous. Cutaneous oximetry has not proved sufficiently accurate. Arterialized earlobe capillary sampling has been proposed, with some authors stating that it is under-utilized. However, to date studies have yielded conflicting results and the clinical utility remains uncertain. Our regional oxygen service based at a specialist respiratory hospital undertook a prospective study of consecutive patients with chronic respiratory disease undergoing assessment for LTOT. Simultaneous radial artery and arterialized earlobe sampling was performed. Rigorous steps were taken to ensure optimal arterialization of the earlobe samples. Agreement between arterial and arterialized PO2 and PCO2 was compared using the Bland-Altman method. One hundred patients were studied. Procedural difficulties (insufficient sample or air in sample) were similar for both procedures, however clotting occurred more frequently in arterialized earlobe samples. Sixty-four sample pairs were available for comparison. The bias and limits of agreement between arterialized and arterial PO2 were wide, mean (+/- 2 SD), -048 (-2.05-1.09) kPa. The bias and limits of agreement for PCO2 were smaller. Using the absolute criterion (arterial PO2 < 7.3 kPa), 9/55 (16%) patients would receive oxygen inappropriately based on the arterialized earlobe sample. Conversely, no patients would have been denied LTOT. Radial artery puncture gave rise to significantly greater discomfort (P < 0.0001) and level of concern (P < 0.0001). Patient preference strongly favoured arterialized earlobe sampling. However, despite rigorous attention to arterialization earlobe sampling was insufficiently accurate to replace radial artery puncture in the prescription of LTOT.

Development and testing of formal protocols for oxygen prescribing

The absence of standardized assessment protocols with well- defined measurement properties limits comparison of outcomes among those receiving long-term oxygen therapy (LTOT). We describe simple protocols for a hospital test, a simulated home test, and an actual home test, their reliability and relationship to each other. Stable patients with exercise hypoxemia participated. In 74 patients who completed four exercise tests, correlations between tests ranged from 0.85 to 0.78. Of these 27.0% had the same prescription from all four tests. In 46% prescriptions were within 1 L/ min and in 27% within 2 L/min. During exercise the hospital tests suggested slightly higher oxygen prescriptions than did the simulated home tests (2.5 L/min versus 2.0 L/min, p < 0.001). In 23 patients who participated in actual home assessments, the correlations between the home test, the hospital, and the simulated home tests were 0.22 (95% CI -0.24 to 0.67) and 0.27 (95% CI -0.18 to 0.72). In conclusion, standardizing tests for the assessment of LTOT is important. We describe simple hospital and simulated home tests that are reproducible, easy to carry out, and correlate well with each other.