Correction: Detection of obstructive sleep apnea using Belun Sleep Platform wearable with neural network-based algorithm and its combined use with STOP-Bang questionnaire

[This corrects the article DOI: 10.1371/journal.pone.0258040.].

Depressive Symptoms and Sleep Quality Mediate the Relationship Between Race and Quality of Life Among Patients With Heart Failure: A Serial Multiple Mediator Model

BACKGROUND

Black patients with heart failure (HF) report worse quality of life (QoL) than White patients. Few investigators have examined mediators of the association between race and QoL, but depressive symptoms and sleep quality are associated with QoL.

OBJECTIVE

The aim of this study was to determine whether depressive symptoms and sleep quality are mediators of the relationship between race and QoL among patients with HF.

METHODS

This was a cross-sectional study. We included 271 outpatients with HF. Self-reported race (White/Black), depressive symptoms (Patient Health Questionnaire), sleep quality (Pittsburgh Sleep Quality Index), and QoL (Kansas City Cardiomyopathy Questionnaire) were collected at baseline. A serial multiple mediator analysis was conducted using the PROCESS macro for SPSS.

RESULTS

Ninety-six patients (35.4%) were Black. Black participants reported higher levels of depressive symptoms and poorer sleep quality than White participants. Race was not directly associated with QoL but indirectly associated with QoL through depressive symptoms and poorer sleep quality. Because of higher levels of depressive symptoms and poorer sleep quality, Black participants reported poorer QoL than White participants.

CONCLUSIONS

Depressive symptoms and sleep quality together mediated the relationship between race and QoL. These findings suggest that screening for depressive symptoms and sleep quality could identify patients at risk for poor QoL, especially in Black patients.

Consumer Wearable Sleep Trackers: Are They Ready for Clinical Use?

As the importance of good sleep continues to gain public recognition, the market for sleep-monitoring devices continues to grow. Modern technology has shifted from simple sleep tracking to a more granular sleep health assessment. We examine the available functionalities of consumer wearable sleep trackers (CWSTs) and how they perform in healthy individuals and disease states. Additionally, the continuum of sleep technology from consumer-grade to medical-grade is detailed. As this trend invariably grows, we urge professional societies to develop guidelines encompassing the practical clinical use of CWSTs and how best to incorporate them into patient care plans.

Belun Ring (Belun Sleep System BLS-100): Deep learning-facilitated wearable enables obstructive sleep apnea detection, apnea severity categorization, and sleep stage classification in patients suspected of obstructive sleep apnea

GOAL AND AIMS

Our objective was to evaluate the performance of Belun Ring with second-generation deep learning algorithms in obstructive sleep apnea (OSA) detection, OSA severity categorization, and sleep stage classification.

FOCUS TECHNOLOGY

Belun Ring with second-generation deep learning algorithms REFERENCE TECHNOLOGY: In-lab polysomnography (PSG) SAMPLE: Eighty-four subjects (M: F = 1:1) referred for an overnight sleep study were eligible. Of these, 26% had PSG-AHI<5; 24% had PSG-AHI 5-15; 23% had PSG-AHI 15-30; 27% had PSG-AHI ≥ 30.

DESIGN

Rigorous performance evaluation by comparing Belun Ring to concurrent in-lab PSG using the 4% rule.

CORE ANALYTICS

Pearson's correlation coefficient, Student's paired t-test, diagnostic accuracy, sensitivity, specificity, positive predictive value, negative predictive value, positive likelihood ratio, negative likelihood ratio, Cohen's kappa coefficient (kappa), Bland-Altman plots with bias and limits of agreement, receiver operating characteristics curves with area under the curve, and confusion matrix.

CORE OUTCOMES

The accuracy, sensitivity, specificity, and kappa in categorizing AHI ≥ 5 were 0.85, 0.92, 0.64, and 0.58, respectively. The accuracy, sensitivity, specificity, and Kappa in categorizing AHI ≥ 15 were 0.89, 0.91, 0.88, and 0.79, respectively. The accuracy, sensitivity, specificity, and Kappa in categorizing AHI ≥ 30 were 0.91, 0.83, 0.93, and 0.76, respectively. BSP2 also achieved an accuracy of 0.88 in detecting wake, 0.82 in detecting NREM, and 0.90 in detecting REM sleep.

CORE CONCLUSION

Belun Ring with second-generation algorithms detected OSA with good accuracy and demonstrated a moderate-to-substantial agreement in categorizing OSA severity and classifying sleep stages.

In search of a better CPAP interface: A network meta-analysis comparing nasal masks, nasal pillows and oronasal masks

Until now, no study has directly network meta-analysed the impact of nasal masks, nasal pillows and oronasal masks on continuous positive airway pressure therapy in patients with obstructive sleep apnea. This study aimed to meta-analyse the impact of three kinds of nasal interfaces with both network meta-analysis and pairwise comparison. PubMed, EMBASE, CENTRAL and ClinicalTrials.gov were systematically searched from inception to December 2020 for studies that compared the three types of nasal interfaces for treating obstructive sleep apnea with continuous positive airway pressure. The outcomes were residual apnea-hypopnea index, continuous positive airway pressure, and nightly average usage. The network meta-analysis was conducted using multivariate random-effects in a frequentist framework where three interfaces were ranked with the surface under the cumulative ranking probabilities. The pairwise comparison was conducted using random-effects meta-analysis. Twenty-nine articles comprising 6378 participants were included. The pairwise comparison showed both nasal masks and nasal pillows were associated with lower residual apnea-hypopnea index, lower continuous positive airway pressure, and higher continuous positive airway pressure adherence compared with oronasal masks. The surface under the cumulative ranking confirmed that nasal masks were associated with the lowest residual apnea-hypopnea index and highest adherence, while pillows were associated with the lowest continuous positive airway pressure. The meta-regression identified that lower pretreatment apnea-hypopnea index and continuous positive airway pressure determined during continuous positive airway pressure titration (versus determined during continuous positive airway pressure therapy) was associated with lower continuous positive airway pressure with nasal masks and nasal pillows. In conclusion, compared with oronasal masks, nasal masks and nasal pillows are better interfaces, especially in patients with lower pretreatment apnea-hypopnea index and those with the therapeutic pressure determined during continuous positive airway pressure titration.

Detection of obstructive sleep apnea using Belun Sleep Platform wearable with neural network-based algorithm and its combined use with STOP-Bang questionnaire

Many wearables allow physiological data acquisition in sleep and enable clinicians to assess sleep outside of sleep labs. Belun Sleep Platform (BSP) is a novel neural network-based home sleep apnea testing system utilizing a wearable ring device to detect obstructive sleep apnea (OSA). The objective of the study is to assess the performance of BSP for the evaluation of OSA. Subjects who take heart rate-affecting medications and those with non-arrhythmic comorbidities were included in this cohort. Polysomnography (PSG) studies were performed simultaneously with the Belun Ring in individuals who were referred to the sleep lab for an overnight sleep study. The sleep studies were manually scored using the American Academy of Sleep Medicine Scoring Manual (version 2.4) with 4% desaturation hypopnea criteria. A total of 78 subjects were recruited. Of these, 45% had AHI < 5; 18% had AHI 5-15; 19% had AHI 15-30; 18% had AHI ≥ 30. The Belun apnea-hypopnea index (bAHI) correlated well with the PSG-AHI (r = 0.888, P < 0.001). The Belun total sleep time (bTST) and PSG-TST had a high correlation coefficient (r = 0.967, P < 0.001). The accuracy, sensitivity, specificity in categorizing AHI ≥ 15 were 0.808 [95% CI, 0.703-0.888], 0.931 [95% CI, 0.772-0.992], and 0.735 [95% CI, 0.589-0.850], respectively. The use of beta-blocker/calcium-receptor antagonist and the presence of comorbidities did not negatively affect the sensitivity and specificity of BSP in predicting OSA. A diagnostic algorithm combining STOP-Bang cutoff of 5 and bAHI cutoff of 15 events/h demonstrated an accuracy, sensitivity, specificity of 0.938 [95% CI, 0.828-0.987], 0.944 [95% CI, 0.727-0.999], and 0.933 [95% CI, 0.779-0.992], respectively, for the diagnosis of moderate to severe OSA. BSP is a promising testing tool for OSA assessment and can potentially be incorporated into clinical practices for the identification of OSA. Trial registration: ClinicalTrial.org NCT03997916 https://clinicaltrials.gov/ct2/show/NCT03997916?term=belun+ring&draw=2&rank=1.

Belun Ring Platform: a novel home sleep apnea testing system for assessment of obstructive sleep apnea

STUDY OBJECTIVES

The objective of the study is to validate the performance of Belun Ring Platform, a novel home sleep apnea testing system using a patented pulse oximeter sensor and a proprietary cloud-based neural networks algorithm.

METHODS

The Belun Ring captures oxygen saturation, photoplethysmography, and accelerometer signals. The Belun Ring total sleep time is derived from features extracted from accelerometer, oxygen saturation, and photoplethysmography signals. The Belun Ring respiratory event index is derived from Belun Ring total sleep time and features extracted from heart rate variability and oxygen saturation changes. A total of 50 adults without significant cardiopulmonary or neuromuscular comorbidities and heart rate affecting medications were evaluated. In-lab sleep studies were performed simultaneously with the Ring and the studies were manually scored using the American Academy of Sleep Medicine Scoring Manual 4% desaturation criteria.

RESULTS

The Belun Ring respiratory event index correlated well with the polysomnography-apnea-hypopnea index (AHI; r = .894, P < .001). The sensitivity and specificity in categorizing AHI ≥ 15 events/h were 0.85 and 0.87, respectively, and the positive predictive value and negative predictive value were 0.88 and 0.83, respectively. The Belun Ring total sleep time also correlated well with the polysomnography-total sleep time (r = .945, P < .001). Although the Belun Ring Platform has a good overall performance, it tends to overestimate AHI in individuals with AHI under 15 events/h and underestimate AHI in those with AHI over 15 events/h. Conclusions: In this proof-of-concept study, the Belun Ring Platform demonstrated a reasonable accuracy in predicting AHI and total sleep time in patients without significant comorbidities and heart rate-affecting medications.

CLINICAL TRIAL REGISTRATION

Registry: ClinicalTrials.gov; Name: Validation of a Novel Device for Screening Patients With Symptoms of Obstructive Sleep Apnea; URL: https://clinicaltrials.gov/ct2/show/NCT04121923; Identifier: NCT04121923.

Support vector machine prediction of obstructive sleep apnea in a large-scale Chinese clinical sample

STUDY OBJECTIVES

Polysomnography is the gold standard for diagnosis of obstructive sleep apnea (OSA) but it is costly and access is often limited. The aim of this study is to develop a clinically useful support vector machine (SVM)-based prediction model to identify patients with high probability of OSA for nonsleep specialist physician in clinical practice.

METHODS

The SVM model was developed using the features routinely collected at the clinical evaluation from 6,875 Chinese patients referred to sleep clinics for suspected OSA. Three apnea-hypopnea index (AHI) cutoffs, ≥5/h, ≥15/h, and ≥30/h were used to define the severity of OSA. The continuous and categorized features were selected separately and were further selected through stepwise forward feature selection. The modeling was achieved through fivefold cross-validation. The model discriminative ability was evaluated for the whole data set and four subgroups categorized with gender and age (<65 versus ≥65 years old [y/o]).

RESULTS

Two features were selected to predict AHI cutoff ≥5/h with six features selected for ≥15/h, and six features selected for ≥30/h, respectively, to reach Area under the Receiver Operating Characteristic (AUROC) 0.82, 0.80, and 0.78, respectively. The sensitivity was 74.14%, 75.18%, and 70.26%, while the specificity was 74.71%, 68.73%, and 70.30%, respectively. Compared to logistic regression, Berlin questionnaire, NoSAS Score, and Supersparse Linear Integer Model (SLIM) scoring system, the SVM model performs better with a more balanced sensitivity and specificity. The discriminative ability was best for male <65 y/o and modest for female ≥65 y/o.

CONCLUSION

Our model provides a simple and accurate modality for early identification of patients with OSA and may potentially help prioritize them for sleep study.

Obstructive sleep apnea and chronic intermittent hypoxia: a review

Hypoxia is an important topic both physiologically and clinically. Traditionally, physiology research has been focusing on the effect of acute and chronic sustained hypoxia and human adaptive response to high altitude. In the past 20 years, genetic studies by many have expanded our understanding of hypoxia to the molecular level. However, in contrast to our extensive knowledge about acute and chronic sustained hypoxia, we know relatively little about the effect of chronic intermittent hypoxia (CIH). In recent years, CIH has attracted more research attention because of the increasing prevalence of obesity and obstructive sleep apnea (OSA) in the western countries. Clinically, CIH is commonly seen in patients with sleep-disordered breathing including OSA, Cheyne-Stokes respiration and nocturnal hypoventilation. It was estimated that for OSA of at least mild severity prevalence estimates range from 3 to 28% in the general population. OSA is characterized by recurrent upper airway collapse during sleep leading to intermittent nocturnal hypoxia and sleep fragmentation. OSA is associated with significant mortality and morbidity including neurocognitive dysfunction, hypertension, many cardiovascular disorders and metabolic disorders such as diabetes and metabolic syndrome. The intermittent hypoxia in OSA closely mimics what is seen in the ischemia-reperfusion injury. Experimentally, there is no universally accepted definition for CIH. Laboratory protocols vary greatly in duration of hypoxia exposure, numbers of hypoxia episodes per day and the total number of days of exposure. Despite the lack of a uniform definition, recent data suggest that CIH may lead to multiple long-term pathophysiologic consequences similar to what we see in patients with OSA. Recent evidences also demonstrate that there are remarkable differences in the response of the physiologic systems to sustained hypoxia and intermittent hypoxia. This review is aimed to briefly discuss the clinical significance of sleep-disordered breathing and our current understanding of CIH.

Prediction of postoperative lung function in patients with lung cancer: comparison of quantitative CT with perfusion scintigraphy

OBJECTIVE

Prediction of postoperative lung function is important in preoperative evaluation of patients with lung cancer. Perfusion scintigraphy is the current method to assess the fractional contribution of lung function of the remaining lung. We developed a quantitative CT method and compared it with perfusion scintigraphy for predictions of postoperative forced expiratory volume in 1 sec (FEV1) in patients with lung cancer.

SUBJECTS AND METHODS

Forty-four patients with lung cancer undergoing lung resection with preoperative CT and perfusion scintigraphy were enrolled. Quantitative CT used a dual threshold (-500 and -910 H) on standard preoperative CT to semiautomatically extract lung volume without emphysema or tumor and atelectasis, which we defined as "functional lung volume." Prediction was calculated from preoperative FEV1 multiplied by the fractional contribution of functional lung volume of the remaining lung by quantitative CT. Perfusion scintigraphy was the standard method. Predictions were correlated with postoperatively measured FEV1.

RESULTS

Both quantitative CT and perfusion scintigraphy predicted postoperative FEV1 well in patients who underwent pneumonectomy (n = 28, r = 0.88 vs r = 0.86) and in lobectomy (n = 16, r = 0.90 vs r = 0.80) (both, p < 0.001). There was good agreement between the two methods by the Bland-Altman method. In the four patients with low measured postoperative FEV1 (<40% predicted normal), quantitative CT had true-positive prediction in four and perfusion scintigraphy, in only two.

CONCLUSION

Given its simplicity, we proposed that quantitative CT be widely used in predicting postoperative FEV1.

Association of Sauropus androgynus and bronchiolitis obliterans syndrome: a hospital-based case-control study

In late April 1995, an outbreak of a poorly defined respiratory illness related to the ingestion of leaves of Sauropus androgynus was observed in southern Taiwan. To further evaluate the association between S. androgynus and bronchiolitis obliterans syndrome, a hospital-based case-control study was conducted with one case group and three different control groups at Veterans General Hospital-Kaohsiung between April and September 1995. A total of 54 cases (50 females, 4 males), 54 age- and sex-matched neighborhood controls, 54 matched routine physical check-up controls, and 54 matched self-referred patron controls (who had ingested S. androgynus yet without obstructive physiology) were interviewed for clinical symptoms, history of S. androgynus consumption, and potential confounding factors. All 54 cases (100%) ingested S. androgynus compared with only five (9%) neighborhood controls (matched odds ratio (OR) incalculable, p < 0.001) and two (4%) physical check-up controls (matched OR incalculable, p < 0.001). In the univariate analysis of 54 cases and 54 self-referred patron controls, factors associated with an increased risk of bronchiolitis obliterans syndrome were methods of food preparation (uncooked juice vs. stir fried or boiled dishes, matched OR 10.3 (95% confidence interval (CI) 1.3-84.4)); preparer of the S. androgynus-containing food (vendor only vs. patient only or patient plus vendor, matched OR 2.8 (95% CI 1.1-7.1)); total S. androgynus consumption quantity (> 4,500 vs. 413-2,063 g, matched OR 10.0 (95% CI 1.9-53.0)); duration of consumption (> 45 vs. 6-24 days, matched OR 2.1 (95% CI 1.2-3.8)); and midterm interruption (< 2 vs. 2-5 days per week, matched OR 2.6 (95% CI 1.1-6.1)). Additionally, multiple conditional logistic regression analysis of cases and self-referred patron controls revealed that a larger total amount of S. androgynus consumption, preparation of S. androgynus food without cooking, and ingesting S. androgynus food prepared by a vendor were the significant risk factors associated with bronchiolitis obliterans syndrome.

Correlation of high-resolution CT and pulmonary function in bronchiolitis obliterans: a study based on 24 patients associated with consumption of Sauropus androgynus

OBJECTIVE

An outbreak of Sauropus androgynus-associated bronchiolitis obliterans occurred in Taiwan in the summer of 1995. We undertook a study of the correlation between high-resolution CT findings and pulmonary function testing in patients from this outbreak.

MATERIALS AND METHODS

We evaluated inspiratory-expiratory high-resolution CT scans of 24 patients with S. androgynus-associated bronchiolitis obliterans. The presence of bronchiectasis was assessed by two visual scores (a bronchial dilatation score and a bronchiectasis extent score). Extent of air-trapping was assessed visually and given a score. We also used computer software to assess the extent of air-trapping and generate scores of dynamic attenuation. Spirometry, plethysmography, and diffusion capacity of each patient were also obtained.

RESULTS

All four scores had statistically significant correlation with forced expiratory volume in 1 sec (FEV1) (p < .05 for both bronchiectasis scores; p < .001 for both air-trapping scores). The two air-trapping scores had statistically significant correlation with forced vital capacity and diffusion capacity. We found the scores for dynamic attenuation had the greatest correlation with FEV1 (r = .85). We also found that mosaic attenuation was notable on expiratory CT scans alone in nine patients (type 1 air-trapping) and on both inspiratory and expiratory CT scans in 15 patients (type 2 air-trapping). In the latter group, FEV1 was significantly lower (p < .01).

CONCLUSION

Findings from high-resolution CT of air-trapping were more important than findings of bronchiectasis when correlating pulmonary function with S. androgynus-associated bronchiolitis obliterans. Type 2 air-trapping suggested a more severe air-flow obstruction than did type 1. Scores for quantitative attenuation generated by computer software were helpful in assessing air-trapping and correlating it with pulmonary function. These findings may apply to patients with bronchiolitis obliterans from other causes.

The outcome of terminal liver cirrhosis patients requiring mechanical ventilation

BACKGROUND

Liver cirrhosis is a common problem in Taiwan. Without liver transplantation, patients with end-stage liver cirrhosis frequently die of various complications and often require mechanical ventilatory support prior to their death. The purpose of this study was to investigate the in-hospital and short-term outcome of such patients.

METHODS

A retrospective review of 47 medical records of mechanically ventilated patients with primary diagnosis of liver cirrhosis, admitted from November 1990 to September 1993, allowed analysis of disease course and outcome for these patients.

RESULTS

Among the 47 patients, a Child-Pugh's class A patient receiving temporary mechanical ventilation (MV) after elective devascularization surgery was excluded from analysis. Among the remaining medically treated 46 patients, there were 33 Child-Pugh's class C patients, 9 class B patients and 4 unclassified patients. Primary reasons for endotracheal intubation and MV included airway protection, acute respiratory distress and shock. Of these patients, shock was present in 39 cases, upper gastrointestinal bleeding in 34, systemic inflammatory response syndrome in 32, renal insufficiency with creatinine greater than 1.3 mg/dl in 32, bacteremia in 14, parenchymal lung disease in 16, spontaneous bacterial peritonitis in 10, and intracerebral hemorrhage in 1 during their hospital courses. Thirty-eight patients (83%) died within 72 hours after being placed on mechanical ventilation. Patients requiring MV with complications of bacteremia, parenchymal lung disease or renal insufficiency during hospitalization were found to have a 100% mortality rate. Successful weaning occurred in only 3 of 46 patients (8.7%). Of these three, two (4.3%) went home alive and had survived over six months after discharge.

CONCLUSIONS

It was concluded that cirrhotic patients requiring MV have an extremely poor prognosis. Patients and their families should be fully informed of the prognosis, and routine use of MV should not be encouraged in patients with terminal stage liver disease.

Effectiveness of a continuous quality improvement program aiming to reduce unplanned extubation: a prospective study

OBJECTIVE

To evaluate the effectiveness of a continuous quality improvement (CQI) program in reducing the incidence of unplanned endotracheal extubation.

DESIGN

Prospective study over a 9-month period.

SETTING

Adult intensive care units (ICUs including coronary care unit, medical ICU, surgical ICU, and cardiovascular surgical ICU) in a university-affiliated medical center.

PATIENTS

831 consecutive mechanically ventilated patients.

INTERVENTIONS

CQI program focusing on standardization of procedures, improvement of communication, and identification and management of high-risk patients.

MEASUREMENTS AND RESULTS

With the implementation of this CQI program, the overall incidence density of unplanned extubation (defined as number of new unplanned extubations per mechanical ventilation patient-days) significantly decreased from 2.6% in the first trimester to 1.5% in the second trimester and 1.2% in the third trimester (p = 0.01). This reduction was essentially the result of a decrease in unplanned extubation in orally intubated patients (incidence density 4.6, 1.7 and 1.0% for three trimesters, respectively; p < 0.0001). Unplanned extubation in nasally intubated patients remained largely unaffected (1.2, 1.4, and 1.4% for three trimesters, respectively; p = 0.92).

CONCLUSIONS

The implementation of a concerted CQI program is effective in reducing the overall incidence of unplanned endotracheal extubation.

Outbreak of bronchiolitis obliterans associated with consumption of Sauropus androgynus in Taiwan

BACKGROUND

In August, 1995, there was an outbreak in Taiwan of rapidly progressive respiratory distress associated with consumption of uncooked Sauropus androgynus, a vegetable with a claimed yet unconfirmed effect on weight control. We report on 23 patients with strikingly similar clinical presentations.

METHODS

A structured questionnaire for clinical manifestations was completed. Radiographic findings, pulmonary physiological changes, immunological and microbiological studies, and pathological examination were evaluated.

FINDINGS

All patients were young and middle-aged women (mean age 39 years [range 21-52]). They took uncooked S androgynus juice, generally mixed with guava or pineapple juice, for a mean duration of 10 weeks. Progressive dyspnoea and persistent cough were the main symptoms on presentation. Pulmonary function testing uniformly revealed moderate to severe airflow obstruction with mean forced expiratory volume in 1 s (FEV1) of 0.66 L (26% of predicted). No bronchodilator response was observed. Room-air arterial blood gas analysis showed hypoxaemia (mean PaO2 9.6 [SD 1.6] kPa). Chest radiographs were essentially normal. High-resolution computed tomography showed bilateral bronchiectasis and patchy low attenuation of lung parenchyma with mosaic perfusion. Ventilation-perfusion scintigraphic findings were compatible with obstructive lung disease. Histopathology of open lung biopsy specimens in four patients confirmed the presence of bronchiolitis obliterans. Immunohistochemical stains of the open lung biopsy specimens showed predominance of T cells over B cells. Immunofluorescent stains for IgG, IgM, IgA, C1q, C3, and C4 were negative. Serum concentrations of tumour necrosis factor alpha were higher than those of normal controls. Clinical response to prednisolone was limited.

INTERPRETATION

We describe an unusual association between bronchiolitis obliterans and ingestion of the vegetable S androgynus. T-cell mediated immunity may be involved in the pathogenesis.

[Outcome and cost of mechanical ventilation in patients with inoperable solid tumors and hematologic malignancies]

The application of mechanical ventilation can be life-saving in patients with acute respiratory failure, but is frequently ineffective in terminally ill patients. To analyze the outcome and cost of mechanical ventilation for patients with malignancies, we retrospectively reviewed 115 patients with inoperable solid tumors or hematologic malignancies who received mechanical ventilation. Eighty eight of these 115 patients (77%) died while on mechanical ventilation; 18 patients (16%) were weaned from mechanical ventilation but still died during their hospitalization. Six patients (5%) were discharged but survived less than 3 months and only three patients (3%) survived for more than 3 months after discharge. The total time of mechanical ventilation was 772 person-days, which represented 5.5% (772/13974) of the total mechanical ventilator use in our hospital in 1993. The total hospital cost from initiation of mechanical ventilation to discharge or death of these 115 patients was NT $11,238,022 (US $432,200) and daily hospital cost per person during mechanical ventilation was approximately NT $10,845 (US $420). The "daily cost of discharge survival" (defined as total hospitalization cost from the initiation of mechanical ventilation to discharge or death divided by total discharge person-days) for patients with inoperable solid tumors was NT $73,421 (US $2,820)/per person-day. We concluded that mechanical ventilation should not be routinely used in patients with inoperable solid tumors and hematologic malignancies. Physicians should explain the poor outcome to these patients and their families in advance and inquire about their willingness to forego mechanical ventilation.

Use of noninvasive positive pressure ventilation via nasal mask in patients with respiratory distress after extubation

BACKGROUND

Noninvasive positive pressure ventilation (NIPPV) has been successfully applied to provide ventilatory support in patients with chronic respiratory insufficiency as well as in selected patients with acute respiratory failure of various etiologies. To investigate the effectiveness of NIPPV via nasal mask in patients who develop respiratory distress after extubation, we prospectively studied 19 such patients (14 elective extubations and 5 self-extubations) who required no immediate reintubation.

METHODS

The BiPAP ventilatory support system (BiPAP S/T-D, Respironics Inc., Murrysville, PA) via nasal mask was used to provide NIPPV in each patient. Inspiratory pressure support was adjusted to achieve comfort as well as adequate oxygenation and ventilation.

RESULTS

Eleven patients were successfully transferred to regular oxygen supplement after an average trial of 38 hours. Persistent oral air leak despite the application of chin strap was observed in four of the eight failure cases and appeared to be the leading cause of NIPPV failure. When these patients were excluded, a success rate of 73% was achieved. Other factors contributing to failure included persistent hypoxemia, inadequate ventilation, worsening of underlying diseases and bronchial secretions. No major complication related to the use of NIPPV was observed. In the success group, respiratory rate significantly decreased by an average of 10 breaths/min at one hour after the commencement of NIPPV (p < 0.01). No significant changes of heart rate, blood pressure, Paco2 and pH were noted in either group.

CONCLUSIONS

NIPPV via nasal mask may be considered as an alternative to endotracheal reintubation in selected extubated patients with respiratory distress who require no immediate reintubation.

Demand-flow airway pressure release ventilation as a partial ventilatory support mode: comparison with synchronized intermittent mandatory ventilation and pressure support ventilation

OBJECTIVE

To evaluate airway pressure release ventilation as a partial ventilatory support mode by comparing a demand-flow airway pressure release ventilation system with synchronized intermittent mandatory ventilation and pressure support ventilation.

DESIGN

Prospective, nonrandomized, cross-over trial.

SETTING

Medical intensive care unit in a university medical center.

PATIENTS

Sixteen consecutive patients without chronic obstructive pulmonary disease with mechanical ventilatory support of 25% to 75% of total minute ventilation on synchronized intermittent mandatory ventilation, or 25% to 75% of maximal pressure support level on pressure support ventilation.

INTERVENTIONS

Each mode of mechanical ventilation was supplied to patients with comparable levels of partial support for 30 mins.

MEASUREMENTS AND MAIN RESULTS

Among three different modes, demand-flow airway pressure release ventilation achieved the lowest peak airway pressure (airway pressure release ventilation 9.1 +/- 2.6 cm H2O; pressure support ventilation 18.4 +/- 4.6 cm H2O; synchronized intermittent mandatory ventilation 34.8 +/- 7.7 cm H2O; p < .001). Hemodynamic status and oxygenation status were similar among these three modes. Five (31%) of the 16 patients felt that demand-flow airway pressure release ventilation was a less comfortable mode than synchronized intermittent mandatory ventilation or pressure support ventilation. This finding had no clear correlation with their duration of airway pressure release, preset machine deflation rate, or inspiratory/expiratory ratio of machine breath. Gross asynchrony of effort and ventilator cycling was noticed in two (13%) patients while they were receiving demand-flow airway pressure release ventilation.

CONCLUSIONS

We conclude that for patients who do not have chronic obstructive pulmonary disease, demand-flow airway pressure release ventilation can provide effective partial ventilatory support with lower peak airway pressure when compared with pressure support ventilation and synchronized intermittent mandatory ventilation. However, this airway pressure release ventilation system may be less comfortable than the other two modes, and asynchrony may occur in some patients.

Use of quantitative CT to predict postoperative lung function in patients with lung cancer

PURPOSE

To evaluate the effectiveness of quantitative computed tomography (CT) for predicting postoperative lung function in patients with lung cancer.

MATERIALS AND METHODS

Preoperative spirometry and conventional CT of the chest were performed in 38 patients. A postprocessing CT program was applied to quantitate the volume of whole-lung parenchyma with attenuations of -500 to -910 HU; this was defined as total functional lung volume (TFLV). The regional functional lung volume (RFLV) of the lobes or lung to be resected was quantitated separately. CT-predicted postoperative forced expiratory volume in 1 second (FEV1) and forced vital capacity (FVC) were derived by multiplying the preoperative spirometry values by (1 - RFLV/TFLV).

RESULTS

CT-predicted values correlated well with postoperatively measured results (FEV1: r = .93, P < .001; FVC: r = .86, P < .001) in patients who underwent pneumonectomy or lobectomy, regardless of the patient's preoperative ventilation status.

CONCLUSION

This method is effective in the prediction of postoperative FEV1 and FVC in patients undergoing pulmonary resection.