Basing intubation of acutely hypoxemic patients on physiologic principles.

The decision to intubate a patient with acute hypoxemic respiratory failure who is not in apparent respiratory distress is one of the most difficult clinical decisions faced by intensivists. A conservative approach exposes patients to the dangers of hypoxemia, while a liberal approach exposes them to the dangers of inserting an endotracheal tube and invasive mechanical ventilation. To assist intensivists in this decision, investigators have used various thresholds of peripheral or arterial oxygen saturation, partial pressure of oxygen, partial pressure of oxygen-to-fraction of inspired oxygen ratio, and arterial oxygen content. In this review we will discuss how each of these oxygenation indices provides inaccurate information about the volume of oxygen transported in the arterial blood (convective oxygen delivery) or the pressure gradient driving oxygen from the capillaries to the cells (diffusive oxygen delivery). The decision to intubate hypoxemic patients is further complicated by our nescience of the critical point below which global and cerebral oxygen supply become delivery-dependent in the individual patient. Accordingly, intubation requires a nuanced understanding of oxygenation indexes. In this review, we will also discuss our approach to intubation based on clinical observations and physiologic principles. Specifically, we consider intubation when hypoxemic patients, who are neither in apparent respiratory distress nor in shock, become cognitively impaired suggesting emergent cerebral hypoxia. When deciding to intubate, we also consider additional factors including estimates of cardiac function, peripheral perfusion, arterial oxygen content and its determinants. It is not possible, however, to pick an oxygenation breakpoint below which the benefits of mechanical ventilation decidedly outweigh its hazards. It is futile to imagine that decision making about instituting mechanical ventilation in an individual patient can be condensed into an algorithm with absolute numbers at each nodal point. In sum, an algorithm cannot replace the presence of a physician well skilled in the art of clinical evaluation who has a deep understanding of pathophysiologic principles.

Effect of Atypical Sleep EEG Patterns on Weaning From Prolonged Mechanical Ventilation.

BACKGROUND: Approximately one-third of acute ICU patients display atypical sleep patterns that cannot be interpreted by using standard EEG criteria for sleep. Atypical sleep patterns have been associated with poor weaning outcomes in acute ICUs. RESEARCH QUESTION: Do patients being weaned from prolonged mechanical ventilation experience atypical sleep EEG patterns, and are these patterns linked with weaning outcomes? STUDY DESIGN AND METHODS: EEG power spectral analysis during wakefulness and overnight polysomnogram were performed on alert, nondelirious patients at a long-term acute care facility. RESULTS: Forty-four patients had been ventilated for a median duration of 38 days at the time of the polysomnogram study. Eleven patients (25%) exhibited atypical sleep EEG. During wakefulness, relative EEG power spectral analysis revealed higher relative delta power in patients with atypical sleep than in patients with usual sleep (53% vs 41%; P < .001) and a higher slow-to-fast power ratio during wakefulness: 4.39 vs 2.17 (P < .001). Patients with atypical sleep displayed more subsyndromal delirium (36% vs 6%; P = .027) and less rapid eye movement sleep (4% vs 11% total sleep time; P < .02). Weaning failure was more common in the atypical sleep group than in the usual sleep group: 91% vs 45% (P = .013). INTERPRETATION: This study provides the first evidence that patients in a long-term acute care facility being weaned from prolonged ventilation exhibit atypical sleep EEG patterns that are associated with weaning failure. Patients with atypical sleep EEG patterns had higher rates of subsyndromal delirium and slowing of the wakeful EEG, suggesting that these two findings represent a biological signal for brain dysfunction.

Pearls and pitfalls of respiratory testing in a patient with amyotrophic lateral sclerosis and COPD.

Interpretation of pulmonary function testing in patients with amyotrophic lateral sclerosis must account for coexisting lung diseases, when making patient care decisions. https://bit.ly/3Co2yR0.

Therapy for insomnia with chronic obstructive pulmonary disease: a randomized trial of components.

STUDY OBJECTIVES: To determine efficacy and mechanisms of cognitive behavioral therapy for insomnia (CBT-I) and chronic obstructive pulmonary disease (COPD) education (COPD-ED) on clinical outcomes in adults with concurrent COPD and insomnia. METHODS: We conducted a 2 × 2 factorial study to test the impact of CBT-I and COPD-ED delivered alone or in combination on severity of insomnia and fatigue, sleep, and dyspnea. Participants were randomized to 1 of 4 groups-group 1: CBT-I + attention control (AC; health videos, n = 27); group 2: COPD-ED + AC, n = 28; group 3: CBT-I + COPD-ED, n = 27; and group 4, AC only, n = 27. Participants received six 75-minute weekly sessions. Dependent variables included insomnia severity, sleep by actigraphy, fatigue, and dyspnea measured at baseline, immediately postintervention, and at 3 months postintervention. Presumed mediators of intervention effects included beliefs and attitudes about sleep, self-efficacy for sleep and COPD, and emotional function. RESULTS: COPD patients (percent predicted forced expiratory volume in 1 second [FEV1pp] 67% ± 24% [mean ± standard deviation]), aged 65 ± 8 years, with insomnia participated in the study. Insomnia and sleep improved more in patients who received CBT-I than in those who did not, an effect that was sustained at 3 months postintervention and mediated by beliefs and attitudes about sleep. CBT-I was associated with clinically important improvements in fatigue and dyspnea. When CBT-I and COPD-ED were concurrently administered, effects on insomnia, fatigue, and dyspnea were attenuated. CONCLUSIONS: CBT-I produced significant and sustained decreases in insomnia improved sleep and clinically important improvement in fatigue, and dyspnea. The combination of CBT-I and COPD-ED reduced CBT-I's effectiveness. Further research is needed to understand the mechanisms associated with effects of insomnia therapy on multiple symptoms in COPD. CLINICAL TRIAL REGISTRATION: Registry: ClinicalTrials.gov; Name: A Behavioral Therapy for Insomnia Co-existing with COPD; URL: https://clinicaltrials.gov/ct2/show/NCT01973647; Identifier: NCT01973647. CITATION: Kapella M, Steffen A, Prasad B, et al. Therapy for insomnia with chronic obstructive pulmonary disease: a randomized trial of components. J Clin Sleep Med. 2022;18(12):2763-2774.

Long-Term Acute Care Hospital Outcomes of Mechanically Ventilated Patients With Coronavirus Disease 2019.

OBJECTIVES: To describe the clinical characteristics and outcomes of adult patients with coronavirus disease 2019 requiring weaning from prolonged mechanical ventilation. DESIGN: Observational cohort study of patients admitted to two long-term acute care hospitals from April 1, 2020, to March 31, 2021. SETTING: Two long-term acute care hospitals specialized in weaning from prolonged mechanical ventilation in the Chicagoland area, Illinois, United States. PATIENTS: Adult (≥ 18 yr old) ICU survivors of respiratory failure caused by severe acute respiratory syndrome coronavirus 2 pneumonia receiving prolonged mechanical ventilation. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: During the study period, 158 consecutive patients were transferred to the long-term acute care hospitals for weaning from prolonged ventilation. Demographic, clinical, and laboratory data were collected and analyzed. Final date of follow-up was June 1, 2021. Prior to long-term acute care hospital transfer, median length of stay at the acute care hospital was 41.0 days and median number of ventilator days was 35. Median age was 60.0 years, 34.8% of patients were women, 91.8% had a least one comorbidity, most commonly hypertension (65.8%) and diabetes (53.2%). The percentage of weaning success was 70.9%. The median duration of successful weaning was 8 days. Mortality was 9.6%. As of June 1, 2021, 19.0% of patients had been discharged home, 70.3% had been discharged to other facilities, and 1.3% were still in the long-term acute care hospitals. CONCLUSIONS: Most patients with coronavirus disease 2019 transferred to two Chicago-area long-term acute care hospitals successfully weaned from prolonged mechanical ventilation.

A Case Report of Cystic Fibrosis Plus Tuberous Sclerosis: A Cautionary Tale Regarding Lung Transplantation.

BACKGROUND: Cystic fibrosis (CF) and tuberous sclerosis complex (TSC) are 2 rare genetic diseases that often affect the lungs. Pulmonary compromise in TSC or CF can be severe enough to require lung transplantation. In rare instances patients with CF undergo pneumonectomy to control recurrent lung infections and lung necrosis affecting one lung more than the other. Lung transplantation in these patients is exceedingly rare because preexistent pneumonectomy increases the risk of lung transplant-associated morbidity and mortality. CASE PRESENTATION: We present the case of a young woman with co-occurrence of TSC and CF, who underwent left-sided pneumonectomy and, approximately 2 years later, right-sided single lung transplant. The posttransplant clinical course was complicated by phrenic nerve injury, ventilator dependency, Aspergillus endocarditis with embolic shower, and death. Pretransplant pneumonectomy, Aspergillus colonization, and posttransplant phrenic nerve injury contributed to the complex postoperative course, ventilatory dependence, and poor outcome. CONCLUSION: This cautionary case should alert physicians on the challenges associated with single lung transplant in patients with preexistent pneumonectomy.

Ultrasound and non-ultrasound imaging techniques in the assessment of diaphragmatic dysfunction.

Diaphragm muscle dysfunction is increasingly recognized as an important element of several diseases including neuromuscular disease, chronic obstructive pulmonary disease and diaphragm dysfunction in critically ill patients. Functional evaluation of the diaphragm is challenging. Use of volitional maneuvers to test the diaphragm can be limited by patient effort. Non-volitional tests such as those using neuromuscular stimulation are technically complex, since the muscle itself is relatively inaccessible. As such, there is a growing interest in using imaging techniques to characterize diaphragm muscle dysfunction. Selecting the appropriate imaging technique for a given clinical scenario is a critical step in the evaluation of patients suspected of having diaphragm dysfunction. In this review, we aim to present a detailed analysis of evidence for the use of ultrasound and non-ultrasound imaging techniques in the assessment of diaphragm dysfunction. We highlight the utility of the qualitative information gathered by ultrasound imaging as a means to assess integrity, excursion, thickness, and thickening of the diaphragm. In contrast, quantitative ultrasound analysis of the diaphragm is marred by inherent limitations of this technique, and we provide a detailed examination of these limitations. We evaluate non-ultrasound imaging modalities that apply static techniques (chest radiograph, computerized tomography and magnetic resonance imaging), used to assess muscle position, shape and dimension. We also evaluate non-ultrasound imaging modalities that apply dynamic imaging (fluoroscopy and dynamic magnetic resonance imaging) to assess diaphragm motion. Finally, we critically review the application of each of these techniques in the clinical setting when diaphragm dysfunction is suspected.

Measuring vital capacity in amyotrophic lateral sclerosis: Effects of interfaces and reproducibility.

BACKGROUND: Deterioration of vital capacity (VC) in amyotrophic lateral sclerosis (ALS) signifies disease progression and indicates need for non-invasive ventilation. Weak facial muscles consequent to ALS, with resulting poor mouth seal, may interfere with the accuracy of VC measurements. OBJECTIVES: To determine whether different interfaces affect VC measurements in ALS patients and whether the interface yielding the largest VC produces an even higher VC when re-measured after one week (learning effect). To explore the relationship between optimal interface VC and sniff nasal pressure (SNIP), a measurement of global inspiratory muscle strength. METHODS: Thirty-five patients (17 bulbar and 18 spinal ALS) were studied. Three interfaces (rigid-cylindrical, flanged, oronasal mask) were tested. One week after the first visit, VC was recorded using the optimal interface. SNIP recordings were also obtained. RESULTS: In the bulbar ALS group, median (interquartile range) VC with the flanged mouthpiece was 8.4% (3.9-15.5) larger than with the cylindrical mouthpiece (p < 0.001). VC values with oronasal mask were intermediate to VC with the other two interfaces. In spinal ALS, flanged mouthpiece VC was 4.6% (2.3-7.5) larger than with oronasal mask (p < 0.0006). The latter was 4.5% (0.6-5.2) smaller than with the cylindrical mouthpiece (p = 0.002). In both groups, VC during the second visit was greater than during the first visit (p < 0.025). SNIPs were logarithmically related to VC values recorded with the flanged mouthpiece. CONCLUSION: A flanged mouthpiece yields the largest values of VC in patients with bulbar and spinal ALS.

How to ventilate obstructive and asthmatic patients.

Exacerbations are part of the natural history of chronic obstructive pulmonary disease and asthma. Severe exacerbations can cause acute respiratory failure, which may ultimately require mechanical ventilation. This review summarizes practical ventilator strategies for the management of patients with obstructive airway disease. Such strategies include non-invasive mechanical ventilation to prevent intubation, invasive mechanical ventilation, from the time of intubation to weaning, and strategies intended to prevent post-extubation acute respiratory failure. The role of tracheostomy, the long-term prognosis, and potential future adjunctive strategies are also discussed. Finally, the physiological background that underlies these strategies is detailed.

Misconceptions of pathophysiology of happy hypoxemia and implications for management of COVID-19.

In the article "The pathophysiology of 'happy' hypoxemia in COVID-19," Dhont et al. (Respir Res 21:198, 2020) discuss pathophysiological mechanisms that may be responsible for the absence of dyspnea in patients with COVID-19 who exhibit severe hypoxemia. The authors review well-known mechanisms that contribute to development of hypoxemia in patients with pneumonia, but are less clear as to why patients should be free of respiratory discomfort despite arterial oxygen levels commonly regarded as life threatening. The authors propose a number of therapeutic measures for patients with COVID-19 and happy hypoxemia; we believe readers should be alerted to problems with the authors' interpretations and recommendations.