Respiratory Drive, Dyspnea, and Silent Hypoxemia: A Physiological Review in the Context of COVID-19

Accuracy of the defining characteristics of respiratory nursing diagnoses in patients with COVID-19

OBJECTIVE

To analyze the accuracy of the defining characteristics of four respiratory nursing diagnoses (ND) in patients with COVID-19 and on oxygen therapy.

METHODS

This is a cross-sectional study conducted in four Brazilian public hospitals in two regions of the country. A total of 474 patients with COVID-19 receiving oxygen therapy were assessed. Latent-adjusted class analysis with random effects was used to establish the sensitivity (Se) and specificity (Sp) of the defining characteristics evaluated for each ND.

RESULTS

Among the ND that constituted the study (impaired spontaneous ventilatory, impaired gas exchange, ineffective airway clearance, and dysfunctional ventilatory weaning response), the following defining characteristics had the highest simultaneous Se and Sp (>0.8): decrease in tidal volume, confusion, irritability, dyspnea, decreased breath sounds, orthopnea, impaired ability to cooperate and respond to coaching, and decrease in the level of consciousness.

CONCLUSIONS

Recognizing the clinical signs that predict respiratory ND in patients affected by COVID-19 can contribute to the nurse's accurate diagnostic inference and designate the appropriate nursing interventions to achieve the desired results and avoid complications.

It's in the blood: a review of the hematological system in SARS-CoV-2-associated COVID-19

The emergence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has led to an unprecedented global healthcare crisis. While SARS-CoV-2-associated COVID-19 affects primarily the respiratory system, patients with COVID-19 frequently develop extrapulmonary manifestations. Notably, changes in the hematological system, including lymphocytopenia, neutrophilia and significant abnormalities of hemostatic markers, were observed early in the pandemic. Hematological manifestations have since been recognized as important parameters in the pathophysiology of SARS-CoV-2 and in the management of patients with COVID-19. In this narrative review, we summarize the state-of-the-art regarding the hematological and hemostatic abnormalities observed in patients with SARS-CoV-2-associated COVID-19, as well as the current understanding of the hematological system in the pathophysiology of acute and chronic SARS-CoV-2-associated COVID-19.

Inspiratory Muscle Training While Hospitalized With Acute COVID-19 Respiratory Failure: A Randomized Controlled Trial

Although inspiratory muscle training (IMT) has been used in outpatient settings for patients who recovered from COVID-19 respiratory failure, little data exist to support earlier implementation in acute care hospitals. This study aimed to assess the safety and feasibility of IMT during the acute disease phase of COVID-19.

Design Setting and Patients

Sixty patients presenting with COVID-19 to a single academic medical center were randomized to control or intervention groups using systematic randomization.

Measurements

Participants in the control group had their maximal inspiratory pressure (MIP) measured at enrollment and hospital discharge. They were also asked for their rating of perceived exertion on the Revised Borg Scale for Grading Severity of Dyspnea and were scored by researchers on the Activity Measure for Post-Acute Care (AM-PAC) 6-Clicks Mobility Scale and the Intensive Care Unit Mobility Scale (IMS). Control group patients otherwise received standard care. Participants in the intervention group, in addition to the measures described previously, received inspiratory threshold trainers with the goal of doing 2 sessions daily with a physical therapist for the duration of their inpatient hospitalization. In these sessions, the patient completed 3 sets of 10 breaths with the trainer. Initial resistance was set at 30% of their MIP, with resistance increasing 1 level for the subsequent session if the patients rated their during-activity rating of perceived exertion as less than 2. Changes in functional outcome measures, amount of supplemental oxygen, hospital length of stay (LOS), discharge location, adverse events, and mortality were assessed in group comparisons.

Results

Of 60 enrolled patients, 41 (n = 19 in intervention and n = 22 in control) were included in the final data set, which required completion of the study, initial and discharge data points collected, and survival of hospitalization. Final groups were statistically similar. A total of 161 sessions of IMT were completed among the 19 patients in the intervention group. Mortality totaled 2 in the control group and 3 in the intervention group and adverse events during intervention occurred in only 3 (1.8%) sessions, all of which were minor oxygen desaturations. Sessions were unable to be completed for all potential reasons 11% of possible times. Dropout rate in the intervention group was 3 (10%). Both intervention and control groups demonstrated improved MIP, decreased supplemental oxygen requirements, improved function on the AM-PAC, and slightly decreased function on the IMS. Length of stay was shorter in the intervention group, and discharge disposition was similar between groups.

Conclusions

With a low number of recorded adverse events, similar mortality between groups, and successful completion of 161 exercise sessions, IMT may be a feasible and safe intervention for some hospitalized patients with COVID-19.

Unraveling the Underlying Molecular Mechanism of 'Silent Hypoxia' in COVID-19 Patients Suggests a Central Role for Angiotensin II Modulation of the AT1R-Hypoxia-Inducible Factor Signaling Pathway

A few days after being infected with SARS-CoV-2, a fraction of people remain asymptomatic but suffer from a decrease in arterial oxygen saturation in the absence of apparent dyspnea. In light of our clinical investigation on the modulation of molecules belonging to the renin angiotensin system (RAS) in COVID-19 patients, we propose a model that explains 'silent hypoxia'. The RAS imbalance caused by SARS-CoV-2 results in an accumulation of angiotensin 2 (Ang II), which activates the angiotensin 2 type 1 receptor (AT1R) and triggers a harmful cascade of intracellular signals leading to the nuclear translocation of the hypoxia-inducible factor (HIF)-1α. HIF-1α transactivates many genes including the angiotensin-converting enzyme 1 (ACE1), while at the same time, ACE2 is downregulated. A growing number of cells is maintained in a hypoxic condition that is self-sustained by the presence of the virus and the ACE1/ACE2 ratio imbalance. This is associated with a progressive worsening of the patient's biological parameters including decreased oxygen saturation, without further clinical manifestations. When too many cells activate the Ang II-AT1R-HIF-1α axis, there is a 'hypoxic spillover', which marks the tipping point between 'silent' and symptomatic hypoxia in the patient. Immediate ventilation is required to prevent the 'hypoxic spillover'.

Silent Hypoxemia in the Emergency Department: A Retrospective Cohort of Two Clinical Phenotypes in Critical COVID-19

Introduction: Understanding hypoxemia, with and without the clinical signs of acute respiratory failure (ARF) in COVID-19, is key for management. Hence, from a population of critical patients admitted to the emergency department (ED), we aimed to study silent hypoxemia (Phenotype I) in comparison to symptomatic hypoxemia with clinical signs of ARF (Phenotype II). Methods: This multicenter study was conducted between 1 March and 30 April 2020. Adult patients who were presented to the EDs of nine Great-Eastern French hospitals for confirmed severe or critical COVID-19, who were then directly admitted to the intensive care unit (ICU), were retrospectively included. Results: A total of 423 critical COVID-19 patients were included, out of whom 56.1% presented symptomatic hypoxemia with clinical signs of ARF, whereas 43.9% presented silent hypoxemia. Patients with clinical phenotype II were primarily intubated, initially, in the ED (46%, p < 0.001), whereas those with silent hypoxemia (56.5%, p < 0.001) were primarily intubated in the ICU. Initial univariate analysis revealed higher ICU mortality (29.2% versus 18.8%, p < 0.014) and in-hospital mortality (32.5% versus 18.8%, p < 0.002) in phenotype II. However, multivariate analysis showed no significant differences between the two phenotypes regarding mortality and hospital or ICU length of stay. Conclusions: Silent hypoxemia is explained by various mechanisms, most physiological and unspecific to COVID-19. Survival was found to be comparable in both phenotypes, with decreased survival in favor of Phenotype II. However, the spectrum of silent to symptomatic hypoxemia appears to include a continuum of disease progression, which can brutally evolve into fatal ARF.