Long-term outcomes after critical illness: recent insights

Incidence and Risk Factors of Worsened Activities of Daily Living Status Three Months after Intensive Care Unit Discharge among Critically Ill Patients: A Prospective Cohort Study

Background: We aimed to determine risk factors associated with worsened activity of daily living (ADL) status three months after intensive care unit (ICU) discharge. Methods: In this prospective, observational study, we enrolled critically ill adult patients that were emergently admitted to an ICU. We assessed ADL status by Barthel index score prior to ICU admission and three months after ICU discharge. The primary outcome was worsened ADL status, defined as a ≥10 decrease in Barthel index score. Results: We enrolled 102 patients (median age was 72 years old, 55% were male, and 87% received mechanical ventilation during ICU stay), and 42 patients (41%) had worsened ADL status three months after discharge from ICU. Multivariate analysis revealed that older age (>70 years old; adjusted odds ratio (aOR) 3.68; 95% confidence interval (95%CI) 1.33−10.19), high burden of chronic illness (aOR 4.11; 95%CI 1.43−11.81), and longer duration of mechanical ventilation (≥4 days; aOR 2.83; 95%CI 1.04−7.69) were independent risk factors for worsened ADL status at three months. Conclusions: Almost half of the critically ill adult patients in this cohort had worsened ADL status after ICU discharge. Older age, high burden of chronic illness, and longer duration of mechanical ventilation were risk factors for worsened ADL status.

Post-intensive care screening: French translation and validation of the Healthy Aging Brain Care-Monitor, hybrid version

Background

The Healthy Aging Brain Care-Monitor (HABC-M) questionnaires (self-reported version and caregiver version) have been validated for post-intensive care syndrome (PICS) detection in patients surviving a stay in the intensive care unit (ICU). Their authors have also developed a hybrid version (HABC-M-HV) suited to the daily needs of their post-ICU follow-up clinic. The objectives of the present cross-sectional observational study were to translate the HABC-M-HV questionnaire into French (HABC-M-HV-F) according to international guidelines and to test its measurement properties.

Methods

The HABC-M-HV was translated according to international guidelines. The measurement performances of the questionnaire were tested using internal consistency, test–retest reliability, Standard Error of Measurement (SEM) and Smallest Detectable Change (SDC) calculation, floor and ceiling effect measurement and construct validity.

Results

The validation study included 51 ICU survivors (27.5% women, 63 [55–71] years old). The questionnaire was administered by phone. The internal consistency was very good (Cronbach’s alpha coefficient 0.79). The intra- and inter-examinator reliabilities were excellent (Intraclass Coefficient Correlation = 0.99 and 0.97, respectively). The SEM was 0.62 and the SDC was 1.72. No floor or ceiling effects were observed. The convergent validity was almost entirely confirmed with 71.4% of our hypothesis confirmed.

Conclusion

The HABC-M-HV-F has been shown to be a valid and reliable tool for PICS screening and follow-up in French-speaking ICU survivors. A remote administration by phone was feasible.

Trial registration: Not applicable.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12955-022-01967-1.

A Neurobiological Framework for the Therapeutic Potential of Music and Sound Interventions for Post-Traumatic Stress Symptoms in Critical Illness Survivors

Overview: Post traumatic stress disorder (PTSD) has emerged as a severely debilitating psychiatric disorder associated with critical illness. Little progress has been made in the treatment of post-intensive care unit (ICU) PTSD. Aim: To synthesize neurobiological evidence on the pathophysiology of PTSD and the brain areas involved, and to highlight the potential of music to treat post-ICU PTSD. Methods: Critical narrative review to elucidate an evidence-based neurobiological framework to inform the study of music interventions for PTSD post-ICU. Literature searches were performed in PubMed and CINAHL. The Scale for the Assessment of Narrative Review Articles (SANRA) guided reporting. Results: A dysfunctional HPA axis feedback loop, an increased amygdalic response, hippocampal atrophy, and a hypoactive prefrontal cortex contribute to PTSD symptoms. Playing or listening to music can stimulate neurogenesis and neuroplasticity, enhance brain recovery, and normalize stress response. Additionally, evidence supports effectiveness of music to improve coping and emotional regulation, decrease dissociation symptoms, reduce depression and anxiety levels, and overall reduce severity of PTSD symptoms. Conclusions: Despite the lack of music interventions for ICU survivors, music has the potential to help people suffering from PTSD by decreasing amygdala activity, improving hippocampal and prefrontal brain function, and balancing the HPA-axis.

Understanding Patients' Perceived Health After Critical Illness: Analysis of Two Prospective, Longitudinal Studies of ARDS Survivors

BACKGROUND

Perceived health is one of the strongest determinants of subjective well-being, but it has received little attention among survivors of ARDS.

RESEARCH QUESTION

How well do self-reported measures of physical, emotional, and social functioning predict perceived overall health (measured using the EQ-5D visual analog scale [EQ-5D-VAS]) among adult survivors of ARDS? Are demographic features, comorbidity, or severity of illness correlated with perceived health after controlling for self-reported functioning?

STUDY DESIGN AND METHODS

We analyzed the ARDSNet Long Term Outcomes Study (ALTOS) and Improving Care of Acute Lung Injury Patients (ICAP) Study, two longitudinal cohorts with a total of 823 survivors from 44 US hospitals, which prospectively assessed survivors at 6 and 12 months after ARDS. Perceived health, evaluated using the EQ-5D-VAS, was predicted using ridge regression and self-reported measures of physical, emotional, and social functioning. The difference between observed and predicted perceived health was termed perspective deviation (PD). Correlations between PD and demographics, comorbidities, and severity of illness were explored.

RESULTS

The correlation between observed and predicted EQ-5D-VAS scores ranged from 0.68 to 0.73 across the two cohorts and time points. PD ranged from -80 to +34 and was more than the minimum clinically important difference for 52% to 55% of survivors. Neither demographic features, comorbidity, nor severity of illness were correlated strongly with PD, with |r| < 0.25 for all continuous variables in both cohorts and time points. The correlation between PD at 6- and 12-month assessments was weak (ALTOS: r = 0.22, P < .001; ICAP: r = 0.20, P = .02).

INTERPRETATION

About half of survivors of ARDS showed clinically important differences in actual perceived health vs predicted perceived health based on self-reported measures of functioning. Survivors of ARDS demographic features, comorbidities, and severity of illness were correlated only weakly with perceived health after controlling for measures of perceived functioning, highlighting the challenge of predicting how individual patients will respond psychologically to new impairments after critical illness.

A Decade of Post-Intensive Care Syndrome: A Bibliometric Network Analysis

Background and Objectives: In 2012, the umbrella term post-intensive care syndrome (PICS) was introduced to capture functional long-term impairments of survivors of critical illness. We present a bibliometric network analysis of the PICS research field. Materials and Methods: The Web of Science core database was searched for articles published in 2012 or later using ‘post-intensive care syndrome’ and variant spellings. Using VOSviewer, we computed co-authorship networks of countries, institutions, and authors, as well as keyword co-occurrence networks. We determined each country’s relative research effort and Category Normalized Citation Index over time and analyzed the 100 most-cited articles with respect to article type, country of origin, and publishing journal. Results: Our search yielded 379 articles, of which 373 were analyzed. Annual PICS research output increased from 11 (2012) to 95 articles (2020). Most PICS research originates from the US, followed by England, Australia, the Netherlands, and Germany. We found various collaborations between countries, institutions, and authors, with recent collaborative networks of English and Australian institutions. Article keywords cover aspects of cognitive, mental health, and physical impairments, and more recently, COVID-19. Only a few keywords and articles pertained to PICS prevention and treatment. Conclusions: Our analysis of Web of Science-indexed PICS articles highlights the stark increase in PICS research output in recent years, primarily originating from US- and Europe-based authors and institutions. Despite the research field’s growth, knowledge gaps with respect to PICS prevention and treatment remain.

Experimental Approach of Quadriceps Strength Measurement: Implications for Assessments in Critically Ill Survivors

(1) Background: The supine testing position is suitable for early quadriceps strength (QS) assessment in intensive care unit, while a seated position is more appropriate for survivors who have regained mobility. Acquiring consistent measurements is essential for longitudinal follow-up. We compared the QS generated in different settings in healthy volunteers. (2) Methods: Isometric QS was assessed using a MicroFet2 and standardised protocols comparing different modalities. Hip and knee flexion angles were, respectively, 45° and 40° (H45-K40) in the supine position, and both at 90° (H90-K90) in the seated position. Dynamometer was either handheld (non-fixed configuration, NFC), or fixed (FC) in a cubicle. (3) Results: QS in H90–K90 and H45-K40 positions were strongly correlated, but QS was higher in the later position regardless of the configuration. Compared to H45-K40, biases of 108.2N (or 28.05%) and 110.3N (27.13%) were observed in H90-K90 position, respectively, in the NFC and FC. These biases were independently and positively associated with QS (p < 0.001). For both position, there were no significant differences between QS measured in NFC or FC. (4) Conclusions: The quadriceps was less efficient in the seated position, compared to the supine position, in healthy volunteers. These findings have practical implications for further assessments and research in critically ill patients.

COVID-19 pandemic: the impact on Canada’s intensive care units

The COVID-19 pandemic has exposed the precarious demand-capacity balance in Canadian hospitals, including critical care where there is an urgent need for trained health care professionals to dramatically increase ICU capacity.

The impact of the pandemic on ICUs varied significantly across the country with provinces that implemented public health measures later and relaxed them sooner being impacted more severely. Pediatric ICUs routinely admitted adult patients. Non-ICU areas were converted to ICUs and staff were redeployed from other essential service areas. Faced with a lack of critical care capacity, triage plans for ICU admission were developed and nearly implemented in some provinces.

Twenty eight percent of patients in Canadian ICUs who required mechanical ventilation died. Surviving patients have required prolonged ICU admission, hospitalization and extensive ongoing rehabilitation. Family members of patients were not permitted to visit, resulting in additional psychological stresses to patients, families, and healthcare teams. ICU professionals also experienced extreme psychological stresses from caring for such large numbers of critically ill patients, often in sub-standard conditions. This resulted in large numbers of health workers leaving their professions.

This pandemic is not yet over, and it is likely that new pandemics will follow. A review and recommendations for the future are provided.

Implementation of post-intensive care outpatient clinic (I-POINT) for critically ill COVID-19 survivors

Although we have enough and cumulative information about acute effects of COVID-19, our knowledge is extremely limited about long-term consequences of COVID-19, in terms of its impacts and burdens on patients, families, and the health system. Considering the underlying pathophysiological mechanisms affecting all of the organ systems in critically ill COVID-19 patients who are admitted to intensive care units, the development of post-intensive care syndrome is inevitable. This situation brings along the development of long-COVID. These patients should be followed regarding cognitive, physical, and psychiatric aspects and necessary specialist referrals should be carried out. In this article, we are presenting the experience and recommendations of our center, as a guide for the establishment process of post-intensive care outpatient clinics for the critically ill patients who required intensive care admission due to COVID-19 and could be discharged.

Persisting neuroendocrine abnormalities and their association with physical impairment 5 years after critical illness

Background

Critical illness is hallmarked by neuroendocrine alterations throughout ICU stay. We investigated whether the neuroendocrine axes recover after ICU discharge and whether any residual abnormalities associate with physical functional impairments assessed 5 years after critical illness.

Methods

In this preplanned secondary analysis of the EPaNIC randomized controlled trial, we compared serum concentrations of hormones and binding proteins of the thyroid axis, the somatotropic axis and the adrenal axis in 436 adult patients who participated in the prospective 5-year clinical follow-up and who provided a blood sample with those in 50 demographically matched controls. We investigated independent associations between any long-term hormonal abnormalities and physical functional impairments (handgrip strength, 6-min walk distance, and physical health-related quality-of-life) with use of multivariable linear regression analyses.

Results

At 5-year follow-up, patients and controls had comparable serum concentrations of thyroid-stimulating hormone, thyroxine (T₄), triiodothyronine (T₃) and thyroxine-binding globulin, whereas patients had higher reverse T₃ (rT₃, p = 0.0002) and lower T₃/rT₃ (p = 0.0012) than controls. Patients had comparable concentrations of growth hormone, insulin-like growth factor-I (IGF-I) and IGF-binding protein 1 (IGFBP1), but higher IGFBP3 (p = 0.030) than controls. Total and free cortisol, cortisol-binding globulin and albumin concentrations were comparable for patients and controls. A lower T₃/rT₃ was independently associated with lower handgrip strength and shorter 6-min walk distance (p ≤ 0.036), and a higher IGFBP3 was independently associated with higher handgrip strength (p = 0.031).

Conclusions

Five years after ICU admission, most hormones and binding proteins of the thyroid, somatotropic and adrenal axes had recovered. The residual long-term abnormality within the thyroid axis was identified as risk factor for long-term physical impairment, whereas that within the somatotropic axis may be a compensatory protective response. Whether targeting of the residual abnormality in the thyroid axis may improve long-term physical outcome of the patients remains to be investigated.

Trial registration ClinicalTrials.gov: NCT00512122, registered on July 31, 2007 (https://www.clinicaltrials.gov/ct2/show/NCT00512122).

Graphical Abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s13054-021-03858-1.

Physical capacities assessment in critically ill patients: An exploratory study

BACKGROUND

The severity of muscle weakness after critical illness is very heterogeneous. To identify those patients who may maximally benefit from early exercises would be highly valuable. This implies an assessment of physical capacities, comprised at least of strength measurement and functional tests.

OBJECTIVES

The objective of this study was to investigate the relationship between muscle strength and functional tests in an intensive care unit (ICU) setting.

METHODS

Adults with ICU length of stay ≥2 days were included. Handgrip strength (HG) and maximal isometric quadriceps strength (QS) were assessed using standardised protocols as soon as patients were alert and able to obey commands. At the same time, their maximal level of mobilisation capabilities and their autonomy were assessed using ICU Mobility Scale (ICU-MS) and Barthel Index, respectively.

RESULTS

Ninety-three patients with a median age of 64 [57-71.5] years, body mass index of 26.4 [23.4-29.6] kg/m², and Simplified Acute Physiology Score II of 33 [27.7-41] were included. Absolute and relative QS were, respectively, 146.7 [108.5-196.6] N and 1.87 [1.43-2.51] N/kg. HG was 22 [16-31] kg. The ICU-MS score was 4 [1-5]. A significant positive correlation was observed between HG and absolute QS (r_s = 0.695, p < 0.001) and between HG and relative QS (r_s = 0.428, p < 0.001). The ICU-MS score correlated with HG, with a weak positive relationship (r_s = 0.215, p = 0.039), but not with QS. The ICU-MS score did not statistically differ between the weakest and strongest patients for absolute or relative QS, but was lower in patients with the lowest HG values (p = 0.01). A weak positive correlation was observed between the Barthel Index and muscle strengths (maximum r_s = 0.414, p < 0.001).

CONCLUSIONS

The present results suggest that, during ICU stay, there is no strong association between muscle strength and functional test such as the ICU-MS or Barthel Index. Muscle dynamometry and functional tests are probably complementary tools for physical capacities quantification.

Using smartwatches to observe changes in activity during recovery from critical illness following COVID-19: a 1 year multi-centre observational study. (Preprint)

Background

As a sequela of the COVID-19 pandemic, a large cohort of critical illness survivors have had to recover in the context of ongoing societal restrictions.

Objective

We aimed to use smartwatches (Fitbit Charge 3; Fitbit LLC) to assess changes in the step counts and heart rates of critical care survivors following hospital admission with COVID-19, use these devices within a remote multidisciplinary team (MDT) setting to support patient recovery, and report on our experiences with this.

Methods

We conducted a prospective, multicenter observational trial in 8 UK critical care units. A total of 50 participants with moderate or severe lung injury resulting from confirmed COVID-19 were recruited at discharge from critical care and given a smartwatch (Fitbit Charge 3) between April and June 2020. The data collected included step counts and daily resting heart rates. A subgroup of the overall cohort at one site—the MDT site (n=19)—had their smartwatch data used to inform a regular MDT meeting. A patient feedback questionnaire and direct feedback from the MDT were used to report our experience. Participants who did not upload smartwatch data were excluded from analysis.

Results

Of the 50 participants recruited, 35 (70%) used and uploaded data from their smartwatch during the 1-year period. At the MDT site, 74% (14/19) of smartwatch users uploaded smartwatch data, whereas 68% (21/31) of smartwatch users at the control sites uploaded smartwatch data. For the overall cohort, we recorded an increase in mean step count from 4359 (SD 3488) steps per day in the first month following discharge to 7914 (SD 4146) steps per day at 1 year (P=.003). The mean resting heart rate decreased from 79 (SD 7) beats per minute in the first month to 69 (SD 4) beats per minute at 1 year following discharge (P<.001). The MDT subgroup’s mean step count increased more than that of the control group (176% increase vs 42% increase, respectively; +5474 steps vs +2181 steps, respectively; P=.04) over 1 year. Further, 71% (10/14) of smartwatch users at the MDT site and 48% (10/21) of those at the control sites strongly agreed that their Fitbit motivated them to recover, and 86% (12/14) and 48% (10/21), respectively, strongly agreed that they aimed to increase their activity levels over time.

Conclusions

This is the first study to use smartwatch data to report on the 1-year recovery of patients who survived a COVID-19 critical illness. This is also the first study to report on smartwatch use within a post–critical care MDT. Future work could explore the role of smartwatches as part of a randomized controlled trial to assess clinical and economic effectiveness.

International Registered Report Identifier (IRRID)

RR2-10.12968/ijtr.2020.0102

Long-term complications of COVID-19 in ICU survivors: what do we know?

Coronavirus disease 2019 (COVID-19) has caused more than 175 million persons infected and 3.8 million deaths so far and is having a devastating impact on both low and high-income countries, in particular on hospitals and intensive care units (ICU). The ICU mortality during the first pandemic wave ranged from 40% to 85% during the busiest ICU period for admissions around the peak of the surge, and those surviving are frequently faced with impairments affecting physical, cognitive, and mental health status, complicating the post-acute phase of COVID-19, which in the pre-COVID period, were defined collectively as post-intensive care syndrome (PICS). Long COVID is defined as four weeks of persisting symptoms after the acute illness, and post-COVID syndrome and chronic COVID-19 are the proposed terms to describe continued symptomatology for more than 12 weeks. Overall, 50% of ICU survivors suffer from new physical, mental, and/or cognitive problems at 1 year after ICU discharge. The prevalence, severity, and duration of the various impairments in ICU survivors are poorly defined, with substantial variations among published series, and may reflect differences in the timing of assessment, the outcome measured, the instruments utilized, and thresholds adopted to establish the diagnosis, the qualification of personnel delivering the tests, the resource availability as well diversity in patients' case-mix. Future longitudinal studies of adequate sample size with repeated assessments of validated outcomes and comparison with non-COVID-19 ICU patients are needed to fully explore the long-term outcome of ICU patients with COVID-19. In this article, we focus on chronic COVID-19 in ICU survivors and present state of the art data regarding long-term complications related to critical illness and the treatments and organ support received.

Quality of Heart Failure Care in the Intensive Care Unit

Patients with heart failure (HF) who are seen in an intensive care unit (ICU) manifest the highest-risk, most complex and most resource-intensive disease states. These patients account for a large relative proportion of days spent in an ICU. The paradigms by which critical care is provided to patients with HF are being reconsidered, including consideration of various multidisciplinary ICU staffing models and the development of acute-response teams. Traditional HF quality initiatives have centered on the peri- and postdischarge period in attempts to improve adherence to guideline-directed therapies and reduce readmissions. There is a compelling rationale for expanding high-quality efforts in treating patients with HF who are receiving critical care so we can improve outcomes, reduce preventable harm, improve teamwork and resource use, and achieve high health-system performance. Our goal is to answer the following question: For a patient with HF in the ICU, what is required for the provision of high-quality care? Herein, we first review the epidemiology of HF syndromes in the ICU and identify relevant critical care and quality stakeholders in HF. We next discuss the tenets of high-quality care for patients with HF in the ICU that will optimize critical care outcomes, such as ICU staffing models and evidence-based management of cardiac and noncardiac disease. We discuss strategies to mitigate preventable harm, improve ICU culture and conduct outcomes review, and we conclude with our summative vision of high-quality of ICU care for patients with HF; our vision includes clinical excellence, teamwork and ICU culture.

What intensive care registries can teach us about outcomes

PURPOSE OF REVIEW

Critical care registries are synonymous with measurement of outcomes following critical illness. Their ability to provide longitudinal data to enable benchmarking of outcomes for comparison within units over time, and between units, both regionally and nationally is a key part of the evaluation of quality of care and ICU performance as well as a better understanding of case-mix. This review aims to summarize literature on outcome measures currently being reported in registries internationally, describe the current strengths and challenges with interpreting existing outcomes and highlight areas where registries may help improve implementation and interpretation of both existing and new outcome measures.

RECENT FINDINGS

Outcomes being widely reported through ICU registries include measures of survival, events of interest, patient-reported outcomes and measures of resource utilization (including cost). Despite its increasing adoption, challenges with quality of reporting of outcomes measures remain. Measures of short-term survival are feasible but those requiring longer follow-ups are increasingly difficult to interpret given the evolving nature of critical care in the context of acute and chronic disease management. Furthermore, heterogeneity in patient populations and in healthcare organisations in different settings makes use of outcome measures for international benchmarking at best complex, requiring substantial advances in their definitions and implementation to support those seeking to improve patient care.

SUMMARY

Digital registries could help overcome some of the current challenges with implementing and interpreting ICU outcome data through standardization of reporting and harmonization of data. In addition, ICU registries could be instrumental in enabling data for feedback as part of improvement in both patient-centred outcomes and in service outcomes; notably resource utilization and efficiency.

Post-intensive care syndrome after a critical COVID-19: cohort study from a Belgian follow-up clinic

Purpose

Many patients with coronavirus disease 2019 (COVID-19) required critical care. Mid-term outcomes of the survivors need to be assessed. The objective of this single-center cohort study was to describe their physical, cognitive, psychological, and biological outcomes at 3 months following intensive care unit (ICU)-discharge (M3).

Patients and methods

All COVID-19 adults who survived an ICU stay ≥ 7 days and attended the M3 consultation at our multidisciplinary follow-up clinic were involved. They benefited from a standardized assessment, addressing health-related quality of life (EQ-5D-3L), sleep disorders (PSQI), and the three principal components of post-intensive care syndrome (PICS): physical status (Barthel index, handgrip and quadriceps strength), mental health disorders (HADS and IES-R), and cognitive impairment (MoCA). Biological parameters referred to C-reactive protein and creatinine.

Results

Among the 92 patients admitted to our ICU for COVID-19, 42 survived a prolonged ICU stay and 32 (80%) attended the M3 follow-up visit. Their median age was 62 [49–68] years, 72% were male, and nearly half received inpatient rehabilitation following ICU discharge. At M3, 87.5% (28/32) had not regained their baseline level of daily activities. Only 6.2% (2/32) fully recovered, and had normal scores for the three MoCA, IES-R and Barthel scores. The main observed disorders were PSQI > 5 (75%, 24/32), MoCA < 26 (44%, 14/32), Barthel < 100 (31%, 10/32) and IES-R ≥ 33 (28%, 9/32). Combined disorders were observed in 13/32 (40.6%) of the patients. The EQ-5D-3L visual scale was rated at 71 [61–80]. A quarter of patients (8/32) demonstrated a persistent inflammation based on CRP blood level (9.3 [6.8–17.7] mg/L).

Conclusion

The burden of severe COVID-19 and prolonged ICU stay was considerable in the present cohort after 3 months, affecting both functional status and biological parameters. These data are an argument on the need for closed follow-up for critically ill COVID-19 survivors.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13613-021-00910-9.

Cardiopulmonary Exercise Testing in Critically Ill Coronavirus Disease 2019 Survivors: Evidence of a Sustained Exercise Intolerance and Hypermetabolism

Supplemental Digital Content is available in the text.

OBJECTIVES:

To investigate exercise capacity at 3 and 6 months after a prolonged ICU stay.

DESIGN:

Observational monocentric study.

SETTING:

A post-ICU follow-up clinic in a tertiary university hospital in Liège, Belgium.

PATIENTS:

Patients surviving an ICU stay greater than or equal to 7 days for a severe coronavirus disease 2019 pneumonia and attending our post-ICU follow-up clinic.

MEASUREMENTS AND MAIN RESULTS:

Cardiopulmonary and metabolic variables provided by a cardiopulmonary exercise testing on a cycle ergometer were collected at rest, at peak exercise, and during recovery. Fourteen patients (10 males, 59 yr [52–62 yr], all obese with body mass index > 27 kg/m²) were included after a hospital stay of 40 days (35–53 d). At rest, respiratory quotient was abnormally high at both 3 and 6 months (0.9 [0.83–0.96] and 0.94 [0.86–0.97], respectively). Oxygen uptake was also abnormally increased at 3 months (8.24 mL/min/kg [5.38–10.54 mL/min/kg]) but significantly decreased at 6 months (p = 0.013). At 3 months, at the maximum workload (67% [55–89%] of predicted workload), oxygen uptake peaked at 81% (64–104%) of predicted maximum oxygen uptake, with oxygen pulse and heart rate reaching respectively 110% (76–140%) and 71% (64–81%) of predicted maximum values. Ventilatory equivalent for carbon dioxide remains within normal ranges. The 50% decrease in oxygen uptake after maximum effort was delayed, at 130 seconds (115–142 s). Recovery was incomplete with a persistent anaerobic metabolism. At 6 months, no significant improvement was observed, excepting an increase in heart rate reaching 79% (72–95%) (p = 0.008).

CONCLUSIONS:

Prolonged reduced exercise capacity was observed up to 6 months in critically ill coronavirus disease 2019 survivors. This disability did not result from residual pulmonary or cardiac dysfunction but rather from a metabolic disorder characterized by a sustained hypermetabolism and an impaired oxygen utilization.