Current definitions of the breathing cycle in alveolar breath-by-breath gas exchange analysis.

Identification of the breathing cycle forms the basis of any breath-by-breath gas exchange analysis. Classically, the breathing cycle is defined as the time interval between the beginning of two consecutive inspiration phases. Based on this definition, several research groups have developed algorithms designed to estimate the volume and rate of gas transferred across the alveolar membrane ("alveolar gas exchange"); however, most algorithms require measurement of lung volume at the beginning of the ith breath (VLi-1; i.e., the end-expiratory lung volume of the preceding ith breath). The main limitation of these algorithms is that direct measurement of VLi-1 is challenging and often unavailable. Two solutions avoid the requirement to measure VLi-1 by redefining the breathing cycle. One method defines the breathing cycle as the time between two equal fractional concentrations of lung expired oxygen (Fo2) (or carbon dioxide; Fco2), typically in the alveolar phase, whereas the other uses the time between equal values of the Fo2/Fn2 (or Fco2/Fn2) ratios [i.e., the ratio of fractional concentrations of lung expired O2 (or CO2) and nitrogen (N2)]. Thus, these methods identify the breathing cycle by analyzing the gas fraction traces rather than the gas flow signal. In this review, we define the traditional approach and two alternative definitions of the human breathing cycle and present the rationale for redefining this term. We also explore the strengths and limitations of the available approaches and provide implications for future studies.

Assessing Cognitive-Motor Interference in Military Contexts: Validity and Reliability of Two Dual-tasking Tests.

INTRODUCTION: Cognitive-motor interference is the decrease in cognitive performance and/or physical performance occurring when a cognitive task and a physical task are performed concurrently (dual task) compared to when they are performed in isolation (single task). The aim of this study was to investigate the construct validity and test-retest reliability of two cognitive-motor interference tests in military contexts. MATERIALS AND METHODS: Twenty-two soldiers, officers, and cadets performed a 10-min loaded marching, a 10-min Psychomotor Vigilance Task, and the two tasks combined (visit 1). During visit 2, a 5-min running time trial, a 5-min Word Recall Task, and the two tasks combined. These tests were repeated by 20 participants after 2 weeks (visits 3 and 4). RESULTS: Significant impairments were shown on both running distance (P < .001) and number of words recalled (P = .004) in the dual-task condition compared to the single-task condition. Significantly shorter step length (P < .001) and higher step frequency (P < .001) were found during the loaded marching in the dual-task condition compared to the single-task condition. No significant differences were observed in mean reaction time (P = .402) and number of lapses (P = .479) during the Psychomotor Vigilance Task. Good-to-excellent reliability was found for all the cognitive and physical variables in both single- and dual-task conditions, except for the number of lapses. CONCLUSION: These findings suggest that the Running + Word Recall Task test is a valid and reliable dual-tasking test that could be used to assess cognitive-motor interference in military contexts.

Risk factors for intubation in severe bronchiolitis: a useful tool to decide on an early intensive respiratory support.

BACKGROUND: Bronchiolitis is the most frequent lower airway infection leading hospitalization in children younger than 2 years. RSV is the typical common cause, followed by rhinovirus. Criteria for Pediatric Intensive Care Unit (PICU) admission are not defined by guidelines. METHODS: A retrospective analysis of children with severe bronchiolitis admitted from 2013 to 2016 to our PICU was performed to identify the risk factors associated with intubation in this population. Fourteen variables were studied: sex, weight, age, nationality, provenience, duration of symptoms, risk factors for bronchiolitis development, recurrence, apnea, SpO2 in air, Modified Wood's Clinical Asthma score (M-WCAS), microbiological results, medical treatment, CPAP therapy. The relationship between these variables and the need for mechanical ventilation were explored using univariate and multivariate logistic regression analysis. A ROC analysis was used to identify cut-off for the continuous variables identified as risk factors for intubation in multivariate analysis. RESULTS: We enrolled 93 patients: 19 of them (20.4%) were intubated. Univariate and multivariate analysis demonstrated that a M-WCAS Score ≥7, SpO2 ≤75% and apnea were significantly associated to intubation in children with severe bronchiolitis. CONCLUSIONS: Cut-off values of the variables identified as risk factors for intubation may represent an important tool for pediatricians to decide a prompt and appropriate intensive respiratory support.

COVID-19 disease in professional football players: symptoms and impact on pulmonary function and metabolic power during matches.

This study aimed at: (1) Reporting COVID-19 symptoms and duration in professional football players; (2) comparing players' pulmonary function before and after COVID-19; (3) comparing players' metabolic power (Pmet ) before and after COVID-19. Thirteen male players (Age: 23.9 ± 4.0 years, V̇O2peak : 49.7 ± 4.0 mL/kg/min) underwent a medical screening and performed a running incremental step test and a spirometry test after COVID-19. Spirometric data were compared with the ones collected at the beginning of the same season. Players' mean Pmet of the 10 matches played before COVID-19 was compared with mean Pmet of the 10 matches played after COVID-19. Players completed a questionnaire on COVID-19 symptoms and duration 6 months following the disease. COVID-19 positivity lasted on average 15 ± 5 days. "General fatigue" and "muscle fatigue" symptoms were reported by all players during COVID-19 and persisted for 77% (general fatigue) and 54% (muscle fatigue) of the players for 37 ± 28 and 38 ± 29 days after the disease, respectively. No significant changes in spirometric measurements were found after COVID-19, even though some impairments at the individual level were observed. Conversely, a linear mixed-effects model analysis showed a significant reduction of Pmet (-4.1 ± 3.5%) following COVID-19 (t = -2.686, p < 0.05). "General fatigue" and "muscle fatigue" symptoms may persist for several weeks following COVID-19 in professional football players and should be considered for a safer return to sport. Players' capacity to compete at high intensities might be compromised after COVID-19.

Sleep Deprivation Training to Reduce the Negative Effects of Sleep Loss on Endurance Performance: A Single Case Study.

PURPOSE: Sleep deprivation (SD) is very common during ultraendurance competitions. At present, stimulants such as caffeine and naps are the main strategies used to reduce the negative effects of SD on ultraendurance performance. In this case study, the authors describe the application of a novel strategy consisting of the intermittent repetition of SD (SD training [SDT]) during the weeks preceding an ultraendurance competition. METHODS: A male ultraendurance runner underwent a 6-week SDT program (consisting of 1 night SD every Sunday) in addition to his regular physical training program before taking part in a 6-day race. Before and after SDT, the participant performed 5 consecutive days of daily 2-hour constant-pace running with SD on the first and third night. Psychological and physiological responses were measured during this multiday test. RESULTS: SDT was well tolerated by the athlete. A visual analysis of the data suggests that including SDT in the weeks preceding an ultraendurance competition may have beneficial effects on sleepiness and perceived mental effort in the context of 5 consecutive days of prolonged running and 2 nights of SD. This multiday test seems a feasible way for assessing ultraendurance athletes in the laboratory. CONCLUSIONS: The results provided some encouraging initial information about SDT that needs to be confirmed in a randomized controlled trial in a group of ultraendurance athletes. If confirmed to be effective and well tolerated, SDT might be used in the future to help ultraendurance athletes and other populations that have to perform in conditions of SD.

The effects of sinusoidal linear drifts on the estimation of cardiorespiratory dynamic parameters during sinusoidal workload forcing: a simulation study.

This study aimed at investigating whether: 1) different sinusoidal linear drifts would affect the estimation of the dynamic parameters amplitude (A) and phase lag (φ) of minute ventilation (V˙E), oxygen uptake, carbon dioxide production and heart rate (HR) sinusoidal responses when the frequency analysis technique (F) is performed; 2) the Marquardt-Levenberg non-linear fitting technique (ML) would provide more precise estimations of A and φ of drifted sinusoidal responses compared to F. For each cardiorespiratory variable, fifteen responses to sinusoidal forcing of different sinusoidal periods were simulated by using a first-order dynamic linear model. A wide range of linear drifts were subsequently applied. A and φ were computed for all drifted and non-drifted responses by using both F (AF and φF) and ML (AML and φML). For non-drifted responses, no differences between AF vs AML and φF vs φML were found. Whereas AF and φF were affected by the sinusoidal linear drifts, AML and φML were not. Significant interaction effects (technique x drift) were found for A (P <  0.001; ƞP2 > 0.247) and φ (P <  0.001; ƞP2 > 0.851). Higher goodness of fit values were observed when using ML for drifted V˙E and HR responses only. The present findings suggest ML as a recommended technique to use when sinusoidal linear drifts occur during sinusoidal exercise, and provide new insights on how to analyse drifted cardiorespiratory sinusoidal responses.

Preliminary report on left-ventricular assist devices: are patients' and caregivers' psychosocial needs adequately addressed?.

OBJECTIVES: Patients implanted with a Left Ventricular Assist Device (LVAD) constitute a new population of chronic heart failure (HF) patients requiring continuous medical support and representing heavy costs - both direct and indirect - for the healthcare system. If there is consensus about the increased survival, the psychosocial outcomes, in terms of psychological wellbeing, behavioral and social functioning of both patients and caregivers, are still unclear. Overall, it is not clear if local health and social services are equipped to support them in their needs. We conducted an observational study on the psychosocial characteristics and needs of LVAD patients. METHODS: Twenty-seven patients admitted for rehabilitation after implantation, and their caregivers were recruited. On admission, patients and caregivers were administered questionnaires assessing anxiety, depression, quality of life, level of social complexity and were interviewed about their social resources. At discharge, patients were re-assessed by questionnaires and patients/caregivers received a follow-up phone-interview after 8-12 months. RESULTS: LVAD patients' emotional well-being and subjective quality of life improved during the rehabilitation stay and they confirmed their satisfaction with LVAD at follow-up. Problems emerged concerning the inadequate health and social assistance that LVAD patients receive once home. More than 50% of patients showed substantial social complexity, the burden of which fell on the caregivers, whose strain hardly declined over time, remaining at a level requiring psychological attention. CONCLUSIONS: Technological advances that improve LVAD patients' survival should be rapidly followed by adequate interventions by policy makers to improve also the local health/social assistance provided and to address patients and caregivers psychosocial needs over time.

Caudal 0.2% ropivacaine is less effective during surgery than 0.2% levobupivacaine and 0.2% bupivacaine: a double-blind, randomized, controlled trial.

BACKGROUND: We hypothesized that without the analgesic effects of volatile anesthetics, caudal 0.20% ropivacaine would be less effective during surgical stimulation than 0.20% bupivacaine or 0.20% levobupivacaine. This trial was designed to examine whether the combination of a caudal block with 0.20% ropivacaine and i.v. anesthesia resulted in reduced analgesic efficacy during surgery compared with caudal 0.20% levobupivacaine or 0.20% bupivacaine in children. METHODS: Ninety ASA I-II children between 1 and 7 years old, scheduled for inguinal hernia repair or orchidopexy under propofol anesthesia were randomized to receive a caudal block with 1 ml x kg(-1) of 0.2% bupivacaine, 0.2% ropivacaine or 0.2% levobupivacaine. The primary outcome measure of the study was the clinical efficacy of the caudal block during surgery. Secondary outcome measures were postoperative pain relief and residual motor blockade. RESULTS: Four children were excluded and 86 were analyzed. The proportion of children with effective caudal block during surgery was significantly higher in children receiving levobupivacaine (26/28) or bupivacaine (27/29) compared with patients receiving ropivacaine (21/29) (P = 0.03). There were no significant differences among groups in the analgesic onset time (P = 0.1), incidence of residual motor blockade (P = 0.4), number of patients requiring analgesia after operation or in the time from caudal injection to the first administration of analgesic medication (P = 0.3). CONCLUSIONS: Combined with propofol anesthesia, 0.2% levobupivacaine and 0.2% bupivacaine are more effective than 0.2% ropivacaine for caudal use in children undergoing inguinal hernia repair or orchidopexy.