Mecánica Tusígena / Cough Mechanics

El control neurológico de la tos o la neurofisiología de la tos, implica una serie de eventos complejos en el sistema nervioso que coordinan y desencadenan este reflejo protector pulmonar. Esta intrincada red de señales nerviosas y coordinación muscular se origina en los receptores de la tos, pasa por el centro de la tos en el bulbo raquídeo y finalmente activa los músculos necesarios para la adecuada eliminación del agente irritante. Este mecanismo involucra, la detección del estímulo por receptores especializados, transducción de señales que viajan a lo largo de fibras nerviosas aferentes hacia el sistema nervioso central, centro integrador a nivel del bulbo raquídeo, en el centro de la tos es donde se procesa las señales de los receptores y se coordina la respuesta. La integración de las señales y la respuesta radica en este centro de la tos y en la corteza cerebral quien regula y modula la tos. El control neuronal cortical de la tos implica la participación consciente y voluntaria de la corteza cerebral en la percepción, regulación y adaptación de la tos. La coordinación muscular requiere que la señal viaje por vías nerviosas eferentes motoras hacia los músculos involucrados, la contracción muscular se integra en una secuencia específica que desencadena las fases de la tos, inspiración máxima, compresión y expulsiva.

The neurological control of cough, or the neurophysiology of cough, involves a series of complex events in the nervous system that coordinate and trigger this lung protective reflex. This intricate network of nerve signals and muscle coordination originates from the cough receptors, passes through the cough center in the medulla oblongata, and finally activates the muscles necessary for proper elimination of the irritant. This mechanism involves the detection of the stimulus by specialized receptors, transduction of signals that travel along afferent nerve fibers towards the central nervous system, integrating center at the level of the medulla oblongata, in the cough center is where the signals are processed. receptors and the response is coordinated. The integration of signals and response resides in this cough center and in the cerebral cortex, which regulates and modulates coughing. Cortical neural control of cough involves the conscious and voluntary participation of the cerebral cortex in the perception, regulation, and adaptation of cough. Muscle coordination requires that the signal travel through efferent motor nerve pathways to the muscles involved; muscle contraction is integrated into a specific sequence that triggers the cough, maximum inspiration, compression, and expulsive phases.

Characterization of muscle mass, strength and mobility of critically ill patients with SARS-CoV-2 pneumonia: Distribution by sex, age, days on mechanical ventilation, and muscle weakness.

Objective: Quantify and categorize by sex, age, and time spent on mechanical ventilation (MV), the decline in skeletal muscle mass, strength and mobility in critically ill patients infected with SARS-CoV-2 and requiring mechanical ventilation while at intensive care unit (ICU). Design: Prospective observational study including participants recruited between June 2020 and February 2021 at Hospital Clínico Herminda Martin (HCHM), Chillán, Chile. The thickness of the quadriceps muscle was evaluated by ultrasonography (US) at intensive care unit admission and awakening. Muscle strength and mobility were assessed, respectively, through the Medical Research Council Sum Score (MRC-SS) and the Functional Status Score for the Intensive Care Unit Scale (FSS-ICU) both at awakening and at ICU discharge. Results were categorized by sex (female or male), age (<60 years old or ≥60 years old) and time spent on MV (≤10 days or >10 days). Setting: Intensive care unit in a public hospital. Participants: 132 participants aged 18 years old or above (women n = 49, 60 ± 13 years; men n = 85, 59 ± 12 years) admitted to intensive care unit with a confirmed diagnosis of severe SARS-CoV-2 and requiring MV for more than 48 h were included in the study. Patients with previous physical and or cognitive disorders were excluded. Interventions: Not applicable. Results: Muscle thickness have significantly decreased during intensive care unit stay, vastus intermedius (-11%; p = 0.025), rectus femoris (-20%; p < 0.001) and total quadriceps (-16%; p < 0.001). Muscle strength and mobility were improved at intensive care unit discharge when compared with measurements at awakening in intensive care unit (time effect, p < 0.001). Patients ≥60 years old or on MV for >10 days presented greater muscle loss, alongside with lower muscle strength and mobility. Conclusion: Critically ill patients infected with SARS-CoV-2 and requiring MV presented decreased muscle mass, strength, and mobility during their intensive care unit stay. Factors associated with muscle mass, such as age >60 years and >10 days of MV, exacerbated the critical condition and impaired recovery.

Evaluating a Muscle Ultrasound Education Program: Theoretical Knowledge, Hands-on Skills, Reliability, and Satisfaction of Critical Care Physiotherapists.

OBJECTIVE: To evaluate learning results of critical care physiotherapists participating in a muscle ultrasound (MUS) educational program. DESIGN: Cross-sectional study. SETTING: A custom-made 20-hour MUS course was performed over a 2-week time period, including knobs familiarization, patient positioning, anatomic landmarks, image acquisition, and limb muscle measurements. PARTICIPANTS: Nineteen critical care physiotherapists with little to no prior experience in ultrasound (N=19). INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: Theoretical knowledge, hands-on skills acquisition, and satisfaction were assessed. Inter- and intrarater reliability on landmarks, thickness, and pennation angle of quadriceps between participants was evaluated using intraclass correlation coefficients (ICCs). Reliability among instructors measured prior to the course was also reported as a reference. RESULTS: The percentage score (mean±SD) of knowledge questionnaires was 69±11 (pre-course), 89±10 (post-course), and 92±9 (hands-on skills). Course satisfaction scores ranged from 90%-100%. Pooled interrater reliability of participants (median ICC [interquartile range]) was good (0.70 [0.59-0.79]) for thickness, moderate (0.47 [0.46-0.92]) for landmarks, and absent (0.00 [0.00-0.05]) for pennation angle and the intrarater reliability was good (0.76 [0.51-0.91]) for thickness and weak (0.35 [0.29-0.52]) for pennation angle. Interrater ICC values for instructors were excellent (0.90) for thickness, good (0.67) for landmarks, and moderate (0.41) for pennation angle and intrarater ICC values were excellent (0.94) for thickness and good (0.75) for pennation angle. CONCLUSIONS: Although our sample was quite small and homogeneous, increased theoretical knowledge, high hands-on performance acquisition, and good satisfaction of physiotherapists were observed. Reliability was moderate to excellent for thickness and landmarks and absent to weak for pennation angle. Landmarking and pennation angle remain challenges for physiotherapist training in the application of MUS. Further studies are needed to identify variables that could modify reliability during MUS training.