The effect of inspiratory muscle fatigue on breathing pattern and ventilatory response to CO2.

Abstract

SUMMARY1. The effects of inducing inspiratory muscle fatigue on the subsequent breathing pattern were examined during resting unstimulated breathing and during CO2 rebreathing. In addition, we examined whether induction of inspiratory muscle fatigue alters CO2 responsiveness.2. Global inspiratory muscle fatigue and diaphragmatic fatigue were achieved by having subjects breathe against an inspiratory resistive load while generating a predetermined fraction of either their maximal mouth pressure or maximal transdiaphragmatic pressure until they were unable to generate the target pressure.3. Induction of inspiratory muscle fatigue had no effect on the subsequent breathing pattern during either unstimulated breathing or during CO2 rebreathing.4. Following induction of inspiratory muscle fatigue, the slope of the ventilatory response to CO2 was significantly decreased from 18-8 + 33 during control to 13-8+221 1 min-(% end-tidal CO2 concentration)-with fatigue (P < 002).

Avaliação da aplicação do índice de tobin no desmame da ventilação mecânica após anestesia geral

“…Enquanto na prática médica a maioria dos pacientes submetidos a operações sob anestesia geral balanceada é facilmente extubada, parcela deles permanece em desmame ventilatório prolongado 20,21 . Nenhum dos critérios atuais de extubação é considerado preditor absoluto e, sim, diretrizes para a extubação segura, alertando para a probabilidade de sucesso ou fracasso no desmame ventilatório [22][23][24] 6 proposed a practical, effective, and non-invasive method to obtain the predictive index of success or failure of discontinuing mechanical ventilation.…”

“…Good reproducibility of classical weaning parameters with similar bedside techniques was demonstrated, especially when indexes that estimate the ventilatory pattern using V T and respiratory rate, such as the Tobin index, which is deemed to be the most accurate to predict the prognosis of wean [11][12][13] , were evaluated. Although the accuracy of this index is better than the other extubation tests frequently used [14][15][16][17][18][19] , 20% of false positive results were observed, i.e., the relationship f/V T predicted a successful extubation but the patient could not maintain adequate ventilatory autonomy and had to be re-intubated, or presented clinical complications related with the extubation process [20][21][22][23][24] . The objective of this study was to evaluate the use of the Tobin index with values between 80 and 100 c.L -1 .min -1 or lower than 80 c.L -1 .min -1 before extubation in patients undergoing general anesthesia.…”

“…While in the medical practice most patients undergoing surgeries under balanced general anesthesia are easily extubated, some of the patients remain in prolonged respiratory wean 20,21 . None of the current extubation criteria is considered an absolute predictor, but directives for safe extubation, indicating the probability of success or failure [22][23][24] .…”

“…Demonstrou-se boa reprodutibilidade de parâmetros clás-sicos de desmame realizados com técnicas corretas à beira do leito, sobretudo quando foram avaliados os índices que estimam o padrão ventilatório com o VCE e a freqüência respiratória, como o índice de Tobin, apontado como um dos parâmetros com maior acurácia em predizer o prognóstico do desmame ventilatório [11][12][13] . Embora a precisão desse ín-dice seja melhor do que os demais testes de extubação mais utilizados [14][15][16][17][18][19] foram observados 20% de resultados falsos-positivos, isto é, a relação f/VCE prediz sucesso na extubação, porém o paciente não consegue manter autonomia ventilatória adequada, necessitando de reintubação, ou, então, apresenta complicações clínicas relacionadas com o processo de extubação [20][21][22][23][24] . O objetivo deste estudo foi avaliar a aplicação do índice de Tobin com valores entre 80 e 100 c.L -1 .min -1 ou menores que 80 c.L -1 .min -1 antes da extubação traqueal em pacientes submetidos a anestesia geral.…”

Direct and indirect measurements relevant to the assessment of fatigue of the respiratory muscles - review

“…The application of this test indicates that although rapid shallow breathing may accompany respiratory muscle fatigue [31][32][33][34][35], it cannot be considered a specific marker of fatigue and tidal volume and breathing frequency should not be used as specific indicators of the development of this complex phenomenon.…”