Tags

Type your tag names separated by a space and hit enter

Tension-time index of inspiratory muscles in COPD patients: role of airway obstruction.
Respir Med. 1998 Jun; 92(6):828-35.RM

Abstract

Inspiratory muscle function has been shown to be related to general muscle weakness, weight loss, blood gas tensions, airway obstruction and hyperinflation. The aim of this study was to define (1) the factor that is the main determinant of the tension-time index of the inspiratory muscles (TTmus), and which this increases the risk of inspiratory muscle fatigue; and (2) whether a breathing strategy is adopted to avoid inspiratory muscle fatigue. Twenty-seven normal volunteers and 35 stable COPD outpatients (FEV1% predicted, range: 21-89%; and FRC/TLC, range: 49-77%) were studied. The TTmus was determined as follows: TTmus = PI/PImax.TI/Ttot, where Pi is the mean inspiratory pressure calculated from the mouth occlusion pressure (P0.1), PImax is the maximal inspiratory pressure, TI is the inspiratory time, and Ttot is the total time of the breathing cycle. COPD patients showed significantly lower PImax and higher P0.1, PI, PI/PImax, and TTmus than normal subjects. No patient had a TTmus value higher than the inspiratory muscle fatigue threshold of 0.33. The FEV1 was significantly correlated with TTmus and all its components in the patients. The FRC/TLC was also correlated with all components except PI. Body weight was only correlated with PImax. In a forward and backward stepwise regression analysis, FEV1 appeared to be the only significant factor explaining the variance of log (PI/PImax) and log (TTmus), whereas FRC/TLC was the principal determinant of PImax. In COPD patients, a non-linear relationship was found between TI and P0.1. A negative linear relationship was found between TI/Ttot and PI/PImax. In conclusion, although hyperinflation predominantly affected inspiratory muscle strength in a group of stable COPD patients with a wide range of severity, airway obstruction was the principal factor determining the magnitude of TTmus. In addition, in order to remain below the inspiratory muscle fatigue threshold, as the severity of airway obstruction increased, patients adopted a breathing strategy characterized by decreased TI/Ttot as inspiratory pressure demand increased.

Authors+Show Affiliations

Laboratoire de Physiologie des Interactions, Centre Hospitalier Universitaire Arnaud de Villeneuve, Montpellier, France.No affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info available

Pub Type(s)

Journal Article

Language

eng

PubMed ID

9850366

Citation

Hayot, M, et al. "Tension-time Index of Inspiratory Muscles in COPD Patients: Role of Airway Obstruction." Respiratory Medicine, vol. 92, no. 6, 1998, pp. 828-35.
Hayot M, Perrigault PF, Gautier-Dechaud V, et al. Tension-time index of inspiratory muscles in COPD patients: role of airway obstruction. Respir Med. 1998;92(6):828-35.
Hayot, M., Perrigault, P. F., Gautier-Dechaud, V., Capdevila, X., Milic-Emili, J., Prefaut, C., & Ramonatxo, M. (1998). Tension-time index of inspiratory muscles in COPD patients: role of airway obstruction. Respiratory Medicine, 92(6), 828-35.
Hayot M, et al. Tension-time Index of Inspiratory Muscles in COPD Patients: Role of Airway Obstruction. Respir Med. 1998;92(6):828-35. PubMed PMID: 9850366.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Tension-time index of inspiratory muscles in COPD patients: role of airway obstruction. AU - Hayot,M, AU - Perrigault,P F, AU - Gautier-Dechaud,V, AU - Capdevila,X, AU - Milic-Emili,J, AU - Prefaut,C, AU - Ramonatxo,M, PY - 1998/12/16/pubmed PY - 1998/12/16/medline PY - 1998/12/16/entrez SP - 828 EP - 35 JF - Respiratory medicine JO - Respir Med VL - 92 IS - 6 N2 - Inspiratory muscle function has been shown to be related to general muscle weakness, weight loss, blood gas tensions, airway obstruction and hyperinflation. The aim of this study was to define (1) the factor that is the main determinant of the tension-time index of the inspiratory muscles (TTmus), and which this increases the risk of inspiratory muscle fatigue; and (2) whether a breathing strategy is adopted to avoid inspiratory muscle fatigue. Twenty-seven normal volunteers and 35 stable COPD outpatients (FEV1% predicted, range: 21-89%; and FRC/TLC, range: 49-77%) were studied. The TTmus was determined as follows: TTmus = PI/PImax.TI/Ttot, where Pi is the mean inspiratory pressure calculated from the mouth occlusion pressure (P0.1), PImax is the maximal inspiratory pressure, TI is the inspiratory time, and Ttot is the total time of the breathing cycle. COPD patients showed significantly lower PImax and higher P0.1, PI, PI/PImax, and TTmus than normal subjects. No patient had a TTmus value higher than the inspiratory muscle fatigue threshold of 0.33. The FEV1 was significantly correlated with TTmus and all its components in the patients. The FRC/TLC was also correlated with all components except PI. Body weight was only correlated with PImax. In a forward and backward stepwise regression analysis, FEV1 appeared to be the only significant factor explaining the variance of log (PI/PImax) and log (TTmus), whereas FRC/TLC was the principal determinant of PImax. In COPD patients, a non-linear relationship was found between TI and P0.1. A negative linear relationship was found between TI/Ttot and PI/PImax. In conclusion, although hyperinflation predominantly affected inspiratory muscle strength in a group of stable COPD patients with a wide range of severity, airway obstruction was the principal factor determining the magnitude of TTmus. In addition, in order to remain below the inspiratory muscle fatigue threshold, as the severity of airway obstruction increased, patients adopted a breathing strategy characterized by decreased TI/Ttot as inspiratory pressure demand increased. SN - 0954-6111 UR - https://www.unboundmedicine.com/medline/citation/9850366/Tension_time_index_of_inspiratory_muscles_in_COPD_patients:_role_of_airway_obstruction_ L2 - https://linkinghub.elsevier.com/retrieve/pii/S0954-6111(98)90384-5 DB - PRIME DP - Unbound Medicine ER -