Noninvasive Measurement of the Maximum Relaxation Rate of Inspiratory Muscles in Patients with Neuromuscular Disorders

Abstract

Background: Slowing of inspiratory muscle relaxation has been used as an index for inspiratory muscle fatigue. However, maximum relaxation rate measured from oesophageal pressure traces after maximum sniff (P_oes MRR) has limited clinical usefulness because it requires an oesophageal balloon catheter system. Objectives: It was the aim of this study to establish whether, in neuromuscular patients, maximum relaxation rate assessed from sniff nasal pressure (P_nasal MRR) reflects oesophageal MRR and the tension-time index of the diaphragm (TT_di). Methods: Twenty patients with neuromuscular disease and 10 healthy subjects were studied. P_oes and transdiaphragmatic pressure were measured while P_nasal was recorded with a balloon advanced through the nose into the nasopharynx. Maximum P_oes, transdiaphragmatic pressure and P_nasal were simultaneously measured while the patients performed maximal sniffs. The MRR (% pressure fall/10 ms) for each sniff, the TT_di and the tension-time index of respiratory muscles were determined. Results: Neuromuscular patients showed higher TT_di, lower P_oes MRR and lower P_nasal MRR than the control group. In patients with neuromuscular disease, the correlation coefficient of P_nasal MRR and P_oes MRR was 0.985 (p < 0.001). Regression analysis showed that P_oes MRR = –1.101 + 1.113·P_nasal MRR (r² = 0.929, standard error of the estimate = 0.208). Indeed, P_nasal MRR was negatively correlated with TT_di (r = –0.914, p < 0.001) and the tension-time index of respiratory muscles (r = –0.732, p < 0.001). In the neuromuscular group, the mean difference between P_nasal MRR and P_oes MRR was 0.286 ± 0.217%/10 ms. Conclusions: P_nasal MRR obtained from a maximal sniff accurately reflects P_oes MRR and TT_di in patients with neuromuscular disorders.

Multiparametric analysis of sniff nasal inspiratory pressure test in middle stage amyotrophic lateral sclerosis

“…In our study, all parameters derived from the SNIP curve were significantly different between middle stage ALS and healthy subjects, being in agreement with two previous studies performed in subjects with neuromuscular disorders (47,49). Evangelista et al (49), observed that a reduced MRR was reliable in identifying the delayed relaxation of the respiratory muscles in myotonic dystrophy type 1 patients when compared to healthy controls; while Garcia-Rio et al (47), despite heterogeneity of the study population, found that the decreased MRR of neuromuscular disease patients was accompanied by the deterioration in the functional reserve of the diaphragm as well as of the inspiratory muscles. The rationale for measuring relaxation rates from pressure curves is based on the assumption that the decay portion of the curve, when expiration is totally passive, corresponds to the relaxation phase of inspiratory muscle contraction (18).…”

“…According to Kyroussis et al (22), measurements of relaxation rates obtained from nasal sniffs accurately reflects those from esophageal pressure curves and can be used as an index of the onset and recovery of respiratory muscle fatigue. Moreover, measurements of nasal sniffs are simple, tolerated, and minimally invasive and can provide a quantitative response index to fatigue and therapeutic interventions in neuromuscular disease patients (47,48). In our study, all parameters derived from the SNIP curve were significantly different between middle stage ALS and healthy subjects, being in agreement with two previous studies performed in subjects with neuromuscular disorders (47,49).…”

Effects of diaphragmatic control on the assessment of sniff nasal inspiratory pressure and maximum relaxation rate

“…The diaphragm is one of the main inspiratory muscles active during this maneuver, which raises the question of whether to emphasize its action when measuring SNIP. Although the SNIP test is noninvasive, research indicates a high correlation (r=0.99, p<0.001) between this maneuver and invasive techniques measuring esophageal pressure with an esophageal balloon catheter 11 - 13 . In addition to assessing muscular strength, SNIP has been used as a predictor of respiratory muscle fatigue by analyzing the Maximum Relaxation Rate (MRR) of inspiratory muscles, calculated based on test kinetics 13 .…”

“…Although the SNIP test is noninvasive, research indicates a high correlation (r=0.99, p<0.001) between this maneuver and invasive techniques measuring esophageal pressure with an esophageal balloon catheter 11 - 13 . In addition to assessing muscular strength, SNIP has been used as a predictor of respiratory muscle fatigue by analyzing the Maximum Relaxation Rate (MRR) of inspiratory muscles, calculated based on test kinetics 13 . Previous studies evaluated the MRR in healthy subjects and patients with neuromuscular disorders and chronic obstructive pulmonary disease (COPD) 11 - 13 .…”

Sniff Nasal Inspiratory Pressure in Healthy Japanese Subjects: Mean Values and Lower Limits of Normal

“…Sniff nasal inspiratory pressure (SNIP) is also used to assess respiratory muscle strength [5]. In fact, it has been reported that sniffing is strongly related to the activity and strength of the diaphragm [6, 7], and SNIP can be used to assess inspiratory muscle strength or fatigue in patients with neuromuscular or skeletal disease [8, 9]. In patients with amyotrophic lateral sclerosis in whom it is impossible to measure VC or PImax, it is possible to measure SNIP [10], which has a high sensitivity to predict ventilatory failure [11].…”