Nasal inspiratory pressure: an alternative for the assessment of inspiratory muscle strength?

Optimization of sniff nasal inspiratory pressure (SNIP) measurement methodology in healthy subjects

BACKGROUND

Maximal inspiratory pressure (MIP) is currently the most commonly used measure for respiratory muscle strength (RMS) estimation, however, requires significant effort. Falsely low values are therefore common, especially in fatigue-prone subjects, such as neuromuscular disorder patients. In contrast, sniff nasal inspiratory pressure (SNIP) requires a short, sharp sniff; this is a natural manoeuvre, decreasing required effort. Consequently, it has been suggested that use of SNIP could confirm the accuracy of MIP measurements. However, no recent guidelines regarding the optimal method of SNIP measurement exist, and varied approaches have been described.

OBJECTIVES

We compared SNIP values from three conditions, namely with 30, 60 or 90 s time intervals between repeats, the right (SNIP_R) and left (SNIP_L) nostril, and the contralateral nostril occluded (SNIP_O) or non-occluded (SNIP_NO). Additionally, we determined the optimal number of repeats for accurate SNIP measurement.

METHOD

52 healthy subjects (23 males) were recruited for this study, of which a subset of 10 subjects (5 males) completed tests comparing the time interval between repeats. SNIP was measured from functional residual capacity via a probe in one nostril, while MIP was measured from residual volume.

RESULTS

There was no significant difference in SNIP depending on the interval between repeats (P = 0.98); subjects preferred the 30 s. SNIP_O was significantly higher than SNIP_NO (P < 0.00001) but SNIP_L and SNIP_R did not significantly differ (P =  0.60). There was an initial learning effect for the first SNIP test; SNIP did not decline during 80 repeats (P =  0.64).

CONCLUSIONS

We conclude that SNIP_O is a more reliable RMS indicator than SNIP_NO, as there is reduced risk of RMS underestimation. Allowing subjects to choose which nostril to use is appropriate, as this did not significantly affect SNIP, but may increase ease of performance. We suggest that twenty repeats is sufficient to overcome any learning effect and that fatigue is unlikely after this number of repeats. We believe these results are important in aiding the accurate collection of SNIP reference value data in the healthy population.

¿La función muscular inspiratoria podría ser un equivalente de la insuflación pulmonar en los pacientes con EPOC?

Introduction

Chronic obstructive pulmonary disease (COPD) is the respiratory disease that causes the greatest morbidity and mortality worldwide. Lung function parameters and systemic manifestations have been defined as prognostic factors; however, they have limitations. The aim of this study was to analyze whether inspiratory muscle strength could reflect lung hyperinflation, and therefore serve as a prognostic factor in COPD patients.

Method

We selected COPD patients who had performed a non-invasive respiratory muscle strength assessment and lung function testing between January 2015 and October 2017. Mortality was subsequently followed up until March 1, 2020.

Results

We included 140 COPD patients (GOLD stage I 5%, II 73.4%, and III 21.6%), of whom 10% died during follow-up. Bronchial obstruction, defined by FEV₁, was a good predictor of mortality (p = 0.004). Lung hyperinflation, defined as inspiratory capacity (IC)/total lung capacity less than 25 and IC less than 65% of predicted increased mortality in COPD patients (p = 0.001 and p = 0.06, respectively). In this cohort, inspiratory muscle strength, measured by SNIP, was not a prognostic factor (p = 0.629).

Conclusion

In COPD patients, lung hyperinflation is a prognostic factor, but inspiratory muscle function is not. Inspiratory muscle function in COPD patients depends not only on lung mechanics but also on intrinsic muscle factors.

Nutritional status and muscle dysfunction in chronic respiratory diseases: stable phase versus acute exacerbations

Nutritional abnormalities are frequent in different chronic respiratory diseases such as chronic obstructive pulmonary disease (COPD), bronchiectasis, cystic fibrosis (CF), interstitial fibrosis and lung cancer, having important clinical consequences. However, nutritional abnormalities often remained underdiagnosed due to the relative lack of awareness of health professionals. Therefore, systematic anthropometry or even better, assessment of body composition, should be performed in all patients with chronic respiratory conditions, especially following exacerbation periods when malnutrition becomes more accentuated. Nutritional abnormalities very often include the loss of muscle mass, which is an important factor for the occurrence of muscle dysfunction. The latter can be easily detected with the specific assessment of muscle strength and endurance, and also negatively influences patients' quality of life and prognosis. Both nutritional abnormalities and muscle dysfunction result from the interaction of several factors, including tobacco smoking, low physical activity-sedentarism, systemic inflammation and the imbalance between energy supply and requirements, which essentially lead to a negative balance between protein breakdown and synthesis. Therapeutic approaches include improvements in lifestyle, nutritional supplementation and training. Anabolic drugs may be administered in some cases.

Optimal method for assessment of respiratory muscle strength in neuromuscular disorders using sniff nasal inspiratory pressure (SNIP)

Background

The ability to accurately determine respiratory muscle strength is vitally important in patients with neuromuscular disorders (NMD). Sniff nasal inspiratory pressure (SNIP), a test of inspiratory muscle strength, is easier to perform for many NMD patients than the more commonly used determination of maximum inspiratory pressure measured at the mouth (MIP). However, due to an inconsistent approach in the literature, the optimal technique to perform the SNIP maneuver is unclear. Therefore, we systematically evaluated the impact of performing the maneuver with nostril contralateral to the pressure-sensing probe open (SNIP_OP) versus closed (SNIP_CL), on determination of inspiratory muscle strength in NMD patients as well as control subjects with normal respiratory muscle function.

Methods

NMD patients (n = 52) and control subjects without respiratory dysfunction (n = 52) were studied. SNIP_OP, SNIP_CL, and MIP were measured during the same session and compared using ANOVA. Agreement and bias were assessed with intraclass correlation coefficients (ICC) and Bland-Altman plots.

Results

Mean MIP values were 58.2 and 94.0 cmH2O in NMD and control subjects, respectively (p<0.001). SNIP_CL was greater than SNIP_OP in NMD (51.9 ±31.0 vs. 36.9 ±25.4 cmH₂O; p<0.001) as well as in controls (89.2 ±28.1 vs. 69.2 ±29.2 cmH₂O; p<0.001). In both populations, the ICC between MIP and SNIP_CL (NMD = 0.78, controls = 0.35) was higher than for MIP and SNIP_OP (NMD = 0.53, controls = 0.06). In addition, SNIP_CL was more often able to exclude inspiratory muscle weakness than SNIP_OP.

Conclusions

SNIP_CL values are systematically higher than SNIP_OP in both normal subjects and NMD patients. Therefore, SNIP_CL is a useful complementary test for ruling out inspiratory muscle weakness in individuals with low MIP values.

Clinical management of chronic obstructive pulmonary disease patients with muscle dysfunction

Muscle dysfunction is frequently observed in chronic obstructive pulmonary disease (COPD) patients, contributing to their exercise limitation and a worsening prognosis. The main factor leading to limb muscle dysfunction is deconditioning, whereas respiratory muscle dysfunction is mostly the result of pulmonary hyperinflation. However, both limb and respiratory muscles are also influenced by other negative factors, including smoking, systemic inflammation, nutritional abnormalities, exacerbations and some drugs. Limb muscle weakness is generally diagnosed through voluntary isometric maneuvers such as handgrip or quadriceps muscle contraction (dynamometry); while respiratory muscle loss of strength is usually recognized through a decrease in maximal static pressures measured at the mouth. Both types of measurements have validated reference values. Respiratory muscle strength can also be evaluated determining esophageal, gastric and transdiaphragmatic maximal pressures although there is a lack of widely accepted reference equations. Non-volitional maneuvers, obtained through electrical or magnetic stimulation, can be employed in patients unable to cooperate. Muscle endurance can also be assessed, generally using repeated submaximal maneuvers until exhaustion, but no validated reference values are available yet. The treatment of muscle dysfunction is multidimensional and includes improvement in lifestyle habits (smoking abstinence, healthy diet and a good level of physical activity, preferably outside), nutritional measures (diet supplements and occasionally, anabolic drugs), and different modalities of general and muscle training.

Molecular and biological pathways of skeletal muscle dysfunction in chronic obstructive pulmonary disease

Chronic obstructive pulmonary disease (COPD) will be a major leading cause of death worldwide in the near future. Weakness and atrophy of the quadriceps are associated with a significantly poorer prognosis and increased mortality in COPD. Despite that skeletal muscle dysfunction may affect both respiratory and limb muscle groups in COPD, the latter are frequently more severely affected. Therefore, muscle dysfunction in COPD is a common systemic manifestation that should be evaluated on routine basis in clinical settings. In the present review, several aspects of COPD muscle dysfunction are being reviewed, with special emphasis on the underlying biological mechanisms. Figures on the prevalence of COPD muscle dysfunction and the most relevant etiologic contributors are also provided. Despite that ongoing research will shed light into the contribution of additional mechanisms to COPD muscle dysfunction, current knowledge points toward the involvement of a wide spectrum of cellular and molecular events that are differentially expressed in respiratory and limb muscles. Such mechanisms are thoroughly described in the article. The contribution of epigenetic events on COPD muscle dysfunction is also reviewed. We conclude that in view of the latest discoveries, from now, on new avenues of research should be designed to specifically target cellular mechanisms and pathways that impair muscle mass and function in COPD using pharmacological strategies and/or exercise training modalities.

Relationship between sniff nasal inspiratory pressure and BODE index in patients with COPD

PURPOSE

The aims of this study were to investigate the relationship between sniff nasal inspiratory pressure (SNIP) and severity of chronic obstructive pulmonary disease (COPD) as defined by the BODE index, and to investigate the capacity of different SNIP cutoffs to predict a BODE index score ≥5 (i.e., worse disease severity).

METHODS

Thirty-eight subjects with COPD (21 men, 66 ± 8 years, forced expiratory volume in the first second (FEV(1)) 42 ± 16 % predicted) underwent assessments of SNIP, airflow limitation, body mass index (BMI), dyspnea (Medical Research Council scale), and exercise capacity (6-min walking test, 6MWT). The BODE index was calculated, and patients were separated into two groups according to the BODE quartiles (1 and 2, or 3 and 4).

RESULTS

Patients from quartiles 3 and 4 presented lower values of SNIP than patients from quartiles 1 and 2 (73 ± 18 vs 56 ± 21 cmH(2)O, respectively; p = 0.01). There was significant and inverse correlation between SNIP and the BODE index (r = -0.62; p<0.001). A logistic regression model revealed that a SNIP value below 63 cmH(2)O presented higher sensitivity and specificity (70 and 67 %, respectively) for predicting a BODE score equivalent to quartiles 3 or 4.

CONCLUSION

SNIP is moderately and significantly related to COPD severity as assessed by the BODE index. Moreover, the cutoff point of 63 cmH2O showed the best combination of sensitivity and specificity for predicting worse scores in the BODE index.