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

Abstract

OBJECTIVE:To assess the influence of diaphragmatic activation control (diaphC) on Sniff Nasal-Inspiratory Pressure (SNIP) and Maximum Relaxation Rate of inspiratory muscles (MRR) in healthy subjects. METHOD:Twenty subjects (9 male; age: 23 (SD=2.9) years; BMI: 23.8 (SD=3) kg/m2; FEV1/FVC: 0.9 (SD=0.1)] performed 5 sniff maneuvers in two different moments: with or without instruction on diaphC. Before the first maneuver, a brief explanation was given to the subjects on how to perform the sniff test. For sniff test with diaphC, subjects were instructed to perform intense diaphragm activation. The best SNIP and MRR values were used for analysis. MRR was calculated as the ratio of first derivative of pressure over time (dP/dtmax) and were normalized by dividing it by peak pressure (SNIP) from the same maneuver. RESULTS:SNIP values were significantly different in maneuvers with and without diaphC [without diaphC: -100 (SD=27.1) cmH2O/ with diaphC: -72.8 (SD=22.3) cmH2O; p<0.0001], normalized MRR values were not statistically different [without diaphC: -9.7 (SD=2.6); with diaphC: -8.9 (SD=1.5); p=0.19]. Without diaphC, 40% of the sample did not reach the appropriate sniff criteria found in the literature. CONCLUSION:Diaphragmatic control performed during SNIP test influences obtained inspiratory pressure, being lower when diaphC is performed. However, there was no influence on normalized MRR.

Effects of Diaphragmatic Control on Multiparametric Analysis of the Nasal Inspiratory Pressure Test and Inspiratory Muscle Activity in Healthy Subjects

“…diaphragmatic control) during the SNIP test. Similar to our results, the study by Benício et al [9] exposed that performing diaphragmatic control during the sniff maneuver results in lower SNIP value when compared to the maneuver without DiaphC and associated this to the probable difference in muscle recruitment during both maneuvers. These studies are, as far as we know, the only ones that proposed to evaluate the in uence of diaphragmatic control during the SNIP test and our results complement the authors' interpretation.…”

“…This nding supports the hypothesis that when performing ballistic contraction of the diaphragm muscle during a sniff maneuver, the diaphragm performs its action in a more isolated way which means the accessory muscles are less activated and, as a consequence, the SNIP values are lower. This is based on the ndings described by Benício et al [9].…”

“…Benício et al [9] also question the technical characteristics of sniff maneuvers. The authors reported 40% of the maneuvers without DiaphC exceeded the maneuver time recommended in the literature.…”

“…Occasionally the shortage of details to describe clinical tests, such as the SNIP test, can lead to methodological errors and misinterpretation of results. The study carried out by Benício et al [9] is, as far as we know, the only one that proposed to evaluate the in uence of diaphragmatic control (diaphC) during the SNIP test. It reports that diaphC maneuvers generate lower SNIP values, possibly due to a lower recruitment of accessory respiratory muscles, in addition to generating tests with technical standardization.…”

Reference values of sniff nasal inspiratory pressure in healthy children

“…Respiratory muscle weakness is a common clinical finding in neuromuscular diseases, respiratory diseases affecting the parenchyma and airways and skeletal disorders among others, and its assessment is of great importance in adult and pediatric clinical practice . Respiratory muscle strength is estimated through maximal inspiratory pressure (MIP) and maximal expiratory pressure (MEP), respectively measured noninvasively through the mouth through sustained maneuvers for 2 to 3 seconds with airway occlusion . These measurements have a high false‐negative rate since they depend on the patient's cooperation, in which low results may not reflect weakness but insufficient coordination, motivation, and verbal command .…”