Objective: To investigate the relationship between respiratory function, functionality, and mortality in amyotrophic lateral sclerosis (ALS) patients and to determine which respiratory parameters show the strongest correlation with functionality and mortality. Methods: The study was conducted in Rio Grande do Norte, Northeast Brazil, between January 2018 and December 2023. This was a retrospective cohort, following individuals with ALS who were evaluated at the University Laboratory. Results: A total of 74 ALS patients were included in the analysis, with a mean age of 55.7 ± 13.5 years. Most were male (66.2%) and predominantly presented with spinal-onset ALS (51.3%). Respiratory variables (except peak expiratory flow (PEF)) showed a weak but significant inverse correlation with mortality (FVC% predicted (r_pb = −0.260; p < 0.001), SNIP (r_pb = −0.235; p = 0.001), MEP (r_pb = −0.207; p = 0.007), MIP (r_pb = −0.198; p = 0.009), and PEF% predicted (r_pb = −0.156; p = 0.013)). When analyzing their correlation with ALSFRS-R, all variables showed a significant positive correlation (ranging from weak to moderate) with functionality. A reduction of one unit in the respiratory variables PEF% of predicted, maximal inspiratory pressure (MIP), and sniff nasal inspiratory pressure (SNIP) increased the risk of death by an average of 300% (OR = 2.99; 95% CI: 2.05–4.35), 2% (OR = 1.02; 95% CI: 1.01–1.03), and 1% (OR = 1.01; 95% CI: 1.00–1.02), respectively. Conclusions: Our findings suggest that direct measurements of respiratory function and muscle strength, particularly PEF and SNIP, may serve as more useful markers to guide early interventions such as non-invasive ventilation, thereby improving quality of life and potentially prolonging survival.

Poorly performed sniff nasal inspiratory pressure (SNIP) test in children could lead to misinterpreting the results. We aim to establish an adequate number of SNIP maneuvers in children. Children aged 6 to 11 years of age and both gender without respiratory disease were included in the study. Spirometry and inspiratory muscle strength were assessed. The sample consisted of 121 healthy children (62 girls), 54% presented BMI bellow 85th percentile and 46% upper 85th percentile. Spirometry data were normal (FVC%: 105 ± 13, FEV1%: 100 ± 11) and mean SNIP was 89.47 ± 20.25 cmH2O. No more than 20% of the sample reached the highest SNIP after the 10th maneuver, with a significant difference (p<0.0001) when comparing the highest value between the first ten maneuvers and the highest one after the 10th maneuver. Stratified by age group, 94% of 6-7 years old reached the highest value in the first ten maneuvers, 79% in the 8-9 year age group and 83% in the 10-11 years old. The ICC between the highest values of SNIP and the first acceptable maneuver was 0.437, 0.641 and 0.409 for children 6-7, 8-9 and 10-11 years of age, respectively. The concordance analysis between these two variables was (lower and upper limits): group of 6-7 years -10.10 and 47.98 cmH2O, group of 8-9 years -8.61 and 44.65 cmH2O and -9.92 and 51.66 cmH2O for the group of 10-11 years. In conclusion, twelve maneuvers SNIP maneuvers is appropriate for children between 6 to11 years.