Department of Physical Therapy, University of Miami Miller School of Medicine, Coral Gables, FL, United States; CAPES Foundation, Ministry of Education of Brazil, Brasilia, DF, Brazil.
Pulmonary Section, Miami Veterans Administration Medical Center, Miami, FL, United States.
Respir Med. 2019 Feb;147:13-18. doi: 10.1016/j.rmed.2018.12.012. Epub 2019 Jan 3.
Inspiratory muscle function in COPD has been traditionally described in terms of maximal inspiratory pressure (MIP). Arguably, however, is the day-to-day relevance of MIP, given that individuals rarely need maximal inspiratory forces to perform general tasks, but rather repeated breathing muscle contractions which demand endurance. The sustained maximal inspiratory pressure (SMIP) reflects the ability of the respiratory muscles to maintain force over time (i.e. single-breath work capacity). We investigated the relationships between SMIP and COPD-related clinical outcomes, hypothesizing that SMIP would have superior correlational and discriminatory value when compared to MIP.
61 males with mild-to-very severe airflow obstruction underwent measures of spirometry, whole-body plethysmography, symptomatology, comorbidity, quality of life, exacerbations and mental health. MIP and SMIP were obtained via the Test of Incremental Respiratory Endurance.
The mean ± SD MIP and SMIP were 77.2 ± 22.9 cmHO and 407.9 ± 122.8 PTU. Both MIP and SMIP positively correlated with pulmonary function, with SMIP displaying the highest correlations. We found significant differences in spirometry, hyperinflation, symptomatology, exacerbation frequency, comorbidity, quality of life and anxiety in subjects grouped as having reduced or normal single-breath work capacity. Finally, significantly lower SMIP values were found in individuals with an IC/TLC ratio ≤25%.
The assessment of SMIP appears to have superior clinical value than MIP in COPD. Our analyses revealed that subjects whose SMIP was reduced experienced more severe airflow obstruction, greater hyperinflation, as well as worse health and mental status with increased symptomatology and impaired quality of life.
COPD 患者的吸气肌功能传统上是用最大吸气压力（MIP）来描述的。然而，考虑到个体在完成日常任务时很少需要最大吸气力，而是需要反复的呼吸肌收缩来维持耐力，因此 MIP 的日常相关性可能存在争议。持续最大吸气压力（SMIP）反映了呼吸肌随着时间推移维持力量的能力（即单次呼吸做功能力）。我们研究了 SMIP 与 COPD 相关临床结局之间的关系，假设与 MIP 相比，SMIP 具有更好的相关性和判别价值。
61 名男性患者存在轻至重度气流阻塞，接受了肺量计检查、全身 plethysmography、症状、合并症、生活质量、加重情况和心理健康评估。通过递增呼吸耐力测试获得 MIP 和 SMIP。
MIP 和 SMIP 的平均值（±标准差）分别为 77.2 ± 22.9 cmH2O 和 407.9 ± 122.8 PTU。MIP 和 SMIP 均与肺功能呈正相关，其中 SMIP 的相关性最高。我们发现，在按照单呼吸做功能力降低或正常分组的患者中，肺功能、过度充气、症状、加重频率、合并症、生活质量和焦虑方面存在显著差异。最后，在 IC/TLC 比值≤25%的个体中，SMIP 值显著降低。
与 MIP 相比，SMIP 对 COPD 的评估似乎具有更好的临床价值。我们的分析显示，SMIP 降低的患者经历了更严重的气流阻塞、更大的过度充气以及更严重的健康和心理状态，表现为症状加重和生活质量受损。
