Chest
Volume 142, Issue 6, December 2012, Pages 1455-1460
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Original Research
Critical Care
Diaphragm Muscle Thinning in Patients Who Are Mechanically Ventilated

https://doi.org/10.1378/chest.11-1638Get rights and content

Background

Approximately 40% of patients in medical ICUs require mechanical ventilation (MV). Approximately 20% to 25% of these patients will encounter difficulties in discontinuing MV. Multiple studies have suggested that MV has an unloading effect on the respiratory muscles that leads to diaphragmatic atrophy and dysfunction, a process called ventilator-induced diaphragmatic dysfunction (VIDD). VIDD may be an important factor affecting when and if MV can be discontinued. A sensitive and specific diagnostic test for VIDD could provide the physician with valuable information that might influence decisions regarding extubation or tracheostomy. The purpose of this study was to quantify, using daily sonographic assessments, the rate and degree of diaphragm thinning during MV.

Methods

Seven intubated patients receiving MV during acute care were included. Using sonography, diaphragm muscle thickness was measured daily from the day of intubation until the patient underwent extubation or tracheostomy or died. We analyzed our data using standard descriptive statistics, linear regression, and mixed-model effects.

Results

The overall rate of decrease in the diaphragm thickness of all seven patients over time averaged 6% per day of MV, which differed significantly from zero. Similarly, the diaphragm thickness decreased for each patient over time.

Conclusion

Sonographic assessment of the diaphragm provides noninvasive measurement of diaphragmatic thickness and the degree of diaphragm thinning in patients receiving MV. Our data show that diaphragm muscle thinning starts within 48 h after initiation of MV. However, it is unclear if diaphragmatic thinning correlates with diaphragmatic atrophy or pulmonary function. The relationship between diaphragm thinning and diaphragm strength remains to be elucidated.

Section snippets

Subjects

The St. Luke's-Roosevelt Hospital Institutional Review Board approved this study and designated it study number 09-222. We randomly selected seven newly intubated patients (within 24 h) from the ED, ICU, or medical ward. Patients with tracheostomies were excluded. Informed consent was obtained from the patient or his/her health-care proxy. The patient's chart was reviewed for demographic information and clinical data. Serial ultrasonographic measurements of diaphragm thickness were performed

Results

Overall, the average diaphragm thickness in this group decreased significantly over time at a rate of 6% per day on MV. Similarly, the diaphragm thickness in each patient decreased over time (fig 2). Measurements of diaphragm thickness were taken successfully at end-expiration in all patients. In the group, initial diaphragmatic thickness correlates with weight in kilograms (Pearson correlation coefficient = 0.76, P = .046) (Fig 3).

Linear mixed models revealed that the duration of MV

Discussion

Diaphragm muscle strength has been demonstrated using functional, physiologic, and anatomic methods. Functional measurement includes inspiratory and expiratory pressure differences generated by patients breathing against a closed valve; however, this measurement is effort dependent and poorly reproducible, particularly in intubated, critically ill patients. Esophageal and gastric balloons with pressure transducers can also be used to calculate transdiaphragmatic pressures by subtracting the

Conclusions

We conclude from this study that measured thinning of the diaphragm occurs within 48 h after intubation and the initiation of MV, most consistent with MV-related atrophy. Ultrasound is an easily applied technology in this setting. Further studies are needed to evaluate if this uniform decrease in diaphragm thickness is indeed due to diaphragm atrophy, and if this has an impact on the discontinuation of MV. Larger studies are needed to clarify the relationship between diaphragmatic thinning and

Acknowledgments

Author contributions: Drs J. Lee and Rose had full access to the study data and can vouch for the study integrity and data analysis.

Dr Grosu: contributed to the identification of the purpose of the study, data collection and management, and the writing and revising of the manuscript.

Dr Y. I. Lee: contributed to the creation of the data collection instrument, data collection and management, the creation of the table, and the writing of the manuscript.

Dr J. Lee: contributed to the study design,

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Funding/Support: The authors have reported to CHEST that no funding was received for this study.

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