Diaphragmatic Motion Using Linear Ultrasound

Study Overview
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Brief Summary
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This study evaluates the movement of the diaphragm (which is the main muscle used for breathing). It will compare two ultrasound modalities: linear ultrasound versus curvilinear ultrasound, at measuring diaphragm motion. The proposed measurement method with linear ultrasound is novel, and will be compared against the established method with curvilinear ultrasound. The investigators hypothesize that the novel method will have several potential advantages, including: it may be easier to learn, quicker to perform, and have a lower failure rate.

Detailed Description
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Background: Multiple pathologies cause diaphragmatic dysfunction, including: respiratory, abdominal and neurological disease. Established clinical tests of diaphragmatic function, include: the transdiaphragmatic pressure, the maximal static inspiratory pressure, the sniff inspiratory pressure, pulmonary function tests, electromyography, a chest radiograph or fluoroscopy. However ultrasound assessment of diaphragmatic function is a non-invasive, radiation-free technique that has gained traction in clinical practice in recent years. Several different methods have been described, that examine motion in two different areas of the diaphragm, either the zone of apposition, or the dome of the diaphragm, however no one method has emerged as the standard of care. The current conventional technique (using B-mode or M-mode ultrasound via a phased array or curvilinear probe) in the subcostal region, has several limitations: It can be difficult to measure right hemi-diaphragm excursion with deep breathing, with a failure rate of up to 28% described for quantitative assessment. It is even more difficult to quantitatively assess left hemi-diaphragmatic excursion with deep breathing, as the spleen provides a smaller window compared to the liver window. Failure rates of 79% and 65% have been reported. When using M-mode, the ultrasound beam must image the diaphragmatic excursion line at a perpendicular angle, otherwise reproducibility and accuracy are adversely effected. The investigators propose a novel method, using linear ultrasound to examine the zone of apposition, and determine diaphragmatic excursion at end inspiration and expiration. In theory this technique may have a number of advantages over the conventional method. It is likely easier to learn, quicker to perform, and has a lower failure rate for imaging the diaphragm on both sides during deep breathing. The investigators will compare this method to the conventional method, i.e. a curvilinear probe as described above. Hypothesis: Diaphragmatic motion can be assessed more rapidly, and more reliably via a linear high frequency ultrasound probe, than a curved low frequency probe. Primary Objective: - To evaluate the ease and success of using a novel technique of point-of-care ultrasound diaphragm assessment with a linear probe in the mid-axillary line to measure diaphragmatic motion. The ease of procedure will be determined by the time and the number of attempts required to perform the ultrasound assessment. Secondary Objectives: To determine the normal range of diaphragmatic excursion values from full expiration to full inspiration in men and women; To quantify the reduction in diaphragmatic motion following phrenic nerve palsy - due to an interscalene or supraclavicular brachial plexus block; To compare the finding of diminished diaphragmatic excursion with the conventional method of measurement; i.e. compare the sensitivity and specificity of the tests. To analyze the success rate of measuring the left and right hemi-diaphragmatic movement as compared with the conventional method of measurement. This prospective observational study, will involve patients undergoing elective surgery, and will consist of two phases: Phase 1: The first phase will be to evaluate a new lung ultrasound technique to measure diaphragmatic excursion using a linear probe in the mid-axillary line. This will involve scanning 75 healthy patients undergoing elective surgery to determine normal reference values for this technique in men and women. Phase 2: The second phase will involve 100 patients who are undergoing an interscalene or supraclavicular brachial plexus block as part of their perioperative analgesic management for shoulder or arm surgery. This cohort of patient is likely to develop phrenic nerve palsy as a side effect of the brachial plexus block. The resultant phrenic nerve palsy, will result in reduced diaphragmatic motion, and the aim will be to evaluate the ability of using a linear probe technique to measure this reduction as compared to the conventional method of measurement.

Official Title
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A Novel Method to Measure Diaphragmatic Motion and Excursion

Conditions
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Diaphragm; Movement, Examination of Diaphragm Movement Using Ultrasound

Intervention / Treatment
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* Diagnostic Test: Linear Ultrasound to Measure Diaphragmatic Movement
* Diagnostic Test: Curvilinear Ultrasound to Measure Diaphragmatic Movement
* Diagnostic Test: Pulmonary function tests


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Phase 1 Any healthy adult patient undergoing elective surgery Phase 2 Any adult patient, undergoing elective upper limb surgery that involves an interscalene or supraclavicular brachial plexus block. Exclusion Criteria: (i) Inability to obtain an informed consent (e.g. language barrier) (ii) BMI > 35 (iii) Known pre-existing diaphragmatic dysfunction (iv) Existing lung pathology Smoker Known abnormal pulmonary function tests Severe pulmonary disease e.g., COPD, asthma, pulmonary fibrosis, or any other significant respiratory disease that would adversely affect diaphragm function or pulmonary function tests Additional Criteria for Phase 2 Any contraindication to an interscalene or supraclavicular brachial plexus block

Ages Eligible for Study
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Minimum Age: 18 Years

Sexes Eligible for Study
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All

Study Plan
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How is the study designed?
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Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Phase 1<br>The first phase will be to evaluate a new lung ultrasound technique to measure diaphragmatic excursion using a linear probe in the mid-axillary line. This will involve scanning 75 healthy patients undergoing elective surgery to determine normal reference values in men and women. The following interventions will be carried out: (i) Measurement of diaphragmatic movement with a linear ultrasound probe on both sides of the chest (ii) Measurement of diaphragmatic movement with a curved ultrasound probe on both sides of the chest | Diagnostic Test: Linear Ultrasound to Measure Diaphragmatic Movement<br>* A linear 10-12 MHz ultrasound probe will be used to determine diaphragmatic excursion, by examining the zone of apposition. Diaphragmatic excursion will be measured from end inspiration to end expiration. The measurement will be repeated twice, and an average of the two will be taken. The distance between the two external skin markings, one at the end of full expiration and one at the end of full inspiration will indicate the excursion of the diaphragm.<br>Diagnostic Test: Curvilinear Ultrasound to Measure Diaphragmatic Movement<br>* A curvilinear 2-5 MHz ultrasound probe will be used to determine diaphragmatic excursion, by examining the dome of the diaphragm. M-mode will be used to image the motion of the diaphragm from end inspiration to end expiration. The measurement will be repeated twice, and an average of the two will be taken.<br>|
| Phase 2<br>This will involve patients undergoing an interscalene / supraclavicular brachial plexus block for their routine care, it will examine the reduction in diaphragmatic motion due to phrenic nerve palsy. Interventions: (i) Measurement of diaphragmatic movement with a linear ultrasound probe bilaterally. (ii) Measurement of diaphragmatic movement with a curved ultrasound probe bilaterally. (iii) Pulmonary function tests prior to the brachial plexus block (iv) Planned supraclavicular / interscalene block by the clinical team. (v) Repeat measurement of diaphragmatic movement with linear ultrasound, only on the side of the brachial plexus block. (vi) Repeat measurement of diaphragmatic movement with curved ultrasound, only on the side of the brachial plexus block. | Diagnostic Test: Linear Ultrasound to Measure Diaphragmatic Movement<br>* A linear 10-12 MHz ultrasound probe will be used to determine diaphragmatic excursion, by examining the zone of apposition. Diaphragmatic excursion will be measured from end inspiration to end expiration. The measurement will be repeated twice, and an average of the two will be taken. The distance between the two external skin markings, one at the end of full expiration and one at the end of full inspiration will indicate the excursion of the diaphragm.<br>Diagnostic Test: Curvilinear Ultrasound to Measure Diaphragmatic Movement<br>* A curvilinear 2-5 MHz ultrasound probe will be used to determine diaphragmatic excursion, by examining the dome of the diaphragm. M-mode will be used to image the motion of the diaphragm from end inspiration to end expiration. The measurement will be repeated twice, and an average of the two will be taken.<br>Diagnostic Test: Pulmonary function tests<br>* Bedside pulmonary function tests to measure forced vital capacity (FVC). The FVC measures the maximal volume of gas that can be expired as forcefully and rapidly as possible after a maximal inspiration to total lung capacity. This measurement will help determine if the patient has any obstructive or restrictive diseases of the airways. Three measurements will be taken.<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Time taken to measure diaphragmatic excursion | To measure in minutes the time taken to quantify diaphragmatic excursion from end inspiration to end expiration, and to compare the linear probe versus the curvilinear probe. | 60 minutes | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Normal range of values for diaphragmatic excursion using linear ultrasound | To determine the normal range of values for diaphragmatic excursion from end expiration to end inspiration in men and women | 30 mins | 
| Quantify and compare the reduction in diaphragmatic motion following a phrenic nerve block | To quantify and compare the reduction in diaphragmatic motion (% change from baseline) following a phrenic nerve block using both linear and curved ultrasound probes | 2 hours | 
| Success rate of measuring both the left and right hemi-diaphragmatic movement | To analyze the success rate of measuring both the left and right hemi-diaphragmatic movement; success is defined as successful capture of a good view of the diaphragm and its movement on sonogram using the B mode and M mode scan | 60 mins |