Diaphragm in health and disease Dr Randeep Guleria M.D.,D.M. Professor and Head

1. Diaphragm in health and disease Dr Randeep Guleria M.D.,D.M. Professor and Head Department of Pulmonary Medicine and Sleep Disorders All India Institute of Medical Sciences New-Delhi

2. Muscles of respiration Diaphragm Intercostals and accessory muscles Abdominal muscles • Diaphragm – main inspiratory muscle • External intercostals and accessory muscle also inspiratory muscles • Abdominal muscles – rectus, transverse abdominis, external and internal oblique • expiratory muscles • Augment passive recoil of lung

3. Respiratory muscles are crucial for ventilation Yet often neglected in day to practice May contribute to dyspnoea and respiratory failure Respiratory muscle assessment important Unexplained dyspnoea may be due to respiratory muscle weakness Generalized neuromuscular diseases have respiratory muscle weakness – often missed NIV helpful if respiratory muscle weakness detected early Respiratory muscle weakness may compound other diseases : malnutrition, steroid, drugs, thyroid disorders, heart failure etc.

4. Respiratory muscle strength Assessment • Clinical • Laboratory – unique, multiple ways • Volume displacement • Pressure generation • Electrophysiological • Radiology

5. Clinical Assessment • Generalized neuromuscular disorder Breathlessness, tachypnoea • Breathlessness – in supine position • Nocturnal hypoventilation • Recurrent aspiration • Paradoxical abdominal movement • Features present when diaphragm strength decreased to ¼th of normal • Significant diaphragm weakness may be overlooked in early stage

6. Lung function Inspiratory muscle weakness • Decreased VC, TLC, Normal RV • DLCO normal when corrected for volume. • Normal VC makes respiratory muscle weakness unlikely. • In diaphragm weakness – VC falls on supine position • Usually > 25% • Useful for monitoring of progression of weakness • Test is volitional • May be non specific & non diagnostic

7. Mouth Pressures • Widely used test for global inspiratory and expiratory muscle strength • Static MIP and MEP at mouth measured • Non invasive tests with established normal value • MIP measured from near RV, RV to FRC • MEP measured from TLC • High MIP (>80 cm H2O) rules out significant inspiratory muscle weakness • Volitional test – 3 equal maximum efforts made

8. Mouth piece scale Mercury Column

9. JAPI 1992;40: 108-110

10. Indian values • 689 healthy school and college students studied • Regression equation derived • Normal values for north Indian subjects also derived Guleria R, Jindal SK Normal maximal expiratory pressures in healthy teenagers JAPI 1992;40:108-110 Pande JN et al Respiratory pressures in normal Indian subjects IJCD 1998 40(4): 251-56

13. Issues with mouth pressure • Simple • At times patient is not able to perform the test • Glottis may close • Buccal pressure may contribute to overall pressures • Negative predictive value

14. Direct transdiphrgmatic pressure values more reliable • Relatively invasive • Oesphageal and gastric balloons needed • Difficult in routine practice • Useful in patients suspected have respiratory muscle and as a research tool

16. Sniff pressures • Sniff Pdi – narrower normal range – better than MIP • About 1/6th patient with low MIP have normal sniff Pdi • Sniff Poes can be used instead of sniff Pdi • Single oesophageal catheter needed • Sniff Poes closely correlates with sniff Pdi • Sniff Poes and sniff Pdi most accurate and reproducible volitional tests for global inspiratory muscle strength

17. sniff oesophageal pressures in a patient

18. Sniff oesphageal pressure - issues • More accurate • Invasive • Difficult to do in routine practice • Patients cooperation needed

19. Nasal Pressures • Sniff pressure at nose measured – SNIP • In normal individuals- pressure in oesophagus and nose show a close relationship • Poes = SNIP • In COPD - SNIP may under estimate esophageal pressure • Simple bedside test • Normal valve established (men > 70 cm H2O. women > 60 cm H2O)

20. Initial approach

21. Utility of SNIP • SNIP and MIP measured in normal, patients with obstructive lung disease (COPD) and with restrictive lung disease (ILD) • Very good correlation in normal and patient with restrictive lung disease • Mild insignificant decrease in COPD • Simple easy to do and reproducible • More patient acceptability • Arora N, Guleria R et al. Am J Respir Crit Care Med 2001;163: 156

25. Thorax 2007;62

26. Transplantation Proceedings 2005;37:664

28. Imaging Useful technique • CXR – P/A, lateral view • Qualitative estimates • Decreased lung volume in B/L palsy • Unilateral palsy easy to differentiate • Fluoroscopy – upward movement of diaphragm • Short sharp sniff – paradoxical movement • Video fluoroscopy may provide dynamic information

29. Ultrasound • Used at sites where there is little air between the probe and the muscle • Easier to visualize the right dome • Craniocaudal movement of the posterior dome measured • Thickness of the diaphragm can also be measured • 1.7 to 3.3 mm at FRC in untrained subjects

30. Diaphragm thicker in subjects with greater inspiratory muscle strength • Unilateral palsy associated with thin costal diaphragm • Increase echogenicity be reported in patients with Duchenne muscular dystrophy

33. Utility in COPD • Evaluated 22 COPD and 21 normal subjects • Simple test, poor echo’s in 2 cases • Paradoxical movement in 2 patients with COPD • Significant correlation between diaphragm movement and SVC, FVC and FEV1 seen • Correlation between MIP also seen – not significant • Fair predictor of lung function and inspiratory muscle pressure • Useful to assess effect of intervention programs – rehabilitation, exercise etc. Narayanan R, Guleria R, Gupta AK, Pande JN. Chest 2000;118: 201

34. Malnutrition and diaphragmatic strength • 24 under nourished (BMI < 18.5) and 26 well nourished (BMI> 18.5) individual evaluated. • Anthropometry • MIP, SNIP, Sniff esophageal pressure • US assessment – movement & thickness done • Correlation between strength and nutritional status observed • Mild to moderate malnutrition had little effect on strength & thickness of diaphragm Malav IC, Guleria R, Gupta AK, Pande JN, Sharma SK, Misra A. Chest 2006;130: 248S.

35. European J of Endocrinology 2002;147:299-303

38. Combination of tests increases diagnostic precision. Having multiple rests of respiratory muscle function available both increases diagnostic precision and makes possible in a range of clinical circumstances

39. Indian J Chest Dis. Allied Sci. 2009 Apr-Jun; 51 (2) : 83-5

41. Non volitional tests • Oesophageal and gastric balloons placed • Phrenic nerve studied • Electric • Magnetic • Oesophageal pressure, gastric pressure and Pdi measured

42. Electric Stimulation • Phrenic nerve stimulation done in neck at FRC • Twitch Pdi measured • Uncomfortable - repeated stimulation needed for precise electrode placement. • Patient unable to relax – twitch potentiation • Unilateral and bilateral electric stimulation done • Normal twitch Pdi – 8.8 to 33 cm H2O

44. Magnetic stimulation • Magnetic coil used • Pulsed magnetic field causes current to flow in nervous tissue within the field • Circular coil used over cervical phrenic nerve roots • Magnetic Pdi slightly greater than electric Pdi • Painless & reproducible procedure • Figure of 8 coil used for hemidiaphragm assessment

48. Am J Respir Crit Care Med 1999; 160(2):513-22.

49. Fatigue and endurance • Ventilatory endurance tests • Maximum sustainable ventilation • 70 – 80% MVV for 8 minutes • 20% MVV, increase by 10% every 3 minutes • Threshold loading- weighted plungers/ valves • Repeated MIP • 18 repeated MIP maneuvers – each effort for 10 seconds with a 5 second rest • Resistive loading