CASE CONFERENCES The Clinical Physiologist Section Editor: John W. Kreit, M.D.
Dyspnea of Unknown Cause Think about Diaphragm Pauliane V. Santana1, Elena Prina1,2, Pedro Caruso1, Carlos R. R. Carvalho1, and Andre L. P. Albuquerque1 1
Pulmonary Division, Heart Institute (InCor), Hospital das Clı´nicas, Faculdade de Medicina da Universidade de Sa˜o Paulo, Sa˜o Paulo, Brazil; and 2Hospital Clinic, IDIBAPS, Universitat de Barcelona, Servei de Pneumologia, Institut del Torax, Barcelona, Spain
Keywords: diaphragm; ultrasound; dyspnea
In Brief A patient with 2 weeks of breathlessness during daily activities and intense pain in the right shoulder was referred for physiological evaluation. A chest radiograph showed new right hemidiaphragm elevation, pulmonary function tests demonstrated reduced lung volumes, and maximum inspiratory pressure was markedly reduced. Additional testing based on an understanding of the structure, function, and innervation of the diaphragm confirmed the diagnosis. Figure 1. The chest radiograph shows a markedly elevated right hemidiaphragm (A), which was not present 1 month earlier (B).
The Clinical Challenge A 58-year-old man was admitted for evaluation of effort-related breathlessness over the preceding 2 weeks. He denied fever, weight loss, chest pain, palpitations, and cough or sputum production. He also complained of intense right shoulder pain with movement limitation of the right arm. The patient’s medical history included obesity (body mass index = 39 kg/m2), hypertension, dyslipidemia, and chronic left leg weakness from poliomyelitis. He had never smoked and denied any other respiratory or cardiovascular symptoms or diseases in the past.
On examination, the patient was tachypneic, with a respiratory rate of 26 breaths/min. Vital signs were otherwise normal, and pulse oximetry was 93% on room air. Auscultation of the chest revealed diminished breath sounds in the inferior region of the right
lung without crackles or wheezes. Abdominal examination was unremarkable. Neurologic evaluation Table 2. Volitional tests of respiratory muscle function
Table 1. Lung function tests
FEV1 FVC TLC
Values (L)
% Predicted
1.58 2.03 4.18
58 56 77
MIP, cm H2O MEP, cm H2O SNIP, cm H2O
Result
Normal
239 127 48
,270 .80.5 .50
Definition of abbreviations: MEP = maximal expiratory pressure; MIP = maximal inspiratory pressure; SNIP = sniff nasal inspiratory pressure.
(Received in original form April 28, 2014; accepted in final form September 3, 2014 ) The Respiratory Muscle Lab is supported by FAPESP (Process 2010/08947-9); Dr Prina is supported by Long Term Fellowship 2013 from European Respiratory Society. Correspondence and requests for reprints should be addressed to Andre L. P. Albuquerque, M.D., Ph.D., Pulmonary Division, Heart Institute (InCor), Hospital das Cl´ınicas, Faculdade de Medicina da Universidade de Sa˜o Paulo, Av Dr Eneas de Carvalho Aguiar, 44, sala 1, 58 andar, Cerqueira Cesar, Sa˜o Paulo, 05403-000, Brazil. E-mail: [email protected] Ann Am Thorac Soc Vol 11, No 10, pp 1656–1659, Dec 2014 Copyright © 2014 by the American Thoracic Society DOI: 10.1513/AnnalsATS.201404-181CC Internet address: www.atsjournals.org
1656
AnnalsATS Volume 11 Number 10 | December 2014
CASE CONFERENCES
TLC
Deep Breathing
Sniff
Esophageal
Mobility
QB
10 5 0 –5 –10 –15 –20
Δ=8
0:02:38
Δ=25
Δ=65
0:02:39
30.500
31.000
25
Gastric
Diaphragm
B
20
Δ=9
15
Δ=15
10
Δ=3
5 0:02:38
Pdi
Pressure, cm H2O
FRC
Thickness
Diaphragm
A
35 30 25 20 15 10 5 0
30.500
0:02:39
Δ=17
Δ=28
31.000
Δ=80
Scalene
200 100 0 –100
200
Sternoc
EMG, μV
–200
100 0 –100 –200
Figure 2. (A) M-mode ultrasound measurements of right hemidiaphragm thickness at FRC and TLC. (B) M-mode ultrasound images, esophageal (Pes), gastric (Pga), and transdiaphragmatic (Pdi) pressure measurements, and EMG activity of accessory inspiratory muscles during tidal and deep inspiration and during a sniff maneuver. There was paradoxical movement of the right hemidiaphragm during the sniff maneuver (arrow). E = expiration; I = inspiration; Sternoc = sternocleidomastoid.
revealed mild right arm weakness. There was no leg swelling or tenderness. We could not accurately assess for paradoxical abdominal movement in either the sitting or the supine position due to the patient’s obesity. The chest Case Conferences
radiograph (Figure 1) showed an elevated right hemidiaphragm, which had not been present 1 month earlier. Pulmonary function tests demonstrated reduced lung volumes (Table 1).
Questions 1. What is the most likely cause of this patient’s exertional dyspnea? 2. How can the diagnosis be confirmed? 1657
CASE CONFERENCES Table 3. Transdiaphragmatic pressure measurements during bilateral and unilateral phrenic nerve stimulation Result
Normal
11.0 4.0 10.0
.18 .7 .8
Bilateral phrenic nerve stimulation Right phrenic nerve stimulation Left phrenic nerve stimulation
What is the significance of the patient’s shoulder pain?
Clinical Reasoning Exertional dyspnea is a common symptom that can be caused by respiratory, cardiovascular, or neuromuscular disorders. The finding of new right hemidiaphragm elevation suggested hemidiaphragm weakness or paralysis as the cause of our patient’s dyspnea, and the results of pulmonary function testing were consistent with this diagnosis. Standard volitional tests of respiratory muscle strength were subsequently performed (Table 2). Although expiratory muscle strength was normal, inspiratory muscle strength, as assessed by maximal inspiratory pressure and sniff nasal inspiratory pressure, was markedly reduced.
The Clinical Solution We performed ultrasonography using linear array (6–13 MHz) and convex (2–5 MHz)
probes; measured esophageal, gastric, and transdiaphragmatic pressures; and monitored the EMG activity of the scalene and sternocleidomastoid muscles (Figure 2). The thickness of the right hemidiaphragm was normal during quiet breathing but decreased with deep inspiration. During tidal inspiration, there was no movement of the right hemidiaphragm, transdiaphragmatic pressure was abnormally low, and there was no recruitment of the accessory inspiratory muscles. With deep inspiration, there was still no movement of the right hemidiaphragm. Transdiaphragmatic pressure increased, but this was due primarily to the drop in esophageal pressure produced by contraction of the scalene and sternocleidomastoid muscles. During a sniff maneuver, there was paradoxical (upward) movement of the right hemidiaphragm, and the increase in transdiaphragmatic pressure was again due primarily to recruitment of the accessory muscles. As shown in Table 3, transdiaphragmatic pressure was reduced during bilateral phrenic nerve stimulation. Deep Breathing
Tidal Breathing
Pes
+
+
+
Pes
Pdi Pdi Pga
+ +
+ +
+ +
Pga
Diaphragm Mobility quiet breathing=1.08–2.6 cm Thickness FRC ≥ 0.15 cm
The Science behind the Solution Structure, Function, and Nerve Supply of the Diaphragm
The diaphragm is a dome-shaped muscle that is inserted peripherally onto the inner surfaces of the lower ribs and lumbar vertebrae. It is anatomically and functionally divided into costal and crural regions and consists primarily of high-oxidative fibers that are resistant to fatigue. As shown in Figure 3, during inspiration, the diaphragm flattens, which increases lung volume and reduces pleural and alveolar pressure. At the same time, the accompanying rise in intraabdominal pressure forces the lower ribs outward. This expands the chest wall, which further increases lung volume and reduces pleural and alveolar pressure. Each side of the diaphragm (hemidiaphragm) is innervated by a phrenic nerve, which originates from the C3–C5 nerve roots. The higher cervical nerve roots supply the costal portion of the diaphragm, whereas the crural region is innervated by the lower segments. Each phrenic nerve enters the thoracic cavity posteriorly and then moves anteriorly onto the pericardium. The right phrenic nerve enters the diaphragm just lateral to the caval hiatus, and the left phrenic nerve intersects adjacent to the left heart border.
Mobility deep breathing=6.55–9.21 cm
Assessment of Diaphragm Function Thickness TLC ≥ 20% thickness of FRC
Figure 3. During inspiration, flattening of the diaphragm increases intrathoracic and lung volume. This reduces pleural (esophageal) and alveolar pressure and increases intraabdominal (gastric) pressure. The rise in intraabdominal pressure further increases intrathoracic and lung volume by pushing the lower rib cage outward. The pressure and volume changes increase with the depth of inspiration. Normal diaphragm mobility and thickness, as measured using ultrasonography, are shown. Pes = esophageal pressure; Pga = gastric pressure; Pdi = transdiaphragmatic pressure.
1658
When each phrenic nerve was stimulated separately, only right hemidiaphragm function was abnormal. The results of ultrasonography and transdiaphragmatic pressure measurements confirmed the diagnosis of right hemidiaphragm paralysis. Because the phrenic nerves (C3–C5) and the brachial plexus (C5–T1) originate from overlapping regions of the cervical spinal cord, our patient’s right arm pain and weakness suggested the diagnosis of acute neuralgic amyotrophy, or Parsonage-Turner syndrome.
Diaphragm function can be evaluated by examining its location and movement and by measuring the pressures generated during contraction. Imaging. Normally, the dome of the right hemidiaphragm is 1 to 2 cm higher than the left at end-expiration, and both
AnnalsATS Volume 11 Number 10 | December 2014
CASE CONFERENCES sides move downward during inspiration. Weakness or paralysis typically causes marked elevation of the affected hemidiaphragm, and the diagnosis is often first suspected based on the appearance of the chest radiograph. Diaphragm movement has traditionally been assessed using fluoroscopy. When one hemidiaphragm is weak or paralyzed, there is little or no movement during tidal and deep inspiration. During rapid inspiration through the nose (sniff test), a paralyzed hemidiaphragm moves paradoxically upward. Recently, ultrasound has become a popular alternative to fluoroscopy because of its portability and the lack of radiation exposure. Two types of measurements may be performed. The first is the distance that each hemidiaphragm moves during breathing and a sniff maneuver, and the second is the thickness of the diaphragm adjacent to the lower ribs (the zone of apposition). Studies have shown that normal diaphragm excursion ranges between 1.08 and 2.6 cm during tidal breathing and between 6.55 and 9.21 cm during deep inspiration (Figure 3). Diaphragm thickness is normally at least 0.15 cm and increases by more than 20% between the beginning and end of a deep inspiration. Abnormal thinning of the diaphragm is characteristic of long-term weakness or paralysis. Interestingly, the thickness of our patient’s
right hemidiaphragm was normal during quiet breathing but decreased during deep inspiration (Figure 2). To the best of our knowledge, this finding has not been previously described in patients with acute diaphragm weakness. Pressure measurements. The pressure generated by the diaphragm is most commonly assessed by measuring mouth pressure during a maximal inspiratory effort against a closed shutter (maximum inspiratory pressure). The pressure reached during a maximal sniff maneuver (sniff nasal inspiratory pressure) can also be measured. Although readily available and easy to perform, these tests are neither sensitive nor specific for diaphragm weakness because they are highly dependent on patient effort and reflect the activity of the accessory inspiratory muscles as well as the diaphragm. Diaphragm function is more accurately assessed by measuring the pressure gradient across its surface. Transdiaphragmatic pressure (Pdi) is the difference between intraabdominal and intrathoracic pressure, which are measured using balloon-tipped catheters in the stomach (gastric pressure [Pga]) and the lower esophagus (esophageal pressure [Pes]). Pdi ¼ Pga 2 Pes In healthy subjects, Pdi increases during inspiration as intraabdominal pressure rises
Recommended Reading Qureshi A. Diaphragm paralysis. Semin Respir Crit Care Med 2009;30:315–320. American Thoracic Society/European Respiratory Society. ATS/ERS Statement on respiratory muscle testing. Am J Respir Crit Care Med 2002;166:518–624. Testa A, Soldati G, Giannuzzi R, Berardi S, Portale G, Gentiloni Silveri N. Ultrasound M-mode assessment of diaphragmatic kinetics by anterior transverse scanning in healthy subjects. Ultrasound Med Biol 2011;37:44–52. Boon AJ, Harper CJ, Ghahfarokhi LS, Strommen JA, Watson JC, Sorenson EJ. Two-dimensional ultrasound imaging of the diaphragm:
Case Conferences
and intrathoracic pressure becomes more negative. Transdiaphragmatic pressure can be measured during tidal or deep inspiration or during a maximal sniff maneuver. Alternatively, pressure measurements can be obtained using magnetic stimulation of the phrenic nerves. This has much greater sensitivity and specificity than volitional testing because it eliminates the confounding effects of patient effort and accessory muscle activity and allows each hemidiaphragm to be tested separately. Acute Neuralgic Amyotrophy
Our patient was diagnosed with acute neuralgic amyotrophy, which is also known as Parsonage-Turner syndrome. This is an acute brachial neuropathy, which causes pain and weakness of the shoulder and arm muscles. Phrenic nerve involvement, which may be unilateral or bilateral, occurs in fewer than 10% of cases. Typically, this disorder is self-limited, and there is complete recovery of upper limb function. Unfortunately, in patients with phrenic nerve involvement, recovery of diaphragm function is often slow and incomplete. n Author disclosures are available with the text of this article at www.atsjournals.org.
quantitative values in normal subjects. Muscle Nerve 2013;47: 884–889. Lahrmann H, Grisold W, Authier FJ, Zifko UA. Neuralgic amyotrophy with phrenic nerve involvement. Muscle Nerve 1999;22:437–442. Gottesman E, McCool FD. Ultrasound evaluation of the paralyzed diaphragm. Am J Respir Crit Care Med 1997;155:1570–1574. Nason LK, Walker CM, McNeeley MF, Burivong W, Fligner CL, Godwin JD. Imaging of the diaphragm: anatomy and function. Radiographics 2012;32:E51–E70. McCool FD, Tzelepis GE. Dysfunction of the diaphragm. N Engl J Med 2012;366:932–942.
1659
Dyspnea of Unknown Cause Think about Diaphragm Pauliane V. Santana1, Elena Prina1,2, Pedro Caruso1, Carlos R. R. Carvalho1, and Andre L. P. Albuquerque1 1
Pulmonary Division, Heart Institute (InCor), Hospital das Clı´nicas, Faculdade de Medicina da Universidade de Sa˜o Paulo, Sa˜o Paulo, Brazil; and 2Hospital Clinic, IDIBAPS, Universitat de Barcelona, Servei de Pneumologia, Institut del Torax, Barcelona, Spain
Keywords: diaphragm; ultrasound; dyspnea
In Brief A patient with 2 weeks of breathlessness during daily activities and intense pain in the right shoulder was referred for physiological evaluation. A chest radiograph showed new right hemidiaphragm elevation, pulmonary function tests demonstrated reduced lung volumes, and maximum inspiratory pressure was markedly reduced. Additional testing based on an understanding of the structure, function, and innervation of the diaphragm confirmed the diagnosis. Figure 1. The chest radiograph shows a markedly elevated right hemidiaphragm (A), which was not present 1 month earlier (B).
The Clinical Challenge A 58-year-old man was admitted for evaluation of effort-related breathlessness over the preceding 2 weeks. He denied fever, weight loss, chest pain, palpitations, and cough or sputum production. He also complained of intense right shoulder pain with movement limitation of the right arm. The patient’s medical history included obesity (body mass index = 39 kg/m2), hypertension, dyslipidemia, and chronic left leg weakness from poliomyelitis. He had never smoked and denied any other respiratory or cardiovascular symptoms or diseases in the past.
On examination, the patient was tachypneic, with a respiratory rate of 26 breaths/min. Vital signs were otherwise normal, and pulse oximetry was 93% on room air. Auscultation of the chest revealed diminished breath sounds in the inferior region of the right
lung without crackles or wheezes. Abdominal examination was unremarkable. Neurologic evaluation Table 2. Volitional tests of respiratory muscle function
Table 1. Lung function tests
FEV1 FVC TLC
Values (L)
% Predicted
1.58 2.03 4.18
58 56 77
MIP, cm H2O MEP, cm H2O SNIP, cm H2O
Result
Normal
239 127 48
,270 .80.5 .50
Definition of abbreviations: MEP = maximal expiratory pressure; MIP = maximal inspiratory pressure; SNIP = sniff nasal inspiratory pressure.
(Received in original form April 28, 2014; accepted in final form September 3, 2014 ) The Respiratory Muscle Lab is supported by FAPESP (Process 2010/08947-9); Dr Prina is supported by Long Term Fellowship 2013 from European Respiratory Society. Correspondence and requests for reprints should be addressed to Andre L. P. Albuquerque, M.D., Ph.D., Pulmonary Division, Heart Institute (InCor), Hospital das Cl´ınicas, Faculdade de Medicina da Universidade de Sa˜o Paulo, Av Dr Eneas de Carvalho Aguiar, 44, sala 1, 58 andar, Cerqueira Cesar, Sa˜o Paulo, 05403-000, Brazil. E-mail: [email protected] Ann Am Thorac Soc Vol 11, No 10, pp 1656–1659, Dec 2014 Copyright © 2014 by the American Thoracic Society DOI: 10.1513/AnnalsATS.201404-181CC Internet address: www.atsjournals.org
1656
AnnalsATS Volume 11 Number 10 | December 2014
CASE CONFERENCES
TLC
Deep Breathing
Sniff
Esophageal
Mobility
QB
10 5 0 –5 –10 –15 –20
Δ=8
0:02:38
Δ=25
Δ=65
0:02:39
30.500
31.000
25
Gastric
Diaphragm
B
20
Δ=9
15
Δ=15
10
Δ=3
5 0:02:38
Pdi
Pressure, cm H2O
FRC
Thickness
Diaphragm
A
35 30 25 20 15 10 5 0
30.500
0:02:39
Δ=17
Δ=28
31.000
Δ=80
Scalene
200 100 0 –100
200
Sternoc
EMG, μV
–200
100 0 –100 –200
Figure 2. (A) M-mode ultrasound measurements of right hemidiaphragm thickness at FRC and TLC. (B) M-mode ultrasound images, esophageal (Pes), gastric (Pga), and transdiaphragmatic (Pdi) pressure measurements, and EMG activity of accessory inspiratory muscles during tidal and deep inspiration and during a sniff maneuver. There was paradoxical movement of the right hemidiaphragm during the sniff maneuver (arrow). E = expiration; I = inspiration; Sternoc = sternocleidomastoid.
revealed mild right arm weakness. There was no leg swelling or tenderness. We could not accurately assess for paradoxical abdominal movement in either the sitting or the supine position due to the patient’s obesity. The chest Case Conferences
radiograph (Figure 1) showed an elevated right hemidiaphragm, which had not been present 1 month earlier. Pulmonary function tests demonstrated reduced lung volumes (Table 1).
Questions 1. What is the most likely cause of this patient’s exertional dyspnea? 2. How can the diagnosis be confirmed? 1657
CASE CONFERENCES Table 3. Transdiaphragmatic pressure measurements during bilateral and unilateral phrenic nerve stimulation Result
Normal
11.0 4.0 10.0
.18 .7 .8
Bilateral phrenic nerve stimulation Right phrenic nerve stimulation Left phrenic nerve stimulation
What is the significance of the patient’s shoulder pain?
Clinical Reasoning Exertional dyspnea is a common symptom that can be caused by respiratory, cardiovascular, or neuromuscular disorders. The finding of new right hemidiaphragm elevation suggested hemidiaphragm weakness or paralysis as the cause of our patient’s dyspnea, and the results of pulmonary function testing were consistent with this diagnosis. Standard volitional tests of respiratory muscle strength were subsequently performed (Table 2). Although expiratory muscle strength was normal, inspiratory muscle strength, as assessed by maximal inspiratory pressure and sniff nasal inspiratory pressure, was markedly reduced.
The Clinical Solution We performed ultrasonography using linear array (6–13 MHz) and convex (2–5 MHz)
probes; measured esophageal, gastric, and transdiaphragmatic pressures; and monitored the EMG activity of the scalene and sternocleidomastoid muscles (Figure 2). The thickness of the right hemidiaphragm was normal during quiet breathing but decreased with deep inspiration. During tidal inspiration, there was no movement of the right hemidiaphragm, transdiaphragmatic pressure was abnormally low, and there was no recruitment of the accessory inspiratory muscles. With deep inspiration, there was still no movement of the right hemidiaphragm. Transdiaphragmatic pressure increased, but this was due primarily to the drop in esophageal pressure produced by contraction of the scalene and sternocleidomastoid muscles. During a sniff maneuver, there was paradoxical (upward) movement of the right hemidiaphragm, and the increase in transdiaphragmatic pressure was again due primarily to recruitment of the accessory muscles. As shown in Table 3, transdiaphragmatic pressure was reduced during bilateral phrenic nerve stimulation. Deep Breathing
Tidal Breathing
Pes
+
+
+
Pes
Pdi Pdi Pga
+ +
+ +
+ +
Pga
Diaphragm Mobility quiet breathing=1.08–2.6 cm Thickness FRC ≥ 0.15 cm
The Science behind the Solution Structure, Function, and Nerve Supply of the Diaphragm
The diaphragm is a dome-shaped muscle that is inserted peripherally onto the inner surfaces of the lower ribs and lumbar vertebrae. It is anatomically and functionally divided into costal and crural regions and consists primarily of high-oxidative fibers that are resistant to fatigue. As shown in Figure 3, during inspiration, the diaphragm flattens, which increases lung volume and reduces pleural and alveolar pressure. At the same time, the accompanying rise in intraabdominal pressure forces the lower ribs outward. This expands the chest wall, which further increases lung volume and reduces pleural and alveolar pressure. Each side of the diaphragm (hemidiaphragm) is innervated by a phrenic nerve, which originates from the C3–C5 nerve roots. The higher cervical nerve roots supply the costal portion of the diaphragm, whereas the crural region is innervated by the lower segments. Each phrenic nerve enters the thoracic cavity posteriorly and then moves anteriorly onto the pericardium. The right phrenic nerve enters the diaphragm just lateral to the caval hiatus, and the left phrenic nerve intersects adjacent to the left heart border.
Mobility deep breathing=6.55–9.21 cm
Assessment of Diaphragm Function Thickness TLC ≥ 20% thickness of FRC
Figure 3. During inspiration, flattening of the diaphragm increases intrathoracic and lung volume. This reduces pleural (esophageal) and alveolar pressure and increases intraabdominal (gastric) pressure. The rise in intraabdominal pressure further increases intrathoracic and lung volume by pushing the lower rib cage outward. The pressure and volume changes increase with the depth of inspiration. Normal diaphragm mobility and thickness, as measured using ultrasonography, are shown. Pes = esophageal pressure; Pga = gastric pressure; Pdi = transdiaphragmatic pressure.
1658
When each phrenic nerve was stimulated separately, only right hemidiaphragm function was abnormal. The results of ultrasonography and transdiaphragmatic pressure measurements confirmed the diagnosis of right hemidiaphragm paralysis. Because the phrenic nerves (C3–C5) and the brachial plexus (C5–T1) originate from overlapping regions of the cervical spinal cord, our patient’s right arm pain and weakness suggested the diagnosis of acute neuralgic amyotrophy, or Parsonage-Turner syndrome.
Diaphragm function can be evaluated by examining its location and movement and by measuring the pressures generated during contraction. Imaging. Normally, the dome of the right hemidiaphragm is 1 to 2 cm higher than the left at end-expiration, and both
AnnalsATS Volume 11 Number 10 | December 2014
CASE CONFERENCES sides move downward during inspiration. Weakness or paralysis typically causes marked elevation of the affected hemidiaphragm, and the diagnosis is often first suspected based on the appearance of the chest radiograph. Diaphragm movement has traditionally been assessed using fluoroscopy. When one hemidiaphragm is weak or paralyzed, there is little or no movement during tidal and deep inspiration. During rapid inspiration through the nose (sniff test), a paralyzed hemidiaphragm moves paradoxically upward. Recently, ultrasound has become a popular alternative to fluoroscopy because of its portability and the lack of radiation exposure. Two types of measurements may be performed. The first is the distance that each hemidiaphragm moves during breathing and a sniff maneuver, and the second is the thickness of the diaphragm adjacent to the lower ribs (the zone of apposition). Studies have shown that normal diaphragm excursion ranges between 1.08 and 2.6 cm during tidal breathing and between 6.55 and 9.21 cm during deep inspiration (Figure 3). Diaphragm thickness is normally at least 0.15 cm and increases by more than 20% between the beginning and end of a deep inspiration. Abnormal thinning of the diaphragm is characteristic of long-term weakness or paralysis. Interestingly, the thickness of our patient’s
right hemidiaphragm was normal during quiet breathing but decreased during deep inspiration (Figure 2). To the best of our knowledge, this finding has not been previously described in patients with acute diaphragm weakness. Pressure measurements. The pressure generated by the diaphragm is most commonly assessed by measuring mouth pressure during a maximal inspiratory effort against a closed shutter (maximum inspiratory pressure). The pressure reached during a maximal sniff maneuver (sniff nasal inspiratory pressure) can also be measured. Although readily available and easy to perform, these tests are neither sensitive nor specific for diaphragm weakness because they are highly dependent on patient effort and reflect the activity of the accessory inspiratory muscles as well as the diaphragm. Diaphragm function is more accurately assessed by measuring the pressure gradient across its surface. Transdiaphragmatic pressure (Pdi) is the difference between intraabdominal and intrathoracic pressure, which are measured using balloon-tipped catheters in the stomach (gastric pressure [Pga]) and the lower esophagus (esophageal pressure [Pes]). Pdi ¼ Pga 2 Pes In healthy subjects, Pdi increases during inspiration as intraabdominal pressure rises
Recommended Reading Qureshi A. Diaphragm paralysis. Semin Respir Crit Care Med 2009;30:315–320. American Thoracic Society/European Respiratory Society. ATS/ERS Statement on respiratory muscle testing. Am J Respir Crit Care Med 2002;166:518–624. Testa A, Soldati G, Giannuzzi R, Berardi S, Portale G, Gentiloni Silveri N. Ultrasound M-mode assessment of diaphragmatic kinetics by anterior transverse scanning in healthy subjects. Ultrasound Med Biol 2011;37:44–52. Boon AJ, Harper CJ, Ghahfarokhi LS, Strommen JA, Watson JC, Sorenson EJ. Two-dimensional ultrasound imaging of the diaphragm:
Case Conferences
and intrathoracic pressure becomes more negative. Transdiaphragmatic pressure can be measured during tidal or deep inspiration or during a maximal sniff maneuver. Alternatively, pressure measurements can be obtained using magnetic stimulation of the phrenic nerves. This has much greater sensitivity and specificity than volitional testing because it eliminates the confounding effects of patient effort and accessory muscle activity and allows each hemidiaphragm to be tested separately. Acute Neuralgic Amyotrophy
Our patient was diagnosed with acute neuralgic amyotrophy, which is also known as Parsonage-Turner syndrome. This is an acute brachial neuropathy, which causes pain and weakness of the shoulder and arm muscles. Phrenic nerve involvement, which may be unilateral or bilateral, occurs in fewer than 10% of cases. Typically, this disorder is self-limited, and there is complete recovery of upper limb function. Unfortunately, in patients with phrenic nerve involvement, recovery of diaphragm function is often slow and incomplete. n Author disclosures are available with the text of this article at www.atsjournals.org.
quantitative values in normal subjects. Muscle Nerve 2013;47: 884–889. Lahrmann H, Grisold W, Authier FJ, Zifko UA. Neuralgic amyotrophy with phrenic nerve involvement. Muscle Nerve 1999;22:437–442. Gottesman E, McCool FD. Ultrasound evaluation of the paralyzed diaphragm. Am J Respir Crit Care Med 1997;155:1570–1574. Nason LK, Walker CM, McNeeley MF, Burivong W, Fligner CL, Godwin JD. Imaging of the diaphragm: anatomy and function. Radiographics 2012;32:E51–E70. McCool FD, Tzelepis GE. Dysfunction of the diaphragm. N Engl J Med 2012;366:932–942.
1659
