Neuromuscular Dyspnea Flashcards
What happens to the diaphragm’s workload when a person is supine?
The diaphragm shoulders a greater burden when supine.
What muscles provide force during active expiration?
Internal intercostals, rectus abdominis, transversus abdominis, external and internal oblique muscles.
What role do upper airway dilator muscles play in respiration?
Maintain patency and reduce resistance during respiration.
What is positional dyspnea?
Positional dyspnea includes orthopnea or trepopnea in supine or lateral recumbent positions respectively.
What central lesions can alter breathing patterns and cause dyspnea?
Brain or brainstem ischemia, demyelination, or malignancy.
The emergence of respiratory system weakness typically presents as?
Sleep-disordered breathing before diurnal dyspnea.
What can bulbar weakness impair in patients with NMDs?
Cough, airway patency, and secretion clearance.
What can reduced lung volumes in neuromuscular respiratory patients lead to in the lungs?
Alveolar collapse and atelectasis, particularly at the lung bases.
What is the consequence of non-ventilated alveoli (from NMDs) getting perfusion?
Non-ventilated alveoli receive perfusion without airflow, causing respiratory fatigue and hypercarbia.
What musculoskeletal change can reduce lung volumes in long-standing NMDs?
Scoliosis due to spinal rigidity.
How does scoliosis affect lung function in NMD patients?
Reduces lung volumes and compliance.
What does trepopnea indicate in patients with NMDs?
Asymmetric diaphragm involvement, preferring position with more affected diaphragm downwards.
What does orthopnea suggest in patients with NMDs?
Diaphragm weakness.
What syndrome can occur in patients with C4-C7 spinal cord lesions?
Platypnea-orthodeoxia syndrome. This is dyspnea and impaired O2 sat in seated position likely due to better abdominal support of respiration when supine.
Platypnea is a rare medical condition where an individual has worse dyspnea sitting or standing that improves when laying down. It’s often caused by an intracardiac shunt like PFO. It can also be caused by pulmonary embolus, and pulmonary AVM. Think Platypnea=PPP (Pfo, Pe, Pulmonay avm)
Symptoms of nocturnal hypoventilation
Nighttime awakenings, daytime sleepiness, and morning headaches.
What does weakness of neck flexion correlate with?
Reduced forced vital capacity (FVC).
What respiratory parameters does the single-count breath test assess/correlate with?
It correlates with forced vital capacity (FVC) and negative inspiratory force (NIF). Counts below 25 indicate abnormal respiratory function (count on exhalation 2 (unclear if 1 or 2) counts/second).
What FVC drop percentage in the supine position (compared to upright) indicates diaphragmatic weakness?
> 25% drop in FVC is 90% specific and 79% sensitive for diaphragmatic weakness.
What does MIP test?
Combined strength of inspiratory muscles.
What MIP value is 86% sensitive for predicting nocturnal hypoxia?
Values <60 cmH2O.
What MEP value suggests an ineffective cough?
Values <60 cmH2O suggest an ineffective cough.
What does Cough Peak Flow (CPF) assess?
CPF assesses the maximum expiratory flow during a cough.
What are cough spikes?
Brief surges in expiratory flow exceeding normal maximum levels.
What is the risk associated with reduced cough spikes in ALS patients?
Increased risk of mortality.
In muscular dystrophies what does a high cough peak flow indicate in relation to respiratory infections?
Higher CPF (Cough Peak Flow) decreases risk of respiratory failure during respiratory infections.
What MEP value is associated with identifying an ineffective cough?
MEP <60 cmH2O.
What CPF value identifies an ineffective cough?
CPF <270 L/min identifies an ineffective cough.
What CPF value suggests compromised airway clearance?
CPF <160 L/min suggests compromised airway clearance.
What does the fluoroscopic sniff test assess?
Diaphragm excursion with forced inspiration during fluoroscopy.
For what condition is the fluoroscopic sniff test most useful?
Unilateral diaphragmatic weakness.
What is the sensitivity/specificity of ultrasound for detecting diaphragmatic respiratory weakness?
93% sensitive, 100% specific.
What is the specificity of ultrasound for detecting diaphragmatic respiratory weakness?
100% specific.
What typically precedes daytime hypoventilation in NMDs?
Nocturnal hypercapnia, desaturation, and sleep disruption.
SpO2 criteria for NIV initiation
SpO2 ≤88% for ≥5 min during ≥2 h of nocturnal recording time.
What PaCO2 level on an ABG indicates NIV initiation and reimbursement by Medicare/Medicaid?
PaCO2 ≥45 mmHg.
What are the PFT criteria for NIV initiation and reimbursement by Medicare/Medicaid?
MIP <60 cmH2O or FVC <50% of predicted.
When should NIV be initiated according to FVC levels?
Initiate NIV if FVC <80% with symptoms or FVC <50% without symptoms.
What medications are helpful for secretion management in NMD patients?
Anticholinergic medications are helpful for secretion management.
What medications help with viscous secretions?
Guaifenesin (expectorant), N-acetylcysteine (mucolytic and antioxidant), nebulized bronchodilators.
What respiratory issue can Dextromethorphan-quinidine use for PSA also help?
It can also improve excessive secretions. Dextromethorphan is an anti-tussive but somehow the article states that it may improve excess secretions. I double checked the article. I looked at a different article and it said the same thing for ALS patients
What devices assist with cough and secretion clearance in NMD patients?
Mechanical insufflator-exsufflator and oscillatory vest devices.
What is the benefit of using devices like the mechanical insufflator-exsufflator in NMD patients?
They reduce pulmonary infections.
What are motor neuron diseases that can cause neuromuscular dyspnea?
ALS, Post polio syndrome, SMA
What are muscle diseases that can cause neuromuscular dyspnea?
Frequent: Pompe’s, mitochondrial, LGMD (esp 2C-2F= sarcoglycanopathies, 2I= FKRP), Titanopathies, ILD from inflammatory myopathies
Less common: Myophosphorylase deficiency, Myotonic Dystrophy, FSH, sporadic late onset Nemaline myopathy, critical illness myopathy, immune mediated necrotizing myopathy.
What are our peripheral nerve disorders that can cause neuromuscular dyspnea?
Common: GBS, phrenic neuropathy.
Less common: Miller Fisher syndrome, CIDP (especially nodopathy), poems, MMN, CMT2 associated with TRIM mutations, Neuralgic Amyotrophy
What are neuromuscular junction disorders that are associated with neuromuscular dyspnea?
Frequent: MG, botulism
Less frequent: LEMS, congenital myasthenic syndromes
Per the AANEM lecture in 2024 about neuromuscular disease diseases and respiratory dysfunction, what are the four main criteria for instituting noninvasive ventilation?
- Peak inspiratory pressure <-60cm H20
- FVC < 50% predicted
- Spo2< 88% for over 5 min on nocturnal recording
- Awake pco2>44mmHg
Per the AANEM lecture on neuromuscular disorders with respiratory dysfunction, what FVC threshold for non-invasive ventilation in ALS patients led to better survival?
Instituting non-invasive ventilation when a FVC is greater than 80% predicted
