Sleep Medicine Network
Home-Based Mechanical Ventilation & Neuromuscular Disease Section
The diaphragm plays a key a role in respiratory mechanics, particularly during the inspiratory cycle. Unilateral diaphragm paralysis (UDP) from traumatic, compressive, inflammatory, neuropathic, or iatrogenic phrenic nerve injury presents with exertional dyspnea or orthopnea, though more severe cases may present with hypoventilation, hypercapnia, and daytime fatigue. Diagnostic workup requires evaluation beyond radiography to determine if diaphragm elevation indicates paralysis with or without paradox. Severity of symptoms and degree of impairment do not consistently correlate with fluoroscopic/ultrasound findings during sniff maneuver, degree of restriction by spirometry, or supine forces. Compensatory accessory muscle use during daytime breathing can mask symptoms, and there can be severe nocturnal hypoventilation related to UDP.
Dr. Bethany L. Lussier
For symptomatic patients, treatment recommendations require understanding of the etiology and the likelihood of resolution vs progression, or association with progressive systemic conditions. Nighttime noninvasive ventilation (NIV) is considered useful since diaphragmatic weakness worsens in supine position, and hypoventilation during REM sleep without accessory muscle support is exacerbated (Steier J, et al. Eur Respir J. 2008;32[6]:1479). However, evidence for NIV in UDP remains low quality. NIV has been proposed for ventilatory support particularly when hypercapnia is present (Wiebel M, et al. Med Klin. 1995;90[1 Suppl 1]:20). For patients with progressive neuromuscular conditions, NIV with a backup rate is strongly recommended (Steindor M, et al. Respir Care. 2021;66[3]:410; Benditt JO. Respir Care. 2019;64[6]:679), but access to respiratory assist devices is limited for isolated UDP under current reimbursement algorithms without demonstrable hypercapnia or significant restrictive spirometry. The recent ONMAP recommendations calling for use of symptom severity to support initiating NIV if FVC>80% have not yet been adopted (Morgenthaler TI, et al. Chest. 2021;160[5]:e419). Without marked spirometric restriction or hypercapnia, most patients must fail conservative PAP therapy prior to escalation to NIV, and initiation of a backup rate remains debated. Nevertheless, the only large case series evaluating the predominant features of polysomnography in UDP suggests high incidence of central apneas, suggesting a backup rate may indeed be required independent of the need to support neuromuscular function (Singh M, et al. Can J Anesthesiology. 2021;68[7]:1064). Further assessment of the features, needs, and understanding of the natural trajectory is essential to guide approach to sleep-related hypoventilation in UDP.
Landy V. Luna Diaz
Section Fellow-in-Training
Bethany L. Lussier, MD, FCCP
Section Member-at-Large