Last reviewed: 22 May 2021
Last updated: 16 Oct 2019



History and exam

Other diagnostic factors

  • male sex
  • dyspnoea
  • daytime sleepiness
  • morning headache
  • impaired cough
  • repeated lower respiratory tract infections
  • BMI ≥30 kg/m²
  • increased pulmonary component of second heart sound (P2)
  • lower-extremity oedema
  • right-sided third heart sound (S3 gallop)
  • left-sided fourth heart sound (S4 gallop)

Risk factors

  • body mass index (BMI) ≥30 kg/m²
  • restrictive thoracic disorders
  • central nervous system disorders
  • obstructive airway disease

Diagnostic investigations

1st investigations to order

  • arterial blood gas
  • serum bicarbonate
  • pulse oximetry
  • Hct

Investigations to consider

  • pulmonary function tests
  • respiratory muscle strength
  • CXR
  • polysomnogram
  • echocardiogram
  • TSH
  • PHOX2B gene

Treatment algorithm


Professor of Medicine

Division of Pulmonary and Critical Care Medicine

Temple University School of Medicine




SK is an author of a number of references cited in this topic.

Professor Samuel Krachman would like to gratefully acknowledge Dr Gerard Criner, a previous contributor to this topic. GC declares that he has no competing interests.

Peer reviewersVIEW ALL

Consultant Physician

Royal Brompton Hospital

Honorary Senior Lecturer

National Heart and Lung Institute

Imperial College

Department of Respiratory Medicine




MH declares that he has no competing interests.

Associate Professor of Medicine

Physiology and Neuroscience

New York University School of Medicine

New York



KIB declares that he has no competing interests.

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