The relationship between hypoxemia and dyspnoea (which is a sensation of uncomfortable, difficult or laboured breathing, or the experience of breathing discomfort) can be quite complex . Hypoxemia per se does not necessarily elicit dyspnoea in healthy condition, despite an increased ventilatory drive and an increased minute ventilation.
The maximal sustainable ventilation for an average adult varies according to the time frame. The maximal voluntary ventilation (MVV) for 15 seconds is 130 L/min, and 75% of MVV can be maintained for 15 minutes at 100 L/min, whilst 50% of MVV can be maintained for many hours at 65 L/min. Furthermore, 30 L/min can be maintained for an almost indefinite period of time, which does not necessarily elicit dyspnoea. The ventilatory response to hypoxemia can be blunted by a number of factors such as age and diabetes, both imposing a 50% reduction in ventilatory response to hypoxemia. Similarly, fever causes a right shift in the dissociation curve which results in a lower SaO2 with preserved PaO2 (no chemoreceptor response to the low SaO2) . Hypoxemia and concomitant hypocapnia favour maintaining an acceptable SaO2 despite low PaO2. The most common reasons for dyspnoea include hypercapnia, increased work of breathing (reduced compliance), and neuromechanical dissociation. In fact, the aetiology of dyspnoea is often multifactorial and hypoxemia can be a contributing factor .
- Parshall MB, et al. Am J Respir Crit Care Med. 2012 Feb 15;185(4):435-52.
- Tobin MJ, et al. Am J Respir Crit Care Med. 2020 Jun 1;201(11):1319-1320.
- Frausing Hansen E. Dyspnea and hypoxemia – what is the correlation (including silent hypoxemia). Nordic Lung Congress 2022, 01–03 June, Copenhagen, Denmark.
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Table of Contents: NLC 2022
NLC 2022 Highlights Podcast
Respiratory Disease and Physical Activity
Physical activity improves asthma control
Tailored exercise needed for COPD patients
Exercise training for IPF patients is feasible but access needs to be improved
Respiratory Disease and Reproduction
Asthma increases risks around delivery
PRO-ART study: unravelling the link between asthma and subfertility
Early-onset and uncontrolled asthma: strong association with recurrent pregnancy loss
Palliative Care in Respiratory Diseases
Advance care planning
Biologics in Asthma
Severe asthma in the spotlights
Common comorbidities in severe asthma
Treatable Traits in Obstructive Airway Diseases
Targeting treatable traits allows a personalised approach to management of (severe) asthma
Challenges in Upper Airway Diseases
Exercise-induced laryngeal obstruction (EILO) is often misdiagnosed
The role of biologics in CRSwNP
The ULANC Group: working together in CRSwNP/asthma
Interstitial Lung Diseases (ILD)
Rheumatoid arthritis-associated ILD
Thoracic ultrasound: a new diagnostic imaging tool in RA-ILD?
Update on treatment of fibrotic ILD
Lung Cancer Screening in the Nordics
Lung cancer screening in Denmark
Points of interest for radiologists screening for lung cancer
E-cigarettes impose detrimental effects on health
Effects of passive vaping in COPD patients
Vaping amongst adolescents: an alarming trend
Tuberculosis and Sarcoidosis
New antigens in sarcoidosis
Detection of latent TB infection key to preventing the spread of the disease
New antigens in sarcoidosis
Sarcoidosis guidelines update
Fatigue syndrome in sarcoidosis