The impact of these kind of respiratory problems on patient outcomes and healthcare costs is relevant as it is associated with high morbidity and mortality2

In this article we discuss the signs of respiratory distress, and interventions to keep your sedated patient safe. The terms respiratory depression, distress or failure will be used interchangeably to refer to inadequate pulmonary gas exchange.

What is respiratory distress or failure?

Respiratory failure occurs when pulmonary gas exchange is sufficiently impaired to cause hypoxemia with or without hypercarbia. It is defined as a partial pressure of oxygen PaO2 < 8 kPa (60 mmHg) and divided into two types according to the partial pressure of carbon dioxide PaCO2 level.3,4,5

  Type I Respiratory Failure (acute hypoxemic) Type II Respiratory failure (ventilatory failure)
Partial pressure of oxygen PaO2 < 8 kPa < 8 kPa
Partial pressure of carbon dioxide PaCO2 Normal or Low > 6 kPa
Common causes   
  • Depression of respiratory centre (e.g. opioids)
  • Reduced respiratory effort
  • Failure to compensate for an increase in dead space and/or CO2 production
  • Chronic bronchitis and emphysema
  • Chest wall deformities
  • Respiratory muscle weakness

Why does respiratory distress or failure happen during sedation?

In the perioperative setting, sedative drugs often cause respiratory impairment related to Central Nervous System depression, airway obstruction, decreased respiratory effort and respiratory muscle weakness. Certain factors related to the sedation technique, surgical procedure and patient variability, predispose patients to higher likelihood of respiratory complications:

Factors related to sedation technique

  • Dose of sedatives
  • Single vs Multiple drugs
  • Bolus vs Titration to Effect

Factors related to surgery or intervention

  • Elective vs Emergency procedure
  • Open vs Minimally invasive procedure
  • Upper abdominal incision
  • Longer procedures

Factors related to patient variability

  • Age
  • Frailty
  • ASA score
  • Pulmonary/respiratory problems
  • Smoking

Signs of respiratory distress or failure

Early identification of the signs or respiratory distress, and adequate intervention, can help prevent further deterioration, morbidity and mortality

A diagnosis of respiratory distress is made on the presence of:6

  • Signs of CO2 retention or absent expired CO2 (noticed in the capnography trace)
  • Use of accessory muscles of respiration 
  • Changes in respiratory rate
  • Abnormal or absent breathing sounds
  • Reduced SpO2

Intervention in respiratory distress or failure

Assessing risk factors prior to the procedure can help prevent perioperative respiratory failure

Choosing adequate sedation techniques, reducing doses of sedative drugs, titrating to effect, timing and choice of intervention are modifiable factors which can be managed.

Despite careful assessment and preparation, respiratory failure can still occur. Intraoperative monitoring with capnography, pulse oximetry and careful clinical observation allow early detection of respiratory problems.

Once respiratory impairment has been identified, early and adequate intervention plays an important role in patient outcomes:2,7,8

  1. Manually and verbally stimulate the patient
  2. Suction  (if there are signs of airway obstruction)
  3. Ensure airway patency (head tilt chin lift; jaw thrust; guedel)
  4. Ensure ventilation and oxygenation  (support with bag valve mask if required)
  5. Treatment of specific cause/underlying condition
  6. Continue monitoring vital signs
  7. Ask for help


Respiratory depression is one of the most common complications in sedation practice, mainly associated with the administration of sedative drugs. Careful preoperative assessment, attentive intraoperative monitoring, early identification of signs of respiratory distress or failure and adequate intervention as explained above can prevent morbidity and mortality.

About the author

My name is Andreia Trigo RN BSc MSc, I am a nurse consultant with over a decade of experience in anaesthesia, sedation and pain management.

This involves patient care, as well as lecturing at post grad level on these topics, presenting at conferences and co-developing a very successful sedation course at SedateUK. My passion for creating safer environments for patients and professionals led me to collaborate with Medtronic and share my knowledge and expertise with our professional community.


The content of this article is written by a blogger with whom Medtronic has a relationship. However, the contents represent the personal objective views, comments and techniques of the blogger and are not statements from Medtronic. To the extent this material might contain images of patients or any material where a copyright is held by a third party, all necessary written permissions from the patient or copyright holder, as applicable, with respect to use, distribution or copying of such images or copyrighted materials has been obtained by the blogger.

  • 1. Academy of Medical Royal Colleges (2013) Safe Sedation Practice for Healthcare procedures: standards and guidance. Available at

  • 2. Denise Battaglini et al (2019) Perioperative anaesthetic management of patients with or at risk of acute distress respiratory syndrome undergoing emergency surgery. BMC Anesthesiology volume 19, Article number: 153 available at

  • 3. Ata Murat Kaynar (2018) Respiratory Failure. Available at

  • 4. Anaesthesia UK (2009) Respiratory Failure. Available at

  • 5. Puneet Katyal et al Pathophysiology of Respiratory Failure and use of mechanical ventilation. Available at

  • 6. Vanessa Moll (2018) Overview of Respiratory Arrest. Available at

  • 7. Daniel E Becker et al (2007) Management of Complications During Moderate and Deep Sedation: Respiratory and Cardiovascular Considerations. Anesth Prog. 2007 Summer; 54(2): 59–69. Available at

  • 8. Jeffrey B. Gross et al (2002) Practice Guidelines for Sedation and Analgesia by Non-Anesthesiologists. Anesthesiology 4 2002, Vol.96, 1004-1017 Available at