What Is The Effect Of Opioid On Breathing?1
What Is Breathing?
Breathing is an inspiration (breath in) and expiration (breath out). We breathe about 18 to 22 times per minute. Breathing helps to inhale (breath in) oxygen and exhale (breath out) carbon dioxide.
What Is Hypoxia (Less Oxygen In Blood)?
Hypoxia is less concentration of oxygen in blood. Breathing less often than normal rate of breathing causes hypoxia. Complete stoppage of breathing also known as apnea results in severe hypoxia. Lack of oxygen (hypoxia) for 3 to 5 minutes causes loss of brain function and irreversible damage to heart and brain. Hypoxia is harmful and causes tissue damage.
Is The Rate Of Breathing Important?
Yes, rate of breathing is important to eliminate carbon dioxide and inhale oxygen. Air has oxygen and we breathe in oxygen with air each time we inhale (inspiration). Oxygen is consumed during carbohydrate and fat metabolism to generate heat and energy. Metabolism also creates carbon dioxide. Carbon dioxide is harmful to body and needs to be removed by exhaling (expiration). Opioid changes rate of breathing and amount of air inhaled.
What Are The Effects Of Opioid On The Rate Of Breathing?
Opioid reduces rate of breathing and also reduces volume of air inhaled by abruptly changing inspiration to expiration.2 Opioid influences mechanism of breathing.
What Is The Mechanism Of Breathing?3
Breathing is inspiration and expiration controlled by respiratory centers in brain, pons and medulla oblongata. Inspiration and expiration is accomplished by contractions of inspiratory and expiratory muscles. Inspiratory muscles contract during inspiration and relaxes during expiration. Similarly expiratory muscles contracts during expiration and relaxes during inspiration. Opioid suppresses respiratory centers.
What Are The Respiratory Centers?
Respiratory centers are located in brain, medulla oblongata and pons. Medulla oblongata and pons are tubular in shape and wider than spinal cord. Medulla Oblongata and pons lies between brain and spinal cord. Multiple respiratory centers controls inspiration and expiration.
There is a cortical respiratory center and 4 subcortical respiratory centers. Subcortical respiratory centers are as follows-
- Inspiratory Center
- Expiratory center
- Pneumotaxic center
- Apneustic Center
What Is The Role Of Respiratory Center?
- Inspiratory Center– located in medulla oblongata and causes inspiration.
- Expiratory Center– located in medulla oblongata and causes expiration.
- Pneumotaxic Center– located in pons, causes switch from inspiration to expiration and limits inspiration.
- Apneustic Center– located in pons, causes inspiration and ends expiration.
How Does Opioid Affect Respiratory Center?
Opioid suppresses respiratory center located at pons by activating mu opioid receptor resulting in slow breathing. Opioid action at mu receptors if not eliminated or reversed then patient may stop breathing (apnoea).1 Apnea or complete stoppage of breathing causes fatal outcome resulting in death. Opioid also suppresses cortical respiratory center.
What Is Cortical Respiratory Center?
Brain or cortical respiratory center lies in section of brain. Cortical respiratory center controls a sub-cortical respiratory center of pons and medulla oblongata. Cortical respiratory center is also suppressed by opioids. Suppression of brain (cortical) centers results in profound effects on lower (sub-cortical) respiratory centers. Effects of opioid action on lower respiratory center of pons and medulla oblongata is substantially increased when brain or cortical center is suppressed.2
Who Are The High-Risk Patients?
Following patients are high-risk patients-
- Obese patients
- Patients with abnormal airways- large neck
- Narrow airway passage in throat- Large tonsils and adenoids obstructs breathing space
- Diseases resulting in narrowing of peripheral airways-
- Congestive heart failure
- Terminally ill patients 4
- Medications when prescribed with opioids causes suppression of breathing centers-
- Muscle relaxants
- Family history of sleep apnea.
Is It Possible To Treat Opioid Induced Respiratory Depression?
Yes, opioid induced respiratory depression results in decreased rate (number) of breathing per minutes or apnea (complete stoppage of breathing). Opioid pills mostly causes decreased rate of breathing and effect is reversed with naloxone injection or sublingual pills. Opioid induced apnea is seen following intravenous opioids given for general anesthesia. Sudden development of apnea is observed after anesthesia. Apnea is reversed by intravenous injection of naloxone.1 Few patients may need life support therapy for few hours to days.
Which Patient Would Need Life Support Therapy?
Following patient may need life support therapy-
- Patient not responding to naloxone (opioid reversal medication.)
- Patient in apnea (not breathing) after anesthesia.
- Patient with severe hypoxia (less oxygen in blood)
- Apnea resulting in brain and heart damage.
What Is Life Support Therapy?
Life support involves following treatment-
- Intermittent positive pressure ventilation
- Medications to maintain normal blood pressure
- Medications to maintain normal heart function
Which Other Conditions Depresses Respiratory Centers?
Following conditions depresses respiratory centers-
- Brain Ischemia caused by vasoconstriction (narrowing of blood vessels),
- Brain trauma- brain injury like concussion, contusion and tear
- Brain tumor
- Brainstem damage
- Chronic opioid use: a risk factor for central sleep apnea and successful therapy with adaptive pressure support servo-ventilation.
Fahim A, Johnson AO.
J R Coll Physicians Edinb. 2012;42(4):314-6.
- Characterization of breathing patterns during patient-controlled opioid analgesia. Drummond GB, Bates A, Mann J, Arvind DK. Br J Anaesth. 2013 Dec;111(6):971-8.
- Non-analgesic effects of opioids: opioid-induced respiratory depression. Boom M, Niesters M, Sarton E, Aarts L, Smith TW, Dahan A. Curr Pharm Des. 2012;18(37):5994-6004.
- Effect of intraoral and subcutaneous morphine on dyspnea at rest in terminal patients with primary lung cancer or lung metastases. Gamborg H1, Riis J1, Christrup L2, Krantz T1. J Opioid Manag. 2013 Jul-Aug;9(4):269-74.