Understanding Pre-Oxygenation and Desaturation Time

Pre-oxygenation is a crucial step in ensuring adequate oxygenation during medical procedures. In a 70-kg man, the functional residual capacity (FRC) is approximately 2.5 liters. If pre-oxygenated adequately, all of the FRC will be 100% oxygen, and oxygen extraction per minute is 250 ml. This means that the patient will have 10 minutes of adequate oxygenation in the absence of ventilation before desaturation occurs.

However, if only 21% (room air) was in the FRC, the patient would only have 2 minutes before they started to desaturate. It is important to note that the oxygen extraction rate is 250 ml per minute in a 70-kg male. A person who has been adequately preoxygenated will not start to desaturate until double this time period, which is 10 minutes.

Therefore, if the patient is oxygenated on room air only, the correct answer for desaturation time would be 2.5 minutes. However, if the patient has been adequately preoxygenated, they will desaturate well before 25 minutes is reached. Understanding pre-oxygenation and desaturation time is crucial in ensuring patient safety during medical procedures.

Diagnosis of Subarachnoid Haemorrhage

Subarachnoid haemorrhage can be diagnosed with a high degree of accuracy through an urgent CT scan, which can confirm the condition in 95% of patients. In most cases, a lumbar puncture is not necessary unless the patient’s medical history suggests the need for one and the CT scan results are normal. If a bloody tap is suspected, the number of red blood cells should decrease with each successive sample. If an LP is performed six hours after the onset of symptoms, the supernatant fluid should be examined for xanthochromia after centrifugation.

Anesthesia Grading Score for Patient Risk

The American Society of Anesthesiologists developed a grading score in 1963 to assess patient risk during surgery. The score ranges from one to five and uses Roman numerals to indicate the severity of a patient’s systemic disease. Patients without systemic disease are classified as grade I, while those with mild to moderate systemic disease that does not limit their activities are classified as grade II. Patients with severe systemic disease that causes functional limitations are classified as grade III, and those with severe systemic disease that poses a constant threat to life are classified as grade IV. Additionally, the letter E is added to indicate emergency surgery. Finally, patients who are moribund and unlikely to survive more than 24 hours with or without surgery are classified as grade V. This grading system helps anesthesiologists determine the appropriate level of care and monitoring needed during surgery.

Halothane Hepatitis and Precautions

Halothane hepatitis is a condition that can range from minor liver function issues to severe liver failure. It occurs when liver damage appears within 28 days of exposure to halothane, after excluding other known causes of liver disease. About 75% of patients with halothane hepatitis have antibodies that react to halothane-altered antigens. Therefore, it is important to take precautions when using halothane.

Halothane should be avoided if there has been a previous exposure within three months, if there is a known adverse reaction to halothane, if there is a family history of adverse reactions, or if there is pre-existing liver disease. These precautions can help prevent the occurrence of halothane hepatitis and ensure the safety of patients. It is important to carefully consider the use of halothane and take necessary measures to avoid any potential harm.

Understanding Heat Loss During Surgery: The Role of Radiation, Convection, Conduction, Evaporation, and Respiration

During surgery, the body can lose heat through various mechanisms. Radiation, which accounts for 40% of heat loss, depends on factors such as body temperature and the environment. To combat this, patients are covered with warming methods like the Bair Hugger™. Convection, or air movement, contributes to 30% of heat loss, while conduction (5%) occurs through contact with the operating table and surrounding air. Evaporation (15%) is higher if the abdomen is open, and humidity is kept at 50% in the theatre to reduce it. Finally, respiration accounts for 10% of heat loss. Understanding these mechanisms can help healthcare professionals better manage patient temperature during surgery.

Choosing the Correct Endotracheal Tube Size for an 8-Year-Old Child

When it comes to intubating an 8-year-old child, choosing the correct endotracheal tube (ETT) size is crucial. Cuffed ETTs are now considered safe for use in children, but not in neonates. To calculate the appropriate size of a cuffed ETT, use the formula (Child’s age/4) + 3.5. For an 8-year-old child, the correct size of a cuffed ETT would be 5.5 mm. If an uncuffed tube is preferred, use the formula (Child’s age/4) + 4 to calculate the tube size, which would be 6.0 mm for an 8-year-old child. It is important to note that using a cuffed tube offers more protection from aspiration. Avoid using a 4.5 mm cuffed ETT, as it is too small for an 8-year-old child.

Suxamethonium: A Depolarising Muscle Relaxant

Suxamethonium is a type of muscle relaxant that causes muscular fasciculations after being injected intravenously. It quickly induces neuromuscular paralysis, but recovery is spontaneous once it is metabolized by the enzyme pseudo or plasma cholinesterase, which is produced in the liver. However, certain pesticides and drugs, such as ecothiopate iodide, can inhibit cholinesterase activity and prolong the effects of suxamethonium. Additionally, reduced levels of plasma cholinesterase can be caused by liver disease, malnutrition, and pregnancy, while genetically determined abnormal enzymes can also lead to a prolonged action of suxamethonium. It’s important to note that neostigmine and other anticholinesterase drugs do not serve as reversal agents and can actually potentiate the neuromuscular block caused by suxamethonium.

When administering suxamethonium, it’s important to be aware that bradycardia (a slow heart rate) may occur in children after the first dose and in adults after repeated doses. Premedication with atropine should be considered to prevent this. It’s also crucial to note that suxamethonium is a potent trigger of both anaphylaxis and malignant hyperpyrexia, with the incidence of anaphylaxis being highest with rocuronium, atracurium, and suxamethonium.

Post-Operative Foot Drop Caused by Prolonged Pressure on Common Peroneal Nerve

Prolonged pressure on the common peroneal nerve during anaesthesia is a well-known cause of post-operative foot drop. It is important to ensure that patients are adequately padded on the fibula head when positioning them under general or regional anaesthesia for extended periods of time. While a central neurological cause is unlikely to cause such well-defined peripheral nerve lesions, it is essential to take precautions to prevent nerve damage during surgery.

Treatment for post-operative foot drop is typically conservative, and the transient neuropraxia can often pass. However, in some cases, this may result in permanent injury. It is crucial to monitor patients closely after surgery and provide appropriate care to prevent further complications. By taking preventative measures and providing proper post-operative care, healthcare professionals can help reduce the risk of post-operative foot drop and other nerve injuries.

Common Complications of Suxamethonium Administration

Suxamethonium is a commonly used muscle relaxant during anesthesia. However, it can lead to several complications, including malignant hyperthermia, raised intraocular pressure, anaphylaxis, prolonged paralysis, and hyperkalemia.

Malignant hyperthermia is a genetic myopathy that causes a hypermetabolic state, leading to circulatory collapse and death. Treatment involves recognition, removal of stimuli, continuation of anesthesia with intravenous agents, cooling, and administration of dantrolene.

Raised intraocular pressure and intracranial pressure can occur after suxamethonium administration, but this is only relevant to patients with ocular and intracranial diseases.

Anaphylaxis is a severe allergic reaction that can occur after suxamethonium administration. Diagnosis is based on signs and symptoms.

Prolonged paralysis can occur in patients with abnormal pseudocholinesterase level or function, which is generally due to inherited genetic alleles. Diagnosis is by blood test.

Hyperkalemia can occur after suxamethonium administration, especially in patients with severe muscle damage or recent burns. Diagnosis does not require a muscle biopsy.

Managing Malignant Hyperpyrexia: An Anaesthetic Emergency

Malignant hyperpyrexia is a life-threatening anaesthetic emergency triggered by inhalational anaesthetics and muscle relaxants in genetically susceptible individuals. It causes a hypermetabolic state, leading to increased CO2 production, oxygen consumption, heat production, metabolic and respiratory acidosis, hyperkalaemia, activation of the sympathetic nervous system, and disseminated intravascular coagulation.

Early signs include a rise in end-tidal CO2, rigid muscles, tachycardia, and tachypnoea. Treatment involves discontinuation of the triggering agent, rapid administration of dantrolene, active cooling, and treatment of hyperkalaemia. Dantrolene inhibits calcium release from the sarcoplasmic reticulum and reverses the hypermetabolic state.

It is important to inform the surgeon and stop the operation. Once the initial reaction is controlled, the patient will require transfer to the ICU and monitoring for 24-48 hours.

In contrast, giving more muscle relaxant or antibiotics is not recommended. Active management and stabilisation of the patient should precede discussion with the ICU. Malignant hyperpyrexia requires prompt recognition and management to prevent serious complications and death.

Coagulase-Negative Staphylococci: Commonly Isolated Bacteria in Clinical Microbiology Laboratories

Coagulase-negative Staphylococci are frequently encountered in clinical microbiology laboratories. These bacteria, including Staphylococcus epidermidis, are susceptible to novobiocin and have become a significant cause of infection, especially in patients who are hospitalized and have foreign bodies implanted or those who have weakened immune systems.

The prevalence of coagulase-negative Staphylococci in clinical settings highlights the importance of identifying and treating these bacteria promptly. With the rise of antibiotic resistance, it is crucial to monitor the susceptibility patterns of these organisms to ensure effective treatment. By the characteristics and potential risks associated with coagulase-negative Staphylococci, healthcare providers can take appropriate measures to prevent and manage infections caused by these bacteria.

Respiratory Alkalosis: Causes and Effects

Respiratory alkalosis is a condition that occurs when a person hyperventilates, leading to a decrease in the partial pressure of carbon dioxide (PaCO2) in the alveoli. This decrease in PaCO2 causes an increase in the ratio of bicarbonate concentration (HCO3) to PaCO2, which in turn increases the pH of the blood. As a result, the patient may appear to have an alkalosis with a high pH of 7.5, low pCO2, and normal PO2. However, the body tries to compensate for this by lowering the bicarbonate concentration. This condition can be caused by a variety of factors, including anxiety, fever, hypoxia, and pulmonary disease. It can also be a side effect of certain medications or a result of high altitude. Treatment for respiratory alkalosis depends on the underlying cause and may include addressing the underlying condition, breathing techniques, or medication.

Considerations for Anesthesia in a Patient with Medical History

When administering anesthesia to a patient, it is important to take into account their medical history and any potential risk factors. Here are some considerations for a patient with specific medical history:

Anesthesia Considerations for a Patient with Medical History

– Prolonged Paralysis: If a patient has a family or personal history of prolonged paralysis after receiving suxamethonium, it may be necessary to consider using a different muscle relaxant during surgery.
– Asthma: Patients with asthma are at a higher risk of airway irritation during endotracheal intubation. However, in some surgeries, intubation is necessary and careful monitoring is required.
– Blood Pressure: While a blood pressure of 110/75 may be normal for a 26-year-old male, it is important to review the patient’s past blood pressure measurements to ensure that this is the case. Induction agents with profound cardiovascular effects should be avoided if the patient is in shock.
– Family History of Cardiac Arrest: If a patient has a family history of cardiac arrest, it is important to review the facts of the case and consider any independent risk factors that may have contributed to the event.
– Penicillin Allergy: While anesthesia agents do not contain penicillin, it is important to document any allergies in case the patient requires antibiotics after surgery.

Medication Management in Perioperative Period

Phenelzine and tranylcypromine are monoamine oxidase inhibitors that need to be discontinued at least two weeks before elective surgery due to their potential life-threatening interactions with pethidine and indirect sympathomimetics. Additionally, they can prolong the action of suxamethonium by decreasing the concentration of plasma cholinesterase. Carbamazepine, an anticonvulsant, should be continued throughout the perioperative period. Gliclazide, a short-acting oral hypoglycemic, can be taken if the surgery’s anticipated duration is short.

Lisinopril, an angiotensin-converting enzyme inhibitor (ACEi), and digoxin, a cardiac glycoside, should be continued pre-operatively. Morphine sulfate tablets should also be continued pre-operatively, and a morphine infusion (PCA) should be considered for postoperative analgesia. Pyridostigmine is used in the management of myasthenia gravis and should be continued before minor surgery. However, if perioperative muscle relaxation is required, omitting one or more doses of pyridostigmine would allow a reduction in the dose of the muscle relaxant. Proper medication management in the perioperative period is crucial to ensure patient safety and optimal surgical outcomes.

Treatment for Mild Hypokalaemia

Mild hypokalaemia can be treated with oral supplementation. If a patient is able to eat, intravenous fluids are unnecessary. It is best to advise the patient to take oral supplements for a few days. Foods such as tomatoes and bananas contain high levels of potassium and could be offered as well. However, it is important to note that the maximum concentration of potassium that can be given via a peripheral line is 40 mmol/L. It is also important to avoid loop diuretics as they can make the patient’s potassium levels even lower. As long as the patient is asymptomatic and able to eat, mild hypokalaemia can be easily treated with oral supplementation.

Characteristics of Aortic Stenosis

Aortic stenosis is a condition where the aortic valve becomes narrowed, causing the heart to work harder to pump blood out to the body. Despite this increased workload, the apex beat in aortic stenosis is not displaced but has a heaving character. Additionally, the pulse is typically of small volume and slow rising. The second heart sound may be inaudible or paradoxically split.

It is important to note that the intensity of the murmur is not a reliable indicator of the severity of the disease. As the cardiac output is reduced with more severe disease, the murmur may become less intense. However, the murmur tends to become longer as the disease progresses, due to the longer ejection time needed. These characteristics can help healthcare professionals diagnose and monitor aortic stenosis in patients.

Common Inducing Anaesthetic Agents and Their Uses

Propofol, etomidate, ketamine, midazolam, and thiopental are all commonly used inducing anaesthetic agents with varying properties and uses.

Propofol is the drug of choice for RSII procedures in normotensive individuals without obvious cardiovascular pathology. It has amnesic, anxiolytic, anticonvulsant, and muscle relaxant properties, but no analgesic effects.

Etomidate provides haemodynamic stability without histamine activity and minimal analgesic effects. It is used in RSI procedures in patients with raised intracranial pressure and cardiovascular conditions, often in combination with fentanyl.

Ketamine is a non-competitive glutamate N-methyl-D-aspartate (NMDA) receptor blocker that produces dissociative anaesthesia. It can be used for induction of anaesthesia in patients with hypotension, status asthmaticus, and shock, but is avoided in hypertensive patients due to relative contraindications.

Midazolam is a benzodiazepine with anticonvulsive, muscle relaxant, and anaesthetic actions. At higher doses or in combination with other opioids, it induces significant cardiovascular and respiratory depression.

Thiopental is administered intravenously as an inducing anaesthetic agent or as a short-acting anaesthetic. It is also used as an anticonvulsant agent and to decrease intracranial pressure in neurosurgical procedures.

Managing a ‘Can’t Intubate’ Scenario in a Patient with Neck of Femur Fracture

In a ‘can’t intubate’ scenario with a patient who has a neck of femur fracture, the priority is delivering oxygen. If attempts at intubation have been difficult and the patient is desaturating, the Difficult Airway Society recommends attempting ventilation with a laryngeal mask airway (LMA) as a temporary measure. If this fails and the patient continues to desaturate, an emergency cricothyrotomy is advised for urgent oxygen delivery. Using a videolaryngoscope to secure a definitive airway is not recommended if oxygenation is a priority. Similarly, attempting a fibreoptic intubation or using a long blade for further attempts at intubation can cause damage and swelling in the airway, leading to laryngospasm. Waking the patient up is also not advisable in this emergency situation, as neck of femur fractures have a high mortality rate if left untreated.

Medications for Pain Relief in Various Conditions

Pinaverium is a medication that is commonly used to reduce the duration of pain in individuals with irritable bowel syndrome (IBS). On the other hand, carbamazepine is used to treat neuropathic pain that is associated with malignancy, diabetes, and other disorders. Clodronate is another medication that is used to treat malignant bone pain and hypercalcaemia by inhibiting osteoclastic bone resorption.

Corticosteroids are also used to treat pain caused by central nervous system tumours. These medications work by reducing inflammation and oedema, which in turn relieves the pain caused by neural compression. Nifedipine is another medication that is used to relieve painful oesophageal spasm and tenesmus that is associated with gastrointestinal tumours.

Lastly, oxybutynin is a medication that is used to relieve painful bladder spasm. Overall, these medications are used to treat pain in various conditions and can provide relief to individuals who are experiencing discomfort.

Neuropathic Pain and Treatment Options

Neuropathic pain is a chronic condition that affects neuronal membrane excitability and often results in allodynia, hyperalgesia, and hyperpathia. Unlike nociceptive pain, neuropathic pain is less responsive to opioids and can be more difficult to treat. To manage this type of pain, coanalgesics such as antidepressants, anticonvulsants, and antiarrhythmics are commonly prescribed. Anticonvulsants are typically administered at similar doses and schedules as in the treatment of epilepsy. The analgesic response to mexiletine can be predicted by evaluating the improvement in pain after an intravenous lidocaine infusion. Amitriptyline, on the other hand, has a faster analgesic response than its antidepressant effect, with pain relief occurring within a week of treatment. Overall, managing neuropathic pain requires a multifaceted approach that may involve a combination of medications and other therapies.

Cannabinoids and Their Effects

Cannabinoids are compounds found in the resin of cannabis sativa, with 9-tetrahydrocannabinol (9-THC) being the most important active component. However, the oral bioavailability of THC, whether in pure form or as part of marijuana, is low and highly variable, with effects taking anywhere from 0.5 to 3 hours to occur. Smoking marijuana also does not significantly increase bioavailability, with rates rarely exceeding 10-20%.

Interestingly, the analgesic effects of cannabinoids can be blocked by naloxone and other opioid receptor antagonists. Additionally, synthetic cannabinoids have been found to reduce inflammation caused by arachidonic acid by inhibiting eicosanoid production. Overall, the effects and limitations of cannabinoids is important for both medical and recreational use.

Comparison of Different Anesthetic Agents

Propofol is a short-acting anesthetic agent with an elimination half-life of four hours. It is commonly used for day case procedures and sedation in intensive care units. On the other hand, etomidate is no longer preferred due to its side effects such as postoperative nausea and vomiting, venous thrombosis, and interference with glucocorticoid production. Ketamine, a phencyclidine derivative, can cause hallucinations and nightmares. Methohexitone may lead to involuntary muscular movement and epileptiform activity on an EEG. Lastly, thiopentone has the longest elimination half-life of 12 hours, which can cause a prolonged hangover effect.

In summary, different anesthetic agents have their own advantages and disadvantages. It is important to choose the appropriate agent based on the patient’s condition and the type of procedure being performed.

Common Adverse Reactions to Medications: Symptoms and Treatments

Malignant Hyperthermia, Neuroleptic Malignant Syndrome, Serotonin Syndrome, Acute Dystonia, and Meningitis are all potential adverse reactions to medications.

Malignant Hyperthermia is a rare condition that can occur after exposure to general anaesthetics or muscle relaxants. Symptoms include a sudden increase in temperature, acidosis, hypercapnia, and widespread skeletal muscle rigidity. Treatment involves dantrolene and supportive care such as cooling and correction of acidosis.

Neuroleptic Malignant Syndrome is a rare idiosyncratic reaction that can occur as a response to taking high-potency anti-psychotic medication. Symptoms include hyperthermia, fluctuating consciousness, rigidity, tachycardia, labile blood pressure, and autonomic dysfunction. Treatment involves discontinuing the medication and supportive management such as fluids and cooling. Dantrolene or bromocriptine may also be used.

Serotonin Syndrome occurs when a patient takes multiple doses, an overdose, or a combination of certain medications. Symptoms include confusion, agitation, hyperreflexia, shivering, sweating, tremor, fever, and ataxia. Treatment involves stopping the drugs and providing supportive care.

Acute Dystonia presents with spasm of various muscle groups and is a side-effect of anti-psychotic medication. It can occur in the first few hours of administration of anti-psychotic medication. It is also seen with the antiemetic metoclopramide where it can cause an oculogyric crisis. It is not usually associated with anaesthesia.

Meningitis is not a complication of anaesthesia or muscle relaxants.

Importance of Adequate Hydration in Monitoring Organ Perfusion

Hourly urine output is a reliable indicator of organ perfusion, which is directly linked to hydration levels. However, if there is a urological obstruction, this measure may not be accurate. While a trend in central venous pressure (CVP) can be helpful, a single reading is not a reliable indicator of hydration status. Late signs of hypovolemia include dry mucous membranes and hypotension. Therefore, it is crucial to maintain adequate hydration levels to ensure proper organ perfusion and prevent hypovolemia.

Medical Interventions for a Post-Operative Patient with Reduced Consciousness

When dealing with a post-operative patient with reduced consciousness, it is important to rule out any reversible causes before administering any medical interventions. In the case of opiate toxicity, administering naloxone, an opiate antidote, can reverse the effects of the opiates. However, if the patient’s reduced Glasgow Coma Scale score and lack of respiratory effort are not caused by hypoglycemia, giving intravenous glucose is not necessary. It is also important to consider the patient’s age and wait a little longer to rule out any reversible causes. Administering a second dose of muscle relaxant reversal is unlikely to help if the patient has adequate contraction on train of four testing. Lastly, before re-sedating the patient for a CT head, it is necessary to rule out any reversible causes such as opiate toxicity.

Resuscitation Council (UK) Recommendations for Choking Emergencies

When faced with a choking emergency, the Resuscitation Council (UK) recommends a specific course of action. If the patient is able to cough effectively, encourage them to do so. If not, but they are conscious, try five back blows followed by five abdominal thrusts (Heimlich manoeuvre) and repeat if necessary. However, if the patient becomes unconscious, begin CPR immediately. It is important to note that a finger sweep is no longer recommended as it can push the obstruction further into the airway. Additionally, high flow oxygen is necessary for breathing, but nasopharyngeal airways will not help in this situation. Removal with forceps is also not recommended as it can be hazardous. If the Heimlich manoeuvre fails, a cricothyroidotomy should be considered. While this procedure is recommended in the US and UK, it is not encouraged in some countries like Australia due to the risk of internal injury from over-vigorous use.

Types of Laryngoscopes

Laryngoscopes are medical instruments used to visualize the larynx and facilitate intubation. There are several types of laryngoscopes, each with its own unique features. The Miller, Oxford, and Wisconsin laryngoscopes have straight blades, while the Macintosh and McCoy laryngoscopes have curved blades. The McCoy laryngoscope is typically used for difficult intubations, as its blade tip is hinged and can be operated by a lever mechanism on the handle. Overall, the choice of laryngoscope depends on the individual patient and the specific needs of the intubation procedure.

Prognostic Indicators for Hypoxic Brain Injury Patients

Hypoxic brain injury patients require ancillary tests to aid in determining their prognosis. Bilaterally absent somatosensory evoked responses (SSEPs) at 24–72 hours and complete generalised suppression of electroencephalographic (EEG) waves on day three are reliable indicators of poor prognosis. Absent pupillary or corneal reflexes at three days after cardiac arrest, along with the absence of motor response, is also a better prognostic marker. However, in the absence of either one of these factors, the prognosis should be evaluated using results from ancillary tests (SSEP/EEG). Extensor motor response on day three, despite the absence of motor response, is a reliable indicator for poor prognosis. Myoclonic status epilepticus (MSE) – bilateral and synchronous myoclonus of the face, limbs and axial skeleton – has been studied as a reliable marker for poor prognosis in these patients, even in the presence of brainstem and motor responses. However, it should not be considered in isolation as a prognostic indicator. It is important to note that the reliability of these indicators may be affected by factors such as noise interferences, hypothermia, and drugs given during resuscitation.

Management of Anaphylaxis: Medications and Dosages

Anaphylaxis is a severe and potentially life-threatening allergic reaction that requires immediate treatment. The first-line management for anaphylaxis is the administration of adrenaline, also known as epinephrine. The dosage of adrenaline varies depending on the age of the patient. For adults, 0.5 ml of 1 : 1000 adrenaline should be given intramuscularly (im), and the dose can be repeated after 5 minutes if there is no response. In children, the dosage ranges from 150 to 500 micrograms depending on age.

Intravenous (iv) administration of adrenaline is not recommended at a concentration of 1 : 1000. However, iv adrenaline can be administered at a concentration of 1 : 10 000 by an anaesthetist, titrated according to effect. An adrenaline infusion may be necessary for cardiovascular support of the patient.

Chlorpheniramine and hydrocortisone are also part of the treatment for anaphylaxis, but adrenaline takes priority. The dosages of these drugs vary depending on the age of the patient and can be given either im or through a slow iv injection.

It is important to note that anaphylaxis is a medical emergency, and prompt treatment with the appropriate medications is crucial for a positive outcome.

Calculating Oxygen Remaining in a Cylinder

When using an oxygen cylinder, it’s important to know how much oxygen is left to avoid running out. To calculate the remaining oxygen, you need to know the cylinder size and the flow rate. For example, if a cylinder has 340 litres of oxygen and is flowing at 10 litres per minute, how much oxygen is left after 6 minutes?

In 12 minutes, 120 litres of oxygen would have already been used (12 min × 10 l/min = 120 l). To find out how much oxygen is left, subtract the amount used from the total amount: 340 – 120 = 220 litres. Then, divide the remaining gas by the flow rate (10 l/min) to get the remaining time: 220/10 = 22 minutes.

It’s important to note that if the flow rate is higher or the cylinder size is smaller, the remaining time will be shorter. Therefore, it’s crucial to monitor the oxygen levels and have a backup cylinder on hand in case of emergency.