Medical gas therapy

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Medical gas therapy
Other namesTherapeutic gas
Specialty pulmonology
gaseous signaling molecules

Medical gas therapy is a treatment involving the administration of various gases. It has been used in medicine since the use of oxygen therapy. [1] Most of these gases are drugs, including oxygen. [2] Many other gases, collectively known as factitious airs, were explored for medicinal value in the late eighteenth century. In addition to oxygen, medical gases include nitric oxide (NO), and helium-O2 mixtures (Heliox). Careful considerations and close monitoring needed when medical gases are in use. For the purpose of this article only gas mixtures are described.

Contents

Gas mixtures therapies

Nitric oxide

Nitric oxide is a substance that our body produces in its every cell and in its every organ. It has a number of functions. It take part in vasodilation, platelet inhibition, immune regulation, enzyme regulation, and neurotransmission.

Inhaled nitric oxide is a gas that is inhaled. [1] It was initially described in 1987 as an "endothelial-derived relaxing factor" and has since been used to treat pulmonary disorders. [3] It works by relaxing smooth muscle to widen (dilate) blood vessels, especially in the lungs. [1] Inhaled nitric oxide selects only pulmonary smooth muscles. There will be no effect or minimal effect of inhaled nitric oxide on atelectatic or fluid-filled lung. [3] It improves oxygenation and decreases pulmonary hypertension. [4] Nitric oxide is used together with a mechanical ventilator to treat respiratory failure in premature infants. [1] In adults nitric oxide can be used in treating pulmonary hypertension with acute respiratory distress syndrome. Thanks to the possible clinical successful outcomes of nitric oxide treatment patients can avoid need for extracorporeal membrane oxygenation treatment. The U.S. Food and Drug Administration has been approved the use of nitric oxide in term and near-term (greater than 34 weeks' gestation age) neonates with hypoxic respiratory failure with clinical or echocardiographic evidence of pulmonary hypertension. [5]

Contraindications

Nitric oxide must not be used in neonates who depend on right-to-left shunting of blood.

Dosing of nitric oxide

Dose needed to achieve desired effect but avoid toxicity and adverse effects in neonates and adults is relatively low. Usually it is 5-20 ppm (parts per million). [6] Regular arterial blood gas tests needed to assess the response to the therapy and signs of toxicity. Improvement in partial pressure of oxygen (PO2) and oxygen saturation would be indication of positive response to the nitric oxide therapy. If there is an evidence that nitric oxide works the same dose would be used till the hypoxemia and pulmonary hypertension resolved. When the hypoxemia and pulmonary hypertension resolved titration or slowly weaning of the nitric oxide initiates. Abrupt discontinuation of nitric oxide may lead to compromised oxygenation and pulmonary hypertension may rebound. [7]

Robert F. Furchgott, PhD Drfurchgott.jpg
Robert F. Furchgott, PhD

Side effects of the nitric oxide therapy

Methemoglobins level in the blood increases with the use of nitric oxide. Methemoglobin is abnormal form of molecule which can not carry oxygen. Methemoglobin turns blood brown. Other medications can produce methemoglobin too. Monitoring of methemoglobin needed when nitric oxide is in use.

Nitric oxide with oxygen (O2) in combination produces another by-product chemical compound nitrogen dioxide (NO2). The higher the oxygen concentration and nitric oxide therapy duration and lower ventilator flow rate the higher amount of NO2 will be produced. NO2 is toxic and its level should always be monitored in nitric oxide therapies. High level of NO2 can lead to cell damage, hemorrhage, pulmonary edema.

Bill Clinton meets the 1998 Nobel Prize Winners in the White House. From left to right: Ferid Murad, Medicine; Louis Ignarro, Medicine; Daniel Tsui, Physics; Robert Furchgott, Medicine; Bill Clinton, The President; John Pople, Chemistry; Horst L. Stormer, Physics; Robert Laughlin, Physics Clinton&1998NobelLaureates.jpg
Bill Clinton meets the 1998 Nobel Prize Winners in the White House. From left to right: Ferid Murad, Medicine; Louis Ignarro, Medicine; Daniel Tsui, Physics; Robert Furchgott, Medicine; Bill Clinton, The President; John Pople, Chemistry; Horst L. Störmer, Physics; Robert Laughlin, Physics

Use of nitric oxide in patients with left heart failure or congestive heart failure may lead to pulmonary edema or worsen pulmonary edema.

Nobel Prize for Nitric oxide discoveries

Three US scientist - Robert F. Furchgott, PhD, Louis J. Ignarro, PhD, and Ferid Murad, MD, PhD won Nobel Prize in Physiology and Medicine for their discovery of nitric oxide role in cardiovascular and nervous systems in 1998. [8] Even though the nitric oxide effects on the body known for more than 25 years the clinical use is still in a development.

Helium and oxygen

In medicine, Heliox generally refers to a mixture of 21% O2 (the same as air) and 79% He, although other combinations are available.

Heliox generates less airway resistance than air and thereby requires less mechanical energy to ventilate the lungs. [9] "Work of Breathing" is reduced. It does this by two mechanisms:

  1. increased tendency to laminar flow
  2. reduced resistance in turbulent flow

The dry air on the Earth we inhale consists of 78.8% nitrogen, 20.95% oxygen and 0.93% argon. Heliox therapy is substitution of nitrogen with helium. Helium itself has no pharmacological value, it does not react in the body. Its only purpose is to make the flow less turbulent and help oxygen to get into the lungs. Less turbulent flow requires less work to breathe.

Helium and Heliox properties

Helium (He) is colorless, odorless, tasteless, and inert noble gas. Helium is second lightest gas after hydrogen. [10]

Heliox has a similar viscosity to air but a significantly lower density (0.5 g/L versus 1.2 5g/L at STP). Flow of gas through the airways comprises laminar flow, transitional flow and turbulent flow. The tendency for each type of flow is described by the Reynolds number. Heliox's low density produces a lower Reynolds number and hence higher probability of laminar flow for any given airway. Laminar flow tends to generate less resistance than turbulent flow.

In the small airways where flow is laminar, resistance is proportional to gas viscosity and is not related to density and so heliox has little effect. The Hagen–Poiseuille equation describes laminar resistance. In the large airways where flow is turbulent, resistance is proportional to density, so Heliox has a significant effect.

Heliox has been used medically since the early 1930s. It was the mainstay of treatment in acute asthma before the advent of bronchodilators. Currently, heliox is mainly used in conditions of large airway narrowing (upper airway obstruction from tumors or foreign bodies and vocal cord dysfunction). There is also some use of heliox in conditions of the medium airways (croup, asthma and chronic obstructive pulmonary disease).

Patients with these conditions may develop a range of symptoms including dyspnea (breathlessness), hypoxemia (below-normal oxygen content in the arterial blood) and eventually a weakening of the respiratory muscles due to exhaustion, which can lead to respiratory failure and require intubation and mechanical ventilation. Heliox may reduce all these effects, making it easier for the patient to breathe. [11] Heliox has also found utility in the weaning of patients off mechanical ventilation, and in the nebulization of inhalable drugs, particularly for the elderly. [12] Research has also indicated advantages in using helium–oxygen mixtures in delivery of anaesthesia. [13]

Heliox side effect

Heliox side effect is that inhaled helium change voice. Speech will sound high pitched. This effect is caused by low density gas passing through the vocal cords. The effect is reversible.

Related Research Articles

<span class="mw-page-title-main">Hypoxia (medicine)</span> Medical condition of lack of oxygen in the tissues

Hypoxia is a condition in which the body or a region of the body is deprived of adequate oxygen supply at the tissue level. Hypoxia may be classified as either generalized, affecting the whole body, or local, affecting a region of the body. Although hypoxia is often a pathological condition, variations in arterial oxygen concentrations can be part of the normal physiology, for example, during strenuous physical exercise.

<span class="mw-page-title-main">Meconium aspiration syndrome</span> Medical condition affecting newborn infants

Meconium aspiration syndrome (MAS) also known as neonatal aspiration of meconium is a medical condition affecting newborn infants. It describes the spectrum of disorders and pathophysiology of newborns born in meconium-stained amniotic fluid (MSAF) and have meconium within their lungs. Therefore, MAS has a wide range of severity depending on what conditions and complications develop after parturition. Furthermore, the pathophysiology of MAS is multifactorial and extremely complex which is why it is the leading cause of morbidity and mortality in term infants.

Heliox is a breathing gas mixture of helium (He) and oxygen (O2). It is used as a medical treatment for patients with difficulty breathing because this mixture generates less resistance than atmospheric air when passing through the airways of the lungs, and thus requires less effort by a patient to breathe in and out of the lungs. It is also used as a breathing gas diluent for deep ambient pressure diving as it is not narcotic at high pressure, and for its low work of breathing.

<span class="mw-page-title-main">Respiratory failure</span> Inadequate gas exchange by the respiratory system

Respiratory failure results from inadequate gas exchange by the respiratory system, meaning that the arterial oxygen, carbon dioxide, or both cannot be kept at normal levels. A drop in the oxygen carried in the blood is known as hypoxemia; a rise in arterial carbon dioxide levels is called hypercapnia. Respiratory failure is classified as either Type 1 or Type 2, based on whether there is a high carbon dioxide level, and can be acute or chronic. In clinical trials, the definition of respiratory failure usually includes increased respiratory rate, abnormal blood gases, and evidence of increased work of breathing. Respiratory failure causes an altered state of consciousness due to ischemia in the brain.

<span class="mw-page-title-main">Acute respiratory distress syndrome</span> Human disease

Acute respiratory distress syndrome (ARDS) is a type of respiratory failure characterized by rapid onset of widespread inflammation in the lungs. Symptoms include shortness of breath (dyspnea), rapid breathing (tachypnea), and bluish skin coloration (cyanosis). For those who survive, a decreased quality of life is common.

<span class="mw-page-title-main">Oxygen therapy</span> Use of oxygen as a medical treatment

Oxygen therapy, also referred to as supplemental oxygen, is the use of oxygen as medical treatment. Supplemental oxygen can also refer to the use of oxygen enriched air at altitude. Acute indications for therapy include hypoxemia, carbon monoxide toxicity and cluster headache. It may also be prophylactically given to maintain blood oxygen levels during the induction of anesthesia. Oxygen therapy is often useful in chronic hypoxemia caused by conditions such as severe COPD or cystic fibrosis. Oxygen can be delivered via nasal cannula, face mask, or endotracheal intubation at normal atmospheric pressure, or in a hyperbaric chamber. It can also be given through bypassing the airway, such as in ECMO therapy.

<span class="mw-page-title-main">Pulmonary hypertension</span> Increased blood pressure in lung arteries

Pulmonary hypertension is a condition of increased blood pressure in the arteries of the lungs. Symptoms include shortness of breath, fainting, tiredness, chest pain, swelling of the legs, and a fast heartbeat. The condition may make it difficult to exercise. Onset is typically gradual. According to the definition at the 6th World Symposium of Pulmonary Hypertension in 2018, a patient is deemed to have pulmonary hypertension if the pulmonary mean arterial pressure is greater than 20mmHg at rest, revised down from a purely arbitrary 25mmHg, and pulmonary vascular resistance (PVR) greater than 3 Wood units.

<span class="mw-page-title-main">Blue baby syndrome</span> Two situations that lead to cyanosis in infants

Blue baby syndrome can refer to conditions that cause cyanosis, or blueness of the skin, in babies as a result of low oxygen levels in the blood. This term has traditionally been applied to cyanosis as a result of:.

  1. Cyanotic heart disease, which is a category of congenital heart defect that results in low levels of oxygen in the blood. This can be caused by either reduced blood flow to the lungs or mixing of oxygenated and deoxygenated blood.
  2. Methemoglobinemia, which is a disease defined by high levels of methemoglobin in the blood. Increased levels of methemoglobin prevent oxygen from being released into the tissues and result in hypoxemia.
<span class="mw-page-title-main">Generalized hypoxia</span> Medical condition of oxygen deprivation

Generalized hypoxia is a medical condition in which the tissues of the body are deprived of the necessary levels of oxygen due to an insufficient supply of oxygen, which may be due to the composition or pressure of the breathing gas, decreased lung ventilation, or respiratory disease, any of which may cause a lower than normal oxygen content in the arterial blood, and consequently a reduced supply of oxygen to all tissues perfused by the arterial blood. This usage is in contradistinction to localized hypoxia, in which only an associated group of tissues, usually with a common blood supply, are affected, usually due to an insufficient or reduced blood supply to those tissues. Generalized hypoxia is also used as a synonym for hypoxic hypoxia This is not to be confused with hypoxemia, which refers to low levels of oxygen in the blood, although the two conditions often occur simultaneously, since a decrease in blood oxygen typically corresponds to a decrease in oxygen in the surrounding tissue. However, hypoxia may be present without hypoxemia, and vice versa, as in the case of infarction. Several other classes of medical hypoxia exist.

<span class="mw-page-title-main">Nasal cannula</span> Medical device to deliver supplemental oxygen

The nasal cannula (NC) is a device used to deliver supplemental oxygen or increased airflow to a patient or person in need of respiratory help. This device consists of a lightweight tube which on one end splits into two prongs which are placed in the nostrils curving toward the sinuses behind the nose, and from which a mixture of air and oxygen flows. The other end of the tube is connected to an oxygen supply such as a portable oxygen generator, or a wall connection in a hospital via a flowmeter. The cannula is generally attached to the patient by way of the tube hooking around the patient's ears or by an elastic headband, and the prongs curve toward the paranasal sinuses. The earliest, and most widely used form of adult nasal cannula carries 1–3 litres of oxygen per minute.

Stridor is a high-pitched extra-thoracic breath sound resulting from turbulent air flow in the larynx or lower in the bronchial tree. It is different from a stertor which is a noise originating in the pharynx.

<span class="mw-page-title-main">Hypoxemia</span> Abnormally low level of oxygen in the blood

Hypoxemia is an abnormally low level of oxygen in the blood. More specifically, it is oxygen deficiency in arterial blood. Hypoxemia has many causes, and often causes hypoxia as the blood is not supplying enough oxygen to the tissues of the body.

In respiratory physiology, airway resistance is the resistance of the respiratory tract to airflow during inhalation and exhalation. Airway resistance can be measured using plethysmography.

Persistent fetal circulation is a condition caused by a failure in the systemic circulation and pulmonary circulation to convert from the antenatal circulation pattern to the "normal" pattern. Infants experience a high mean arterial pulmonary artery pressure and a high afterload at the right ventricle. This means that the heart is working against higher pressures, which makes it more difficult for the heart to pump blood.

<span class="mw-page-title-main">Exhaled nitric oxide</span> Breath test for respiratory inflammation

In medicine, exhaled nitric oxide (eNO) can be measured in a breath test for asthma and other respiratory conditions characterized by airway inflammation. Nitric oxide (NO) is a gaseous molecule produced by certain cell types in an inflammatory response. The fraction of exhaled NO (FENO) is a promising biomarker for the diagnosis, follow-up and as a guide to therapy in adults and children with asthma. The breath test has recently become available in many well-equipped hospitals in developed countries, although its exact role remains unclear.

Biological functions of nitric oxide are roles that nitric oxide plays within biology.

<span class="mw-page-title-main">Heated humidified high-flow therapy</span> Respiratory support method

Heated humidified high-flow therapy, often simply called high flow therapy, is a type of respiratory support that delivers a flow of medical gas to a patient of up to 60 liters per minute and 100% oxygen through a large bore or high flow nasal cannula. Primarily studied in neonates, it has also been found effective in some adults to treat hypoxemia and work of breathing issues. The key components of it are a gas blender, heated humidifier, heated circuit, and cannula.

In the respiratory system, ventilation/perfusion (V/Q) mismatch refers to the pathological discrepancy between ventilation (V) and perfusion (Q) resulting in an abnormal ventilation/perfusion (V/Q) ratio. Ventilation is a measure of the amount of inhaled air that reaches the alveoli, while perfusion is a measure of the amount of deoxygenated blood that reaches the alveoli through the capillary beds. Under normal conditions, ventilation-perfusion coupling keeps ventilation (V) at approximately 4 L/min and normal perfusion (Q) at approximately 5 L/min. Thus, at rest, a normal V/Q ratio is 0.8. Any deviation from this value is considered a V/Q mismatch. Maintenance of the V/Q ratio is crucial for preservation of effective pulmonary gas exchange and maintenance of oxygenation levels. A mismatch can contribute to hypoxemia and often signifies the presence or worsening of an underlying pulmonary condition.

<span class="mw-page-title-main">Nitrogen dioxide poisoning</span> Medical condition

Nitrogen dioxide poisoning is the illness resulting from the toxic effect of nitrogen dioxide. It usually occurs after the inhalation of the gas beyond the threshold limit value. Nitrogen dioxide is reddish-brown with a very harsh smell at high concentrations, at lower concentrations it is colorless but may still have a harsh odour. Nitrogen dioxide poisoning depends on the duration, frequency, and intensity of exposure.

Work of breathing (WOB) is the energy expended to inhale and exhale a breathing gas. It is usually expressed as work per unit volume, for example, joules/litre, or as a work rate (power), such as joules/min or equivalent units, as it is not particularly useful without a reference to volume or time. It can be calculated in terms of the pulmonary pressure multiplied by the change in pulmonary volume, or in terms of the oxygen consumption attributable to breathing.

References

  1. 1 2 3 4 Moncada S (1999). "Nitric oxide: discovery and impact on clinical medicine". J R Soc Med. 92 (4): 164–9. doi:10.1177/014107689909200402. PMC   1297136 . PMID   10450191.
  2. ↑ Kacmarek, Robert M. Fundamentals of Respiratory Care (11 ed.). Elsevier. p. 905.
  3. 1 2 Gentile, Michael A. (1 September 2011). "Inhaled Medical Gases: More to Breathe Than Oxygen". Respiratory Care. 56 (9): 1341–1359. doi: 10.4187/respcare.01442 . ISSN   0020-1324. PMID   21944684. S2CID   34231129.
  4. ↑ Kacmarek, Robert M. Fundamentals of Respiratory Care.
  5. ↑ Kacmarec, Robert. Fundamentls of Respiratory Care. Elsevier.
  6. ↑ Kacmarek, Robert M. Fundamentals of Respiratory Care. Elsevier.
  7. ↑ Kacmarek, Robert. Fundamentals of the Respiratory Care. Elsevier.
  8. ↑ SoRelle, Ruth (December 1998). "Nobel Prize Awarded to Scientists for Nitric Oxide Discoveries". Circulation. 98 (22): 2365–2366. doi:10.1161/01.CIR.98.22.2365. ISSN   0009-7322.
  9. ↑ "Heliox21". Linde Gas Therapeutics. 27 January 2009. Retrieved 13 April 2011.
  10. ↑ Walsh, Brian K. Neonatal and Pediatric Respiratory Care (4th ed.). Elsevier.
  11. ↑ BOC Medical. "Heliox data sheet" (PDF).
  12. ↑ Lee DL, Hsu CW, Lee H, Chang HW, Huang YC (September 2005). "Beneficial effects of albuterol therapy driven by heliox versus by oxygen in severe asthma exacerbation". Acadrmic Emergency Medicine. 12 (9): 820–7. doi: 10.1197/j.aem.2005.04.020 . PMID   16141015 . Retrieved 2008-07-08.
  13. ↑ Buczkowski PW, Fombon FN, Russell WC, Thompson JP (November 2005). "Effects of helium on high frequency jet ventilation in model of airway stenosis". British Journal of Anaesthesiology. 95 (5): 701–5. doi: 10.1093/bja/aei229 . PMID   16143576.
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