Use appropriate oxygen delivery devices to achieve the necessary fraction of inspired oxygen (Fio2)
Use appropriate oxygen delivery devices to achieve the necessary fraction of inspired oxygen (Fio2): Excerpt from Avoiding Common Pediatric Errors
Author:
Renée Roberts, MD
What to Do - Make a Decision
Whenassessingapatientwhoishypoxic,monitorstomeasurepulseoximetry,
electrocardiogram, and blood pressure should be placed while providing
supplemental oxygen. The mental status should be observed and the chest
should be auscultated to ensure that the airway is patent, that the lungs are
clear, and that spontaneous respiratory efforts are adequate. Quickly check
areas to rule out include obstruction either via collapse of the soft tissues
or via a foreign object (such as a mucous plug or vomitus), stridor, and
bronchospasm. These reasons for hypoxiashould beruled outandaddressed
before significant improvement is seen with supplemental oxygen.
Incertainpatientpopulations,thebenefitsofsupplementaloxygenmust
be weighed with the potential risks. Neonates, especially expremature infants younger than 44 weeks' postconceptual age, are at risk of developing
retrolental fibroplasia (otherwise known as retinopathy of prematurity). It is
suggested that PaO2 does not rise above 80 torr in this population. Supplemental oxygen in patients with certain congenital heart lesions (hypoplastic
left heart syndrome, single ventricle physiologies, ventricular septal defect,
patent ductus arteriosus) will cause an increase in alveolar oxygen tension
and may compromise the balance between pulmonary and systemic flow.
Patients taking certain chemotherapeutic drugs, such as bleomycin, may be
prone to oxygen toxicity and pulmonary fibrosis.
Nasal cannulae fall under the category of low-flow systems. They are
used to provide a low concentration of oxygen to the patient. The actual FIO2
delivered depends on oxygen flow, nasopharyngeal volume, and inspiratory
flow. FIO2 roughly increases 1% to 2% above 21% per liter of oxygen flow
in a normally breathing adult. So, at oxygen flows of 3 to 4 L/min, nasal
cannulas can deliver an FIO2 of 30% to 35%. An FIO2 of 40% to 50% can
be attained with flows of >10 L/min. In infants, FIO2 of 0.35, 0.45, 0.6,
and 0.68, with flows of 0.25, 0.5, 0.75, and 1 L/min, respectively, can be
attained.
Although nasal cannulae have the advantage of allowing feeding and
increased mobility while delivering supplemental oxygen, they do dry out
mucous membranes and are poorly tolerated by patients at high flows. In
fact, if higher flows are needed to achieve a higher FIO2, alternative methods
of oxygen delivery should be considered. "Simple" or oxygen masks without
a reservoir bag are suited for patients who require higher levels of oxygen
for short periods. The body of the mask serves as the reservoir or both the
inspired oxygen and expired carbon dioxide (CO2). The required minimum
flow needs to be checked with the manufacturer so that rebreathing of CO2
is prevented. The FIO2 delivered is variable; it may range from 0.3 to 0.6 at
5 to 10 L/min.
When higher levels of FIO2 are needed, the partial rebreather mask and
the nonrebreathing mask can be used. Both have a reservoir bag at the end
of the mask but the nonrebreather uses valves between the bag and mask and
at least one of the mask's exhalation ports. Typical minimum flows range
from 10 to 15 L/min. Partial rebreathers can attain an FIO2 between 0.4
and 0.6, whereas nonrebreathers are used to deliver FIO2 >0.6. Both masks
are useful for patients with normal spontaneous minute ventilation, such as
trauma patients and victims of mild carbon monoxide poisoning. As with
all the mask methods of supplemental oxygen delivery, the maximum FIO2
attainable has not been well established in infants and children.
Do not leave dyspneic patients on nonrebreather masks. These patients
are candidates for fixed-performance, high-flow oxygen systems. These include anesthesia bags or bag-mask-valve systems and air entrapment "Venturi" masks. For practical purposes, bag-mask-valve systems are often used
in resuscitation situations. The "Venturi" mask system comes in fixed and
adjustable FIO2 models, with minimum flow instructions. An FIO2 of 1.0 is
attainable depending on flow.
Many infants and children cannot tolerate nasal cannulae or masks.
Oxygen hoods are an alternative. FIO2 can vary from 0.21 to 1.0 and cannot
be easily controlled because a constant flow of gas is needed through and out
of the system to remove CO2. Flows of >7 L/min are required to wash out
expired CO2. The hoodis useful for short-term oxygen therapy for relatively
inactive infants.
Supplemental oxygen will improve oxygenation. However, it will not
improve hypercarbia. If the patient is hypoventilating, dyspneic, or shows an
altered mental status that does not improve with oxygen, obtain an arterial
blood gas if time permits. Use your clinical judgment instead of waiting for
lab results if additional measures are needed. More supportive measures,
such as the insertion of a nasal or oral airway, continuous positive airway
pressure, bilevel positive airway pressure, positive pressure ventilation, or
intubation may be required.
Suggested Reading
MyersTR,AmericanAssociationforRespiratoryCare(AARC).AARCClinicalPracticeGuideline:selectionofanoxygendeliverydeviceforneonatalandpediatricpatients—2002revision
& update. Respir Care. 2002;47(6):707–716.
Book Source Details
- Book Title: Avoiding Common Pediatric Errors
- Author(s): Anthony D Slonim MD, DrPH; Lisa Marcucci MD
- Year of Publication: 2008
- Copyright Details: Avoiding Common Pediatric Errors, Copyright © 2008 Lippincott Williams & Wilkins.
More About Premature Birth
More Medical Textbooks Online about Premature Birth
Review other book chapters online related to Premature Birth:
Copyright notice for book excerpts: Copyright © 2008 Lippincott Williams & Wilkins. All rights reserved.
|
|
More About This Book:
Title: Avoiding Common Pediatric Errors
Authors: Anthony D Slonim MD, DrPH; Lisa Marcucci MD
Publisher: Lippincott Williams & Wilkins
Copyright: 2008
ISBN: 0-7817-7489-6
|
|
» Next page: Premature Adrenarche (The 5-Minute Pediatric Consult)
Rate This Website
What do you think about the features of this website?
Take our user survey and have your say:
Website User Survey
Medical Tools & Articles:
Next articles:
Tools & Services:
Medical Articles:
Forums & Message Boards
- Ask or answer a question at the Boards:
