Respiratory Support Modalities



Respiratory Support Modalities





Oxygen Delivery Devices

Donald Artes/Cathy Haut


Discussion



  • In order to provide supplemental oxygenation for a child with hypoxia or ineffective ventilation, a variety of oxygen delivery devices are available for use.


  • Indications include pathophysiologic hypoxemia, ineffective oxygenation related to neurologic illness or trauma, postanesthesia, and conditions resulting in myocardial ischemia.



Types



  • Low-flow devices: Provide oxygen at flow rates that are less than the patient’s inspiratory demand.



    • Nasal cannula: Delivers oxygen concentrations of approximately 24% to 44% at flow rates of 1 to 6 L/minute in adolescents and adults. A humidifier is used if the nasal cannula will be used at higher flows and for longer periods of time.



      • Flow rates as low as 250 mL (0.25 L/min) are used to deliver oxygen in infants.


      • Delivered oxygen concentrations are based on oxygen flow in relation to the patient’s minute volume (tidal volume × rate) and are therefore difficult to accurately predict in infants and young children.


    • Non-rebreather mask: Delivers oxygen concentrations of approximately 60% to 80% at flow rates of 8 to 10 L/minute.



      • Non-rebreather masks should be used when a child is in respiratory distress, especially when the etiology of the distress is unknown.


  • High-flow devices: Provide oxygen at flow rates that meet or exceed the patient’s inspiratory demand.



    • Venturi mask delivers oxygen concentrations at precisely 24%, 28%, 31%, 35%, 40%, and 50%. This is accomplished by interchanging one of six color-coded adapters.


    • Aerosol mask, in conjunction with a jet nebulizer, delivers oxygen concentrations of 28% to 100%. An air entrainment port can be opened and closed to adjust the delivered oxygen concentration. The smaller the opening of the entrainment port, the higher the oxygen concentration and the lower the total flow delivered to the patient (Table 4.1).


    • High-flow nasal cannulas: Specific systems that are designed to deliver heated humidified blended oxygen at higher flow rates that may meet or exceed the patient’s demand. See additional information under “Noninvasive Ventilation” that follows.


Noninvasive Ventilation


Discussion



  • Noninvasive ventilation plays a key role in the support of pediatric patients who once would have required intubation and mechanical ventilation.


  • Indications include the need for short-term ventilation, improvement in lung volumes and compliance, and a reduction in oxygen requirements.



Types



  • BiPAP (bilevel positive airway pressure)



    • Allows for the separate regulation of the inspiratory and expiratory positive pressure levels as well as the ability to set a mandatory minimal ventilatory rate.


  • CPAP (continuous positive air pressure)



    • Allows for spontaneous ventilation, which provides a constant positive airway pressure throughout the respiratory cycle.


  • High-flow nasal cannula



    • Gas delivery using a nasal cannula at gas temperatures near body temperature, allowing for highly saturated water vapor.


    • This highly saturated gas allows for increased flow rates without causing additional discomfort and irritation to the nasal mucosa.









TABLE 4.1 Oxygen Delivery













































Oxygen (%)


Approximate Air/O2 Ratio


Oxygen Flow Rate (L/minute)


Total Flow to Patient (L/minute)


24


25:1


4


104


28


10:1


4


44


30


8:1


6


54


35


5:1


8


48


40


3:1


10


40


45


2:1


12


36


50


1.7:1


12


33


Note: There may come a point at oxygen concentrations of greater than 50% when the total delivered flow may not meet the patient’s demand.



Assessment and Management



  • BiPAP/CPAP



    • Finding the appropriate mask fit for a pediatric patient can be challenging because of the variety of pediatric face shapes and sizes.


    • The key to successful noninvasive ventilation is a calm cooperative patient. Slowly increasing the patient’s airway pressures to allow for desensitization or the use of small doses of anxiolytics may be required.


    • Heavy doses of sedation and analgesia are contraindicated.


    • Periodic breaks off of the BIPAP/CPAP mask are necessary for proper skin assessment and to reduce the risk of skin breakdown.


    • Skin barrier devices can be applied between the skin and the mask to reduce the risk of skin breakdown.


    • Adequate patient airway protection is necessary to avoid the potential danger of aspiration.


    • Not indicated in patients with conditions that reduce the respiratory drive or in cases of respiratory failure.


    • Care should be taken with patients whose condition interferes with the seal of the mask, such as facial trauma, facial surgery, or the presence of a nasogastric tube.


  • High-flow nasal cannula



    • Flow rates are set at 1 to 8 L/minute for infants and young children, although flow rates can be as high as 40 L/minute in older children and adults.


    • Some sources have postulated that the rate of flow may deliver a level of positive pressure similar to CPAP.


  • Evaluating patient response



    • Improvement in arterial blood gases (e.g., increase in oxygenation and decrease in carbon dioxide levels).


    • Relief of dyspnea.


    • Improvement in the delivery of medications such as bronchodilators.


  • Diagnostic evaluation



    • Consider radiographic imaging while requiring oxygen.


Laryngeal Mask Airway

Brian Eells


Airway Management



Etiology/Types



  • Originally designed by Dr. Archie Brain.



    • LMA is LMA North America, now part of Teleflex.






      FIGURE 4.1 • Laryngeal Mask Airway. The original LMA design: a size 1 and size 6 LMA-Classic. The two bars over the airway aperture prevent the epiglottis from obstructing the LMA barrel.









      TABLE 4.2 Standard Sizing for LAAA



























      Mask Size


      Patient size


      1


      <5 kg neonate/infant


      1.5


      5-10 kg infant


      2


      10-20 kg infant/child


      2.5


      20-30 kg child


      3


      30-50 kg child/small adult


      4


      50-70 kg normal adult


      5


      70-100 kg large adult



    • Many LMA versions are available (e.g., Classic, Unique, ProSeal).


  • Other brands now exist (e.g., i-gel, Ambu Aura-i, Cook air-Q).


LMA Management



  • Intact airway reflexes preclude proper placement (e.g., biting, coughing, vomiting) (Table 4.2).



    • LMA size is estimated based on weight (See Table 4.2) and delete (see Table 4.2 at the end of the first bullet)


  • Cuff volumes are described by manufacturer.


  • Proper inflation usually causes slight upper movement of LMA and slight bulging of anterior neck.


  • Risk of ischemia if cuff is overinflated and/or systemic blood pressure is low.


  • May cause gastric insufflation if airway pressures exceed gastroesophageal opening pressure (e.g., ×15-25 cm H2O).






FIGURE 4.2 • Mallampati Scoring.


Difficult Airway

Brian Eells



Etiology/Types



  • Most assessments and guidelines are based on adult population (e.g., Mallampati classes, ASA’s “Practice guidelines for management of the difficult airway”) (Figure 4.2).


Associated Underlying Conditions



  • Congenital anomalies (e.g., Pierre Robin sequence, Treacher Collins syndrome)


  • Tumors (e.g., cystic hygroma)


  • Infection (e.g., retropharyngeal abscess, epiglottitis)


  • Oral/dental (e.g., severe overbite, wired teeth/jaw, high-arched palate)


  • Muscular (e.g., torticollis)


  • Skeletal (e.g., ankylosis, cervical fracture)


  • Trauma


Clinical Presentation



  • Predictors of difficult pediatric laryngoscopy



    • Age <1 year


    • ASA physical status 3 or 4


    • Modified Mallampati class 3 or 4


    • Oromaxillofacial disorder


    • Cardiac dysfunction


Evaluation

Jan 30, 2021 | Posted by in NURSING | Comments Off on Respiratory Support Modalities
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