B is for Breathing (part 1 of 4)

18 June, 2010 by: colinparker

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Hello again… This recording session turned into such a marathon, we had to split it into 4 parts!
B is for Breathing

This first part covers:

  • respiratory physiology basics
  • neonatal breathing and apnoeas
  • ALTE’s
  • assessing the work of breathing

Please join us again in 2 weeks for Breathing, part 2, in which we divulge some clinical pearls which you may find helpful in distinguishing different causes of respiratory embarassment or tachypnoea.  For example, how to distinguish bronchiolitis from congestive cardiac failure in an infant, or remembering the non-respiratory causes of rapid breathing.

As always, we welcome your comments. Don’t be shy!

Brief synopsis of this PEMcast:

CP: Intro & disclaimer

CP: Respiratory Physiology

Respiratory centre in medulla controls rate & depth of respiration, input from chemoreceptors, lung, cortex.
Effected via nerves C3,4,5, diaphragm & resp muscles (intercostal, abdominal, accessory) – coordinated activity.
Central respiratory drive (Ondine’s curse)
Chemoreceptors central (pH), peripheral in carotid & aortic bodies (Po2, PCO2)
Receptors in lung sensitive to stretch, irritants, vessel engorgement
Lung maturity:  in utero development
Alveoli 20 million at birth, 300 million age 8yrs (?multiply or enlarge after 8yrs)
large surface area: 2.8 m2 at birth, 32 m2 aged 8
Infants: diffusing capacity 1/3 to 1/2 that of adults (even correcting for surface area)
Diffusion: Surfactant – Epithelial cell – Interstitium – Endothelial Cell – Plasma – Red Cell

Patent airway

Normal RR:

<1                   30-40
1-2                  25-35
2-5                  25-30
5-12                  20-25
<12                  15-20

Tidal Volume 5-7mL/kg

Minute Volume is volume of gas (exhaled) per minute (dep on RR and Vt)
Alveolar minute volume – takes into account dead space –  ie amount of air available for gas exchange -CO2 varies in proportion

WOB usually 1% of metabolic rate

Anatomic considerations: Airway differences (Upper), narrow distal airway first 5 yrs, Soft chest wall

KB: Neonates – periodic breathing

DA: Apnoeas esp neonatal – causes

CP: ALTE

National Institutes of Health definition: Some combination of:

  • Apnea
  • Colour change (blue/pale/red)
  • Muscle tone (floppy)
  • (choking/gagging)
  • AND Frightening to the observer

Cause can be identified in up to 50% of cases (GOR, pertussis, LRTI, sepsis (UTI esp), seizure; metabolic, cardiac, factitious, NAI)

Hx, examination (tests?)
[eMedicine article = thorough]
Admit for observation
Apnea monitors…
Not near-miss SIDS

KB: WOB assessment: effort & efficacy, signs of increased WOB

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Comments

2 Responses to “B is for Breathing (part 1 of 4)”
  1. Kawi gurl says:

    Great blog! much appreciated.

    Sent from my iPhone 4G

  2. Colin says:

    The ranges of normal respiratory rate produced by APLS and PALS are apparently misleading, according to this recent article in the Lancet:

    Fleming S, Thompson M, Stevens R, Heneghan C, Plüddemann A, Maconochie I,
    Tarassenko L, Mant D. Normal ranges of heart rate and respiratory rate in
    children from birth to 18 years of age: a systematic review of observational
    studies. Lancet. 2011 Mar 14. [Epub ahead of print] PubMed PMID: 21411136.

    http://www.ncbi.nlm.nih.gov/pubmed/21411136

    These researchers from Oxford, UK and Oregon, USA have analysed data from 69 original studies, to produce a new evidence-based set of centile charts for normal respiratory rate and normal heart rate ranges according to age.

    Be sure to get the webappendix supplement; page 13 of the document contains a table of cutoff values for various centiles, by age range.

    I wonder whether this will result in a change to the established cutoffs used by international bodies such as APLS, and how long this will take?

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