Respiratory Distress

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Respiratory Distress

• Tintinalli Chapter 65

2
Dyspnea

• Subjective feeling of difficult, labored, or
  uncomfortable breathing
• 2/3 presenting with it have a pulmonary or
  cardiac disorder
• Other variations
• Tachypnea rapid
• Orthopnea recumbent
• Paroxysmal nocturnal dyspnea awakens from sleep
• Platypnea upright position
• Trepopnea left or right lateral decubitus

3
Clinical features

• Most Common Causes

• Life Threatening Causes

• Obstructive Airway
• Heart Failure
• Ischemic
• Pneumonia
• Psychogenic

• Upper airway obstruction
• Tension Pneumo
• PE
• Neuromuscular
• Fat Embolism

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Diagnosis

• History past med hx, previous hospitalizations,
  previous intubations, ICU stays, compliance,
  smoking hx, exposures
• Pulse ox
• ABG
• CXR
• BNP
• EKG

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Treatment

• Maintence of airway and oxygenation
• paO2gt60 mmHg and O2 sat gt90

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Hypoxemia

• Arbitrarily defined as PaO2lt60 mmHg.
• Abnormally low arterial oxygen tension.
• CaO2 .0031 X PaO2 1.38 X Hb X SaO2

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Relative hypoxemia

• Arterial oxygen tension is lower than expected
  for a given level of inhaled oxygen
• Assess using A-a gradient
• 145 PaCO2 PaO2
• Normal is lt10 in young healthy patients
• Increases with age 2.5 .21(age in years)(11)

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Pathophysiology

• Hypoventilation
• Right to left shunt
• Ventilation Perfusion mismatch
• Diffusion impairment
• Low inspired oxygen
• Compensation

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Clinical Features, Diagnosis, Treatment

• Agitation, headache, somnolence, coma, seizures
• Tachypnea and hyperventilation
• ABG required (not just pulse ox)
• Airway and supplemental oxygen

10
Hypercapnea

• Arbitrarily defined as PaCO2 gt 45 mmHg
• Causes
• Depressed central resp drive, thoracic cage
  disorders, neuromuscular impairment, COPD, upper
  airway obs

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Pathophysiology

• Dead space and tidal volume
• Alveolar volume (Ta) TV dead space (Td)
• Alveolar ventilation is Ta(TV TD) X Rate

12
Clinical Features, Diagnosis Treatment

• Acute Increased ICP, headache, confusion,
  lethargy, seizures, coma
• Chronic can be well tolerated
• ABG required for diagnosis
• Acute bicarb ? 1 mEq for q 10 mmHg ? PaCO2
• Chronic bicarb ? about 3.5 mEq for q 10 mmHg ?
  PaCO2
• www.medcalc.com

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Wheezing

• Musical sounds produced by airflow through
  central and distal airways.
• Airway flutter and vortex shedding

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Clinical features

• Associated with asthma and other obstructive
  diseases
• Bronchial obstruction caused by muscular spasm
  and inflammation
• Causes
• Upper angioedema, foreign body, infection
• Lower asthma, bronchioloitis, COPD, foreign body
• CV cardiogenic pulm edema, ARDS, PE
• Psychogenic

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Diagnosis

• Bedside spirometry
• FEVgt80 normal
• FEV 50-80 mild obs
• FEV 25-50 moderate obs
• FEV lt25 severe airflow obs
• CXR (especially no history of asthma)
• ABG (most mild to moderate do not require)

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Treatment

• B agonists
• Anticholinergics
• Systemic or inhaled corticosteroids

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Cough

• Protective reflex to clear secretions and foreign
  debris from tracheobronchial tree
• Many stimulants
• Irritant receptors vagus n cough center in
  medulla

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Clinical features

• Common acute last lt 3 wks
• URI, bronchitis, pneumonia, allergic rxn
• Subacute
• Usually post-infectious
• Chronic gt8 wks
• smoking, chronic bronchitis, postnasal discharge,
  GERD, asthma, and ACE inhibitor

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Diagnosis Treatment

• Acute
• CXR antitussives
• Intractable 4cc neb l lidocaine
• Chronic
• ? exposure to irritants, d/c ACEi, ARB, Bblocker
• Tx postnasal drip antihistamine, image sinus
• Tx asthma
• CXR
• Tx GERD
• Consult Pulm, CT chest, bronchoscopy

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Hiccups

• Spastic contraction of inspiratory muscles
  against a closed glottis

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Clinical features

• Acute (benign, self-limiting)
• gastric distention, alcohol, smoking, change in
  air temperature
• Chronic (persistent, intractable)
• vagal or phrenic n damage, hair in auditory canal
  pressing tm and stimulating auricular branch of
  vagus nerve, general anesthesia

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Diagnosis

• History
• Persistence during Sleep? Organic cause
• Resolution during sleep? Psychogenic cause
• Hx of general anesthesia
• CXR
• Ear examination

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Treatment

• Swallowing teaspoon of granulated sugar
• Chlorpromazine 25 to 50 mg IV
• Metoclopramide 10 mg IV or IM
• If effective, give oral therapy

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Cyanosis

• Bluish color of skin and mucous membranes
• Determined by absolute amount of deoxygenated
  hemoglobin in the blood

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Pathophysiology

• Traditional deoxygenated Hb exceeds 5 g/dL
• Can be detected as low as 1.5
• Can be detected at SaO2 of 85 or not until SaO2
  has reached 75
• Numerous physiological and anatomic factors
• Most sensitive site?

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Clinical features

• Central unsaturated arterial blood or abnormal
  hemoglobin
• Affects mucous membranes and skin
• Peripheral slowing of blood flow to an area and
  ? extraction of O2 from arterial blood
• CHF, cold extremities, shock, PVD,
  vasoconstriction

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Diagnosis

• ABG and pulse ox (methemoglobin or
  carboxyhemoblobin)
• Central oxygen saturation is decreased
• Peripheral oxygen saturation should be normal
• Methemoglobin or carboxyhemoglobin normal PaO2
  and decrease in measured oxygen saturation

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Diagnosis, contd

• If measured PaO2 and Hb concentration are normal,
  think pseudocyanosis
• Heavy metals, drugs (amiodarone, chloroquine),
  chrysiasis (comp of gold treatment with blue
  pigmentation of skin when exposed to light),
  argyria (slate blue due to ingestion/application
  of silver)
• Hereditary methemoglobimemia
• Genetic disorder affecting NADH-methemoglobin
  reductase
• Usually compensated and asymptomatic

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Treatment

• Supplemental oxygen
• Failure to improve
• Shock, abnormal hgb, or pseudocyanosis
• Acquired methemoglobinemia methylene blue with
  caution

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Pleural Effusion

• Fluid accumulating in potential space between
  visceral and parietal pleura
• Causes
• Transudate imbalance in hydrostatic or oncotic
  pressure (low protein)
• CHF, nephrotic syn, cirrhosis
• Exudate active fluid fluid secretion or leakage
  (high protein)
• cancer, pneumonia, pe, infection, rheum
  disorders, uremia, pancreatitis, amiodarone

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Pathophysiology

• Any process that
• Increases parietal fluid production
• Interferes with fluid absorption

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Clinical features

• Percussion dullness
• Decreased breath sounds
• Dyspnea
• Pain with respiration

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Diagnosis

• Upright CXR requires 150 to 200 mL of pleural
  fluid
• Thoracentesis
• Light criteria 1 or more
• fluid/serum protein ratio gt.5
• fluid/serum ratio LDHgt.6
• pleural LDHgt2/3 of upper limit for serum LDH

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Additional tests if exudative

• Gram stain
• Cell count
• Glucose
• Cytology
• pH
• Amylase
• Fungal/TB stains/assays

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Treatment

• Thoracentesis if dyspnea at rest
• Drainage with thoracostomy tubes if empyema
• Parapneumonic effusions with positive cultures,
  gram stain, or pHlt7.1 thoracostomy tube drainage
• Diuretics for CHF

36
References

• Tintinalli, Ch. 65