1 - Lung Expansion

Info from 'Respiratory Care: Principles and Practice,' 4th edition

A&P of respiratory system

• upper respiratory tract

  • nasal cavity, pharynx, larynx

• lower respiratory tract

  • trachea, bronchi, lungs

airway clearance therapy

lung therapy that decreases airway resistance (R_aw), shortens time constants (T_c), and reduces air trapping & hyperinflation (ie, COPD)

lung expansion therapy

lung therapy that increases lung compliance (C_L) and decreases airway resistance (R_aw)

formula for time constant (T_c)

T_c = C_L × R_aw

transmural pressure

difference between pressures inside and outside the lungs

• positive pressure: sphere distends

• negative pressure: sphere collapses

transpulmonary pressure

difference between pressures of alveoli and pleural space

• holds lungs open

transthoracic pressure

difference between pressures of pleural space and body surface of lungs

• forces lungs to deflate

transrespiratory pressure

difference between pressures of alveoli and outside atmosphere

gel layer

• layer of mucociliary transport formed by mucous and goblet cells

• traps dust, pollen, contaminants, and microorganisms

cilia

• tiny hairs in the mucociliary tract that beat in wavelike motion towards pharynx

• produce up to 100 mL of mucus per day

atelectasis

• incomplete expansion or complete collapse of alveoli

  • common pulmonary complication post-op

• types: gas, nitrogen washout, mucus plugging, anesthesia

  • 20-25% of basal collapse after anesthesia

• passive: hypoventilation, pain, sedation, diaphragm weakness

lung expansion therapies

• incentive spirometry

• deep breathing

• positive pressure (increasing alveolar pressure and changing gradient to pleural spaces)

  • intermittent positive pressure breathing (IPPB)

  • PAP (CPAP & PEEP)

mechanisms of lung expansion therapies

• increasing transpulmonary pressure

• reducing atelectasis

• enhancing alveolar ventilation

clinical goals of lung expansion therapies

• improving oxygenation

• preventing post-op pulmonary complications

• re-expansion of collapsed alveoli

patient populations for lung expansion therapies

• patients with neuromuscular disease

• post-op patients

• patients with atelectasis

patient goals for lung expansion therapy

• what type of therapy? (find patient’s VC)

• measure VC

  • >15 mL/kg IBW

    • deep breathing and coughing

  • 10-15 mL/kg IBW

    • incentive spirometry

  • 5-10 mL/kg IBW or IC <1/3 predicted

    • positive pressure

  • <5 mL/kg

    • impending respiratory failure

breathing exercises

• deep breathing

  • diaphragmatic if VC ≥ 15 mg/kg IBW

• maximal expiration

  • patients coached

  • inspiration from resting expiration

  • end-expiratory hold

incentive spirometry

lung expansion therapy that:

• maintains airway patency

• prevents/reverses atelectasis

• aids in secretion mobilization

• increases muscle strength

positive airway pressure (PAP)

lung expansion therapy that includes CPAP, PEP, EPAP, IPPB, MV

• increases transpulmonary pressure gradient (increases lung expansion)

• prevents/reverses atelectasis

• mobilizes secretions

• optimizes delivery of bronchodilators in patients having bronchial hygiene therapy

• reduces air trapping in asthma & COPD

contraindications for PAP

• untreated pneumothorax

• patient’s inability to tolerate increased WOB (acute asthma, COPD)

• ICP > 20 mmHg

• hemodynamic instability

• recent facial/oral/skull surgery or trauma

• hypoventilation

• acute sinusitis

• epistaxis

• esophageal surgery

• active hemoptysis

• nausea

• tympanic membrane rupture or other middle ear pathology

hazards & complications for PAP

• increased WOB

• increased ICP

• myocardial ischemia, decreased venous return

positive airway pressure (PAP)

lung expansion therapy that uses 1-way inspiratory valve and 1-way expiratory valve

• diaphragm breathing

• exhale against fixed-orifice resistors (back pressure)

  • flow restrictor

• generates pressures during expansion that uses range from 10-20 cm H₂O

  • feel vibrations over central chest during exhalation

  • 10-20 breaths followed by cough

  • repeat 4-6x

expiratory positive airway pressure (EPAP)

lung expansion therapy that uses threshold resistor

• opposes exhalation

  • one-way valve allows gas at ambient pressure to enter airway on inspiration and directs exhaled gas through threshold resistor

• pressures of 10-20 cm H₂O

continuous positive airway pressure (CPAP)

lung expansion therapy that involves breathing through a pressurized circuit against threshold resistor

• 5-20 cmH₂O during inspiration and expiration

• oxygenation and lung expansion

bilevel positive airway pressure (BiPAP)

lung expansion therapy similar to CPAP but can set different pressure levels for inspiration (IPAP) and expiration (EPAP)

• oxygenation, lung expansion, and ventilation