CPAP and Bi-level PAP Therapy

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Salient Points

This article focuses on improving our understanding of PAP therapy, to gain working knowledge of the device, study the clinical research evidence and implementation of PAP therapy. The purpose is to spread information in order to educate healthcare providers and systems.

It includes the following:

  1. Basic understanding of the CPAP system – CPAP – Continuous Positive Airway Pressure Therapy – maintains the airway pressure despite inspiration and expiration of the patient.
  2. Beneficial effects of CPAP – preventing the collapse of the upper airway, greater end expiratory lung volume, increase in oxygen stores, increased tracheal traction – improves upper airway patency, etc.
  1. Negative effects of CPAP – Negative effects of CPAP, may decrease venous return, increase load on abdominal muscles, provoke anxiety, etc.
  1. Bi-level PAP therapy
  2. Comparison between Bi-level PAP and CPAP
  3. Clinical evidence of the effects of Bi-level PAP and CPAP therapy

There is evidence to support that in OSA patients, PAP ameliorates sleepiness in patients with OSA, motor vehicle accidents are reduced in patients with OSA following initiation of CPAP treatment. Bi-level PAP has been shown to improve health related quality of life in patients with obesity hypoventilation syndrome and ALS.

Detailed Summary

CPAP – Continuous Positive Airway Pressure Therapy – maintains the airway pressure despite inspiration and expiration of the patient. It is maintained within an FDA specified pressure range (eg +/- 1.5cm H2O), this is necessary as it ensures the device maintains a certain prescription pressure for the patient.

This error range is greater with larger tidal volumes, inspiratory effort from patients, increased RR and at higher prescription pressure settings.

The CPAP device works to splint the airway open – preventing the collapse of the upper airway.

Other beneficial effects of CPAP:

  1. Greater end expiratory lung volume.
  2. Increase in oxygen stores.
  3. Increased tracheal traction – improves upper airway patency.
  4. Lowers cardiac after load.
  5. Increases cardiac output.

Negative effects of CPAP

  1. May decrease venous return
  2. Increase load on abdominal muscles
  3. Provoke anxiety
  4. May propagate central apneas
  5. May reduce PaCO2 levels
  6. Ventilatory instability – central apneas and periodic breathing.

Other Side Effects

  1. Mask related skin changes
  2. Aerophagia
  3. Sinus Pain
  4. Oral and nasal dryness
  5. Tooth decay

In Spite of the above downsides, CPAP may be one of the most cost – effective and least toxic forms of medical therapy.

Bi-level PAP Therapy – based on the idea of varying the administered pressure between the inspiratory and expiratory cycles. This would decrease the amount of pressure against which the patient exhales, which decreases the abdominal muscle strain and respiratory discomfort during the expiratory cycle.

Advantage of Bi-Level PAP when compared to CPAP.

  • Greater Tidal Volume
  • Reduced strain on abdominal muscles
  • The difference between the IPAP and EPAP could be considered as pressure support level that could augment the inspired tidal volume. This can be used to combat non-obstructive hypoventilation that may occur in host conditions.

In adults, the maximum IPAP pressure setting for bi-level PAP is not to exceed 30 cm H2O, and the minimum difference between IPAP and EPAP level should not be less than 4 cm H2O.

Transition is recommenced from CPAP to bi-level PAP is encouraged when the CPAP level approaches 15 cm H2O and exhalation against CPAP levels approaching 15 cm H2O can be uncomfortable for most patients.

Although the above mentioned advantages of Bi-level PAP may seem promising, there is no major advantage over CPAP from an adherence point of view.

Clinical Evidence for CPAP and Bi-level PAP

  • There is evidence to support that in OSA patients, PAP ameliorates sleepiness in patients with OSA, motor vehicle accidents are reduced in patients with OSA following initiation of CPAP treatment.

Bi-level PAP therapy has been shown to improve health related quality of life in patients with obesity hypoventilation syndrome and ALS.

Reference Link : https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3119924/

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