Continuous Positive Airway Pressure (CPAP): An Overview

Continuous positive airway pressure (CPAP) is a therapeutic modality in respiratory care that provides constant, gentle pressure to keep the airways open and support effective breathing. It is widely recognized for its role in treating obstructive sleep apnea, but its benefits extend into acute and critical care, where it can improve oxygenation and reduce the need for invasive ventilation.

This article explores what CPAP is, how it works, why it’s relevant to respiratory therapists, and the impact it has on the field of respiratory care.

Free Access

RRT Course and Quiz Bundle (Free)

Get free access to 15+ premium courses and quizzes that cover the most essential topics to help you become a Registered Respiratory Therapist (RRT).

Get Free Access

What Is CPAP?

Continuous positive airway pressure (CPAP) is a noninvasive ventilation strategy that delivers a constant flow of pressurized air to keep the airways open. Unlike invasive mechanical ventilation, which requires an endotracheal tube, CPAP is administered via a snug-fitting mask, nasal pillows, or sometimes a full-face interface.

The continuous stream of air creates positive pressure in the airways throughout the breathing cycle, preventing collapse and ensuring adequate oxygenation.

The concept of CPAP was first introduced in the early 1980s for obstructive sleep apnea (OSA) patients, and since then, it has revolutionized treatment not only for sleep-related breathing disorders but also for conditions like acute respiratory distress syndrome (ARDS), congestive heart failure, and neonatal respiratory distress.

CPAP operates on a simple yet powerful principle: by maintaining a baseline pressure within the airways, the alveoli are kept open, thereby improving gas exchange and reducing the work of breathing.

How CPAP Works

To appreciate CPAP’s effectiveness, it helps to understand the physiology behind it. During normal breathing, small airways and alveoli can sometimes collapse at the end of exhalation, particularly in patients with obstructive or restrictive lung disease. This collapse leads to impaired oxygenation and increased effort to re-expand the airways with the next breath.

CPAP prevents this collapse by applying continuous positive pressure. Here’s what it accomplishes physiologically:

• Maintains alveolar recruitment: Prevents alveoli from collapsing, maximizing the surface area available for gas exchange.
• Improves oxygenation: By keeping alveoli open, more oxygen crosses into the bloodstream.
• Reduces work of breathing: Patients expend less effort to re-expand their lungs, which lowers respiratory muscle fatigue.
• Supports functional residual capacity (FRC): CPAP increases the volume of air remaining in the lungs after exhalation, improving ventilation–perfusion matching.

Note: This mechanism is particularly beneficial in disorders like OSA, where soft tissues obstruct the airway during sleep, or in pulmonary edema, where positive pressure can help push fluid out of alveoli and into the interstitial space.

CPAP in Sleep Medicine

The most common and recognizable use of CPAP is in treating obstructive sleep apnea (OSA). OSA occurs when the upper airway collapses repeatedly during sleep, causing apneas (pauses in breathing) and hypopneas (shallow breaths). Left untreated, OSA contributes to daytime sleepiness, cardiovascular disease, hypertension, and decreased quality of life.

CPAP is considered the gold standard therapy for OSA. By splinting the upper airway open, it prevents obstruction and restores normal sleep architecture. For respiratory therapists, this area of practice often involves patient education, mask fitting, troubleshooting leaks, and encouraging adherence to therapy.

Compliance is a major challenge—patients often struggle with mask discomfort, nasal congestion, or claustrophobia. Respiratory therapists play a critical role in overcoming these barriers, ensuring patients remain engaged in their therapy.

CPAP in Acute Care

Beyond sleep labs, CPAP plays a crucial role in acute and critical care settings. It can be used as an alternative to intubation for certain patients with respiratory distress. Examples include:

• Acute cardiogenic pulmonary edema: CPAP reduces preload and afterload on the heart while improving oxygenation, often stabilizing patients quickly.
• Post-extubation support: In some cases, CPAP helps prevent reintubation by maintaining airway patency and oxygenation during recovery.
• Acute hypoxemic respiratory failure: CPAP can buy time while underlying causes are treated, potentially avoiding the need for invasive ventilation.

In neonatal intensive care units, CPAP is life-saving for premature infants with immature lungs. Nasal CPAP delivers gentle positive pressure that supports alveolar expansion, reduces apnea of prematurity, and helps neonates transition from intrauterine to extrauterine life without the risks of mechanical ventilation.

The Role of Respiratory Therapists

Respiratory therapists are highly involved in the administration of CPAP therapy. Their responsibilities include assessment, initiation, monitoring, and adjustment of CPAP therapy across a wide spectrum of patients.

Key responsibilities include:

• Patient assessment: Determining the need for CPAP, evaluating oxygenation status, and identifying contraindications (e.g., untreated pneumothorax).
• Equipment setup and calibration: Ensuring the machine delivers the prescribed pressure and flow, verifying alarms, and selecting the proper interface.
• Patient education and support: Teaching patients how to use their CPAP device, troubleshoot common issues, and maintain their equipment.
• Monitoring outcomes: Assessing ABGs, oxygen saturation, and clinical signs to ensure CPAP is effective.
• Interdisciplinary collaboration: Working alongside physicians, nurses, and sleep technologists to provide comprehensive care.

Note: For respiratory therapists, proficiency with CPAP therapy is non-negotiable. It blends technical skill with patient-centered care, requiring both clinical expertise and empathetic communication.

CPAP in the Broader Context of Respiratory Care

The relevance of CPAP to respiratory care goes beyond individual therapy. It reflects several key themes in the profession:

• Noninvasive support over invasive intervention: CPAP exemplifies the shift toward noninvasive strategies that reduce complications associated with intubation and mechanical ventilation.
• Patient-centered care: Success with CPAP often depends on patient comfort, adherence, and understanding, making RTs critical educators and advocates.
• Evidence-based practice: Research consistently validates CPAP’s role in improving outcomes for OSA, pulmonary edema, and neonatal distress, reinforcing the importance of science-driven care.
• Expanding scope of practice: With the rise of home care, telehealth, and sleep medicine, RTs are increasingly needed to support patients outside the hospital, extending the impact of CPAP into community health.

CPAP Practice Questions

1. What is the primary purpose of CPAP therapy?  
To improve oxygenation and support adequate oxygenation at lower levels of inspired oxygen (FiO2).

2. What type of CPAP device fits over the nose and mouth or just the nose?  
Mask CPAP

3. Which type of CPAP is commonly used short-term for conditions like carbon monoxide poisoning, pneumonia, or postoperative atelectasis?  
Mask CPAP

4. What are two common disadvantages of mask CPAP?  
Difficulty maintaining a proper seal and poor patient tolerance.

5. Which type of CPAP is preferred for neonates due to their obligate nasal breathing?  
Nasal CPAP

6. What is a common issue when using nasal CPAP on a crying neonate, and how can it be corrected?  
CPAP pressure may be lost due to crying; readjusting the nasal prongs can help restore effectiveness.

7. What type of CPAP is used in patients with an endotracheal tube?  
CPAP mode of mechanical ventilation

8. When using endotracheal CPAP, what is essential to monitor continuously?  
Airway pressure, along with setting an appropriate low-pressure alarm.

9. In a CPAP system, what does a loss of pressure typically indicate?  
A leak in the system or insufficient flow; increasing the flow may correct the issue.

10. What does an increased pressure in a CPAP system generally suggest?  
An obstruction in the circuit or patient interface.

11. What happens when there is excessive flow in a CPAP system?  
Continuous venting of the pressure release (pop-off) valve occurs.

12. How would you define CPAP in terms of respiratory support?  
A noninvasive method of providing ventilatory support for patients in respiratory distress.

13. In which conditions is CPAP commonly used?  
Acute pulmonary edema, COPD exacerbations, and acute bronchospasm—especially when combined with beta-2 agonists.

14. How does CPAP improve oxygenation and ventilation?  
It increases airway pressure, opens collapsed alveoli, prevents further atelectasis, enhances oxygen diffusion, and reduces interstitial fluid accumulation.

15. What is the intended outcome of using CPAP therapy?  
To improve lung compliance and make spontaneous breathing easier for the patient.

16. What component of the CPAP system helps control the pressure delivered to the patient?  
A pressure relief valve integrated into the face mask.

17. When is CPAP indicated?  
In patients with respiratory distress whose own efforts are insufficient to meet oxygen demand.

18. What are general clinical indications for using CPAP?  
Respiratory distress with preserved drive, patent airway, normal blood pressure, alertness, rapid breathing, submersion injury, bronchospasm, or SpO2 < 90%.

19. What are the contraindications for CPAP use?  
Respiratory arrest, hypoventilation, suspected pneumothorax or chest trauma, tracheostomy, active vomiting or GI bleeding, inability to follow commands, facial abnormalities, or intolerance of the mask.

20. What is the recommended initial PEEP setting when using CPAP?  
Between 5 and 10 cm H2O.

21. What are the steps for applying CPAP to a patient?  
Check equipment, assemble tubing and mask, confirm oxygen flow, allow the patient to adjust to the mask before strapping it on, then reassess for effectiveness and safety.

22. How can CPAP lead to hypotension?  
By increasing intrathoracic pressure, which reduces venous return (preload) to the heart, potentially causing a drop in blood pressure.

23. What does CPAP stand for?  
Continuous Positive Airway Pressure

24. What is continuous positive airway pressure (CPAP)?  
The delivery of constant positive pressure to the airways of a spontaneously breathing patient throughout the entire respiratory cycle.

25. Is CPAP considered an invasive or noninvasive form of ventilation support?  
Noninvasive; it supports ventilation without the need for intubation.

26. Is the flow of gas in CPAP therapy continuous?  
Yes. The patient breathes with and against a constant positive airway pressure.

27. CPAP is most similar to which mechanical ventilation setting?  
PEEP (Positive End-Expiratory Pressure).

28. What is the purpose of CPAP pressure during expiration?  
To prevent alveolar collapse and maintain lung volume.

29. What are some benefits of using CPAP therapy?  
It keeps airways open, reduces atelectasis, improves gas exchange surface area, and increases lung compliance.

30. What is atelectasis?  
A condition involving collapsed alveoli, leading to reduced or absent gas exchange in part of the lung.

31. Has the international use of CPAP increased in recent years?  
Yes. Studies have shown its effectiveness, leading to widespread adoption in the U.S., Europe, and other developed countries, especially in neonatal care.

32. Is CPAP feasible in low-resource or low-cost settings?  
Yes. CPAP can be delivered using affordable, simplified equipment.

33. By what approximate percentage can CPAP reduce the need for intubation?  
Up to 50%.

34. Why is it important to monitor skin integrity under a CPAP mask?
To prevent pressure ulcers and skin breakdown from prolonged mask contact.

35. What types of masks can be used to administer CPAP?  
Nasal mask, full face mask, or nasal pillow interface.

36. In CPAP mode, do you set a respiratory rate on the device?  
No, CPAP does not provide a set respiratory rate. It supports spontaneous breathing only.

37. What adjustment should be made if a patient begins hypoventilating while on CPAP?  
Switch the patient to BiPAP, which provides both inspiratory and expiratory pressure support.

38. CPAP provides pressure during which phase(s) of a spontaneous breath?  
Throughout the entire respiratory cycle, including inspiration and expiration.

39. Who performs the total work of breathing when a patient is on CPAP?  
The patient. CPAP does not deliver mechanical breaths.

40. CPAP is primarily indicated for which type of sleep apnea?  
Obstructive Sleep Apnea (OSA).

41. Can a nasal trumpet be placed in a patient using CPAP or BiPAP?  
Yes. A nasal trumpet can be used with both CPAP and BiPAP for airway support.

42. Can an oral airway be used in a patient on CPAP or BiPAP?  
No. Oral airways are typically used only in unconscious patients who cannot tolerate CPAP/BiPAP masks.

43. What are some contraindications to using CPAP therapy?  
Claustrophobia, apnea, neuromuscular disease, facial trauma, inability to protect the airway, and hypoventilation syndrome.

44. Should CPAP be used in a patient experiencing respiratory failure?  
No. CPAP is not appropriate for patients in severe respiratory failure.

45. What conditions are contraindicated for CPAP use?  
Central apnea, cardiac arrest, extreme respiratory failure, facial trauma, and an unprotected airway.

46. What role does tube depth play in CPAP therapy?  
The depth of the CPAP interface can influence the pressure delivered to the airways.

47. How is the level of CPAP measured, and what is the typical starting range?  
Measured in cm H₂O; typically started at 5–6 cm H₂O and may be increased up to 10 cm H₂O as needed.

48. What are the requirements for using nasal prongs effectively with CPAP?  
Prongs must be the correct size for a good seal; tape can be used to enhance fit, and prongs should be secured in place.

49. What are key tips for successful CPAP application in neonates?  
Ensure a good nasal seal, encourage nasal breathing, keep the mouth closed, and ensure the patient remains calm.

50. How can you tell if CPAP is functioning correctly in a bubble CPAP setup?  
Bubbling in the water chamber indicates pressure is being delivered and CPAP is functioning properly.

51. What is a nasal mask in CPAP therapy?  
A triangular-shaped mask that fits over the bridge of the nose and sits just above the upper lip.

52. What is a nasal pillow in CPAP therapy?  
A minimal interface that rests under the nostrils, providing comfort and greater freedom of movement.

53. What is a full face mask in CPAP therapy?  
A mask that covers both the nose and mouth to deliver continuous airway pressure.

54. Who benefits most from using a nasal mask with CPAP?  
Patients who primarily breathe through their nose.

55. What is an important consideration when using a nasal mask for CPAP?  
Monitor the bridge of the nose for signs of skin breakdown due to prolonged mask use.

56. What is the primary function of CPAP in acute pulmonary edema?  
To improve oxygenation and reduce preload by shifting fluid out of the alveoli into circulation.

57. How does CPAP reduce the work of breathing?  
By maintaining airway patency and improving lung compliance, reducing the effort required for inhalation.

58. In what situation should CPAP be removed immediately?  
If the patient vomits or aspirates, or if there’s a sudden drop in blood pressure or consciousness.

59. Why must the patient be alert and cooperative for CPAP to be effective?  
Because CPAP is a noninvasive therapy that requires spontaneous breathing and mask tolerance.

60. What vital sign should be monitored closely when initiating CPAP?  
Blood pressure, due to potential hypotension from increased intrathoracic pressure.

61. What is the goal of CPAP therapy in patients with atelectasis?  
To reopen collapsed alveoli and prevent further collapse.

62. Why should you avoid using CPAP in patients with suspected pneumothorax?  
Positive pressure can worsen the condition by increasing air leakage into the pleural space.

63. How does CPAP help improve oxygenation without increasing FiO₂?  
By recruiting alveoli and increasing the surface area for gas exchange.

64. Which patients benefit most from nasal pillows for CPAP delivery?  
Those who are nasal breathers and seek a low-profile, comfortable fit.

65. How does CPAP influence venous return to the heart?  
It can reduce venous return due to increased intrathoracic pressure, potentially causing hypotension.

66. What effect does a poor mask seal have on CPAP therapy?  
It leads to pressure loss and reduced therapeutic effectiveness.

67. How often should the skin under the CPAP mask be assessed?  
At least every 2 hours to prevent pressure injuries and skin breakdown.

68. Why should mouth breathing be discouraged during nasal CPAP use?  
It causes loss of pressure and reduces CPAP effectiveness.

69. What is one method to ensure a better seal with nasal prongs?  
Use of adhesive strips or tape to improve prong fit and prevent dislodgement.

70. Why is CPAP commonly used in patients with obstructive sleep apnea?  
To splint the airway open and prevent airway collapse during sleep.

71. What is the typical range for therapeutic CPAP pressure settings?  
Between 5 and 10 cm H₂O.

72. Can CPAP be used continuously throughout the day?  
No. It is generally intended for use during sleep or short-term respiratory distress.

73. What type of humidification may be required during CPAP therapy?  
Heated humidification to prevent nasal dryness and discomfort.

74. What feature on a CPAP machine prevents excessive pressure buildup?  
A pressure relief or pop-off valve.

75. What patient position can help improve the effectiveness of CPAP?  
Semi-Fowler’s or upright position to optimize lung expansion.

76. Why is CPAP considered a lung recruitment strategy?  
Because it opens collapsed alveoli and maintains them open to enhance gas exchange.

77. When starting CPAP, what should you do if the patient feels anxious?  
Reassure them, allow them to hold the mask first, and introduce pressure gradually.

78. What is one sign that CPAP therapy may be failing?  
Worsening oxygen saturation or increased work of breathing despite therapy.

79. What complication may arise from excessive CPAP pressure?  
Barotrauma, including pneumothorax or gastric insufflation.

80. How is the effectiveness of CPAP measured clinically?  
By assessing improvements in SpO₂, respiratory rate, work of breathing, and patient comfort.

81. What is the primary physiological benefit of using CPAP in neonates?  
It helps maintain functional residual capacity and prevent alveolar collapse.

82. How does CPAP impact the alveolar-capillary membrane?  
By improving oxygen diffusion through increased surface area and reduced atelectasis.

83. What should you do if a patient on CPAP becomes nauseated?  
Remove the mask immediately and monitor for vomiting or aspiration.

84. Why must a CPAP system include a low-pressure alarm?  
To alert the clinician if the circuit disconnects or pressure drops due to a leak.

85. Can CPAP be used in conjunction with aerosolized bronchodilator therapy?  
Yes, it can enhance medication delivery in patients with bronchospasm.

86. What should you assess first if a CPAP machine is alarming for high pressure?  
Check for an obstruction in the circuit or patient airway.

87. Why might a full-face CPAP mask be used instead of a nasal interface?  
For mouth breathers or patients who cannot tolerate nasal-only interfaces.

88. What is the potential gastrointestinal complication from excessive CPAP pressure?  
Aerophagia, which may lead to bloating or gastric distension.

89. How can you minimize air leaks with nasal CPAP in neonates?  
Ensure proper prong sizing and secure attachment with straps or adhesive.

90. What is the role of bubbling in a water seal CPAP system?  
It indicates that the system is maintaining positive pressure.

91. When should CPAP be weaned in a stable patient?  
Once oxygenation has improved and signs of respiratory distress have resolved.

92. What is the effect of CPAP on functional residual capacity (FRC)?  
It increases FRC by keeping alveoli open at end-expiration.

93. Why is patient cooperation essential for effective CPAP therapy?  
Because the patient must maintain a tight mask seal and tolerate continuous pressure.

94. What might indicate that CPAP therapy is no longer effective for a patient?  
Declining oxygen saturation and increasing respiratory rate despite therapy.

95. How does CPAP differ from BiPAP in terms of pressure support?  
CPAP delivers a single continuous pressure, while BiPAP provides different pressures for inspiration and expiration.

96. Can CPAP be initiated in a pre-hospital setting?  
Yes, especially for conditions like pulmonary edema or severe respiratory distress.

97. What is the significance of humidification in CPAP therapy?  
It prevents drying of mucosal membranes and improves patient comfort.

98. What should you do if a CPAP mask is causing facial pressure sores?  
Switch to a different mask type or use protective dressings.

99. What is one method to improve CPAP compliance in new users?  
Educate the patient thoroughly and start at a lower pressure to improve tolerance.

100. How does CPAP help patients with cardiogenic pulmonary edema?  
It reduces preload and afterload, thereby decreasing pulmonary congestion.

Final Thoughts

Continuous positive airway pressure (CPAP) has proven to be a reliable and versatile therapeutic measure that enhances breathing, improves oxygenation, and reduces complications in patients across various settings.

Whether used in the management of obstructive sleep apnea, acute cardiogenic pulmonary edema, or neonatal respiratory distress, CPAP demonstrates the value of noninvasive support in modern practice.

For respiratory therapists, proficiency with CPAP is essential, as it combines technical skill with patient-focused care and highlights the profession’s critical role in improving outcomes.