All articles by Talk About Sleep

The Talk About Sleep Mission: to be a world leader in the sleep field by providing quality information, support and resources to sleep disorder patients, their family, friends and healthcare professionals.

Mouth Leak and the Vicious Cycle

The following information is provided by: Fisher & Paykel Healthcare

Mouth Leak

Mouth LeakWhen a patient is receiving CPAP therapy, exhaling against the force of the constant pressure can be difficult. Often patients will open their mouths slightly when they sleep or even begin to breathe through their mouths. In doing this, a proportion of the incoming air travels in through the nose and straight out the patient’s mouth. This is known as unidirectional flow.


The Vicious Cycle

The Vicious CycleThe vicious cycle describes the situation which often occurs as a result of mouth leak. When the patient falls asleep while using CPAP therapy, mouth leak may occur. Because incoming air is able to travel directly out through the patient’s mouth without first going to the lungs, unidirectional airflow occurs. The increased flow of cold dry air through the nasal passages causes mucosal drying and rebound congestion. The swelling that occurs in rebound congestion results in a decrease in nasal airway diameter and as a result, increased nasal airway resistance occurs.

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CPAP Therapy Potential Problems

The following information is provided by Fisher & Paykel Healthcare

If typical room air is at 20ºC containing about 10 mg H2O per litre of gas, and the body supplies the remaining heat and moisture required for efficient gas exchange, what happens during CPAP therapy?

The nasal airway is unable to maintain sufficient warmth and humidity for the increased gas flow of CPAP therapy. As a result, the patient’s airways lose moisture, and they will eventually exhibit symptoms consistent with upper airway drying and inflammation, such as:

  • Dry nose
  • Breakdown of the soft tissue around the nares
  • Dry throat
  • Bleeding nose
  • Headache
  • Dry cracked lips
  • Chest discomfort
  • Infections of the nose, throat and sinuses

Such patients find speech and clearing of their dry nose difficult. This can often result in the patient being less compliant with the therapy.

Maximum compliance is achieved by maximizing patient comfort. The easiest and most successful way to increase patient comfort is by using heated humidification.

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How the Human Body Humidifies Air

The following information is provided by: Fisher & Paykel Healthcare


InspirationOne of the key functions of the nasal airway is to heat and humidify inspired gases. The nasal airway provides approximately 75% of the humidity added to each breath. The body heats the inspired gas to core body temperature and 100% RH by the time it reaches the gas exchange boundary in the lungs.



ExpirationWhen we expire, humidity is recovered from expired gases to humidify the next inspired breath. The remainder of the water requirement is supplied from the body’s systematic reserves. Airflow generated by CPAP is greater than normal and overcomes the body’s ability to heat and humidify the air 7,8.


A Cross Section of the Nasal Airway

Nasal Airway Cross SectionAs this MRI scan shows, the nasal airway is highly vascular, enabling it to be easily dried out by cold dry air.

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What is Humidity?

The following information is provided by Fisher & Paykel Healthcare

Humidity is the amount of water vapor in a gas. When discussing humidity, we can refer to either relative humidity or absolute humidity:

Humidity 1
Humidity 2
Absolute Humidity (AH) is the amount of water vapor per liter of gas, measured in mg/L.
Relative Humidity (RH) is a measure of how much water vapor is in the gas compared to its capacity to hold water vapor. It is measured as a percentage (%).

A. If a liter of gas can hold 44mg of water vapor and it contains 44mg, then it has 100% Relative Humidity (or it is saturated). B. If the same liter of gas contains only 22mg of water vapor, then it would only be half full or has 50% Relative Humidity.

Maximum Capacity

Maximum Capacity is The maximum amount of water vapor a gas can hold is determined by temperature.

Absolute Humidity

Humidification and CPAP

The graph above shows that heated humidification provides far greater humidity than both room air and cold passover humidification.

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Excessive Daytime Sleepiness And Narcolepsy

Interview with Michael Lacey, M.D.

Medical Director, Northside

Hospital Neurodiagnostic Laboratory

Medical Director, Neurotrials Medical Research Firm

Instructor, Northside Hospital School of Sleep Medicine Atlanta, GA

Conducted by Dan Rutz

Click here for the audio interview with Dr. Michael Lacey, M.D

In the first half of this interview, Dr. Michael Lacey explains the causes and consequences of Excessive Daytime Sleepiness emphasizing the importance of a good night’s sleep to help recharge certain areas of the brain.

In the second half of the interview, Dr. Lacey discusses Narcolepsy, a rare, but potentially dangerous sleep disorder, including the symptoms, the procedure for diagnosing it, and the medications to treat it.

Excessive Daytime Sleepiness

DAN RUTZ: Before we get into narcolepsy specifically, let’s talk in more general terms about the problem of…of lack of energy, of sleepiness during the day.


DAN RUTZ: I assume we’re talking about something that a lot of people can identify with.

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Abstract: Effects of a Heated Tube on Sleep Quality, With Active Heated Humidification During CPAP Therapy In a Cool Sleeping Environment

Printed with permission from Fisher&Paykel Healthcare

Poster Session: Advances in Obstructive Sleep Apnea
Nilius, Georg, Domanski, Ulrike, Franke, Karl-Josef, Ruhle, Kral-Heinz
Chest 2005 128: 232S-a


To compare the effect of conventional humidification with ThermoSmart™ heated breathing tube humidification on sleep quality and patient symptoms.


  • 19 OSA patients, prospectively recruited.
  • Patients underwent two full nights of polysomnography (PSG), in a cool room, whilst on CPAP at their pre-determined therapeutic pressure. Their first night was randomized to either conventional heated humidification or ThermoSmart™ heated breathing tube humidification. Patients crossed over to the alternative treatment arm on their second night.
  • PSG parameters were analyzed to determine objective quality of sleep and subjective questionnaires were administered to determine patient symptoms/side effects of therapy.


results graph

results graph


If condensation forms in the CPAP tubing system sleep quality is considerably reduced. When using CPAP therapy in a cool room, the use of a heated humidifier with a heated breathing tube improves sleep quality and subjective symptom scores.

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An Introduction To Narcolepsy And Daytime Sleepiness

A sleep disorder is a physical and psychological condition or disturbance of sleep and wakefulness caused by abnormalities that occur during sleep or by abnormalities of specific sleep mechanisms. Although the sleep disorder exists during sleep, recognizable symptoms manifest themselves during the day. Accurate diagnosis requires a polysomnogram, widely known as a “sleep test.”

It is estimated that some 40 million Americans suffer from chronic, long-term sleep disorders. Another 20 to 30 million Americans suffer from some kind of sleep disorder on an irregular basis. The annual costs in productivity, health care, and safety have been estimated in the billions of dollars.

What is Narcolepsy?

Narcolepsy is a neurological condition that causes patients to have excessive sleepiness during the day combined with recurring episodes of naps, particularly at inappropriate times.

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TalkAboutSleep Interviews Dr. Jed Black About Xyrem

Dr. Jed BlackDr. Jed Black, Director of the Stanford Sleep Disorders Center, was involved in the clinical trials for Xyrem, and answers our questions in the brief interview below:

TalkAboutSleep: Orphan’s new drug Xyrem treats the symptoms of narcolepsy. Which symptoms does it treat? What is the impact on those symptoms?

Dr. Black: Xyrem improves cataplexy, daytime alertness and nocturnal sleep. Improvement in any of these areas is often dramatic.

TalkAboutSleep: How does Xyrem work?

Dr. Black: Xyrem’s mechanism of action in narcolepsy symptoms is unclear. One component of its activity may be to improve the restorative nature of nocturnal sleep and thereby reduce symptom severity.

TalkAboutSleep: What is a typical dosage of Xyrem? How is it given?

Dr. Black: Xyrem is dosed in liquid form ranging from approximately 4-5 gram per night to 9-10 grams per night.

TalkAboutSleep: Are there any side-effects to Xyrem of any significance?

Dr. Black: Xyrem is taken at night because it causes marked sedation.

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