Cardiorespiratory polygraphy (synonym: sleep apnea screening) is a diagnostic measure used in sleep medicine for the detection of sleep-related breathing disorders. First and foremost is obstructive sleep apnea syndrome (OSAS), which is part of the metabolic syndrome (clinical name for the symptom combination obesity (overweight), hypertension (high blood pressure), elevated fasting glucose (fasting blood sugar) and fasting insulin serum levels (insulin resistance), and dyslipidemia (elevated VLDL triglycerides, lowered HDL cholesterol)) often affects obese (obese) patients. The apneas (respiratory arrests) result in a short-term drop in oxygen saturation (SpO2) and are terminated by an arousal reaction (intrinsic arousal), usually unnoticed by the patient. As a result, insufficiently restful sleep sets in, patients are fatigued during the day and are prone to dangerous microsleep. In addition, OSAS is an important risk factor for the development of secondary hypertension (high blood pressure as a secondary disease). Cardiorespiratory polygraphy is also called sleep apnea screening because it is an orienting search method and is performed as a pre-diagnosis on an outpatient basis (at home) using a mobile device. Polysomnography, which is monitored in a sleep laboratory and is used to specify the diagnosis, should be mentioned as a more advanced diagnostic method.
Indications (areas of application)
Cardiorespiratory polygraphy is used as an upstream diagnostic test for sleep-related breathing disorders. These include:
- Cheyne-Stokes respiration (CSA) – Pathologic breathing characterized by periodic increases and decreases in both depth and rate of breathing that occurs in the presence of inadequate cerebral perfusion.
- Altitude-induced periodic breathing – Pathological breathing when at high altitudes, resulting in altitude-induced hyperventilation (increased breathing) with sleep-through disturbances and increased daytime sleepiness due to a decreased oxygen supply.
- Hypoxemia syndrome (reduced oxygen content in the blood) in lung diseases – e.g. chronic obstructive pulmonary disease (COPD).
- Hypoxemia syndrome (decreased oxygen content in the blood) in neuromuscular diseases – e.g., amyotrophic lateral sclerosis (ALS; degenerative disease of the motor nervous system).
- Hypoxemia syndrome (decreased oxygen content in the blood) in musculoskeletal diseases – e.g., diseases of the skeleton or muscles responsible for respiratory movements.
- Obstructive sleep apnea syndrome (OSAS).
- Pickwick syndrome – Obestitas hypoventilation syndrome is a special or maximal form of OSAS and occurs in extremely obese patients.
- Follow-up when using a CPAP device (breathing aid that creates positive pressure to counteract airway narrowing).
- Central sleep apnea syndrome (ZSAS) – Pathological breathing resulting from damage to the respiratory center (formatio reticularis) in the CNS (central nervous system). Causes include adverse effects of centrally acting drugs.
Contraindications
Cardiorespiratory polygraphy is a noninvasive diagnostic procedure, so there are no contraindications, except for sufficient indication. However, a prerequisite for performance is sufficient compliance (patient cooperation) and ability to instruct the patient in the use of the device.
Before the examination
Before the examination, a detailed internal medical history and a thorough physical examination are necessary to narrow down the diagnosis. Cardiorespiratory polygraphy is a noninvasive diagnostic method that does not require more intensive preparation of the patient. However, since it is an outpatient procedure, the patient must be trained regarding the use of the polygraphy machine.
The process
Cardiorespiratory polygraphy is performed on an outpatient basis and involves the registration, recording, and evaluation of the following parameters:
| Parameters | Sensor (measurement/measuring device) |
| Respiratory flow measurement | Nasal pressure cannula (nasal cannula), thermistor (resistance thermometer) |
| Snoring sounds | Microphone |
| Respiratory movements (abdominal (belly breathing) as well as thoracic (chest breathing) respiratory movements). | Manometer |
| Heart rate | Pulsoymetry (measurement of oxygen saturation of arterial blood and pulse rate) or ECG (electrocardiogram; recording of electrical activity of the heart) |
| Oxygen saturation (SpO2) | Pulse oximetry or oximetry (determination of oxygen saturation of oxygenatable hemoglobin (red blood pigment that binds oxygen and transports it to organs through the bloodstream)) |
| Body position | Accelerometer |
| Mask pressure measurement | Pitot pressure measurement (through hose connection to mask) |
All of the above parameters are derived and recorded simultaneously (at the same time) during a sleep period of at least 6 hours. The patient receives a so-called polygraphy device from a registered sleep physician, which he or she uses independently for one night at home. The evaluation is then carried out by the sleep physician on the basis of the raw data. Since no sleep stages are determined by means of EEG (electroencephalography; registration of brain waves) during this examination, the informative value of cardiorespiratory polygraphy is limited, so it is usually followed by polysomnography.
After the examination
No special measures are required on the patient after polysomnography. Depending on the results of the examination, medication or other therapeutic measures may need to be performed. If there are incorrect measurements, artifacts, or if the results are not conclusive, consider repeating the examination.
Potential complications
Because cardiorespiratory polygraphy is a noninvasive procedure, no complications are expected. However, mismeasurements, e.g., related to application errors by the patient, should be noted.
