Respiratory Muscle Strength
MIP and MEP are respiratory muscle strength measures that are helpful for managing obstructive sleep apnea and insomnia.
MIP (Maximum Inspiratory Pressure):
MIP measures the maximum pressure you can generate against a blocked airway during inhalation.
It assesses the strength of the inspiratory muscles, primarily the diaphragm and external intercostal muscles.
Low MIP values may indicate weakened inspiratory muscles, which can contribute to inadequate ventilation during sleep and exacerbate sleep apnea and sleep fragmentation.
MEP (Maximum Expiratory Pressure):
MEP measures the maximum pressure generated during forced exhalation against a blocked airway.
It evaluates the strength of expiratory muscles, such as the abdominal and internal intercostal muscles.
Reduced MEP values may suggest issues with airway clearance, which can increase airway obstruction risk.
Importance in Sleep Apnea Management
Sleep apnea is associated with reduced airway muscle tone, especially during sleep. Respiratory muscle weakness can exacerbate airway collapse and breathing disturbances. While respiratory function tests are not standard for evaluating sleep apnea, they can be crucial in specific contexts:
Tailoring Treatments:
For patients with muscle weakness, these respiratory measures can guide CPAP or BIPAP setting adjustments and targeted respiratory therapies (e.g., inspiratory or expiratory muscle strength training) in complex sleep apnea cases resistant to standard therapies.
Evaluating Treatment Efficacy:
Tracking MIP and MEP following respiratory muscle strength training is a reliable way to confirm its effectiveness..
Mechanisms of Improvement in Insomnia
Reduced Sleep Fragmentation:
Strengthening respiratory muscles can reduce the arousals caused by breathing difficulties, making sleep more continuous,
Increased Parasympathetic Activity:
Stronger respiratory muscles reduce the sensation of breathlessness, which can trigger anxiety or hyperarousal before or during sleep. Controlled breathing exercises as part of respiratory muscle strength training may activate the parasympathetic nervous system, reducing stress and promoting relaxation.
Connection Between Respiratory Muscle Strength and Rhinomanometry
Rhinomanometry measures airflow and resistance in the nasal passages during breathing. Reduced flow may indicate nasal obstruction affecting airflow dynamics. Additionally, low MIP and MEP can contribute to reduced flow on rhinomanometry. Here’s how:
Inspiratory Muscle Weakness (Low MIP):
Weak inspiratory muscles (diaphragm and intercostal muscles) generate insufficient negative pressure to drive air through the nasal passages.
On rhinomanometry, this can appear as reduced inspiratory flow, even if the nasal passages are structurally normal.
Expiratory Muscle Weakness (Low MEP):
Weak expiratory muscles may similarly reduce the ability to generate sufficient positive pressure for exhalation.
On rhinomanometry, this can manifest as reduced expiratory flow or an abnormal flow-volume loop during exhalation.
Dynamic Collapse:
Respiratory muscle weakness can exacerbate airway collapse, particularly in individuals with predisposing conditions like nasal valve instability.
Lower muscle strength may fail to counteract dynamic airway collapse during high-resistance nasal breathing, reducing measurable flow..
Differentiating Muscle Weakness from Nasal Obstruction
While low MIP and MEP can contribute to reduced flow on rhinomanometry, they differ from mechanical nasal obstruction caused by:
Structural factors: Deviated septum, enlarged turbinates, or nasal polyps.
Dynamic factors: Collapsible nasal valves.
If reduced rhinomanometry flow is due to respiratory muscle weakness, treatments targeting inspiratory and expiratory muscle strength (i.e., respiratory muscle strength training) may help improve nasal airflow issues. This holistic approach ensures accurate diagnosis and optimizes treatment.
Normal Values for MIP and MEP by Age and Gender
The normal values for MIP and MEP vary by age, sex, and sometimes body size. Below are typical reference ranges based on published studies and clinical guidelines. MIP reflects inspiratory muscle strength, primarily the diaphragm and intercostal muscles. MEP reflects expiratory muscle strength, mainly abdominal and intercostal muscles. Low values indicate respiratory muscle weakness, which may warrant further investigation (e.g., neuromuscular diseases, chronic lung diseases).
Maximum Inspiratory Pressure
| Age Range (Years) |
Men Lower Limit 1.645 SD (cm H2O) |
Men Mean (cm H2O) |
Women Lower Limit 1.645 SD (cm H2O) |
Women Mean (cm H2O) |
|---|---|---|---|---|
| 18–29 | 94.9 |
136.2 | 65.6 | 103.9 |
| 30-39 | 76.9 | 129.9 | 73.9 | 106.9 |
| 40-49 | 97.0 |
133.3 | 59.6 | 102.4 |
| 50-59 | 84.6 | 130.9 | 71.7 | 101.3 |
| 60-69 | 87.6 | 122.0 | 44.9 | 90.6 |
| 70-80 | 63.1 | 100.6 | 51.3 | 84.4 |
Maximum Expiratory Pressure
| Age Range (Years) |
Men Lower Limit 1.645 SD (cm H2O) |
Men Mean (cm H2O) |
Women Lower Limit 1.645 SD (cm H20) |
Women Mean (cm H2O) |
|---|---|---|---|---|
| 18–29 | 121 |
184.0 | 91.3 | 139.5 |
| 30-39 | 120 | 200.7 | 102 | 152.1 |
| 40-49 | 135 |
202.8 | 96.2 | 142.7 |
| 50-59 | 118 | 205.3 | 105 | 150.3 |
| 60-69 | 138 |
199.2 | 79.5 | 136.3 |
| 70-80 | 97.9 |
170.0 | 76.4 | 127.4 |
Lista-Paz A, Langer D, Barral-Fernández M, Quintela-Del-Río A, Gimeno-Santos E, Arbillaga-Etxarri A, Torres-Castro R, Vilaró Casamitjana J, Varas de la Fuente AB, Serrano Veguillas C, Bravo Cortés P, Martín Cortijo C, García Delgado E, Herrero-Cortina B, Valera JL, Fregonezi GAF, González Montañez C, Martín-Valero R, Francín-Gallego M, Sanesteban Hermida Y, Giménez Moolhuyzen E, Álvarez Rivas J, Ríos-Cortes AT, Souto-Camba S, González-Doniz L. Maximal Respiratory Pressure Reference Equations in Healthy Adults and Cut-off Points for Defining Respiratory Muscle Weakness. Arch Bronconeumol. 2023 Dec;59(12):813-820. English, Spanish. doi: 10.1016/j.arbres.2023.08.016. Epub 2023 Sep 29. PMID: 37839949.
Factors Influencing Values:
Gender: Men tend to have higher values due to greater respiratory muscle mass.
Age: Strength declines with age, reducing MIP and MEP..
Body Size and Fitness Level: Larger individuals and physically active individuals may have higher values.
Underlying Health Conditions: Conditions such as COPD, neuromuscular diseases, or sleep apnea can lead to lower-than-normal values.
Sleep and Brain utilizes the Vitalograph Pneumotrac with RMS for testing respiratory muscle strength and respiratory mechanics. The Pneumotrac with RMS (Respiratory Muscle Strength) enables Spirometry and Respiratory Muscle Strength measurements. Alongside vital capacity (VC), forced vital capacity (FVC), and peak cough flow (PCF), it provides a noninvasive approach to sniff nasal inspiratory pressure (SNIF), maximum inspiratory pressure (MIP), and maximum expiratory pressure (MEP) measurements in adults and children.
We can use the Pneumotrac with RMS to assess diaphragmatic weakness, assess respiratory muscle strength, and monitor the response to respiratory muscle training. The Pneumotrac with RMS is environmentally friendly and does not use disposable sensors, turbines, or flow tubes. The single-use bacterial and viral filter, with validated cross-contamination efficiency >99.999%, protects you, the operator, and the device.
The Spirotrac 6 software is compliant with the American Thoracic Society/European Respiratory Society (ATS/ERS) spirometry guidelines, meeting international guidelines on accuracy and reporting. It offers instant test quality feedback per ATS/ERS Technical Standards, ensuring sustained maximum pressure for 1 second. Pressure and time curves provide real-time input and exceptional test accuracy with a high resolution of 0.1 cm of water. The software provides a percent predicted comparison, repeatability rating, and monitors historical changes in lung function by comparing results and viewing trends over time. For a complete history, we can trend MIP, MEP, SNIP, and VC on one chart.
Frequently Asked Questions
How do we assess Maximum Inspiratory Pressure and Maximum Expiratory Pressure?
The American Thoracic Society outlines the methods for assessing the maximum inspiratory and maximum expiratory pressure.
Maximum Inspiratory Pressure is assessed by having you inhale to the top of vital capacity, then gently biting and wrapping their lips around the respiratory filter's mouthpiece, and then exhaling with maximum effort for ≥ 2 seconds.
Maximum Expiratory Pressure is assessed by having you exhale to the bottom of vital capacity, then gently biting and wrapping their lips around the respiratory filter's mouthpiece, and then inhaling with maximum effort for ≥ 2 seconds.
For both. MEP and MIP, we record the maximum of 3 trials that vary by ≤ 20%.
For both MEP and MIP, no air leakage must occur through the nose. For that reason, we place a nose clip. It is also critical that no air leakage occurs around the respiratory filter's mouthpiece. Therefore, we secure a tight lip seal by applying manual pressure circumferentially around the mouthpiece to ensure no air leakage.
What are the verbal instructions for Maximum Inspiratory Pressure and Maximum Expiratory Pressure?
There are no standardized verbal instructions for MEP or MIP proposed by the American Thoracic Society. Therefore, the verbal instructions below are examples that we use for MIP and MEP:
Maximum Expiratory Pressure: "Breathe in as much air as possible until you can't breathe in anymore, then gently bite on this mouthpiece and seal your lips tightly around the mouthpiece to make sure no air leaks out of the side, then blow out as hard as possible until I tell you to stop."
Maximum Inspiratory Pressure: Blow out as much air as possible until you can't breathe out anymore, then gently bite on this mouthpiece and seal your lips tightly around the mouthpiece to make sure no air leaks out of the side, then suck in as hard as possible until I tell you to stop."ss
Why does Maximum Expiratory Pressure matter?
Unlike values such as ml or mm hg, which indicate the flow or volume of air, typically reflected by spirometry tests, MEP measures your actual expiratory strength.
This is because the measurement of MEP utilizes a manometer or a pressure threshold trainer, which generally has a one-way valve or an occluded airway through which you need to blow quickly and intensively, as opposed to the spirometer, which requires the individual to blow and sustain the maximum duration in that one single breath.
MEP value is more critical if you have compromised speech, swallowing, and breathing functions because it provides a better outlook on expiratory muscle strength. Once your MEP value is measured, you can start with expiratory muscle strength training according to your personal MEP level.
How can you measure your Maximum Expiratory Pressure without an accurate and precise measurement device?
You can estimate the MEP by using a pressure threshold trainer, such as the EMST 150
Step 1: Take the EMST 150 in your hand, and place it on the lowest setting by rotating the knob.
Step 2:
Insert the mouthpiece on the end of the device.
Take a deep breath.
Blow through the device intensively.
Step 3: While blowing, if you feel the air push through, that means you have crossed the specific threshold level.
Step 4: Start increasing the threshold level by rotating the knob counter-clockwise and blowing again. Keep doing this until you reach a level without air coming out from the device.
Step 5: Once you find that level, turn the knob back one turn and blow through the device. This is your personal MEP setting.
