Pulmonary Function Tests Overview

A method to analyze lung airflow and volumes, used to diagnose shortness of breath (dyspnea) causes, specifically obstructive or restrictive lung diseases.

A lung condition where air has trouble leaving the lungs.

A lung condition where air has trouble entering the lungs.

Shortness of breath.

A cause of shortness of breath due to lack of physical fitness or weight.

Tiny air sacs in the lungs.

Air passages in the lungs that lead to alveoli.

Used to monitor disease severity and progression in addition to identifying the cause of breathlessness.

The volume of air forcefully exhaled in the first second of a forced expiration.

The total amount of air that can be forcefully exhaled after a maximum inspiration.

The ratio of the volume of air exhaled in the first second (FEV1) to the total forced vital capacity (FVC).

A normal FEV1/FVC ratio is typically greater than 80%.

The FEV1/FVC ratio is reduced in patients with obstructive lung disease.

The FEV1/FVC ratio may be normal or even slightly increased in restrictive lung disease.

The amount of air inhaled and exhaled during normal, quiet breathing.

The additional volume of air that can be inhaled beyond the normal tidal volume.

The additional volume of air that can be exhaled beyond the normal tidal volume.

The amount of air that remains in the lungs after a maximal exhalation.

The maximum volume of air that can be exhaled after a maximal inhalation.

The volume of air remaining in the lungs after a normal, quiet exhalation.

A simple, non-invasive test that measures lung function by assessing air flow and volume

A normal FEV1/FVC ratio is approximately 0.8, meaning that about 80% of the total lung capacity is exhaled in the first second.

A spirometry test that meets specific criteria for accurate interpretation. These criteria include a sharp peak and flow curve, and a duration of more than six seconds.

A normal spirogram has a sharp peak and flow curve, the expiratory phase lasts longer than six seconds, with a plateau indicating the total FVC.

The spirogram curve in a restrictive disease looks similar to a normal one but with lower overall volumes due to reduced lung capacity.

The spirogram curve in an obstructive disease shows a significantly slower slope than normal, indicating difficulty with airflow.

FEV1 is lower in restrictive disease compared to normal, because the lungs can't hold as much air to push out.

FEV1 is much lower in obstructive lung disease compared to normal, due to the difficulty in exhaling air.

FVC is lower in restrictive lung disease, as the lungs can't fill with as much air.

FVC is also lower in obstructive lung disease, as it is difficult to empty the lungs completely.

A graph showing the relationship between air flow rate (Y-axis) and lung volume (X-axis) during breathing, used to diagnose lung diseases.

The curve has a lower peak expiratory flow and a gradual decline in volume, indicating difficulty exhaling.

The curve has a similar shape to a normal one, but smaller overall, showing limited lung volume.

The amount of energy the body uses to move air in and out of the lungs.

The resistance encountered by air moving through the airways.

Rapid airflow creating a chaotic pattern, increasing resistance.

Smooth, streamlined airflow with low resistance.

Increased breathing rate leads to increased airflow resistance and higher work of breathing.

The resistance encountered when expanding and contracting the lungs.

The more deflated the lungs are, the more work is needed to inflate them.

Rapid breathing reduces the amount of work needed to expand the lungs.

Less work is required to expand the lungs during rapid breathing because they don't get as deflated.

As you breathe faster, there is less elastic resistance to overcome. Conversely, breathing slower results in more elastic resistance.

Airflow resistance increases as you breathe faster, thus requiring greater work of breathing. The faster the air moves, the more friction it encounters.

The optimal breathing rate is around 15-20 breaths per minute. This minimizes the work of breathing by balancing elastic and airflow resistance.

Restrictive lung disease increases the work of breathing at all respiratory rates. This is due to the difficulty in expanding the lungs.

Restrictive patients prefer fast and shallow breathing to minimize work of breathing. This reduces elastic resistance.

Obstructive lung disease also increases the work of breathing at all respiratory rates, but the primary issue is airway resistance.

Obstructive patients prefer slow and deep breathing to minimize work of breathing. This reduces airflow resistance.

Respiratory rate is primarily determined by carbon dioxide levels and oxygen levels in the blood, not just work of breathing.

Restrictive lung disease leads to fast and shallow breathing, while obstructive lung disease leads to slow and deep breathing.

Patients with restrictive lung disease prefer fast breathing to reduce elastic resistance. Patients with obstructive lung disease prefer slow breathing to minimize airway resistance.