Reviews Before becoming PGY- pulmonary function test

Pulmonary function test

Reference:  "Overview of pulmonary function testing in adults"(2016) Meredith C McCormack, MD, MHS, retrieved from UpToDate

 

Q:  PFT主要的內容？

A:  spirometry(before and 10 to 15 minutes after a bronchodilator, Albuterol 90 to 100 mcg  #4 IH?), lung volume examination

      DLCO, maximal respiratory pressures, flow-volume loops,

      submaximal exercise testing, and bronchoprovocation challenge

 

Q: PFT注意事項？

A: 若平常都用inhalor BID，則PFT四小時前開始不可用SABA、十二小時前開始不可用LABA、二十四小時前開始不可用LAMA。

Q: Spirometry 是測什麼？
A: (白話)測量深吸氣後大力、完整吐氣時，每個時間點的呼氣量。

↑ from wikipedia



Q: FVC減少、呼吸道阻塞時怎麼測？

A: 可以改測SVC(Slow exhalation)，但是如果是restrictive  lung則兩者的結果一樣爛。

 

Q: Spirometry的判讀流程？
A: 先看 FEV1/FVC, 再看DLCO。結果大致分三大種：較確定obstructive type的COPD、變異性較大的asthma、restrictive type的ILD/neuromuscular problem。 



↑from UpToDate



Q: Flow-volume loop的鑑別診斷用途？
A: 當聽到stridor的時候使用，能幫助辨別airway obstruction的部位。

from UpToDate

Q: Maximal respiratory pressures是什麼？
A: 經過有阻力的吹口大力吸氣 / 噘嘴吐力的最大壓力值。
 

* PFT tutorial website: https://depts.washington.edu/uwmedres/Library/eLearning/Pulmonary/

 Here are some notes from the website listed above:
 
- For obstructive pattern, the severity depends on...

	FEV1 > 80% predicted: mild obstruction
	50% < FEV1 < 80% predicted: moderate obstruction
	30% < FEV1 < 50% predicted: severe obstruction
	FEV1 < 30% predicted: very severe obstruction - For decrease DLCO, the severity depends on...      65% predicted < DLCO <80% predicted: Mild      50% < DLCO < 65% predicted: Moderate      DLCO < 50% predicted: Severe

- For reduced DLCO, the meaning is...

1. obstructive--> emphysematous, reduced surface area for gas exchange.
2. normal spirometry and lung volumes-->anemia, pulmonary hypertension, heart problem
3. restrictive -->idiopathic pulmonary fibrosis
4. Not equalled to hypoxemia!

Mind: diffuse alveolar hemorrhage的病人DLCO可能不降反升！
 
- For restrictive pattern, the severity depends on...

     65% < TLC < 80% predicted: mild restriction
     50% < TLC < 65% predicted: moderate restriction
     TLC < 50% predicted: severe restriction
 
- Characteristics of  idiopathic pulmonary fibrosis
    septal thickening
    traction bronchiectasis
    more prominent in the periphery of the lungs (sub-pleural regions)

 

- For mixed obstructive+ restrictive pattern, the severity depends on...
   
     FEV₁ > 80% predicted: mild
     50% < FEV₁ < 80% predicted: moderate
     30% < FEV₁ < 50% predicted: severe
     FEV₁ < 30% predicted: very severe