Percussion, Auscultation & Pulse Oximetry
Lesson 4 rounds out the hands-on bedside assessment skills: percussion (tapping to evaluate what's under the chest wall), auscultation (listening to lung, voice, and heart sounds), and pulse oximetry (the noninvasive oxygenation measurement you'll use on every patient).
Percussion
Percussion is the act of tapping on a surface to evaluate the underlying structures. It's done by placing a finger firmly against a body part and striking that finger with a fingertip from the other hand.
Chest Percussion
Chest percussion produces both a sound and a palpable vibration useful for evaluating the underlying lung tissue.
Technique
- Place the middle finger of the non-dominant hand firmly against the chest wall, parallel to the ribs, with the palm and other fingers held off the chest
- Use the tip of the middle finger on the right hand (or the lateral aspect of the right thumb) to strike that finger near the base of the terminal phalanx with a quick, sharp blow
- The striking motion is generated at the wrist — not the elbow or shoulder
- Keep the stationary finger firmly against the chest wall; strike and immediately withdraw — the two fingers should be in contact for only an instant
Video reference:
Lung Percussion Sounds
| Sound | Description | Associated With |
|---|---|---|
| Resonant | Normal | Normal air-filled lung |
| Flat | Soft, high-pitched, short duration | Atelectasis |
| Dull | Medium intensity, pitch, and duration | Fluid-filled organs (heart, liver); pleural effusion; pneumonia |
| Hyperresonant | Very loud, lower in pitch, longer in duration | Emphysematous lung; pneumothorax |
| Tympanic | Loud, drum-like, high-pitched | Gastric bubble; air-filled stomach |
Auscultation
Auscultation is the process of listening to body sounds — this lesson covers lung, voice, and heart auscultation. It is the most commonly used physical assessment technique for the respiratory and cardiovascular system.
Lung Auscultation
Setup
- Patient should be sitting upright, breathing a little deeper through an open mouth (if possible)
- Place the diaphragm directly on skin — a hospital gown or thin shirt is acceptable
- Stethoscope tubing should not touch anything — it produces extraneous noises
- Auscultate each position bilaterally using a systematic method
Analyzing Breath Sounds
Work through each finding in order:
- Identify the breath sound
- Identify the intensity (loudness) — mild, moderate, or severe
- Identify when during the respiratory cycle it is heard — inspiratory, expiratory, or both
- Location — bilateral vs unilateral; anterior vs posterior; upper vs lower
- Do the breath sounds change with therapy?
- Do the breath sounds change with coughing?
Normal Breath Sounds
| Sound | Where It's Heard |
|---|---|
| Vesicular | Over most of the lung fields |
| Bronchovesicular | Over the mainstem bronchus |
| Bronchial / Tracheal | Only over the trachea |
Video reference:
Adventitious Breath Sounds
Adventitious = added, irregular sounds produced within a normal sound.
Crackles (Rales)
| Type | Recommended Intervention |
|---|---|
| Coarse rales | Patient needs suctioning |
| Medium rales | Recommend chest physical therapy |
| Fine rales | Recommend IPPB, heart drugs, diuretics, and oxygen |
Video references:
Wheezes
- Unilateral ("localized") wheezing — suggests tumors or foreign body aspiration
- Cardiac asthma — wheezing and dyspnea in patients with heart failure (CHF) in the absence of asthma or COPD; caused by vascular congestion and perivascular edema from fluid overload
Voice Auscultation
Auscultation of voice sounds through a normal air-filled lung produces a muffled, unclear sound — sound vibrations travel poorly through air. Vocal resonance is increased when sound travels through a solid or liquid, so voice auscultation is most helpful for patients with consolidation, pneumonia, atelectasis, pleural effusion, tumor, or abscess.
Egophony
Abnormally enhanced vocal resonance with a high-pitched, nasal quality. Indicates consolidation, pleural effusion, or abscess.
How to assess: auscultate the chest while the patient repeats "E." Egophony exists when this letter is heard as a nasal "A" through the stethoscope.
Video reference:
Bronchophony
Abnormally loud and clear transmission of voice sounds through an area of increased density.
How to assess: the patient repeats the number "99" while you auscultate the thorax.
Whispered Pectoriloquy
Enhanced voice heard through the chest wall — more sensitive than bronchophony.
How to assess: have the patient whisper "one, two, three." Whispered words normally sound faint and indistinct; if they're heard loudly and distinctly, suspect consolidation of lung tissue.
Heart Auscultation
Heart auscultation is the process of listening to the sounds of the heart. Normal heart sounds are caused by the closure of the valves. Have the patient sit upright when auscultating.
Regions
| Region | Location |
|---|---|
| Aortic | Between the 2nd and 3rd intercostal spaces, right sternal border |
| Pulmonic | Between the 2nd and 3rd intercostal spaces, left sternal border |
| Tricuspid | Between the 3rd, 4th, 5th, and 6th intercostal spaces, left sternal border |
| Mitral | Near the apex of the heart, between the 5th and 6th intercostal spaces, mid-clavicular line |
Heart Sounds
S1 — "lub"
- First heart sound
- Occurs at the beginning of ventricular contraction
- Closure of the atrioventricular valves — Mitral and Tricuspid
S2 — "dub"
- Second heart sound
- Occurs when systole ends
- Closure of the Aortic and Pulmonic valves
Video reference:
S3 and S4
Extra sounds generated by unusual blood flow mechanisms. Both are heard at the left 5th intercostal space, mid-clavicular line.
- S3 — results from rapid ventricular filling. May suggest Congestive Heart Failure (CHF).
- S4 — caused most often by a stiff ventricle, such as in hypertension or after a myocardial infarction.
Video references:
Murmurs
Extra sounds heard in conjunction with S1 and S2, caused by blood regurgitating into the chamber it came from.
Causes:
- Valvular dysfunction
- Blood pushed through an abnormal opening — atrial septal defect (ASD) or patent ductus arteriosus (PDA)
Pulse Oximetry
Indications
- Monitor adequacy of arterial oxyhemoglobin saturation
- Quantify the patient's response to therapeutic interventions and diagnostic procedures
- Comply with mandated regulations
Contraindications & Precautions
- No significant contraindications noted — an ABG may be more properly warranted for additional information
- Precautions: false-negatives or false-positives
SpO₂ vs SaO₂
- SpO₂ refers to pulse oximetry
- Not to be confused with SaO₂ — measured with hemoximetry
- Measurement of blood Hgb saturations using spectrophotometry
- Portable, noninvasive device
How Pulse Oximetry Works
- Operates using the Lambert-Beer law — measures light absorbed and transmitted by a substance to identify its presence and determine its concentration
- Uses light to detect tiny volume changes that occur in living tissue during pulsatile blood flow
- Uses two wavelengths of light: one red and one infrared
- Measures transmission through living tissue such as a finger or earlobe
Sensor
- One side emits the red and infrared beams
- The other side measures via a photodetector
- The output signal is transferred to produce the display on the monitor
Signal Components
- Baseline — stable absorbance of the tissue bed
- Peak — pulse component caused by intermittent arterial flow through the tissues
Procedure
Procedure varies depending on site and probe.
- Place the sensor on the selected site
- Observe the waveform (if available)
Documentation
Record the following:
- Date
- Time
- SpO₂ result
- Patient position
- Probe type and site placement
- FiO₂ being provided to the patient