Respiratory examination: basic methods and what to choose

Respiratory examination begins with a clinical objective: quickly identify a life-threatening condition, clarify the underlying disease, and select a safe management strategy. Modern diagnostics rely on a combination of physical examination, bedside methods, functional tests, ultrasound, and, when necessary, invasive interventions. The key principle is the consistent increase in information content while managing risks and costs. [1]

From a technical perspective, standards for performing and interpreting functional tests have been updated in recent years: spirometry, lung volume measurements, diffusing capacity, and airway inflammation indicators. These are important reference documents to consider when planning examinations and interpreting results. [2]

Another systemic change is the active implementation of lung ultrasound at the patient's bedside. Lung ultrasound has proven highly valuable for the diagnosis of dyspnea, pneumonia, pleural effusion, pneumothorax, and pulmonary edema, and often reduces the time to verify the cause of respiratory failure. [3]

Finally, the widespread use of pulse oximetry has necessitated consideration of the method's limitations, particularly the impact of skin pigmentation and environmental factors on accuracy. This directly impacts the interpretation of oxygen saturation and decisions about oxygen therapy. [4]

Patient preparation and baseline indicators

The first step is to assess vital signs: respiratory rate, heart rate, oxygen saturation, temperature, blood pressure, and level of consciousness. These data determine the priorities and safe pace of further investigations, including early initiation of oxygen therapy if indicated and assessment of the need for gas analysis. [5]

Pulse oximetry is a rapid screening tool for hypoxemia, but results can be distorted by poor perfusion, low skin temperature, nail polish, smoking, bright lighting, certain heart rhythm disorders, and dark skin pigmentation. In 2024, the regulator published analytical materials, and in 2025, draft updated recommendations to improve the accuracy of these devices in different patient groups. If clinical findings and results do not match, saturation should be confirmed by blood gas analysis. [6]

Target oxygen saturation ranges in adults in acute settings are typically 94-98%, and in patients at risk for hypercapnia, 88-92% unless otherwise indicated. These are working guidelines for oxygen administration in the emergency department until a diagnosis is confirmed. [7]

Before functional testing, rest, withdrawal of bronchodilators for a specified period, correct inhalation and exhalation technique, mouthpiece tightness, and adherence to quality criteria are essential. Failure to comply with these conditions is the main cause of false obstruction and "skewed" flow and volume curves. [8]

Table 1. Observed signs and probable causes at the start

Sign	The most likely reasons first
Respiratory rate greater than 24 per minute	Pneumonia, pulmonary edema, pulmonary embolism, exacerbation of chronic obstructive pulmonary disease
Oxygen saturation less than 90% by pulse oximeter	Hypoxemia of any nature, decompensation of chronic respiratory failure
Central cyanosis	Severe hypoxemia, methemoglobinemia
Use of accessory muscles	Acute respiratory failure, asthmatic status
Unilateral chest wall protrusion	Pneumothorax with valve mechanism, massive effusion

Physical examination: what is really informative

The classic four—inspection, palpation, percussion, and auscultation—remain the foundation. Inspection reveals the rate and type of respiration, the involvement of accessory muscles, and chest wall deformities. Palpation helps assess vocal fremitus and excursion. These data alone do not establish a diagnosis, but they guide the selection of instrumental methods. [9]

Percussion is particularly useful for recognizing pleural effusion: dullness on percussion has a high specificity and a positive likelihood ratio, as confirmed by meta-analyses. Hyperacousticity more often indicates increased lung airiness or pneumothorax. [10]

Auscultation reveals changes in breath sounds and additional sounds. Dry wheezing is most often associated with bronchial obstruction, moist crackling rales with alveolar pathology, and pleural friction rubs with pleurisy. Interpretation is more valuable when compared with clinical and imaging data. [11]

The reliability of individual tests varies: for example, unilateral wheezing increases the likelihood of pneumonia, but physical examination as a whole cannot reliably rule it out without radiographic or ultrasound confirmation. Sound spectrogram technologies can improve interobserver agreement. [12]

Table 2. Auscultatory phenomena and their interpretation

Phenomenon	What does it mean first of all?
Dry wheezing	Bronchial obstruction in asthma or chronic obstructive pulmonary disease
Moist, fine-bubble rales	Alveolar filling in pneumonia or pulmonary edema
Bronchial breathing	Consolidation of lung tissue above the lesion
Egophony and increased bronchophony	Tissue compaction, possible effusion
Pleural friction rub	Dry pleurisy or adjacent consolidation

Rapid, non-invasive bedside methods

Pulse oximetry allows for screening for hypoxemia and monitoring the effects of oxygen, but if the clinical picture is inconsistent, it requires confirmation by arterial blood gas analysis. In recent years, regulators and professional societies have emphasized systematic errors in people with dark skin pigmentation. [13]

Peak expiratory flow rate (PEF) measurements using a peak flow meter help track variability in bronchial patency over time. In adults and adolescents, a variability of approximately 20% when keeping a diary is considered diagnostically significant, but spirometry remains the preferred reversibility test. [14]

The six-minute walk test assesses functional capacity and is used for baseline prognosis, rehabilitation selection, and therapy monitoring. The standard describes the indications, route, safety, and interpretation of distance and desaturation during exercise. [15]

In the emergency department (ED) setting, lung ultrasound provides rapid clues to the presence of interstitial syndrome, effusion, pneumothorax, or consolidation and often shortens the path to the correct management.[16]

Table 3. Peak expiratory flow rate and variability

Indicator	Diagnostic landmark
Increase in peak expiratory flow rate after bronchodilator	About 20% is considered significant with proper effort
Diurnal variability by diary	Around 20% or more over several days
Preferred reversibility test	Spirometry with an increase in forced expiratory volume in 1 second and forced vital capacity according to standards

Table 4. Six-minute walk test: key parameters

Component	What to evaluate
Total distance	Comparison with the original value and reference
Minimum oxygen saturation	Oxygen decision during exercise
Dyspnea according to the Borg scale	Symptomatic dynamics
Safety	Contraindications and test termination criteria

Spirometry: technique, quality control and reading of results

Spirometry is a basic test of ventilatory function. The current standard specifies requirements for equipment, calibration, patient preparation, and acceptance and reproducibility criteria, including flow-volume waveform analysis, expiratory completion monitoring, and artifact identification. [17]

Interpretation is based on Z-scores, taking into account ethnic and age-specific references, rather than fixed thresholds alone. The assessment includes forced expiratory volume in 1 second, forced vital capacity, their ratio, and severity category based on the degree of deviation. Interpretation strategies were updated in 2022. [18]

Positive reversibility after inhalation of a short-acting bronchodilator supports the diagnosis of asthma, and the absence of a significant response does not exclude obstructive disease in the presence of symptoms and risk factors. Linked measurement before and after the test using a standardized protocol is recommended. [19]

If spirometry is borderline or unstable, the next step is to measure lung volumes and diffusion capacity, and, for inflammatory phenotyping, the fraction of nitric oxide in exhaled air. [20]

Table 5. Typical ventilation patterns according to spirometry

Pattern	Key Features	What to look for next
Obstructive	A decrease in the ratio of forced expiratory volume in 1 second to forced vital capacity below the lower limit of normal, a concave flow curve	Reversibility, variability, lung volumes, inflammatory markers
Restrictive suspect	Decreased forced vital capacity with normal ratio	Confirm total lung capacity using body plethysmography
Mixed	Decrease in both the ratio and forced vital capacity of the lungs	Full set of lung volumes and diffusion capacity

Lung volumes and resistance: why body plethysmography?

Measuring total lung capacity, residual volume, and other corpuscular volume parameters allows for confirmation of restriction, assessment of hyperinflation and air trapping, and calculation of airway resistance. An updated joint standard for measuring lung volumes was published in 2023. [21]

Key takeaway: Reduced total lung capacity confirms a restrictive disorder, while increased residual volume and residual volume/total lung capacity ratio indicate hyperinflation and small airways. Standardized coherent maneuvers and enhanced quality control are recommended.[22]

Body plethysmography also provides airway resistance and conductance, which is helpful in complex obstruction and in assessing response to therapy, although interpretation requires context and comparison with spirometry.[23]

In clinical situations with discordance between spirometry and symptoms, volume measurement is a rational next step before more advanced invasive procedures. [24]

Table 6. Lung volumes and their diagnostic value

Indicator	Change	Possible interpretation
Total lung capacity	Below the lower limit of normal	Parenchymal or extrapulmonary restriction
Residual volume	Above the upper limit of normal	Hyperinflation, air traps
Ratio of residual volume to total lung capacity	Increased	Small airways, severe obstruction
Specific resistance of the respiratory tract	Increased	Obstruction, need for clarification of the phenotype

Diffusing capacity of the lungs: when it is reduced and when it is not

Carbon monoxide diffusion capacity evaluates gas transfer across the alveolar-capillary membrane. The 2017 standard standardized the single-inhalation technique, breath-holding requirements, and hemoglobin adjustments. This is critical for the comparability of results. [25]

A decrease in the index with preserved ventilation may indicate interstitial lesion, pulmonary vascular pathology, or emphysema. Conversely, a normal index with restriction supports an extrapulmonary cause of the limitations. Interpretation always takes into account hemoglobin and smoking. [26]

In obstructive disease, the combination of reduced diffusion capacity and hyperinflation indicates severe emphysema, and dissociation with gas exchange and desaturation during exercise increases the suspicion of a vascular component. [27]

The variability of the result requires repeat measurements when clinical status changes and before making long-term decisions, such as before starting home oxygen.[28]

Table 7. Diffusing capacity of the lungs: a simple interpretation scheme

Diffusion capacity	Spirometry	Volumes	Most likely
Reduced	Normal or mild restriction	Norm	Pulmonary vascular pathology, early interstitial disease
Reduced	Obstruction	Increased residual volume	Emphysema
Norm	Restriction	Decreased total lung capacity	Extrapulmonary restriction

Airway inflammation markers: fractional nitric oxide

Fractional nitric oxide in exhaled air is a noninvasive marker of eosinophilic inflammation. The 2021 guidelines define levels at which this indicator supports diagnosis and guides therapy in adults and children. It should be used in conjunction with clinical and functional assessment. [29]

High values support the likelihood of response to inhaled corticosteroids, low values reduce it, and intermediate values require dynamic monitoring and correlation with symptoms and exacerbations. This measurement is convenient for monitoring adherence and steroid load. [30]

Smoking, acute infections, and the use of certain medications can affect the reading. It is important to standardize measurement times and patient instructions. [31]

Table 8. Fractional nitric oxide: interpretation guidelines in adults

Level	Clinical interpretation
Short	Low probability of eosinophilic inflammation, low expected benefit from inhaled corticosteroids
Intermediate	Context and dynamics are needed
High	High probability of eosinophilic inflammation and response to inhaled corticosteroids

Lung Ultrasound: Quick Answers for Shortness of Breath

Standardized bedside lung ultrasound protocols have been described and validated for the assessment of acute dyspnea. A rapid protocol, combining multiple artifacts and features, allows for the differentiation of underlying causes of respiratory failure with high accuracy. [32]

Key features: absence of pleural sliding in pneumothorax, multiple vertical artifacts in interstitial syndrome, subpleural consolidation in pneumonia, and free fluid in effusion. Combined with venous ultrasound, this speeds diagnosis. [33]

Current consensus emphasizes the role of ultrasound as a first step in patients with respiratory symptoms, particularly when transport to the x-ray room is difficult or delays care.[34]

Table 9. Ultrasound profiles and probable states

Sign on ultrasound	Probable cause
Absence of pleural sliding and "pleural line without movement"	Pneumothorax
Multiple vertical artifacts across the anterior fields	Interstitial syndrome, cardiogenic edema
Subpleural consolidation, bronchogram	Pneumonia
Anechoic streak above the diaphragm	Pleural effusion

Bronchoscopy: When is invasive verification necessary?

Fiberoptic bronchoscopy remains the standard for visualization of the tracheobronchial tree, sampling, and therapeutic procedures. British and international guidelines systematize the indications, preparation, safety, and instrumental procedures, including bronchoalveolar lavage and biopsies. [35]

The procedure is relatively safe if the protocol is followed, but patients with severe chronic obstructive pulmonary disease and pulmonary hypertension have an increased risk of desaturation. Optimization of pre-procedural treatment and caution with sedatives are important. [36]

During the pandemic, the role of selective bronchoscopy in a limited number of patients has been emphasized to exclude superinfection and resolve technical issues in intubated patients. Indications are always weighed against the risk of aerosol formation. [37]

Table 10. Bronchoscopy: indications and contraindications

Indications	Relative contraindications
Unclear hemoptoesis, suspected tumor, infection analysis, foreign body removal, stenting	Severe hypoxemia without adequate oxygenation, unstable hemodynamics, uncorrected coagulopathy

How to Put It All Together: A Practical Algorithm

Begin with baseline measurements and a physical examination. If hypoxemia is present, oxygen should be administered according to target values and gas exchange status should be clarified. A discrepancy between clinical findings and pulse oximetry is a reason to perform a blood gas analysis. [38]

Next come rapid methods: lung ultrasound for dyspnea, peak expiratory flow rate to monitor variability, and a six-minute walk test to assess functional status. These steps help prioritize and determine the need for hospitalization or rehabilitation. [39]

If phenotyping and formalization of the diagnosis are required, perform spirometry according to the standard, then, as indicated, lung volumes and diffusing capacity, and, in the case of an asthmatic phenotype, nitric oxide fraction. This is the core of the modern interpretive strategy. [40]

Finally, bronchoscopy is indicated for morphological verification and therapeutic decision-making when noninvasive methods have been exhausted or when intervention is required. The decision to perform bronchoscopy is made after respiratory stabilization and risk assessment. [41]