When used in combination, blood gas analysis, spirometry, and pulse oximetry can offer more precise information and effective disease management.

Blood-gas-pulse-ox-335When it comes to accurately diagnosing a respiratory condition, one medical assessment tool may not tell the whole story. Separately, spirometry, pulse oximetry, and blood gas analysis provide some insight into a respiratory illness. Used in combination, however, these tools could offer more precise information and lead to more effective disease management.

The prevalence of asthma and related frequent hospitalizations led Iranian researchers to evaluate the efficacy of combined arterial blood gas and spirometry. Their 2014 study1 involved 55 asthmatic patients who were hospitalized in Tehran from 2005 to 2006. Baseline spirometry and arterial blood gas (ABG) measurements were recorded on the day of admission as well as on the date of discharge.

Arterial blood gas analysis evaluated blood pH, arterial carbon dioxide (Paco2), oxygen (Pao2), oxygen saturation (O2), and bicarbonate (HCO3-) concentration. Vmax20c spirometer measured forced expiratory volume (FEV1), forced vital capacity (FVC), FEV1/FVC, and vital capacity (VC) twice, before and after using a bronchodilator. Mean duration of hospital stay was 8.31 (SD = 4.69) days, ranging between 2 and 23 days.1

The study showed that lower baseline arterial pH, higher baseline HCO3-, lower changes of FEV1 after bronchodilator, and higher patient age (mean patient age was 54.96 [SD = 17.54] years) could lead to longer length of stay among asthma patients. The authors admit that hospitalization of asthma patients is unavoidable, but indicate that closer attention to arterial blood gas and spirometry readings could potentially affect the length of hospital stay.

Consider that some patients with acute severe asthma (ASA) may be unable to perform spirometry due to poor clinical status. In this case, arterial blood gas analysis may be able to determine potential acid base imbalance and help with treatment. Researchers from Buenos Aires, Argentina, conducted a study2 in 2014 with 314 asthma patients who visited the emergency department. Arterial blood gas was drawn, and PaO2, PaCO2, and pH as well as FEV1 were measured on arrival; 48 patients were unable to use spirometry. PaO2, PaCO2, and pH and acid base data were compared between patients who completed spirometry and those who did not (n = 266 vs 48).2

The latter group showed respiratory alkalosis in 56.6 vs 37.8% of cases (p < 0.03), respiratory acidosis in 41.6 vs 51.3% (NS). The authors found some connection between gas exchange, acid base status, and extent of airway obstruction measured by spirometry in ASA patients. Additionally, they determined that patients unable to perform spirometry presented with a more severe acid base imbalance.

Another study3 examined the use of spirometry and blood gas analysis in patients with mitral stenosis (MS) complicated by varying degrees of pulmonary hypertension (PH). The 25 subjects in this cross-sectional study were selected for mitral valve surgery and evaluated for clinical class, echocardiographic severity of mitral stenosis, and pulmonary hypertension; spirometry, pulse oximetry, and blood gas analysis were used to assess pulmonary function.

The results of pulmonary function as determined by spirometry and arterial blood gas analysis can complement other medical evaluation tools insofar as interventions are concerned, according to the study authors. When these tools identify possible structural changes due to PFT changes, early surgery may be advised, even in the absence of a complete symptomatic profile.3

Moreover, the findings indicate that in patients with advanced MS, spirometry and blood gas analysis may be able to offer some insight into postoperative outcomes, including morbidity, the probability of ventilatory problems, and functional capabilities.

Obtaining multiple measures from pulse oximetry, spirometry, and blood gas analysis can present a better picture of oxygenation and ventilation status than either tool alone. When deemed necessary and appropriate, ABG readings may provide supplemental information that improves patient care. RT


Phyllis Hanlon is a contributing writer to RT. For further information, contact [email protected].



  1. Mousavi SA, Fereshtehnejad SM, Khalili N, et al. Arterial blood gas and spirometry parameters affect the length of stay in hospitalized asthmatic patients. Med J Islam Repub Iran. 2014 Feb 16;28:4. eCollection 2014.
  2. Raimondi GA, Gonzalez S, Zaltsman J, Menga G. Spirometry and arterial blood gases in acute severe asthma. WebmedCentral PULMONARY MEDICINE 2014;5(4):WMC004600.
  3. Parvathy UT, Rajan R, Faybushevich AG. Pulmonary function derangements in isolated or predominant mitral stenosis—preoperative evaluation with clinico-hemodynamic correlation. Interv Med Appl Sci. 2014;6(2):75-84. doi. 10.1556/IMAS.6.2014.2.4. Epub 2014 Jun 4.